Patent Application
20240150870
The present application claims priority from Japanese patent application JP 2022-177936 filed on Nov. 7, 2022, the entire content of which is hereby incorporated by reference into this application.
The present disclosure relates to an aluminum alloy and a method for producing the same.
By reducing the weight of automotive parts, fuel consumption can be improved and power consumption can be reduced. Therefore, consideration is being given to replacing conventionally used ferrous materials with aluminum materials or aluminum alloys.
For example, in JP 2010-18875 A, a high strength aluminum alloy with excellent castability and workability comprising 3.5 mass percent (mass % or % by mass) to 7.5 mass % of silicon (Si), 0.45 mass % to 0.8 mass % of magnesium (Mg), 0.05 mass % to 0.35 mass % of chromium (Cr) and the remainder consisting of aluminum (Al) and unavoidable impurities when the total is 100 mass % is disclosed.
In JP 2017-14541 A, an aluminum alloy sheet consisting of an Al—Mg—Si-based aluminum alloy, in which, in a differential scanning calorimetry curve with a temperature increase rate of 20° C./minute, an endothermic peak with the height “a” of 1.0 to 5.0 mW/g in the temperature range of 150 to 230° C. and two or more exothermic peaks in the temperature range of 230 to 270° C. are observed, and a ratio “b1/b2” of the peak height “b1” of the low-temperature side to the peak height “b2” of the high-temperature side in the exothermic peaks is 0.80 or less, is disclosed.
In the conventional technology, additional solution heat treatment and/or aging heat treatment is applied to the aluminum alloy after casting. The heat treatments result in the precipitation of Mg—Si-based precipitates in the aluminum alloy. The precipitates provide the hardness required for the parts and suppress natural aging. Therefore, in the conventional technology, the precipitates increase the hardness of the aluminum alloy to achieve high strength.
On the other hand, the aforementioned heat treatment processes can cause deformation of the parts due to heat treatment distortion, and can lead to high costs and high CO2 emissions due to thermal energy consumption.
Therefore, the present disclosure provides an aluminum alloy in which natural aging is suppressed. Furthermore, the present disclosure provides a method for producing an aluminum alloy that can produce an aluminum alloy having sufficient hardness without heat treatment processes after casting.
The inventors have examined various means to solve the aforementioned problems. As a result, the inventors have developed a new method for producing an aluminum alloy material containing Si, Mg, manganese (Mn), and iron (Fe). In the method of producing the aluminum alloy material containing Si, Mg, manganese (Mn), and iron (Fe), the inventors found that by controlling a cooling process of a molten alloy during casting, natural aging can be suppressed and an aluminum alloy with sufficient hardness can be produced, thus completing the present disclosure. In the aluminum alloy of the present disclosure, by controlling the cooling process of the molten alloy during casting, Al—Si—Fe—Mn-based compounds are preferentially precipitated, and the precipitation of Mg—Si-based compounds, which had been precipitated conventionally, is reduced.
In other words, the gist of the present disclosure is as follows.
In the method, the cooling process of (iv) includes a solidification holding process in which the molten alloy is held in a temperature range of 510° C. to 470° C. for 20 minutes to 40 minutes when a temperature of the molten alloy reaches the said temperature range.
The present disclosure provides the aluminum alloy in which natural aging is suppressed. Furthermore, the present disclosure provides the method for producing the aluminum alloy that can produce the aluminum alloy with sufficient hardness without the heat treatment processes after casting.
The following is a detailed description of the preferred embodiment of the present disclosure.
In this specification, the features of the present disclosure will be explained with reference to the drawings as appropriate. The aluminum alloy and the method for producing the same of the present disclosure are not limited to the following embodiments, and can be implemented in various forms with modifications and improvements that can be made by those skilled in the art, to the extent not departing from the gist of the present disclosure. In the present disclosure, the expression “numerical value (lower limit) to numerical value (upper limit)” indicates a range including the lower and upper limits.
The present disclosure relates to an Al—Si-based aluminum alloy comprising Si, Mg, Mn, Fe and unavoidable impurities, which comprises Al—Si—Mg—Fe—Mn-based compounds.
The Si content is not limited. The Si content, as a metal, is generally 0.1 mass % to 15 mass % based on the total mass of the Al—Si-based aluminum alloy. In one embodiment, the Si content, as a metal is 4 mass % to 12 mass % based on the total mass of the Al—Si-based aluminum alloy. Here, the Si content can be measured by ICP optical emission spectrometry.
The Mg content is not limited. The Mg content, as a metal, is generally 0.01 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. In one embodiment, the Mg content, as a metal, is 0.1 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. Here, the Mg content can be measured by ICP optical emission spectrometry.
The Mn content is not limited. The Mn content, as a metal, is usually 0.01 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. In one embodiment, the Mn content, as a metal, is 0.1 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. Here, the Mn content can be measured by ICP optical emission spectrometry.
The Fe content is not limited. The Fe content, as a metal, is generally 0.01 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. In one embodiment, the Fe content, as a metal, is 0.1 mass % to 1 mass %, based on the total mass of the Al—Si-based aluminum alloy. Here, the Fe content can be measured by ICP optical emission spectrometry.
The Al—Si aluminum alloy of the present disclosure can further comprise other alloying elements for modifying, such as one or more metals (other metals) selected from the group consisting of copper (Cu), titanium (Ti), nickel (Ni), zirconium (Zr), cobalt (Co), molybdenum (Mo), tungsten (W), zinc (Zn), lithium (Li), silver (Ag), gallium (Ga), germanium (Ge), scandium (Sc), strontium (Sr), indium (In), vanadium (V), praseodymium (Pr), samarium (Sm), tantalum (Ta), gold (Au), Beryllium (Be), chromium (Cr), arsenic (As), selenium (Se), yttrium (Y), niobium (Nb), ruthenium (Ru), rhodium (Rh), palladium (Pd), cadmium (Cd), tin (Sn), antimony (Sb), tellurium (Te), cerium (Ce), neodymium (Nd), promethium (Pm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), lutetium (Lu), hafnium (Hf), rhenium (Re), iridium (Jr), platinum (Pt), mercury (Hg), bismuth (Bi) and thorium (Th), as appropriate.
The content of each of the other metals is not limited. The content of each of the other metals, as a metal, based on the total mass of the Al—Si-based aluminum alloy, is usually 0.0001 mass % to 0.1 mass %. In one embodiment, the content of each of the other metals, as a metal, based on the total mass of the Al—Si-based aluminum alloy, is 0.001 mass % to 0.05 mass %. The content of all other metals, as metals, is usually 0.01 mass % to 1 mass % based on the total mass of the Al—Si-based aluminum alloy. In one embodiment, the content of all other metals, as metals, is 0.03 mass % to 0.1 mass % based on the total mass of the Al—Si-based aluminum alloy. In the other embodiment, the content of all other metals, as metals, is 0.04 mass % to 0.06 mass % based on the total mass of the Al—Si-based aluminum alloy. The respective contents of the other metals can be measured by methods known in the art although they vary depending on the alloying element. The respective contents of the other metals can be measured, for example, by ICP optical emission spectrometry.
The remainder of the Al—Si-based aluminum alloy, other than the aforementioned metals, consists of aluminum (Al) and unavoidable impurities.
The unavoidable impurities include phosphorus (P) and sulfur (S). The content of phosphorus (P) and sulfur (S) is not limited. The content of each of phosphorus (P) and sulfur (S) is usually 0.01 mass % or less based on the total mass of the Al—Si-based aluminum alloy. The respective contents of phosphorus (P) and sulfur (S) can be measured by methods known in the art although they vary depending on the element to be measured. For example, the respective contents of phosphorus (P) and sulfur (S) can be measured by ICP optical emission spectrometry.
In the Al—Si-based aluminum alloy of the present disclosure, the Al—Si—Mg—Fe—Mn-based compounds can be identified by EPMA mapping of the Al—Si-based aluminum alloy. In the EPMA mapping of the Al—Si-based aluminum alloy, the Al—Si—Mg—Fe—Mn-based compounds have the following characteristics (i) and (ii).
Here, with respect to the intensity (strength) (%) of K-α from various metals at a certain position in the field of 80 μm×80 μm, for example, in the case of Mg, the said intensity indicates the percentage (%) of the K-α line from Mg at a certain position in the field of 80 μm×80 μm when the entire K-α line from Mg in the field of 80 μm×80 μm is 100%.
The presence of Si in the Al—Si—Mg—Fe—Mn-based compounds in the Al—Si-based aluminum alloy can also be confirmed by EPMA, as with Mg, Mn, and Fe.
The shape of the Al—Si—Mg—Fe—Mn-based compounds is not limited. The shape of the Al—Si—Mg—Fe—Mn-based compounds can be spherical, polygonal, or lumpy, for example.
The average particle size of the Al—Si—Mg—Fe—Mn-based compounds is not limited. The average particle size of the Al—Si—Mg—Fe—Mn-based compounds is usually 30 nm to 300 nm as the average of the circular equivalent diameters of 100 particles in a TEM photograph. In one embodiment, the average particle size of the Al—Si—Mg—Fe—Mn-based compounds is 50 nm to 100 nm as the average of the circular equivalent diameters of 100 particles in a TEM photograph.
The Vickers hardness of the Al—Si-based aluminum alloy of the present disclosure is not limited. The Vickers hardness of the Al—Si-based aluminum alloy of the present disclosure is usually 40 HV to 100 HV, and in one embodiment, 50 HV to 60 HV.
The Vickers hardness after forced aging of the Al—Si-based aluminum alloy of the present disclosure is not limited. The Vickers hardness after forced aging (210° C.×90 min) of the Al—Si-based aluminum alloy of the present disclosure is usually 50 HV to 120 HV, and in one embodiment, 50 HV to 60 HV.
In other words, in the Al—Si-based aluminum alloy of the present disclosure, the change in the Vickers hardness before and after forced aging is usually 4% or less, and in one embodiment, 2% or less, as {|Vickers hardness after forced aging−Vickers hardness before forced aging|/Vickers hardness before forced aging}×100.
The Vickers hardness of the Al—Si-based aluminum alloy of the present disclosure can be measured by the Vickers hardness test.
Therefore, in the Al—Si aluminum alloy of the present disclosure, the natural aging is suppressed. Furthermore, the Al—Si-based aluminum alloy of the present disclosure do not require various heat treatments after casting.
The Al—Si-based aluminum alloy of the present disclosure is an Al—Si-based aluminum cast alloy. The cast alloy refers to a molding produced by casting. Therefore, the cast alloy includes a molding produced by low-pressure casting, gravity casting, die casting, etc.
The aluminum alloy in the present disclosure can be used as lightweight materials, such as automobile body parts, which can replace ferrous materials, by being formed by casting.
The Al—Si-based aluminum alloy of the present disclosure can be produced by the processes (i) through (iv) described in detail below.
In the process of (i), the raw materials for the Al—Si-based aluminum alloy are not limited. The raw materials for the Al—Si-based aluminum alloy include pure metals, compounds, and alloys of various metals. Aluminum ingots and aluminum scraps can be used as raw materials for aluminum. In addition, the raw materials for the Al—Si-based aluminum alloy include those in the state of powders, molten metals, and castings (e.g., aluminum alloy ingots). Basically, metals with high melting points can be added as mother alloys with other additive elements, while metals with low melting points can be added as pure metals.
The composition of the raw materials for the Al—Si-based aluminum alloy is adjusted so that the contents of various metals in the Al—Si-based aluminum alloy obtained after production are within the range described above. Therefore, the composition of the raw materials for the Al—Si-based aluminum alloy is the same as the composition of the Al—Si-based aluminum alloy, unless materials which volatilize during production are used as the raw materials.
In the process of (ii), the molten alloy can be prepared, for example, by heating the raw materials for the Al—Si-based aluminum alloy in a melting furnace, for example, an arc melting furnace, to a temperature where the liquid phase occurs, typically 680° C. to 1200° C., and in one embodiment 1000° C. to 1200° C.
In the process of (ii), with respect to aluminum and various metals, which are the raw materials for the Al—Si-based aluminum alloy, the order of addition, the method of addition, the temperature of addition, the time of addition, and the mixing method thereof are not limited. In the process of (ii), the molten alloy is prepared so that the respective metals are uniform.
For example, in the process of (ii) of the present disclosure, various metals are added to molten aluminum prepared by heating aluminum to 680° C., and the temperature of the molten alloy is then increased to the temperature at which the alloy system melts, e.g., 1000° C., to prepare a molten alloy.
In the process of (iii), the mold is not limited. Any mold known in the art can be used as a mold.
In the process of (iv), the molten alloy is solidified by cooling. The process of (iv) includes a solidification holding process. In the course of the solidification in the solidification holding process, when the temperature of the molten alloy reaches 510° C. to 470° C., and in one embodiment 500° C. to 480° C., at which the solidification starts, the temperature of the molten alloy is maintained in this temperature range for 20 minutes to 40 minutes, and in one embodiment for 30 minutes.
In the process of (iv), the cooling rate of the molten alloy is not limited. For example, the cooling rate of the molten alloy is usually 50° C./second to 200° C./second and in one embodiment, 80° C./second to 120° C./second.
In the process of (iv), by holding the molten alloy for the specific time in the specific temperature range, the Al—Si—Mg—Fe—Mn-based compounds are preferentially precipitated in the molten alloy, while the precipitation of Mg2Si is suppressed. Since Mg2Si can cause natural aging, the natural aging in the Al—Si-based aluminum alloy obtained after the process of (iv) is suppressed as a result of the suppression of Mg2Si precipitation. Therefore, in the Al—Si-based aluminum alloy obtained by the method for producing of the present disclosure, the hardness change due to aging can be suppressed.
The method for producing the Al—Si-based aluminum alloy may be any casting known in the art, except for the solidification holding process in the cooling process of (iv).
Casting is the process of pouring a molten metal (including a molten alloy) at high temperature into a cavity in a mold made of sand or metal and cooling the molten metal to solidify it.
Casting includes, for example, the usual melting and casting methods such as continuous casting, continuous casting rolling, semi-continuous casting (DC casting), hot top casting, or die casting.
While the following describes some Examples regarding the present disclosure, it is not intended to limit the present disclosure to those described in such Examples.
In addition, as a conventional Al—Si-based aluminum alloy, the conventional Al—Si-based aluminum alloy (Comparative Example 3) was produced by the processes (i) through (v) above, except that the cooling processes of (iv) and (v) were changed as follows: “The molten alloy poured in the pouring process of (iii) is cooled to 400° C. and the Al—Si-based aluminum alloy was removed from the mold, and then air-cooled to 25° C.”
Vickers hardness was measured for each Al—Si-based aluminum alloy obtained.
The presence (natural aging: Yes) or absence (natural aging: No) of natural aging in the Al—Si-based aluminum alloy can be confirmed by forced aging. Therefore, each Al—Si-based aluminum alloy for which Vickers hardness was measured was subsequently subjected to heat treatment (forced aging) at 210° C. for 90 minutes.
The Vickers hardness was again measured for each Al—Si-based aluminum alloy obtained after the forced aging. The results are shown in Table 2 and
Table 2 and
The Al—Si-based aluminum alloys of Example 1 and Comparative Example 1 were analyzed by EPMA.
On the other hand,
Mg2Si compounds stably increase hardness by heat treatment (aging treatment) and provide the Al—Si-based aluminum alloy with suppressed natural aging, and also impart the hardness required for the aluminum alloy properties. In other words, if Mg2Si compounds are present in the aluminum alloy, natural aging will occur and hardness increase will occur without heat treatment. In the Al—Si-based aluminum alloy of the present disclosure, the precipitates are Al—Si—Mg—Fe—Mn-based compounds, and, in the Al—Si-based aluminum alloy of the present disclosure, the precipitation of Mg2Si compounds is suppressed under an environment of 200° C. or lower. Therefore, natural aging, i.e., hardness increase due to Mg2Si compounds does not occur. Consequently, since the Al—Si-based aluminum alloy of the present disclosure does not require additional heat treatments, such as solution heat treatment and/or aging heat treatment, the influence due to heat treatment distortion can be suppressed, and furthermore, the increase in cost and CO2 emissions due to thermal energy consumption can be suppressed.
All publications, patents and patent applications cited in the present description are herein incorporated by reference as they are.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-177936 | Nov 2022 | JP | national |
