Patent Application
20170029924
The invention relates to a cooling roll for manufacturing an amorphous alloy strip, and a manufacturing apparatus of the amorphous alloy strip. In particular, the invention relates to a manufacturing apparatus of an amorphous alloy ribbon including a water-cooled cooling roll.
Conventionally, the use of iron-based amorphous alloys that have low power loss have been studied as iron cores of transformers and motors; and the practical development for transformers is advancing. However, applications in stacked core transformers have not yet been reported; and even manufacturers that employ stacked cores are hesitant to employ amorphous materials. Also, for motors, practical development substantially has not advanced; and there are only a few sporadic examples of applications of conventional thin strips (having a thickness of 30 μm or less) realized by much effort.
If a thick amorphous alloy strip can be manufactured industrially and inexpensively, applications would not be limited to wound-core transformers/reactors, etc., and would be possible for stacked cores and motors. For the wound-core transformer, increasing the thickness of the strip increases the space factor and improves the work efficiency of the core manufacturing process. Thereby, the volumes of the core and accordingly the coil including the winding are reduced. Due to the increased thickness, the hysteresis loss decreases; and in the commercial frequency range, a reduction effect of the core loss can be expected that is more than enough to cancel the increase of the eddy current loss. The increased thickness of the strip not only can reduce the power loss but also can increase the strength and rigidity. For motors that have high-speed rotation, an unprecedented product that can endure the strong centrifugal forces acting on the rotor can be realized.
The most general method for manufacturing an amorphous alloy is a so-called single-roll melt quenching method in which a cooling roll made of a metal or an alloy having a high thermal conductivity is rotated while causing a melt of an alloy to contact the outer circumferential surface of the roll via a nozzle to cause the alloy melt to coagulate into a ribbon configuration by rapid cooling. The single-roll melt quenching method is a method for manufacturing an amorphous alloy ribbon or sheet in which the melt is quenched by causing rapid movement of the heat of the melt to the cooling roll and by causing the melt to coagulate before crystallization. Here, an “amorphous alloy” is 50% amorphous or more by volume fraction and includes, as the remainder, a multi-phase alloy that has an amorphous parent phase and has nano-sized microcrystals dispersed and precipitated.
In the single-roll melt quenching method, an equilibrium state is reached where the temperature of the cooling roll increases as the amorphous alloy ribbon is manufactured and the heat amount received by the cooling roll from the melt balances the heat amount dissipated to the cooling water from the cooling roll. If the surface temperature of the cooling roll in the equilibrium state is a temperature low enough that the melt can be coagulated in the supercooled state, the amorphous alloy ribbon can be continued to be manufactured continuously. However, in the case where the roll temperature overheats in the casting and the cooling rate to pass through the glass transition temperature does not reach the prescribed cooling rate, the amorphous ribbon can be manufactured only for a finite period of time.
To manufacture a thick amorphous alloy strip, a heat amount that is proportional to the sheet thickness must be moved to the cooling roll. However, there was a limit of the heat amount that could be dissipated to the cooling water contacting the inner surface of the cooling roll. The cooling structure of conventional water-cooled rolls have been configurations in which the cooling water paths flow along the circumferential direction of the outer circumferential surface of the roll as shown in known examples (Patent Literatures 1, 2, and 3).
Also, in Patent Literature 4, although the cooling flow channels that pierce the side surface of the roll are distributed, the flow channels that contribute to the cooling of the roll are only the flow channels on the concentric circle of the outermost circumference; and the heat dissipation capacity is insufficient. The flow channels on the second concentric circle from the outer circumference are arranged for temperature adjustment; and a cooling apparatus therefore is not provided.
In the conventional cooling roll, there was a limit of the heat amount per unit time that can be dissipated by the cooling water. This is because a cooling water channel surface area that is equal to or more than the surface area corresponding to the outer circumferential surface of the roll cannot be provided. For a constant sheet width, there was a limit of the foil thickness that could be obtained in an amorphous state.
Manufacturing methods (having an industrial production scale of, for example, 100 kg or more per charge) of an amorphous alloy strip having a sheet thickness that drastically exceeds the conventionally limited sheet thickness (25 to 30 μm for current commercial materials) are proposed in the Patent Literature 1, 2, and 3.
These methods are methods for continuously manufacturing an amorphous strip having a thickness exceeding the sheet thickness limit (the industrial production scale) of 30 μm of the conventional amorphous alloy foil. However, these methods have the problem that the equipment is large because multiple cooling rolls are used. Also, the operation is complex due to the complexity of repeatedly
Recently, a nozzle material having high durability for dispensing the alloy melt onto the outer circumferential surface of the cooling roll has been discovered. If the nozzle is used, casting is possible continuously for several hours. There is now a possibility that a thick amorphous alloy strip can be manufactured continuously using even a single cooling roll without being dependent on the alternating casting methods of the Patent Literatures 1 to 3.
Patent Literature 1: JP-B 5114241
Patent Literature 2: JP-B 5270295
Patent Literature 3: JP-B 5329915
Patent Literature 4: JP-A 2012-086232
An object of the invention is to provide a manufacturing apparatus of an amorphous alloy strip that makes it possible to manufacture a thick amorphous alloy strip on an industrial scale (100 kg or more per charge) by using a single cooling roll. The plate thickness of a current commercial thick amorphous alloy sheet has been limited to 30 μm or less. An object of the invention is to break through the limit and propose technology that continuously manufactures an amorphous sheet thicker than 30 μm.
To continuously manufacture an amorphous alloy strip having a large thickness by using a single cooling roll, the invention designates the structure of the cooling water flow channels of the cooling roll. Specifically, to obtain the amorphous alloy of the desired thickness, a structure of the cooling roll is provided in which the surface area of the cooling water channels inside the roll can be ensured.
According to the invention, a manufacturing apparatus of an amorphous alloy strip can be realized in which a thick amorphous alloy strip can be manufactured on an industrial scale. As a result, the production cost can be reduced; and smaller product applications are possible due to the space factor increase. Also, the core loss (the iron loss) is reduced, contributing to energy conservation. In the case where annealing is performed for the magnetic core used after stacking by winding, uniformity of the core internal temperature can be realized. This is because the heat flows more from the edge into the interior than between layers. Because the uniformity of the temperature can be realized, optimization of the annealing conditions is realized. Because the temperature of the entire core is at the same level within a narrow range, the optimal conditions are achieved at each portion of the core; and the optimal characteristics can be achieved easily.
Embodiments of the invention will now be described with reference to the drawings.
First, a first embodiment will be described.
In the manufacturing apparatus 1 of the amorphous alloy strip according to the embodiment as shown in
Operations of the manufacturing apparatus of the amorphous alloy strip configured as described above, i.e., the method for manufacturing the amorphous alloy strip according to the embodiment, will now be described.
First, by the melting furnace 14, an alloy that is used as the source material of the amorphous alloy strip S is melted; and the melt A is poured into the crucible 15. The melt A includes a total of 70 atomic % to 95 atomic % of at least one type of Fe, Co, or Ni and includes, other than the three types of ferromagnetic metal elements, 5 atomic % to 30 atomic % of at least one type of element of the semimetal B, Si, C, or P. Further, at least one type of Cr, V, Nb, Mo, W, Ta, Cu, or Sn in the range of 0.01 atomic % to 5 atomic % may be added to a portion of the ferromagnetic elements recited above. It goes without saying that, excluding inevitable impurities, the sum total of the content ratio of the elemental components must be 100%.
Among the added elements recited above, Cu is an essential element when making a so-called nanocrystalline material made of fine crystal grains in the range of several nanometers to 100 nanometers by crystallizing by annealing after making the amorphous foil. Also, other than a nanocrystalline material, the solitary addition of Cu in the (Fe, Co, Ni)—(B, Si, C, P) alloy in the range of 0.1 atomic % to 2.5 atomic % to realize the subdivision of the magnetic domains by partially promoting crystallization to improve the high frequency magnetic properties is within the scope of the invention.
Sn is effective when manufacturing an amorphous strip of an Fe-based alloy including a high content of Fe because Sn acts to suppress the crystallization by segregating in a thin layer of the surface of the foil. Although surface crystallization by annealing occurs easily and the magnetic properties such as the iron loss, the permeability, etc., degrade drastically for an alloy containing 82 atomic % or more of Fe, if 0.1 mass % to 1 mass % of Sn is included, the crystallization does not occur even after the annealing; and the original excellent soft magnetic properties are maintained. Further, a trace addition of S (sulfur) also acts similarly to Sn. An added amount of S in the range of 0.003 to 0.5 mass % is favorable.
The description of the function of the manufacturing apparatus 1 of the embodiment will now be continued. The drive unit (also used as the water drain unit) 13 causes the cooling roll 11 to rotate while the cooling water supply unit 12 causes cooling water W to flow through a flowing water path 21 inside the cooling roll 11. In this state, the melt A of the alloy poured into the crucible 15 from the melting furnace 14 is dispensed toward the outer circumferential surface 11a of the cooling roll 11 from the nozzle 16.
At this time, the melt A forms a puddle between the nozzle 16 and the outer circumferential surface 11a of the cooling roll 11. By the rotating cooling roll 11, the puddle that is cooled by the cooling roll 11 becomes a high viscosity supercooled melt at the vicinity contacting the outer circumferential surface 11a, is extracted in the rotation direction of the roll and quenched by the cooling roll 11, and is coagulated while having the supercooled melt structure. Thereby, the amorphous alloy strip S that has a strip configuration is formed. After the amorphous alloy strip S moves with the outer circumferential surface 11a of the cooling roll 11 to a prescribed position, the amorphous alloy strip S is guided in a direction away from the cooling roll 11 and is taken up. On the other hand, the heat that is conducted to the cooling roll 11 from the melt A moves to the cooling water flowing through the cooling roll interior and subsequently is dissipated outside the cooling roll 11 by the cooling water W flowing through the flowing water path 21.
The amorphous alloy strip manufacturing apparatus of the embodiment will now be described more specifically.
The side surfaces of the cooling roll 11 are covered respectively with covers 23a and 23b at both sides. The covers perform the role of supplying or receiving the cooling water to or from the through-holes without allowing the cooling water to escape to the outside. Although an example is shown in
As a modification of the first embodiment, by providing protrusions 26 having semicircular brim (eave) configurations such as that of
In
A second embodiment will now be described.
In
In the second embodiment, a flow rate adjustment valve 65 is provided in each of the flow channels 62a, 62b, and 62c branched from the main flow channel. By having the flow rate adjustment valve in each flow channel, the optimal flow rate distribution can be provided according to the width and thickness of the sheet to be cast. For example, in the case where the width and the thickness of a sheet are relatively small, it is sufficient to supply the cooling water with particular emphasis on the flow channel most proximal to the roll outer circumferential surface. As the thickness and the width of the sheet become larger, the water supply distribution for the flow channels on the second and third concentric circles also are increased. Thereby, even in the case where the thickness and the width of a sheet become larger, insufficient cooling capacity does not occur.
More specifically, when manufacturing an amorphous alloy strip having a plate thickness of 30 μm, it is sufficient for 90% or more of the cooling water to be supplied with particular emphasis on the flow channel most proximal to the roll outer circumference. As the thickness of the foil increases, the manufacture of an amorphous strip having thicknesses of 50 μm, 75 μm, and 100 μm is possible by increasing the flow rate of the cooling water flowing in the second and third flow channels. Substantially 100% of the heat that cannot be absorbed by the first flow channel is absorbed by the second and third flow channels. The portion that surrounds the cooling flow channels of the roll has no thermal resistance portions because the portion is one body and is not multiple rings or sleeves connected mechanically by shrink-fitting, etc.; therefore, the flow of the heat can utilize the original high thermal conductivity of the Cu alloy.
A modification of the second embodiment will now be described.
As shown in
In the manufacturing apparatus of the amorphous alloy strip of the embodiment in which the side surface through-holes are distributed, the heat dissipation effect is improved by providing an apparatus that cools the cooling water partway through the water supply path.
The diameter and width of the cooling roll used in the embodiment will now be described. These are dependent on the strength of the support mechanism such as the roll rotation axis, the bearings, etc., that support the weight of the roll. If the diameter is too large, the cooling power is improved; but the load of the support mechanism becomes large. Also, if the diameter is too small, the number of branches of the flow channel is insufficient; and the cooling power is insufficient. The diameter should be determined according to the desired thickness of a strip. For example, a diameter of 40 to 60 cm is sufficient for a sheet thickness of 30 to 60 μm; and a diameter of 60 to 80 cm is appropriate for a thickness of 60 to 90 μm. Similarly 80 to 100 cm is favorable for 90 to 110 μm.
For the width of the cooling roll as well, the cooling capacity increases as the width widens. However, compared to a conventional one-stage cooling roll, the effect of widening the width is small. In the case of one-stage cooling, by setting the wall thickness of the roll (the distance between the cooling water channels and the roll surface) to be large, the heat flows two-dimensionally and is conducted to the cooling water in a wide area. However, in the multistage cooling water channels (the water paths arranged on two or more concentric circles) proposed in the embodiment, the effect of widening the width of the roll is limited because much of the heat amount flows one-dimensionally (the temperature gradient is large in the radial direction of the roll). To put it strongly, it is sufficient for the width of the roll to somewhat exceed the width of the sheet.
The size of the through-hole will now be described. Basically, it is sufficient for the total surface area of the through-holes to be such that all of the heat moved from the melt to the cooling roll is sufficiently absorbed by the cooling water. The details are described below. The ease of making the holes, the processing cost, etc., are important points for the size of the through-hole. Also, the pressure that causes the cooling water to flow through must be in an appropriate range. Considering these points, it is favorable for the diameter of the through-hole to be 20 to 50 mm.
The nozzle (the opening for dispensing the alloy melt onto the cooling roll) used in the embodiment basically is a multi-slit nozzle. An example of a double nozzle is shown in
In other words, the surface temperature of the cooling roll in the initial casting is low. The Cu or Cu alloy roll that is used due to high thermal conductivity has poor affinity with Fe-based alloys. As shown by the equilibrium diagram of Cu—Fe alloys, the proportion that melts together is slight at low temperatures (including room temperature). Because of the mutual repulsion, the heat that is conducted by lattice vibrations also is not conducted easily. The heat transfer coefficient is low. If the heat transfer coefficient is low, coagulation does not occur no matter how much of the melt is supplied. In other words, the plate thickness does not become thick. The excessively-supplied melt merely becomes beads and scatters at the periphery. A stable puddle (the melt pool maintained between the nozzle and the roll) is not formed.
It is necessary to increase the roll temperature to increase the heat transfer coefficient. Therefore, the dispensing pressure is set to be low in the initial casting; and an amount of the melt that is commensurate with the heat transfer coefficient is supplied. Then, the puddle is stabilized; all of the heat that is emitted in the coagulation or high viscosity supercooled-liquification is absorbed by the roll; and the temperature of the roll increases. Thereby, the heat transfer coefficient increases; and a higher heat amount is absorbed. That is, the thickness of the foil can be thick.
To date, it has been said that a thick foil is not possible by a multi-slit nozzle method. This is because a melt that surpasses the thermal absorption capacity of the roll is supplied even though the temperature of the cooling roll is low. The overflowing melt scatters; and a stable puddle is not formed. Because the heat is not absorbed by the roll, the temperature of the roll never increases; and a thick foil is not formed. Although exceedingly common-sense, this appears to be generally not recognized.
The method illustrated in
When the sheet thickness becomes thicker than a constant, for example, 30 μm, the heat cannot be removed by only the flow channel of the outermost circumference. The heat that cannot be absorbed is absorbed by the water flowing through the second water path from the outer circumference. The water of the third flow channel is utilized when the sheet thickness is even thicker. Thus, it is sufficient to increase the flow channels according to the desired sheet thickness. The three levels of flow channels shown in
When implementing the embodiment, the arrangement of the through-holes, i.e., the distance from the roll outer circumferential surface, must be determined. However, although the wall thickness of the roll is important in the case where the cooling water channels are set only at the outermost circumference as conventionally, this cannot be designated in the embodiment. As long as a Cu or Cu alloy having a high thermal conductivity (the thermal conductivity being 70% or more of that of pure Cu) is used, if the sum total of the surface area of the through-holes piercing the side surface of the roll can absorb the heat amount incident on the roll per unit time, it is unnecessary to designate the wall thickness. The heat amount that is conducted to the cooling water can be estimated using the sum total of the surface area of the flow channels of the cooling water and the forced convective heat transfer coefficient of the water (1.2 to 5.8)×103 W/kg. The heat transfer coefficient recited above refers to “Illustrated Study of Heat Transfer Engineering,” Ohmsha, Ltd., Kaneyasu Nishikawa (Editor) and Naokata Kitayama (published Jan. 1, 1985).
In the case where an extremely thick amorphous alloy sheet is desired, the number of flow channels when viewed from the roll side surface may be four or more. When the number of flow channels becomes large, the diameter of the roll must be large. If the roll becomes too large, problems occur with the strength of the support mechanism such as the rotation axis, the bearings, etc., supporting the roll. In such a case, two rolls are arranged and used as in
If the cooling roll of the invention is used in combination with one of the Patent Literatures 1, 2, or 3, the productivity increases because the time until roll replacement lengthens. The work efficiency also is improved.
According to the invention, a manufacturing apparatus of an amorphous alloy strip can be realized in which a thick amorphous alloy strip can be manufactured at an industrial scale using a single roll.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-086139 | Apr 2014 | JP | national |
This is a continuation application of International Application PCT/JP2015/050687, filed on Jan. 13, 2015. This application also claims priority to Japanese Patent Application No. 2014-086139, filed on Apr. 18, 2014. The entire contents of each are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2015/050687 | Jan 2015 | US |
| Child | 15293559 | US |
