A punch for press forming a rectangular thin-walled steel shell part

Abstract

The application discloses a stamping forming female die for a steel rectangular thin-wall shell part, and a working surface of the stamping forming female die is provided with a straight-angle chamfer structure with a section difference; the straight-angle chamfer structure with the section difference comprises a section difference surface and a female die working surface which are sequentially connected in a punch downward direction; an upper corner of the section difference surface is provided with a round corner R1, and a lower corner is provided with a round corner R2; an upper corner of the female die working surface is provided with a variable-diameter round corner R3, and a lower corner is provided with a round corner R4; two long edges of the working surface of the stamping forming female die are provided with a sectional structure, and the variable-diameter round corner R3 is provided with different radii on each section. The application effectively solves problems, such as instability wrinkling and cracking of a bottom and a mouth, poor demolding and the like in a stamping forming process of the rectangular thin-wall shell.

Description

TECHNICAL FIELD

[0001] The present application relates to a forming die, more particularly to a punch forming die for a steel rectangular thin-walled shell part. BACKGROUND

[0002] Compared with cylindrical shells (cylindrical parts), square shell parts (box-shaped parts) are also widely used and varied, because of the presence of four corners, and some square shells are rectangular and the long and short dimensions differ greatly, so it is much more difficult to form the material than cylindrical shells.

[0003] Typical rectangular thin-walled shell parts, such as lithium battery square shell outer packaging parts or similar shell parts, use a combination of multi-pass deep drawing and thinning deep drawing forming process, and the blank is gradually deep drawn from a near-elliptical shape into a box-shaped part. As shown in Figure 1 The forming die uses a common combination of a punch 1, a die 2, and a blank holder 3, and a bottom support plate can usually be added. The existing die 2 usually has a certain die entry angle, and the angle α is mostly between 20-30°. This die form is suitable for relatively thick aluminum shell materials. However, with the development of new energy vehicles, square shell lithium batteries are constantly seeking lightweight, and low-carbon is also pursued, and steel square shells have become an important choice.

[0004] The choice of a steel square shell necessarily results in a significant reduction in wall thickness, and the material properties differ greatly from aluminum materials, so the die entry angle die form cannot meet the stamping forming requirements of thin-walled rectangular shells. During the forming process, the material flowing to the working surface at the inclined angle position is prone to instability and wrinkling and cannot be eliminated by the bottom support plate, and the four corners of the bottom are prone to cracking.

[0005] In existing patent applications, such as Chinese patent CN 113172158A, which discloses a deep drawing die for box-shaped parts, a combined deep drawing die, and a deep drawing method, including a deformation die section, a roller combination die section, and a straightening die section arranged from top to bottom, i.e., using a rigid die and a roller combination die form, which is beneficial to reducing friction during forming. However, the die design and the corresponding tooling are relatively complex, the equipment requirements are high, and it is not easy to place the blank holder, which is not suitable for the stamping production of rectangular thin-walled shells, especially parts with small corner and fillet radii, and is prone to instability and wrinkling.

[0006] Chinese patent CN 112692169B discloses a die for deep drawing forming of a rolled differential thickness plate box-shaped part, including a deep drawing die part and a hydraulic control part, which can obtain high-quality differential thickness plate box-shaped parts by controlling the reasonable matching of the differential thickness plate thin and thick side blank holder forces. However, it does not involve the details of the die, and for thin-walled shell forming, it cannot control instability and cracking.

[0007] As disclosed in Chinese patent CN 215543792U, an aluminum alloy rectangular box-shaped thin-walled shell cold reverse extrusion die includes an upper punch assembly and a lower die assembly capable of moving downward to close the mold and moving upward to open the mold, which is used for extrusion forming of aluminum alloy square shell. However, it is not suitable for forming processing of rectangular thin-walled steel shell. SUMMARY

[0008] In view of the defects in the prior art, the purpose of the present application is to provide a stamping forming die for a steel rectangular thin-walled shell part, which effectively solves the problems of instability wrinkling, bottom cracking, and poor demolding during the stamping forming process of the rectangular thin-walled shell.

[0009] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0010] A stamping forming die for a steel rectangular thin-walled shell part:

[0011] The working surface of the stamping forming die is provided with a stepped right-angle rounded corner structure;

[0012] The stepped right-angle rounded corner structure includes a stepped surface and a die working surface connected in sequence in the direction of the punch pressing down;

[0013] The upper corner of the stepped surface is provided with a rounded corner R1, and the lower corner is provided with a rounded corner R2;

[0014] The upper corner of the die working surface is provided with a variable-diameter rounded corner R3, and the lower corner is provided with a rounded corner R4;

[0015] The two long edges of the working surface of the stamping forming die are provided with a segmented structure, and the variable-diameter rounded corner R3 is provided with different radii on each segment.

[0016] Preferably, the height H1 of the stepped surface is between 2-10mm.

[0017] Preferably, the inner diameter D1 of the stepped surface is greater than the outer diameter d1 of the outer surface of the shell in the previous forming pass; and

[0018] D1 = d1 + k1, k1 is 0-1mm.

[0019] Preferably, the radius of the rounded corner R1 is between 3-5mm.

[0020] Preferably, the radius of the rounded corner R2 = r2-k2;

[0021] r2 is the rounded corner radius of the outer surface corner of the shell in the previous forming pass, and k2 is 1-2mm.

[0022] Preferably, the segmented structure of the two long edges of the working surface of the stamping forming die specifically includes:

[0023] The midpoint of the long side of the working surface of the stamping forming female die is provided with a point a0;

[0024] The positions on both sides of the point a0 are respectively provided with symmetrical points a1 and a2;

[0025] The positions outside the points a1 and a2 are provided with points a3 and a4, and the points a3 and a4 are symmetrically arranged relative to the point a0; wherein,

[0026] The length A1 of the line segment from the point a1 to the point a2 is (A-B) / 2;

[0027] The length A2 of the line segment from the point a1 to the point a3 and from the point a2 to the point a4 is A1 / 2;

[0028] In the formula, A is the length dimension of the working surface of the stamping forming female die, and B is the width dimension of the working surface of the stamping forming female die.

[0029] Preferably, the radius of the variable radius fillet R3 outside the line segment from the point a3 to the point a4 is r30, and r30 is an initial setting value;

[0030] The radius of the variable radius fillet R3 on the line segment from the point a1 to the point a2 is r31, and r31=k3*initial setting value, and k3 takes a value of 1.5-2 mm;

[0031] The variable radius fillet R3 on the line segment from the point a1 to the point a3 and on the line segment from the point a2 to the point a4 adopts a gradually changing fillet radius, that is, gradually decreasing from r31 to r30.

[0032] Preferably, the radius of the fillet R4 is k4*r31, and k4 takes a value of 2-3 mm.

[0033] The stamping forming female die for a steel rectangular thin-walled shell part provided by the application adopts a straight angle chamfering fillet entry mode with a segment difference, and different entry fillet radii are arranged in sections in the direction of the two long sides of the female die, and the upper and lower fillets on the working surface of the female die are provided with a suitable size relationship, so that the problems of instability wrinkling, bottom cracking, and poor demolding of the bottom and the mouth of the rectangular thin-walled shell during stamping forming can be effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a use state schematic diagram of an existing stamping forming female die;

[0035] Figure 2 is an axial view schematic diagram of the stamping forming female die of the application;

[0036] Figure 3 is a plan view schematic diagram of the stamping forming female die of the application;

[0037] Figure 4 is a schematic diagram of the use state of the stamping forming concave die of the present application. DETAILED DESCRIPTION

[0038] In order to better understand the above technical solutions of the present application, the technical solutions of the present application will be further described below in combination with the drawings and examples.

[0039] In combination with Figures 2 to 4 As shown in the figure, the stamping forming concave die of the steel rectangular thin-walled shell part provided by the present application adopts a straight-angle reverse-rounding entry mode with a step difference, and the two long edge directions of the concave die are arranged in sections with different entry rounding radii, and the upper and lower rounding of the working surface of the concave die is set with a suitable size relationship, so that the instability wrinkling of the bottom and the mouth, the bottom cracking, and the poor demolding during the stamping forming process of the rectangular thin-walled shell can be effectively improved. Specifically, it includes:

[0040] The working surface of the stamping forming concave die 10 is set as a straight-angle reverse-rounding structure with a step difference.

[0041] The straight-angle reverse-rounding structure with a step difference includes a step surface 12 and a concave die working surface 13 connected in sequence along the pressing direction of the punch 11.

[0042] Among them, the height H1 of the step surface 12 is between 2-10mm.

[0043] The inner diameter D1 of the step surface 12 is greater than the outer diameter d1 of the outer surface of the shell of the previous forming pass; and

[0044] D1=d1+k1, k1 takes a value of 0-1mm.

[0045] The upper corner of the step surface 12 is set as a rounding R1, and the lower corner is set as a rounding R2.

[0046] The upper corner of the concave die working surface 13 is set as a variable-diameter rounding R3 (i.e. the entry rounding of the concave die working surface), and the lower corner is set as a rounding R4.

[0047] The radius of the rounding R1 is between 3-5mm.

[0048] The radius of the rounding R2=r2-k2;

[0049] r2 is the rounding radius of the corner of the outer surface of the shell of the previous forming pass, and k2 takes a value of 1-2mm.

[0050] The two long edges of the working surface of the stamping forming concave die 10 are set as sections, and the variable-diameter rounding R3 on each section is set as different radii.

[0051] In combination with Figure 3As shown, A is the length dimension of the working surface of the stamping forming female die 10, B is the width dimension of the working surface of the stamping forming female die 10, and A > B.

[0052] In this way, the two long edges of the working surface of the stamping forming female die 10 are arranged in a segmented manner, which specifically includes:

[0053] A point a0 is arranged at the midpoint of the long edge of the working surface of the stamping forming female die 10.

[0054] Symmetrical points a1 and a2 are arranged at positions on both sides of the point a0.

[0055] Points a3 and a4 are arranged at positions outside the points a1 and a2, and the points a3 and a4 are also symmetrically arranged relative to the point a0.

[0056] The length A1 of the line segment from the point a1 to the point a2 is (A-B) / 2.

[0057] The length A2 of the line segment from the point a1 to the point a3 and from the point a2 to the point a4 is A1 / 2.

[0058] In this way, the radius of the variable-diameter round corner R3 outside the line segment from the point a3 to the point a4 is r30, and r30 is an initial setting value;

[0059] The radius of the variable-diameter round corner R3 on the line segment from the point a1 to the point a2 is r31, and r31=k3*initial setting value, k3 is 1.5-2mm;

[0060] The variable-diameter round corner R3 on the line segment from the point a1 to the point a3 and on the line segment from the point a2 to the point a4 gradually decreases from r31 to r30.

[0061] The radius of the round corner R4 is k4*r31, and k4 is 2-3mm.

[0062] Embodiment

[0063] In this embodiment, for a certain rectangular thin-walled shell, the length, width and height are 154*88*80mm, the round corner radius R3 is 3.6mm, the bottom round corner radius R1 is 1mm, and the wall thickness t0 is 0.30mm; the blank is an elliptical shape with a length of 310mm, a width of 270mm and a thickness of 0.30mm; the blank is stretched in 6 passes, and except for the first pass which uses a common punch-die forming, the dies of the other passes use the die design in the present application. The third pass die is:

[0064] 1) the height H1 of the step surface 12 is 6 mm; the outer diameter d1 of the shell outer surface in the second pass is 203 mm and 148 mm in the length and width center, and the corner outer surface has a round corner radius of R3.5 mm; the inner diameter D1 of the step surface 12 is 203.5 mm and 148.5 mm in the length and width center; the radius of the round corner R1 is 4 mm; and the radius of the round corner R2 is 2 mm;

[0065] 2) the length and width of the working surface of the stamping forming concave die 10 are A=184 mm and B=120 mm, respectively; the length of the line segment from point a1 to point a2 is A1=32 mm; the length of the line segment from point a1 to point a3 and the length of the line segment from point a2 to point a4 are A2=16 mm; the radius of the concave die entry diameter round corner R3 on the line segment from point a1 to point a2 is r31=3.5 mm; the radius of the concave die entry diameter round corner R3 outside the line segment from point a3 to point a4 is r30=2 mm; and the radius of the concave die entry diameter round corner R3 on the line segment from point a1 to point a3 and the line segment from point a2 to point a4 is a gradually changing round corner radius, i.e., gradually decreasing from r31=3.5 mm to r30=2 mm;

[0066] 3) the radius of the lower round corner R4 of the die working surface is 8.8 mm.

[0067] In this way, the step plus right-angle round corner entry mode well controls the mouth instability wrinkling and bottom cracking problems in the steel shell forming process, the segmented arrangement of the die working round corner improves the uneven material flow of the long and short edges in the rectangular thin-walled shell deep drawing forming, the upper and lower round corner radius settings effectively improve the poor demolding of the thin-walled shell, and finally realize the high-quality forming processing of the shell.

[0068] Those skilled in the art in this technical field should realize that the above embodiments are only used to illustrate the present application, and are not used as a limitation of the present application, and as long as the changes and modifications of the above described embodiments are within the scope of the spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A stamping forming concave die of a steel rectangular thin-walled shell part, characterized in that: the working surface of the stamping forming concave die is provided with a straight angle chamfer structure with a step difference; the straight angle chamfer structure with a step difference comprises a step difference surface and a concave die working surface connected in sequence in the direction of the punch pressing; the upper corner of the step difference surface is provided with a round corner R1, and the lower corner is provided with a round corner R2; the upper corner of the concave die working surface is provided with a variable radius chamfer R3, and the lower corner is provided with a round corner R4; the two long edges of the working surface of the stamping forming concave die are provided in a segmented manner, and the variable radius chamfer R3 is provided with different radii on each segment; the two long edges of the working surface of the stamping forming concave die are provided in a segmented manner, which specifically comprises: a point a0 is arranged at the midpoint position of the long edge of the working surface of the stamping forming concave die; symmetrical points a1 and a2 are arranged at the positions on both sides of the point a0; points a3 and a4 are arranged at the positions outside the points a1 and a2, and the points a3 and a4 are symmetrically arranged relative to the point a0; wherein, the length A1 of the line segment from the point a1 to the point a2 is (A-B) / 2; the length A2 of the line segment from the point a1 to the point a3 and from the point a2 to the point a4 is A1 / 2; wherein, A is the length dimension of the working surface of the stamping forming concave die, and B is the width dimension of the working surface of the stamping forming concave die, the radius r30 of the variable radius chamfer R3 outside the line segment from the point a3 to the point a4 is an initial setting value; the radius r31 of the variable radius chamfer R3 on the line segment from the point a1 to the point a2 is k3*initial setting value, and k3 takes a value of 1.5-2 mm; the variable radius chamfer R3 on the line segment from the point a1 to the point a3 and from the point a2 to the point a4 adopts a gradually changing chamfer radius, that is, gradually decreases from r31 to r30; the height H1 of the step difference surface is between 2-10 mm; the inner diameter D1 of the step difference surface is greater than the outer diameter d1 of the outer surface of the shell of the previous forming pass; and D1=d1+k1, k1 takes a value of 0-1 mm; the radius of the round corner R1 is between 3-5 mm; the radius of the round corner R2 is r2-k2; r2 is the chamfer radius of the corner of the outer surface of the shell of the previous forming pass, and k2 takes a value of 1-2 mm; the radius of the round corner R4 is k4*r31, and k4 takes a value of 2-3 mm. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The punch forming die for a steel rectangular thin-walled shell part according to claim 1, characterized in that: ​ 3. The punch forming die for a steel rectangular thin-walled shell part according to claim 1, characterized in that: ​ ​ 4. The punch forming die for a steel rectangular thin-walled shell part according to claim 1, characterized by: ​ 5. The punch forming die for a steel rectangular thin-walled shell part according to claim 4, characterized in that: ​ ​ 6. The punch forming die for a steel rectangular thin-walled shell part according to claim 1, characterized in that: ​

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