Cold forging process and forming die for multi-step fan-shaped parts

Abstract

The present invention relates to a cold forging forming process and forming die for a multi-step sector-shaped part. The forming process includes the preparation of a sector-shaped profile and a longitudinal upsetting forming process. First, a rolling mill is used to make a round bar material into a sector-shaped profile in a roller rolling state, and a drawing die of a cold drawing machine is used to draw the sector-shaped profile in a roller rolling state into a sector-shaped profile for upsetting; then, according to the length of the target part, a section of the sector-shaped profile for upsetting is cut and placed in a forming die for longitudinal semi-open upsetting forming to obtain a target part that meets the requirements. The forming die includes an upper die and a lower die. In the lower die, a C-shaped positioning elastic ring is used to position the die assembly circumferentially to avoid relative rotation between the upper die assembly and the lower die assembly. The present invention adopts a longitudinal semi-open upsetting forming method to form parts that can be directly installed and used and have very high precision, thereby improving production efficiency, reducing the production cost of such parts, and improving their market competitiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of metal cold forging, and in particular relates to a cold forging forming process and a forming die for a multi-step sector-shaped part. Background Art

[0002] Currently, one of the stator structures of DC motors is a multi-step fan-shaped structure, which can achieve multi-pole concentrated winding and reduce the length of the winding ends to facilitate automated assembly, reduce product costs and prices, and enhance market competitiveness.

[0003] The cross-sectional profile at any position in the structure of a general multi-step fan-shaped part is approximately fan-shaped. The "approximately fan-shaped" means that the multi-step fan-shaped part is a part of a fan with different radius and the same angle, and retains the arc of the fan to which it belongs, but the multi-step fan has multiple rounded corners in the circumference, and the center of the cross-section of the multi-step fan-shaped part is located outside the cross-section.

[0004] The multi-step sector is divided into a rod and a crown along the longitudinal direction, the cross section of the rod is smaller than the cross section of the crown, and the crown is a structure with multiple steps, and the cross section area of ​​the multiple steps gradually increases from the rod to the end face of the crown. Since the rod and the crown have a relatively strict positional relationship, parts of this structure are not easy to machine. Under the existing processing method, a horizontal open die forging method is generally adopted, which requires pre-forging, horizontal open final forging, trimming, and grinding of the burrs left after cutting off the flash after trimming, and finally completing the processing of the entire part. The entire production process has many steps, a long production cycle, a short die life, and a high cost, which reduces the market competitiveness of such products. Summary of the invention

[0005] The purpose of the present invention is to provide a cold forging forming process and forming die for multi-step fan-shaped parts. In this process, the characteristics of material net forming are utilized and a longitudinal semi-open upsetting forming method is adopted to form parts with high precision that can be directly installed and used, thereby improving production efficiency, reducing the production cost of such parts and improving their market competitiveness.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a cold forging forming process of a multi-step fan-shaped part, wherein the cross-sectional profile at any position of the multi-step fan-shaped part is approximately fan-shaped and has multiple rounded corners, and one end of the multi-step fan-shaped part has a multi-layer step structure; the forming process includes the preparation of a fan-shaped profile and a longitudinal upsetting forming process, in the preparation of the fan-shaped profile, a round bar material is made into a fan-shaped profile in a roller-rolled state by a rolling mill, and the fan-shaped profile in a roller-rolled state is drawn into a fan-shaped profile for upsetting by a drawing die of a cold drawing machine; in the longitudinal upsetting forming process, according to the length of the target part, a section of the fan-shaped profile for upsetting is cut and placed in a forming die for longitudinal semi-open upsetting forming to obtain a target part that meets the requirements;

[0007] The forming die used in the cold forging process includes an upper die and a lower die, the upper die has a convex die for downwardly extruding the profile, the lower die has a concave die cavity that matches the shape of the multi-step fan-shaped piece, the concave die cavity is surrounded by a die hole in the concave die assembly and a top piece extending into the die hole, the concave die assembly includes an upper concave die assembly and a lower concave die assembly that are concentrically arranged up and down, a C-shaped positioning elastic ring is sleeved on the periphery of the concave die assembly, and the C-shaped positioning elastic ring can position the circumference of the concave die assembly to avoid relative rotation between the upper concave die assembly and the lower concave die assembly;

[0008] The upper die assembly is composed of an upper die and an upper die middle ring sleeved outside the upper die, and the lower die assembly is composed of a lower die and a lower die middle ring sleeved outside the lower die. The inner edge of the junction of the lower die and the upper die is used to form a chamfer at the end of the rod portion in a multi-step sector shape. The upper die middle ring and the lower die middle ring are both in a circular shape, and the outer circular surface has a plane. The inner circular surface shape of the C-shaped positioning elastic ring is consistent with the outer circular surface shape of the upper die middle ring and the lower die middle ring, and the height of the C-shaped positioning elastic ring is equal to the sum of the heights of the upper die middle ring and the lower die middle ring, so that the C-shaped positioning elastic ring combines the upper die assembly and the lower die assembly together.

[0009] Before the round bar material is roller rolled, the round bar material is in a hot rolled state and is sequentially annealed, shot blasted and coated.

[0010] After the round bar material is roller-rolled, the obtained sector-shaped profile in the roller-rolled state is subjected to non-oxidation annealing, shot blasting, and film treatment, and then is drawn using a cold drawing machine.

[0011] The film treatment is a phosphorus saponification treatment or a graphene lubrication + saponification treatment.

[0012] During the non-oxidation annealing, vacuum protection or nitrogen protection is used.

[0013] During the drawing process using a cold drawing machine, stone particles with a diameter of 3mm~5mm are added to the drawing powder used.

[0014] The cross-sectional profile of the sector-shaped profile in the roller-rolled state has no rounded corners.

[0015] The cross-sectional profile of the fan-shaped profile used for upsetting is processed with fillets, and the number and position of the fillets are the same as the number and position of the fillets on the cross-sectional profile of the prepared target part.

[0016] A forming die for a multi-step sector-shaped part, used for processing the multi-step sector-shaped part, comprises an upper die and a lower die, wherein the upper die has a convex die for downwardly extruding a profile, and the lower die has a concave die cavity that matches the shape of the multi-step sector-shaped part, and the concave die cavity is surrounded by a die hole in a concave die assembly and a top piece extending into the die hole, and the concave die assembly comprises an upper concave die assembly and a lower concave die assembly that are concentrically arranged up and down, and a C-shaped positioning elastic ring is sleeved on the periphery of the concave die assembly, and the C-shaped positioning elastic ring can position the circumference of the concave die assembly to prevent the upper concave die assembly and the lower concave die assembly from rotating relative to each other;

[0017] The upper die assembly is composed of an upper die and an upper die middle ring sleeved outside the upper die, and the lower die assembly is composed of a lower die and a lower die middle ring sleeved outside the lower die. The inner edge of the junction of the lower die and the upper die is used to form a chamfer at the end of the rod portion in a multi-step sector shape. The upper die middle ring and the lower die middle ring are both in a circular shape, and the outer circular surface has a plane. The inner circular surface shape of the C-shaped positioning elastic ring is consistent with the outer circular surface shape of the upper die middle ring and the lower die middle ring, and the height of the C-shaped positioning elastic ring is equal to the sum of the heights of the upper die middle ring and the lower die middle ring, so that the C-shaped positioning elastic ring combines the upper die assembly and the lower die assembly together.

[0018] The present invention has the following innovations and advantages: the present invention adopts a longitudinal semi-open upsetting forming method, fully utilizes the net forming characteristics of the material, directly forges and forms without generating flash and burrs, and can be directly installed and used after forming without subsequent processing and trimming. From the process point of view, one process is reduced, thus improving the processing efficiency. From the material utilization point of view, since no flash is generated, there is no need to cut out excess flash, which can improve the material utilization, thereby reducing the production cost of such parts and improving the market competitiveness of the products.

[0019] The forming mold used in the present invention is used in conjunction with the improved process. During the forging process of the blank, the upper die assembly and the lower die assembly may rotate relative to each other, which may cause the blank to rotate, thereby destroying the shape of the part surface and producing defective products. In this regard, the present invention improves the shape of the die center ring, and provides a plane on the outer circular surface of the die center ring, so that the outer circular surface is not a complete circle, and the plane of the outer circular surface of the die center ring and the plane of the inner circular surface of the C-shaped positioning elastic ring fit each other, thereby preventing the possibility of rotation of the upper die assembly and the lower die assembly, thereby ensuring the forming shape and surface quality of the part. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a sector-shaped profile in a roller-rolled state obtained after a round bar material is roller-rolled;

[0021] Figure 2 for Figure 1 Sectional view at AA in the middle;

[0022] Figure 3 is a schematic diagram of a fan-shaped profile used for upsetting;

[0023] Figure 4 for Figure 3 Sectional view at the middle BB;

[0024] Figure 5 It is a schematic diagram of the structure of the multi-step fan-shaped part after forming;

[0025] Figure 6 A schematic diagram of the structure of the molding die used in the present invention;

[0026] Figure 7 It is a schematic diagram of the structure of the middle ring of the die;

[0027] Figure 8 It is a schematic diagram of the structure of a C-type positioning elastic ring;

[0028] Fig. 9 Schematic diagram of the structure of the upper die;

[0029] Fig.10 It is a structural schematic diagram of the lower concave die;

[0030] Numbers in the figure: 1. Sector-shaped profile in roller rolling state, 2. Sector-shaped profile for upsetting, 3. Rod, 4. Crown, 401. First-level step structure, 402. Second-level step structure, 5. Upper die frame, 6. Punch pad, 7. Punch fixing ring, 8. Punch, 9. Fixing nut, 10. Multi-step sector, 11. Upper die, 12. Upper die middle ring, 13. C-type positioning elastic ring, 14. Lower die, 1401. Circular boss, 15. Lower die middle ring, 16. Die outer ring, 17. Ejector, 18. Die base, 19. Ejector pad, 20. Large pad, 21. Fixed die base, 22. Ejector, 23. Lower die frame, 24. Die middle ring, 25. Plane, 26. Notch. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the invention in any way.

[0032] See attached Figure 5 As shown, the crown 4 of the multi-step sector 10 prepared in this embodiment has two steps, a first step structure 401 and a second step structure 402, the cross section of the first step structure is larger than the cross section of the second step structure, and both are larger than the cross section of the rod 3. The material used for preparation is a round bar of pure iron DT4, and the forming process includes the preparation of the sector profile and the longitudinal semi-open upsetting forming process. The specific steps are as follows:

[0033] (1) Preparation process of fan-shaped profiles:

[0034] The hot-rolled round bar material is subjected to annealing, shot blasting, coating treatment, roller rolling, non-oxidation annealing, shot blasting, and coating treatment, and then drawn using a wire drawing die to form an intermediate state of a fan-shaped profile for upsetting;

[0035] The heating temperature of annealing is 860°C, the holding time is 3 hours, and then it is cooled to 500°C in the furnace and then air-cooled;

[0036] During shot blasting, steel shot with a diameter of 0.6 mm is used, and the shot blasting time is 10 to 15 minutes;

[0037] The film treatment may be phosphorus saponification treatment or graphene lubrication + saponification treatment;

[0038] The heating temperature of non-oxidation annealing is 860℃, the holding time is 3 hours, vacuum protection or nitrogen protection, then cooling to 500℃ with the furnace, and air cooling;

[0039] The drawing process of the wire drawing die adopts a horizontal cold drawing machine, and the lubrication method is to add stone particles with a diameter of 3mm to 5mm in the wire drawing powder.

[0040] After roller rolling, a sector-shaped profile 1 in a roller rolling state is obtained. At this time, the profile has no rounded corners and has poor dimensional accuracy. Figure 1 , 2 shown.

[0041] After the drawing process, a fan-shaped profile 2 for upsetting is obtained. At this time, the profile is processed with rounded corners, the dimensional accuracy is high, and the number and position of the rounded corners are consistent with the parts to be processed, such as Figure 3 , 4 shown.

[0042] Longitudinal semi-open upsetting forming process: according to the size of the final required part, the fan-shaped profile 2 for upsetting obtained in the previous step is cut and blanked, placed in the mold cavity of the forming mold, and longitudinally semi-opened upsetting forming is performed to form a fan-shaped part with a larger crown 4 and a smaller stem 3, that is, the multi-step fan-shaped part 10 of the present invention, such as Figure 5 The formed part has a shaft part with good precision and a crown part that can be installed and matched. The relative positions of the shaft and the crown are accurate, and no subsequent trimming and grinding are required.

[0043] When cutting materials, the length of the cut bars needs to be kept consistent to control the volume and maintain the stability of the weight, so that each forging has good consistency.

[0044] The specific structure of the molding die used in the above process is as follows Figure 6 As shown, it includes an upper die and a lower die, the upper die has a punch 8 that can extrude the profile downward, and also includes an upper die frame 5, a punch pad 6, a punch fixing ring 7 and a fixing nut 9. The punch fixing ring 7 is fixed to the upper die frame 5 by screws, the punch pad 6 and the upper ends of the punch 8 are installed in the punch fixing ring 7, the lower end of the punch 8 extends downward from the punch fixing ring 7, the upper end of the punch 8 has a limiting ring, the fixing nut 9 is sleeved on the punch 8 and is threadedly connected to the punch fixing ring 7, the limiting ring on the punch 8 is pressed against the inner edge of the fixing nut 9, thereby realizing the positioning and fixation of the punch pad 6, the punch 8 and the punch fixing ring 7.

[0045] The lower mold has a mold cavity that matches the shape of the multi-step fan-shaped part, and the mold cavity is surrounded by a mold hole in the mold assembly and a ejector 17 extending into the mold hole. The mold assembly includes an upper mold assembly and a lower mold assembly. The upper mold assembly consists of an upper mold 11 and an upper mold middle ring 12 sleeved outside the upper mold 11, and the lower mold assembly consists of a lower mold 14 and a lower mold middle ring 15 sleeved outside the lower mold 14. The upper mold hole of the upper mold 11 and the lower mold hole of the lower mold 14 correspond to each other to form the mold hole, the shape of the upper mold hole in the upper mold 11 matches the shape of the target part, the shape of the lower mold hole of the lower mold 14 matches the shape of the rod of the target part, the shape of the upper end of the ejector 17 matches the lower mold hole, so as to insert the profile in the lower mold hole to support the mold hole, and the connecting position of the upper mold hole and the lower mold hole is used to form the chamfer of the end position of the rod 3 of the target part.

[0046] The upper die center ring 12 and the lower die center ring 15 are collectively referred to as the die center ring 24 and have the same structure. Figure 7 As shown, they are both circular, and the outer surface has a plane 25. The upper die 11 and the upper die center ring 12 are interference fit, and the lower die 14 and the lower die center ring 15 are interference fit. By limiting the relative rotation of the upper die center ring 12 and the lower die center ring 15, the rotation of the upper die 11 and the lower die 14 in the circumferential direction can be limited, thereby ensuring that the chamfer of the end of the part rod is accurate relative to the rod without misalignment.

[0047] The shape structure of the upper die and the lower die is as follows Fig. 9 , 10 As shown, a circular boss 1401 is provided on the upper end surface of the lower die 14, and the lower end surface of the upper die 11 is a plane. The provision of the circular boss 1401 can reduce the contact area between the upper die 11 and the lower die 14, making the two fit more closely.

[0048] A C-shaped positioning elastic ring 13 is also sleeved on the periphery of the die assembly. The C-shaped positioning elastic ring 13 is annular. Figure 8 As shown, a notch is provided in the circumferential direction to facilitate the disassembly and assembly of the die center ring 24. The inner circumferential surface shape of the C-shaped positioning elastic ring 13 matches the outer circumferential surface shape of the die center ring 24, and also has a plane 25. In this way, after the die center ring 24 is placed in the C-shaped positioning elastic ring 13, the C-shaped positioning elastic ring 13 can position its position in the circumferential direction of the die center ring to prevent the die center ring from rotating. The height of the C-shaped positioning elastic ring 13 is equal to the sum of the heights of the upper die center ring 12 and the lower die center ring 15, so that the C-shaped positioning elastic ring 13 combines the upper die assembly and the lower die assembly together. The C-shaped positioning elastic ring 13 can position the die assembly in the circumferential direction to prevent the upper die assembly and the lower die assembly from rotating during the upper die pressing process, that is, the above-mentioned restriction on the upper die center ring 12 and the lower die center ring 15.

[0049] The C-shaped positioning elastic ring 13 is also covered with a die outer ring 16, and the die outer ring 16 is fixed to the lower die frame 23 through a fixed die base 21. The die assembly and the ejector 17 are installed on the die base 18, and the die base 18 is fixed to the lower die frame 23 through a large pad 20. The lower end of the ejector 17 is pressed against the ejector pad 19, and the ejector pad 19 is driven by the ejector rod 22 below to move up and down in the movable cavity in the center of the die base 18, so that the ejector 17 can eject the part out of the mold upward.

[0050] After the upper die 11 and the upper die middle ring 12 are interference fitted, the upper die hole in the upper die 11 and the plane 25 on the outer cylindrical surface of the upper die middle ring 12 are processed. Similarly, after the lower die 14 and the lower die middle ring 15 are interference fitted, the lower die hole in the lower die 14 and the plane 25 on the outer cylindrical surface of the lower die middle ring 15 are processed. In the upper die assembly and the lower die assembly, there is a certain positional correspondence between the upper die hole of the upper die 11 and the plane 25 on the outer cylindrical surface of the upper die middle ring 12, and this positional relationship is also applicable to the lower die hole of the lower die 14 and the plane of the outer cylindrical surface of the lower die middle ring 15, so that the upper die hole of the upper die 11 and the lower die hole of the lower die 14 can be positioned with the help of the C-shaped positioning elastic ring 13.

[0051] The working sequence of the above forming mold is: the intercepted fan-shaped profile 2 for upsetting is placed in the die hole of the lower die, and the upper die part is pressed downward by the forging machine, and the punch 8 squeezes the profile downward until the punch 8 moves to a certain distance from the upper surface of the upper die 11, completing the longitudinal semi-open upsetting of the profile, forming a multi-step fan-shaped part 10 with a large crown 4 and a two-step structure and a smaller stem 3; then after the upper die returns, the ejector 22 pushes the ejector pad 19 to move upward, driving the ejector 17 to move upward, ejecting the parts in the die hole, and completing the preparation process of the multi-step fan-shaped part 10.

[0052] In the above process, the large fan-shaped part of the crown of the prepared multi-step fan-shaped part 10 has a two-layer step structure, wherein the lower step structure is the second step structure 402 formed in the die hole of the die, and the upper step structure is the first step structure 401 formed between the punch 8 and the upper die 11. Therefore, when the upper die is pressed down, the stopping position of the punch 8 needs to be a certain distance away from the upper die 7, and the distance is related to the height of the formed first step structure 401.

Claims

1. A cold forging process for a multi-step sector-shaped part, wherein the cross-sectional profile of any position of the multi-step sector-shaped part is approximately sector-shaped and has multiple rounded corners, and one end of the multi-step sector-shaped part has a two-layer step structure; characterized in that: The forming process includes the preparation of the fan-shaped profile and the longitudinal upsetting forming process. In the preparation of the fan-shaped profile, a rolling mill is used to make a round bar material into a fan-shaped profile in a roller-rolled state, and a drawing die of a cold drawing machine is used to draw the fan-shaped profile in the roller-rolled state into a fan-shaped profile for upsetting. In the longitudinal upsetting forming process, according to the length of the target part, a section of the fan-shaped profile for upsetting is cut and placed in a forming die for longitudinal open upsetting forming to obtain a target part that meets the requirements. The forming die used in the cold forging process comprises an upper die and a lower die, the upper die having a convex die for extruding the profile downward, and is characterized in that: the lower die has a die cavity that matches the shape of the multi-step fan-shaped piece (10), the die cavity is surrounded by a die hole in the die assembly and a pusher (17) extending into the die hole, the die assembly comprises an upper die assembly and a lower die assembly that are concentrically arranged up and down, a C-shaped positioning elastic ring (13) is sleeved on the periphery of the die assembly, and the C-shaped positioning elastic ring (13) can position the die assembly in the circumferential direction to prevent the upper die assembly and the lower die assembly from rotating relative to each other; The upper die assembly is composed of an upper die (11) and an upper die middle ring (12) sleeved outside the upper die (11); the lower die assembly is composed of a lower die (14) and a lower die middle ring (15) sleeved outside the lower die (14); the inner edge of the junction between the lower die (14) and the upper die (11) is used to form a chamfer at the end of the rod portion of the multi-step sector (10); the upper die middle ring (12) and the lower die middle ring (15) are all in the shape of a ring, and the outer circular surface has a flat section, the inner circular surface shape of the C-shaped positioning elastic ring (13) is consistent with the outer circular surface shape of the upper die middle ring (12) and the lower die middle ring (15), and the height of the C-shaped positioning elastic ring (13) is equal to the sum of the heights of the upper die middle ring (12) and the lower die middle ring (15), so that the C-shaped positioning elastic ring (13) combines the upper die assembly and the lower die assembly together.

2. The cold forging process of a multi-step sector-shaped part according to claim 1, characterized in that: Before the round bar material is roller rolled, the round bar material is in a hot rolled state and is sequentially annealed, shot blasted and coated.

3. The cold forging process of a multi-step sector-shaped part according to claim 2, characterized in that: After the round bar material is roller-rolled, the obtained sector-shaped profile in the roller-rolled state is subjected to non-oxidation annealing, shot blasting, and film treatment, and then is drawn using a cold drawing machine.

4. A cold forging process for a multi-step sector-shaped part according to claim 2 or 3, characterized in that: The film treatment is a phosphorus saponification treatment or a graphene lubrication + saponification treatment.

5. The cold forging process of a multi-step sector-shaped part according to claim 3, characterized in that: During the non-oxidation annealing, vacuum protection or nitrogen protection is used.

6. A cold forging process for a multi-step sector-shaped part according to claim 2 or 3, characterized in that: During the drawing process using a cold drawing machine, stone particles with a diameter of 3mm~5mm are added to the drawing powder used.

7. The cold forging process of a multi-step sector-shaped part according to claim 1, characterized in that: The cross-sectional profile of the sector-shaped profile in the roller-rolled state has no rounded corners.

8. The cold forging process of a multi-step sector-shaped part according to claim 1, characterized in that: The cross-sectional profile of the fan-shaped profile used for upsetting is processed with fillets, and the number and position of the fillets are the same as the number and position of the fillets on the cross-sectional profile of the prepared target part.

9. A forming die for a multi-step sector-shaped part, used for processing the multi-step sector-shaped part as claimed in claim 1, comprising an upper die and a lower die, wherein the upper die has a convex die for extruding the profile downward, characterized in that: The lower mold has a die cavity that matches the shape of the multi-step fan-shaped piece (10), the die cavity is surrounded by a die hole in the die assembly and a pusher (17) extending into the die hole, the die assembly comprises an upper die assembly and a lower die assembly that are concentrically arranged up and down, a C-shaped positioning elastic ring (13) is sleeved on the periphery of the die assembly, and the C-shaped positioning elastic ring (13) can position the die assembly in the circumferential direction to prevent the upper die assembly and the lower die assembly from rotating relative to each other; The upper die assembly is composed of an upper die (11) and an upper die middle ring (12) sleeved outside the upper die (11); the lower die assembly is composed of a lower die (14) and a lower die middle ring (15) sleeved outside the lower die (14); the inner edge of the junction between the lower die (14) and the upper die (11) is used to form a chamfer at the end of the rod portion of the multi-step sector (10); the upper die middle ring (12) and the lower die middle ring (15) are all in the shape of a ring, and the outer circular surface has a flat section, the inner circular surface shape of the C-shaped positioning elastic ring (13) is consistent with the outer circular surface shape of the upper die middle ring (12) and the lower die middle ring (15), and the height of the C-shaped positioning elastic ring (13) is equal to the sum of the heights of the upper die middle ring (12) and the lower die middle ring (15), so that the C-shaped positioning elastic ring (13) combines the upper die assembly and the lower die assembly together.

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