A multi-constraint step extrusion forming method for large-sized anisotropic and abnormally shaped box blanks

Abstract

The present invention discloses a multi-constraint step-by-step extrusion forming method for large-sized anisotropic and heteromorphic box blanks, which includes five steps: upsetting forming, preparing the first set of dies, forming in the first process, preparing the second set of dies, and forming in the second process. In the forming of the first process, the large anvil presses the blank down twice. When pressing down for the second time, the insert block at the left front part of the first female die is removed, and the blank moves towards the left front of the inner cavity to form a protrusion. In the forming of the second process, first, the strip-shaped punch presses the blank down to make the redundant blank flow towards the arched cavity, and then the strip-shaped punch and the arched punch press down simultaneously to form the final box body with a horizontal boss. The design of the present invention is ingenious. By changing the force-bearing position of the blank with two sets of dies, the two-dimensional extrusion is transformed into three-dimensional extrusion, the pressure is applied reasonably, the forming load is effectively reduced, and the product meeting the service conditions is made with fewer steps and less pressure, improving the material utilization rate and production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic processing and forming of metal materials, and in particular refers to a multi-constraint step-by-step extrusion forming method for a large-scale anisotropic and shaped box blank. Background Art

[0002] With the development of science and technology and the changes in the war form, weapons and equipment are developing in the direction of large-scale and lightweight. Special-shaped boxes with lightweight, integration and complexity have gradually become the first choice for special equipment and large and complex components. The common methods for manufacturing large and complex special-shaped boxes are casting, multi-directional press extrusion or direct machining. The traditional casting process is prone to produce defects such as loose organization, shrinkage holes and bubbles, which will cause great material waste in the production process and low material utilization rate; and if the anisotropic and heterogeneous boxes need to be formed in one time, a multi-directional press is required, but the box size is large and the equipment requirements are high; simple machining has low production efficiency and mechanical properties are difficult to guarantee; especially for special-shaped boxes with anisotropic bosses, the forming direction of the bosses of the special-shaped box-like components is not in the same plane as the forming direction of the box as a whole. Therefore, the difficulty in forming the special-shaped box-like components lies in how to reasonably design the shape of the forging and the structure of the die to flow the excess blank to the required part. The shortcomings of the existing forming methods are difficult to meet the service conditions of such large special-shaped box components. Summary of the invention

[0003] The purpose of the present invention is to provide a multi-constraint step-by-step extrusion forming method for a large-scale anisotropic and shaped box blank, which effectively overcomes the problems brought about by the existing traditional box structure processing and manufacturing, utilizes the metal flow law to form complex boss parts, improves the comprehensive mechanical properties of the formed box, effectively reduces the forming load, and improves material utilization and production efficiency.

[0004] To achieve the above object, the solution of the present invention is: a multi-constraint step-by-step extrusion forming method for a large-scale anisotropic and shaped box blank, including two step-by-step extrusion processes, involving two sets of dies, and the specific steps are as follows:

[0005] S1 Upsetting: The bar is formed into a blank through upsetting process;

[0006] S2 Prepare the first set of molds: Preheat the first set of molds, which includes an upper mold assembly and a lower mold assembly; the upper mold assembly includes an upper template, a punch, a large anvil, a small anvil, and a handle; the upper template is connected to the upper part structure of the press, the punch is fixed at the lower end of the upper template, the large anvil and the small anvil are installed below the punch, and the handle is connected to the large anvil; the lower mold assembly includes a first female die, an internal stress ring, an external stress ring, a lower template, a top plate, and a ejector rod; the lower template is connected to the lower part of the press, the internal stress ring is fixed on the lower template, the first female die and the top plate are installed inside the internal stress ring; the first female die is installed on the top plate, the first female die is composed of multiple inserts, and the multiple inserts surround an inner cavity for placing the blank below the punch; the length of the large anvil is the same as the width of the right and middle parts of the inner cavity, and the large anvil is moved above the right and middle parts of the inner cavity through the handle, so that the lower end of the large anvil extends into the right or middle part of the inner cavity to squeeze the blank; the size of the small anvil is the same as that of the left rear part of the inner cavity, so that the lower end of the small anvil extends into the left rear part of the inner cavity to squeeze the blank; a knockout hole is opened in the middle of the bottom of the inner cavity, and the size matches that of the ejector rod, and the external stress ring is press-fitted and sleeved outside the internal stress ring;

[0007] S3 First process forming: Put the preheated blank into the inner cavity, install the large anvil below the punch, and the large anvil is pressed down twice in sequence, including:

[0008] The first press-down: Install the large anvil above the right part of the inner cavity, the press descends to drive the punch to move downward to press the large anvil against the right part of the inner cavity, and stop squeezing after the blank completely fills the right part of the inner cavity;

[0009] The second press-down: Remove the insert at the left front part of the first female die, use the handle to move the large anvil above the middle part of the inner cavity, the large anvil presses down the middle part of the inner cavity, so that the excess blank moves to the left front of the inner cavity to form a protrusion, and make the height of the blank in the middle part of the inner cavity equal to the height of the blank in the right part;

[0010] After the second press-down of the large anvil is completed, remove the large anvil, install the small anvil above the left rear part of the inner cavity, the press drives the punch to descend to press the small anvil against the left rear part of the inner cavity, so that the height of the blank in the left rear part of the inner cavity is equal to the height of the blank in the middle and right parts, and the blank is squeezed into shape; after the extrusion is completed, the press drives the punch to rise away from the formed blank, remove the small anvil, the ejector rod rises to eject the formed blank, the first female die, and the top plate, and remove the formed blank;

[0011] S4 Prepare the second set of molds: Preheat the second set of molds, which includes an upper template, a strip-shaped punch, an arched punch, a second female die, an upper stress ring, a lower stress ring, and a support block. The upper template is connected to the upper part of the press. The strip-shaped punch and the arched punch are installed at the lower end of the lower template. The second female die is provided with a receiving cavity for placing the blank formed in the first process after being turned 90°. The strip-shaped punch has the same size as the upper part of the receiving cavity, so that the lower end of the strip-shaped punch extends into the receiving cavity to extrude the blank. The top of the receiving cavity protrudes forward to form an arched cavity. The arched punch has the same size as the arched cavity, and the lower end of the arched punch extends into the arched cavity to extrude the blank. The support block is installed at the lower part of the arched cavity to support the second female die when extruding the blank. The upper stress ring is sleeved on the upper part of the second female die, and the lower stress ring is sleeved on the lower part of the second female die.

[0012] S5 Second process forming: Preheat the blank formed in the first process, turn the preheated blank 90° with the convexity facing up and place it into the receiving cavity. Install the strip-shaped punch at the lower end of the upper template. The press descends to drive the strip-shaped punch to press down on the top of the blank, and press the excess blank into the arched cavity. Then install the arched punch at the lower end of the upper template. The press drives the strip-shaped punch and the arched punch to press down again. After the blank is completely filled in the second female die, a formed box body with a horizontal convex platform on the top is obtained, and stop extruding. The press drives the strip-shaped punch and the arched punch to rise and separate from the formed box body. Remove the support block, the upper stress ring, and the lower stress ring, and then disassemble the second female die to take out the formed box body.

[0013] Further, in steps S2 and S3, the handle is set at one end in the length direction of the large anvil, and when the large anvil extrudes the blank, it is always located above the first female die, the internal stress ring, and the external stress ring.

[0014] Further, the first female die in steps S2 and S3 is composed of five inserts, including one insert each provided at the front, rear, and right parts, and two inserts arranged side by side in the front and rear of the left part. The five inserts enclose a horizontal T-shaped inner cavity for placing the blank. The left front part of the T-shaped inner cavity extends to the left to form an arc cavity, and the arc cavity is filled with the insert in the left front part.

[0015] Further, in step S3, after removing the insert in the left front part, the arc cavity in the left front part of the T-shaped inner cavity is exposed. The large anvil presses down on the middle of the inner cavity to make the blank flow into the arc cavity to form a convexity, so that after the small anvil presses down, the left front part of the formed blank has convexities protruding horizontally to the left and vertically upward.

[0016] Further, in steps S4 and S5, the second female die is an assembled female die composed of multiple side plates and a bottom plate. After the box body is formed, the side plates are disassembled to take out the formed box body.

[0017] Furthermore, in steps S4 and S5, the second set of dies further includes a fixed backing plate. The strip-shaped punch and the arched punch are quickly installed at the lower end of the lower template through the fixed backing plate. The fixed backing plate is fixed to the lower end of the lower template. A chute is provided at the lower end of the fixed backing plate. Guide rails matching the chute are provided at the tops of the strip-shaped punch and the arched punch. The guide rails are clamped with the chute to fix the strip-shaped punch and the arched punch to the fixed backing plate.

[0018] After adopting the above solution, the beneficial effects of the present invention are as follows:

[0019] The present invention uses a step-by-step extrusion method for forming. Compared with the traditional one-time extrusion forming method, multiple-step extrusion can effectively reduce the forming load. The present invention also makes full use of the fluidity of the metal. In the second extrusion process of the large anvil in step S3, by changing the number of inserts, the blank is made to move in the direction of the least resistance, that is, to flow left forward to form a protrusion. In step S5, first, the strip-shaped punch presses down on the blank to make the excess blank flow into the arched cavity, and then the strip-shaped punch and the arched punch press down simultaneously to form a special-shaped box body with a horizontal boss. Compared with the traditional forming method, the present invention uses two sets of dies and, through two extrusion processes, makes full use of the metal flow law to step-by-step extrude the blank from two planar directions to form a special-shaped box body with a boss at the end, improving the material utilization rate and production efficiency. The present invention is ingeniously designed. By changing the stress position of the blank, two-dimensional extrusion is transformed into three-dimensional extrusion, and pressure is reasonably applied to effectively reduce the forming load. With fewer steps and less pressure, a product that meets the service conditions is manufactured.

[0020] In addition, the present invention uses anvils of different sizes and strip-shaped punches and arched punches of different shapes to step-by-step extrude the blank, which can change the stress area of the blank, better control the metal stress state, equivalent strain, plastic deformation, and tissue uniformity, etc., ensuring the smooth progress of the forming. At the same time, the present invention uses hot extrusion forming technology. Compared with cold extrusion technology, it greatly reduces the extrusion pressure and ensures the optimal comprehensive mechanical properties of the material while ensuring near-net forming. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the box body finally manufactured by the present invention;

[0022] Figure 2 It is a schematic structural diagram of the first set of dies of the present invention;

[0023] Figure 3 It is a sectional view of the first set of dies of the present invention;

[0024] Figure 4 It is a top view of the complete lower die assembly of the present invention;

[0025] Figure 5 It is the top view of the lower die assembly for removing the left front insert of the present invention;

[0026] Figure 6 It is the schematic structural diagram of the first pressing state of the large anvil block of the present invention;

[0027] Figure 7 It is the schematic structural diagram of the second pressing state of the large anvil block of the present invention;

[0028] Figure 8 It is the schematic structural diagram of the pressing state of the small anvil block of the present invention;

[0029] Figure 9 It is the schematic structural diagram of the blank formed in the first process step of the present invention;

[0030] Figure 10 It is the schematic structural diagram of the second set of dies of the present invention;

[0031] Figure 11 It is the sectional view of the second set of dies of the present invention;

[0032] Figure 12 It is the exploded view of the parts of the second set of dies of the present invention;

[0033] Figure 13 It is the top view of the second female die of the present invention;

[0034] Figure 14 It is the top view of the strip-shaped punch of the present invention;

[0035] Figure 15 It is the top view of the arched punch of the present invention;

[0036] Figure 16 It is the process flow chart of the present invention.

[0037] Reference numeral description:

[0038] 1. Target formed box body; 11. Boss; 2. First set of dies; 201. Upper template; 202. Punch; 203. Large anvil block; 204. Small anvil block; 205. Handle; 206. First female die; 2061. Insert; 207. Inner stress ring; 208. Outer stress ring; 209. Lower template; 210. Top plate; 211. Ejector rod; 212. Inner cavity; 213. Arc cavity; 3. Second set of dies; 31. Strip-shaped punch; 32. Arched punch; 321. Guide rail; 33. Second female die; 331. Side plate; 332. Bottom plate; 333. Accommodating cavity; 334. Arched cavity; 34. Upper stress ring; 35. Lower stress ring; 36. Fixed backing plate; 361. Slide groove; 37. Support block; 38. Filler block; 4. Blank; 41. Protrusion; 5. Screw. Detailed implementation manners

[0039] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] As Figure 1 shown, the target forming box body 1 of the present invention is in a "T" shape. When the box body is placed vertically, its top is provided with a horizontal boss 11 protruding forward. The boss 11 is not in the same plane as the overall box body. Therefore, the forming direction of the boss 11 is not in the same plane as the overall forming direction of the box body. The traditional extrusion method is single-sided centralized forming or overall one-time forming, which will bring the problem of uneven forming load. Therefore, the difficulty in forming this special-shaped box body component lies in how to flow the excess blank 4 to the required part, that is, the horizontal boss 11 part of the present invention, by reasonably designing the shape of the forging and the structure of the female die. It is necessary to reasonably control the flow direction of the blank 4 and the forming load. For this purpose, the present invention adopts two sets of molds and, through two extrusion processes, extrudes and forms the special-shaped box body step by step from two plane directions.

[0041] As Figures 2 to 8 shown, the first set of molds 2 involved in the present invention includes an upper mold assembly and a lower mold assembly; the upper mold assembly includes an upper template 201, a punch 202, a large anvil 203, a small anvil 204, and a handle 205. The upper template 201 is connected to the upper part structure of a press (not shown in the figure). The punch 202 is fixed to the lower end of the upper template 201. The large anvil 203 and the small anvil 204 are installed below the punch 202. The handle 205 is connected to the large anvil 203, and the large anvil 203 can be moved by driving the handle 205.

[0042] The lower die assembly includes a first female die 206, an internal stress ring 207, an external stress ring 208, a lower template 209, a top plate 210, and ejector rods 211. The lower template 209 is connected to the lower part of a press. The internal stress ring 207 is fixed on the lower template 209. The first female die 206 and the top plate 210 are installed inside the internal stress ring 207, and the first female die 206 is installed on the top plate 210. The first female die 206 is composed of multiple detachable inserts 2061, including one insert 2061 provided at each of the front, rear, and right parts, and two inserts 2061 arranged side by side in the front and rear of the left part. The five inserts 2061 enclose a transverse T-shaped inner cavity 212 for placing a blank 4 below a punch 202. The left front part of the T-shaped inner cavity 212 extends leftward to form an arc-shaped cavity 213, and the arc-shaped cavity 213 is filled with the insert 2061 at the left front part. The punch 202 can be in a T shape corresponding to the first female die 206 to achieve sufficient extrusion and reduce the material for making the punch 202. The length of the large anvil 203 is the same as the width of the right and middle parts of the inner cavity 212, and the large anvil 203 can be moved above the right and middle parts of the inner cavity 212 through a handle 205, so that the lower end of the inner cavity 212 can extend into the right and middle parts of the inner cavity 212 to extrude the blank 4. The handle 205 is arranged at one end in the length direction of the large anvil 203. When moving the large anvil 203, the handle 205 is always located above the first female die 206, the internal stress ring 207, and the external stress ring 208, and does not affect the first female die 206, the internal stress ring 207, and the external stress ring 208 during the process of the large anvil 203 extruding the blank 4. The size of the small anvil 204 is the same as that of the left rear part of the inner cavity 212, so that the lower end of the small anvil 204 can extend into the left rear part of the inner cavity 212 to extrude the blank 4. A top hole is opened in the middle of the bottom of the inner cavity 212, and the size is matched with the ejector rods 211. The external stress ring 208 is sleeved outside the internal stress ring 207 by interference fit. The internal and external cooperation of the internal stress ring 207 and the external stress ring 208 further improves the die strength and prevents stress overload from damaging the forming of the blank 4. The upper template 201 and the punch 202, and the lower template 209 and the internal stress ring 207 are fixedly connected by screws 5 to prevent the punch 202 from sliding relative to the upper template 201 and the internal stress ring 207 from sliding relative to the lower template 209.

[0043] Such as Figures 10 to 15As shown in the figure, the second set of molds 3 involved in the present invention includes an upper template 201, a strip-shaped punch 31, an arched punch 32, a second female die 33, an upper stress ring 34, and a lower stress ring 35. The upper template 201 is connected to the upper part of the press; the strip-shaped punch 31 and the arched punch 32 are installed at the lower end of the lower template 209. A fixed backing plate 36 can be arranged between the strip-shaped punch 31 and the arched punch 32 and the upper template 201, and is fixed to the upper template 201 through the fixed backing plate 36. The fixed backing plate 36 is fixed at the lower end of the lower template 209, and the strip-shaped punch 31 and the arched punch 32 are installed at the lower end of the fixed backing plate 36; the second female die 33 is an assembled female die composed of a plurality of side plates 331 and a bottom plate 332. The side plates 331 and the bottom plate 332 enclose a receiving cavity 333 for the blank 4 formed in the first process to be placed vertically after being turned 90°. The size of the strip-shaped punch 31 is the same as that of the receiving cavity 333, and the strip-shaped punch 31 can extend into the receiving cavity 333 to extrude the blank 4; a arched cavity 334 protrudes forward at the top of the receiving cavity 333. The size of the arched punch 32 is the same as that of the arched cavity 334, and the arched punch 32 can extend into the arched cavity 334 to extrude the blank 4; to save the manufacturing material of the second female die 33, the lower part of the arched cavity 334 can be set to be hollow, and a support block 37 is installed below the arched cavity 334 to support the second female die 33, ensure the stability of the second female die 33 during extrusion, make the extrusion more sufficient, and can also reduce the cost; the upper stress ring 34 is sleeved on the upper part of the second female die 33, and the lower stress ring 35 is sleeved on the lower part of the second female die 33. The upper stress ring 34 and the lower stress ring 35 can enhance the strength of the second female die 33 and prevent the second set of molds 3 from cracking due to stress overload.

[0044] The upper template 201 and the fixed backing plate 36 are fixedly connected by screws 5 to prevent the fixed backing plate 36 from sliding relative to the upper template 201; the strip-shaped punch 31 and the arched punch 32 are quickly installed at the lower end of the upper template 201 through the fixed backing plate 36. Specifically, a chute 361 is opened at the lower end of the fixed backing plate 36, and guide rails 321 matching the chute 361 are provided at the tops of the strip-shaped punch 31 and the arched punch 32. The guide rails 321 are clamped with the chute 361 to fix the strip-shaped punch 31 and the arched punch 32 to the fixed backing plate 36, which is convenient for disassembling and assembling the strip-shaped punch 31 and the arched punch 32. The disassembly and assembly are simple and fast, saving production time and realizing rapid production; when the size of the fixed backing plate 36 is not enough, supplementary blocks 38 can be fixed on both sides of the fixed backing plate 36 to increase the extrusion pressure and prevent the strip-shaped punch 31 and the arched punch 32 from sliding.

[0045] As Figure 16 shown, the present invention provides a multi-constraint step-by-step extrusion forming method for a large-sized anisotropic and special-shaped box blank, and the specific steps are as follows:

[0046] S1 Upsetting forming: Upset the bar stock into the blank 4 through the upsetting process;

[0047] S2 Prepare the first set of dies 2: Assemble the internal stress ring 207, external stress ring 208, lower template 209 and ejector rod 211 according to the above assembly relationship, and install the assembled above components on the lower working table of the press, so that the lower template 209 is connected to the lower part structure of the press; Connect and fix the upper template 201 and the punch 202, and install the installed upper template 201 and punch 202 on the upper working table of the press, so that the upper template 201 is connected to the upper part structure of the press; Preheat the first female die 206, large anvil 203, small anvil 204 and top plate 210. After the preheating is completed, place the first female die 206 and the top plate 210 into the internal stress ring 207;

[0048] S3 First process forming: Put the preheated blank 4 into the inner cavity 212, install the large anvil 203 below the punch 202, and the large anvil 203 is pressed down twice in sequence, including:

[0049] The first press: As Figure 6 shown, install the large anvil 203 above the right part of the inner cavity 212. The descent of the press drives the punch 202 to move downward, so that the large anvil 203 presses down the right part of the inner cavity 212. Stop pressing after the blank 4 completely fills the right part of the inner cavity 212;

[0050] The second press: As Figure 7 shown, the press drives the punch 202 to rise, remove the insert 2061 at the left front part of the first female die 206, so that the arc cavity 213 at the left front part of the T-shaped inner cavity 212 is exposed. Use the handle 205 to move the large anvil 203 above the middle part of the inner cavity 212, and lower the press to make the large anvil 203 press down the middle part of the inner cavity 212, so that the excess blank 4 moves to the left front of the inner cavity 212, so that the blank 4 flows into the arc cavity 213 to form a horizontal protrusion 41, and make the height of the blank 4 in the middle part of the inner cavity 212 equal to the height of the blank 4 in the right part, so that the blank 4 completely fills the middle and right parts of the inner cavity 212;

[0051] If after the two presses, the heights of the middle and right parts of the blank 4 are not equal, the large anvil 203 can be moved to the uneven part by using the handle 205 and continue to press until the blank 4 is extruded flat;

[0052] After the large anvil 203 is pressed, raise the press and remove the large anvil 203, and install the small anvil 204 below the punch 202, as Figure 8As shown, the length of the small anvil 204 is the same as the width of the left rear part of the inner cavity 212. The lower end of the small anvil 204 extends into the left rear part of the inner cavity 212. The press drives the punch 202 to descend, pressing down the small anvil 204 on the left rear part of the inner cavity 212, making the height of the blank 4 in the left rear part of the inner cavity 212 flush with the height of the blanks 4 in the middle and right parts. At the same time, the excess blank 4 is squeezed towards the arc cavity 213 to form a vertical protrusion 41, that is, the blank 4 is initially extruded and formed. After the extrusion is completed, the press drives the punch 202 to rise and separate from the formed blank 4, removes the small anvil 204, the ejector rod 211 rises to eject the formed blank 4, the first female die 206 and the top plate 210, removes the insert 2061 of the first female die 206, and takes out the formed blank 4; as Figure 9 shown, the formed blank 4 is a T-shaped box body with irregular protrusions 41 protruding horizontally to the left and vertically upwards at the left front part;

[0053] S4 Prepare the second set of dies 3: Connect and fix the upper template 201 and the fixed backing plate 36, and install the upper template 201 and the fixed backing plate 36 on the upper working table of the press, so that the upper template 201 is connected to the upper part structure of the press; Preheat the second female die 33, the long strip punch 31, and the arched punch 32. After the preheating is completed, assemble the second female die 33, the support block 37, the upper stress ring 34, and the lower stress ring 35 according to the above assembly relationship;

[0054] S5 Second process forming: After preheating the blank 4 formed in the first process, turn it clockwise by 90°, place its protrusion 41 upwards into the receiving cavity 333, install the long strip punch 31 at the lower end of the fixed backing plate 36, the press descends to drive the long strip punch 31 to press down the top of the blank 4, so that the blank 4 fills the receiving cavity 333, and presses the excess blank 4 in the upper part of the receiving cavity 333 into the arched cavity 334; Then raise the press, install the arched punch 32 at the lower end of the fixed backing plate 36, the press drives the long strip punch 31 and the arched punch 32 to press down again. After the blank 4 is completely filled with the second female die 33, a formed box body with a horizontal convex platform 11 at the top is obtained, and the extrusion is stopped; The press drives the long strip punch 31 and the arched punch 32 to rise and separate from the formed box body, removes the support block 37 and the stress rings, then removes the side plate 331 of the second female die 33, and takes out the formed box body. This formed box body is the special-shaped box body with a horizontally convex platform 11 protruding forward at the top finally manufactured by the present invention.

[0055] The present invention forms by means of step-by-step extrusion. Compared with the traditional one-time extrusion forming method, multiple-step extrusion can effectively reduce the forming load. The present invention also makes full use of the fluidity of the metal. In the second extrusion process of the large anvil 203 in step S3, by changing the number of inserts 2061, the blank 4 is made to move in the direction with the least resistance, that is, to flow left forward to form a protrusion 41. In step S5, first, the long-strip punch 31 presses down the blank 4 to make the redundant blank 4 flow into the arched cavity 334, and then the long-strip punch 31 and the arched punch 32 press down simultaneously to form a special-shaped box body with a horizontal boss 11. Compared with the traditional forming method, the present invention adopts two sets of molds and, through two extrusion processes, makes full use of the flow law of the metal to step-by-step extrude the blank 4 from two plane directions to form the final special-shaped box body with a boss 11, improving the material utilization rate and production efficiency. The design of the present invention is ingenious. By changing the force-bearing position of the blank 4, two-dimensional extrusion is transformed into three-dimensional extrusion, and pressure is reasonably applied to effectively reduce the forming load, and a product meeting the service conditions is made with fewer steps and less pressure.

[0056] In addition, the present invention adopts anvils of different sizes and long-strip punches 31 and arched punches 32 with different shapes to step-by-step extrude the blank 4, which can change the force-bearing area of the blank 4, better control the metal stress state, equivalent strain, plastic deformation, tissue uniformity, etc., and ensure the smooth progress of forming. At the same time, the present invention adopts hot extrusion forming technology. Compared with cold extrusion technology, the extrusion pressure is greatly reduced, and while ensuring near-net forming, the optimal comprehensive mechanical properties of the material are also ensured.

[0057] The above are only the preferred embodiments of the present invention and do not limit the design of this case. All equivalent changes made according to the key design of this case fall within the protection scope of this case.

Claims

1. A multi-constraint step-by-step extrusion forming method for large-scale anisotropic and heteromorphic box blanks, characterized in that: It includes two-step extrusion processes and involves two sets of dies. The specific steps are as follows: S1 Upsetting forming: The bar stock is formed into a blank through the upsetting process; S2 Prepare the first set of dies: Preheat the first set of dies. The first set of dies includes an upper die assembly and a lower die assembly. The upper die assembly includes an upper template, a punch, a large anvil, a small anvil, and a handle. The upper template is connected to the upper part structure of the press. The punch is fixed to the lower end of the upper template. The large anvil and the small anvil are installed below the punch. The handle is connected to the large anvil. The lower die assembly includes a first female die, an internal stress ring, an external stress ring, a lower template, a top plate, and a ejector rod. The lower template is connected to the lower part of the press. The internal stress ring is fixed to the lower template. The first female die and the top plate are installed inside the internal stress ring. The first female die is installed on the top plate. The first female die is composed of multiple inserts. The multiple inserts enclose an inner cavity for the blank to be placed below the punch. The length of the large anvil is the same as the width of the right and middle parts of the inner cavity. The large anvil is moved above the right and middle parts of the inner cavity through the handle, so that the lower end of the large anvil extends into the right or middle part of the inner cavity to extrude the blank. The size of the small anvil is the same as that of the left rear part of the inner cavity, so that the lower end of the small anvil extends into the left rear part of the inner cavity to extrude the blank. A knockout hole is opened in the middle of the bottom of the inner cavity, and its size matches that of the ejector rod. The external stress ring is press-fitted and sleeved outside the internal stress ring; S3 Forming in the first process: Put the preheated blank into the inner cavity. Install the large anvil below the punch. The large anvil makes two downward presses in sequence, including: The first downward press: Install the large anvil above the right part of the inner cavity. The press descends to drive the punch to move downward, causing the large anvil to press the right part of the inner cavity. Stop extrusion after the blank completely fills the right part of the inner cavity; The second downward press: Remove the insert at the left front part of the first female die. Use the handle to move the large anvil to above the middle part of the inner cavity. The large anvil presses the middle part of the inner cavity, making the excess blank move to the left front of the inner cavity to form a protrusion, and making the height of the blank in the middle part of the inner cavity equal to the height of the blank in the right part; After the second downward press of the large anvil is completed, remove the large anvil. Install the small anvil above the left rear part of the inner cavity. The press drives the punch to descend, causing the small anvil to press the left rear part of the inner cavity, making the height of the blank in the left rear part of the inner cavity equal to the height of the blanks in the middle and right parts, and extruding the blank into shape. After extrusion is completed, the press drives the punch to rise away from the formed blank. Remove the small anvil. The ejector rod rises to eject the formed blank, the first female die, and the top plate. Remove the formed blank; S4 Prepare the second set of molds: Preheat the second set of molds. The second set of molds includes an upper template, a strip-shaped punch, an arched punch, a second female die, an upper stress ring, a lower stress ring, and a support block. The upper template is connected to the upper part of the press. The strip-shaped punch and the arched punch are installed at the lower end of the lower template. The second female die is provided with a receiving cavity for placing the blank formed in the first process after being turned 90°. The strip-shaped punch has the same size as the upper part of the receiving cavity, so that the lower end of the strip-shaped punch extends into the receiving cavity to extrude the blank. An arched cavity protrudes forward from the top of the receiving cavity. The arched punch has the same size as the arched cavity, and the lower end of the arched punch extends into the arched cavity to extrude the blank. The support block is installed at the lower part of the arched cavity to support the second female die when extruding the blank. The upper stress ring is sleeved on the upper part of the second female die, and the lower stress ring is sleeved on the lower part of the second female die. S5 Forming in the second process: Preheat the blank formed in the first process. After turning the preheated blank 90° with the convexity facing up, place it into the receiving cavity. Install the strip-shaped punch at the lower end of the upper template. The press descends to drive the strip-shaped punch to press down on the top of the blank, and press the excess blank into the arched cavity. Then install the arched punch at the lower end of the upper template. The press drives the strip-shaped punch and the arched punch to press down again. After the blank completely fills the second female die, a formed box body with a horizontal convex platform on the top is obtained, and stop extruding. The press drives the strip-shaped punch and the arched punch to rise away from the formed box body. Remove the support block, the upper stress ring, and the lower stress ring, and then disassemble the second female die to take out the formed box body.

2. A multi-constraint step-by-step extrusion forming method for a large-scale anisotropic and abnormally shaped box blank as described in claim 1, characterized in that: In steps S2 and S3, the handle is set at one end in the length direction of the large anvil, and when the large anvil extrudes the blank, it is always located above the first female die, the internal stress ring, and the external stress ring.

3. A multi-constraint step-by-step extrusion forming method for large-scale anisotropic and irregular box blanks as described in claim 1, characterized in that: In step S2 and step S3, the first female die is composed of five inserts, including one insert provided at the front, rear, and right parts respectively, and two inserts arranged side by side in the front and rear of the left part. The five inserts enclose a horizontal T-shaped inner cavity for placing the blank. The left front part of the T-shaped inner cavity extends leftward to form an arc cavity, and the arc cavity is filled with the insert in the left front part.

4. A multi-constraint step-by-step extrusion forming method for a large-sized anisotropic and heteromorphic box blank as described in claim 3, characterized in that: In step S3, after removing the insert in the left front part, the arc cavity in the left front part of the T-shaped inner cavity is exposed. The large anvil presses down on the middle part of the inner cavity to make the blank flow into the arc cavity to form a convexity, so that after the small anvil presses down, the left front part of the formed blank has convexities protruding horizontally to the left and vertically upward.

5. A multi-constraint step-by-step extrusion forming method for a large-sized anisotropic and abnormally shaped box blank as described in claim 1, characterized in that: In steps S4 and S5, the second female die is an assembled female die composed of multiple side plates and a bottom plate. After the box body is formed, the side plates are disassembled to take out the formed box body.

6. A multi-constraint step-by-step extrusion forming method for a large-sized anisotropic and heterotypic box blank as described in claim 1, characterized in that: In steps S4 and S5, the second set of molds further includes a fixed backing plate. The strip-shaped punch and the arched punch are quickly installed at the lower end of the lower template through the fixed backing plate. The fixed backing plate is fixed at the lower end of the lower template. A chute is opened at the lower end of the fixed backing plate. Guide rails matching the chute are provided at the tops of the strip-shaped punch and the arched punch. The guide rails are clamped with the chute to fix the strip-shaped punch and the arched punch to the fixed backing plate.

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