A method for preparing a battery square shell

Abstract

The invention provides a shaping preparation method for a battery square shell, which is characterized in that it comprises the following steps: raw material preparation: configuring a rod-shaped aluminum alloy blank; blank pretreatment: removing the oxide scale from the blank and then preheating it; hot extrusion: hot extruding the blank to form a round cake; cold extrusion: cold extruding to form a round tube of a predetermined length; cold drawing: performing one or more cold drawing to stretch the round tube into an elliptical tube; shaping: shaping the elliptical tube into a square tube.

Description

Technical Field

[0001] The invention relates to a shaping and preparation method for a battery square shell. Background Art

[0002] At present, there are two production processes for aluminum alloy battery square tubes. One is a process based on hot extrusion, cold extrusion and cold bending. The minimum wall thickness of hot pressed or cold extruded square tubes can be 0.45mm, and different wall thicknesses can be achieved. The other is a process based on welding, and the minimum wall thickness can be 0.3mm, but it can only be made into a uniform wall thickness.

[0003] A Chinese invention patent application with the application publication date of CN111740041A and the application publication date of October 2, 2020 discloses a method for manufacturing a battery shell, comprising the following steps: S1, hot extrusion or cold extrusion of a metal blank into a tubular prefabricated metal part; S2, stretching the prefabricated metal part along the axial direction of the prefabricated metal part; S3, cutting a section of the prefabricated metal part after stretching along the axial direction as a battery shell. It is formed by a single hot extrusion or cold extrusion. A single hot extrusion or cold extrusion of a thin-walled square tube below 0.5 mm is extremely difficult to form, and is prone to defects such as ripples and unstable cross-sectional dimensions.

[0004] A Chinese invention application with application publication number CN110038914A and application publication date July 23, 2019 discloses a round tube extrusion die, which is characterized in that it includes a matching punch and a die; the punch is provided with a die body, a foreman, a punch baffle and a diverter bridge, and the punch is provided with a diverter port between the die body and the diverter bridge, the punch baffle and the diverter bridge are both connected to the die body, the foreman is connected to the punch baffle, and a pier chamfer is formed between the diverter bridge and the die body; the die is provided with a working belt, a die baffle and the mold wall, and the female mold forms a tapered slope between the working belt and the female mold baffle, and a receiving area is formed between the female mold baffle and the mold wall; in the mold closing state, the female mold baffle and the mold wall cooperate with the mold body to form a large-radius bowl-shaped welding chamber; and the working belt is arranged adjacent to the foreman and there is a gap connecting the mold core of the female mold, and the male mold baffle, the female mold baffle and the tapered slope jointly form a tapered secondary welding chamber, and the tapered secondary welding chamber is connected to the large-radius bowl-shaped welding chamber. This application is formed by hot extrusion. However, the square tube formed by hot extrusion has the problem of insufficient strength and hardness. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a method for preparing a battery square shell with a reasonable structural design.

[0006] The technical solution adopted by the embodiment of the present invention to solve the above problem is: a method for shaping and preparing a square battery shell, characterized in that it includes the following steps:

[0007] Raw material preparation: prepare rod-shaped aluminum alloy billet;

[0008] Pretreatment of billet: After descaling the billet, preheat it;

[0009] Hot extrusion: hot extrusion of the billet into a round tube;

[0010] Cold extrusion: Cold extrusion forms round tubes of predetermined length;

[0011] Cold drawing: one or more cold drawing processes are performed to stretch the round tube into an oval tube;

[0012] Shaping: Shape the oval tube into a square tube.

[0013] The components contained in the aluminum alloy billet described in the embodiment of the present invention and the mass percentage of each component are: manganese: 1.2% to 1.6%; magnesium: ≤0.02%; zinc: ≤0.02%; silicon ≤0.6%; iron ≤0.7%; copper: 0.05% to 0.2%; zirconium ≥0.001%; ​​impurities: ≤0.15%; aluminum: balance.

[0014] The total mass percentage of magnesium and zinc in the embodiment of the present invention is ≤0.03%.

[0015] In the embodiment of the present invention, the blank is pretreated to remove the oxide scale, and the preheating temperature is 450-520°C.

[0016] During hot extrusion in the embodiment of the present invention, the extrusion coefficient is 50-150, and the ratio of the maximum outer diameter of the circular tube to the diameter of the blank is less than or equal to 1.5.

[0017] The circular tube described in the embodiment of the present invention has uniform wall thickness or unequal wall thickness; when the circular tube has uniform wall thickness, the minimum wall thickness of the square tube made therefrom is greater than or equal to 0.2 mm; when the circular tube has unequal wall thickness, the wall thickness of one side of the square tube made therefrom is 0.8 to 1.5 mm, and the wall thickness of the other three sides is 0.2 to 0.5 mm.

[0018] After the hot extrusion of the embodiment of the present invention is completed, aging strengthening is performed for more than 6 hours, and the temperature is set at 140-180°C.

[0019] During the cold extrusion described in the embodiment of the present invention, a stearic acid-based lubricant is mixed on the surface of the round cake material, and the round cake material coated with the lubricant is extruded at high pressure by a cold extrusion punch to form a cold extruded round tube with a length of 250-600 mm.

[0020] The embodiment of the present invention is equipped with a cold drawing device for cold drawing, and the cold drawing device includes:

[0021] frame;

[0022] a supporting unit, which is disposed on the frame and includes a forced support member and a power unit; the power unit is connected to the forced support member and is configured to drive the forced support member to rotate; the forced support member includes a first supporting surface and a second supporting surface, and the distance from the first supporting surface to the rotation center of the forced support member is smaller than the distance from the second supporting surface to the rotation center of the forced support member; and

[0023] The supporting member is in strip shape and cooperates with the forced supporting member.

[0024] In the embodiment of the present invention, the first supporting surface has a first vertex, the second supporting surface has a second vertex, and the distance from the outer surface of the forced support member to its rotation center gradually increases from the first vertex to the second vertex; the ratio of the distance from the second vertex to the rotation center of the forced support member to the distance from the first vertex to the rotation center of the forced support member is less than or equal to 2.

[0025] The cold drawing device described in the embodiment of the present invention is provided with multiple groups to perform multiple cold drawing on the round tube.

[0026] The embodiment of the present invention configures a shaping device for shaping, and the shaping device includes:

[0027] Bracket;

[0028] A pipe support unit, which is disposed on the bracket and includes a cam, a driving unit and a pipe support member, wherein the driving unit is connected to the cam, the cam cooperates with the pipe support member, the cam includes a first abutting surface and a second abutting surface, and the distance from the first abutting surface to the rotation center of the cam is smaller than the distance from the second abutting surface to the rotation center of the cam; and

[0029] The tube pressing unit includes a shaping unit and a control unit, wherein the control unit is connected to the shaping unit, and the shaping unit is arranged on the outside of the tube support member and is configured to extrude the tube from the outside of the tube.

[0030] The shaping unit described in the embodiment of the present invention includes two groups of first shaping members and two groups of second shaping members. The two groups of the first shaping members are arranged on both sides of the width direction of the pipe, and the two groups of the second shaping members are arranged on both sides of the height direction of the pipe.

[0031] In the embodiment of the present invention, the overpressure of the first shaping member and the second shaping member is between 0.02 and 0.06 times the height of the square tube.

[0032] The support tube members of the embodiment of the present invention are provided with two groups, which are respectively provided on both sides of the cam, and the side of the support tube members is provided with a first concave surface, and the two sides of the height direction of the two groups of support tube members respectively form a second concave surface.

[0033] In the embodiment of the present invention, the first shaping member is provided with a first convex portion corresponding to the first inner concave surface, and the second shaping member is provided with a second convex portion corresponding to the second inner concave surface.

[0034] In this embodiment of the present invention, the inner concave size of the first inner concave surface is less than or equal to 2% to 5% of the distance between the end faces of the two groups of support pipes in the width direction; the inner concave size of the second inner concave surface is less than or equal to 3% to 6% of the distance between the end faces of the two groups of support pipes in the height direction.

[0035] Compared with the prior art, the present invention has one or more of the following advantages or effects: the shaping preparation method of the battery square shell of the present invention first extrudes the special aluminum alloy billet into round tubes with unequal wall thickness or equal wall thickness by hot extrusion or cold extrusion, and then the round square tubes with unequal wall thickness or equal wall thickness are made into square tubes with unequal wall thickness or equal wall thickness by cold drawing; the formability and strength of the aluminum material can be improved by changing the trace element ratio of the aluminum material; the problem of single hot extrusion or cold extrusion thin-walled square tubes being difficult to form is solved, and single hot extrusion or cold extrusion thin-walled square tubes with a thickness of less than 0.5 mm are difficult to form and are prone to wavy lines, unstable cross-sectional dimensions and other defects; the problem of the difficulty in forming tubes with unequal wall thicknesses is solved, and tubes with equal wall thickness can be made thinner; the problem of low strength and hardness of square tubes after hot extrusion is solved, and the square tubes manufactured by the present method can significantly improve The strength and hardness of the high-pressure material are improved; the manufacturing accuracy of the square tube is improved; cold drawing: in the process of gradually cold drawing from a circle to an ellipse along the diameter direction, the size in the short diameter direction is shortened, and the deformation amount of cold drawing is controlled by continuously adjusting the process to allow the material to flow toward the long diameter direction to achieve the target size of each process; multiple cold drawing can be performed to prevent the parts from cracking due to one-time cold drawing; shaping process: the final size of the part is achieved through cold drawing and shape shaping, and the part is shaped into a square cross-section through the shape overpressure profiling tooling to finally achieve the target shape and size; compared with cold bending forming, the problem of difficult forming of square tubes with unequal wall thicknesses is solved. The material of the present invention is formed by drawing along the diameter direction of the tube body, and the material deformation is mainly small deformation plastic deformation; the cold drawing in the present invention also reduces the head and tail waste in the cold drawing process, improves the accuracy, can achieve unequal wall thickness, and improves the material utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 1 is a diagram of the forming process of square tubes with unequal wall thicknesses in an embodiment of the present invention.

[0038] Figure 2 It is a forming process diagram of two cold drawing and one shaping in an embodiment of the present invention.

[0039] Figure 3 Schematic diagram of the three-dimensional structure of the cold drawing device in the embodiment of the present invention Figure 1 .

[0040] Figure 4 Schematic diagram of the three-dimensional structure of the cold drawing device in the embodiment of the present invention Figure 2 .

[0041] Figure 5 yes Figure 4 Enlarged view of point A in the middle.

[0042] Figure 6 It is a schematic diagram of the main structure of the forced support.

[0043] Figure 7 It is a schematic diagram of the forced support member being pushed and rotated by the first connecting rod and the second connecting rod.

[0044] Figure 8 It is a schematic diagram of the three-dimensional structure of the shaping device in an embodiment of the present invention.

[0045] Fig. 9 It is a schematic diagram of the main structure of the shaping device in an embodiment of the present invention.

[0046] Fig.10 yes Fig. 9 Enlarged view of point B in the middle.

[0047] Fig.11 It is a three-dimensional structural schematic diagram of the shaping device without part of the tube pressing unit.

[0048] Fig.12 yes Fig.11 Enlarged view of point C in the middle.

[0049] Fig.13 It is a schematic diagram of the main structure of the cam.

[0050] Fig.14 It is a schematic diagram of the coordination between the pipe support unit and the pipe compression unit. DETAILED DESCRIPTION

[0051] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described below. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood. The directions such as "axial direction", "above", "below", etc. in the following text are all for the purpose of more clearly indicating the structural position relationship and are not limitations of the present invention. In the present invention, the "vertical", "horizontal" and "parallel" are defined as: including the situation of ±10% based on the standard definition. For example, vertical usually refers to an angle of 90 degrees relative to the reference line, but in the present invention, vertical refers to a situation within 80 to 100 degrees.

[0052] See also Figures 1 to 14 The method for preparing the battery square shell of this embodiment comprises the following steps:

[0053] Raw material preparation: prepare rod-shaped aluminum alloy billet;

[0054] Pretreatment of billet: After descaling the billet, preheat it;

[0055] Hot extrusion: hot extrusion of the blank into a round cake;

[0056] Cold extrusion: Cold extrusion forms round tubes of predetermined length;

[0057] Cold drawing: one or more cold drawing processes are performed to stretch the round tube into an oval tube;

[0058] Shaping: Shape the oval tube into a square tube.

[0059] The components contained in the aluminum alloy billet described in this embodiment and the mass percentage of each component are: manganese: 1.2%~1.6%; magnesium: ≤0.02%; zinc: ≤0.02%; silicon: ≤0.6%; iron: ≤0.7%; copper: 0.05%~0.2%; zirconium ≥0.001%; ​​impurities: ≤0.15%; aluminum: balance.

[0060] In a specific embodiment, the aluminum alloy billet comprises the following components and the mass percentage of each component: manganese: 1.2%; magnesium: 0.02%; zinc: 0.01%; silicon: 0.6%; iron: 0.7%; copper: 0.1%; zirconium ≥ 0.001%; ​​aluminum: balance.

[0061] In a specific embodiment, the aluminum alloy billet contains the following components and the mass percentage of each component: manganese: 1.6%; magnesium: 0.01%; zinc: 0.02%; silicon: 0.4%; iron: 0.3%; copper: 0.05%; zirconium: 0.0013%; impurities: 0.15%; aluminum: balance.

[0062] In a specific embodiment, the aluminum alloy billet contains the following components and the mass percentage of each component: manganese: 1.3%; magnesium: 0.01%; zinc: 0.01%; silicon: 0.6%; iron: 0.5%; copper: 0.03%; zirconium: 0.0012%; impurities: 0.1%; aluminum: balance.

[0063] In this embodiment, the impurities include sulfide and carbon impurities.

[0064] In the above embodiment, iron is added, and the iron element can dissolve in MnAl6 to form (FeMn)Al6 compounds, thereby reducing the solubility of manganese in aluminum and significantly improving the mechanical properties of the alloy; the copper element is added, which has a certain solid solution strengthening effect and can generate CuAl2, which has an obvious aging strengthening effect, but copper can reduce the corrosion resistance of the alloy, so it should be controlled to ≤0.05%; the silicon element is added, which can form a complex ternary phase (Al12Mn3Si2) with manganese, and can also reduce the solubility of manganese in aluminum and improve the mechanical properties of the alloy material.

[0065] In the above embodiment, adding a trace amount of zirconium element is conducive to the formation of Al3Zr compounds, hindering the recrystallization process, and refining the recrystallized grains. When the grain size decreases, the dislocation density increases, thereby enhancing the material's resistance to deformation (improving mechanical properties); the material's thermal expansion coefficient decreases, thereby reducing the thermal stress during processing (improving the material's cutting performance); grain boundaries are places where stress concentrates. When the grain size decreases, the number of grain boundaries decreases, the degree of stress concentration decreases, thereby reducing stress and fatigue.

[0066] The total mass percentage of magnesium and zinc in this embodiment is ≤0.03%. For example, the total mass percentage of magnesium is controlled at 0.01%, and the total mass percentage of zinc is controlled at 0.01%, so that the total mass percentage of magnesium and zinc is ≤0.03%. For another example, the total mass percentage of zinc is controlled at 0.01%, and the total mass percentage of magnesium is controlled at 0.02%, so that the total mass percentage of magnesium and zinc is ≤0.03%. For another example, the total mass percentage of zinc is controlled at 0.01%, and the total mass percentage of magnesium is controlled at 0.015%, so that the total mass percentage of magnesium and zinc is ≤0.03%. By controlling the total mass percentage of magnesium and zinc to ≤0.03%, the strength of the material can be improved.

[0067] In the present embodiment, the preheating temperature of the blank is 450-520°C after descaling. Specifically, the preheating and descaling are performed by an infrared heating furnace. The preheating process can ensure that the temperature during the hot extrusion process is as stable as possible above the recrystallization temperature, so that the material has good fluidity and the thickness and shape size of the extruded round tube are uniform.

[0068] During hot extrusion in this embodiment, a round tube is formed by a hot extruder under high pressure, and an extrusion coefficient (rod cross-sectional area / tube cross-sectional area) is 50-150, and the ratio of the maximum outer diameter of the round tube to the diameter of the blank is less than or equal to 1.5.

[0069] The circular tubes described in this embodiment have equal wall thickness or unequal wall thickness; when the circular tubes have equal wall thickness, the minimum wall thickness of the square tubes made therefrom is greater than or equal to 0.2 mm; when the circular tubes have unequal wall thickness, the wall thickness of one side of the square tubes made therefrom is 0.8 to 1.5 mm, and the wall thickness of the other three sides is 0.2 to 0.5 mm.

[0070] After the hot extrusion of this embodiment is completed, aging strengthening is performed for more than 6 hours, and the temperature is set to 140-180° C. After aging strengthening, the tensile strength and yield strength of the hot extruded material can be increased by at least 10%.

[0071] During the cold extrusion described in this embodiment, a stearic acid-based lubricant is mixed on the surface of the circular tube, and the circular tube coated with the lubricant is extruded at high pressure by a cold extrusion punch to form a cold extruded circular tube with a length of 250-600 mm. The stearic acid-based lubricant is a solid lubricant that can be evenly coated on the surface of the blank, and can effectively improve the lubrication stability during the forming process of the circular tube, achieving the goal of uniform thickness and shape size during the forming process.

[0072] This embodiment configures a cold drawing device to perform cold drawing, and the cold drawing device includes a frame 1, a support unit 2 and a support member 3.

[0073] The support unit 2 in this embodiment is arranged on the frame 1, and includes a forced support member 21 and a power unit 22; the power unit 22 is connected to the forced support member 21, and is configured to drive the forced support member 21 to rotate; the forced support member 21 includes a first supporting surface 211 and a second supporting surface 212, and the distance from the first supporting surface 211 to the rotation center O of the forced support member 21 is smaller than the distance from the second supporting surface 212 to the rotation center O of the forced support member 21.

[0074] The supporting member 3 in this embodiment is in a strip shape and cooperates with the forced supporting member 21 .

[0075] When in use, the pipe 10 (round pipe or elliptical pipe) is sleeved on the support unit 2 of the cold drawing device, and the support member 3 is arranged between the inner wall of the pipe and the forced support member 21, and at this time the first support surface 211 cooperates with the support member 3; the forced support member 21 is rotated by the power unit 22, and the forced support member 21 gradually stretches the pipe 10 during the rotation process, deforming it, and finally making the second support surface 212 against the support member 3, thereby completing the stretching of the cross-sectional direction of the pipe 10. In order to obtain the target size, multiple groups of cold drawing devices can be set, and through multiple cold drawing, the assembly makes the pipe close to the target size. Compared with other processes in the prior art, the forced support member 21 used to stretch the pipe 10 in cooperation with the support member 3 will not scratch the surface of the pipe 10 and will not easily damage the pipe.

[0076] After the pipe 10 is arranged outside the support 3, it is inserted into the pipe 10. It is replaceable, so the support 3 can be replaced according to different size requirements. When multiple cold drawing is required, only the support 3 needs to be replaced when different cold drawing processes are required, which can improve equipment utilization and reduce costs.

[0077] In this embodiment, the first supporting surface 211 and the second supporting surface 212 are connected by an arc transition, so when the force-supporting member 21 rotates, it can smoothly push the supporting member 3 to ensure the quality of cold drawing.

[0078] In this embodiment, the first support surface 211 and the second support surface 212 are both arc surfaces. The curvature radius of the second support surface 212 is smaller than the curvature radius of the first support surface 211, so that the second support surface 212 can better support the support member 3.

[0079] In this embodiment, the first supporting surface 211 has a first vertex 2111, the second supporting surface 212 has a second vertex 2121, and the distance from the outer surface of the force-supporting member 21 to its rotation center O gradually increases from the first vertex 2111 to the second vertex 2121.

[0080] In this embodiment, the ratio of the distance a from the second vertex 2121 to the rotation center O of the forced support 21 to the distance b from the first vertex 2111 to the rotation center O of the forced support 21 is less than or equal to 2 and greater than 1.4, so as to control the amount of cold drawing at one time, avoid excessive cold drawing at one time, resulting in uneven wall thickness or material rupture, and at the same time ensure the efficiency of cold drawing.

[0081] The power unit 22 of this embodiment includes a cylinder 221, a first connecting rod 222 and a second connecting rod 223. The force support member 21 is hinged to the first connecting rod 222 and the second connecting rod 223 respectively. Figure 7The state of the forced support member 21 changes as it rotates under the control of the first connecting rod 222 and the second connecting rod 223. When the cylinder 221 controls the first connecting rod 222 and the second connecting rod 223 to move in opposite directions (the first connecting rod 222 and the second connecting rod 223 are in opposite directions along the length direction of the pipe), the forced support member 21 rotates. In other embodiments, the forced support member 21 can also be controlled to rotate by a motor or a cylinder, which will not be described in detail here.

[0082] The force-supporting member 21 of this embodiment has an initial position and a supporting tube position. In the initial position, the first supporting surface 211 corresponds to the supporting member 3 . In the supporting tube position, the second supporting surface 212 corresponds to the supporting member 3 .

[0083] The force-supporting member 21 of this embodiment has an internal passage, and the first connecting rod 222 and the second connecting rod 223 pass through the internal passages respectively, so as to avoid the first connecting rod 222 and the second connecting rod 223 being outside the force-supporting member 21 and affecting the processing of the pipe 10 .

[0084] The outer circumference of the force-supporting member 21 of the present embodiment is elliptical, and has two groups of first supporting surfaces 211 and two groups of second supporting surfaces 212 .

[0085] In this embodiment, the ratio of the distance between the rotation centers O of two adjacent force-staying members 21 to the length of the major axis of the force-staying member 21 (i.e., the distance between the two second vertices) is greater than 2 and less than 5. Therefore, the pipe 10 can have uniform force in the length direction to ensure its dimensional accuracy.

[0086] In this embodiment, a plurality of force-supporting members 21 are provided, and the plurality of force-supporting members 21 are controlled by a power unit 22 to simplify the structure.

[0087] The cold drawing device described in this embodiment is provided with multiple groups to perform multiple cold drawing on the circular tube. If two cold drawing are performed, the cold drawing deformation amount can be adjusted accordingly according to the product cross-sectional height during the first cold drawing, and the deformation amount is controlled to be ≤35%, and during the second cold drawing, the cold drawing deformation amount should be ≤30%.

[0088] This embodiment is equipped with a shaping device for shaping, and the shaping device includes a support 4, a tube supporting unit 5 and a tube pressing unit 6.

[0089] The pipe support unit 5 in this embodiment is arranged on the bracket 4, and includes a cam 51, a driving unit 52 and a pipe support member 53. The driving unit 52 is connected to the cam 51, and the cam 51 cooperates with the pipe support member 53. The cam 51 includes a first abutting surface 511 and a second abutting surface 512. The distance from the first abutting surface 511 to the rotation center O of the cam 51 is smaller than the distance from the second abutting surface 512 to the rotation center O of the cam 51. When in use, the pipe 10 (circular pipe or elliptical pipe) is sleeved outside the pipe support unit 5. When the cam 51 rotates, the first abutting surface 511 gradually switches to cooperate with the pipe support member 53 to cooperate with the second abutting surface 512 to support the pipe 10.

[0090] The tube pressing unit 6 in this embodiment includes a shaping unit 61 and a control unit 62. The control unit 62 is connected to the shaping unit 61. The shaping unit 61 is arranged on the outside of the tube support member 53 and is configured to extrude the tube 10 from the outside of the tube 10 to shape the tube 10 from the outside of the tube 10 to ensure the dimensional accuracy of the tube 10.

[0091] The shaping unit 61 of this embodiment includes two groups of first shaping members 611 and two groups of second shaping members 612. The two groups of the first shaping members 611 are arranged on both sides of the width direction of the pipe 10, and the two groups of the second shaping members 612 are arranged on both sides of the height direction of the pipe 10, so as to shape the pipe 10 from four directions of the pipe 10. The two groups of the first shaping members 611 and the two groups of the second shaping members 612 are respectively controlled by electric cylinders or pneumatic cylinders.

[0092] The overpressure of the first shaping member 611 is 2% to 6% of the width of the tube 10. The overpressure of the second shaping member 612 is 2% to 6% of the height of the tube 10. This can compensate for the rebound of the wall of the tube 10 after shaping.

[0093] In this embodiment, two groups of pipe support members 53 are provided, and the two groups of pipe support members 53 are respectively provided on both sides of the cam 51. The side of the pipe support member 53 is provided with a first inner concave surface 531, and the two sides of the height direction of the two groups of pipe support members 53 are respectively formed with a second inner concave surface 532. The provision of the first inner concave surface 531 and the second inner concave surface 532 can effectively compensate for the rebound of the material and have a buffering effect on the material to avoid directly piercing the pipe 10.

[0094] In this embodiment, the first shaping member 611 is provided with a first convex portion 6111 corresponding to the first inner concave surface 531, and the first convex portion 6111 has an outer convex arc surface. The second shaping member 612 is provided with a second convex portion 6121 corresponding to the second inner concave surface 532, and the second convex portion 6121 has an outer convex arc surface.

[0095] In this embodiment, the inner concave dimension a of the first inner concave surface 531 is less than or equal to 2% to 5% of the distance dimension b between the end surfaces of the two groups of the supporting tube members 53 in the width direction.

[0096] In this embodiment, the inner concave dimension c of the second inner concave surface 532 is less than or equal to 3% to 6% of the distance dimension d between the end surfaces of the two groups of the supporting tube members 53 in the height direction.

[0097] The driving unit 52 described in this embodiment includes a cylinder 521, a first connecting rod 522 and a second connecting rod 523. The cam 51 is hinged on the first connecting rod 522 and the second connecting rod 523 respectively. When the cylinder 521 controls the first connecting rod 522 and the second connecting rod 523 to move in opposite directions respectively, the cam 51 rotates to switch between the first pushing surface 511 and the second pushing surface 512.

[0098] The cam 51 of this embodiment has an internal passage, and the first connecting rod 522 and the second connecting rod 523 pass through the internal passages respectively, so as to avoid the first connecting rod 522 and the second connecting rod 523 being outside the cam 51 and affecting the processing of the pipe 10 .

[0099] The outer periphery of the cam 51 in this embodiment is elliptical.

[0100] In this embodiment, the ratio of the distance between the rotation centers O of two adjacent cams 51 to the size of the major axis of the cam 51 is greater than 2 and less than 5.

[0101] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for shaping and preparing a square battery case, characterized in that: The following steps are involved: Raw material preparation: Prepare rod-shaped aluminum alloy billet; Pretreatment of billet: After descaling the billet, preheat it; Hot extrusion: hot extrusion of the blank into a round cake; Cold extrusion: Cold extrusion forms round tubes of predetermined length; Cold drawing: one or more cold drawing processes are performed to stretch the round tube into an oval tube; Shaping: shaping oval tubes into square tubes; A shaping device is configured to perform shaping, the shaping device comprising: Bracket; A pipe support unit, which is disposed on the bracket and includes a cam, a driving unit and a pipe support member, wherein the driving unit is connected to the cam, the cam cooperates with the pipe support member, the cam includes a first abutting surface and a second abutting surface, and the distance from the first abutting surface to the rotation center of the cam is smaller than the distance from the second abutting surface to the rotation center of the cam; and A tube pressing unit, the tube pressing unit comprising a shaping unit and a control unit, the control unit being connected to the shaping unit, the shaping unit being arranged on the outside of the tube supporting member and configured to squeeze the tube from the outside of the tube; The circular tube has a uniform wall thickness or a non-uniform wall thickness; when the circular tube has a uniform wall thickness, the minimum wall thickness of the square tube made from it is greater than or equal to 0.2 mm; when the circular tube has a non-uniform wall thickness, the wall thickness of one side of the square tube made from it is 0.8-1.5 mm, and the wall thickness of the other three sides is 0.2-0.5 mm; The shaping unit comprises two groups of first shaping members and two groups of second shaping members, the two groups of the first shaping members are arranged on both sides of the width direction of the pipe, and the two groups of the second shaping members are arranged on both sides of the height direction of the pipe; The overpressure of the first shaping member and the second shaping member is between 0.02 and 0.06 times the height of the square tube.

2. The method for shaping and preparing a square battery case according to claim 1, characterized in that: The aluminum alloy blank contains the following components and the mass percentage of each component: manganese: 1.2% to 1.6%; Magnesium: ≤0.02%; Zinc: ≤0.02%; Silicon ≤0.6%; Iron ≤0.7%; Copper: 0.05%~0.2%; Zirconium ≥0.001%; ​​Impurities: ≤0.15%; Aluminum: balance.

3. The method for shaping and preparing a square battery case according to claim 2, characterized in that: The total mass percentage of magnesium and zinc is ≤0.03%.

4. The method for shaping and preparing a square battery case according to claim 1, characterized in that: During the pretreatment of the blank, the oxide scale is removed and the preheating temperature is 450~520℃.

5. The method for shaping and preparing a square battery case according to claim 1, characterized in that: During hot extrusion, the extrusion coefficient is 50-150, and the ratio of the maximum outer diameter of the circular tube to the diameter of the blank is less than or equal to 1.

5.

6. The method for shaping and preparing a square battery case according to claim 1 or 5, characterized in that: After hot extrusion, aging strengthening is carried out for more than 6 hours, and the temperature is set at 140~180℃.

7. The method for shaping and preparing a square battery case according to claim 1, characterized in that: During the cold extrusion, a stearic acid-based lubricant is mixed on the surface of the round cake material, and the round cake material coated with the lubricant is extruded at high pressure by a cold extrusion punch to form a cold extruded round tube with a length of 250-600 mm.

8. The method for shaping and preparing a square battery case according to claim 1, characterized in that: A cold drawing device is configured to perform cold drawing, the cold drawing device comprising: frame; a supporting unit, which is disposed on the frame and includes a forced support member and a power unit; the power unit is connected to the forced support member and is configured to drive the forced support member to rotate; the forced support member includes a first supporting surface and a second supporting surface, and the distance from the first supporting surface to the rotation center of the forced support member is smaller than the distance from the second supporting surface to the rotation center of the forced support member; and The supporting member is in strip shape and cooperates with the forced supporting member.

9. The method for shaping and preparing a square battery case according to claim 8, characterized in that: The first supporting surface has a first vertex, the second supporting surface has a second vertex, and the distance from the outer surface of the forced support to its rotation center gradually increases from the first vertex to the second vertex; the ratio of the distance from the second vertex to the rotation center of the forced support to the distance from the first vertex to the rotation center of the forced support is less than or equal to 2.

10. The method for shaping and preparing a square battery case according to claim 8, characterized in that: The cold drawing devices are arranged in multiple groups to perform multiple cold drawing on the round tube.

11. The method for shaping and preparing a square battery case according to claim 1, characterized in that: The support tube members are provided in two groups, and the two groups of support tube members are respectively provided on both sides of the cam, and the side of the support tube members is provided with a first inner concave surface, and the two sides of the height direction of the two groups of support tube members respectively form a second inner concave surface.

12. The method for shaping and preparing a square battery case according to claim 11, characterized in that: The first shaping member is provided with a first convex portion corresponding to the first inner concave surface, and the second shaping member is provided with a second convex portion corresponding to the second inner concave surface.

13. The method for shaping and preparing a square battery case according to claim 12, characterized in that: The inner concave size of the first inner concave surface is less than or equal to 2%-5% of the distance between the end faces of the two groups of support pipes in the width direction; the inner concave size of the second inner concave surface is less than or equal to 3%-6% of the distance between the end faces of the two groups of support pipes in the height direction.

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