阅读说明：本技术 一种高性能汽车转向系统中横拉杆接头用钢 (Steel for tie rod joint in high-performance automobile steering system ) 是由 梁佰战 郑力宁 蒋栋初 朱延律 赵刚 赵岳 陈坤 上官福康 于 2021-06-10 设计创作，主要内容包括：本发明公开了一种高性能汽车转向系统中横拉杆接头用钢,由以下质量百分比元素组成：0.49～0.53%的C、0.25～0.40%的Si、0.70～0.90%的Mn、0.30～0.40%的Cr、0.045～0.060%的Mo、0～0.30%的Ni、0.015～0.035%的Al、0.015～0.030%的S、0.0080～0.0110%的N、0.010～0.025%的Nb、≤0.015%的P、≤0.0008%的B、≤0.0020%的O、≤0.0002%的H,余量为Fe。本发明钢种不仅使用规格大,而且具有高强度、高低温冲击性能,用于加工各种形状横接头,加工的横接头力学性能优良,切削性能好,同时该发明钢种对于工艺的适应性较强,在常规钢铁企业的工艺流程(转炉或电炉+炉外精炼+连铸+轧制)中都可以生产。(The invention discloses steel for a tie rod joint in a high-performance automobile steering system, which consists of the following elements in percentage by mass: 0.49-0.53% of C, 0.25-0.40% of Si, 0.70-0.90% of Mn, 0.30-0.40% of Cr, 0.045-0.060% of Mo, 0-0.30% of Ni, 0.015-0.035% of Al, 0.015-0.030% of S, 0.0080-0.0110% of N, 0.010-0.025% of Nb, less than or equal to 0.015% of P, less than or equal to 0.0008% of B, less than or equal to 0.0020% of O, less than or equal to 0.0002% of H, and the balance of Fe. The steel grade has large using specification, high strength, high and low temperature impact performance, is used for processing transverse joints with various shapes, has excellent mechanical property of the processed transverse joints and good cutting performance, has stronger adaptability to the process, and can be produced in the process flows (converter or electric furnace + external refining + continuous casting + rolling) of conventional steel enterprises.)

1. The steel for the tie rod joint in the high-performance automobile steering system is characterized by comprising the following elements in percentage by mass: 0.49-0.53% of C, 0.25-0.40% of Si, 0.70-0.90% of Mn, 0.30-0.40% of Cr, 0.045-0.060% of Mo, 0-0.30% of Ni, 0.015-0.035% of Al, 0.015-0.030% of S, 0.0080-0.0110% of N, 0.010-0.025% of Nb, less than or equal to 0.015% of P, less than or equal to 0.0008% of B, less than or equal to 0.0020% of O, less than or equal to 0.0002% of H, and the balance of Fe.

2. The steel for tie rod joints in high performance automobile steering systems according to claim 1, wherein: the alloy consists of the following elements in percentage by mass: 0.50-0.53% of C, 0.30-0.40% of Si, 0.84-0.90% of Mn, 0.35-0.40% of Cr, 0.045-0.055% of Mo, 0.20-0.25% of Ni, 0.020-0.035% of Al, 0.015-0.025% of S, 0.0090-0.0110% of N, 0.015-0.025% of Nb, less than or equal to 0.012% of P, less than or equal to 0.0005% of B, less than or equal to 0.0015% of O, less than or equal to 0.00015% of H, and the balance of Fe.

3. The steel for tie rod joints in high performance automobile steering systems according to claim 1, wherein: the alloy consists of the following elements in percentage by mass: 0.50-0.53% of C, 0.30-0.40% of Si, 0.84-0.90% of Mn, 0.35-0.40% of Cr, 0.045-0.055% of Mo, 0.020-0.035% of Al, 0.015-0.025% of S, 0.0090-0.0110% of N, 0.015-0.025% of Nb, less than or equal to 0.012% of P, less than or equal to 0.15% of Ni, less than or equal to 0.0005% of B, less than or equal to 0.0015% of O, less than or equal to 0.00015% of H, and the balance of Fe.

Technical Field

The invention belongs to the technical field of metallurgy, relates to a tie rod joint in an automobile steering system, and particularly relates to steel for the tie rod joint in a high-performance automobile steering system.

Background

The steering system of the automobile plays a very important role in various major systems (an engine system, a suspension system and the like) of the automobile, which is related to the directionality and the safety of the automobile in the driving process, wherein a tie rod joint (hereinafter, referred to as a "cross joint") is one of components connecting a steering gear and a knuckle arm, and the steering gear transmits the steering action of a driver to the knuckle arm through the cross joint, so that the safety and the service life of the automobile steering system are directly determined by the performance of the cross joint. Generally, the improvement or enhancement of the safety of an automobile part is mainly completed through three aspects of material selection, structural design and production process, and the three measures are all to improve the product failure limit and increase the performance margin to ensure the improvement and enhancement of the safety of a transverse joint.

Referring to the related patents, it is found that all the patents relating to the automobile transverse joint are only patents relating to some processing or structural design aspects, such as: patent CN212106491U discloses a cross joint with an arc-shaped structural reinforcement rod, patent CN211764791U discloses a torsional cross joint, patent CN112412964A discloses a joint based on a steering tie rod of an automobile steering system, patent CN209700784 discloses a ball pin seat blind hole type automobile steering tie rod joint, patent CN208123243U a maintenance-free steering tie rod joint, patent CN2380465Y a wear-resistant automobile tie rod joint, and the related contents of the patents mainly refer to the design aspect of the cross joint; patent CN201582296U discloses a cross joint suitable for cold extrusion technology, which mainly describes a cross joint suitable for a specific processing technology.

In the aspect of material selection, in the prior art, 45 steel is mainly used for processing a transverse joint, a certain amount of microstructure still exists within one-half radius after the 45 steel is tempered, a near surface is sorbite, pearlite and ferrite still exist at the position of one-half radius, the consistency of the microstructure at the position of the near surface and the position of one-half radius is poor, and the structural difference enables the tensile strength and the impact toughness not to meet the high performance requirements (the raw material requirements are that the yield strength is more than or equal to 430MPa, the tensile strength is 650-800 MPa, the elongation is more than or equal to 16%, the section shrinkage is more than or equal to 40%, the 0 ℃ V-shaped impact power is more than or equal to 27J, the yield strength is more than or equal to 560MPa, the tensile strength is 800-950 MPa, and the 0 ℃ V-shaped impact power is more than or equal to 35J), a transverse joint in an automobile steering system needs to transmit torsion force in the use process, particularly, the automobile needs higher steering force when the automobile runs at low speed, and the transverse joint needs higher strength, the automobile in cold regions needs the transverse joint to have higher low-temperature toughness, and the steel for the transverse joint needs to have high strength, high toughness and the like in performance when being selected and used due to the use requirement of the transverse joint.

Therefore, the development of a special steel for a tie rod joint with high performance in an automobile steering system is urgently needed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the steel for the tie rod joint in the high-performance automobile steering system, the cross joint processed by using the steel disclosed by the invention has excellent mechanical property and good cutting property, meanwhile, the production process of the steel is strong in adaptability, the production of the steel can be completed in conventional steel enterprises, and the steel has the advantages of simple production process, low cost and good performance.

The invention is realized by the following technical scheme:

the steel for the tie rod joint in the high-performance automobile steering system comprises the following elements in percentage by mass: 0.49-0.53% of C, 0.25-0.40% of Si, 0.70-0.90% of Mn, 0.30-0.40% of Cr, 0.045-0.060% of Mo, 0-0.30% of Ni, 0.015-0.035% of Al, 0.015-0.030% of S, 0.0080-0.0110% of N, 0.010-0.025% of Nb, less than or equal to 0.015% of P, less than or equal to 0.0008% of B, less than or equal to 0.0020% of O, less than or equal to 0.0002% of H, and the balance of Fe.

The invention further improves the scheme as follows:

the steel for the tie rod joint in the high-performance automobile steering system comprises the following elements in percentage by mass: 0.50-0.53% of C, 0.30-0.40% of Si, 0.84-0.90% of Mn, 0.35-0.40% of Cr, 0.045-0.055% of Mo, 0.20-0.25% of Ni, 0.020-0.035% of Al, 0.015-0.025% of S, 0.0090-0.0110% of N, 0.015-0.025% of Nb, less than or equal to 0.012% of P, less than or equal to 0.0005% of B, less than or equal to 0.0015% of O, less than or equal to 0.00015% of H, and the balance of Fe.

The invention has the further improvement scheme that:

the steel for the tie rod joint in the high-performance automobile steering system comprises the following elements in percentage by mass: 0.50-0.53% of C, 0.30-0.40% of Si, 0.84-0.90% of Mn, 0.35-0.40% of Cr, 0.045-0.055% of Mo, 0.020-0.035% of Al, 0.015-0.025% of S, 0.0090-0.0110% of N, 0.015-0.025% of Nb, less than or equal to 0.012% of P, less than or equal to 0.15% of Ni, less than or equal to 0.0005% of B, less than or equal to 0.0015% of O, less than or equal to 0.00015% of H, and the balance of Fe.

The reason why the chemical composition of the steel for tie-rod joint in the high-performance automobile steering system of the present invention is limited is explained in detail as follows:

c: in view of the significant effect of the C element on strength, hardness and wear resistance, and the cost advantage is significant, but too high a C content can adversely affect its plasticity, while taking into account the risks of development of this steel grade. And finally, taking the C content as 0.49-0.53%.

Si: the designed and added silicon in the steel mainly utilizes the alloying action of the silicon, and the silicon content is generally required to be not less than 0.15%. Silicon is usually dissolved in ferrite or austenite in steel in a solid solution, and improves hardenability, tempering stability and oxidation resistance, but too high silicon content reduces the plasticity index of the steel and seriously decarburizes the surface of the steel by heating. After comprehensive consideration, the Si content is determined to be 0.25-0.40% in component design.

Mn: manganese can strongly improve the hardenability of steel; manganese and iron can form a solid solution to strengthen the strength of the matrix; manganese can reduce the critical transformation temperature, thereby refining pearlite and improving strength, generally the manganese content does not exceed 1.8%, and the increase of the manganese content can improve both strength and plasticity, while considering the risk of development of the steel grade. Therefore, the Mn content is determined to be 0.70-0.90%.

Mo: molybdenum can improve the hardenability of steel; molybdenum, manganese and chromium can prevent the tempering embrittlement tendency of the steel; the molybdenum improves the tempering stability of the steel, so that the steel can be tempered at a higher temperature, thereby effectively eliminating or reducing the residual stress of the steel and improving the plasticity of the steel; molybdenum also improves the corrosion resistance of the steel. Although molybdenum has a good effect of improving the mechanical property of steel, the cost of molybdenum is high, and therefore, the molybdenum is only slightly added in the design of the steel grade component in combination with the influence of the molybdenum on the cost, and the content of the molybdenum is 0.045-0.060%.

Ni: nickel can strengthen ferrite and refine pearlite without significantly affecting the plasticity of the steel; for medium carbon steel, pearlite is thinned as nickel lowers the pearlite transformation temperature; nickel can improve the fatigue resistance and reduce the sensitivity of steel to gaps; nickel reduces the low-temperature brittle transition temperature of steel and obviously improves the low-temperature impact property of the steel, but the cost of the nickel is higher. The adding amount of the nickel content can be determined according to the use environment of the transverse joint, when the transverse joint is used in a low-temperature environment, the Ni content is designed to be 0.20-0.30%, otherwise, the nickel element can not be added.

Al: aluminum is the most commonly used cheap deoxidizer, is used for deoxidation in the smelting process, and simultaneously, the existence of aluminum can balance the oxygen of steel, the higher the aluminum content is, the lower the oxygen content in the steel is, but after the aluminum content exceeds 0.060%, the oxygen content in the steel is less changed; the aluminum and the nitrogen in the steel can form a fine and dispersedly distributed refractory [ AlN ] compound which can be used for inhibiting coarsening of crystal grains, and the aluminum plays a role in refining the crystal grains in the steel according to a relation graph between [ AlN ] and the grain size; the high aluminum content also brings about a plurality of adverse effects, wherein the most adverse effects are in smelting control, and the smelting and casting are easy to generate nodulation when the aluminum content is high. By comprehensively considering the factors, the aluminum content is designed to be 0.015-0.035%.

S: the existence of sulfur element is harmful to steel products, mainly causes the problem of hot brittleness, so the content of the sulfur element is regulated to be not more than 0.035 percent in high-quality steel, but under certain conditions, the sulfur brings some beneficial effects, and the sulfur and the manganese are combined with each other to form manganese sulfide so as to improve the cutting processing performance of the steel; the sulfur has little influence on the strength of the steel, but the existence of sulfide inclusion reduces the ductility and the toughness, particularly the impact toughness; higher sulphur content will impair the corrosion resistance of the steel, but will have a less pronounced effect on the oxidation resistance of the steel. By comprehensively considering the factors, the aluminum content is designed to be 0.015-0.030%.

Nb: the function of niobium in steel is similar to that of vanadium and titanium, and mainly the coarsening temperature of crystal grains is increased and the crystal grains are refined; reducing the overheating sensitivity and the temper brittleness of the steel; niobium is unfavorable for hardenability under normal quenching conditions; the strength, the toughness and the resistance to creep of the steel are improved; and the niobium alloy is expensive. By comprehensively considering the factors, the aluminum content is designed to be 0.010-0.025%.

[ O ], [ H ], [ P ], B: the four elements are controlled as residual harmful elements by the steel grade, and considering the cost factor, the control ranges of the four residual elements in the steel grade are that O is less than or equal to 0.0020 percent, H is less than or equal to 0.0002 percent, P is less than or equal to 0.015 percent and B is less than or equal to 0.008 percent.

The invention has the beneficial effects that:

1. in the component design process of the steel, the invention considers the sulfur element in the chemical components to improve the turning performance of the product, particularly the turning performance after the heat treatment of the processed product, and simultaneously considers the influence of the addition of the sulfur element on the A-type nonmetallic inclusion in the steel, thereby influencing the toughness of the product, and the sulfur content in the steel is designed to be 0.015-0.030%.

2. In the component design of the steel grade, the nickel element is selectively added aiming at the service environment of the transverse joint, and a certain amount of nickel element is properly added aiming at the low-temperature service environment so as to improve the low-temperature performance of the transverse joint, otherwise, the nickel element is not added in consideration of the production cost.

3. The steel grade of the invention can be suitable for various automobile transverse joints, and the maximum specification of the transverse joint can be phi 60 mm.

4. After the raw material with the diameter not larger than 60mm produced by the method is subjected to overall quenching and tempering, the performance of any part of the raw material is as follows: tensile strength Rm =680-800 MPa; yield strength Rel =480-550 MPa; elongation a = 17-20%; the reduction of area Z = 50-59%; and the V-shaped impact energy KV2=35-90J at 0 ℃. After the transverse joint with the diameter not larger than 60mm is subjected to quenching and tempering, the properties are as follows: tensile strength Rm = 850-; yield strength Rel =610-700 MPa; 0 ℃, and V-shaped impact energy KV2= 38-90J. The steel grade of the invention not only has large use specification, but also has high strength and high and low temperature impact performance, and can be used for processing transverse joints with various shapes, and the processed transverse joints have excellent mechanical property and good cutting performance.

5. The steel grade has stronger adaptability to the process, and can be produced in the process flows (converter or electric furnace + external refining + continuous casting + rolling) of the conventional steel enterprises.

Drawings

FIG. 1 is a cross-joint microstructure of phi 60mm after hardening and tempering in example 1;

FIG. 2 shows a cross-joint microstructure of phi 30mm after hardening and tempering in example 2.

Detailed Description

Example 1

The steel for the tie rod joint in the high-performance automobile steering system is prepared by adopting the following process:

after smelting in a converter or an electric furnace, carrying out external refining treatment in an LF furnace and a vacuum furnace, carrying out conventional calcium modification treatment after LF refining, feeding a certain amount of pyrite into molten steel after the vacuum treatment is finished, casting the molten steel into a square billet on an arc continuous casting machine, heating the billet, and rolling the billet in a continuous rolling machine into a corresponding specification.

The chemical composition of the steel material obtained in this example: 0.50% of C, 0.30% of Si, 0.79% of Mn0.32% of Cr0.32%, 0.049% of Mo0.020% of Al, 0.010% of P, 0.018% of S, 0.015% of Nb0.23% of Ni, 0.0005% of B, 0.0010% of O, 0.00013% of H, 0.0095% of N and the balance of Fe. Casting a section: phi 200mm, rolled steel specification: phi 60 mm.

Taking the obtained raw material to prepare a transverse joint, carrying out thermal refining on the raw material and the transverse joint integrally, wherein the thermal refining temperature is 860 ℃ quenching and 640 ℃ tempering, the mechanical properties of the raw material and the transverse joint after thermal refining are shown in tables 1 and 2, and the microstructure of the transverse joint after thermal refining is shown in figure 1.

TABLE 1 phi 60mm raw material mechanical property

TABLE 2 phi 60mm cross joint mechanical properties

As can be seen from tables 1 and 2, the phi 60mm steel produced by the steel grade of the invention and the transverse joint processed by the steel grade completely meet the requirements of the high-performance transverse joint in terms of mechanical properties after quenching and tempering, and have larger margin of performance indexes.

As can be seen from FIG. 1, the microstructure of the cross joint at the near surface and at one-half radius after hardening and tempering has better consistency.

Example 2

By adopting the same production process as in example 1, the chemical composition of the obtained steel is as follows: 0.50% of C, 0.35% of Si, 0.84% of Mn0.35% of Cr0.35%, 0.047% of Mo0.018% of Al, 0.013% of P, 0.020% of S, 0.017% of Nb0.05% of Ni0.05% of B, 0.0008% of O, 0.00015% of H, 0.0100% of N and the balance of Fe. Casting a section: phi 150mm, rolled steel specification: phi 30 mm.

Taking the obtained raw material to prepare a transverse joint, carrying out thermal refining on the raw material and the transverse joint integrally, wherein the thermal refining temperature is 860 ℃ quenching and 640 ℃ tempering, the mechanical properties of the raw material and the transverse joint after thermal refining are shown in tables 3 and 4, and the microstructure of the transverse joint after thermal refining is shown in figure 2. :

TABLE 3 mechanical properties of 30mm log

TABLE 4 phi 30mm cross joint mechanical properties

As can be seen from tables 3 and 4, the phi 30mm steel produced by the steel grade of the invention and the transverse joint processed by the steel grade completely meet the requirements of the high-performance transverse joint in terms of mechanical properties after quenching and tempering, and have larger margin of performance indexes.

As can be seen from FIG. 2, the microstructure of the cross joint at the near surface and at one-half radius after hardening and tempering has better consistency.