Axle head forming process for a combined drive axle housing with axle head

Abstract

The present invention discloses a shaft head forming process for a combined drive axle housing with a shaft head, comprising the following specific steps: step 1) splitting a prefabricated tube formed by liquid expansion pressure from the middle into two initial tube blanks, inserting the prefabricated tube into an upsetting mandrel, and upsetting the prefabricated tube blank by a die at an appropriate temperature to form a locally thickened tube blank; step 2) inserting the locally thickened tube blank into a spinning mandrel, spinning the prefabricated tube blank by a reducing roller at an appropriate temperature to obtain an end-reduced tube blank, and spinning the prefabricated tube blank by a forming shoulder roller to obtain a stepped shaft head; and step 3) heat treating or coating the outer surface of the stepped shaft head prefabricated tube blank with a high-hardness material to obtain a formed shaft head prefabricated tube blank with a high-hardness surface. The shaft head of the drive axle housing manufactured by the present invention can use an original tube blank with a larger diameter, thicken the shaft head wall without losing stability, and ensure the accurate size of the fillet of the inner wall of the transition zone between the shaft head and the drive axle body during the shaft head diameter reduction and shoulder forming, thereby avoiding stress concentration.

Description

Technical Field

[0001] The present invention relates to a method for forming a shaft head of a drive axle housing, and in particular to a method for forming a shaft head integrally with a drive axle housing by liquid expansion forming. Background Art

[0002] Axles with axle heads are commonly found in load-bearing axles and expansion-formed drive axles. This is because the original tube diameter is small, and the selected tube material can meet the axle head hardness requirements through heat treatment. The axle head can be manufactured through upsetting, and the axle head diameter is relatively small compared to the original tube diameter during upsetting, preventing instability. For hydraulically formed drive axle housings, the equivalent diameter in the middle of the axle housing is larger, so the wall thickness in the middle is thinner to achieve lightweight requirements. The diameter of the axle head is smaller, and the wall thickness is thicker to ensure strength. For these hydraulically formed drive axle housings with integrated axle heads, firstly, a larger diameter original tube blank is required to meet the requirements of hydraulic forming. However, the axle head diameter is smaller, significantly different from the original tube diameter. This makes it easy to cause instability in the transition zone between the large and small diameters of the drive axle when forming the axle head. Secondly, the inner wall radius of the transition zone between the axle head and the drive axle housing body must be precisely controlled to ensure stress concentration. Patent publication number CN111558665B discloses a "Hydraulic Bulging Drive Axle Housing Axle Head Forming Process and Die." This process requires four shaft end reductions and three warm pressings. This process is complex and inefficient, and can easily lead to instability during the reduction and warm pressing phases. The internal fillet of the axle housing axle head cannot be precisely controlled, leading to small fillets and even cracking. The seven sets of dies required are costly. This invention addresses the issues of avoiding instability and bulging during axle head manufacturing, while also ensuring the proper size of the inner wall fillet of the axle head to avoid stress concentration caused by small fillets and cracking. Summary of the Invention

[0003] In response to the above problems, the present invention proposes a shaft head forming process for a combined drive axle housing with a shaft head, and the technical solution used is as follows:

[0004] A shaft head forming process for a combined drive axle housing with a shaft head, wherein the overall process route is local thickening of the shaft head - shaft head spinning reduction and shoulder forming - local surface hardening treatment of the shaft head, characterized by comprising the following steps:

[0005] Step 1) Local thickening tube forming:

[0006] The prefabricated tube formed by liquid expansion is split into two initial tube blanks from the middle, and the initial tube blanks are inserted into the upsetting mandrel from both sides. The portion of the end shaft head of the initial tube blank to be thickened is heated to an appropriate temperature, and the end shaft head of the initial tube blank is partially upset through a die, thereby obtaining a locally thickened tube blank with an unchanged outer diameter of the end shaft head and a reduced inner diameter;

[0007] Step 2) Forming the stepped shaft head tube blank:

[0008] The locally thickened tube blank is inserted into the spinning mandrel, the shaft head at the end of the locally thickened tube blank is locally heated to an appropriate temperature, the diameter of the shaft head of the locally thickened tube blank is reduced by spinning with a reducing wheel to obtain an end-reduced tube blank, and the stepped shaft head tube blank is obtained by spinning with a forming shoulder wheel;

[0009] Step 3) External surface hardening treatment:

[0010] The outer surface of the stepped shaft head tube blank is heat treated or coated with a high-hardness material to obtain a formed shaft head tube blank with a high-hardness surface.

[0011] Furthermore, in step 1), the initial tube blank is formed by liquid expansion and pressing, and the cross-sections at the large end and the plate support position have reached the required dimensions, and are cut into two pieces from the middle along a direction perpendicular to the axis of the bridge housing; the cross-section of the large end of the initial tube blank is a circular ring, the cross-section of the plate support position is a rectangular tube, the cross-section of the small end is a circular ring, and the large end and the small end and the plate support position are transitioned by arc surfaces. The upsetting mandrel is an axisymmetric body of revolution, the outer surface and arc surface of its large diameter portion coincide with the inner wall of the corresponding portion of the initial tube blank, the small diameter portion of the upsetting mandrel is 20 to 22 mm smaller than the diameter of the inner wall of the end portion of the initial tube blank, the inner diameter of the guard ring in the mold is 0.2 to 0.4 mm larger than the outer diameter of the end portion of the initial tube blank, the guard ring slides in the base and is reset by a spring and limited by a screw.

[0012] Furthermore, the locally thickened tube blank in step 1) is formed on a three-way hydraulic press. The lower clamping die in the mold is fixed on the press workbench, and the upper clamping die is fixed on the press main slide and moves up and down with the hydraulic press main slide. The two initial tube blanks are sleeved on the upsetting mandrel and the arc surfaces on both sides of the middle of the upsetting mandrel are matched with the inner wall of the initial tube blank. Then, the tube blanks are placed in the lower clamping die. The hydraulic press slide moves downward to drive the upper clamping die to press the initial tube blank. The left and right bases are fixed on the press respectively. On the horizontal sliding template, the horizontal sliding template of the press drives the left and right bases and guard rings to move toward the center. The guard ring first reaches the part of the initial tube blank to be thickened. The end of the upsetting mandrel is inserted into the smaller inner hole of the base to play a positioning and guiding role. The base upsets and thickens the end of the initial tube blank. The inner hole wall of the guard ring prevents the end of the initial tube blank from bulging during upsetting and thickening. The outer wall of the upsetting mandrel end limits the thickening amount of the end of the initial tube blank. The arc surfaces on both sides of the middle of the upsetting mandrel support the inner wall of the initial tube blank to prevent local instability.

[0013] Furthermore, in the step 2), the outer surface and the arc surface of the large diameter portion of the spinning mandrel are consistent with the inner wall of the locally thickened tube blank, the outer wall of the middle portion is consistent with the inner wall of the locally thickened square arm of the tube blank, the radius of the fillet Ra at the small diameter end is a cylinder with a radius of 18mm~22mm, the reducing wheel is a discus shape, the radius of the fillet Rb of the discus edge is 10mm~15mm, and the shoulder wheel is a cylindrical shape, and the fillet Rc between the cylindrical surface and the bottom surface is 4mm~6mm.

[0014] Furthermore, in the step 2) when forming the stepped shaft head tube blank, the locally thickened tube blank is inserted into the spinning mandrel and the arc surface of the spinning mandrel is matched with the inner wall of the locally thickened tube blank. Then, the large end of the spinning mandrel is placed in the main shaft hole of the spinning machine, clamped and driven to rotate by the main shaft. The spinning machine drives the reducing wheel and the shoulder wheel to move axially from the shaft head end side of the locally thickened tube blank to the other side, with the reducing wheel in front and the shoulder wheel in the back; when the reducing wheel spins and reduces the diameter of the end of the locally thickened tube blank, the spinning machine drives the shoulder wheel to move radially so that it contacts the locally thickened tube blank to balance the force generated by the reducing wheel; when the shoulder wheel spins and forms the shoulder of the locally thickened tube blank, the spinning machine drives the reducing wheel to move radially so that it maintains contact with the locally thickened tube blank to balance the force generated by the shoulder wheel; the rounded corner of the small diameter end of the spinning mandrel controls the rounded corner forming size of the inner wall of the end of the locally thickened tube blank.

[0015] Since the present invention adopts the above technical solution, the present invention has the following advantages:

[0016] The hydraulic expansion drive axle housing shaft head manufactured by the present invention can use an original tube blank with a larger diameter, thicken the shaft head wall thickness without losing stability, and ensure the accurate size of the inner wall fillet of the transition area between the shaft head and the drive axle body when reducing the shaft head diameter and forming the shaft shoulder, thereby avoiding stress concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the initial tube blank after liquid expansion and pressing in step 1) of the present invention;

[0018] Figure 2 Schematic diagram of upsetting and extruding a locally thickened tube blank in step 1) of the present invention;

[0019] Figure 3 For the present invention Figure 2 Schematic diagram of the structure at A in the middle;

[0020] Figure 4 Schematic diagram of the upsetting mandrel in step 1) of the present invention;

[0021] Figure 5 This is a schematic diagram of forming the end-reduced tube blank in step 2) of the present invention;

[0022] Figure 6 Schematic diagram of the spinning mandrel in step 2) of the present invention;

[0023] Figure 7 This is a schematic diagram of forming a stepped shaft head tube blank in step 2) of the present invention;

[0024] Figure 8 Schematic diagram of the reducing wheel in step 2) of the present invention;

[0025] Figure 9 Schematic diagram of the middle shoulder rotating wheel in step 2) of the present invention;

[0026] Figure 10 This is a schematic diagram of the final formed shaft head tube blank in step 3) of the present invention.

[0027] Figure numbers: 1. Initial tube blank; 2. Locally thickened tube blank; 3. End-reduced tube blank; 4. Stepped shaft head tube blank; 5. Formed shaft head tube blank; 6. Die; 7. Upsetting mandrel; 8. Spinning mandrel; 9. Reducing roller; 10. Shoulder roller; 6-1. Base; 6-2. Spring; 6-3. Screw; 6-4. Guard ring; 6-5. Upper clamping die; 6-6. Lower clamping die. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be further specifically described below through examples and in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] In the description of the present invention, it should be noted that the terms "up", "down", "in", "out", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention. Example

[0030] When forming and manufacturing the shaft head, in order to meet the strength requirements, local thickening is performed without losing stability or bulging, and the fillet size of the inner wall of the shaft head is guaranteed to avoid the formation of small fillets and cracks that lead to stress concentration.

[0031] To solve the above technical problems, the following steps are included:

[0032] Step 1) locally thickening the tube blank 2 to form, such as Figures 1-4 As shown:

[0033] The liquid-expanded 20Mn2 tube is split from the middle into two initial tube blanks 1. The diameter ɸD1 of the large end of the initial tube blank 1 is ɸ295mm, the wall thickness is 10mm, the diameter ɸD2 of the small end is ɸ125mm, the wall thickness t1 is 14mm, and the inner wall size h×b of the rectangular cross section at the L position is 107mm×92mm. It is inserted into the upsetting mandrel 7 from both sides to form the initial tube blank 1 assembly, and the outer surface and the arc surface of the large diameter part of the upsetting mandrel 7 are consistent with the inner wall of the corresponding part of the initial tube blank 1. The diameter ɸD3 of the large end of the upsetting mandrel 7 is ɸ27 4.8mm, the diameter of the small end ɸd3 is ɸ77mm; the mold 6 includes: a base 6-1, a spring 6-2, a screw 6-3, a retaining ring 6-4, an upper clamping die 6-5 and a lower clamping die 6-6; the inner diameter of the retaining ring 6-4 is ɸ125.3mm, the retaining ring 6-4 slides in the base 6-1, and the local thickening of the tube blank 2 is formed on a three-way hydraulic press; the lower clamping die 6-6 of the mold 6 is fixed on the workbench of the hydraulic press, the upper clamping die 6-5 is fixed on the main slide of the hydraulic press, and the bases 6-1 on the left and right sides are respectively fixed on the horizontal slides of the hydraulic press. The assembly is placed in the lower clamping die 6-6, and the intermediate frequency annealing equipment is used to heat the part of the initial tube blank 1 where the shaft head is to be thickened to 900℃~1000℃. The main slide of the hydraulic press moves downward to drive the upper clamping die 6-5 to press the initial tube blank 1. The horizontal slide of the hydraulic press drives the base 6-1 and the retaining ring 6-4 to move synchronously toward the center. During this process, the end of the upsetting mandrel 7 is inserted into the hole of the base 6-1 for guidance. The retaining ring 6-4 first reaches the part to be thickened, and the left and right bases 6-1 upset the shaft head at the end of the initial tube blank 1. During upsetting, the inner hole wall of the retaining ring 6-4 contacts and rubs with the outer wall of the end of the initial tube blank 1. It no longer moves to prevent the end of the initial tube blank 1 from bulging outward. At the end of upsetting, the horizontal slider of the hydraulic press drives the left and right bases 6-1 to move outward at the same time. The base 6-1 drives the protective ring 6-4 to move outward and away from the initial tube blank 1 through the screw 6-3. The main slider of the hydraulic press drives the upper clamping die 6-5 to move upward. After the initial tube blank 1 assembly is taken out, the downsetting mandrel 7 is disassembled, and finally a locally thickened tube blank 2 with an end shaft head with an unchanged outer diameter and a reduced inner diameter is obtained. At the same time, in the process of the horizontal slider of the hydraulic press driving the left and right bases 6-1 to move outward, the protective ring 6-4 is reset by the spring 6-2.

[0034] Step 2) forming the stepped shaft head tube blank 4, as shown in FIG. Figures 5-10 As shown:

[0035] The locally thickened tube blank 2 is inserted into the spinning mandrel 8 to form a locally thickened tube blank 2 assembly. The diameter of the large end ɸD4 of the spinning mandrel 8 is ɸ274.8mm, and the diameter of the small end ɸd4 is ɸ77mm. The outer surface and arc surface of the large diameter part of the spinning mandrel 8 are consistent with the inner wall of the locally thickened tube blank 2. The middle part of the spinning mandrel 8 is a square cross-section with a size of 107.1mm~92mm, which has a small interference fit with the inner wall of the square arm of the locally thickened tube blank 2. The fillet radius Ra of the small diameter end of the spinning mandrel 8 is R15mm, and the reducing wheel 9 is a discus shape with a discus edge. The corner radius Rb is R13mm, the shoulder wheel 10 is cylindrical, and the fillet Rc between the cylindrical surface and the bottom surface is R5mm. The locally thickened tube blank 2 end shaft head reduction and shoulder forming are carried out on the spinning machine. The large end of the locally thickened tube blank 2 assembly with the set spinning mandrel 8 is placed in the main shaft hole of the spinning machine and clamped. The medium frequency heating is used to heat the locally thickened tube blank 2 end shaft head to 950℃~1050℃. The main shaft of the spinning machine drives the spinning mandrel 8 to rotate. The spinning mandrel 8 drives the locally thickened tube blank 2 to rotate through the square cross section. The spinning machine is driven The reducing wheel 9 and the shoulder wheel 10 move axially from the shaft head end side of the locally thickened tube blank 2 to the other side; the reducing wheel 9 is in front and the shoulder wheel 10 is behind, with a spacing of 15 mm. When the reducing wheel 9 spins the end of the locally thickened tube blank 2 to reduce the diameter, the spinning machine drives the shoulder wheel 10 to move radially so that it contacts the locally thickened tube blank 2 to balance the force generated by the reducing wheel 9; when the shoulder wheel 10 spins the shoulder of the locally thickened tube blank 2, the spinning machine drives the reducing wheel 9 to move radially so that it keeps in contact with the locally thickened tube blank 2. Contact to balance the force generated by the shoulder spinning wheel 10; the small-diameter end radius of the spinning mandrel 8 controls the forming size of the inner wall radius of the end of the locally thickened tube blank 2, and the diameter of the tube blank shaft head is reduced by spinning with the reducing wheel 9 to obtain the end reduced-diameter tube blank 3, and the stepped shaft head tube blank 4 is obtained by spinning with the forming shoulder spinning wheel 10. Its main dimensions are the shaft head outer diameter ɸD5 of ɸ89mm, the wall thickness t3 of 20mm, the shaft head inner wall radius Rd of 15mm, and the shoulder radius Re of R5mm. Depending on the situation, a gas spray gun is used to supplement heat during the spinning process.

[0036] Step 3) External surface hardening treatment:

[0037] The outer surface of the stepped shaft head tube blank 4 is subjected to heat treatment to increase the hardness, thereby obtaining a formed shaft head tube blank 5 with a high-hardness shaft head. Example

[0038] The difference between this embodiment and embodiment 1 is that the tube material of the initial tube blank 1 is Q345 or Q460;

[0039] Accordingly, when the initial tube blank 1 using the above-mentioned tube material is subjected to the outer surface hardening treatment in step 3), the specific process is as follows: after the stepped shaft head tube blank 4 produced in step 2) of Example 1 is cooled and the surface oxide scale is removed, a high-hardness material is built-up welded or laser-coated on the outer surface of the stepped shaft head tube blank 4 to obtain a formed shaft head tube blank 5 with a high-hardness shaft head.

[0040] The present invention has a simple process and high efficiency. When forming the locally thickened tube blank 2, it can effectively prevent the initial tube blank from becoming unstable and bulging. When forming the end diameter-reduced tube blank 3 and the stepped shaft head tube blank 4, it ensures that the inner fillet size of the shaft head is accurate.

Claims

1. A shaft head forming process for a combined drive axle housing with a shaft head, the overall process route is local thickening of the shaft head - shaft head spinning reduction and forming of the shaft shoulder - local surface hardening treatment of the shaft head, characterized in that: The steps include: Step 1) Partial thickening of the tube blank (2) Forming: The prefabricated tube formed by liquid expansion is split from the middle into two initial tube blanks (1), the initial tube blank (1) is inserted into an upsetting mandrel (7) from both sides, the portion of the end shaft head of the initial tube blank (1) to be thickened is heated to an appropriate temperature, and the end shaft head of the initial tube blank (1) is partially upset through a die (6), thereby obtaining a locally thickened tube blank (2) with a constant outer diameter of the end shaft head and a reduced inner diameter; Step 2) Forming the stepped shaft head tube blank (4): Inserting the locally thickened tube blank (2) into a spinning mandrel (8), locally heating the end shaft head of the locally thickened tube blank (2) to an appropriate temperature, reducing the diameter of the shaft head of the locally thickened tube blank (2) by spinning with a reducing wheel (9) to obtain an end reduced diameter tube blank (3), and spinning with a forming shoulder wheel (10) to obtain a stepped shaft head tube blank (4); In the step 2), the outer surface and arc surface of the large diameter portion of the spinning mandrel (8) are consistent with the inner wall of the locally thickened tube blank (2), the outer wall of the middle portion is consistent with the inner wall of the square arm of the locally thickened tube blank (2), the radius of the fillet Ra of the small diameter end is a cylinder with a radius of 18mm to 22mm, the reducing wheel (9) is a discus shape, the radius of the fillet Rb of the disc edge is 10mm to 15mm, and the shoulder wheel (10) is a cylindrical shape, and the fillet Rc between the cylindrical surface and the bottom surface is 4mm to 6mm; The reducing wheel (9) is in front and the shoulder wheel (10) is in the back; when the reducing wheel (9) spins and reduces the diameter of the end of the partially thickened tube blank (2), the spinning machine drives the shoulder wheel (10) to move radially so that it contacts the partially thickened tube blank (2) to balance the force generated by the reducing wheel (9); when the shoulder wheel (10) spins and forms the shoulder of the partially thickened tube blank (2), the spinning machine drives the reducing wheel (9) to move radially so that it remains in contact with the partially thickened tube blank (2) to balance the force generated by the shoulder wheel (10); the rounded corner of the small-diameter end of the spinning mandrel (8) controls the rounded corner forming size of the inner wall of the end of the partially thickened tube blank (2); Step 3) External surface hardening treatment: The outer surface of the stepped shaft head tube blank (4) is heat treated or coated with a high-hardness material to obtain a formed shaft head tube blank (5) with a high-hardness surface.

2. The shaft head forming process of the combined drive axle housing with a shaft head according to claim 1 is characterized in that: In the step 1), the initial tube blank (1) is formed by liquid expansion and pressing, and the cross-sections of the large end and the plate support position have reached the required size, and are cut into two pieces from the middle along the direction perpendicular to the axis of the tube; the cross-section of the large end of the initial tube blank (1) is a circular ring, the cross-section of the plate support position is a rectangular tube, and the cross-section of the small end is a circular ring. The large end and the small end and the plate support position are transitioned by an arc surface. The upsetting mandrel (7) is an axisymmetric rotation body, and the outer surface and the arc surface of the large diameter portion thereof coincide with the inner wall of the corresponding portion of the initial tube blank (1). The small diameter portion of the upsetting mandrel (7) is 20-22 mm smaller than the inner wall diameter of the end portion of the initial tube blank (1). The inner diameter of the guard ring (6-4) in the mold (6) is 0.2-0.4 mm larger than the outer diameter of the end portion of the initial tube blank (1). The guard ring (6-4) slides in the base (6-1) and is reset by a spring (6-2) and limited by a screw (6-3).

3. The shaft head forming process of the combined drive axle housing with a shaft head according to claim 2, characterized in that: The locally thickened tube blank (2) of step 1) is formed on a three-way hydraulic press. The lower clamping die (6-6) in the mold (6) is fixed on the press workbench, and the upper clamping die (6-5) is fixed on the main slide of the press and moves up and down with the main slide of the hydraulic press. The two initial tube blanks (1) are sleeved on the upsetting mandrel (7) and the arc surfaces on both sides of the middle of the upsetting mandrel (7) are matched with the inner wall of the initial tube blank (1). Then, the tube blanks are placed in the lower clamping die (6-6). The hydraulic press slide moves downward to drive the upper clamping die to press the initial tube blank (1). The left and right bases (6-1) are respectively fixed on the horizontal sliding template of the press. The horizontal sliding template of the machine drives the left and right bases (6-1) and the guard ring (6-4) to move toward the center. The guard ring (6-4) first reaches the part of the initial tube blank (1) to be thickened. The end of the upsetting mandrel (7) is inserted into the smaller inner hole of the base (6-1) to play a positioning and guiding role. The base (6-1) performs upsetting and thickening on the end of the initial tube blank (1). The inner hole wall of the guard ring (6-4) prevents the end of the initial tube blank (1) from bulging outward during upsetting and thickening. The outer wall of the end of the upsetting mandrel (7) limits the thickening amount of the end of the initial tube blank (1). The arc surfaces on both sides of the middle of the upsetting mandrel (7) support the inner wall of the initial tube blank (1) to prevent local instability.

4. The shaft head forming process of the combined drive axle housing with a shaft head according to claim 1 is characterized in that: When forming the stepped shaft head tube blank (4) in step 2), the locally thickened tube blank (2) is inserted into the spinning mandrel (8) and the arc surface of the spinning mandrel (8) is made to coincide with the inner wall of the locally thickened tube blank (2). Then, the large end of the spinning mandrel (8) is placed in the main shaft hole of the spinning machine, clamped and driven to rotate by the main shaft. The spinning machine drives the reducing wheel (9) and the shoulder wheel (10) to move axially from the shaft head end side of the locally thickened tube blank (2) to the other side.

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