Step-diameter reduction-hot spinning forming method for stepped tube blanks used in large-sized hydro-expansion formed automotive axle housings

Abstract

The present invention discloses a necking - hot spinning forming method for a stepped tube blank used for a large - size hydro - bulging formed automotive axle housing. First, free push - necking is performed on both ends of a seamless steel pipe to obtain a specific necked tube blank (11). The necked part at the right end of the heated necked tube blank (11) is heated. The tube blank (11) is clamped on a spinning machine, and forward spinning reduction and reverse spinning thinning are performed on the necked part on the right side of the tube blank (11). Then, reverse spinning reduction and thickening are performed on the right end of the tube blank (11), and the workpiece is unloaded and taken out. The direction of the tube blank (11) is reversed, and spinning is performed on the left part of the tube blank (11) after necking to obtain a stepped tube blank used for a hydro - bulging formed automotive axle housing. In the present invention, the increase value of the wall thickness of the workpiece is reduced by 15% - 25% compared with free push - necking, and the weight of the pipe fitting is reduced by 10% - 15%. When large - deformation reduction is performed on both sides of the tube blank, the middle part is not unstable, the ends are not warped, and no cracks occur. Moreover, the production efficiency is high, the manufacturing cost is low, and the forming quality is good.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic forming of metal pipe fittings, and particularly to a necking - hot spinning forming method for stepped tube blanks used in large - size hydro - bulging forming of automotive axle housings. Background Technique

[0002] Automotive axle housings belong to large - size variable - diameter special - shaped cross - section pipe parts, which are both load - bearing and force - transmitting parts in an automobile and require relatively high strength and stiffness. At present, casting methods and stamping - welding methods are mainly used to manufacture automotive axle housings. Castings have high strength and stiffness, but are material - consuming, energy - consuming and polluting during production. Stamping - welded parts are light in weight, but the weld performance is relatively low. The hydro - bulging forming method is a new method for manufacturing automotive axle housings. First, the two ends of a seamless steel pipe of a certain specification are necked down to prepare a stepped tube blank, then the middle part of the stepped tube blank is hydro - bulged, and finally, after filling it with liquid, it is pressed and formed with a die. The obtained automotive axle housing pipe fittings are integrally formed without welds, with high strength, stiffness and high material utilization rate.

[0003] The stepped tube blank for hydro - bulging forming of automotive axle housings has a large outer diameter in the middle straight - tube part and small outer diameters on both sides. The ratio of the outer diameter in the middle to the outer diameters on both sides is greater than 1.60, and there is a tapered transition between the middle straight - tube and the straight - tubes on both sides; the length dimension is relatively large, generally greater than 1450 mm.

[0004] The stepped tube blank for hydro - bulging forming of automotive axle housings can theoretically be prepared by necking or spinning methods. The overall forming method of a seamless - welded axle housing for heavy - duty trucks disclosed in Chinese Patent (CN201310191336.6) performs multi - pass large - deformation free push - compression necking on both ends of the seamless steel pipe (the ratio of the outer diameters of the tube blank before and after necking is generally 1.6 - 2.0) to obtain a stepped tube blank. However, the wall thickness of the tube blank increases by more than 50% after necking, resulting in a large weight of the necked - down pipe fitting, and warping at the ends and easy axial cracking. The tube - blank double - side reverse - core - axis push - compression necking die and process disclosed in Chinese Patent (CN201310191757.9) first places a core - axis inside the tube blank before necking. While using a necking die to push - compress the two ends of the tube blank from the outside to the inside, the core - axis placed inside the tube blank moves from the inside to the outside. This method solves to a certain extent the problems of large wall - thickness increase value and end warping after necking, but the middle part of the tube blank is prone to instability during the necking forming process, and it is difficult to remove the die after necking, and the tube blank is easily locked between the necking die and the core - axis.

[0005] The Chinese patent (CN201710538600.7) discloses a combination die for high-precision pipe reduction spinning. It is mainly composed of a fixed core die, a movable core die, a transition ring and a tail top plate placed inside the tube blank. The movable core die is tightly sleeved outside the fixed core die, and the fixed core die and the tail top plate clamp the movable core die through the transition ring. This combination die is suitable for the diameter reduction spinning of stepped tube blanks with large outer diameters at both ends and small outer diameters in the middle. The spinning process is relatively stable, and the quality of the pipe fittings after spinning is good. The Chinese patent (CN201010288774.0) discloses a method for hot spinning of a seamless gas cylinder with a forward rotary wheel. First, heat the steel pipe closing section (short length) to 920-1050℃, perform 6-7 passes of semi-ellipsoidal forward sealing spinning on the steel pipe closing section, and then perform 3-4 passes of bottom thickening spinning on the obtained semi-ellipsoidal head, and finally perform finishing spinning on the head surface.

[0006] The stepped tube blank used for bulging and forming automobile bridge shells has a large outer diameter in the middle and small outer diameters on both sides, and a large length. It is impossible to use the core mold structure in Chinese patent CN201710538600.7. If the content disclosed in Chinese patent CN201010288774.0 is adopted, it only relies on the external spinning wheel for large deformation and diameter reduction forming, which requires multiple spinning passes, has a long forming time and high manufacturing cost, and it is difficult to ensure the wall thickness requirements and forming quality of the tube blank. The surface will be uneven after large deformation spinning. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a step-shaped tube blank reduction-hot spinning forming method for large-size expansion and forming automobile axle housings. The wall thickness increase of the product of the invention is reduced by 15%~25% compared with the free push reduction, and the weight of the tube is reduced by 10%~15%; when the two sides of the tube blank undergo large deformation and diameter reduction, the middle part does not lose stability, the ends do not warp, and do not crack. In addition, the production efficiency is high, the manufacturing cost is low, and the forming quality is good.

[0008] To achieve the above object, the present invention provides a step-shaped tube blank reduction-hot spinning forming method for large-size expansion forming automobile axle housing, the method comprising the following steps:

[0009] Step 1: Select an initial seamless steel tube blank with an outer diameter of φd0, a wall thickness of t0, and a length of L0.

[0010] Step 2: Keep the length of the middle part L11 unchanged, and freely push and compress the two sides to obtain a specific reduced diameter tube blank. The outer diameter of the reduced diameter part is reduced to φd1=(0.60~0.75)φd0, and the wall thickness is increased to t1=(1.25~1.40)t0. There is a conical transition between the reduced diameter part and the initial tube blank in the middle, and the semi-cone angle c1=15~25°. There is a large arc transition between the straight arm part of the outer diameter φd1 of the tube blank and the conical surface after reduction, and the transition arc R1=40~100mm. The lengths of the reduced diameter parts on both sides are L12 and L13 respectively.

[0011] Step 3: Heat the reduced diameter part at the right end of the reduced diameter tube blank, and the heating temperature T=900~1050℃.

[0012] Step 4: Install the tube blank on the spinning machine, put the left end of the reduced diameter tube blank into the hollow spindle box of the spinning machine, use the spinning machine chuck blocks Ⅰ, Ⅱ and the clamping die blocks Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ installed thereon to clamp the right end part of the middle outer diameter φd0 of the reduced diameter tube blank, use the push rod to support the left end face of the tube blank, and place the stepped mandrel with a small diameter at the front section and a large diameter at the rear section into the inner cavity of the tube blank from the right end of the tube blank. The rotary wheel driving system drives the rotary wheels Ⅰ, Ⅱ on the front and rear sides of the tube blank to be placed at the transition between the reduced diameter part and the tapered part of the tube blank.

[0013] Step 5: The right side of the tube is spun down to reduce the diameter. The main shaft of the spinning machine drives the chuck blocks Ⅰ and Ⅱ to drive the tube to rotate after the diameter reduction. The spinning wheels Ⅰ and Ⅱ on the front and back sides of the tube are spun forward. At the same time, the mandrel driving system drives the stepped mandrel to move synchronously toward the outer end of the tube, so that the outer diameter of the right side of the tube is reduced from φd1 to φd2, φd2=(0.80~0.90)φd1, the wall thickness is increased from t1 to t2, t2=(1.05~1.15)t1, and the length is increased from L12 to L21; the inner surface of the tube after the diameter reduction contacts the outer surface of the large diameter section of the stepped mandrel, and the straight arm part of the outer diameter φd2 of the tube transitions with the conical surface after the positive spinning in a large arc, and the transition arc R2=100~160mm.

[0014] Step 6: The right side of the tube is reverse-spinned for thinning. The roller drive system drives the front and rear rollers Ⅰ and Ⅱ to perform reverse spinning from the outer end of the tube to the inside in the horizontal direction. At the same time, the mandrel drive system drives the stepped mandrel to move synchronously from right to left inside the tube, so that the inner diameter of the tube remains unchanged after the right side is positively spun and the outer diameter is reduced from φd2 to φd3, the wall thickness is reduced from t2 to t3, and the length is increased from L21 to L31, satisfying t3=(1.05~1.20)t0.

[0015] Step 7: The rotary wheel driving system quickly moves the front and rear rotary wheels Ⅰ and Ⅱ to the outer end of the tube blank, and at the same time the stepped mandrel moves outward, so that the rear section of the stepped mandrel with a large diameter is moved out of the tube blank, and the front section with a small diameter is located in the inner cavity of the tube blank.

[0016] Step 8: Reverse spinning and necking-down with wall thickness increasing at the right end of the tube blank. The spinning wheel drive system drives the front and rear spinning wheels to perform reverse spinning from the outer end of the tube blank inward, so that the outer diameter of the part with a length of L42 at the right end of the tube blank is necked down from φd3 to φd4, where φd4 = (0.80 - 0.90)φd3, and the wall thickness increases from t3 to t4, where t4 = (1.05 - 1.15)t3. A tapered transition is formed between the part with an outer diameter of φd4 at the end and the part with an outer diameter of φd3, with a half-cone angle c2 = 15 - 25°. A large arc transition is formed between the straight arm part with an outer diameter of φd4 at the end of the tube blank and the conical surface after reverse spinning, and the transition arc R3 = 40 - 100 mm.

[0017] Step 9: Taking the workpiece. The main shaft of the spinning machine stops rotating, the mandrel drive system drives the mandrel to withdraw, the front and rear spinning wheel systems drive the front and rear spinning wheels Ⅰ and Ⅱ to radially withdraw, the clamping die segments Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ release the clamped tube blank, the ejector rod drive system drives the ejector rod to move to the right, eject the tube blank, and unload and take the workpiece.

[0018] Step 10: For the left part of the tube blank after necking-down, perform according to Steps 3 - 9 to complete the spinning process of the left part of the necked-down tube blank.

[0019] When the spinning wheels Ⅰ and Ⅱ perform forward spinning and necking-down, the ratio f1 of the axial feed speed to the spindle speed is 0.4 - 1.0 mm / r; when performing reverse spinning and wall thickness thinning, the ratio f2 of the axial feed speed of the spinning wheels Ⅰ and Ⅱ to the spindle speed is 0.1 - 0.5 mm / r; when performing reverse spinning and necking-down with wall thickness increasing, the ratio f3 of the axial feed speed of the spinning wheels Ⅰ and Ⅱ to the spindle speed is 0.1 - 0.5 mm / r.

[0020] A spinning machine for the necking-down - hot spinning forming method of a stepped tube blank for a large-size hydroformed automotive axle housing, the spinning machine is composed of a spindle box, a base, a chuck drive system, a spinning wheel drive system, a mandrel drive system, a mandrel assembly, an ejector rod drive system and an ejector rod, wherein:

[0021] The spindle box is of a hollow structure, and a chuck drive system is arranged inside. The chuck drive system is composed of a main shaft, a pull rod, hinges Ⅰ and Ⅱ, a chuck, chuck segments Ⅰ and Ⅱ, and clamping die segments Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ. When the chuck drive system drives the pull rod to move longitudinally, it drives the chuck segments Ⅰ and Ⅱ and the clamping die segments Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ to move longitudinally along the wedge surface of the chuck through the hinges Ⅰ and Ⅱ, so that the clamping die segments Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, and Ⅵ clamp and release the tube blank, and when the chuck drive system rotates, it drives the clamped tube blank to rotate together.

[0022] The rotary wheel driving system is horizontally arranged on the front and rear sides, and is composed of rotary wheels I, II, longitudinal feed components I, II and radial feed components I, II that move laterally thereon. Rotary wheels I, II are installed on radial feed components I, II through bearings, and are driven by radial feed components I, II to achieve radial feeding and withdrawal. Longitudinal feed components I, II are driven by a motor through a screw or by a hydraulic cylinder to achieve longitudinal movement.

[0023] The mandrel driving system is driven by a motor through a gear rack mechanism to achieve longitudinal movement. The mandrel assembly consists of a mandrel, a shaft stop spring, a bearing, a bearing cover and a mandrel support shaft. The mandrel assembly is installed on the mandrel driving system through the mandrel support shaft.

[0024] The ejector driving system is driven by a motor through a lead screw or a hydraulic cylinder to achieve longitudinal movement. The ejector is driven by the ejector driving system to move longitudinally and is used to support the left end face of the tube blank. It can rotate synchronously with the tube blank during spinning and move to the right after spinning to eject the spun tube blank.

[0025] The clamping mold blocks I, II, III, IV, V, and VI are composed of 6 fan-shaped bodies with the same structure. The angle between the left and right sides of each fan-shaped body is 45°. The axial length L6 of the fan-shaped body is (1.00~1.20)φd0. The outer surface is a cylindrical surface with a diameter φD1= (1.30~1.50)φd0; the inner surface is composed of a cylindrical surface and a conical surface. The diameter of the cylindrical surface is φD2= (1.03~1.05)φd0. The semi-cone angle c3 of the conical surface is equal to the semi-cone angle c1 of the tube blank after diameter reduction. The axial length L61 of the conical surface is 10~15mm.

[0026] The mandrel is a stepped shaft with a small diameter at the front section and a large diameter at the rear section. The right end is provided with a stepped circular hole for installing a bearing and a mandrel support shaft. The mandrel can rotate synchronously with the tube blank during spinning. The diameter φdx1 and length Lx1 of the front section of the mandrel are determined according to the outer diameter φd4, wall thickness t4 and length L42 of the end of the stepped tube blank, diameter φdx1=φd4-(2.05-2.10)t4, Lx1=(1.10~1.20)L42, and the diameter φdx2 of the rear section is determined according to the outer diameter φd3 and wall thickness t3 after reverse spinning thinning, diameter φdx2=φd3-(2.05-2.10)t3, length Lx2=(0.80~1.20)φd3.

[0027] The beneficial effects of the present invention are as follows: after large-size expansion-pressing of stepped tube blanks for automobile axle housings, the wall thickness increase is reduced by 15% to 25% compared with the free push-pressing diameter reduction on the left and right sides; the weight of the tube is reduced by 10% to 15%; when large deformation diameter reduction is performed on both sides of the tube blank, the middle part does not lose stability, the ends do not warp, and there is no cracking; the production efficiency is high, the manufacturing cost is low, and the forming quality is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the initial seamless steel pipe of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0029] Figure 2 is the tube blank after reducing of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0030] Figure 3 is the schematic diagram of forward spinning with diameter reduction on the right side of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0031] Figure 4 is the tube blank after forward spinning with diameter reduction on the right side of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0032] Figure 5 is the tube blank after reverse spinning with wall thickness reduction on the right side of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0033] Figure 6 is the schematic diagram of reverse spinning with diameter reduction and wall thickness increase at the right end of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0034] Figure 7 is the tube blank after reverse spinning with diameter reduction and wall thickness increase at the right end of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0035] Figure 8 is the preparation of stepped tube blanks by the reducing - hot spinning forming method for large - size stepped tube blanks;

[0036] Figure 9 is the front view of the clamping die segments for hot spinning of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0037] Figure 10 is the left view of the clamping die segments for hot spinning of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0038] Figure 11 is the mandrel assembly for hot spinning of the reducing - hot spinning forming method for large - size stepped tube blanks;

[0039] Figure 12 is the stepped mandrel for hot spinning of the reducing - hot spinning forming method for large - size stepped tube blanks.

[0040] In the above-mentioned drawings, 1. headstock, 2. ejector rod, 3. main shaft, 4. draw bar, 5, 5'. hinge I, II, 6, 6'. screw I, II, 7, 7'. screw III, IV, 8. chuck, 9a, 9b. chuck segments I, II, 10a, 10b, 10c, 10d, 10e, 10f. clamping die segments I, II, III, IV, V, VI, 11. tube blank, 12, 12'. spinning wheels I, II, 13, 13'. spinning wheel radial feed assemblies I, II, 14. mandrel support shaft, 15, 15'. screw V, VI, 16, 16'. spinning wheel longitudinal feed assemblies I, II, 17. base, 18. mandrel drive system, 19. mandrel, 20. shaft retaining circlip, 21. bearing, 22. felt oil seal, 23. screw VII, 24. bearing cover. Detailed implementation mode Embodiment

[0041] For a stepped tube blank for a hydroforming bridge shell with an axle load of 11t, the necking - hot spinning forming method includes the following steps:

[0042] Step 1: Select an initial seamless steel tube blank 11 with an outer diameter φd0 = φ273mm, a wall thickness t0 = 12mm, and a length L0 = 1480mm. The initial seamless steel tube blank is as Figure 1 shown.

[0043] Step 2: Keep the part with a length of L11 = 622mm in the middle unchanged, and perform free push - pull necking on both sides to obtain a specific necked tube blank 11. The outer diameter of the necked part is reduced to φd1 = φ200mm and the wall thickness is increased to t1 = 15.1mm. There is a tapered transition between the necked part and the initial tube blank 11 in the middle, with a half - cone angle c1 = 20°. There is a large - arc transition between the straight - arm part with an outer diameter of φ200mm of the tube blank 11 and the tapered surface after necking, with a transition arc R1 = 50mm. The lengths of the necked parts on both sides are L12 = 352mm and L13 = 352mm respectively. After necking, the tube blank of the stepped tube blank necking - hot spinning forming method is as Figure 2 shown.

[0044] Step 3: Heat the necked part at the right end of the necked tube blank 11, and the heating temperature T = 900 - 1050°C.

[0045] Step 4: Mount the tube blank 11 on the spinning machine, place the left end of the reduced diameter tube blank 11 into the hollow spindle box 1 of the spinning machine, use the spinning machine chuck blocks I, II (9a, 9b) and the clamping die blocks I, II, III, IV, V, VI (10a, 10b, 10c, 10d, 10e, 10f) installed thereon to clamp the right end portion of the reduced diameter tube blank 11 with an outer diameter of φd0=φ273mm in the middle, use the push rod 2 to support the left end face of the tube blank 11, and place the stepped mandrel 19 with a small diameter at the front section and a large diameter at the rear section from the right end of the tube blank 11 into the inner cavity of the tube blank 11, and the rotary wheel driving system drives the rotary wheels I, II (12, 12′) on the front and rear sides of the tube blank 11 to be placed at the transition between the reduced diameter part and the tapered part of the tube blank 11.

[0046] Step 5: The right side of the tube blank 11 is subjected to positive spinning to reduce the diameter. The main shaft of the spinning machine drives the chuck blocks I and II (9a and 9b) to drive the tube blank 11 after the diameter reduction to rotate. The spinning wheels I and II (12 and 12′) located on the front and rear sides of the tube blank 11 are subjected to positive spinning. At the same time, the mandrel driving system 18 drives the stepped mandrel 19 to move synchronously toward the outer end of the tube blank 11, so that the outer diameter of the right side of the tube blank 11 is reduced from φd1=φ200mm to φd2=φ173mm, the wall thickness is increased from t1=15.1mm to t2=16.1mm, and the length is increased from L12=352mm to L21=381mm; the inner surface of the tube blank 11 after the diameter reduction contacts the outer surface of the large diameter section of the stepped mandrel 19, and the straight arm part of the tube blank 11 with an outer diameter of φ173mm transitions with the conical surface after positive spinning in a large arc, and the transition arc R2=120mm. Step-shaped tube blank reduction-hot spinning forming method The tube blank after right side reduction positive spinning is as follows Figure 4 shown.

[0047] Step 6: The right side of the tube 11 is reverse-spinned for thinning. The roller drive system drives the front and rear rollers Ⅰ and Ⅱ (12, 12′) to reverse-spin horizontally from the outer end of the tube 11 to the inside. At the same time, the mandrel drive system 18 drives the stepped mandrel 19 to move synchronously from right to left inside the tube 11, so that the inner diameter of the tube 11 after the right side is positively spun and reduced in diameter remains unchanged, and the outer diameter is reduced from φd2=φ173mm to φd3=φ170mm, the wall thickness is reduced from t2=16.1mm to t3=13.5mm, and the length is increased from L21=381mm to L31=453mm. Step-shaped tube reduction-hot spinning forming method After the right side is thinned and reverse-spinned, the tube is as follows Figure 5 shown.

[0048] Step 7: The rotary wheel driving system quickly moves the front and rear rotary wheels Ⅰ and Ⅱ (12, 12′) to the outer end of the tube blank 11, and at the same time, the stepped mandrel 19 moves outward, and the large-diameter rear section of the stepped mandrel 19 is moved out of the tube blank 11, and the small-diameter front section is located in the inner cavity of the tube blank 11.

[0049] Step 8: Reverse spinning and necking-down with wall thickness increasing at the right end of the tube blank 11. The spinning wheel drive system drives the front and rear spinning wheels I and II (12, 12') to perform reverse spinning with infeed from the outer end of the tube blank 11, reducing the outer diameter of the 150 mm long part at the right end of the tube blank 11 from φd3 = φ170 mm to φd4 = φ150 mm and increasing the wall thickness from t3 = 13.5 mm to t4 = 14 mm; a tapered transition is made between the part with an outer diameter of φd4 = φ150 mm at the end and the part with φd3 = φ170 mm, with a half-cone angle c2 = 20°; a large arc transition is made between the straight arm part with an outer diameter of φ150 mm at the end of the tube blank 11 and the conical surface after reverse spinning, and the transition arc R3 = 50 mm. The stepped tube blank prepared by the stepped tube blank necking-down - hot spinning forming method is as Figure 8 shown.

[0050] Step 9: Taking the workpiece. The main shaft 3 of the spinning machine stops rotating, the mandrel drive system 18 drives the mandrel 19 to withdraw, the front and rear spinning wheel systems drive the front and rear spinning wheels I and II (12, 12') to withdraw radially, the clamping die segments (10a, 10b, 10c, 10d, 10e, 10f) release the clamped tube blank 11, the ejector rod drive system drives the ejector rod 2 to move to the right, ejecting the tube blank 11, and unloading and taking the workpiece.

[0051] Step 10: Perform steps (3) - (9) on the left part of the tube blank 11 after necking-down to complete the spinning of the left part of the necked-down tube blank 11.

[0052] A spinning machine for the step-shaped tube blank reduction-hot spinning forming method for large-size expansion forming automobile bridge shells, the spinning machine is composed of a spindle box 1, a base 17, a chuck drive system, a rotary wheel drive system, a core rod drive system 18, a core rod assembly, a push rod drive system, and a push rod 2. The spindle box 1 is a hollow structure, and a chuck drive system is arranged inside. The chuck drive system is composed of a spindle 3, a pull rod 4, hinges Ⅰ, Ⅱ (5, 5'), a chuck 8, chuck blocks Ⅰ, Ⅱ (9a, 9b) and clamping mold blocks Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ (10a, 10b, 10c, 10d, 10e, 10f). When the chuck drive system drives the pull rod 4 to move longitudinally, it drives the hinges Ⅰ, Ⅱ (5, 5') to move longitudinally. The chuck blocks Ⅰ, Ⅱ (9a, 9b) and the clamping die blocks Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ (10a, 10b, 10c, 10d, 10e, 10f) move longitudinally along the wedge-shaped surface of the chuck 8, so that the clamping die blocks Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ (10a, 10b, 10c, 10d, 10e, 10f) clamp and release the tube blank 11, and when the chuck driving system rotates, the clamped tube blank 11 is driven to rotate together. The rotary wheel driving system is arranged horizontally on the front and rear sides, and is composed of rotary wheels I and II (12, 12'), longitudinal feed components (16, 16') and radial feed components I and II (13, 13') that move laterally thereon. The rotary wheels I and II (12, 12') are installed on radial feed components I and II (13, 13') through bearings, and are driven by radial feed components I and II (13, 13') to realize radial feeding and withdrawal. The longitudinal feed components I and II (16, 16') are driven by a motor through a lead screw or a hydraulic cylinder to realize longitudinal movement. The mandrel driving system 18 is driven by a motor through a gear rack mechanism to realize longitudinal movement. The mandrel assembly is composed of a mandrel 19, a shaft stop spring 20, a bearing 21, a bearing cover 24, a mandrel support shaft 14, etc. The mandrel assembly is installed on the mandrel driving system 18 through the mandrel support shaft 14. The ejector drive system is driven by a motor through a lead screw or by a hydraulic cylinder to achieve longitudinal movement. The ejector 2 is driven by the ejector drive system to move longitudinally and is used to support the left end surface of the tube blank 11. It can rotate synchronously with the tube blank 11 during spinning and move to the right after spinning to eject the spun tube blank 11.

[0053] The clamping mold blocks Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ (10a, 10b, 10c, 10d, 10e, 10f) for the spinning machine are composed of 6 fan-shaped bodies with the same structure. The angle between the left and right sides of each fan-shaped body is 45°. The axial length L6 of the fan-shaped body is 300mm. The outer surface is a cylindrical surface with a diameter φD1=φ380mm; the inner surface is composed of a cylindrical surface and a conical surface, the diameter of the cylindrical surface is φD2=φ276mm, the semi-cone angle c3 of the conical surface is equal to the semi-cone angle c1 of the tube blank after diameter reduction, c3=20°, and the axial length L61 of the conical surface is 15mm.

[0054] The mandrel 19 for the spinning machine is a stepped shaft with a small diameter at the front section and a large diameter at the rear section. The right end is provided with a stepped round hole for installing the bearing 21 and the mandrel support shaft 14. During spinning, the mandrel 19 can rotate synchronously with the tube blank 11. The diameter of the front section of the stepped mandrel 19 is φdx1 = φ143mm, Lx1 = 160mm, the diameter of the rear section is φdx2 = φ122mm, and the length Lx2 = 170mm.

Claims

1. A reducing - hot spinning forming method for stepped tube blanks used in large - size hydro - bulging formed automotive axle housings, characterized in that: The forming method comprises the following steps: Step 1: Select an initial seamless steel tube blank (11) with an outer diameter φd0, a wall thickness t0, and a length L0; Step 2: Keeping the length of the middle portion L11 unchanged, the two sides are freely pushed and reduced to obtain a specific reduced diameter tube blank (11), the outer diameter of the reduced diameter portion is reduced to φd1=(0.60~0.75)φd0, the wall thickness is increased to t1=(1.25~1.40)t0, the reduced diameter portion and the middle initial tube blank (11) are tapered, the semi-cone angle c1=15~25°, the straight arm portion of the outer diameter φd1 of the tube blank (11) and the tapered surface after the reduction are transitioned in a large arc, the transition arc R1=40~100mm, and the lengths of the reduced diameter portions on both sides are L12 and L13 respectively; Step 3: heating the right end of the reduced diameter tube (11) at a heating temperature of T = 900-1050°C; Step 4: Mounting a tube blank (11) on a spinning machine, placing the left end of the reduced diameter tube blank (11) into the hollow spindle box (1) of the spinning machine, using the spinning machine chuck blocks I and II (9a, 9b) and the clamping die blocks I, II, III, IV, V, VI (10a, 10b, 10c, 10d, 10e, 10f) mounted thereon to clamp the right end portion of the reduced diameter tube blank (11) with an outer diameter φd0 in the middle, using a push rod to support the left end surface of the tube blank (11), and inserting a stepped mandrel (19) with a small diameter at the front section and a large diameter at the rear section into the inner cavity of the tube blank (11) from the right end of the tube blank (11), and the rotary wheel driving system drives the rotary wheels I and II (12, 12′) at the front and rear sides of the tube blank (11) to be placed at the transition between the reduced diameter portion and the tapered portion of the tube blank (11); Step 5: The right side of the tube blank (11) is positively spun to reduce the diameter. The spinner main shaft drives the chuck blocks I and II (9a and 9b) to drive the tube blank (11) after the diameter reduction to rotate. The spinning wheels I and II (12 and 12') located on the front and rear sides of the tube blank (11) are positively spun. At the same time, the mandrel driving system (18) drives the stepped mandrel (19) to move synchronously toward the outer end of the tube blank (11), so that the outer diameter of the right side of the tube blank (11) is reduced from φd1 to φ d2, φd2=(0.80~0.90)φd1, the wall thickness increases from t1 to t2, t2=(1.05~1.10)t1, and the length increases from L12 to L21; the inner surface of the reduced tube blank (11) contacts the outer surface of the large diameter section of the stepped mandrel (19), and a large arc transition is formed between the straight arm portion of the outer diameter d2 of the tube blank (11) and the conical surface after forward spinning, and the transition arc R2=100~160mm; Step 6: The right side of the tube blank (11) is subjected to reverse spinning for thinning. The roller drive system drives the front and rear rollers I and II (12, 12′) to perform reverse spinning from the outer end of the tube blank (11) to the inside in a horizontal direction. At the same time, the mandrel drive system (18) drives the stepped mandrel (19) to move synchronously from right to left inside the tube blank (11), so that the inner diameter of the tube blank (11) after the right side is subjected to forward spinning for thinning remains unchanged, the outer diameter is reduced from φd2 to φd3, the wall thickness is reduced from t2 to t3, and the length is increased from L21 to L31, satisfying t3=(1.05~1.20)t0; Step 7: The roller drive system quickly moves the front and rear rollers Ⅰ and Ⅱ (12, 12') to the outer end of the tube blank (11). Meanwhile, the stepped mandrel (19) moves outward, moving the rear section with a large diameter of the stepped mandrel (19) out of the tube blank (11), and the front section with a small diameter is located inside the cavity of the tube blank (11). Step 8: Reverse spinning and diameter reduction with wall thickness increase are performed at the right end of the tube blank (11). The roller drive system drives the front and rear rollers Ⅰ and Ⅱ (12, 12') to perform reverse spinning by infeed from the outer end of the tube blank (11) inward, so that the outer diameter of the part with a length L42 at the right end of the tube blank (11) is reduced from φd3 to φd4, φd4 = (0.80 - 0.90)φd3 for transition, and the wall thickness is increased from t3 to t4, t4 = (1.05 - 1.15)t3. A tapered transition is made between the part with an outer diameter of φd4 at the end and the part with an outer diameter of φd3, and the half-cone angle c2 = 15 - 25°. A large arc transition is made between the straight arm part with an outer diameter of φd4 at the end of the tube blank (11) and the tapered surface after reverse spinning, and the transition arc R3 = 40 - 100 mm. Step 9: Take out the workpiece. The main shaft (3) of the spinning machine stops rotating. The mandrel drive system (18) drives the mandrel (19) to withdraw. The front and rear roller systems drive the front and rear rollers Ⅰ and Ⅱ (12, 12') to withdraw radially. The clamping die segments Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ (10a, 10b, 10c, 10d, 10e, 10f) release the clamped tube blank (11). The ejector rod drive system drives the ejector rod (2) to move to the right to eject the tube blank (11) for unloading and taking out the workpiece. Step 10: For the spinning of the left part of the tube blank (11) after diameter reduction, perform according to the above Steps 3 - 9 to complete the spinning of the left part of the reduced-diameter tube blank (11).

2. The necking - hot spinning forming method for stepped tube blanks used in large - size hydro - expansion formed automotive axle housings according to claim 1, characterized in that: When the rollers Ⅰ and Ⅱ (12, 12') perform forward spinning and diameter reduction, the ratio f1 of the axial feed speed to the rotational speed of the main shaft (3) is 0.4 - 1.0 mm / r; when performing reverse spinning and wall thickness reduction, the ratio f2 of the axial feed speed of the rollers Ⅰ and Ⅱ (12, 12') to the rotational speed of the main shaft (3) is 0.1 - 0.5 mm / r; when performing reverse spinning and diameter reduction with wall thickness increase, the ratio f3 of the axial feed speed of the rollers Ⅰ and Ⅱ (12, 12') to the rotational speed of the main shaft (3) is 0.1 - 0.5 mm / r.

3. A spinning machine for the stepped tube blank necking-thermal spinning forming method of a large-sized expanded and pressed formed automotive axle housing according to any one of claims 1-2, characterized in that: The spinning machine consists of a main shaft box (1), a base (17), a chuck drive system, a roller drive system, a mandrel drive system (18), a mandrel assembly, an ejector rod drive system, and an ejector rod (2), where:[[]] The main shaft box (1) has a hollow structure, and a chuck drive system is arranged inside. The chuck drive system comprises a main shaft (3), a pull rod (4), hinges I and II (5, 5'), a chuck (8), chuck blocks I and II (9a, 9b) and clamping mold blocks I, II, III, IV, V, and VI (10a, 10b, 10c, 10d, 10e, 10f). When the chuck drive system drives the pull rod (4) to move longitudinally, the chuck blocks I and II (10a, 10b, 10c, 10d, 10e, and 10f) are driven by the hinges I and II (5, 5'). 9a, 9b) and the clamping die blocks I, II, III, IV, V, VI (10a, 10b, 10c, 10d, 10e, 10f) move longitudinally along the wedge-shaped surface of the chuck (8), so that the clamping die blocks I, II, III, IV, V, VI (10a, 10b, 10c, 10d, 10e, 10f) clamp and release the tube blank (11), and when the chuck driving system rotates, the clamped tube blank (11) is driven to rotate together; The rotary wheel driving system is horizontally arranged at the front and rear sides, and is composed of rotary wheels I, II (12, 12'), longitudinal feed components I, II (16, 16') and radial feed components I, II (13, 13') moving laterally thereon. The rotary wheels I, II (12, 12') are mounted on the radial feed components I, II (13, 13') through bearings, and are driven by the radial feed components I, II (13, 13') to realize radial feeding and withdrawal. The longitudinal feed components I, II (16, 16') are driven by a motor through a lead screw or by a hydraulic cylinder to realize longitudinal movement. The mandrel drive system (18) is driven by a motor through a gear rack mechanism to achieve longitudinal movement, the mandrel assembly is composed of a mandrel (19), a shaft stop spring (20), a bearing (21), a bearing cover (24) and a mandrel support shaft (14), and the mandrel assembly is mounted on the mandrel drive system (18) through the mandrel support shaft (14); The push rod driving system is driven by a motor through a lead screw or by a hydraulic cylinder to achieve longitudinal movement. The push rod (2) is driven by the push rod driving system to move longitudinally and is used to support the left end surface of the tube blank (11). During spinning, it rotates synchronously with the tube blank (11) and moves to the right after spinning to eject the spun tube blank (11).

4. The spinning machine for the stepped tube blank necking-thermal spinning forming method for large-sized hydroformed automotive axle housings according to claim 3, characterized in that: The clamping mold blocks I, II, III, IV, V, and VI (10a, 10b, 10c, 10d, 10e, and 10f) are composed of 6 fan-shaped bodies with the same structure. The angle between the left and right sides of each fan-shaped body is 45°. The axial length of the fan-shaped body is L6=(1.00~1.20)φd0. The outer surface is a cylindrical surface with a diameter φD1=(1.30~1.50)φd0. The inner surface is composed of a cylindrical surface and a conical surface. The diameter of the cylindrical surface is φD2=(1.03~1.05)φd0. The semi-cone angle c3 of the conical surface is equal to the semi-cone angle c1 of the tube blank (11) after diameter reduction. The axial length of the conical surface is L61=10~15mm.

5. The spinning machine for the reducing - hot spinning forming method of the stepped tube blank for large - size hydro - bulging forming of automotive axle housing according to claim 3, characterized in that: The mandrel (19) is a stepped shaft with a smaller diameter at the front section and a larger diameter at the rear section. The right end is provided with a stepped round hole for installing a bearing (21) and a mandrel support shaft (14). During spinning, the mandrel (19) rotates synchronously with the tube blank (11). The diameter φdx1 and length Lx1 of the front section of the mandrel (19) are determined according to the outer diameter φd4, wall thickness t4 and length L42 of the end of the stepped tube blank (11). The diameter φdx1 = φd4 - (2.05 - 2.10)t4, and Lx1 = (1.10 to 1.20)L42. The diameter φdx2 of the rear section is determined according to the outer diameter φd3 and wall thickness t3 after reverse spinning and thinning. The diameter φdx2 = φd3 - (2.05 - 2.10)t3, and the length Lx2 = (0.80 to 1.20)φd3.

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