Aluminum alloy composite for brazing and heat exchanger including the same

Abstract

An Al—Si based brazing material is formed on one surface of a core material, and a cladding material is formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness thereof. The core material contains 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, and 0.02 to 0.3 mass % of Ti in such a manner that a total content of Cu and Si is in the range of 2.0 mass % or less. The cladding material contains 2 to 9 mass % of Zn, 0.3 to 1.8 mass % of Mn and/or 0.04 to 1.2 mass % of Si, and further contains 0.02 to 0.25 mass % of Fe, 0.01 to 0.30 mass % of Cr, 0.005 to 0.15 mass % of Mg, and/or 0.001 to 0.15 mass % of Cu.

Description

TECHNICAL FIELD

The present invention relates to an aluminum alloy composite material suitable for brazing sheet that is used in a tube, a header plate, and a heater core of a radiator in an automobile and the like, and also relates to a heat exchanger. More particularly, the present invention relates to an aluminum alloy composite material for brazing that has high strength, has high corrosion resistance on an inner-surface side (coolant side) when being used as a radiator, a heater core, and a radiator tube, and can be made thin, and also relates to a heat exchanger using that aluminum alloy composite material.

BACKGROUND ART

In an aluminum alloy composite material for brazing in which a core material is cladded with a brazing material on one surface and a cladding material on the other surface, the strength of the core material is improved by adding Mg to the core material. However, when the Mg content in the core material exceeds 0.2 % by mass (0.2 mass %), the brazeability is extremely lowered. Therefore, addition of Mg to the core material is not preferable.

An aluminum alloy composite material is proposed which can be made thin without hindering the corrosion resistance, the brazeability, and the like (see Japanese Patent Laid-Open Publication Nos. Hei 8-283891 and Hei 11-61306). Especially, in the aluminum alloy composite material described in Japanese Patent Laid-Open Publication No. Hei 8-283891, the cladding material contains Mg of 0.3 to 3 mass % and Zn of 2.2 to 5 mass %. This aluminum alloy composite material improves the strength of the cladding material by the addition of Mg.

Moreover, an aluminum alloy composite material is proposed in which the strength of the cladding material is improved by adding Mn and Si to the cladding material, instead of Mg (see Japanese Patent Laid-Open Publication No. Hei 11-61306).

However, the conventional techniques described above have the following disadvantages. First, the aluminum alloy composite material described in Japanese Patent Laid-Open Publication No. Hei 8-283891 aims to improve the strength by adding Mg to the cladding material. However, when the aluminum alloy composite material is made thinner, Mg is diffused by heat during brazing and reaches a surface of the brazing material through the core material, thus deteriorating the brazeability. Therefore, it is necessary to form the core material to be thick in order to ensure a desired brazeability. That is, making the aluminum composite material thin is limited. Moreover, in this conventional aluminum alloy composite material, the brazeability on the cladding material side is inferior to that of the brazing material. Therefore, this conventional aluminum alloy composite material cannot be used as a tube material that is brazed on the cladding material side.

On the other hand, the aluminum alloy described in Japanese Patent Laid-Open Publication No. Hei 11-61306 aims to improve the strength by adding Mn and Si to the cladding material. However, making the aluminum alloy composite material thinner without deteriorating the corrosion resistance and the like only by adding Mn and Si to the cladding material has a limitation. More specifically, in case of adding Si to the cladding material, precipitation of Al—Mn—Si precipitates at grain boundaries occurs during brazing. Thus, the corrosion resistance of the cladding material is deteriorated and a time period during which the cladding material serves as a sacrifice anode layer is shortened. This results in deterioration of the corrosion resistance of the cladding material on the inner-surface side (coolant side). Moreover, the core material usually contains Cu that is diffused into the cladding material during the brazing. Thus, precipitation of Al—Cu—Si precipitates or Al—Mn—Cu—Si precipitates occurs at the grain boundaries in the cladding material so as to deteriorate the corrosion resistance of the cladding material. This also causes deterioration of the corrosion resistance of the cladding material on the inner-surface side.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an aluminum alloy composite material for brazing that has high strength, has good corrosion resistance on its inner-surface side (coolant side) when being used as a tube, a header plate, and a heater core of a radiator, and can be made thin, and to provide a heat exchanger using that aluminum alloy composite material.

According to a first aspect of the present invention, an aluminum alloy composite material for brazing comprises: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material. The core material contains 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, and 0.02 to 0.3 mass % of Ti in such a manner that a total content of Cu and Si is in the range of 2.0 mass % or less and a remainder of a composition of the core material is Al and unavoidable impurities. The cladding material contains 2 to 9 mass % of Zn, at least one selected from the group consisting of 0.3 to 1.8 mass % of Mn and 0.04 to 1.2 mass % of Si, and at least one selected from the group consisting of 0.02 to 0.25 mass % of Fe, 0.01 to 0.30 mass % of Cr, 0.005 to 0.15 mass % of Mg, and 0.001 to 0.15 mass % of Cu.

In this aluminum alloy composite material for brazing, it is preferable that the cladding material contain 3 mass % or more of Zn and a Zn/Si ratio be 4 or more.

According to a second aspect of the present invention, an aluminum alloy composite material for brazing comprises: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material. The core material contains 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, and 0.02 to 0.3 mass % of Ti in such a manner that a total content of Cu and Si is in the range of 2.0 mass % or less and a remainder of a composition of the core material is Al and unavoidable impurities. The cladding material contains 2 to 9 mass % of Zn, 0.3 to 1.8 mass % of Mn, 0.5 to 1.2 mass % of Si, and at least one selected from the group consisting of 0.02 to 0.25 mass % of Fe, 0.01 to 0.30 mass % of Cr, 0.005 to 0.15 mass % of Mg, and 0.001 to 0.15 mass % of Cu. An average Si composition in the cladding material is equal to or less than 0.5 times Si content.

In this aluminum alloy composite material for brazing, it is preferable that the cladding material contains 3 mass % or more of Zn and a Zn/Si ratio be 4 or more.

A heat exchanger according to the present invention is assembled by performing brazing that uses the aluminum alloy composite material for brazing according to the second aspect of the present invention as a brazing sheet, wherein the brazing is performed at a cooling rate of 100° C./minute or more.

According to a third aspect of the present invention, an aluminum alloy composite material for brazing comprises: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material. The core material contains 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu. 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, 0.02 to 0.3 mass % of Ti, and a remainder of Al and unavoidable impurities. The cladding material contains 2 to 9 mass % of Zn, and at least one selected from the group consisting of 0.3 to 1.8 mass % of Mn and 0.04 to 1.2 mass % of Si. The cladding material further contains precipitates or crystallized particles-having an average grain size smaller than 0.1 μm with a density of 5.0×10⁸ particles/mm³ or more.

According to the first through third aspects of the present invention, an aluminum alloy composite material for brazing can be achieved that has high strength and high corrosion resistance and that can be formed to be thin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an aluminum alloy composite material for brazing according to an embodiment of the present invention;

FIG. 2 is a perspective view showing a part of a tube of a radiator; and

FIG. 3 is a cross-sectional view showing a laminated structure in the aluminum alloy composite material that forms the tube.

BEST MODE FOR CARRYING OUT THE INVENTION

The inventors of the present invention made various experiments and researches in order to overcome the aforementioned problems. As a result, the inventors found that an aluminum alloy composite material could be made thinner largely while ensuring the brazeability, the corrosion resistance, and the strength, by making a cladding material contain Mn and Si in predetermined content ranges, setting the ratio of the thickness of the cladding material to that of the aluminum alloy composite material to achieve a predetermined range, making the cladding material contain at least one of Fe, Cr, Mg, and Cu, and limiting distribution of precipitates or crystallized particles in the cladding material.

Moreover, the corrosion resistance can be improved by setting “an average Si composition of the cladding material” to be equal to or less than “Si content”×0.5. Furthermore, the corrosion resistance on the inner-surface side (coolant side) of the aluminum alloy composite material can be improved by setting a cooling rate during brazing to be 100° C./minute or low.

A core material, a cladding material, and a brazing material of an aluminum alloy composite material for brazing according to the first aspect of the present invention are now described with respect to a reason why a component is added and a reason for limiting the composition. First, the composition of the core material is described.

Core Material]

Mg (Magnesium): 0.2 Mass % or Less

Mg is an element that improves the strength of the core material. However, Mg lowers the brazeability when Mg content exceeds 0.2 mass %. Especially, in case of a Nocolok brazing method, the brazeability is largely lowered. Therefore, Mg content is limited to 0.2 mass % or less. In order to further suppress the deterioration of the brazeability, it is preferable that Mg content be 0.1 mass % or less.

Cu (Copper): 0.2 to 1.0 Mass %

Cu is an element that improves the strength of the core material and also improves the corrosion resistance of the core material on the brazing-material side. However, Cu added to the core material increases susceptibility to intergranular corrosion and therefore lowers the corrosion resistance of the core material on its cladding material side. Thus, 2 mass % or more of Zn is added to the cladding material. This addition of Zn can set a potential of the cladding material to be base with respect to a potential of the grain boundaries and can prevent intergranular corrosion. That is, it is possible to set the potential of the cladding material to be low with respect to the potential of the core material, especially potentials of a matrix and the grain boundaries of the core material by increasing Zn content in the cladding material. Therefore, intergranular corrosion can be prevented. When Cu content is less than 0.2 mass %, the strength of the core material cannot be improved sufficiently. On the other hand, when Cu content exceeds 1.0 mass %, a melting point of the core material is lowered and melting of the core material occurs during brazing. Therefore, Cu content is set in the range of 0.2 to 1.0 mass %.

Si (Silicon): 0.05 to 1.3 Mass %

Si is an element that improves the strength of the core material. Especially, Mn—Si precipitates improves the strength of the core material. However, when Si content is less than 0.05 mass %, the strength of the core material cannot be improved sufficiently. On the other hand, when Si content exceeds 1.3 mass %, the melting point of the core material is lowered, and melting of the core material occurs during brazing because of increase of a low-melting phase. Therefore, Si content is set in the range of 0.05 to 1.3 mass %.

Total Content of Cu and Si: 2.0 Mass % or Less

As described above, Cu and Si lower the melting point of the core material and cause melting of the core material during brazing, when the added amount exceeds a predetermined amount. In order to prevent the melting of the core material, it is necessary to limit the total content of Si and Cu to be 2.0 mass % or less. Therefore, the total content of Si and Cu is set to 2.0 mass % or less.

Mn (Manganese): 0.3 to 1.8 Mass %

Mn is an element that improves the corrosion resistance, the brazeability, and the strength of the core material. When Mn content is less than 0.3 mass %, the strength cannot be improved. However, when Mn content exceeds 1.8 mass %, large compounds are generated, thus lowering the workability. Therefore, Mn content is set in the range of 0.3 to 1.8 mass %.

Ti (Titanium): 0.02 to 0.3 Mass %

Ti is an element that improves the corrosion resistance of the core material extremely. When Ti content is less than 0.02 mass %, Ti cannot improve the corrosion resistance of the core material sufficiently. On the other hand, even when Ti content exceeds 0.3 mass %, Ti cannot further improve the corrosion resistance of the core material but generates large compounds. Thus, the workability of the aluminum composite material is lowered. Therefore, Ti content is set in the range of 0.02 to 0.3 mass %. As described above, Ti is an element that is indispensable for improvement of the corrosion resistance of the core material. When Ti is added to the core material, precipitation in layers occurs in the core material so as to suppress progress of pitting corrosion in a depth direction. Moreover, addition of Ti changes the potential of the core material to be noble. In addition, Ti is small in a diffusion rate in an aluminum alloy and does not move largely during brazing. Therefore, addition of Ti is effective to maintain a potential difference between the core material and the brazing material or between the core material and the cladding material so as to electrochemically prevent corrosion of the core material.

Cr (Chromium): 0.3 Mass % or Less

Cr is an element that improves the corrosion resistance, the strength, and the brazeability of the core material. When Cr content exceeds 0.3 mass %, the corrosion resistance, the strength, and the brazeability of the core material cannot be further improved. Instead, the workability is deteriorated because of large compounds. Therefore, Cr content is set in the range of 0.3 mass % or less. It is preferable that Cr content be in the range of 0.02 to 0.3 mass %.

Fe (Iron): 0.2 Mass % or Less

Fe is an element that makes crystal grains in the core material finer and improves the strength and the weldability of the core material. When Fe content exceeds 0.2 mass %, the corrosion resistance of the core material is deteriorated. Therefore, Fe content is set in the range of 0.2 mass % or less. It is more preferable that Fe content be in the range of 0.02 to 0.2 mass %.

[Cladding Material]

The composition of the cladding material is now described.

Mn (Manganese): 0.3 to 1.8 Mass %

Mn is an element that improves the strength of the cladding material. In other words, Mn in the form of solid solution in the cladding material improves the strength of the material. When Mn content is less than 0.3 mass %, the sufficient amount of Mn solid solution cannot be obtained. Therefore, the strength cannot be ensured. On the other hand, when Mn content is more than 1.8 mass %, compounds increase. Those compounds deteriorate the workability of the cladding material and serve as starting points of crack, thus deteriorating the workability of the entire composite material. Therefore, in case of adding Mn to the cladding material, Mn content in the cladding material is set in the range of 0.3 to 1.8 mass %.

Si (Silicon): 0.04 to 1.2 Mass %

Si improves the strength of the cladding material like Mn, when being added to the cladding material. When Si content is less than 0.04 mass %, the improvement of the strength is not sufficient. When Si content is more than 1.2 mass %, the susceptibility to intergranular corrosion is increased and the corrosion resistance is lowered. Therefore, in case of adding Si to the cladding material, Si content is set in the range of 0.04 to 1.2 mass %. Please note that Mn and Si have the same effect and therefore it is only necessary to add at least one of Mn and Si.

Zn (Zinc): 2 to 9 Mass %

Zn is added to the cladding material in order to make a potential of the cladding material to be base. In this case, when Cu content in the core material is 0.2 mass % or less, a sufficient sacrifice anode effect can be achieved and the corrosion resistance can be maintained, even if Zn content in the cladding material is less than 2 mass %. However, when Cu content in the core material exceeds 0.2 mass % but does not exceed 1.0 mass %, it is necessary to set Zn content in the cladding material to the range of 2 to 9 mass %. This is because a sufficient potential difference cannot be ensured between the cladding material and grain boundaries when Zn content in the cladding material is less than 2 mass %. In this case, intergranular corrosion occurs and the corrosion resistance of the core material in the cladding material-side is deteriorated. On the other hand, when Zn content in the cladding material exceeds 9 mass %, a rate of self-corrosion of the cladding material itself increases. Thus, the cladding material is exhausted early, a time period during which the cladding material has a sacrifice anode effect is shortened, and the corrosion resistance is deteriorated. Please note that it is preferable that Zn content be 3 mass % or more in order to keep a good balance between the strength and the corrosion resistance while the amount of Si is increased.

The strength of the cladding material can be further improved by adding at least one of Mn and Si as described above and further adding at least one of Fe, Cr, Mg, and Cu. This is effective for the improvement of the strength of the entire thickness.

Fe: 0.02 to 0.25 Mass %

Fe makes the crystal grains in the cladding material finer and is solved in the form of solid solution, thereby improving the strength of the cladding material. When Fe content is less than 0.02 mass %, the effect of making the crystal grains finer and the effect of improving the strength are not sufficient. When Fe content exceeds 0.25 mass %, the amount of intermetallic compounds and crystallized particles that contain Fe in the cladding material is increased so as to increase cathode sites. Thus, a corrosion rate of the cladding material is increased and the corrosion resistance is deteriorated. Therefore, in case of adding Fe, Fe content is set in the range of 0.25 mass % or less. It is more preferable that Fe content be in the range of 0.02 to 0.2 mass %.

Cr: 0.01 to 0.30 Mass %

Cr is an element that improves the corrosion resistance and the strength in the cladding material. When Cr content exceeds 0.3 mass %, the corrosion resistance and the strength of the cladding material cannot be further improved. Moreover, since the amount of crystallized particles that contain Cr is increased so as to increase cathode sites, the corrosion rate of the cladding material itself is increased and the corrosion resistance is deteriorated. For this reason, Cr content is set in the range of 0.3 mass % or less. On the other hand, in the case where Cr content is 0.01 mass % or less, the effects of improving the strength and the corrosion resistance cannot be obtained. Therefore, when Cr is added, Cr content is set in the range of 0.01 to 0.30 mass %.

Mg: 0.005 to 0.15 Mass %

Mg in the form of solid solution in the cladding material improves the strength of the cladding material. Moreover, in the case where Mg and Si exist together in the cladding material, Mg can further improve the strength because of an effect achieved by dispersion of Mg₂Si precipitates. When Mg content exceeds 0.15 mass %, Mg degrades the brazeability at a site at which the cladding material is bonded. For this reason, Mg content is set to 0.15 mass % or less. In addition, when Mg content is less than 0.005 mass %, the effect of improving the strength is small. Therefore, in case of adding Mg, Mg content is set in the range of 0.005 to 0.15 mass %.

Cu: 0.001 to 0.15 Mass %

Cu in the form of solid solution in the cladding material improves the strength of the cladding material. In the case where Cu content in the cladding material exceeds 0.15 mass %, the potential of the cladding material is noble. Thus, even if Cu content in the core material is set in the range of 0.2 to 1 mass % and the content of Zn in the cladding material is set in the range of 2 to 7%, the sacrifice anode effect of the cladding material with respect to the core material is lowered and therefore the corrosion resistance of the core material on the cladding material-side is deteriorated. In the case where Cu content is less than 0.001 mass %, the effect of improving the strength is small and the sufficient increase of the strength of the cladding material cannot be achieved.

Cladding Ratio of the Cladding Material: 6 to 30% of An Entire Thickness of the Aluminum Alloy Composite Material

When a cladding ratio of the cladding material having the above-noted composition of the present invention is set to 6% or more, it is possible to obtain the sufficient strength while maintaining the corrosion resistance, even if the aluminum alloy composite material is made very thin. In the case where the cladding ratio is smaller than 6%, the sacrifice anode effect of the cladding material is not sufficient. Thus, the corrosion resistance of the core material is deteriorated. For this reason, the cladding ratio of the cladding material having the composition of the present invention is set to 6% or more with respect to the entire thickness.

Moreover, in the case where the cladding ratio of the cladding material is set to 30% or more, the thickness of the core material is relatively reduced and the corrosion resistance of the core material on the outer-surface side is deteriorated. Therefore, an upper limit of the cladding ratio is set to 30%. Thus, the cladding ratio of the cladding material is set to 6 to 30%.

It is Preferable That Zn Content be 3 Mass % or More and a Zn/Si Ratio be 4 or More

Although addition of Si to the cladding material improves the strength of the cladding material, it deteriorates the corrosion resistance (intergranular corrosion resistance). In order to keep a good balance between the strength and the corrosion resistance in a state where the amount of Si is increased, it is preferable that Zn content be set to 3 mass % or more. Moreover, when a Zn/Si ratio is set to 4 or more, the corrosion resistance and the strength that are in preferable ranges, respectively, can be achieved at the same time, even if the aluminum alloy composite material is made very thin. Therefore, it is preferable that Zn content be 3 mass % or more and the Zn/Si ratio be 4 or more.

[Brazing Material]

Next, the brazing material is described. An Al—Si based alloy such as A4045 alloy, that is used as a conventional brazing material, can be used as the brazing material of the present invention. Moreover, when Zn is added to the brazing material, the brazing material can be made to serve as a sacrifice anode positively. In this case, it is preferable that Zn content in the brazing material be set to be the same as that in the cladding material, i.e., 2 to 5 mass %. In addition, it is necessary to ensure a large potential difference between a fin member and an outer surface of the brazing material in order to ensure the corrosion resistance of a surface of the brazing material. Therefore, a minute amount of a metal element for increasing a potential, such as Cu may be added to the brazing material.

The aforementioned compositions of the core material, the cladding material, and the brazing material may be adjusted before cladding independently of each other. Alternatively, those compositions may be adjusted by controlling conditions of heating and cooling during brazing and the like so as to diffuse an element contained in one of the core material, the cladding material, and the brazing material to another material.

Next, the second aspect of the present invention is described. According to the second aspect of the present invention, Mn and Si are essential in the cladding material, unlike the first aspect of the present invention recited in claim 1. Moreover, the Si composition in the cladding material is different from that in the first aspect of the present invention, and an “average Si composition” in the cladding material is equal to or less than (Si content)×1/2. Except for the above, the second aspect of the present invention is the same as the first aspect of the present invention.

The second aspect of the present invention is now described with respect to the differences from the first aspect of the present invention. The detailed description of the same components as those in the first aspect of the present invention is omitted here. In the second aspect of the present invention, the composition of the cladding material is different from that in the first aspect of the present invention in the following points.

Si (Silicon): 0.5 to 1.2 Mass %

Si improves the strength of the cladding material in the same manner as that of Mn, when being added to the cladding material. Moreover, the effect of improving the strength is enhanced by adding both Mn and Si. When Si content is less than 0.5 mass %, the effect of improving the strength is not sufficient. When Si content is larger than 1.2 mass %, the susceptibility to intergranular corrosion is enhanced and the corrosion resistance is deteriorated. Therefore, in case of adding Si to the cladding material, Si content is set in the range of 0.5 to 1.2 mass %. Please note that Mn and Si have the same effects and therefore it is only necessary to add at least one of Mn and Si.

“Average Si Composition” in the Cladding Material is Equal to or Less Than (Si content)×1/2

In the case where an aluminum alloy contains Si, Si mainly exists in any of the following three ways. (1) Si exists in the aluminum alloy by itself. When Si content is about 1 mass % or less, Si usually exists in the form of solid solution or as a single-element Si precipitate having a size of 1 μm or less. (2) When about 1 mass % of Si and about 1 mass % of Mn exist together, Al—Mn—Si crystallized particles (having a grain size of several microns to several tens of microns) are generated during casting. (3) When about 1 mass % of Si and about 1 mass % of Mn exist together, Al—Mn—Si precipitates having a grain size of several microns or less are obtained other than the above crystallized particles during casting, depending on a condition of a heat (soaking) treatment and a cooling condition. The “average Si composition” means a total content of Si in the crystallized particles having the grain size described in (2) other than a large crystallized particles having a grain size of 10 μm or more, and Si described in (1) and (3). The “average Si composition” can be measured as Si concentration obtained by performing line analysis for Si and Mn with a commercially available EPMA (Electron Probe Micro-analyzer), except for a peak at which both Mn and Si show large intensities in a range of 10 μm or more (that is considered as a peak from large crystallized particles having a grain size of 10 μm or more).

In the case where the amount of Si in the form of solid solution in a material is large, an effect of accelerating precipitation of Al—Mn—Si, Al—Mn—Si—Cu, and Al—Si—Cu precipitates at grain boundaries during cooling of brazing is large. This is because Si in the form of solid solution in crystal grains can be easily diffused. Moreover, fine ones of the precipitates described in above (1), (2) and (3) behave in a similar manner to Si in the form of solid solution, because they can be easily solved to form solid solution during heating of the brazing. Thus, those fine precipitates also have the effect of accelerating precipitation of Al—Mn—Si, Al—Mn—Si—Cu, and Al—Si—Cu precipitates at grain boundaries during cooling. Thus, according to the present invention, a ratio of Si in the form of solid solution and the fine precipitates is lowered, i.e., the average Si composition is made equal to or less than (Si content)×0.5, thereby suppressing the amount of Si reaching the grain boundary during cooling of brazing, and providing an effect that precipitation at grain boundaries hardly occurs. When the average Si composition exceeds (Si content)×0.5, the amount of the precipitates at grain boundaries is increased and the corrosion resistance of the cladding material is deteriorated. Consequently, the corrosion resistance of the brazing sheet is lowered on the cladding material side.

The average Si composition can be controlled by making Si stable as Al—Mn—Si crystallized particles in advance. More specifically, the average Si composition can be set to (Si content)×0.5 or less by setting the temperature of soaking of ingot of the cladding material to 520 to 630° C. Moreover, in the case where the soaking temperature is set to 400 to 520° C., the same effect can be achieved by setting a cooling rate during casting to 0.1 to 5° C./hour.

Cooling rate during brazing: 100° C./minute or more

Precipitation of Al—Mn—Si, Al—Mn—Si—Cu, and Al—Si—Cu precipitates at grain boundaries can be suppressed by controlling the amount of Si solid solution in the aforementioned manner and further setting the cooling rate to 100° C./minute or more. Setting the cooling rate during brazing to 100° C./minute or more can shorten a time required for diffusion of Si, Cu, and the like. Thus, the amount of the precipitates at the grain boundaries can be reduced. Moreover, the above setting of the cooling rate during brazing can improve the corrosion resistance, when being combined with the suppression of the amount of Si solid solution.

Next, the third aspect of the present invention is described. The third aspect of the present invention defines the number of particles of precipitates or crystallized particles.

Density of Precipitates or Crystallized Particles Having an Average Grain Size Less Than 0.1 μm is 5.0×10⁸ Particles/mm³ or More

Intermetallic compounds mainly containing Al—Mn in the cladding material make at least a predetermined number of particles of the precipitates or crystallized particles having the size defined in the third aspect of the present invention distribute in the cladding material, thereby coarsening the grains in the cladding material after brazing and improving the corrosion resistance. After clad rolling of the cladding material and the core material and the like, those materials are cold-worked until an entire thickness reaches a predetermined thickness. In the case where there are precipitates or crystallized particles having the size defined in the present invention in the cladding material, a so-called pinning effect for suppressing movement of dislocation introduced into the cladding material during the cold work acts. That dislocation is set free from the pinning effect due to heating of brazing. However, in the case where there are only large precipitates or crystallized particles in the cladding material, the suppression of the movement of the dislocation by the pinning effect does not occur. Instead, recrystallization using the large precipitates or crystallized particles as nuclei preferentially occurs. Thus, after the brazing, the grain size in the cladding material becomes smaller and therefore intergranular corrosion can easily occur. However, when the precipitates or crystallized particles are controlled to be fine as in the present invention, the dislocation is pinned and is then set free during heating of the brazing. Thus, recrystallization is delayed and is then accelerated. Consequently, the grain size in the cladding material becomes large. Therefore, intergranular corrosion hardly occurs and the high corrosion resistance can be obtained.

When the size of the precipitates or crystallized particles is less then 0.01 μm, the pinning effect does not act sufficiently. Therefore, it is preferable that precipitates having a size in a range from approximately 0.01 μm to approximately 0.1 μm, the particle number of which is defined by the present invention or more, exist in the cladding material.

The size of the precipitates or crystallized particles in the cladding material can be adjusted in an appropriate manner in accordance with the composition of the cladding material, the temperature of a soaking process before rolling, and the heating temperature during the clad rolling.

Next, effects of Examples of the present invention are specifically described, comparing with Comparative Examples departing from the scope of the present invention.

Examples of the First Aspect of the Present Invention

Table 1 shows the composition of the core material and Table 2 shows the composition of the cladding material. In Table 1, Core materials Nos. A1 to A5 are Examples of the present invention and Core materials Nos. A6 to A18 are Comparative Examples. In Table 2, Cladding materials Nos. A1 to A4 and All to A13 are Examples of the present invention and Cladding materials Nos. A5 to A10 are Comparative Examples departing from the scope of the claims reciting the first aspect of the present invention.

TABLE 1
Core
material	Core material composition (mass %)
No.	Si	Fe	Cu	Mn	Mg	Cr	Ti	Al	Remarks
A1	0.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder		Examples
A2	0.8	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
A3	1.0	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
A4	0.8	0.05	0.30	1.3	0.0	0.1	0.12	Remainder
A5	0.8	0.05	0.90	1.3	0.0	0.1	0.12	Remainder
A6	0.03	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: less than its	Comparative examples
									lower limit of 0.05
									mass %
A7	0.8	0.05	0.15	1.3	0.0	0.1	0.12	Remainder	Cu: less than its
									lower limit of 0.2
									mass %
A8	0.8	0.05	0.70	0.2	0.0	0.1	0.12	Remainder	Mn: less than its
									lower limit of 0.3
									mass %
A9	0.8	0.05	0.70	1.3	0.3	0.1	0.12	Remainder	Mg: larger than its
									upper limit of 0.2
									mass %
A10	0.8	0.05	0.70	1.3	0.0	0.0	0.12	Remainder	Cr: less than its
									preferable lower limit of
									0.02 mass %
A11	0.8	0.05	0.70	1.3	0.0	0.1	0.00	Remainder	Ti: less than its
									lower limit of 0.02
									mass %
A12	1.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: larger than its
									upper limit of 1.4
									mass %
A13	0.8	0.3	0.70	1.3	0.0	0.1	0.12	Remainder	Fe: larger than its
									upper limit of 0.2
									mass %
A14	0.8	0.05	1.1	1.3	0.0	0.1	0.12	Remainder	Cu: larger than its
									upper limit of 1.0
									mass %
A15	0.8	0.05	0.70	1.9	0.0	0.1	0.12	Remainder	Mn: larger than its
									upper limit of 1.8
									mass %
A16	0.8	0.05	0.70	1.3	0.0	0.1	0.31	Remainder	Ti: larger than its
									upper limit of 0.3
									mass %
A17	0.8	0.05	0.70	1.3	0.0	0.4	0.12	Remainder	Cr: larger than its
									upper limit of 0.3
									mass %
A18	1.2	0.05	0.90	1.3	0.0	0.1	0.12	Remainder	Cu + Si: larger than
									its upper limit of 2.0
									mass %

TABLE 2
Skin
material	Skin material composition (mass %)
No.	Si	Fe	Cu	Mn	Mg	Zn	Cr	Al	Zn/Si	Remarks
A1	0.8	0.17	0.10	0.89	0.01	4.5	0.03	Remainder	5.6		Examples
A2	0.04	0.17	0.02	0.9	0.02	4.5	0.05	Remainder	90
A3	0.80	0.20	0.02	0.9	0.01	4.1	0.03	Remainder	5.1
A4	0.6	0.20	0.03	0.8	0.08	3.0	0.15	Remainder	4.9
A5	0.03	0.17	0.08	0.4	0.01	4.1	0.03	Remainder	136.7	Si: less than its	Comparative examples
										lower limit of 0.04
										mass %
A6	1.0	0.19	0.08	0.4	0.02	4.5	0.05	Remainder	4.5	Si: larger than its
										upper limit of 0.9
										mass %
A7	0.1	0.22	0.03	0.2	0.10	3.2	0.15	Remainder	3.2	Mn: less than its
										lower limit of 0.3
										mass %
A7-2	0.8	0.18	0.10	2.3	0.02	4.2	0.15	Remainder	5.25	Mn: larger than its
										upper limit of 1.8
										mass %
A8	0.85	0.20	0.08	1.1	0.12	3.2	0.03	Remainder	3.7	Zn/Si ratio: less
										than 4
A9	0.4	0.21	0.03	0.4	0.11	1.8	0.05	Remainder	4.5	Zn: less than its
										lower limit of 2 mass %
A10	0.25	0.22	0.03	0.6	0.03	9.5	0.15	Remainder	20.4	Zn: larger than its
										upper limit of 9 mass %
A11	0.08	0.18	0.12	0.9	0.10	3.8	0.15	Remainder	47.5		Examples
A12	0.75	0.18	0.02	0.5	0.02	4.5	0.10	Remainder	6.0
A13	0.35	0.19	0.03	0.5	0.05	3.3	0.10	Remainder	9.4
A14	0.8	0.30	0.04	0.9	0.10	4.2	0.10	Remainder	5.25	Fe: larger than its	Comparative examples
										upper limit of 0.25
										mass %
A15	0.8	0.01	0.01	0.9	0.08	4.2	0.03	Remainder	5.25	Fe: less than its
										lower limit of 0.02
										mass %
A16	0.75	0.18	0.11	0.85	0.09	5.2	0.50	Remainder	6.93	Cr: larger than its
										upper limit of 0.30
										mass %
A17	0.75	0.18	0.12	0.85	0.01	5.2	0.005	Remainder	6.93	Cr: less than its
										lower limit of 0.01
										mass %
A18	0.6	0.16	0.03	0.85	0.2	4.0	0.03	Remainder	6.67	Mg: larger than its
										upper limit of 0.15
										mass %
A19	0.6	0.16	0.05	0.85	0.002	4.0	0.03	Remainder	6.67	Mg: less than its
										lower limit of 0.005
										mass %
A20	0.85	0.15	0.20	0.85	0.02	4.1	0.03	Remainder	4.82	Cu: larger than its
										upper limit of 0.15
										mass %
A21	0.85	0.15	0.0002	0.85	0.02	4.1	0.03	Remainder	4.82	Cu: less than its
										lower limit of 0.001
										mass %

For each of the core materials listed in Table 1 and each of the cladding materials listed in Table 2, an aluminum alloy composite material for brazing shown in FIG. 1 was manufactured using a brazing material (JIS4045 alloy; Si: 10.5 mass %, Fe: 0.05 mass %, Cu: 0.05 mass %, Ti: 0.02 mass %, and the remainder of Al and unavoidable impurities). FIG. 1 is a cross-sectional view of the aluminum alloy composite material for brazing according to an example of the present invention. As shown in FIG. 1, the aluminum alloy composite material 4 includes a cladding material 2 and a brazing material 3 that are respectively formed on surfaces of a cladding material 1. Table 3 shows combinations of the core material and the cladding material in the aluminum alloy composite material, the thickness of each of the core material and the cladding material, the thickness of the brazing material, and the entire thickness of the composite material.

	TABLE 3
					Cladding
	Core material	Skin material	Brazing		ratio of
	Core		Skin		material	Entire	skin
	material	Thickness	material	Thickness	Thickness	Thickness	material
No.	No.	(μm)	No.	(μm)	(μm)	(mm)	(%)	Remarks
Examples	A1	A1	105	A1	30	15	0.15	20.0
	A2	A1	105	A2	30	15	0.15	20.0
	A3	A2	110	A3	25	15	0.15	16.7
	A4	A2	105	A4	30	15	0.15	20.0
	A5	A3	105	A1	30	15	0.15	20.0
	A6	A3	110	A3	25	15	0.15	16.7
	A7	A3	105	A4	30	15	0.15	20.0
	A8	A4	105	A11	30	15	0.15	20.0
	A9	A4	105	A12	30	15	0.15	20.0
	A10	A5	115	A13	20	15	0.15	13.3
Comparative	A11	A6	105	A3	30	15	0.15	20.0	Si in core material: less
Examples									than its lower limit of
									0.05 mass %
	A12	A7	105	A3	30	15	0.15	20.0	Cu in core material: less
									than its lower limit of 0.2
									mass %
	A13	A8	105	A3	30	15	0.15	20.0	Mn in core material: less
									than its lower limit of 0.3
									mass %
	A14	A9	105	A3	30	15	0.15	20.0	Mg in core material:
									larger than its upper
									limit of 0.2 mass %
	A15	A10	105	A3	30	15	0.15	20.0	Cr in core material: less
									than its preferable lower
									limit of 0.02 mass %
	A16	A11	105	A3	30	15	0.15	20.0	Ti in core material: less
									than its lower limit of
									0.02 mass %
	A17	A12	105	A3	30	15	0.15	20.0	Si in core material:
									larger than its upper
									limit of 1.4 mass %
	A18	A13	105	A3	30	15	0.15	20.0	Fe in core material:
									larger than its upper
									limit of 0.2 mass %
	A19	A14	105	A3	30	15	0.15	20.0	Cu in core material:
									larger than its upper
									limit of 1.0 mass %
	A20	A15	105	A3	30	15	0.15	20.0	Mn in core material:
									larger than its upper
									limit of 1.8 mass %
	A21	A16	105	A3	30	15	0.15	20.0	Ti in core material:
									larger than its upper
									limit of 0.3 mass %
	A22	A17	105	A3	30	15	0.15	20.0	Cr in core material:
									larger than its upper
									limit of 0.3 mass %
	A23	A18	105	A3	30	15	0.15	20.0	Cu + Si: larger than 2.0
	A24	A3	105	A5	30	15	0.15	20.0	Si in skin material: less
									than its lower limit of
									0.04 mass %
	A25	A3	105	A6	30	15	0.15	20.0	Si in skin material:
									larger than its upper
									limit of 0.9 mass %
	A26	A3	105	A7	30	15	0.15	20.0	Mn in skin material: less
									than its lower limit of 0.3
									mass %
	A27	A3	105	A7-2	30	15	0.15	20.0	Mn in skin material:
									larger than its upper
									limit of 1.8 mass %
	A28	A3	105	A8	30	15	0.15	20.0	Zn/Si in skin material ≦4
	A29	A3	105	A9	30	15	0.15	20.0	Zn in the skin material:
									less than its lower limit
									of 2 mass %
	A30	A3	105	A10	30	15	0.15	20.0	Zn in skin material:
									larger than its upper
									limit of 9 mass %
	A31	A3	105	A14	30	15	0.15	20.0	Fe in skin material:
									larger than its upper
									limit of 0.25 mass %
	A32	A3	105	A15	30	15	0.15	20.0	Fe in skin material: lower
									than its lower limit of
									0.02 mass %
	A33	A3	105	A6	30	15	0.15	20.0	Cr in skin material:
									larger than its upper
									limit of 0.3 mass %
	A34	A3	105	A17	30	15	0.15	20.0	Cr in skin material: less
									than its lower limit of
									0.01 mass %
	A35	A3	105	A18	30	15	0.15	20.0	Mg in skin material: less
									than its upper limit of
									0.15 mass %
	A36	A3	105	A19	30	15	0.15	20.0	Mg in skin material: less
									than its lower limit of
									0.005 mass %
	A37	A3	105	A20	30	15	0.15	20.0	Cu in skin material:
									larger than its upper
									limit of 0.15 mass %
	A38	A3	105	A21	30	15	0.15	20.0	Cu in skin material: less
									than its lower limit of
									0.001 mass %
	A39	A3	127	A3	8	15	0.15	5.3	Cladding ratio of skin
									material: less than 6%
	A40	A3	85	A3	50	15	0.15	33.3	Cladding ratio of skin
									material: larger than 30%

For each of the composite materials listed in Table 3, a brazeability test, a measurement of tensile strength, and an anticorrosion test were performed in the following manner. In the brazeability test, 5 g/m² of Nocolok flux was applied onto a brazing-material side surface of the aluminum alloy composite material and was then dried. Then, that aluminum alloy composite material was heated in a nitrogen atmosphere having a dew point of −40 ° C. under a condition in which the temperature was increased to 600° C. and was kept at 600° C. for two minutes.

FIG. 2 is a perspective view showing a part of a tube of a radiator. In actual manufacturing of the radiator, brazing is performed in a state where the tube 34, a fin 35 for radiating heat, and a header 36 for connecting the tube 34 are assembled, as shown in FIG. 2. Moreover, the tube 34 is formed by a core material 31, a cladding material 32, and a brazing material 33, as shown in FIG. 3. In this case, the brazeability was evaluated based on a fluid coefficient obtained by a drop test (“drop type fluidity test” described in Aluminum Brazing Handbook, published by January, 1992, Japan Light Metal Welding and Construction Association, p. 126), considering simplification and quantification of the evaluation of brazeability.

The evaluation result is shown below in Table 4. In Table 4, the aluminum alloy composite material having a fluidity of 65% or more is shown with circle, whereas the aluminum alloy composite material having a fluidity less than 65% is shown with cross.

TABLE 4
			Depth of	Depth of
			corrosion	corrosion on	Reason why
	Brazeability	Tensile	on brazing	skin	Comparative
	(fluid	strength	material	material	Example is
No.	coefficient) %	Mpa	side μm	side μm	inferior	Remarks
Examples	A1	70%◯	162◯	◯	◯
	A2	70%◯	160◯	◯	◯
	A3	70%◯	164◯	◯	◯
	A4	70%◯	159◯	◯	◯
	A5	70%◯	163◯	◯	◯
	A6	70%◯	165◯	◯	◯
	A7	70%◯	166◯	◯	◯
	A8	70%◯	159◯	◯	◯
	A9	70%◯	160◯	◯	◯
	A10	70%◯	159◯	◯	◯
Comparative	A11	70%◯	148X	◯	◯	Insufficient	Si in core material: less
Examples						post-braze	than its lower limit of
						strength	0.05 mass %
	A12	70%◯	145X	◯	◯	Insufficient	Cu in core material: less
						post-braze	than its lower limit of
						strength	0.2 mass %
	A13	70%◯	146X	◯	◯		Mn in core material: less
							than its lower limit of
							0.3 mass %
	A14	60%X	165◯	◯	◯	Insufficient	Mg in core material:
						brazeability	larger than its upper
						in case of the	limit of 0.2 mass %
						core material
						containing Mg
						of 0.3 mass %
	A15	70%◯	158◯	◯	◯	Slightly	Cr in core material: less
						insufficient	than its preferable
						strength	lower limit, 0.02 mass %
	A16	70%◯	162◯	X	◯	Deterioration	Ti in core material: less
						of corrosion	than its lower limit of
						resistance of	0.02 mass %
						core material
	A17	—	—	—	—	Occurrence of	Si in core material:
						melting of	larger than its upper
						core material	limit of 1.4 mass %
	A18	70%◯	162◯	X	◯	Deterioration	Fe in core material:
						of corrosion	larger than its upper
						resistance of	limit of 0.2 mass %
						core material
	A19	—	—	—	—	Occurrence of	Cu in core material:
						melting of	larger than its upper
						core material	limit of 1.0 mass %
	A20	70%◯	164◯	◯	◯	Lowering of	Mn in core material:
						productivity	larger than its upper
							limit of 1.8 mass %
	A21	70%◯	162◯	◯	◯	Lowering of	Ti in core material:
						productivity	larger than its upper
							limit of 0.3 mass %
	A22	70%◯	163◯	◯	◯	Lowering of	Cr in core material:
						productivity	larger than its upper
							limit of 0.3 mass %
	A23	—	—	—	—	Occurrence of	Cu + Si in core material:
						melting of	larger than its upper
						core material	limit of 2.0 mass %
	A24	70%◯	156X	◯	◯	Insufficient	Si in skin material: less
						post-braze	than its lower limit of
						strength	0.04 mass %
	A25	70%◯	167◯	◯	X	Deterioration	Si in skin material:
						of corrosion	larger than its upper
						resistance on	limit of 0.9 mass %
						skin material
						side
	A26	70%◯	157X	◯	◯	Insufficient	Mn in skin material: less
						post-braze	than its lower limit of
						strength	0.3 mass %
	A27	70%◯	165◯	◯	◯	Lowering of	Mn in skin material:
						the	larger than its upper
						productivity	limit of 1.8 mass %
	A28	70%◯	166◯	◯	X	Deterioration	Zn/Si in skin material ≦4
						of corrosion
						resistance on
						skin material
						side
	A29	70%◯	164◯	◯	X	Deterioration	Zn in skin material: less
						of corrosion	than its lower limit of 2
						resistance on	mass %
						skin material
						side
	A30	70%◯	164◯	◯	X	Deterioration	Zn in skin material:
						of corrosion	larger than its upper
						resistance on	limit of 9 mass %
						skin material
						side
	A31	70%◯	160◯	◯	X	Deterioration	Fe in skin material:
						of corrosion	larger than its upper
						resistance on	limit of 0.25 mass %
						skin material
						side
	A32	70%◯	155	◯	◯	Insufficient	Fe in skin material: less
						post-braze	than its lower limit of
						strength	0.02 mass %
	A33	70%◯	161◯	◯	X	Deterioration	Cr in skin material:
						of corrosion	larger than its upper
						resistance on	limit of 0.3 mass %
						skin material
						side
	A34	70%◯	157X	◯	X	Insufficient	Cr in skin material: less
						post-braze	than its lower limit of
						strength,	0.01 mass %
						deterioration
						of corrosion
						resistance on
						skin material
						side
	A35	70%◯	167◯	◯	◯	Deterioration	Mg in skin material:
						of	larger than its upper
						brazeability	limit of 0.15 mass %
						at a brazing
						site on skin
						material side
	A36	70%◯	157X	◯	◯	Insufficient	Mg in skin material: less
						post-braze	than its lower limit of
						strength	0.005 mass %
	A37	70%◯	168◯	◯	X	Deterioration	Cu in skin material:
						of corrosion	larger than its upper
						resistance on	limit of 0.15 mass %
						skin material
						side
	A38	70%◯	157X	◯	◯	Deterioration	Cu in skinmaterial: less
						of post-braze	than its lower limit of
						strength	0.001 mass %
	A39	70%◯	162◯	◯	X	Deterioration	Cladding ratio of skin
						of corrosion	material: less than 6%
						resistance on
						skin material
						side
	A40	70%◯	160◯	X	◯	Deterioration	Cladding ratio of skin
						of corrosion	material: larger than
						resistance on	30%
						brazing
						material side

In order to obtain the post-braze strength, a tensile test (JISZ2241) was performed at a room temperature for the aluminum alloy composite material that was heated in a similar manner to that in the aforementioned brazeability test. The result of the tensile test is also shown in Table 4. The post-braze strength exceeding 158 MPa is shown with circle, whereas the post-braze strength equal to or less than 158 MPa is shown with cross.

In a corrosion test on the brazing material side, CASS test was performed for 250 hours in a row for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test. The result of this test is also shown in Table 4. In a field of “Depth of corrosion on brazing material side, in Table 4, the composite material in which the depth of the corrosion on the brazing material side was equal to or smaller than 70 μm is shown with circle, while the composite material in which that depth exceeded 70 μm is shown with cross.

In order to obtain the corrosion resistance on the cladding material side, a corrosion test was performed for the cladding material side of the aluminum alloy composite material. In the corrosion test on the cladding material side, a corrosion test was performed for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test, by using artificial water (Cl: 300 ppm by mass, SO₄: 100 ppm by mass, and Cu: 5 ppm by mass). While the aluminum alloy composite material was immersed in the artificial water, a cycle test that includes a process for keeping the aluminum alloy composite material at 88° C. for 8 hours (containing a heating time from a room temperature to 88° C.) and a process for keeping the aluminum alloy composite material at a room temperature for 16 hours (containing a cooling time from 88° C. to the room temperature) was performed for 39 days. The result of this test is also shown in Table 4. In a field of “Depth of corrosion on cladding material side” in Table 4, the composite material in which the depth of corrosion on the cladding material side was equal to or less than 30 μm is shown with circle, whereas the composite material in which that depth exceeded 30 μm is shown with cross.

As shown in Table 4, Examples A1 to A10 of the present invention were good in all the brazeability, the tensile strength, the corrosion depth on the brazing material side, and the corrosion depth on the cladding material side. On the other hand, Comparative Example All was insufficient in the post-braze strength, because the amount of Si in the core material was less than its lower limit. For Comparative Example A12, the post-braze strength was insufficient, because the amount of Cu in the core material was less than its lower limit. For Comparative Example A13, the post-braze strength was not sufficient, because the amount of Mn in the core material was less than its lower limit. For Comparative Example A14, the brazeability was not good, because the amount of Mg in the core material exceeded its upper limit. For Comparative Example A15, the strength was slightly inferior, because the amount of Cr in the core material was less than its lower limit. For Comparative Example A16, the corrosion resistance of the core material was deteriorated, because the amount of Ti in the core material was less than its lower limit. For Comparative Example A17, melting of the core material occurred, because the amount of Si in the core material exceeded its upper limit. For Comparative Example A18, the corrosion resistance of the core material was deteriorated, because the amount of Fe in the core material exceeded its upper limit. For Comparative Example A19, melting of the core material occurred, because the amount of Cu in the core material exceeded its upper limit. For Comparative Example A20, the productivity was deteriorated, because the amount of Mn in the core material exceeded its upper limit. For Comparative Example A21, the productivity was deteriorated, because the amount of Ti in the core material exceeded its upper limit. For Comparative Example A22, the productivity was deteriorated, because the amount of Cr in the core material exceeded its upper limit. For Comparative Example A23, melting of the core material occurred, because the total amount of Cu and Si in the core material exceeded its upper limit.

For Comparative Example A24, the post-braze strength was not sufficient, because the amount of Si in the cladding material was less than its lower limit. For Comparative Example A25, the corrosion resistance on the cladding material side was deteriorated, because the amount of Si in the cladding material exceeded its upper limit. For Comparative Example A26, the post-braze strength was not sufficient, because the amount of Mn in the cladding material was less than its lower limit. For Comparative Example A27, the productivity was lowered, because the amount of Mn in the cladding material exceeded its upper limit. For Comparative Example A28, the corrosion resistance on the cladding material side was deteriorated, because Zn/Si in the cladding material was less than its lower limit. For Comparative Example A29, the corrosion resistance on the cladding material side was deteriorated, because the amount of Zn in the cladding material was less than its lower limit. For Comparative Example A30, the corrosion resistance on the cladding material side was degraded, because the amount of Zn in the cladding material exceeded its upper limit. For Comparative Example A31, the corrosion resistance on the cladding material side was deteriorated, because the amount of Fe in the cladding material exceeded its upper limit. For Comparative Example A32, the post-braze strength was not sufficient, because the amount of Fe in the cladding material was less than its lower limit. For Comparative Example A33, the corrosion resistance on the cladding material side was deteriorated, because the amount of Cr in the cladding material exceeded its upper limit. For Comparative Example A34, the post-braze strength was not sufficient and the corrosion resistance on the cladding material side was deteriorated, because the amount of Cr in the cladding material was less than its lower limit. For Comparative Example A35, the brazeability at a brazing site on the cladding material side was deteriorated, because the amount of Mg in the cladding material exceeded its upper limit. For Comparative Example A36, the post-braze strength was not sufficient, because the amount of Mg in the cladding material was less than its lower limit. For Comparative Example A37, the corrosion resistance on the cladding material side was deteriorated, because the amount of Cu in the cladding material exceeded its upper limit. For Comparative Example A38, the post-braze strength was deteriorated, because the amount of Cu in the cladding material was less than its lower limit. For Comparative Example A39, the corrosion resistance on the cladding material side was deteriorated, because the cladding ratio of the cladding material was less than its lower limit. For Comparative Example A40, the corrosion resistance on the brazing material side was deteriorated, because the cladding ratio of the cladding material exceeded its upper limit.

Examples of the Second Aspect of the Present Invention

Effects of Examples of the second aspect of the present invention are now described specifically, comparing with Comparative Examples departing from the scope of the second aspect of the present invention.

Table 5 shows the composition of the core material and Table 6 shows the composition of the cladding material. In Table 5, Core materials Nos. B1 to B5 are Examples of the present invention and Core materials Nos. B6 to B18 are Comparative Examples. In Table 6, Cladding materials Nos. B1 to B4 and B11 to B13 are Examples of the present invention and Cladding materials Nos. B5 to B10 are Comparative Examples departing from the scope of the claims reciting the second aspect of the present invention.

TABLE 5
Core
material	Core material composition (mass %)
No.	Si	Fe	Cu	Mn	Mg	Cr	Ti	Al	Remarks
B1	0.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder		Examples
B2	0.8	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
B3	1.0	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
B4	0.8	0.05	0.30	1.3	0.0	0.1	0.12	Remainder
B5	0.8	0.05	0.90	1.3	0.0	0.1	0.12	Remainder
B6	0.03	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: less than its lower limit	Comparative examples
									of 0.05 mass %
B7	0.8	0.05	0.15	1.3	0.0	0.1	0.12	Remainder	Cu: less than its lower limit
									of 0.2 mass %
B8	0.8	0.05	0.70	0.2	0.0	0.1	0.12	Remainder	Mn: less than its lower limit
									of 0.3 mass %
B9	0.8	0.05	0.70	1.3	0.3	0.1	0.12	Remainder	Mg: larger than its upper
									limit of 0.2 mass %
B10	0.8	0.05	0.70	1.3	0.0	0.0	0.12	Remainder	Cr: less than its preferable
									lower limit of 0.02 mass %
B11	0.8	0.05	0.70	1.3	0.0	0.1	0.00	Remainder	Ti: less than its lower limit
									of 0.02 mass %
B12	1.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: larger than its upper
									limit of 1.4 mass %
B13	0.8	0.3	0.70	1.3	0.0	0.1	0.12	Remainder	Fe: larger than its upper
									limit of 0.2 mass %
B14	0.8	0.05	1.1	1.3	0.0	0.1	0.12	Remainder	Cu: larger than its upper
									limit of 1.0 mass %
B15	0.8	0.05	0.70	1.9	0.0	0.1	0.12	Remainder	Mn: larger than its upper
									limit of 1.8 mass %
B16	0.8	0.05	0.70	1.3	0.0	0.1	0.31	Remainder	Ti: larger than its upper
									limit of 0.3 mass %
B17	0.8	0.05	0.70	1.3	0.0	0.4	0.12	Remainder	Cr: larger than its upper
									limit of 0.3 mass %
B18	1.2	0.05	0.90	1.3	0.0	0.1	0.12	Remainder	Cu + Si: larger than its
									upper limit of 2.0 mass %

TABLE 6
Skin
material	Skin material composition (mass %)
No.	Si	Fe	Cu	Mn	Mg	Zn	Cr	Al	Zn/Si	Remarks
B1	0.8	0.17	0.10	0.89	0.01	4.5	0.03	Remainder	5.6		Examples
B2	0.04	0.17	0.02	0.9	0.02	4.5	0.05	Remainder	90
B3	0.80	0.20	0.02	0.9	0.01	4.1	0.03	Remainder	5.1
B4	0.6	0.20	0.03	0.8	0.08	3.0	0.15	Remainder	4.9
B5	0.4	0.17	0.08	0.4	0.01	4.1	0.03	Remainder	136.7	Si: less than its	Comparative examples
										lower limit of
										0.5 mass %
B6	1.3	0.19	0.08	0.4	0.02	4.5	0.05	Remainder	4.5	Si: larger than
										its upper limit
										of 1.2 mass %
B7	0.1	0.22	0.03	0.2	0.10	3.2	0.15	Remainder	3.2	Mn: less than its
										lower limit of
										0.3 mass %
B7-2	0.8	0.18	0.10	2.3	0.02	4.2	0.15	Remainder	5.25	Mn: larger than
										its upper limit
										of 1.8 mass %
B8	0.85	0.20	0.08	1.1	0.12	3.2	0.03	Remainder	3.7	Zn/Si ratio:
										less than 4
B9	0.4	0.21	0.03	0.4	0.11	1.8	0.05	Remainder	4.5	Zn: less than its
										lower limit of 2
										mass %
B10	0.25	0.22	0.03	0.6	0.03	9.5	0.15	Remainder	20.4	Zn: larger than
										its upper limit
										of 9 mass %
B11	0.08	0.18	0.12	0.9	0.10	3.8	0.15	Remainder	47.5		Examples
B12	0.75	0.18	0.02	0.5	0.02	4.5	0.10	Remainder	6.0
B13	0.35	0.19	0.03	0.5	0.05	3.3	0.10	Remainder	9.4
B14	0.8	0.30	0.04	0.9	0.10	4.2	0.10	Remainder	5.25	Fe: larger than	Comparative examples
										its upper limit
										of 0.25 mass %
B15	0.8	0.01	0.01	0.9	0.08	4.2	0.03	Remainder	5.25	Fe: less than its
										lower limit of
										0.02 mass %
B16	0.75	0.18	0.11	0.85	0.09	5.2	0.50	Remainder	6.93	Cr: larger than
										its upper limit
										of 0.30 mass %
B17	0.75	0.18	0.12	0.85	0.01	5.2	0.005	Remainder	6.93	Cr: less than its
										lower limit of
										0.01 mass %
B18	0.6	0.16	0.03	0.85	0.2	4.0	0.03	Remainder	6.67	Mg: larger than
										its upper limit
										of 0.15 mass %
B19	0.6	0.16	0.05	0.85	0.002	4.0	0.03	Remainder	6.67	Mg: less than its
										lower limit of
										0.005 mass %
B20	0.85	0.15	0.20	0.85	0.02	4.1	0.03	Remainder	4.82	Cu: larger than
										its upper limit
										of 0.15 mass %
B21	0.85	0.15	0.0002	0.85	0.02	4.1	0.03	Remainder	4.82	Cu: less than its
										lower limit of
										0.001 mass %
B22	Content:	0.17	0.10	0.89	0.01	4.5	0.03	Remainder	5.6	Average Si	Examples
	0.8,									composition ≦ (Si
	Amount									content) × 0.5
	of solid
	solution:
	0.3
B23	Content:	0.17	0.10	0.89	0.01	4.5	0.03	Remainder	5.6	Average Si	Comparative
	0.8,									composition > (Si	examples
	Amount									content) × 0.5
	of solid
	solution:
	0.45

For each of the core materials listed in Table 5 and each of the cladding materials listed in Table 6, an aluminum alloy composite material for brazing shown in FIG. 1 was manufactured using a brazing material (JIS4045 alloy; Si: 10.5 mass %, Fe: 0.05 mass %, Cu: 0.05 mass %, Ti: 0.02 mass %, the remainder was formed from Al and unavoidable impurities). Table 7 shows combinations of the core material and the cladding material in the aluminum alloy composite material, the thickness of each of the core material and the cladding material, the thickness of the brazing material, and the entire thickness of the composite material.

	TABLE 7
					Cladding
	Core material	Skin material	Brazing		ratio of
	Core		Skin		material	Entire	skin
	material	Thickness	material	Thickness	Thickness	thickness	material
No.	No.	(μm)	No.	(μm)	(μm)	(mm)	(%)	Remarks
Examples	B1	B1	105	B1	30	15	0.15	20.0
	B2	B1	105	B2	30	15	0.15	20.0
	B3	B2	110	B3	25	15	0.15	16.7
	B4	B2	105	B4	30	15	0.15	20.0
	B5	B3	105	B1	30	15	0.15	20.0
	B6	B3	110	B3	25	15	0.15	16.7
	B7	B3	105	B4	30	15	0.15	20.0
	B8	B4	105	B11	30	15	0.15	20.0
	B9	B4	105	B12	30	15	0.15	20.0
	B10	B5	115	B13	20	15	0.15	13.3
Comparative	B11	B6	105	B3	30	15	0.15	20.0	Si in core material:
Examples									less than its lower
									limit of 0.05 mass %
	B12	B7	105	B3	30	15	0.15	20.0	Cu in core material:
									less than its lower
									limit of 0.2 mass %
	B13	B8	105	B3	30	15	0.15	20.0	Mn in core material:
									less than its lower
									limit of 0.3 mass %
	B14	B9	105	B3	30	15	0.15	20.0	Mg in core material:
									larger than its upper
									limit of 0.2 mass %
	B15	B10	105	B3	30	15	0.15	20.0	Cr in core material:
									less than its
									preferable lower
									limit of 0.02 mass %
	B16	B11	105	B3	30	15	0.15	20.0	Ti in core material:
									less than its lower
									limit of 0.02 mass %
	B17	B12	105	B3	30	15	0.15	20.0	Si in core material:
									larger than its upper
									limit of 1.4 mass %
	B18	B13	105	B3	30	15	0.15	20.0	Fe in core material:
									larger than its upper
									limit of 0.2 mass %
	B19	B14	105	B3	30	15	0.15	20.0	Cu in core material:
									larger than its upper
									limit of 1.0 mass %
	B20	B15	105	B3	30	15	0.15	20.0	Mn in core material:
									larger than its upper
									limit of 1.8 mass %
	B21	B16	105	B3	30	15	0.15	20.0	Ti in core material:
									larger than its upper
									limit of 0.3 mass %
	B22	B17	105	B3	30	15	0.15	20.0	Cr in core material:
									larger than its upper
									limit of 0.3 mass %
	B23	B18	105	B3	30	15	0.15	20.0	Cu + Si in core
									material: larger
									than its upper limit
									of 2.0 mass %
	B24	B3	105	B5	30	15	0.15	20.0	Si in skin material:
									less than its lower
									limit of 0.5 mass %
	B25	B3	105	B6	30	15	0.15	20.0	Si in skin material:
									larger than its upper
									limit of 1.2 mass %
	B26	B3	105	B7	30	15	0.15	20.0	Mn in skin material:
									less than its lower
									limit of 0.3 mass %
	B27	B3	105	B7-2	30	15	0.15	20.0	Mn in skin material:
									larger than its upper
									limit of 1.8 mass %
	B28	B3	105	B8	30	15	0.15	20.0	Zn/Si in skin
									material ≦4
	B29	B3	105	B9	30	15	0.15	20.0	Zn in skin material:
									less than its lower
									limit of 2 mass %
	B30	B3	105	B10	30	15	0.15	20.0	Zn in skin material:
									larger than its upper
									limit of 9 mass %
	B31	B3	105	B14	30	15	0.15	20.0	Fe in skin material:
									larger than its upper
									limit of 0.25 mass %
	B32	B3	105	B15	30	15	0.15	20.0	Fe in skin material:
									less than its lower
									limit of 0.02 mass %
	B33	B3	105	B16	30	15	0.15	20.0	Cr in skin material:
									larger than its upper
									limit of 0.3 mass %
	B34	B3	105	B17	30	15	0.15	20.0	Cr in skin material:
									less than its lower
									limit of 0.01 mass %
	B35	B3	105	B18	30	15	0.15	20.0	Mg in skin material:
									larger than its upper
									limit of 0.15 mass %
	B36	B3	105	B19	30	15	0.15	20.0	Mg in skin material:
									less than its lower
									limit of 0.005 mass %
	B37	B3	105	B20	30	15	0.15	20.0	Cu in skin material:
									larger than its upper
									limit of 0.15 mass %
	B38	B3	105	B21	30	15	0.15	20.0	Cu in skin material:
									less than its lower
									limit of 0.001 mass %
	B39	B3	127	B3	8	15	0.15	5.3	Cladding ratio of
									skin material: less
									than 6%
	B40	B3	85	B3	50	15	0.15	33.3	Cladding ratio of
									skin material:
									larger than 30%
Examples	B41	B3	105	B22	30	15	0.15	20.0
Comparative	B42	B3	105	B23	30	15	0.15	20.0	Average Si
Examples									composition > (Si
									content) × 0.5
Examples	B43	B3	105	B22	30	15	0.15	20.0

In Table 7, a cooling rate during brazing was 30 to 70° C./minute for Examples B1 to B10 and B41 and Comparative Examples B11 to B40 and B42. Moreover, the cooling rate during brazing was 120° C./minute for Comparative Example B42.

For each of the composite materials listed in Table 7, a brazeability test, a measurement of tensile strength, and an anticorrosion test were performed in the following manner. In the brazeability test, 5 g/m² of Nocolok flux was applied onto a brazing-material side surface of the aluminum alloy composite material and was then dried. Then, that aluminum alloy composite material was heated in a nitrogen atmosphere having a dew point of −40 ° C. under a condition in which the temperature was increased to 600° C. and was kept at 600° C. for two minutes.

The brazeability was evaluated by a fluid coefficient obtained by a drop test (“drop type fluidity test” described in Aluminum Brazing Handbook, published by January, 1992, Japan Light Metal Welding & Construction Association, p. 126), considering simplification and quantification of the evaluation of the brazeablity.

The evaluation result is shown below in Table 8. In Table 8, the aluminum alloy composite material having a fluidity of 65% or more is shown with circle, whereas the aluminum alloy composite material having a fluidity less than 65% is shown with cross.

TABLE 8
			Depth of	Depth of
			corrosion	corrosion
	Brazeability	Tensile	on brazing	on skin	Reason why
	(fluid	strength	material	material	Comparative Example
No.	coefficient) %	MPa	side μm	side μm	is inferior	Remarks
Examples	B1	70%◯	162◯	◯	◯
	B2	70%◯	160◯	◯	◯
	B3	70%◯	164◯	◯	◯
	B4	70%◯	159◯	◯	◯
	B5	70%◯	163◯	◯	◯
	B6	70%◯	165◯	◯	◯
	B7	70%◯	166◯	◯	◯
	B8	70%◯	159◯	◯	◯
	B9	70%◯	160◯	◯	◯
	B10	70%◯	159◯	◯	◯
Comparative	B11	70%◯	148X	◯	◯	Insufficient	Si in core material: less than its
Examples						post-braze strength	lower limit of 0.05 mass %
	B12	70%◯	145X	◯	◯	Insufficient	Cu in core material: less than its
						post-braze strength	lower limit of 0.2 mass %
	B13	70%◯	146X	◯	◯		Mn in core material: less than its
							lower limit of 0.3 mass %
	B14	60%X	165◯	◯	◯	Insufficient	Mg in core material: larger than
						brazeability in case	its upper limit of 0.2 mass %
						of core material
						containing Mg of 0.3
						mass %
	B15	70%◯	158◯	◯	◯	Slightly insufficient	Cr in core material: less than its
						strength	preferable lower limit of 0.02
							mass %
	B16	70%◯	162◯	X	◯	Deterioration of	Ti in core material: less than its
						corrosion resistance	lower limit of 0.02 mass %
						of core material
	B17	—	—	—	—	Occurrence of melting	Si in core material: larger than
						of core material	its upper limit of 1.4 mass %
	B18	70%◯	163◯	X	◯	Deterioration of	Fe in core material: larger than
						corrosion resistance	its upper limit of 0.2 mass %
						of core material
	B19	—	—	—	—	Occurrence of melting	Cu in core material: larger than
						of core material	its upper limit of 1.0 mass %
	B20	70%◯	164◯	◯	◯	Lowering of the	Mn in core material: larger than
						productivity	its upper limit of 1.8 mass %
	B21	70%◯	162◯	◯	◯	Lowering of the	Ti in core material: larger than
						productivity	its upper limit of 0.3 mass %
	B22	70%◯	163◯	◯	◯	Lowering of the	Cr in core material: larger than
						productivity	its upper limit of 0.3 mass %
	B23	—	—	—	—	Occurrence of melting	Cu + Si in core material: larger
						of core material	than its upper limit of 2.0 mass %
	B24	70%◯	156X	◯	◯	Insufficient	Si in skin material: less than its
						post-braze strength	lower limit of 0.04 mass %
	B25	70%◯	167◯	◯	X	Deterioration of	Si in skin material: larger than
						corrosion resistance	its upper limit of 0.9 mass %
						on skin material side
	B26	70%◯	157X	◯	◯	Insufficient	Mn in skin material: less than its
						post-braze strength	lower limit of 0.3 mass %
	B27	70%◯	165◯	◯	◯	Lowering of the	Mn in skin material: larger than
						productivity	its upper limit of 1.8 mass %
	B28	70%◯	166◯	◯	X	Deterioration of	Zn/Si in skin material ≦4
						corrosion resistance
						on skin material side
	B29	70%◯	164◯	◯	X	Deterioration of	Zn in skin material: less
						corrosion resistance	than its lower limit of 2
						on skin material side	mass %
	B30	70%◯	164◯	◯	X	Deterioration of	Zn in skin material: larger
						corrosion resistance	than its upper limit of 9
						on skin material side	mass %
	B31	70%◯	160◯	◯	X	Deterioration of	Fe in skin material: larger
						corrosion resistance	than its upper limit of 0.25
						on skin material side	mass %
	B32	70%◯	155	◯	◯	Insufficient	Fe in skin material: less
						post-braze strength	than its lower limit of 0.02
							mass %
	B33	70%◯	161◯	◯	X	Deterioration of	Cr in skin material: larger
						corrosion resistance	than its upper limit of 0.3
						on skin material side	mass %
	B34	70%◯	157X	◯	X	Insufficient	Cr in skin material: less
						post-braze strength,	than its lower limit of 0.01
						deterioration of	mass %
						corrosion resistance
						on skin material side
	B35	70%◯	167◯	◯	◯	Deterioration of	Mg in skin material: larger
						brazeability at a	than its upper limit of 0.15
						brazing site on skin	mass %
						material side
	B36	70%◯	157X	◯	◯	Insufficient	Mg in skin material: less
						post-braze strength	than its lower limit of 0.005
							mass %
	B37	70%◯	168◯	◯	X	Deterioration of	The amount of Cu in skin
						corrosion resistance	material: larger than its
						on skin material side	upper limit of 0.15 mass %
	B38	70%◯	157X	◯	◯	Deterioration of	Cu in skin material: less
						post-braze strength	than its lower limit of 0.001
							mass %
	B39	70%◯	162◯	◯	X	Deterioration of	Cladding ratio of skin
						corrosion resistance	material: less than 6%
						on skin material side
	B40	70%◯	160◯	X	◯	Deterioration of	Cladding ratio of skin
						corrosion resistance	material: larger than 30%
						on brazing material
						side
Examples	70%◯	162◯	◯	⊚		Small amount of grain boundary
B41						precipitation in skin
						material
Comparative	70%◯	163◯	◯	◯
Examples B42
Examples	70%◯	163◯	◯	⊚		Small amount of grain boundary
B43						precipitation in skin
						material

In order to obtain the post-braze strength, a tensile test (JIS ◯◯◯) was performed for the aluminum alloy composite material that was heated during brazing in a similar manner to that in the aforementioned brazeability test. The result of the tensile test is also shown in Table 8. The post-braze strength exceeding 158 MPa is shown with circle, whereas the post-braze strength equal to or less than 158 MPa is shown with cross.

In a corrosion test on the brazing material side, CASS test (JIS ◯◯◯) was performed for 250 hours in a row for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test. The result of this test is also shown in Table 8. In a field of “Depth of corrosion on brazing material side, in Table 8, the composite material in which the depth of the corrosion on the brazing material side was equal to or smaller than 70 μm is shown with circle, while the composite material in which that depth exceeded 70 μm is shown with cross.

In order to obtain the corrosion resistance on the cladding material side, a corrosion test was performed for the cladding material side of the aluminum alloy composite material. In the corrosion test on the cladding material side, a corrosion test was performed for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test, by using artificial water (Cl: 300 ppm by mass, SO₄: 100 ppm by mass, and Cu: 5 ppm by mass). While the aluminum alloy composite material was immersed in the artificial water, a cycle test that includes a process for keeping the aluminum alloy composite material at 88° C. for 8 hours (containing a heating time from a room temperature to 88° C.) and a process for keeping the aluminum alloy composite material at a room temperature for 16 hours (containing a cooling time from 88° C. to the room temperature) was performed for 30 days. A 30-days corrosion test and a 50-days corrosion test were performed in the aforementioned procedure. The result is shown in Table 8. In a field of “Depth of corrosion on cladding material side” in Table 8, the composite material in which the depth of corrosion on the cladding material side after 30 days was equal to or less than 30 μm is shown with circle, the composite material in which that depth after 30 days exceeded 30 μm is shown with cross, and the composite material in which that depth did not exceed 30 μm even after 50 days is shown with double circle. That is, the composite material in which the depth of corrosion in the cladding material did not exceed 30 μm after 30 days but was equal to or larger than 30 μm after 50 days is shown with circle.

As shown in Table 8, Examples B1 to B10 of the present invention were good in all the brazeability, the tensile strength, the corrosion depth on the brazing material side, and the corrosion depth on the cladding material side. On the other hand, Comparative Example B11 was insufficient in the post-braze strength because the amount of Si in the core material was less than its lower limit. For Comparative Example B12, the post-braze strength was insufficient, because the amount of Cu in the core material was less than its lower limit. For Comparative Example B13, the post-braze strength was not sufficient, because the amount of Mn in the core material was less than its lower limit. For Comparative Example B14, the brazeability was not good, because the amount of Mg in the core material exceeded its upper limit. For Comparative Example B15, the strength was slightly inferior, because the amount of Cr in the core material was less than its lower limit. For Comparative Example B16, the corrosion resistance of the core material was deteriorated, because the amount of Ti in the core material was less than its lower limit. For Comparative Example B17, melting of the core material occurred, because the amount of Si in the core material exceeded its upper limit. For Comparative Example B18, the corrosion resistance of the core material was deteriorated, because the amount of Fe in the core material exceeded its upper limit. For Comparative Example B19, melting of the core material occurred, because the amount of Cu in the core material exceeded its upper limit. For Comparative Example B20, the productivity was lowered, because the amount of Mn in the core material exceeded its upper limit. For Comparative Example B21, the productivity was lowered, because the amount of Ti in the core material exceeded its upper limit. For Comparative Example B22, the productivity was lowered, because the amount of Cr in the core material exceeded its upper limit. For Comparative Example B23, melting of the core material occurred, because the total amount of Cu and Si in the core material exceeded its upper limit.

For Comparative Example B24, the post-braze strength was not sufficient, because the amount of Si in the cladding material was less than its lower limit. For Comparative Example B25, the corrosion resistance on the cladding material side was deteriorated, because the amount of Si in the cladding material exceeded its upper limit. For Comparative Example B26, the post-braze strength was not sufficient, because the amount of Mn in the cladding material was less than its lower limit. For Comparative Example B27, the productivity was lowered, because the amount of Mn in the cladding material exceeded its upper limit. For Comparative Example B28, the corrosion resistance on the cladding material side was deteriorated, because Zn/Si in the cladding material was less than its lower limit. For Comparative Example B29, the corrosion resistance on the cladding material side was deteriorated, because the amount of Zn in the cladding material was less than its lower limit. For Comparative Example B30, the corrosion resistance on the cladding material side was deteriorated, because the amount of Zn in the cladding material exceeded its upper limit. For Comparative Example B31, the corrosion resistance on the cladding material side was deteriorated, because the amount of Fe in the cladding material exceeded its upper limit. For Comparative Example B32, the post-braze strength was not sufficient, because the amount of Fe in the cladding material was less than its lower limit. For Comparative Example B33, the corrosion resistance on the cladding material side was deteriorated, because the amount of Cr in the cladding material exceeded its upper limit. For Comparative Example B34, the post-braze strength was not sufficient and the corrosion resistance on the cladding material side was deteriorated, because the amount of Cr in the cladding material was less than its lower limit. For Comparative Example B35, the brazeability at a brazing site on the cladding material side, because the amount of Mg in the cladding material exceeded its upper limit. For Comparative Example B36, the post-braze strength was not sufficient, because the amount of Mg in the cladding material was less than its lower limit. For Comparative Example B37, the corrosion resistance on the cladding material side was deteriorated, because the amount of Cu in the cladding material exceeded its upper limit. For Comparative Example B38, the post-braze strength was deteriorated, because the amount of Cu in the cladding material was less than its lower limit. For Comparative Example B39, the corrosion resistance on the cladding material side was deteriorated, because the cladding ratio of the cladding material was less than its lower limit. For Comparative Example B40, the corrosion resistance on the brazing material side was deteriorated, because the cladding ratio of the cladding material exceeded its upper limit.

Moreover, Examples B41 and B43 used the cladding material No. B22 and had the average Si composition that was equal to or less than (Si content)×0.5. On the other hand, Comparative Example B42 used the cladding material No. B23 and had the average Si composition that was larger than (Si content)×0.5. Therefore, Examples B41 and B43 were good in the brazeability, the tensile strength, the corrosion depth on the brazing material side, and the corrosion depth on the cladding material side, and were excellent in the corrosion depth on the cladding material side, especially.

Next, effects of Examples of the third aspect of the present invention are specifically described, comparing with Comparative Examples departing from the scope of the third aspect of the present invention.

Table 9 shows the composition of the core material and Table 10 shows the composition of the cladding material. In Table 9, Core materials Nos. C1 to C7 are Examples of the present invention and Core materials Nos. C8 to C17 are Comparative Examples. In Table 10, Cladding materials Nos. C1 to C7 are Examples of the present invention and Cladding materials Nos. C8 to C13 are Comparative Examples departing from the scope of the claims reciting the third aspect of the present invention.

	TABLE 9
	Core
	material	Core material composition (mass %)
	No.	Si	Fe	Cu	Mn	Mg	Cr	Ti	Al
Examples	C1	0.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
	C2	0.8	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
	C3	1.0	0.05	0.70	1.3	0.0	0.1	0.12	Remainder
	C4	0.8	0.05	0.30	1.3	0.0	0.1	0.12	Remainder
	C5	0.8	0.05	0.90	1.3	0.0	0.1	0.12	Remainder
Comparative	C6	0.8	0.05	0.70	1.3	0.0	0.0	0.12	Remainder	Cr: less than
Examples										its lower
										limit
	C7	0.8	0.05	0.70	1.3	0.0	0.4	0.12	Remainder	Cr: larger
										than its
										upper limit
	C8	0.03	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: less than
										its lower
										limit
	C9	0.8	0.05	0.15	1.3	0.0	0.1	0.12	Remainder	Cu: less than
										its lower
										limit
	C10	0.8	0.05	0.70	0.2	0.0	0.1	0.12	Remainder	Mn: less than
										its lower
										limit
	C11	0.8	0.05	0.70	1.3	0.3	0.1	0.12	Remainder	Mg: larger
										than its
										upper limit
	C12	0.8	0.05	0.70	1.3	0.0	0.1	0.00	Remainder	Ti: less than
										its lower
										limit
	C13	1.4	0.05	0.70	1.3	0.0	0.1	0.12	Remainder	Si: larger
										than its
										upper limit
	C14	0.8	0.3	0.70	1.3	0.0	0.1	0.12	Remainder	Fe: larger
										than its
										upper limit
	C15	0.8	0.05	1.1	1.3	0.0	0.1	0.12	Remainder	Cu: larger
										than its
										upper limit
	C16	0.8	0.05	0.70	1.9	0.0	0.1	0.12	Remainder	Mn: larger
										than its
										upper limit
	C17	0.8	0.05	0.70	1.3	0.0	0.1	0.31	Remainder	Ti: larger
										than its
										upper limit

	TABLE 10
	Skin
	material	Skin material composition (mass %)
	No.	Si	Fe	Cu	Mn	Mg	Zn	Cr	Al
Examples	C1	0.8	0.17	0.10	0.89	0.01	4.5	0.03	Remainder
	C2	0.04	0.17	0.02	0.9	0.02	4.5	0.05	Remainder
	C3	0.80	0.20	0.02	0.9	0.01	4.1	0.03	Remainder
	C4	0.6	0.20	0.03	0.8	0.08	3.0	0.15	Remainder
	C5	0.75	0.18	0.11	0.85	0.09	5.2	0.3	Remainder	Addition of Cr
	C6	0.6	0.16	0.03	0.85	0.15	4.0	0.03	Remainder	Addition of Mg
	C7	0.85	0.15	0.15	0.85	0.02	4.1	0.03	Remainder	Addition of Cu
Comparative	C8	0.03	0.17	0.08	0.4	0.01	4.1	0.03	Remainder	Si: less than
Examples										its lower
										limit
	C9	1.3	0.19	0.08	0.4	0.02	4.5	0.05	Remainder	Si: larger
										than its upper
										limit
	C10	0.1	0.22	0.03	0.2	0.10	3.2	0.15	Remainder	Mn: less than
										its lower
										limit
	C11	0.8	0.18	0.10	2.3	0.02	4.2	0.15	Remainder	Mn: larger
										than its upper
										limit
	C12	0.4	0.21	0.03	0.4	0.11	1.8	0.05	Remainder	Zn: less than
										its lower
										limit
	C13	0.25	0.22	0.03	0.6	0.03	9.5	0.15	Remainder	Zn: larger
										than its upper
										limit

For each of the core materials listed in Table 9 and each of the cladding materials listed in Table 10, an aluminum alloy composite material for brazing shown in FIG. 1 was manufactured using a brazing material (JIS4045 alloy; Si: 10.5 mass %, Fe: 0.05 mass %, Cu: 0.05 mass %, Ti: 0.02 mass %, the remainder was formed from Al and unavoidable impurities). Tables 11 and 12 show combinations of the core material and the cladding material in the aluminum alloy composite material, the thickness of each of the core material and the cladding material, the thickness of the brazing material, and the entire thickness of the composite material.

	TABLE 11
						Density of
						particles of
						precipitates
						or crystals
						having a
						size less
						than 0.1 μm
	Core material	Skin material	Brazing		Cladding	(the number
	Core		Skin		material	Entire	ratio of	of particles
	material	Thickness	material	Thickness	Thickness	thickness	skin	per cubic
	No.	(μm)	No.	(μm)	(μm)	mm	material %	millimeter)
Examples	C1	C1	105	C1	30	15	0.15	20.0	5.2 × 108
	C2	C1	105	C2	30	15	0.15	20.0
	C3	C2	110	C3	25	15	0.15	16.7
	C4	C2	105	C4	30	15	0.15	20.0
	C5	C3	105	C1	30	15	0.15	20.0
	C6	C3	110	C3	25	15	0.15	16.7
	C7	C3	105	C4	30	15	0.15	20.0
	C8	C3	105	C5	30	15	0.15	20.0
	C9	C3	105	C6	30	15	0.15	20.0
	C10	C3	105	C7	30	15	0.15	20.0
Comparative	C11	C6	105	C3	30	15	0.15	20.0
Examples	C12	C7	105	C3	30	15	0.15	20.0

	TABLE 12
						Density of
						particles of
						precipitates
						or crystals
						having a
						size less
						than 0.1 μm
	Core material	Skin material	Brazing		Cladding	(the number
	Core		Skin		material	Entire	ratio of	of particles
	material	Thickness	material	Thickness	Thickness	thickness	skin	per cubic
	No.	(μm)	No.	(μm)	(μm)	mm	material %	millimeter)
Comparative	C13	C6	105	C3	30	15	0.15	20.0
Examples	C14	C7	105	C3	30	15	0.15	20.0
	C15	C8	105	C3	30	15	0.15	20.0
	C16	C9	105	C3	30	15	0.15	20.0
	C17	C11	105	C3	30	15	0.15	20.0
	C18	C12	105	C3	30	15	0.15	20.0
	C19	C13	105	C3	30	15	0.15	20.0
	C20	C14	105	C3	30	15	0.15	20.0
	C21	C15	105	C3	30	15	0.15	20.0
	C22	C16	105	C3	30	15	0.15	20.0
	C23	C3	105	C8	30	15	0.15	20.0
	C24	C3	105	C9	30	15	0.15	20.0
	C25	C3	105	C10	30	15	0.15	20.0
	C26	C3	105	C11	30	15	0.15	20.0
	C27	C3	105	C12	30	15	0.15	20.0
	C28	C3	105	C13	30	15	0.15	20.0
	C29	C3	127	C3	8	15	0.15	5.3
	C30	C3	85	C3	50	15	0.15	33.3
	C31	C3	105	C3	30	15	0.15	20	4.8 × 108

For each of the composite materials listed in Tables 11 and 12, a brazeability test, a measurement of tensile strength, and an anticorrosion test were performed in the following manner. In the brazeability test, 5 g/m² of Nocolok flux was applied onto a brazing-material side surface of the aluminum alloy composite material and was then dried. Then, that aluminum alloy composite material was heated in a nitrogen atmosphere having a dew point of −40° C. under a condition in which the temperature was increased to 600° C. and was kept at 600° C. for two minutes.

The brazeability was evaluated based on a fluid coefficient obtained by a drop test in the aforementioned manner, considering simplification and quantification of the evaluation of the brazeability.

The evaluation result is shown below in Tables 13 and 14. In Tables 13 and 14, in a field of “Brazeability”, the aluminum alloy composite material having a fluidity of 65% or more is shown with circle, whereas the aluminum alloy composite material having a fluidity less than 65% is shown with cross.

Moreover, transmission electron microscopic observation was made so as to measure the thickness from fringes of equal thickness and to measure the number of particles of precipitates or crystallized particles in the cladding material per unit volume.

	TABLE 13
				Depth of	Depth of
				corrosion	corrosion	Reason why
		Brazeability	Tensile	on brazing	on skin	Comparative
		(fluid	strength	material	material	Example is
	No.	coefficient) %	MPa	side μm	side μm	inferior
Examples	C1	70%◯	162◯	◯	◯
	C2	70%◯	160◯	◯	◯
	C3	70%◯	164◯	◯	◯
	C4	70%◯	159◯	◯	◯
	C5	70%◯	163◯	◯	◯
	C6	70%◯	165◯	◯	◯
	C7	70%◯	166◯	◯	◯
	C8	70%◯	168◯	◯	◯	Deterioration
						of corrosion
						resistance on
						skin material
						side
	C9	70%◯	167◯	◯	◯	Deterioration
						of corrosion
						resistance on
						skin material
						side
	C10	70%◯	168◯	◯	◯	Deterioration
						of corrosion
						resistance on
						skin material
						side
Comparative	C11	70%◯	158◯	◯	◯	Slightly
Examples						insufficient
						strength
	C12	70%◯	163◯	◯	◯	Slight lowering
						of productivity

	TABLE 14
				Depth of	Depth of
				corrosion	corrosion
		Brazeability	Tensile	on brazing	on skin
		(fluid	strength	material	material	Reason why Comparative
	No.	coefficient) %	MPa	side μm	side μm	Example is inferior
Comparative	C13	70%◯	148X	◯	◯	Insufficient post-braze
Examples						strength
	C14	70%◯	145X	◯	◯	Insufficient post-braze
						strength
	C15	70%◯	146X	◯	◯
	C16	60%X	165◯	◯	◯	Inferior brazeability
	C17	70%◯	162◯	X	◯	Deterioration of
						corrosion resistance of
						core material
	C18	—	—	—	—	Occurrence of melting of
						core material
	C19	70%◯	163◯	X	◯	Deterioration of
						corrosion resistance of
						core material
	C20	—	—	—	—	Occurrence of melting of
						core material
	C21	70%◯	164◯	◯	◯	Lowering of
						productivity
	C22	70%◯	162◯	◯	◯	Lowering of
						productivity
	C23	70%◯	156X	◯	◯	Insufficient post-braze
						strength
	C24	70%◯	167◯	◯	X	Deterioration of
						corrosion resistance on
						skin material side
	C25	70%◯	157X	◯	◯	Insufficient post-braze
						strength
	C26	70%◯	165◯	◯	◯	Lowering of
						productivity
	C27	70%◯	164◯	◯	X	Deterioration of
						corrosion resistance on
						skin material side
	C28	70%◯	164◯	◯	X	Deterioration of
						corrosion resistance on
						skin material side
	C29	70%◯	162◯	◯	X	Deterioration of
						corrosion resistance on
						skin material side
	C30	70%◯	160◯	X	◯	Degradation of the
						corrosion resistance on
						the brazing material
						side
	C31	70%◯	162◯	◯	X	Deterioration of
						corrosion resistance on
						skin material side

In order to obtain the post-braze strength, a tensile test (JISZ2241) was performed for the aluminum alloy composite material after being heated in a similar manner to that in the aforementioned brazeability test. The result of the tensile test is also shown in Table 14. The post-braze strength exceeding 158 MPa is shown with circle, whereas the post-braze strength equal to or less than 158 MPa is shown with cross.

In the corrosion test on the brazing material side, CASS test (Item (5) of JISH8681) was performed for 250 hours in a row for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test. The result of this test is also shown in Table 14. In a field of “Depth of corrosion on brazing material side, in Table 14, the composite material in which the depth of the corrosion on the brazing side was equal to or smaller than 70 μm is shown with circle, whereas the composite material in which that depth exceeded 70 μm is shown with cross.

In order to obtain the corrosion resistance on the cladding material side, a corrosion test was performed for the cladding material side of the aluminum alloy composite material. In the corrosion test on the cladding material side, a corrosion test was performed for the aluminum alloy composite material that was heated in a similar manner to that in the brazeability test, by using artificial water (Cl: 300 ppm by mass, SO₄: 100 ppm by mass, and Cu: 5 ppm by mass). While the aluminum alloy composite material was immersed in the artificial water, a cycle test that includes a process for keeping the aluminum alloy composite material at 88° C. for 8 hours (containing a heating time from a room temperature to 88° C.) and a process for keeping the aluminum alloy composite material at a room temperature for 16 hours (containing a cooling time from 88° C. to the room temperature) was performed for 30 days. The result is shown in Table 14. In a field of “Depth of corrosion on cladding material side” in Table 14, the composite material in which the depth of corrosion on the cladding material side was equal to or less than 30 μm is shown with circle, whereas the composite material in which that depth exceeded 30 μm is shown with cross.

As shown in Table 14, Examples C1 to C10 of the present invention were good in all the brazeability, the tensile strength, the corrosion depth on the brazing material side, and the corrosion depth on the cladding material side. On the other hand, Comparative Example C11 was slightly insufficient in the post-braze strength, because the amount of Cr in the core material was less than its lower limit. For Comparative Example C12, the productivity was slightly lowered, because the amount of Cr in the core material exceeded its upper limit. For Comparative Example C13, the post-braze strength was not sufficient, because the amount of Si in the core material was less than its lower limit. For Comparative Example C14, the post-braze strength was not sufficient, because the amount of Cu in the core material was less than its lower limit. For Comparative Example C15, the post-braze strength was not sufficient, because the amount of Mn in the core material was less than its lower limit. For Comparative Example C16, the brazeability was inferior, because the amount of Mg in the core material exceeded its upper limit. For Comparative Example C17, the corrosion resistance of the core material was deteriorated, because the amount of Ti in the core material was lower than its lower limit. For Comparative Example C18, melting of the core material occurred, because the amount of Si in the core material exceeded its upper limit. For Comparative Example C19, the corrosion resistance of the core material was deteriorated, because the amount of Fe in the core material exceeded its upper limit. For Comparative Example C20, melting of the core material occurred, because the amount of Cu in the core material exceeded its upper limit. For Comparative Example C21, the productivity was lowered, because the amount of Mn in the core material exceeded its upper limit. For Comparative Example C22, the productivity was lowered, because the amount of Ti in the core material exceeded its upper limit.

For Comparative Example C23, the post-braze strength was not sufficient, because the amount of Si in the cladding material was lower than its lower limit. For Comparative Example C24, the corrosion resistance on the cladding material side was deteriorated, because the amount of Si in the cladding material exceeded its upper limit. For Comparative Example C25, the post-braze strength was not sufficient, because the amount of Mn in the cladding material was lower than its lower limit. For Comparative Example C26, the productivity was deteriorated, because the amount of Mn in the cladding material exceeded its upper limit. For Comparative Example C27, the corrosion resistance on the cladding material side was deteriorated, because the amount of Zn in the cladding material was less than its lower limit. For Comparative Example C28, the corrosion resistance on the cladding material side was deteriorated, because the amount of Zn in the cladding material exceeded its upper limit. For Comparative Example C29, the corrosion resistance on the cladding material side was deteriorated, because the cladding ratio of the cladding material was less than its lower limit. For Comparative Example C30, the corrosion resistance on the brazing material side was deteriorated, because the cladding ratio of the cladding material exceeded its upper limit. For Comparative Example C31, the corrosion resistance on the cladding material side was deteriorated, because the number of particles of the precipitates or crystallized particles having a predetermined size in the cladding material was equal to or less than its lower limit.

Claims

1. An aluminum alloy composite material for brazing, comprising: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material, the core material having a composition consisting essentially of 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, and 0.02 to 0.3 mass % of Ti in such a manner that a total content of Cu and Si is in a range of 2.0 mass % or less and a remainder of Al and unavoidable impurities, the cladding material containing 2 to 9 mass % of Zn, at least one selected from the group consisting of 0.3 to 1.8 mass % of Mn and 0.04 to 1.2 mass % of Si, and at least one selected from the group consisting of 0.02 to 0.25 mass % of Fe, 0.01 to 0.30 mass % of Cr, 0.005 to 0.15 mass % of Mg, and 0.001 to 0.15 mass % of Cu.

2. The aluminum alloy composite material according to claim 1, wherein the cladding material contains 3 mass % or more of Zn and a Zn/Si ratio is 4 or more.

3. An aluminum alloy composite material for brazing, comprising: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material, the core material having a composition that consisting essentially of 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, and 0.02 to 0.3 mass % of Ti in such a manner that a total content of Cu and Si is in a range of 2.0 mass % or less and a remainder of Al and unavoidable impurities, the cladding material containing 2 to 9 mass % of Zn, 0.3 to 1.8 mass % of Mn, 0.5 to 1.2 mass % of Si, and at least one selected from the group consisting of 0.02 to 0.25 mass % of Fe, 0.01 to 0.30 mass % of Cr, 0.005 to 0.15 mass % of Mg, and 0.001 to 0.15 mass % of Cu, wherein an average Si composition in the cladding material is equal to or less than 0.5 times Si content.

4. The aluminum alloy composite material according to claim 3, wherein the cladding material contains 3 mass % or more of Zn and a Zn/Si ratio is 4 or more.

5. A heat exchanger assembled by performing brazing that uses the aluminum alloy composite material for brazing as set forth in claim 3, as a brazing sheet, wherein the brazing is performed at a cooling rate of 100° C./minute or more.

6. An aluminum alloy composite material for brazing, comprising: a core material; a brazing material formed of an Al—Si based aluminum alloy on one surface of the core material; and a cladding material formed on the other surface of the core material with a cladding ratio of 6 to 30% with respect to an entire thickness of the aluminum alloy composite material, the core material having a composition that consisting essentially of 0.2 mass % or less of Mg, 0.3 mass % or less of Cr, 0.2 mass % or less of Fe, 0.2 to 1.0 mass % of Cu, 0.05 to 1.3 mass % of Si, 0.3 to 1.8 mass % of Mn, 0.02 to 0.3 mass % of Ti, and a remainder of Al and unavoidable impurities, the cladding material containing 2 to 9 mass % of Zn, and at least one selected from the group consisting of 0.3 to 1.8 mass % of Mn and 0.04 to 1.2 mass % of Si, wherein the cladding material further contains precipitates or crystallized particles having an average grain size smaller than 0.1 am with a density of 5.0×108 particles/mm3 or more.