CN109706392B

CN109706392B - Square tube for trailer axle, preparation method thereof and trailer axle

Info

Publication number: CN109706392B
Application number: CN201811594036.1A
Authority: CN
Inventors: 田研; 肖松良; 张敏; 赵勤; 周勇; 刘晓; 王世明
Original assignee: Hengyang Valin Steel Tube Co Ltd
Current assignee: Hengyang Valin Steel Tube Co Ltd
Priority date: 2018-12-25
Filing date: 2018-12-25
Publication date: 2020-08-21
Anticipated expiration: 2038-12-25
Also published as: CN109706392A

Abstract

The invention provides a square tube for a trailer axle, a preparation method of the square tube and the trailer axle. The square tube comprises the following chemical element components in percentage by weight: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.02 to 0.04% of Al, 0.18 to 0.28% of Ni, and the balance of Fe and inevitable impurities. Through the proportion of the elements, the formed square tube has the characteristics of high strength and high toughness, and can meet the requirements of trailer axles.

Description

Square tube for trailer axle, preparation method thereof and trailer axle

Technical Field

The invention relates to the technical field of metallurgy, in particular to a square tube for a trailer axle, a preparation method of the square tube and the trailer axle.

Background

The trailer axle can be divided into an integral shaft and a three-section shaft according to a forming method. The integrated shaft is made of round tube and is formed by extrusion, closing and squaring. The three-section shaft takes a square tube (each side wall is not an absolute plane but a curved surface with larger curvature radius) as a raw material, and the two ends of the three-section shaft are welded and forged with solid shaft heads. Compared with an integrated shaft, the three-section shaft has greater technical advantages, and the safety coefficient is higher than that of the integrated shaft. The shaft head of the three-section shaft is a solid forging, so that the bearing capacity and the service life are long; the three-section shaft is reasonable in structural design, reduces tire abrasion in no-load, and ensures stable transportation of goods because the shaft head and the shaft body are level in loading; the three-section shaft is mainly suitable for high-end trucks or special trucks. The square tube for manufacturing the axle body of the three-section trailer axle needs to be assembled with an axle accessory, and good dimensional precision is required. The trailer needs to bear large high-frequency sine wave periodic load when running, the standard regulated fatigue life of JT/T475-2002 trailer axle is not less than 800000 times, and the material for manufacturing the axle needs to have good toughness.

At present, square tubes for manufacturing three-section trailer axle bodies are produced in a shaping cold-drawing mode. The square tube for the axle is produced by a shaping cold-drawing process, the outer diameter of the outer surface of the hollow billet is controlled by an outer die, the wall thickness and the inner diameter of the inner surface of the hollow billet are controlled by a special-shaped core die, and the finished product is subjected to heat treatment by quenching, water-spraying cooling and tempering processes. The cold-drawn square tube is made from hot-rolled rough tubes, and is shaped and cold-drawn after being pickled to remove oxide skin, and the pickling, phosphorization, saponification and other processes can seriously pollute the environment. The cold deformation square tube has residual stress, the free torsional rigidity of the section of the cold deformation square tube is lower, torsion is easy to occur when the cold deformation square tube is bent, bending and twisting are easy to occur when the cold deformation square tube is pressed, and the torsional property is poor. The cold deformation mode can only produce the square pipe of small wall thickness, does not thicken again in the corner, bears the weak ability of the concentrated load of locality. The cold hardening caused by the continuous cold deformation increases the strength and hardness of the square pipe and decreases the toughness index, and therefore, the impact resistance is deteriorated.

The hot rolling process is used for producing seamless square pipes, and the existing hot rolling steel pipe production line is mainly utilized, and after the round section hot rolling process of seamless steel pipes, a three-roller or four-roller sizing frame is added for direct squaring. The hot rolling process saves a plurality of processing procedures such as acid washing, phosphorization, saponification, cold drawing and the like, greatly reduces the environmental pollution, reduces the production cost and improves the production efficiency. The four-roller square tube sizing mill frame is difficult to be universal with the existing universal three-roller circular tube sizing mill frame, only the four-roller square tube sizing mill frame can be transformed, one of three transmission shafts of the three-roller circular tube sizing mill is used for transmission, the power output of the sizing mill is limited, and only a small-wall-thickness hot-rolled square tube can be produced. The three-roller square tube sizing mill frame is completely compatible with the three-roller circular tube sizing mill frame, the deformation capacity of the circular tube sizing mill can be fully exerted, and the hot-rolled square tube is wide in specification coverage range. However, the roller edges of the rack roller of the three-roller square tube sizing mill are intersected at the side length middle part of the square tube pass, metal in a deformation area can flow out from a roller gap when the square tube is rolled, a protruding edge can be formed at the side length middle part of the square tube, and the requirement of the square tube for the axle on high size precision cannot be met.

Disclosure of Invention

The invention mainly aims to provide a square tube for a trailer axle, a preparation method thereof and the trailer axle, so as to provide a novel trailer axle with high strength and high toughness.

In order to achieve the above object, according to one aspect of the present invention, there is provided a square tube for a trailer axle, the square tube comprising the following chemical elements in percentage by weight: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.02 to 0.04% of Al, 0.18 to 0.28% of Ni, and the balance of Fe and inevitable impurities.

Further, the trailer axle is a three-section axle, and the rolling process of the square tube is hot rolling.

According to another aspect of the present invention, there is provided a method of manufacturing a square tube for a trailer axle, the method comprising: heating a steel billet to obtain a hot billet, wherein the steel billet comprises the following chemical element components in percentage by weight: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.02 to 0.04% of Al, 0.18 to 0.28% of Ni0.18, and the balance of Fe and inevitable impurities; sequentially carrying out hot piercing and rolling on the hot blank to obtain a pierced billet; and (4) squaring the pierced billet to obtain a square tube.

Further, adopt and decide the side device and decide the side to above-mentioned pierced billet, decide the side device and include: one or more pipe rolling mills and one or more side pipe rolling mills that set gradually along tubular product direction of delivery, each side pipe rolling mill includes: a frame; the three groups of roller parts are provided with a roller which moves actively, each roller is arranged on the rack, three rollers in the three groups of roller parts comprise a first roller, a second roller and a third roller, the axes of the rollers are intersected in the same plane, the roller grooves of the rollers are combined to form a square hole, each side wall of the square hole is an arc-shaped side wall, the axis of the first roller is arranged along the horizontal direction, the roller grooves of the second roller and the third roller are symmetrically arranged along the vertical bisector of the roller groove of the first roller, the axes of the rollers are intersected to form an equilateral triangle, the roller grooves of the first roller form two adjacent side walls of the square hole, and the roller grooves of the second roller and the roller grooves of the third roller form one of the other two side walls of the square hole.

Furthermore, the number of the round tube rolling mills is one, the number of the square tube rolling mills is multiple, and the aperture of each square tube rolling mill is sequentially reduced and the curvature radius of each square tube rolling mill is sequentially increased along the conveying direction of the tubes.

Further, the total reduction rate of the square tube rolling mill is 12-15%, and the reduction rates of the square tube rolling mill are 1.2-1.5%, 6.0-8.0% and 5.0-6.0% in sequence along the conveying direction of the pipe.

Further, the heating treatment process of the steel billet comprises the steps of preheating the steel billet along with a furnace, heating in sections and soaking in sequence to obtain a hot billet, preferably, the heating in sections comprises five sections of heating, wherein the temperature of the first section of heating is 850-940 ℃, the temperature of the second section of heating is 980-1080 ℃, the temperature of the third section of heating is 1130-1170 ℃, the temperature of the fourth section of heating is 1230-1280 ℃, the temperature of the fifth section of heating is 1230-1280 ℃, the temperature of soaking is 1220-1270 ℃, and the time of the heating treatment is further preferably 1.5-4 hours.

Further, the hot piercing is tapered piercing, and it is preferable that the rolling is performed by a tandem mill.

Further, the outer diameters of the hollow billets obtained by the conical perforation are respectively

And

the diameter of the continuous rolling mill which is sequentially corresponding to the external diameter of the hollow billet is

According to one aspect of the invention, a trailer axle is provided, wherein the trailer axle is a three-section axle and is manufactured by adopting the square tube manufactured by any one of the manufacturing methods.

By applying the technical scheme of the invention, carbon mainly acts as a gap solid solution element to improve the strength of cast steel. However, too high carbon may reduce plasticity, toughness, and especially plasticity; and too low carbon requires additional strength elements such as manganese and molybdenum. From the matching angle of performance and cost, the carbon content is controlled to be 0.19-0.23%. The silicon is mainly used as a reducing agent and a deoxidizing agent in the steel-making process. However, since too high silicon is solid-solution-strengthened in austenite and ferrite to lower toughness, the content of silicon is controlled to be 0.20% to 0.37%. Manganese is an effective element for improving the strength of the alloy cast steel, and can effectively improve the low-temperature impact toughness of the cast steel and also improve the low-temperature toughness of a welding seam. Too low manganese results in insufficient strength, and thus the manganese content is controlled to be 1.55% to 1.68%. The vanadium, niobium and aluminum can be compounded to refine grains, so that the content of V is controlled to be 0.04-0.07%, the content of Nb is controlled to be 0.03-0.05%, and the content of Al is controlled to be 0.02-0.04%, so as to fully exert the mutual cooperation effect. The nickel is used for improving hardenability and strength, and is controlled to be 0.18-0.28% so as to more stably meet the requirements at low temperature. Through the proportion of the elements, the formed square tube has the characteristics of high strength and high toughness, and can meet the requirements of trailer axles.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 shows a schematic structural view of a square tube rolling mill according to an embodiment of the present invention.

Wherein the figures include the following reference numerals:

1. a frame; 21. a first roll; 22. a second roll; 23. and a third roller.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As analyzed in the background of the present application, a square tube of a trailer axle of a three-section axle requires good toughness, and the present application provides a square tube for a trailer axle, a method for manufacturing the same, and a trailer axle.

In an exemplary embodiment of the present application, a square tube for a trailer axle is provided, wherein the square tube comprises the following chemical element components in percentage by weight: 0.19 to 0.23C, 0.20 to 0.37 Si, 1.55 to 1.68 Mn, 0.04 to 0.07V, 0.03 to 0.05 Nb0.02 to 0.04 Al, 0.18 to 0.28 Ni, and the balance Fe and unavoidable impurities.

The main function of carbon is as an interstitial solid solution element to improve the strength of cast steel. However, too high carbon may reduce plasticity, toughness, and especially plasticity; and too low carbon requires additional strength elements such as manganese and molybdenum. From the matching angle of performance and cost, the carbon content is controlled to be 0.19-0.23%. The silicon is mainly used as a reducing agent and a deoxidizing agent in the steel-making process. However, since too high silicon is solid-solution-strengthened in austenite and ferrite to lower toughness, the content of silicon is controlled to be 0.20% to 0.37%. Manganese is an effective element for improving the strength of the alloy cast steel, and can effectively improve the low-temperature impact toughness of the cast steel and also improve the low-temperature toughness of a welding seam. Too low manganese results in insufficient strength, and thus the manganese content is controlled to be 1.55% to 1.68%. The vanadium, niobium and aluminum can be compounded to refine grains, so that the content of V is controlled to be 0.04-0.07%, the content of Nb is controlled to be 0.03-0.05%, and the content of Al is controlled to be 0.02-0.04%, so as to fully exert the mutual cooperation effect. The nickel is used for improving hardenability and strength, and is controlled to be 0.18-0.28% so as to more stably meet the requirements at low temperature. Through the proportion of the elements, the formed square tube has the characteristics of high strength and high toughness, and can meet the requirements of trailer axles.

Preferably, the trailer axle is a three-section axle, and the rolling process of the square tube is hot rolling. Compared with a cold-deformed square tube, the hot-rolled square tube has the advantages of larger sectional area, smaller inner and outer circular angles and reasonable geometric size distribution in the same variety and specification, and has better bearing performance; the thermal deformation square tube has small residual stress, better low-temperature impact performance and lower ductile-brittle transition temperature. The square pipe produced by cold deformation has a high possibility of brittle cracking due to process limitation, and a brittle cracking area needs to be avoided during welding, while the hot-rolled square pipe does not have the problems.

In another exemplary embodiment of the present application, there is provided a method of manufacturing a square tube for a trailer axle, the method including: heating a steel billet to obtain a hot billet, wherein the steel billet comprises the following chemical element components in percentage by weight: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.02 to 0.04% of Al, 0.18 to 0.28% of Ni, and the balance of Fe and inevitable impurities; sequentially carrying out hot piercing and rolling on the hot blank to obtain a pierced billet; and (4) squaring the pierced billet to obtain a square tube.

Compared with a cold-deformed square tube, the hot-rolled square tube has the advantages of larger sectional area, smaller inner and outer circular angles and reasonable geometric size distribution in the same variety and specification, and has better bearing performance; the thermal deformation square tube has small residual stress, better low-temperature impact performance and lower ductile-brittle transition temperature. The square pipe produced by cold deformation has a high possibility of brittle cracking due to process limitation, and a brittle cracking area needs to be avoided during welding, while the hot-rolled square pipe does not have the problems. Therefore, the steel billet has the characteristics of high strength and high toughness at low temperature due to the element composition of the steel billet, and the high strength and high toughness of the steel billet can be fully exerted by adopting a hot piercing and hot rolling mode, so that the formed square pipe for the trailer axle has the high strength and high toughness at low temperature.

In order to improve the dimensional accuracy of the square pipe, it is preferable to square the pierced billet using a squaring device, which includes, as shown in fig. 1: one or more pipe rolling mills and one or more side pipe rolling mills that set gradually along tubular product direction of delivery, each side pipe rolling mill includes: a frame 1; three groups of roller parts, each group of roller parts is provided with a roller which moves actively, each roller is arranged on the frame 1, three rollers in the three groups of roller parts comprise a first roller 21, a second roller 22 and a third roller 23, the axes of the rollers are intersected in the same plane, the roller grooves of the rollers are combined to form a square hole, each side wall of the square hole is an arc-shaped side wall, the axis of the first roller 21 is arranged along the horizontal direction, the roller grooves of the second roller 22 and the third roller 23 are symmetrically arranged along the vertical bisector of the roller groove of the first roller 21, and the axes of the rollers are intersected to form an equilateral triangle, and the roll groove of the first roll 21 forms two adjacent side walls of the square hole, the tangent plane of the roll groove of the second roll 22 is perpendicular to the tangent plane of the roll groove of the third roll 23, and the roll groove of the second roll 22 and the roll groove of the third roll 23 form one of the other two side walls of the square hole. The roller grooves of the rollers are intersected at the corner of the square pipe hole pattern R, metal in a deformation area cannot flow out of the roller gaps when the square pipe is rolled, a protruding edge cannot be formed in the side length middle part of the square pipe, and the requirement of the square pipe for the axle on high dimensional accuracy can be completely met; each roller part is provided with a roller which moves actively, so that enough rolling torque can be provided for sizing the square pipe, and the sizing requirement of the thick-wall square pipe is met. The square tube rolling mill can utilize the frame of the existing three-roll circular tube rolling mill, and the shape of the roll groove of each roll can be changed, so that the square tube rolling mill is easy to realize.

In a preferred embodiment, there are one round tube rolling mill and a plurality of square tube rolling mills, and the diameter of the square tube rolling mill decreases and the radius of curvature increases in the tube conveying direction. The primary sizing is carried out by using the circular tube rolling mill, and then the sizing is carried out in sequence by using the plurality of square tube rolling mills, so that the working stability and the sizing accuracy of each rolling mill are improved.

In order to further improve the dimensional accuracy of the obtained square pipe, the total reduction rate of the square pipe rolling mill is preferably 12-15% to obtain a square pipe with a smooth surface. The rolling reduction rate of the square tube rolling mill is 1.2-1.5%, 6.0-8.0% and 5.0-6.0% in sequence along the conveying direction of the pipe. The rolling reduction of each square tube rolling machine is within 8.0 percent, so that the rolling machines can conveniently bite and control the size of the hollow billet, and the problem that the size precision and the torsion resistance of a finished product are deteriorated due to overlarge deformation in the sizing process is solved.

In one embodiment, the process of heating the steel billet comprises the steps of preheating the steel billet along with a furnace, heating in sections and soaking in sequence to obtain a hot billet, preferably, the heating in sections comprises five sections of heating, wherein the temperature of the first section of heating is 850-940 ℃, the temperature of the second section of heating is 980-1080 ℃, the temperature of the third section of heating is 1130-1170 ℃, the temperature of the fourth section of heating is 1230-1280 ℃, the temperature of the fifth section of heating is 1230-1280 ℃, the temperature of soaking is 1220-1270 ℃, and the time of heating is further preferably 1.5-4 h. Through the sectional heating, the steel billet is gradually raised to the soaking temperature, and the defect that cracks are generated in the hot billet due to the fact that the heating speed is too high is avoided.

In addition, the hot perforation is preferably a conical perforation, the conical perforation has high deformability, the pierced billet has flexible geometric dimension, high precision and high production efficiency. The rolling is preferably carried out by adopting a continuous rolling mill, so that the problems of high strength and hardness and low toughness and plasticity of the cold-rolled square tube are solved, and the impact property is good; moreover, the production process can realize continuous production and has high production efficiency. The conical puncher and the continuous rolling mill are matched for operation, so that the square tube with more uniform mechanical property and stronger torsion resistance can be obtained, the production efficiency of the square tube can be improved, and the large-scale efficient production of the square tube is realized.

Preferably, the outer diameters of the capillaries obtained when the conical perforation is performed are respectively

And

when the diameter of the continuous rolling mill sequentially corresponds to the external diameter of the tubular billet is

After the square tube is formed, the preparation method is carried out according to the conventional process of the trailer axle, and the description is omitted.

In yet another exemplary embodiment of the present application, a trailer axle is provided, the trailer axle being a three-section axle, the trailer axle being fabricated from a square tube made by any of the above-described fabrication methods. The trailer axle prepared by the preparation method has high strength and high toughness.

The complete square tube manufacturing process comprises the following steps:

sawing and blanking → heating in a circular furnace → hot perforation → continuous rolling → reheating in a stepping furnace → high-pressure water descaling → orientation → cooling in a cooling bed → head and tail cutting → physicochemical inspection is qualified → pressure straightening → nondestructive inspection → cutting to length → manual inspection → character spraying → packaging and warehousing.

Rolling in a phi 340MPM continuous rolling mill set of Hengyang Hualing steel pipe Co. The following examples are provided to illustrate hot piercing, continuous rolling, and sizing.

Example 1

The weight percentage of each chemical element component in the square tube material for the trailer axle used in the low-temperature environment is as follows: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.030 to 0.050% of Nb, 0.020 to 0.040% of Al, 0.18 to 0.28% of Ni, and the balance of Fe and inevitable impurities.

Taking the square tube with the specification of 150 multiplied by 11mm as an example, the concrete steps are as follows:

A. and (3) producing by adopting a blank with the diameter of 250 mm. The billet heating comprises preheating, heating and soaking processes. Preheating temperature is dependent on furnace temperature; the heating is divided into five sections: the first-stage heating temperature is 900 +/-10 ℃, the second-stage heating temperature is 1030 +/-10 ℃, the third-stage heating temperature is 1150 +/-10 ℃, and the fourth-stage and fifth-stage heating temperatures are 1260 +/-10 ℃; the temperature of the soaking section is 1250 +/-10 ℃, and the total heating time is 2-2.5 hours.

B. The tube rolling adopts a conical puncher for punching and a continuous tube rolling mill group for rolling. The specification of the perforated hollow billet required for producing the square tube is as follows

× 21mm, designs a continuous tube rolling mill group

Pass, the size of the pierced billet after continuous rolling is

C. The sizing mill adopts a round pipe frame and 3 square pipe frames for organization production, and the roll pass curve of the square pipe sizing mill is shown in figure 1. The round hollow billet is sized by a round hole type frame, and the specification of the hot rolling hollow billet is

Along the running direction of the pipe, the roll pass diameters of a square pipe sizing mill are 172.5mm, 159mm and 150.7mm in sequence, the rolling reduction rates of a single stand of the roll of the square pipe sizing mill are 1.43%, 7.83% and 5.22% respectively, the total rolling reduction rate of a square pipe stand is 13.88%, the curve curvature radius range of the roll of the square pipe stand is 210mm, 700mm and 2300mm, and the seamless hot-rolled square pipe with the specification of 150 × 150 × 11mm is produced by sizing through a square pipe hole type stand.

The specification and the rotating speed of the square tube rolling mill arranged in the sequence of passing the round tubes are shown in table 1.

TABLE 1

Comparative example 1

The difference from the embodiment 1 is that the weight percentage of each chemical element component in the square tube material for the trailer axle is as follows: 0.25 to 0.30% of C, 0.20 to 0.37% of Si, 1.0 to 1.2% of Mn, 0.04 to 0.07% of V, 0.030 to 0.050% of Nb, 0.020 to 0.040% of Al, and the balance of Fe and inevitable impurities.

Comparative example 2

The difference from the embodiment 1 is that the weight percentage of each chemical element component in the square tube material for the trailer axle is as follows: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.020 to 0.040% of Al, and the balance of Fe and inevitable impurities.

Any two square tubes of each example and comparative example are selected and tested for geometric dimension and mechanical property at room temperature, the results of geometric dimension test are shown in table 2, tensile test and impact test are performed on the square tubes of the examples and comparative examples according to the method specified in standard method and definition of steel product mechanical property test, and the results of mechanical property test are shown in table 3.

TABLE 2

TABLE 3

As can be seen from the data in tables 2 and 3, the non-quenched and tempered hot-rolled seamless square tube can meet the requirements of the trailer axle on manufacturing and use in various geometric dimensions and mechanical properties.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a square tube for a trailer axle is characterized by comprising the following steps:

heating a steel billet to obtain a hot billet, wherein the steel billet comprises the following chemical element components in percentage by weight: 0.19 to 0.23% of C, 0.20 to 0.37% of Si, 1.55 to 1.68% of Mn, 0.04 to 0.07% of V, 0.03 to 0.05% of Nb, 0.02 to 0.04% of Al, 0.18 to 0.28% of Ni0.18, and the balance of Fe and inevitable impurities;

sequentially carrying out hot piercing and rolling on the hot blank to obtain a pierced billet;

the pierced billet is subjected to square setting to obtain a square tube,

adopt and decide the side device right the pierced billet carries out deciding the side, decide the side device and include: one or more pipe rolling mills and one or more side pipe rolling mills that set gradually along tubular product direction of delivery, each side pipe rolling mill includes:

a frame (1);

the rolling device comprises three groups of rolling parts, each group of rolling parts is provided with a rolling roller which moves actively, each rolling roller is arranged on the rack (1), three rolling rollers in the three groups of rolling parts comprise a first rolling roller (21), a second rolling roller (22) and a third rolling roller (23), the axes of the rolling rollers are intersected in the same plane, rolling grooves of the rolling rollers are combined to form a square hole, each side wall of the square hole is an arc-shaped side wall, the axis of the first rolling roller (21) is arranged along the horizontal direction, the rolling grooves of the second rolling roller (22) and the third rolling roller (23) are symmetrically arranged along the vertical bisector of the rolling groove of the first rolling roller (21), the axes of the rolling rollers are intersected to form an equilateral triangle, the rolling grooves of the first rolling roller (21) form two adjacent side walls of the square hole, and the rolling grooves of the second rolling roller (22) and the rolling grooves of the third rolling roller (23) form each of the other two side walls of the square hole One.

2. The manufacturing method according to claim 1, wherein there are one round tube rolling mill and a plurality of square tube rolling mills, and the diameter of the bore of each of the square tube rolling mills decreases and the radius of curvature increases in the direction of the tube conveyance.

3. The manufacturing method according to claim 2, wherein the total reduction ratio of the square tube rolling mill is 12 to 15%, and the reduction ratios of the square tube rolling mill are 1.2 to 1.5%, 6.0 to 8.0%, and 5.0 to 6.0% in the conveying direction of the pipe.

4. The method according to claim 1, wherein the heating the steel slab comprises sequentially preheating the steel slab in a furnace, heating the steel slab in stages, and soaking the steel slab in the heat to obtain the hot slab.

5. The method according to claim 4, wherein the step-wise heating comprises five-step heating, wherein the temperature of the first heating step is 850-940 ℃, the temperature of the second heating step is 980-1080 ℃, the temperature of the third heating step is 1130-1170 ℃, the temperature of the fourth heating step is 1230-1280 ℃, and the temperature of the fifth heating step is 1230-1280 ℃.

6. The preparation method according to claim 4, wherein the soaking temperature is 1220 to 1270 ℃.

7. The method according to claim 4, wherein the heat treatment is carried out for 1.5 to 4 hours.

8. The method of claim 1, wherein the hot perforations are tapered perforations.

9. The method for manufacturing a composite material according to claim 8, wherein the rolling is performed by a tandem mill.

10. The manufacturing method according to claim 9, wherein the outer diameters of the pipes obtained by the conical perforation are respectively phi 246mm, phi 288mm, phi 336mm and phi 410mm, and the hole diameters of the continuous rolling mill sequentially corresponding to the outer diameters of the pipes are phi 210mm, phi 248mm, phi 293mm and phi 364 mm.

11. A trailer axle, characterized in that the trailer axle is a three-section axle, and the trailer axle is manufactured by using the square tube manufactured by the manufacturing method according to any one of claims 1 to 10.