A method of manufacturing a heavy truck axle housing

Abstract

The application provides a heavy truck axle housing manufacturing method, which comprises the following steps: selecting a ladder-shaped pipe blank, firstly performing axial annular material supplementing pre-expanding to obtain a pre-expanding pipe blank with an upper flat side, a lower side and front and rear convex sides, the wall thickness of the upper flat side is almost not thinned, and the wall thickness gradually decreases from the upper side to the lower side along the annular direction; and performing final expanding after annealing to obtain an axle housing pipe, the upper side of the pre-expanding pipe blank becomes a front flat surface with a bell-shaped additional front cover, the front and rear sides are shaped into a H-shaped side beam, the lower side becomes a semispherical rear oil cover, and the wall thickness of the front flat surface and the side beam is increased. The pre-expanding die is composed of left and right pressing heads, left and right sliding dies, an upper control die and a lower control die, the cavity axial width of the upper flat area of the upper control die is greater than that of the front and rear convex sides. The manufactured heavy truck axle housing is free of welds and oil leakage, the wall thickness of the front flat surface and the side beam of the axle housing is large, the bending and torsion resistance is improved, the diameter expansion rate is large during hydraulic expanding, the wall thickness thinning rate is small, the forming quality is good, and the material utilization rate is high.

Description

Technical Field

[0001] This application belongs to the field of automobile manufacturing technology, and in particular relates to a method for manufacturing a heavy-duty truck axle housing. Background Technology

[0002] The drive axle housing is one of the main load-bearing components of a car. It serves as the assembly base for the final drive, differential, and half-shafts. Its primary function is to support the weight of the vehicle, withstand the road reaction forces and torques transmitted from the wheels, and then transmit these forces to the chassis or body via the suspension. Its performance directly affects the safety and reliability of the transport vehicle, and it must possess sufficient strength and rigidity while meeting the trend towards lightweight automotive manufacturing.

[0003] Heavy truck axle housings are large in size and subject to complex stresses. Figure 1 This is a front view of the rear drive axle housing assembly of a heavy-duty truck. The axle housing consists of a circular tube area, a straight boom area, and an axle housing area from both ends to the middle. A leaf spring seat is welded to the upper side of the straight boom area to transmit vertical force. The axle housing area has side beams on the upper and lower sides, with a maximum cross-sectional height of 560mm in the middle. During installation, an upper thrust seat is welded to the upper side beam, and a lower thrust seat is welded to the lower side at the junction of the straight boom area and the axle housing area to transmit the longitudinal and lateral forces of the heavy-duty truck during driving. Figure 2 This is a side view of the rear drive axle housing assembly of a heavy-duty truck. The rear axle housing area has a rear oil cap. A reinforcing ring is welded to the front face at the stop, after which a heavy-duty main reducer is assembled. During operation, longitudinal and lateral forces are transmitted to the front face through the reinforcing ring. Therefore, the heavy-duty truck axle housing, especially in the axle housing section, particularly the side beams and the front face area, must have a significant wall thickness to ensure the product can withstand the combined effects of vertical, longitudinal, and lateral forces.

[0004] Heavy-duty truck axle housings are primarily manufactured using stamping and welding methods. Figure 1 The heavy-duty truck axle housing is a stamped and welded axle housing, composed of an upper axle housing sheet, a lower axle housing sheet, four triangular pads, a rear oil cap, and a reinforcing ring. The upper and lower axle housing sheets are stamped from steel plates of equal wall thickness. To ensure lightweighting, the rear oil cap is made from a thinner steel plate than the upper and lower axle housing sheets. The stamping and welding method results in long welds on the heavy-duty truck axle housing, making it prone to oil leaks at the welds of the rear oil cap and triangular pads. Furthermore, in practical engineering applications, the thin wall thickness at the connection between the rear oil cap and the upper and lower axle housing sheets leads to low rigidity, internal stress concentration, weak load-bearing capacity, and a high risk of failure. Additionally, the material utilization rate is low during production.

[0005] Chinese Patent [201310019329.8] discloses a method for integrally forming a seamless axle housing for light and medium-duty trucks. It uses a seamless steel round tube, reduces the diameter at both ends, performs two hydraulic expansions on the middle of the tube blank, and then reduces the diameter at both ends again to obtain an axisymmetric pre-expanded tube blank. The pre-expanded tube blank is filled with liquid and pressed using a mold to obtain a semi-finished axle housing with a hemispherical rear oil cap and an additional front cover. The additional front cover is then removed to obtain the final axle housing product. While this method produces a seamless axle housing, it has several drawbacks: ① The pre-expanded tube blank is axisymmetric, and hydraulic expansion only involves axial feeding. Achieving a large expansion ratio requires two hydraulic expansions. The wall thickness is uniform along the circumferential direction on the same cross-section of the axle housing, resulting in thinner walls and poorer rigidity at the high-load front plane and side beams; ② The removed additional front cover has a large mass.

[0006] Chinese patent [201310191336.6] discloses a method for integral forming of a weldless axle housing for heavy-duty trucks. It uses a seamless steel round tube, compresses both ends with a mandrel, and then uses a mold with an approximately circular cross-section to hydraulically expand the middle of the tube blank. The ends are then reduced in diameter to obtain a pre-expanded tube blank with an approximately axisymmetric shape of revolution. The pre-expanded tube blank is filled with liquid, and a mold is used to press it from top to bottom and front to back to obtain a semi-finished axle housing without an additional front cover. The rear oil cover is then shaped to obtain the final axle housing product. While this method produces a weldless integral axle housing for heavy-duty trucks, it has several drawbacks: ① The pre-expanded tube blank is approximately axisymmetric, and hydraulic expansion only provides axial material, resulting in a large wall thickness reduction rate. In practical applications, a diameter expansion rate exceeding 50% can easily lead to cracking; ② The wall thickness is uniform along the circumferential direction on the same cross-section of the axle housing, with thinner walls at the front plane and side beams where the load is high, resulting in poor rigidity; ③ Wrinkles exist on the front plane during pressing, leading to poor forming quality. Summary of the Invention

[0007] 1. Technical problems to be solved

[0008] Based on the problems of heavy-duty truck axle housings, axle housings manufactured by stamping and welding have long welds, are prone to oil leakage, have thin walls at the connection between the rear oil cap and the upper and lower axle housing plates, have weak load-bearing capacity, are prone to failure, and have low material utilization. When manufacturing heavy-duty truck axle housings using the existing hydraulic bulging method, the pre-bulged tube blank is an approximately axisymmetric rotating body shape. Hydraulic bulging only provides axial material feeding, resulting in a large wall thickness reduction rate, easy expansion and cracking. The wall thickness is the same along the circumferential direction on the same cross section of the axle housing, and the wall thickness is thin at the front plane and side beams where the load is high, resulting in poor rigidity. The front plane forming quality is also poor during pressing. This application provides a method for manufacturing heavy-duty truck axle housings.

[0009] 2 Technical Solution

[0010] To achieve the above objectives, this application provides a method for manufacturing a heavy-duty truck axle housing, based on the main parameters of the heavy-duty truck axle housing, namely the height d of the middle section of the axle housing. mThe rectangular cross-section height h1 and width b1 of the straight arm sections on both sides of the bridge housing, and the outer diameter d of the circular tubes at both ends of the bridge housing. e The hydraulic bulging process steps are as follows: h2 is the height of the rear oil cover apex from the center axis, and d1 is the maximum diameter at the connection between the rear oil cover and the axle housing body.

[0011] (1) A stepped tube blank is selected, which consists of a circular end area, a first transition area, a straight arm area, a second transition area, and an bulging area connected sequentially from both ends to the middle. The outer diameter of the circular end is d. e The wall thickness of the round end is t2, and the outer diameter of the straight arm region is d. s The wall thickness of the straight arm region is t1, the outer diameter of the bulging region is d0, and the wall thickness of the bulging region is t0.

[0012] (2) Pre-expansion: The two ends of the stepped tube blank are sealed and filled with liquid using a pre-expansion mold. The stepped tube blank is then subjected to axial and circumferential feeding hydraulic expansion to obtain a pre-expansion tube blank. The middle part of the pre-expansion tube blank includes an upper side, a front side, a lower side and a rear side connected in sequence. The upper side is flat, and the lower side, the front side and the rear side are all convex. The wall thickness of the flat part of the upper side is not reduced, and the wall thickness gradually decreases from the upper side to the lower side along the circumferential direction.

[0013] The distance h from the axis to the flattened portion on the upper side of the pre-expanded tube blank is (0.30~0.40)d. m The maximum radius of curvature R of the front convex portion b = (0.43~0.53)d m The maximum radius of curvature R of the rear convex portion b = (0.43~0.53)d m The maximum radius of curvature R of the lower convex portion a = (0.45~0.55)d m The maximum diameter expansion rate can reach 85%;

[0014] The wall thickness t at the outermost point on the front side of the pre-expanded tube blank b = (0.89~0.95)t0, where t is the wall thickness at the outermost point on the rear side of the pre-expanded tube blank. b = (0.89~0.95)t0, where t is the wall thickness at the lowest point on the lower side. a = (0.84~0.90)t0, no cracking under large expansion ratio;

[0015] The pre-expansion mold mainly includes an upper control mold, a lower control mold, a left sliding mold, a right sliding mold, a left pressure head, and a right pressure head. The axial width of the cavity on the upper flat part of the upper control mold is greater than that of the convex cavities on the front and rear sides, ensuring good formability. The axial width of the lower control mold is equal to that of the convex cavities on the front and rear sides of the upper control mold.

[0016] The cavities of the left and right sliding molds are the same, and the axial width of the upper flat part cavity is smaller than that of the front and rear and lower convex parts cavity.

[0017] (3) The middle expansion portion of the pre-expanded tube blank is subjected to medium-frequency annealing at a temperature of 800℃~900℃;

[0018] (4) Final expansion: Low-pressure liquid is first filled into the pre-expanded tube blank using a mold, and then the pre-expanded tube blank is pressed and formed from four directions: top, bottom, front and back to obtain the bridge shell tube. The upper side of the pre-expanded tube blank becomes a front plane with a gong-shaped additional front cover, the front and back sides are formed into a cross-section of the cross-section of the side beam, and the lower side becomes a hemispherical rear oil cover. The wall thickness at the front plane and side beam is increased compared to the pre-expanded tube blank, and the wall thickness at the highest point of the rear oil cover is not reduced, which improves the bending and torsional stiffness of the bridge shell part.

[0019] (5) Remove the smaller additional front cover to obtain a weld-free heavy truck axle housing.

[0020] Another embodiment provided in this application is as follows: the axial width of the convex portion on the front and rear sides of the upper control mold is w1 = (100~140) mm, the maximum axial width of the cavity of the flat portion on the upper side of the upper control mold is w2, which satisfies w2 = (1.2~1.5)w1, the upper control mold transitions from the upper side to the lower side in a planar or curved form along the circumferential direction to ensure that there are no extrusion marks when the flat portion on the upper side of the pre-expanded tube blank is formed; the axial width of the lower control mold is w1.

[0021] Another embodiment provided in this application is: the height h3 of the apex of the gong-shaped additional front cover from the axis is (0.40~0.52)h2, the maximum diameter d2 of the connection between the gong-shaped additional front cover and the front plane is (0.60~0.70)d1, and less material is removed.

[0022] 3. Beneficial effects

[0023] Compared with the prior art, the beneficial effects of the heavy truck axle housing manufacturing method provided in this application are as follows:

[0024] The heavy-duty truck axle housing manufacturing method provided in this application results in a seamless, integrally formed axle housing. This completely eliminates the problems of weld cracking and oil leakage, as well as failure at the rear oil cap.

[0025] The heavy-duty truck axle housing manufacturing method provided in this application produces a heavy-duty truck axle housing with a large load-bearing front plane and thick side beam walls, which improves the bending and torsional resistance while ensuring the product is lightweight.

[0026] The heavy-duty truck axle housing manufacturing method provided in this application has a large expansion ratio and a small wall thickness reduction ratio during hydraulic bulging, resulting in good forming quality and high material utilization. Attached Figure Description

[0027] Figure 1 This is a front view of a stamped and welded axle housing for a heavy-duty truck.

[0028] Figure 2 This is a side view of a stamped and welded axle housing for a heavy-duty truck.

[0029] Figure 3 This is a cross-sectional schematic diagram of the trapezoidal tube blank of this application;

[0030] Figure 4 This is a longitudinal cross-sectional schematic diagram of the pre-expanded tube blank and mold of this application;

[0031] Figure 5 This is a schematic cross-sectional view of the pre-expanded tube blank of this application;

[0032] Figure 6 This is a schematic diagram of the pre-expansion upper control mold structure of this application;

[0033] Figure 7 This is a schematic diagram of the pre-expansion control module structure of this application;

[0034] Figure 8 This is a front view of the final bulging rear axle housing semi-finished product of this application;

[0035] Figure 9 This is a top view cross-sectional schematic diagram of the semi-finished rear axle housing with final bulging shape according to this application;

[0036] Figure 10 This is a schematic diagram of the front view of the semi-finished rear axle housing after final bulging, as per this application.

[0037] Figure 11 This is a top view sectional diagram of the bridge shell of this application.

[0038] In the diagram: 1-Leaf spring seat, 2-Axle housing plate, 3-Upper thrust seat, 4-Side beam, 5-Triangular pad, 6-Lower axle housing plate, 7-Reinforcing ring, 8-Stop, 9-Lower thrust seat, 10-Rear oil cover, 11-Round end area, 12-Straight arm area, 13-Expansion area, 14-Second transition area, 15-First transition area, 16-Left sliding mold, 17-Upper control mold, 18-Right sliding mold, 19-Right pressure head, 20-Lower control mold, 21-Pre-expansion tube blank, 22-Left pressure head, 23-Additional front cover. Detailed Implementation

[0039] In the following, specific embodiments of this application will be described in detail with reference to the accompanying drawings. Based on these detailed descriptions, those skilled in the art will be able to clearly understand and implement this application. Without departing from the principles of this application, features from various embodiments can be combined to obtain new implementations, or certain features from some embodiments can be substituted to obtain other preferred implementations.

[0040] See Figures 1-11 The heavy-duty truck axle housing manufacturing method provided in this application uses a stepped tube blank. First, axial and circumferential feeding pre-expansion is performed to obtain a pre-expansion tube blank with a flat upper side and outward convex lower and front / rear sides. The wall thickness of the flat upper part remains almost constant, while the wall thickness gradually decreases from the top to the bottom along the circumferential direction. After annealing, a low-pressure liquid is first filled into the pre-expansion tube blank using a final expansion mold. Then, the pre-expansion tube blank is pressed and shaped from four directions (top, bottom, front, and rear) to obtain the axle housing component. The upper side of the pre-expansion tube blank becomes a front plane with a gong-shaped additional front cover 18, the front and rear sides are formed into U-shaped side beams, and the lower side becomes a hemispherical rear oil cover. The wall thickness at the front plane and side beams increases. The pre-expansion mold consists of a left pressure head 22, a right pressure head 19, a left sliding mold 16, a right sliding mold 18, an upper control mold 17, and a lower control mold 20. The axial width of the cavity in the flat upper region of the upper control mold 17 is greater than the outward convex cavities on the front and rear sides.

[0041] Example

[0042] The main parameters of a heavy-duty truck axle housing with an axle load of 12 tons include: the height d of the intermediate section of the axle housing. m =530mm, the rectangular cross-section height h1=160mm and width b1=158mm of the straight arm section on both sides of the bridge housing, and the outer diameter d of both ends of the bridge housing. e =φ170mm, height h2 from the apex of the rear oil cap to the center axis = 252mm, maximum diameter d1 at the connection between the rear oil cap and the axle housing body = φ454mm. The process steps of the heavy-duty truck axle housing hydraulic bulging method of this embodiment are as follows:

[0043] (1) Select a stepped tube blank, such as Figure 3 As shown, from both ends to the middle, there are a circular end region 11, a first transition region 15, a straight arm region 12, a second transition region 14, and an bulging region 13 connected in sequence. The outer diameter of the circular end region 11 is d. e =φ170mm, the wall thickness of the round end region 11 is t2 = 16mm, and the outer diameter of the straight arm region 12 is d. s =φ186mm, the wall thickness of the straight arm region 12 is t1=15mm, the outer diameter of the bulging region 13 is d0=φ299mm, the wall thickness of the bulging region 13 is t0=11mm;

[0044] (2) Pre-expansion forming: A pre-expansion forming mold is used to seal both ends of the stepped tube blank and fill it with liquid. Axial circumferential feeding hydraulic expansion is then performed on the expansion zone of the stepped tube blank to obtain a pre-expansion tube blank. The pre-expansion tube blank includes an upper side, a front side, a lower side, and a rear side connected sequentially in the middle. The upper side is flat, while the lower side, the front side, and the rear side are all convex. The wall thickness of the flat portion of the upper side does not decrease, but gradually decreases circumferentially from the upper side to the lower side. Figure 4 , Figure 5 As shown;

[0045] The distance h from the axis to the flat upper part of the pre-expanded tube blank is 188 mm, and the maximum radius of curvature R of the front convex part is... b =263mm, the maximum radius of curvature R of the rear convex portion b =263mm, maximum radius of curvature R of the lower convex portion a =269mm, with a maximum expansion ratio of nearly 80%;

[0046] The wall thickness t at the intersection of the middle cross section and the upper side of the longitudinal section passing through the axis of the pre-expanded tube blank c =10.89mm, the wall thickness t at the outermost point of the front side b =10.01mm, the wall thickness t at the outermost point on the rear side b =10.01mm, the thinning rate is 9.0%, and the wall thickness t at the lowest point on the lower side is... a = 9.67mm, thinning rate of 12.1%, no cracking;

[0047] The pre-expansion mold mainly includes: an upper control mold 17, a lower control mold 20, a left sliding mold 16, a right sliding mold 18, a left pressure head 22, and a right pressure head 19, etc. Figure 4 As shown. The axial width of the flat cavity on the upper side of the upper control mold 17 is greater than that of the convex cavities on the front and rear sides, ensuring good formability; the axial width of the lower control mold 20 is equal to that of the convex cavities on the front and rear sides of the upper control mold 17;

[0048] The axial width w1 of the convex portion on the front and rear sides of the upper control mold 17 is 120mm, and the maximum axial width w2 of the cavity of the upper flat portion is 160mm. The cavity transitions circumferentially from the upper to the lower side in a curved form, ensuring no extrusion marks during the forming of the upper flat portion of the pre-expanded tube blank. Figure 6 As shown; the axial width w1 of the lower control mold is 120mm, as... Figure 7 As shown.

[0049] The left sliding mold 16 and the right sliding mold 18 have the same cavity, and the axial width of the upper flat part cavity is smaller than that of the front and rear sides and the lower convex part cavity.

[0050] (3) Intermediate frequency annealing is carried out on the bulging part in the middle of the pre-bulged tube blank, and the annealing temperature is 850 °C;

[0051] (4) Final bulging: First, low-pressure liquid is filled into the pre-bulged tube blank inside by using a die, and then the pre-bulged tube blank is pressed from four directions of up and down, front and back to obtain a bridge housing pipe fitting, as Figure 8 , Figure 9 , Figure 10 shown. The upper side of the pre-bulged tube blank becomes a front plane with a gong-shaped additional front cover 23, the front and back sides are formed into side beams with a U-shaped cross-section, the lower side becomes a hemispherical rear oil cover, the wall thickness at the front plane and the side beams increases compared with the pre-bulged tube blank, and the wall thickness at the highest point of the rear oil cover hardly decreases, improving the bending and torsion resistance stiffness of the bridge housing part;

[0052] The maximum height d of the upper and lower side beams of the bridge housing part of the bridge housing pipe fitting m = 530 mm, the height h2 from the vertex of the rear oil cover to the axis is 252 mm, the maximum diameter d1 at the connection with the bridge housing body is φ454 mm, the height h3 from the vertex of the gong-shaped additional front cover to the axis is 120 mm, and the maximum diameter d2 at the connection with the front plane is φ284 mm; the diameter d on both sides of the bridge housing area s = φ186 mm straight-arm round tube becomes a straight-arm square tube, the height h1 of the rectangular cross-section is 160 mm, the width b1 is 158 mm, and the diameter d of the round tubes at both ends e = φ170 mm;

[0053] On the largest cross-section of the bridge housing part, the wall thickness t of the intersection point e of the side beam and the horizontal plane passing through the axis e = 10.41 mm, the wall thickness t of the fillet connection point g between the front plane and the side beam g = 10.68 mm, increasing compared with the wall thickness of the pre-bulged tube blank; the wall thickness t of the vertex of the rear oil cover f = 9.65 mm.

[0054] (5) Remove the additional front cover 23 with a smaller mass to obtain a seamless bridge housing product, as Figure 11 shown.

[0055] The bridge housing manufactured by the manufacturing method of the heavy truck bridge housing in this application is integrally formed without welds. It completely eliminates the problems of weld cracking and oil leakage and the failure at the rear oil cover; the front plane and side beams of the bridge housing with a large load have a large wall thickness, increasing the bending and torsion resistance stiffness of the bridge housing part, and at the same time ensuring product lightweight; the forming quality of the pipe fitting is good, the wall thickness reduction rate during hydroforming is small and there is no cracking, and the removed additional front cover has a small mass and high material utilization rate.

[0056] Although this application has been described above with reference to specific embodiments, those skilled in the art will understand that many modifications can be made to the configurations and details disclosed in this application within the principles and scope of the disclosure. The scope of protection of this application is determined by the appended claims, and the claims are intended to cover all modifications included in the literal meaning or scope of equivalents of the technical features in the claims.

Claims

1. A method for manufacturing a heavy-duty truck axle housing, based on parameters of the heavy-duty truck axle housing, namely the height d of the middle section of the axle housing. m The rectangular cross-section height h1 and width b1 of the straight arm sections on both sides of the bridge housing, and the outer diameter d of the circular tubes at both ends of the bridge housing. e The characteristics are: the height h2 of the apex of the rear oil cover from the central axis, and the maximum diameter d1 at the connection between the rear oil cover and the axle housing body. The method includes the following steps: (1) A stepped tube blank is selected, wherein the stepped tube blank consists of a rounded end region, a first transition region, a straight arm region, a second transition region, and an expansion region connected sequentially from both ends to the middle, and the outer diameter of the rounded end region is d. e The wall thickness of the rounded end region is t2, and the outer diameter of the straight arm region is d. s The wall thickness of the straight arm region is t1, the outer diameter of the bulging region is d0, and the wall thickness of the bulging region is t0. (2) Pre-expansion: The two ends of the stepped tube blank are sealed and filled with liquid using a pre-expansion mold. The stepped tube blank is then subjected to axial and circumferential feeding hydraulic expansion to obtain a pre-expansion tube blank. The middle part of the pre-expansion tube blank includes an upper side, a front side, a lower side, and a rear side connected in sequence. The upper side is flat, and the lower side, the front side, and the rear side are all convex. The wall thickness of the flat part of the upper side is not reduced, and the wall thickness gradually decreases from the upper side to the lower side along the circumferential direction. The distance h from the axis to the flattened portion on the upper side of the pre-expanded tube blank is (0.30~0.40)d. m The maximum radius of curvature R of the front convex portion b = (0.43~0.53)d m The maximum radius of curvature R of the rear convex portion b = (0.43~0.53)d m The maximum radius of curvature R of the lower convex portion a = (0.45~0.55)d m The maximum diameter expansion rate can reach 85%; The wall thickness t at the outermost point on the front side of the pre-expanded tube blank b = (0.89~0.95)t0, where t is the wall thickness at the outermost point on the rear side of the pre-expanded tube blank. b = (0.89~0.95)t0, where t is the wall thickness at the lowest point on the lower side. a = (0.84~0.90)t0, no cracking under large expansion ratio; The pre-expansion mold includes an upper control mold, a lower control mold, a left sliding mold, a right sliding mold, a left pressure head, and a right pressure head. The axial width of the cavity in the flat part on the upper side of the upper control mold is greater than that in the convex cavities on the front and rear sides, ensuring good formability. The axial width of the lower control mold is equal to that of the convex cavities on the front and rear sides of the upper control mold. The cavities of the left and right sliding molds are the same, and the axial width of the upper flat part cavity is smaller than that of the front and rear and lower convex parts cavity. (3) The middle expansion portion of the pre-expanded tube blank is subjected to medium-frequency annealing at a temperature of 800℃~900℃; (4) Final expansion: Low-pressure liquid is first filled into the pre-expanded tube blank using a mold, and then the pre-expanded tube blank is pressed and formed from four directions: top, bottom, front and back to obtain the bridge shell tube. The upper side of the pre-expanded tube blank becomes a front plane with a gong-shaped additional front cover, the front and back sides are formed into a cross-section of the cross-section of the side beam, and the lower side becomes a hemispherical rear oil cover. The wall thickness at the front plane and side beam continues to increase, and the wall thickness at the highest point of the rear oil cover does not decrease, which improves the bending and torsional stiffness of the bridge shell. (5) Remove the additional front cover to obtain a weld-free heavy truck axle housing.

2. The method for manufacturing a heavy-duty truck axle housing as described in claim 1, characterized in that: The axial width of the convex portion on the front and rear sides of the upper control mold is w1 = (100~140) mm, and the maximum axial width of the cavity of the flat portion on the upper side of the upper control mold is w2, which satisfies w2 = (1.2~1.5)w1. The upper control mold transitions from the upper side to the lower side in a planar or curved form along the circumferential direction to ensure that there are no extrusion marks when the flat portion on the upper side of the pre-expanded tube blank is formed; the axial width of the lower control mold is w1.

3. The method for manufacturing a heavy-duty truck axle housing as described in claim 1, characterized in that: The height h3 of the apex of the gong-shaped additional front cover from the axis is (0.40~0.52)h2, and the maximum diameter d2 of the connection between the gong-shaped additional front cover and the front plane is (0.60~0.70)d1, resulting in less material removal.

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