Method for manufacturing rectangular cylindrical metal body

Abstract

[Problem] The present invention addresses the problem that when manufacturing a bottomed rectangular cylindrical body consisting of two pairs of long sides and two pairs of short sides from a metal material, the height of an open end surface of the four sides cannot be set in an extrusion molding process. [Solution] The rectangular cylindrical metal body of the present invention is obtained by adjusting a metal material such that the cross-sectional area thereof is larger than the projected surface area of the product in a plan view, and extrusion molding the metal material.

Description

Manufacturing method for metal square cylinder

[0001] The present invention relates to a method for manufacturing a rectangular cylindrical body having a bottom and consisting of two pairs of long sides and two pairs of short sides from a metal material.

[0002] Conventionally, containers used, for example, in battery cases, specifically rectangular cylindrical bodies with a bottom (hereinafter referred to as the "target product") have mainly been produced by a so-called deep drawing process in which a metal plate material is placed on a die and pulled into the die from above with a punch.

[0003] However, this deep drawing process has the following problems: The corners of the container bottom become thin, and to prevent breakage, multiple drawing and ironing processes are required, increasing the number of processes; an intermediate annealing process is required to prevent breakage of the metal plate material, reducing productivity; and the use of metal plate material increases material costs.

[0004] In order to improve the above-mentioned problems that occur in deep drawing, it has been proposed recently to use a square billet as shown in Fig. 6(a) as a material, rather than a metal plate material, as the material, and to produce the product by backward extrusion molding (also called impact molding) using the device shown in Fig. 6(b). However, even if the target product is produced by backward extrusion molding, the problem of breakage occurring easily in the side portion near the bottom as shown in Fig. 6(c) is not significantly improved, and the heights of the four sides forming the opening become uneven, requiring a separate processing step after backward extrusion molding to make the heights of the four sides of the opening uniform.

[0005] For example, in Patent Document 1 (JP 2022-15900 A), when manufacturing a case in which the width between the outer and inner surfaces is defined as the thickness and thick and thin sections are arranged side by side in the circumferential direction, the problem is that when the material is extruded backward, the end surfaces do not become flat, and cutting is required to make these surfaces flat, and a method is proposed to solve this problem.

[0006] That is, in Patent Document 1, a final workpiece that is the material to be molded into a case has a first portion that becomes the thick portion when molded into the case, and a second portion that becomes the thin portion when molded into the case, and is prepared in a state in which the height of the first portion when viewed in an axial direction, which is the direction in which the tube extends when the final workpiece is molded into the case, is lower than the height of the second portion when viewed in the axial direction, and the final workpiece is set in a hole in a die that is formed in a shape corresponding to the outer surface and extends in a predetermined direction, in an attitude in which the axial direction of the final workpiece coincides with the one direction, and the final workpiece is pressed from the one direction by a first punch that is provided with a pressing portion that forms a protrusion shaped to correspond to the inner surface, and the final workpiece is thereby molded into the case by backward extrusion molding.

[0007] In Patent Document 1, backward extrusion molding is performed such that the gap between the wall of the die hole and the first punch is set relatively wide in the first part of the final workpiece and relatively narrow in the second part, and therefore "the amount of material is greater in the thick part than in the thin part," and based on this, "the height of the thick first part is made lower than the height of the thin second part," thereby offsetting the effect of the difference in flow rate and making the end surface flat.

[0008] Patent Document 1 is similar to the present invention only in that it "flattens the end surface" and "uses pre-adjusted materials" in consideration of differences in material flow rates. However, Patent Document 1 is premised on the production of cases in which thick and thin portions are set side by side in the circumferential direction, and therefore cannot be used to manufacture the products covered by the present application.

[0009] The statement in Patent Document 1 that "the thick portion stretches more than the thin portion" means that there is a difference in the flow rate of the material, and theoretically, this difference in flow rate at the adjacent part between the thick portion and the thin portion will cause breakage.

[0010] Furthermore, in Patent Document 1, the "height of the material" is adjusted so that "the height of the thick first portion is lower than the height of the thin second portion," but there is also the problem that adjusting the height of a certain material and molding it before manufacturing in order to flatten the edge surface of the product is itself time-consuming.

[0011] JP 2022-15900 A

[0012] The problem that this invention aims to solve is that when manufacturing a bottomed rectangular cylindrical body consisting of two pairs of long sides and two pairs of short sides from metal material, it is not possible to easily control the height of the four sides that form the open end surface during the extrusion molding process.

[0013] In order to solve the above problems, the present invention provides a method for manufacturing a bottomed metal square cylindrical body consisting of two pairs of long sides and two pairs of short sides in a planar view by controlling the height of the opening end faces of the cylindrical body of each pair of long sides and short sides, and the metal material is adjusted so that the cross-sectional area in a planar view is larger than the projected area of ​​the product to be obtained, and the metal material is extruded.

[0014] According to the present invention, a bottomed rectangular metal tubular body consisting of two pairs of long and short sides in a plan view can be manufactured without fractures in the side surfaces near the bottom by controlling the height of the open end faces of each pair of long and short sides of the tubular body without fine adjustments such as providing high and low portions in the metal material before manufacturing. Therefore, in processing after extrusion molding, processing such as making the open end faces uniform in height or raising or lowering one of the pair of short sides or the pair of long sides, including the degree of height, is not required.

[0015] 1A is a perspective view of a metal material used in the present invention, (b) is a plan view of the metal material used in the present invention, and (c) is a diagram showing the state of the metal material used in the present invention loaded into a forward extrusion molding device before extrusion molding. 1A is a perspective view of a target product obtained by the present invention, (b) is a plan view of the target product obtained by the present invention, and (c) is a diagram showing the state of the target product while it is still in the forward extrusion molding device after extrusion molding is completed. 1B is a diagram showing the flow of the metal material used in the present invention during forward extrusion molding, with (a) a plan view, (b) a long side cross-sectional view, and (c) a short side cross-sectional view. 1C is a graph showing the relationship between excess material and the difference between the long side height and the short side height in the present invention. 1D is a diagram for explaining the projected area of ​​the product, (b) the cross-sectional area of ​​the metal material, and (c) the excess material in the present invention. 1D is a diagram for explaining the technology for obtaining a target product from a square billet by backward extrusion molding, as a premise example of the present invention.

[0016] In the present invention, when manufacturing a metal square cylindrical body (hereinafter referred to as the "target product") with a bottom consisting of two pairs of long sides and two pairs of short sides in a plan view, the objective of making the heights of the four sides forming the opening equal or freely adjusting the heights of the four sides is achieved by adjusting the cross-sectional area of ​​the metal material so that it is larger than the projected area of ​​the product in a plan view, and then extruding the metal material.

[0017] An embodiment of the present invention will be described with reference to the drawings. The metal material M and the target product C will be described by referring to the metal material M before and during forming in FIG. 1 and the target product C after forming in FIG. 2. The present invention uses a metal material M (having an excess pad portion Mα) adjusted to have a larger cross-sectional area as shown in FIG. 5(b) than the projected area of ​​the target product C in a plan view as shown in FIG. 5(a). Specifically, in this example, for example, a metal material M is used whose long side length is such that each of the short sides bulges outward by the excess pad portion α relative to the long side length of the target product C to be obtained.

[0018] In the present invention, "adjustment by providing an excess metal portion Mα" does not refer to "preforming" adjustment, such as adjusting the height in advance, as in Patent Document 1, but simply refers to adjusting the size of the billet. Therefore, from the perspective of adjusting the size of the billet, the present invention involves using a metal material M having a cross-sectional area larger than the projected area of ​​the surface formed by two pairs of long sides and short sides of the target product. In this example, the excess metal portion Mα refers to the difference between the cross-sectional area and the projected area.

[0019] 1(c) and 2(c), the manufacturing method is carried out by using, for example, a forward extrusion molding apparatus 1 including a die D, a lower punch P1 disposed in the die D, and a punch P for extruding a metal material M between the inner surface of the die D and the outer surface of the lower punch P1. Note that a backward extrusion molding apparatus may also be used to carry out the method of the present invention.

[0020] Next, we considered the difference in height of the four sides that make up the opening. The fluidity of the metal material M in the flow space formed between the outer surface of the lower punch P1 fixed inside the die D and the inner surface of the die D in forward extrusion molding is such that more metal material flows along the pair of long sides than along the pair of short sides, and when an unadjusted square billet is used as the metal material M, the height of the opening end face of the pair of short sides is low and the height of the opening end face of the pair of long sides is high.

[0021] Furthermore, when considering fluidity, as shown in Figure 3, the lower punch P1 of the metal material M causes the metal material M to flow from the center S of the short sides, which connects the longitudinal centers of each of the pair of short sides, toward both long sides, and the metal material M present in the short side portions in the flow space flows as is on both short sides.

[0022] In other words, when forward extrusion molding is performed using an unadjusted square billet as metal material M, the flow rate of the metal material M increases on both long sides while decreasing on both short sides, and this difference in flow rate is manifested as a difference in the height of the four sides forming the opening (the pair of short sides is lower than the pair of long sides).

[0023] In the present invention, the above-mentioned metal material M flows from the short side center S, which connects the length centers of each side of the pair of short sides, in the directions of both long sides, and the metal material M present in the short side portion in the flow space flows as is on both short sides.Based on this fact, the portion of the metal material M that becomes the pair of short sides of the target product in a planar view is adjusted in the long side length direction toward the opposite side from the opposing direction of each side of the pair of short sides (metal material M having an excess metal portion Mα is used).

[0024] As described above, when forward extrusion is performed on an unadjusted square billet as the metal material M, the height of the opening end face of the pair of long sides of the target product becomes higher than the opening height of the pair of short sides. As a result of simulation based on the above findings, it was found that the difference in opening height has the relationship shown in Figure 4.

[0025] The simulation conditions were as follows: A square billet of pure aluminum (A1050 O material) with a planar length (short side length) of 16 mm (vertical X), a planar length (long side length) of 100 mm (horizontal Y), and a thickness of 16.6 mm was used as the metal material M. The target product C had an opening with a long side length (external dimension) of 100 mm (horizontal Y) and a short side length (external dimension) of 16 mm (vertical X). In the metal material M, the amount of expansion of the pair of short sides, i.e., the excess pad α, in the long side direction was changed toward the opposite side from the opposing direction of each side of the pair of short sides.

[0026] 4 shows the relationship between the difference in height between the opening height of the pair of long sides and the opening end height of the pair of short sides and the adjustment amount of the excess pad portion Mα, i.e., the relationship between the excess pad α and the total amount of excess pad α bulging out in the long side length direction in the opposite direction from the facing direction of each side of the pair of short sides, as shown on the horizontal axis. To redefine, the excess pad α is the amount (portion) per short side adjusted in the long side length direction in the opposite direction from the facing direction of each side of the pair of short sides, and the excess pad portion Mα is the total amount (generic term) of the excess pad α and excess pad α of both short sides.

[0027] 4, in this simulation, if the height difference is 0 mm, that is, if the height of the pair of long sides and the height of the pair of short sides in the opening are made equal, it can be seen that the excess pad Mα should be 16 mm. In this example, the excess pad Mα = 16 mm means that in advance, the portions of the metal material M that will become the pair of short sides should be adjusted by bulging them outward by 8 mm in the long side length direction toward the opposite side from the opposing direction of each side of the pair of short sides (excess pad α = 8 mm). In other words, a metal material M with a planar width Y (long side length) of 116 mm should be used.

[0028] In addition, in the simulation shown in Figure 4, when the excess material portion Mα is less than 16 mm, the height difference is a positive value, i.e., the height of the opening end surface of the pair of long sides is higher than that of the pair of short sides, and when the excess material portion Mα is greater than 16 mm, the height difference is a negative value, i.e., the height of the opening end surface of the pair of long sides is lower than that of the pair of short sides.

[0029] From the above, the excess pad α can be determined taking into consideration the volume (height x projected area) of each side that forms the opening. In this example, which simulates the production of a target product C in which the thickness of each of the four sides that form the opening is the same, if the height of the pair of long sides that form the opening in the target product C is used as the standard and the height of the pair of short sides is made equal to or higher than this, then the metal material M can be used with a dimension that is equal to or greater than the width Y (long side length) in a plan view of the target product C, as a dimension that bulges outward in the long side length direction of the excess pad α in the opposite direction to the opposing direction of each side of the pair of short sides.

[0030] In short, by using metal material M taking the above into consideration, the amount of metal material M that flows from the pads α to both short sides during molding is abundant, and at least when the short side height is made uniform based on the long side height at the opening end, there is no shortage of metal material M that flows to both short sides, and stable and reliable control can be achieved. Also, by taking the above into consideration, it is possible to control the short side height to be large or the long side height to be large.

[0031] Furthermore, when manufacturing a target product C in which the thickness of each side of the target product C differs by adjusting the size of the lower punch P1 in the die D, by using a metal material M having an excess thickness Mα that takes into account the volume of each side of the target product C, it is possible to control not only the opening height of each side of the pair of short sides and the pair of long sides, but also the thickness.

[0032] In the present invention, in forming a bottomed rectangular metal cylinder, the ratio of the extruded area to the cross-sectional area of ​​the metal material M is large, and when it is extruded downward from the lower punch, it is extruded through a stage where it is formed into a fairly uniform square billet shape, so there are no restrictions on the shape of the metal material M itself as long as the total volume of the material required for the target product C is satisfied. For this reason, it goes without saying that in the present invention, there is no need to pre-form the metal material M.

[0033] Therefore, as long as the requirements of the present invention are met and the overall volume of material required for the target product C is satisfied, the metal material M may be, for example, a cylindrical round billet material cut from a cheaper bar material, and there is no need to limit the shape to these round billets or square billets.

[0034] 1 Forward extrusion molding device C Target product M Metal material Mα Excess material (total amount of excess material α, general term) α Excess material (adjustment amount on each side, part)

Claims

1. A method for manufacturing a rectangular metal tube with a bottom, consisting of two pairs of long sides and two pairs of short sides when viewed in a plane, by controlling the height of the open end faces of the tube for each pair of long sides and short sides, in which the cross-sectional area of ​​the metal material is adjusted to be larger than the projected area of ​​the product when viewed in a plane, and the metal material is extruded to produce a rectangular metal tube.

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