JP7007884B2 - Case and its manufacturing method - Google Patents

Description

The present invention relates to a case of a device that generates heat, such as a motor, a secondary battery, and a capacitor, and a method for manufacturing the same.

The motor device has a structure in which a magnet and an iron core wound with a dielectric coil are housed inside a cylindrical case, and when electricity is passed through the dielectric coil, heat is generated by the electric resistance of the dielectric coil. When a magnet is exposed to high heat, the magnetic force is reduced, so it is required to dissipate heat through the case. Further, the material of the case is preferably a non-magnetic material in order to contain the magnetic force, and an aluminum case has been used. The case of the secondary battery and the capacitor, which are repeatedly charged and discharged, also uses an aluminum case like the motor device in order to dissipate the heat generated during charging and discharging.

As the case material aluminum, pure aluminum having high thermal conductivity and excellent heat dissipation is used, and in cases where high strength is required, Al—Mn alloys such as A3003 alloy and Al—Mn—Cu alloys are used. It is used (see Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2015-125886 Japanese Unexamined Patent Publication No. 2014-185377

However, Al-Mn-based alloys and Al-Mn-Cu-based alloys have a problem that they have lower thermal conductivity and inferior heat dissipation than pure aluminum. Further, when the bottomed case is manufactured by impact molding or drawing molding on a disk-shaped material, it is required to have good moldability in addition to heat dissipation and strength.

In view of the background art described above, it is an object of the present invention to provide a case made of an aluminum alloy having excellent heat dissipation, strength and moldability, and a method for manufacturing the same.

That is, the present invention has the configurations described in the following [1] to [8].

[1] A bottomed case made of an aluminum alloy and having a bottom wall and a side wall integrally molded.
The aluminum alloy contains Si: 0.2% to 0.6%, Fe: 0.1% to 0.35%, Mg: 0.45% to 0.9%, and the balance is Al and unavoidable impurities. A case characterized by having a thermal conductivity of 180 W / (m · K) or more and an HV hardness of 55 or more.

[2] The aluminum alloy further contains at least one of Cu: 0.01% to 0.1%, Mn: 0.01% to 0.1%, and Cr: 0.01% to 0.1%. The case according to item 1 above, including seeds.

[3] The case according to item 1 or 2 above, wherein the aluminum alloy further contains at least one of Ti: 0.002% to 0.1% and B: 0.001% to 0.05%.

[4] Si: 0.2% to 0.6%, Fe: 0.1% to 0.35%, Mg: 0.45% to 0.9%, and the balance consists of Al and unavoidable impurities. A material for molding is produced by quenching an aluminum alloy after heat treatment, and impact molding is performed on the material heated to 120 ° C to 200 ° C to form a bottomed case in which the bottom wall and the side wall are integrated. A characteristic case manufacturing method.

[5] The method for manufacturing a case according to item 4 above, wherein the heat treatment is any one of hot rolling, hot extrusion, and solution treatment.

[6] The method for manufacturing a case according to item 4 or 5 above, wherein the material after quenching is subjected to artificial aging treatment.

[7] An in-vehicle battery in which any of the cases 1 to 3 in the preceding paragraph is used, which comprises a part of the structure of the vehicle body.

[8] A vehicle body characterized in that the vehicle-mounted battery according to item 7 above is used as a part of the structure of the vehicle body.

The case described in [1] above has a thermal conductivity of 180 W / (m · K) or more and an HV hardness of 55 or more, and therefore has high heat dissipation and strength. Further, the case is a bottomed case in which the bottom wall and the side wall are integrally molded, indicating that the moldability is good.

The case described in [2] above is particularly excellent in strength and / or moldability.

The case described in [3] above is particularly excellent in moldability.

According to the case manufacturing method described in the above [4], Mg ₂ Si particles are precipitated by heat treatment and subsequent quenching to prepare a material having good strength and moldability, and the prepared material is produced at 120 ° C. or higher. By applying impact molding by heating to a temperature of 200 ° C., it can be molded into a bottomed case without reducing the strength obtained by the quenching effect.

According to the case manufacturing method described in [5] above, any of the heat treatments of hot rolling, hot extrusion, and solution heat treatment can be performed to obtain the effect described in [4].

According to the case manufacturing method described in [6] above, a case having high strength can be manufactured by age hardening.

Since the in-vehicle battery described in [7] above has high strength in the case, it can be used as a part of the structure of the vehicle body.

Since the vehicle-mounted battery constitutes a part of the structure of the vehicle body according to the above [8], it is possible to reduce the number of members overlapping with the conventional vehicle body.

It is a perspective view which shows one Embodiment of the case of this invention. It is explanatory drawing which shows the impact molding method. It is a figure which shows the electric vehicle which used the in-vehicle battery as a part of the structure of a car body.

[Case]
FIG. 1 shows an embodiment of the case of the present invention.

Case 1 is a bottomed cylindrical body made of an aluminum alloy and integrally formed with a bottom wall 11 and a side wall 12, and the chemical composition, thermal conductivity, and HV hardness of the aluminum alloy are specified.
(Chemical composition of aluminum alloy)
In the chemical composition of the aluminum alloy of the material of Case 1, the significance of adding each element and the reason for limiting the content are as follows. The unit of the content of each element is mass%, which is abbreviated as "%".

Si coexists with Mg and precipitates Mg ₂ Si particles, which contributes to improving the strength of the alloy. If the Si content is less than 0.2%, the effect of precipitation strengthening is reduced, while if it exceeds 0.60%, the grain boundary precipitation of Si increases and grain boundary embrittlement is likely to occur, and the toughness of the alloy is increased. Decreases. Therefore, the Si content is 0.2% to 0.6%, and a particularly preferable Si content is 0.3% to 0.5%.

Fe crystallizes as an AlFeSi phase to prevent grain coarsening, reduces quenching sensitivity of the alloy, improves strength and toughness, and contributes to improvement of corrosion resistance. If the Fe content is less than 0.1%, the effect is small, while if it exceeds 0.35%, the thermal conductivity is lowered. Therefore, the Fe content is 0.1% to 0.35%, and a particularly preferable Fe content is 0.15% to 0.25%.

Mg coexists with Si and precipitates Mg ₂ Si particles, which contributes to the improvement of the strength of the alloy. When the Mg content is less than 0.45%, the effect of improving the strength is small, while when the Mg content exceeds 0.9%, the moldability and the thermal conductivity are lowered. Therefore, the Mg content is 0.45 to 0.9%, and a particularly preferable Mg content is 0.5% to 0.8%.

The aluminum alloy preferably further contains at least one of Cu, Mn, and Cr, if necessary.

Cu precipitates CuAl ₂ particles and contributes to improving the strength of the aluminum alloy. If the Cu content is less than 0.01%, the effect is small, while if the Cu content is more than 0.1%, the moldability is lowered. Therefore, the Cu content is 0.01% to 0.1%, and a particularly preferable Cu content is 0.05% to 0.08%.

Mn has the effect of precipitating Al—Mn-based particles and Al—Mn—Fe—Si-based particles to make the structure finer, promoting plastic flow during molding, and improving moldability. If the Mn content is less than 0.01%, the effect is small, while if the Mn content exceeds 0.1%, the thermal conductivity is lowered, which is not preferable. Therefore, the Mn content is 0.01% to 0.1%, and a particularly preferable Mn content is 0.03% to 0.06%.

Cr has the effect of precipitating Al—Cr-based particles and Al—Cr—Fe—Si-based particles to make the structure finer, promoting plastic flow during molding, and improving moldability. If the Cr content is less than 0.01%, the effect is small, while if the Cr content exceeds 0.1%, the thermal conductivity is lowered, which is not preferable. Therefore, the Cr content is 0.01% to 0.1%, and a particularly preferable Cr content is 0.03% to 0.06%.

The aluminum alloy preferably further contains at least one of Ti and Br, if necessary.

Ti and B have the effect of miniaturizing the ingot structure, and the miniaturization of the ingot structure enhances the moldability. In order to obtain such an effect, the Ti content is preferably 0.002% to 0.1%, more preferably 0.02% to 0.08%, and even more preferably 0.002% to 0.05%. The B content is preferably 0.0001% to 0.05%, more preferably 0.005% to 0.01%.

The rest of the aluminum alloy is Al and unavoidable impurities.
(Physical characteristics of aluminum alloy)
The aluminum alloy has a thermal conductivity of 180 W / (m · K) or more and is excellent in heat dissipation. A particularly preferable thermal conductivity is 200 W / (m · K) or more. Further, the HV hardness of the aluminum alloy is 55 or more, and the strength is excellent. A particularly preferable HV hardness is 58 or more. Further, the case 1 is a bottomed case in which the bottom wall 11 and the side wall 12 are integrally molded, indicating that the moldability is good.

Further, the tensile strength of the aluminum alloy constituting the case 1 is not limited, but is preferably 180 MPa or more, and even more preferably 200 MPa or more.
[Case manufacturing method]
The case 1 is manufactured by subjecting a material to impact molding.

In the impact molding, as shown in FIG. 2, the material 2 put into the cavity 22 of the die 21 is impacted by the punch 23, the thickness of the material 2 is reduced to form the bottom wall 11, and the material 2 is formed along the peripheral surface of the punch 23. This is a processing method in which the bottom wall 11 and the side wall 12 are integrally formed by stretching the material. According to impact molding, a bottomed case can be molded in one step. In impact molding, the side wall 12 is stretched while thinning the material 2, so that the material 2 for molding is thicker than the bottom wall 11 of the case 1 having the target shape. Deep drawing is a processing method for molding the side wall from a material with the same thickness as the bottom wall of the case, but since there is a limit to the height of the side wall that can be molded in one process, it is necessary to form a high side wall. Requires multiple steps and requires dies and punches for each step. On the other hand, in impact molding, since a side wall having a desired height can be obtained with a set of dies 21 and punch 23 in one process, the manufacturing efficiency is higher than that of deep drawing molding, and the manufacturing cost can be reduced.

In order to form a bottomed case by impact molding, it is necessary that the material has good fluidity and formability, but the molded case must have an HV hardness of 55 or more. be. In the present invention, the chemical composition of the aluminum alloy of the material is specified, and the temperature of the material to be subjected to impact molding is specified by performing heat treatment and quenching until the aluminum alloy is cast and processed into the shape of the material. Thereby, the moldability in impact molding is controlled, and the molded case has high heat dissipation and strength. The heat dissipation is obtained based on the chemical composition of the aluminum alloy.

The material 2 is a plate material having a thickness thicker than that of the bottom wall 11 of the case 1, and its planar shape is substantially the same as that of the bottom wall 11 of the case. For example, the material of the circular case is a circular plate, and the material of the square case is a square plate. The methods for producing a material with such a shape can be roughly divided into (A) a method of punching a large-sized plate with a thickness equivalent to the material into a planar shape of the material by fine blanking, and (B) a method of punching the planar shape of the material into a cross section. There is a method of slicing the bar material to the thickness of the material. The method for manufacturing a case of the present invention defines the temperature of a material to be subjected to heat treatment and quenching after the heat treatment in the process of producing a material for impact molding, and to be subjected to impact molding. The above-mentioned particles are precipitated by heat treatment during the material preparation process and subsequent quenching. That is, Mg ₂ Si particles and CuAl ₂ particles are precipitated to improve the strength, and Al-Mn-based particles, Al-Mn-Fe-Si-based particles, Al-Cr-based particles and Al-Cr-Fe-Si. Systematic particles Precipitate particles to improve strength and formability.

Hereinafter, two types of methods for producing the large-sized plate material (A) and two types of methods for producing the rod-shaped material (B) will be shown, and the heat treatment conditions in each method will be described.
(A-1)
The slab is semi-continuously cast, the slab is homogenized, then face-cut, hot-rolled, then quenched, and then cold-rolled to the thickness of the material 2. If necessary, the cold-rolled material is aged. A large-sized plate material produced by cold rolling is punched out by fine blanking to produce a material 2 having a required shape.

In the above steps, hot rolling corresponds to the heat treatment in the present invention. The hot rolling temperature (preheating temperature of the slab) is preferably 420 ° C to 520 ° C, particularly preferably 480 ° C to 500 ° C. Then, it is quenched from the above temperature.
(A-2)
The billet is semi-continuously cast, and after the billet is homogenized, it is face-cut, hot-extruded into a plate having the thickness of the material 2, and quenched. If necessary, the extruded plate material is aged. The large-sized plate material produced by the extrusion is punched out by fine blanking to produce a material 2 having a required shape.

In the above steps, hot extrusion corresponds to the heat treatment in the present invention. The hot extrusion temperature (preheating temperature of the billet) is preferably 420 ° C to 520 ° C, particularly preferably 450 ° C to 500 ° C. Then, it is quenched from the above temperature.
(B-1)
The billet is semi-continuously cast, the billet is homogenized, and then surface-cut, and a bar having a planar shape of the material 2 is hot-extruded and quenched. If necessary, the extruded bar is aged. The bar is sliced to the thickness of the material 2 to prepare the material 2.

In the above steps, hot extrusion corresponds to the heat treatment in the present invention. The hot extrusion temperature (preheating temperature of the billet) is preferably 420 ° C to 520 ° C, particularly preferably 450 ° C to 500 ° C. Then, it is quenched from the above temperature.
(B-2)
A bar having a plane shape of the material 2 as a cross section is continuously cast, the continuous cast material is homogenized, peeled, and sliced to the thickness of the material 2. This slice cutting material is solution-treated and then quenched. If necessary, it is aged after quenching. As a result, the material 2 is produced.

In the above step, the solution treatment of the sliced cutting material corresponds to the heat treatment in the present invention. The solution treatment temperature is preferably 480 ° C to 560 ° C, particularly preferably 510 ° C to 540 ° C. The solution treatment time is preferably 120 minutes to 360 minutes, particularly preferably 150 minutes to 240 minutes. Then, it is quenched from the above temperature.

In the steps (A-1), (A-2), (B-1), and (B-2), the aging treatment performed after quenching is an optional step. The aging treatment has the effect of increasing the strength and hardness due to the fine precipitation of aging precipitates such as Al-Cu and Mg ₂ Si. Preferred conditions for the aging treatment are 170 ° C. to 220 ° C. × 2 hours to 18 hours, and particularly preferable conditions are 180 ° C. to 200 ° C. × 4 hours to 10 hours. Further, the homogenization treatment for the cast material is also an arbitrary treatment, and it is preferable to perform the homogenization treatment at 490 ° C to 570 ° C. When the homogenization treatment temperature is within the above range, the effect of homogenizing the segregation during casting can be obtained, the transition metal element to be the recrystallization nucleus does not become coarse, and it is preferable from the viewpoint of preventing coarse recrystallization. If the homogenization treatment temperature is less than 490 ° C, it becomes difficult to obtain the effect of homogenizing the segregation during casting, while if it exceeds 570 ° C, the precipitation of the transition metal element becomes coarse and the effect of preventing coarse recrystallization becomes small. In particular, in the case of an aluminum alloy to which Fe and Mn are added, this range is preferable in order to obtain a higher effect. The homogenization treatment time is preferably 3 hours to 20 hours.

The material 2 produced by the methods (A-1), (A-2), (B-1), and (B-2) is heated to 120 ° C. to 200 ° C. after the surface is lubricated, and impact molding is performed at such a temperature. do. If the temperature of the material 2 is less than 120 ° C., the moldability is insufficient and molding by impact molding is difficult. On the other hand, if the temperature exceeds 200 ° C., the quenching effect is reduced or disappears. A particularly preferable temperature for the material 2 is 140 ° C to 180 ° C.

Further, the molding method of the material is not limited to the above-mentioned four methods. As long as heat treatment and subsequent quenching are performed during the process of producing a material having a required shape, the material may be produced by another method.

The use of the case of the present invention is not limited, but since it has excellent heat dissipation, it is suitable for the case of a device that generates heat such as a motor, a battery, and a capacitor. Further, since it has excellent strength, it can be used as a structure that supports a load or as a part of the structure. For example, as shown in FIG. 3, in the electric vehicle 3, it is necessary to mount a large number of batteries 30, and the batteries 30 are used as a part of the structure of the vehicle body. A large number of batteries 30 can be used as a structural material by assembling them so that the side walls of the case are in contact with each other and blocking them by winding a binding band or the like. The structural material has high strength in a direction parallel to the side wall of the case, and FIG. 3 shows a structure in which the side wall of the case of a large number of batteries 30 supports the load W of the floor panel 31. In addition, the dimensions of the structural material can be changed depending on the number and arrangement of batteries. As described above, by using the in-vehicle battery as a part of the structure of the vehicle body, it is possible to reduce the number of members overlapping with the conventional vehicle body.

[Production of material]
A slab was cast from an aluminum alloy having the chemical composition shown in each example of Table 1 and homogenized at 540 ° C. for 12 hours. Next, the surface of the slab was surface-cut and hot-rolled at 520 ° C. to form a thick plate having a thickness of 15 mm, and the thick plate was water-cooled and quenched. Then, the hardened thick plate is rolled to 3 mm by cold rolling to obtain a cold rolled plate, and this cold rolled plate is artificially aged at 180 ° C. for 6 hours, and a fine blanking mold having a diameter of 28 mm is used. Material 2 was produced by punching. Material 2 is a disk having a thickness of 3 mm and a diameter of 28 mm.
[Impact molding and moldability]
The prepared material 2 is subjected to bonde treatment as a lubricating film forming treatment, heated to the temperature shown in Table 1, impact-molded using the die 21 and punch 23 of FIG. 2, and placed in a bottomed case 1 (see FIG. 1). processed.

Impact molding aims to mold the bottom wall 11 having a thickness of 3 mm to 0.5 mm of the material 2, and the actual molding value can be formed thinner than the target value. Molding is possible, and the molding value does not reach the target value. It was evaluated that it could not be molded.
[Physical characteristics of molded products]
The physical characteristics of the molded case were measured by the following method.
(HV hardness)
The 12 side walls of the case 1 were cut and the HV hardness in the cross section was measured.
(Tensile strength)
A test piece was prepared from the side wall 12 of the case 1 and the tensile strength was measured.
(Thermal conductivity)
The thermal conductivity of the bottom wall 11 of Case 1 was measured by a laser flash method.

The results of these measurements are shown in Table 1.

From Table 1, it was confirmed that the cases of the examples had moldability, heat dissipation, and strength.

The case of the present invention can be used as a case for a device that generates heat, such as a motor, a secondary battery, and a capacitor.

1 ... Case 2 ... Material 3 ... Electric vehicle 11 ... Bottom wall 12 ... Side wall 21 ... Dice 22 ... Cavity 23 ... Punch 30 ... Battery 31 ... Floor panel

Claims (6)

A bottomed case made of aluminum alloy with the bottom wall and side walls integrally molded.
The aluminum alloy contains Si: 0.2% to 0.6%, Fe: 0.1% to 0.35%, Mg: 0.45% to 0.9%, and the balance is Al and unavoidable impurities. A case characterized by having a thermal conductivity of 180 W / (m · K) or more and an HV hardness of 55 or more. The aluminum alloy further contains at least one of Cu: 0.01% to 0.1%, Mn: 0.01% to 0.1%, and Cr: 0.01% to 0.1%. The case according to claim 1. The case according to claim 1 or 2, wherein the aluminum alloy further contains at least one of Ti: 0.002% to 0.1% and B: 0.001% to 0.05%. An aluminum alloy containing Si: 0.2% to 0.6%, Fe: 0.1% to 0.35%, Mg: 0.45% to 0.9%, and the balance is Al and unavoidable impurities. After heat treatment by hot rolling, hot extrusion, or solution treatment, quenching was performed at 170 ° C to 200 ° C to prepare a material for molding, and the material was heated to 120 ° C to 200 ° C. A case characterized in that the material is impact-molded to integrate the bottom wall and the side wall, and a bottomed case having a thermal conductivity of 180 W / (m · K) or more and an HV hardness of 55 or more is molded. Manufacturing method. An in-vehicle battery in which the case according to any one of claims 1 to 3 is used, which comprises a part of a structure of a vehicle body. A vehicle body according to claim 5 , wherein the vehicle-mounted battery is used as a part of the structure of the vehicle body.

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