A method for manufacturing a hollow front axle tube blank for a vehicle

Abstract

This invention relates to the field of automotive manufacturing technology, specifically to a method for preparing a hollow front axle tube blank for automobiles. The method includes: S1: selecting a seamless steel tube of length L0, diameter φd0, and wall thickness t0 as the initial tube blank; S2: applying graphene lubrication to a region of length L1 from the outside to the inside at both ends of the initial tube blank; S3: using a double-layer coil to perform medium-frequency heating on the ends of the initial tube blank, resulting in a five-segment temperature field at the heated ends: a high-temperature constant zone, a high-temperature gradual cooling zone, a rapid cooling zone, a natural conduction zone, and a room-temperature zone, from the ends inwards; S4: performing mandrel upsetting and thickening on a three-axis hydraulic press. The tube blank prepared by this invention has an outer linear thickening zone with linearly increasing wall thickness, a uniform thickening zone with equal wall thickness and a thickness increase of more than 1 times, and an inner linear thickening zone with linearly decreasing wall thickness, resulting in a hollow front axle tube with good formability, improving material utilization while meeting the performance requirements of the axle.

Description

Technical Field

[0001] This invention relates to the field of automobile manufacturing technology, and in particular to a method for preparing a hollow front axle tube blank for automobiles. Background Technology

[0002] The front axle is one of the most important components of a car. Its complex shape and ability to withstand impact loads make it crucial for load-bearing and steering. Its strength, rigidity, and fatigue life directly affect the stability of the car's transmission system and the overall safety of the vehicle. The front axle typically consists of a central crossbeam, two side bends, and a front axle support.

[0003] Currently, automobiles mainly use forged and welded front axles, but these have low bending and torsional resistance, and the narrow section below the leaf spring seat is prone to fracture failure, making it difficult to achieve lightweighting while ensuring high performance. With the continuous advancement of automotive lightweighting requirements, the market urgently needs a new type of front axle that is lightweight and has high performance.

[0004] Chinese patent CN102240892A discloses a forming method for a hollow front axle, including: blank blanking—end and transition zone heating—end diameter reduction—end heating—end upsetting—overall heating—overall composite forming—machining. This method uses a hollow rectangular section to replace the solid I-beam section of the forged front axle, which is beneficial to reduce the weight of the front axle and improve the torsional bending strength. However, this method has certain defects in the process: (1) In order to obtain sufficient wall thickness at the end of the blank, it is necessary to heat it multiple times to perform necking and upsetting, which increases energy consumption and causes serious decarburization at the end of the blank; (2) The end of the front axle needs to be upsetting into a solid, which easily causes wrinkles to appear on the inner metal wall of the upsetting part, thereby reducing the performance of the axle.

[0005] Chinese patent CN115194419A discloses a method for forming a hollow automobile front axle, including: blank blanking—first heating—end thickening—second heating—bending and forming—integral pressing—machining—welding accessories. The end-thickened blank is as follows... Figure 1 As shown, the end wall thickness increases uniformly from the outside to the inside and then gradually decreases. This method only requires heating once when thickening the end, which reduces energy consumption and decarburization of the end surface. The hollow front axle tube with no metal folds in the inner cavity of the fist is formed. However, the following shortcomings still exist: (1) Two sets of coils with different frequencies are arranged in parallel when heating the end, resulting in low heating efficiency and high energy consumption; (2) The pressing of the fist of the tube is large and there is a lot of material waste.

[0006] Chinese patent CN117564204A discloses a upset thickening mold and forming method for a hollow automobile front axle tube blank. This forming method proposes an upset tube blank, such as... Figure 2As shown, its maximum thickening area is located on the inner side of the tube blank end. The hollow front shaft tubes formed by using this tube blank have a small end machining amount and high material utilization rate, but still have the following limitations: (1) The end of the upset tube blank lacks a uniform thickening area, which affects the performance of the hollow front shaft tubes formed in the end; (2) The wall thickness distribution of the thickening area of ​​the upset tube blank is complex, making it difficult to form in actual manufacturing.

[0007] In summary, in order to improve the material utilization rate of hollow front axle tubes and ensure sufficient performance of the punch, it is required that the inner side of the end of the hollow front axle tube blank has a sufficiently long uniform thickening zone. However, existing tube blank end thickening methods are usually difficult to meet this requirement and may also cause problems such as wrinkling of the inner cavity of the tube blank thickening zone and insufficient wall thickness increase. Therefore, it is urgent to develop a suitable preparation method. Summary of the Invention

[0008] To address the aforementioned problems, the present invention aims to provide a method for preparing a hollow front axle tube blank for automobiles. This method efficiently obtains a five-segment temperature field at the end of the tube blank using a double-layer coil, and then obtains a hollow front axle tube blank by upsetting with a mandrel. A uniform thickening zone of a certain length is formed on the inner side of the thickening zone, with a maximum thickening amount of more than 1 times. The wall thickness gradually decreases from the uniform thickening zone to the end. The hollow front axle tubes finally formed using this tube blank have higher material utilization and better performance.

[0009] The technical solution adopted in this invention is as follows:

[0010] The present invention provides a method for preparing a hollow front axle tube blank for automobiles, which specifically includes the following steps: S1: Select a seamless steel pipe with length L0, diameter φd0, and wall thickness t0 as the initial billet; S2: Apply graphene lubrication to the region of length L1 from the outside to the inside at both ends of the initial tube blank; S3: The initial tube blank end is heated by medium frequency using a double-layer coil. The heated initial tube blank end has a five-segment temperature field: from the initial tube blank end inward, they are high temperature constant zone, high temperature slow cooling zone, rapid cooling zone, natural conduction zone and room temperature zone. S4: The mandrel is upset and thickened on a three-way hydraulic press to obtain a hollow front axle tube blank. A uniform thickening zone of a preset length is formed inside the thickening zone of the hollow front axle tube blank. The wall thickness of the uniform thickening zone is equal and more than 1 times thick.

[0011] Furthermore, in step S3, the length of the high-temperature constant region is L. 01 The temperatures are all T1 = 1000~1100℃; the length of the high-temperature slow-descent zone is L. 02 The temperature decreases linearly from T1 with the first slope to T2 = 850~950℃; the length of the rapid cooling zone is L. 03The temperature decreases linearly from T2 to T3 (200-300℃) with a second slope; the first slope is less than the second slope; the length of the natural conduction zone is L. 04 The temperature naturally transitions from T3 to room temperature T4; the length of the room temperature zone is L. 05 The temperature is maintained at room temperature T4; where L 01 +L 02 +L 03 <L1。

[0012] Furthermore, in step S3, the double-layer coil includes an inner coil and an outer coil, with the ends of the two coils aligned and arranged inwards. The length of the inner coil is greater than that of the outer coil, and the length of the inner coil L2 = L 01 +L 02 +L 03 The outer coil length L3 = (0.8~0.9) (L 01 +L 02 ).

[0013] Furthermore, the inner diameter of the inner coil is φd1 = (1.05~1.15)d0; the inner diameter of the outer coil is φd2 = (1.05~1.15)d1.

[0014] Furthermore, step S4 includes: fixing the middle part of the heated initial tube blank by clamping the mold; feeding the tube blank axially synchronously through the left and right upsetting dies and the mandrel installed in its core until the side wall of the die contacts the end of the tube blank; the upsetting die continues to feed to upset and thicken the end of the tube blank, with a feed amount of S; after upsetting and thickening, a hollow front shaft tube blank is obtained.

[0015] Furthermore, the thickened area at the end of the hollow front axle tube blank is divided into three regions from the outside to the inside: an outer linear thickening region with a length of L4, where the wall thickness increases linearly from t3 to t4 with a third slope from the outside to the inside; a uniform thickening region with a length of L5 and a wall thickness of t4; and an inner linear thickening region with a length of L6, where the wall thickness decreases linearly from t4 to the initial wall thickness t0 with a fourth slope; the third slope is greater than the fourth slope.

[0016] Furthermore, the feed rate S = (0.85~1.05)d0; the length L4 of the linear thickening zone at the outer end of the hollow front shaft tube blank = (0.15~0.25)d0, the end wall thickness t3 = (1.0~1.1)t0; the wall thickness t4 of the uniform thickening zone = (2.0~2.3)t0, the length L5 = (0.4~0.6)d0; and the length L6 of the linear thickening zone on the inner side = (0.9~1.3)d0.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The double-layer coil heating proposed in this invention can efficiently obtain a specific five-segment heating temperature field at the end of the initial tube blank, effectively reducing energy consumption; 2. The hollow front axle tube blank obtained by the preparation method of the present invention has an outer linear thickening zone with linearly increasing wall thickness, a uniform thickening zone with equal wall thickness and more than 1 times thick, and an inner linear thickening zone with linearly decreasing wall thickness from the outside to the inside. The hollow front axle tube blank obtained by the present invention has better formability, improves material utilization, and fully meets the performance requirements of the fist. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a thickened tube blank at the end of a hollow rectangular cross-section automobile front axle with a large drop in the existing technology; Figure 2 This is a schematic diagram of a hollow automotive front axle upset thickening tube blank design in the prior art; Figure 3 This is a schematic diagram of the initial blank and lubrication zone of the hollow front axle in this invention; Figure 4 This is a schematic diagram of the five-segment temperature field obtained after heating the end of the initial tube blank in this invention; Figure 5 This is a schematic diagram of the double-layer coil used for initial tube blank end heating in this invention; Figure 6 This is a schematic diagram of the mandrel upsetting and thickening process in this invention; Figure 7 This is a schematic diagram of the hollow front shaft tube blank prepared according to the present invention; Figure 8 This is a schematic diagram of the main structure of the hollow front axle tube obtained by using the hollow front axle tube blank of the present invention; Figure 9 This is a top view schematic diagram of the hollow front axle tube obtained by using the hollow front axle tube blank of the present invention.

[0019] In the attached figures, the following labels are used: 1-Five-segment temperature field; 1a-High temperature constant zone; 1b-High temperature gradual cooling zone; 1c-Rapid cooling zone; 1d-Natural conduction zone; 1e-Room temperature zone; 2-Inner coil; 3-Outer coil; 4-Middle clamping mold; 5-Upsetting die; 5a-Die sidewall; 6-Mandrel; 7-Hollow front shaft blank; 8-Outer end linear thickening zone; 9-Uniform thickening zone; 10-Inner end linear thickening zone. Detailed Implementation

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] The method for preparing a hollow front axle tube blank for automobiles proposed in this invention specifically includes the following steps: S1: Select a seamless steel pipe with length L0, diameter φd0, and wall thickness t0 as the initial billet; S2: Apply graphene lubrication to the region of length L1 from the outside to the inside at both ends of the initial tube blank, such as... Figure 3 As shown; S3: A double-layer coil is used to perform medium-frequency heating on the end of the initial tube blank. The heated end of the initial tube blank obtains a five-segment temperature field 1: from the end of the initial tube blank inwards, these are the high-temperature constant zone 1a, the high-temperature slow-fall zone 1b, the rapid cooling zone 1c, the natural conduction zone 1d, and the room temperature zone 1e; (e.g., ...) Figure 4 As shown, where: The length of the high-temperature constant region 1a is L 01 The temperatures are all T1 = 1000~1100℃; The length of the high-temperature slow-descent zone 1b is L 02 The temperature decreases linearly and slowly from T1 with the first slope to T2 = 850~950℃; The length of the rapidly cooling region 1c is L 03 The temperature drops linearly from T2 to T3 = 200~300℃ with a second slope; the first slope is less than the second slope; The length of the natural conduction region 1d is L 04 The temperature naturally transitions from T3 to room temperature T4; The length of the room temperature region 1e is L 05 The temperature is maintained at room temperature T4; Among them, L 01 +L 02 +L 03 <L1。

[0022] like Figure 5 As shown, the double-layer coil adopts the following structural arrangement: the outer ends of the inner and outer coils are flush, and the inner ends are both wound inward and arranged on the outer side of the initial tube blank end; wherein, the length of the inner coil 2 is greater than the length of the outer coil 3, the length of the inner coil 2 is L2 and the inner diameter is φd1, and the length of the outer coil 3 is L3 and the inner diameter is φd2; wherein: The length L2 of the inner coil 2 is L 01 +L 02 +L03 The inner diameter is φd1 = (1.05~1.15)d0.

[0023] The length L3 of the outer coil 3 is (0.8~0.9)(L 01 +L 02 The inner diameter is φd2 = (1.05~1.15)d1.

[0024] S4: Upsetting and thickening of the mandrel is performed on a three-axis hydraulic press to obtain a hollow front axle blank. A uniformly thickened zone of a predetermined length is formed inside the thickened zone of the hollow front axle blank; the wall thickness of the uniformly thickened zone is equal and more than doubled. The specific process is as follows: like Figure 6 As shown, the initial tube blank after heating is first fixed by the clamping mold 4; then, the upsetting dies 5 on the left and right sides and the mandrel 6 installed in the core are fed axially synchronously until the side wall 5a of the upsetting die contacts the end of the tube blank; then the upsetting die 5 continues to feed to upset and thicken the end of the tube blank, with a feed amount of S; after upsetting and thickening, a hollow front shaft tube blank 7 is obtained.

[0025] Wherein, the feed rate S = (0.85~1.05)d0; like Figure 7 As shown, the thickened area at the end of the hollow front shaft tube blank 7 is divided into three regions from the outside to the inside: the outer linear thickening area 8, with a length of L4, where the wall thickness increases linearly from t3 to t4 with a third slope from the outside to the inside; the uniform thickening area 9, with a length of L5 and a wall thickness of t4; and the inner linear thickening area 10, with a length of L6, where the wall thickness decreases linearly from t4 to the initial wall thickness t0 with a fourth slope; the third slope is greater than the fourth slope.

[0026] The length of the linear thickening region 8 at the outer end is L4 = (0.15~0.25)d0, and the end wall thickness is t3 = (1.0~1.1)t0; The wall thickness of the uniformly thickened region 9 is t4 = (2.0~2.3)t0, and the length is L5 = (0.4~0.6)d0; The length L6 of the inner linear thickening region 10 is (0.9~1.3)d0.

[0027] The core of the preparation method proposed in this invention lies in the application of the characteristic that the yield stress changes with temperature during the plastic deformation of metal. By adjusting the yield stress of each section of the tube blank through a five-segment heating temperature field, and combining the characteristic that the axial force on each part of the tube blank during upsetting gradually increases from the end to the inside, it is possible to obtain an outer linear thickening zone with linearly increasing wall thickness, a uniform thickening zone with equal wall thickness, and an inner linear thickening zone with linearly decreasing wall thickness. The maximum wall thickness and length of the uniform thickening zone need to be controlled by a mandrel installed in the core of the upsetting die.

[0028] The present invention will be further illustrated below through specific embodiments: This embodiment proposes a method for preparing a hollow front axle tube blank for commercial vehicles, the process steps of which are as follows: Step S1: Select a seamless steel pipe with a length of L0=2240mm, a diameter of φd0=114mm, and a wall thickness of t0=13mm as the initial tube blank.

[0029] Step S2: Apply graphene lubrication to the region with a length of L1=520mm from the outside to the inside at both ends of the initial tube blank.

[0030] Step S3: Double-layer coil intermediate frequency heating, the end of the heated tube blank obtains a five-segment temperature field 1, which has the following characteristics: From the end of the tube blank inwards, the zones are: a high-temperature constant zone 1a, a high-temperature slow-fall zone 1b, a rapid-fall zone 1c, a natural conduction zone 1d, and a room-temperature zone 1e; among which: The length of the high-temperature constant region 1a is L 01 =50mm, temperature T1=1000℃; The length of the high-temperature slow-descent zone 1b is L 02 =100mm, the temperature decreases linearly and slowly from T1 to T2=900℃; The length of the rapidly cooling zone 1c is L 03 =200mm, the temperature drops linearly from T2 with a large slope to T3=220℃; The natural conduction zone has a length of L over 1 day. 04 =150mm temperature naturally transitions from T3 to room temperature T4; The length of the room temperature region 1e is L 05 =1240mm, temperature maintained at room temperature T4.

[0031] The double-layer coil structure has the following characteristics: the inner coil 2 is longer than the outer coil 3, the outer ends of the inner and outer coils are flush, and the inner ends are wound inwards around the tube blank; the inner coil 2 has a length of L2=350mm and an inner diameter of φd1=125mm; the outer coil 3 has a length of L3=130mm and an inner diameter of φd2=135mm.

[0032] Step S4: Perform mandrel upsetting and thickening on a three-axis hydraulic press, as follows: The heated tube blank is fixed in the middle by clamping mold 4; it is then fed axially synchronously by the left and right upsetting dies 5 and the mandrel 6 installed in its core until the die sidewall 5a contacts the end of the tube blank; the upsetting dies 5 continue to feed to upset and thicken the end of the tube blank, with a feed amount S=110mm. After upsetting, a hollow front shaft tube blank 7 is obtained.

[0033] The thickened area at the end of the hollow front shaft tube blank 7 obtained after upsetting is divided into three regions from the outside to the inside: the outer linear thickening area 8, with a length of L4=25mm, and the wall thickness increases linearly from t3=13.5mm to t4 with a large slope from the outside to the inside; the uniform thickening area 9, with a length of L5=55mm and a wall thickness of t4=28mm; and the inner linear thickening area 10, with a length of L6=130mm, and the wall thickness decreases linearly from t4 to the initial wall thickness t0.

[0034] Hollow front axle tubes for vehicles are prepared using the hollow front axle tube blanks obtained by the above method, such as... Figure 8 and Figure 9 As shown, it has the following advantages: (1) The outer end of the fist is a process supplement that is subsequently removed by machining. It is obtained by pressing the linear thickening zone of the outer end of the hollow front axle tube blank. It is small in size and light in weight, so there is less material waste; (2) The wall thickness of the main pin hole to be processed in the fist meets the performance requirements, and no metal wrinkles are generated in the inner cavity. This is due to the fact that the wall thickness of the uniform thickening zone of the hollow front axle tube blank is increased by more than 1 times and has a suitable length.

[0035] All matters not covered in this invention are common knowledge.

[0036] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a hollow front axle tube blank for automobiles, characterized in that, The method includes the following steps: S1: Select a seamless steel pipe with length L0, diameter φd0, and wall thickness t0 as the initial billet; S2: Apply graphene lubrication to the region of length L1 from the outside to the inside at both ends of the initial tube blank; S3: The initial tube blank end is heated by medium frequency using a double-layer coil. The heated initial tube blank end has a five-segment temperature field: from the initial tube blank end inward, they are high temperature constant zone, high temperature slow cooling zone, rapid cooling zone, natural conduction zone and room temperature zone. S4: The mandrel is upset and thickened on a three-axis hydraulic press to obtain a hollow front axle tube blank. A uniform thickening zone of a preset length is formed inside the thickening zone of the hollow front axle tube blank. The wall thickness of the uniform thickening zone is equal and more than 1 times thick. In step S3, the length of the high-temperature constant region is L. 01 The temperatures are all T1 = 1000~1100℃; the length of the high-temperature slow-descent zone is L. 02 The temperature decreases linearly from T1 with the first slope to T2 = 850~950℃; the length of the rapid cooling zone is L. 03 The temperature decreases linearly from T2 to T3 (200-300℃) with a second slope; the first slope is less than the second slope; the length of the natural conduction zone is L. 04 The temperature naturally transitions from T3 to room temperature T4; the length of the room temperature zone is L. 05 The temperature is maintained at room temperature T4; where L 01 +L 02 +L 03 <L1; In step S3, the double-layer coil includes an inner coil and an outer coil, with the ends of the two coils aligned and arranged inwards. The length of the inner coil is greater than that of the outer coil, and the length of the inner coil L2 = L 01 +L 02 +L 03 The outer coil length L3 = (0.8~0.9) (L 01 +L 02 ); The thickened area at the end of the hollow front axle tube blank is divided into three regions from the outside to the inside: an outer linear thickening region with a length of L4, where the wall thickness increases linearly from t3 to t4 with a third slope from the outside to the inside; a uniform thickening region with a length of L5 and a wall thickness of t4; and an inner linear thickening region with a length of L6, where the wall thickness decreases linearly from t4 to the initial wall thickness t0 with a fourth slope; the third slope is greater than the fourth slope.

2. The method for preparing a hollow front axle tube blank for automobiles according to claim 1, characterized in that: The inner diameter of the inner coil is φd1 = (1.05~1.15)d0; the inner diameter of the outer coil is φd2 = (1.05~1.15)d1.

3. The method for preparing a hollow front axle tube blank for automobiles according to claim 1, characterized in that: Step S4 includes: fixing the middle part of the heated initial tube blank by clamping the mold; feeding the tube blank axially synchronously through the left and right upsetting dies and the mandrel installed in the core until the side wall of the die contacts the end of the tube blank; the upsetting die continues to feed to upset and thicken the end of the tube blank, with a feed amount of S; after upsetting and thickening, a hollow front shaft tube blank is obtained.

4. The method for preparing a hollow front axle tube blank for automobiles according to claim 3, characterized in that: The feed rate S = (0.85~1.05)d0; the length L4 of the linear thickening zone at the outer end of the hollow front shaft tube blank = (0.15~0.25)d0, the end wall thickness t3 = (1.0~1.1)t0; the wall thickness t4 of the uniform thickening zone = (2.0~2.3)t0, the length L5 = (0.4~0.6)d0; the length L6 of the linear thickening zone on the inner side = (0.9~1.3)d0.

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