A steel for automobile wheel spokes and a method for manufacturing the same

Abstract

The application relates to the technical field of steel materials for automobile parts, in particular to a steel for automobile spokes and a preparation method thereof. The chemical components of the steel include C, Si, Mn, P, S, Cr, Nb, Ti, V and Fe; wherein the content of C is 0.10wt%-0.26wt%, the content of Si is 0.22wt%-0.30wt%, the content of Mn is 0.80wt%-1.60wt%, the content of P is <=0.015wt%, the content of S is <=0.005wt%, the content of Cr is 0.45wt%-0.75wt%, the content of Nb is 0.02wt%-0.03wt%, the content of Ti is 0.02wt%-0.05wt%, and the content of V is 0.02wt%-0.15wt%. The application solves the technical problem of poor fatigue resistance of the existing steel for automobile spokes.

Description

Technical Field

[0001] The present application relates to the technical field of steel materials for automobile parts, and in particular to steel for automobile spokes and a preparation method thereof. Background Art

[0002] Wheels are crucial safety features, acting as a link between the road surface and the chassis. The driving wheels bear the weight of the vehicle while converting the powertrain's torque output into linear pull and thrust, which are then transmitted to the road through the tires. They are crucial components for enabling the vehicle's forward and reverse movements, braking, and steering. The driven wheels, on the other hand, bear the weight of the vehicle and move forward, backward, brake, and steer as the vehicle moves. Both driving and driven wheels are subject to vibration, impact, and fatigue loads.

[0003] At present, most car spokes are made of low-strength steel plates. This is because the spoke preparation process requires complex rolling plastic deformation processing. If high-strength materials are used, it is difficult to perform deformation processing. However, due to the low strength of such spokes, their bearing capacity is low. Under complex road conditions and test loads, the ventilation holes of the spokes are subjected to harsh bending, impact, torsion, fatigue and other loads, and fatigue fractures and other accidents often occur, posing a huge traffic safety hazard.

[0004] Therefore, how to improve the fatigue resistance of the spoke is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present application provides a steel for automobile wheel spokes and a preparation method thereof, in order to solve the technical problem that the existing steel for automobile wheel spokes has poor fatigue resistance.

[0006] In a first aspect, the present application provides a steel for automobile wheel spokes, wherein the chemical composition of the steel comprises:

[0007] C, Si, Mn, P, S, Cr, Nb, Ti, V and Fe; among them,

[0008] The C content is 0.10% to 0.26% by weight, the Si content is 0.22% to 0.30% by weight, the Mn content is 0.80% to 1.60% by weight, the P content is ≤0.015% by weight, the S content is ≤0.005% by weight, the Cr content is 0.45% to 0.75% by weight, the Nb content is 0.02% to 0.03% by weight, the Ti content is 0.02% to 0.05% by weight, and the V content is 0.02% to 0.15% by weight.

[0009] Optionally, in the chemical composition of the steel, the C content is 0.18 weight % to 0.20 weight %, the Si content is 0.26 weight % to 0.30 weight %, the Cr content is 0.55 weight %, the Ti content is 0.035 weight % to 0.05 weight %, and the V content is 0.05 weight % to 0.06 weight %.

[0010] Optionally, the steel further includes at least one of the following chemical substances: VC, TiC, VN, NbC, NbN, TiN, and the diameter of the chemical substance is 2 nm to 10 nm.

[0011] Optionally, the metallographic structure of the steel includes: ferrite and bainite; wherein,

[0012] The volume fraction of ferrite is 20% to 40%, and the volume fraction of bainite is 60% to 80%.

[0013] In a second aspect, the present application provides a method for preparing steel for automobile spokes, which is used to prepare the steel described in any embodiment of the first aspect, and the method comprises:

[0014] Mechanically processing the steel substrate having the chemical composition and then preparing ventilation holes;

[0015] The ventilation holes are subjected to surface tissue strengthening treatment; wherein the strengthening treatment includes:

[0016] Under the conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment to obtain steel for automobile spokes.

[0017] Optionally, the set starting temperature is 350°C to 450°C.

[0018] Optionally, the set endpoint temperature is 50°C to 100°C.

[0019] Optionally, the step of performing warm processing and physical impact treatment on the ventilation holes under the conditions of a set starting temperature and a set end temperature to obtain the steel for automobile spokes comprises:

[0020] Under the conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment, and the process parameters in the physical impact treatment are controlled to obtain steel for automobile spokes; wherein,

[0021] The process parameters in the physical impact treatment include impact pressure and impact frequency.

[0022] Optionally, the impact pressure is ≥1500 MPa.

[0023] Optionally, the impact frequency is ≥10 Hz.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] The automotive wheel spoke steel provided in the embodiments of the present application increases the tensile strength and yield strength of the steel by limiting the addition of C, Si, and Mn, then adds Ti to refine the austenite grains and strengthen them through a first nanoparticle precipitation strengthening, adds Cr for solid solution strengthening and improves hardenability to obtain a bainite structure, then adds Nb for recrystallization and grain refinement strengthening and a second nanoparticle precipitation strengthening, and adds V for solid solution strengthening and a third nanoparticle precipitation strengthening. The nanograins 0.5 to 2 mm below the vent surface contain a large number of dislocations, deformations, and residual compressive stresses between the grains, which hinder the initiation and propagation of fatigue cracks. The fatigue durability of the spoke vents is significantly improved compared to that of ordinary spokes. This solves the technical problem of the poor fatigue resistance of existing automotive wheel spoke steel. In addition, the automotive wheel spoke steel can meet the requirements for complex deformation in the production of wheel spokes while also providing the wheel spokes with good strength, thereby improving the driving safety of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 A schematic flow chart of a method for preparing steel for automobile spokes provided in an embodiment of the present application;

[0029] Figure 2 A metallographic structure diagram of a steel for automobile spokes provided in an embodiment of the present application;

[0030] Figure 3 This is an enlarged view of the metallographic structure diagram of steel for automobile spokes provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0032] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible subranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is intended to include any cited numeral (fractional or integer) within the indicated range.

[0033] In this application, unless otherwise specified, the directional words used, such as "upper" and "lower", refer specifically to the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] In a first aspect, the present application provides a steel for automobile wheel spokes, wherein the chemical composition of the steel comprises:

[0036] C, Si, Mn, P, S, Cr, Nb, Ti, V and Fe; among them,

[0037] The C content is 0.10% to 0.26% by weight, the Si content is 0.22% to 0.30% by weight, the Mn content is 0.80% to 1.60% by weight, the P content is ≤0.015% by weight, the S content is ≤0.005% by weight, the Cr content is 0.45% to 0.75% by weight, the Nb content is 0.02% to 0.03% by weight, the Ti content is 0.02% to 0.05% by weight, and the V content is 0.02% to 0.15% by weight.

[0038] In the embodiment of the present application, the thickness of the steel for automobile wheel spokes is 4 mm to 20 mm. The purpose is: the steel is suitable for passenger car wheel spokes and commercial vehicle wheel spokes, and the thickness specification can match the chemical composition and correspond to the rolling and heat treatment processes, so as to obtain the target tissue ratio and mechanical properties; if the thickness is too large, the consistency of the tissue performance in the thickness direction may not be guaranteed, resulting in an increase in wheel weight; if the thickness is too large, it may be difficult to obtain the shape and size on the spoke.

[0039] Controlling the C content to 0.10% to 0.26% by weight has the following positive effects: C is a fundamental strengthening element in steel, and its content largely determines the tensile strength of the steel plate. Excessive C content can lead to high hardenability, resulting in excessive high-hardness martensite during subsequent welding to the wheel rim, which can easily cause cold cracking. Excessive C content can lead to insufficient steel strength, making it impossible to achieve the target bainite ratio during steel production. Specifically, the C content can be 0.10%, 0.14%, 0.18%, 0.22%, 0.26%, etc.

[0040] The positive effects of controlling the Si content to 0.22% to 0.30% by weight: Si is a solid solution strengthening element in steel, increasing its strength. If the Si content is too high, the steel plate may become brittle to a certain extent. If the Si content is too low, the target bainite microstructure ratio may not be achieved during steel production. This may also prevent the subsequent Si+Mn combined deoxidation during spoke-to-rim welding, increase the oxygen content in the weld, and reduce fatigue performance in the weld area. Specifically, the Si content can be 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, etc.

[0041] Controlling the Mn content to 0.80% to 1.60% by weight has the following positive effects: Mn improves the hardenability of the steel strip, thereby refining the microstructure. If the Mn content is too high, it can increase its segregation tendency within the steel sheet, leading to delamination defects during spoke spinning and punching. If the Mn content is too low, the hardenability of the steel sheet can be reduced, especially in the center of the sheet, where the target bainite microstructure cannot be achieved. Specifically, the Mn content can be 0.80%, 1.0%, 1.2%, 1.4%, 1.6%, etc.

[0042] The positive effect of controlling the phosphorus content to ≤ 0.015 wt% is that phosphorus can easily affect the formability of steel. A higher phosphorus content increases the likelihood of segregation, which negatively impacts fatigue performance. Specifically, the phosphorus content can be 0.015 wt%, 0.014 wt%, 0.013 wt%, etc.

[0043] The positive effect of controlling the S content to ≤ 0.005 wt% is that S easily affects the formability of steel. A higher S content increases the likelihood of segregation, which negatively impacts fatigue performance. Specifically, the S content can be 0.005 wt%, 0.0048 wt%, 0.0049 wt%, etc.

[0044] Controlling the Cr content to 0.45% to 0.75% by weight has the following positive effects: Cr can improve the hardenability of steel, facilitate the phase transformation of bainite, and have a certain solid solution strengthening effect, ensuring the thermal and aging stability of the nanostructured reinforcement layer. If the Cr content is too high, it will cause Cr to segregate into a banded distribution structure to a certain extent, producing a high-hardness layered martensite structure at the center of the steel plate thickness, reducing the uniformity of the microstructure and performance, and hindering the cold working spinning and stamping of the spokes. If the Cr content is too low, it may be impossible to achieve the target bainite structure ratio to a certain extent, resulting in insufficient strength of the final steel product. Specifically, the Cr content can be 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, etc.

[0045] Controlling the Nb content to 0.02% to 0.03% by weight has the following positive effects: Nb refines grain size, promoting recrystallization strengthening and secondary nanoparticle precipitation strengthening, while also improving the toughness of the steel. If the Nb content is too high, excessive niobium carbide precipitation may occur. Since the niobium carbide absorbs a large amount of carbon during the forming process, it reduces the stability of the austenite and prevents the target bainite ratio from being achieved. If the Nb content is too low, grain coarsening may occur, reducing strength. Specifically, the Nb content can be 0.02%, 0.025%, 0.03%, etc.

[0046] The positive effects of controlling the Ti content to 0.02% to 0.05% by weight are as follows: Ti can fix nitrogen during the solidification stage of the ingot and produce a strong primary precipitation strengthening effect, thereby improving the high-temperature plastic deformation ability of the steel. If the Ti content is too high, large TiN inclusions will form to a certain extent. The formed inclusions will separate from the matrix during mechanical plastic forming and form crack sources, thereby causing cracking of the steel; if the Ti content is too low, it will cause grain coarsening and reduce strength to a certain extent. Specifically, the Ti content can be 0.02%, 0.03%, 0.04%, 0.05%, etc.

[0047] The positive effects of controlling the V content to 0.02% by weight to 0.15% by weight are: solid solution strengthening and nanoparticle precipitation strengthening. During the warm processing in the embodiment of the present application, nano-scale particles are precipitated in the bainite crystal, and the third nanoparticle precipitation strengthening is performed. After nanostructure strengthening, the thermal stability and aging stability of the nanostructure strengthening layer are guaranteed. If the V content is too low or too low, it will lead to poor solid solution strengthening and nanoparticle precipitation strengthening effects to a certain extent. Specifically, the V content can be 0.02% by weight, 0.05% by weight, 0.08% by weight, 0.11% by weight, 0.15% by weight, etc.

[0048] In some embodiments, the chemical composition of the steel includes 0.18 wt% to 0.20 wt% of C, 0.26 wt% to 0.30 wt% of Si, 0.55 wt% of Cr, 0.035 wt% to 0.05 wt% of Ti, and 0.05 wt% to 0.06 wt% of V.

[0049] In the embodiments of the present application, preferably, the chemical composition can be controlled to be the above-mentioned content.

[0050] In some embodiments, the steel further comprises at least one of the following chemical substances: VC, TiC, VN, NbC, NbN, and TiN, and the diameter of the chemical substance is 2 nm to 10 nm.

[0051] In the examples of the present application, the chemical substance is composed of one or more of carbides and nitrides of Ti, Nb, and V. Figure 3. The positive effect of controlling the diameter size of the chemical substance to 2nm to 10nm: the chemical substance is a nanoparticle phase, a strengthening phase, and is dispersed between ferrite and bainite. When the wheel structure is loaded, the dislocation cuts through or bypasses the nanoparticles. Under the combined influence of the two mechanisms, a strengthening effect is achieved. If the particle size is too small, to a certain extent, the dislocation loop will only bypass the nanoparticles, reducing the strengthening effect; if the particle size is too large, to a certain extent, the dislocation loop will only cut through the nanoparticles, also reducing the strengthening effect. Specifically, the size can be 2nm, 4nm, 6nm, 8nm, 10nm, etc.

[0052] In some embodiments, the metallographic structure of the steel includes: ferrite and bainite; wherein the volume fraction of ferrite is 20% to 40%, and the volume fraction of bainite is 60% to 80%, see Figure 2 .

[0053] In the embodiments of the present application, controlling the ferrite volume fraction to 60% to 80% has the following positive effects: The ferrite structure imparts good toughness to the wheel spoke steel, improving its plastic deformation properties and facilitating cold mechanical forming of the spokes, such as stamping and spinning. If the volume fraction is too high, it can reduce strength and degrade load-bearing performance to a certain extent. If the volume fraction is too low, it can reduce plasticity to a certain extent, leading to forming cracking and making it difficult to process the steel into a wheel with the required shape and dimensional accuracy. Controlling the bainite volume fraction to 20% to 40% has the following positive effects: Bainite is a strengthening phase with strong grain boundary bonding strength with ferrite, which can enhance the strength of the steel. If the volume fraction is too high, it can lead to excessive grain boundary aggregation strength, weakening the metal fluidity and causing forming cracking. If the volume fraction is too low, it can reduce strength to a certain extent, thereby reducing load-bearing performance. Specifically, the volume fraction of the ferrite can be 20%, 25%, 30%, 35%, 40%, etc.; the volume fraction of the bainite can be 60%, 65%, 70%, 75%, 80%, etc.

[0054] In the second aspect, the present application provides a method for preparing steel for automobile spokes, which is used to prepare the steel described in any embodiment of the first aspect, see Figure 1 , the method comprising:

[0055] S1. Mechanically processing a steel substrate having the chemical composition to prepare ventilation holes;

[0056] S2. Performing surface tissue strengthening treatment on the ventilation holes; wherein the strengthening treatment includes:

[0057] Under the conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment to obtain steel for automobile spokes.

[0058] Before step S1 , the step of obtaining the steel matrix having the above chemical composition includes: heating, rough rolling, finish rolling, cooling and coiling the slab having the above chemical composition.

[0059] In the heating step, the final heating temperature is between 1190°C and 1290°C, and the heating time is between 150 and 250 minutes. The positive effects of controlling the final heating temperature to between 1190°C and 1290°C include ensuring sufficient heating of the slab, thereby facilitating microstructural transformation. If the temperature is too high, the grains may be excessively coarse, affecting the strength of the steel. If the temperature is too low, the rolling force during rolling may be excessive, affecting the operation of the rolling mill.

[0060] In the above-mentioned rough rolling step: the initial temperature of the rough rolling is 1180℃~1260℃, the final rolling temperature of the rough rolling is 1060℃~1200℃, and the number of rolling passes of the rough rolling is 5 to 7 times. The positive effect of controlling the initial temperature of the rough rolling to 1180℃~1260℃ is: obtaining a good austenite matrix structure, which is beneficial to the controlled rolling and controlled cooling during the steel rolling process, and the ferrite, bainite and martensite structures can be obtained in sequence. If the temperature is too high, it may lead to coarse structure, and cause decarburization and thickening of the oxide scale on the surface of the steel; if the temperature is too low, it may cause the temperature to drop too quickly between rough rolling and finishing rolling, which is not conducive to the fine control of grain size. The positive effects of controlling the finishing temperature of the rough rolling to 1060℃~1200℃ are: controlling the change of grains and removing surface iron oxide scale, thereby obtaining a reasonable finishing process temperature window; if the temperature is too high, it may lead to too high finishing temperature, making the steel grains coarse and the oxide scale thick; if the temperature is too low, it may increase the load of the rolling mill and shorten the temperature window for equalization. The positive effects of controlling the rolling passes of the rough rolling to 5~7 times are: rolling the loose shrinkage defects in the core of the ingot to obtain a good core structure; if the rolling passes are too many, the rolling temperature may drop significantly, which is not conducive to the initial temperature control of the finishing rolling; if the rolling passes are too few, the deformation rate of the slab may be too large, and bulging and warping may occur during the leveling process of the steel, which is not conducive to finishing control.

[0061] In the above-mentioned finishing rolling step: the initial temperature of the finishing rolling is 1050° C. to 1150° C., the final rolling temperature of the finishing rolling is 880° C. to 950° C., and the number of rolling passes of the finishing rolling is 6 to 7 times.

[0062] The positive effect of controlling the initial temperature of the finishing rolling process to 1050°C to 1150°C is that it achieves the appropriate rolling deformation resistance, which is beneficial for improving the plate width hit rate. If the temperature is too high, it may lead to decarburization of the steel surface and thickening of the oxide scale, making it impossible to guarantee the surface strength and surface flatness. If the temperature is too low, it may increase the steel's rolling deformation resistance, sharply increase the load on the rolling mill, and cause equipment damage. The positive effect of controlling the final rolling temperature of the finishing rolling process to 880°C to 950°C is that it achieves a wider ferrite temperature transformation range and obtains equiaxed ferrite grains, which is beneficial for the plastic forming of the spokes. If the temperature is too high, it may lead to coarse ferrite grains, thereby reducing the fine grain strengthening effect. If the temperature is too low, it may lead to flattening of the structure, making the grains inconsistent in the thickness direction, resulting in fluctuations in steel properties. The positive effect of controlling the number of finishing passes to 6-7 is that through multiple passes and small deformation, the grain size of the steel plate can be made uniform throughout the thickness, resulting in stable performance. Excessive rolling passes may lead to lower rolling temperatures, resulting in surface fine grains and increased mill load in subsequent passes. Excessive rolling passes may also result in large deformation in a single finishing pass, making it impossible to guarantee the edge quality of the steel.

[0063] In the above cooling step: the initial temperature of the cooling is 850°C to 950°C, and the terminal temperature of the cooling is 350°C to 450°C.

[0064] The positive effect of controlling the initial cooling temperature to 850°C to 950°C is that the initial transformation of ferrite is completed. If the temperature is too low, the grain size may be coarse, resulting in reduced plasticity and strength of the steel. If the temperature is too low, the structure may be flattened, resulting in large differences in the transverse and longitudinal properties of the steel.

[0065] The positive effect of cooling to a final temperature of 350°C to 450°C is that the target bainite ratio is achieved. If the temperature is too high, the bainite ratio may decrease, reducing the strength of the steel; if the temperature is too low, martensite may form, reducing the plasticity of the steel.

[0066] In the above coiling step, the coiling temperature is 350° C. to 450° C., which has the positive effect of enabling the steel plate to obtain good microstructure and properties.

[0067] In step S1, the machining can be one or a combination of forging, spinning, and stamping, with the goal of obtaining a spoke structure with varying cross-sectional thickness and dimensions. The ventilation holes can be prepared by one or a combination of stamping, hole expansion, flanging, and high-energy beam cutting, with the goal of producing a lightweight spoke structure that cools the wheel during travel. The nanograins 0.5 to 2 mm below the surface of the ventilation holes have a large number of dislocations, deformations, and residual compressive stresses between the grains, hindering fatigue crack initiation and propagation. The fatigue durability of spoke ventilation holes is significantly improved compared to ordinary spokes.

[0068] In some embodiments, the set starting temperature is 350°C to 450°C.

[0069] "Set start temperature" indicates the initial temperature of warm working. Controlling this initial temperature to 350℃~450℃ has the following positive effects: the metallographic structure of the steel will not change, but the strength will be lower than that at room temperature. During the subsequent physical impact process, the surface structure can obtain sufficient nano-phase transformation. If the temperature is too high, it will cause phase transformation to a certain extent, reduce the proportion of bainite, and the nanostructure will recover and recrystallize, thereby reducing the strength of the steel and failing to achieve the effect of nanostructure strengthening. If the temperature is too low, it will cause the depth of the nanostructure transformation layer to a certain extent, making the final metallographic structure uneven, affecting the performance stability of the wheel product. Specifically, the temperature can be 350℃, 370℃, 390℃, 410℃, 430℃, 450℃, etc.

[0070] In some embodiments, the set endpoint temperature is 50°C to 100°C.

[0071] The "set endpoint temperature" indicates the final temperature of the warm processing. Controlling this endpoint temperature to 50°C to 100°C has the positive effect of strengthening the nanostructure of the outermost layer, thereby achieving a gradient nanostructure through the thickness. If this temperature is too high, the nanostructure transformation in the outermost layer may be incomplete, resulting in less residual compressive stress. If this temperature is too low, the deformation and hardening of the outermost layer may be too intense, leading to tissue delamination. Specifically, this temperature can be 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C.

[0072] In some embodiments, the step of performing warm working and physical impact treatment on the ventilation holes under the conditions of a set starting temperature and a set end temperature to obtain steel for automobile spokes comprises:

[0073] Under the conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment, and the process parameters in the physical impact treatment are controlled to obtain steel for automobile spokes; wherein the process parameters in the physical impact treatment include: impact pressure and impact frequency.

[0074] In some embodiments, the impact pressure is ≥1500 MPa.

[0075] The positive effect of controlling the physical impact pressure to ≥1500 MPa is that the metal surface undergoes a nanostructured phase transformation, reaching the required depth and maintaining it. If the pressure is too low, the nanostructured phase transformation will be difficult to achieve and maintain. Specifically, the impact pressure can be 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, etc.

[0076] In some embodiments, the impact frequency is ≥10 Hz.

[0077] The positive effect of controlling the physical impact frequency to 10Hz or higher is that the metal surface undergoes a nanostructured phase transformation, reaching the required depth and maintaining it. If the pressure is too low, the nanostructured phase transformation may not occur or be sustained. Specifically, the impact frequency can be 10Hz, 11Hz, 12Hz, 13Hz, etc.

[0078] The automobile wheel spoke steel is realized based on the above-mentioned preparation method of the automobile wheel spoke steel. The specific steps of the preparation method of the automobile wheel spoke steel can refer to the above-mentioned embodiment. Since the automobile wheel spoke steel adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0079] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0080] Table 1 Chemical composition of steel for automobile spokes, the remainder being Fe and unavoidable impurities (wt%)

[0081]

[0082]

[0083] Table 2 Process parameters for preparing steel for automobile spokes

[0084]

[0085] Table 3 Surface microstructure strengthening treatment process parameters for automobile spoke steel

[0086]

[0087] Table 4 Properties of steel for automobile spokes

[0088]

[0089]

[0090] Test methods for related experiments:

[0091] Metallographic structure examination: Metallographic structure was examined using an OLYMPS laser confocal microscope. Hardness: Vickers hardness of each area was measured using an HVS-10Z Vickers hardness tester. Tensile strength: Tensile properties of the specimens were tested using a WE-100 tensile testing machine. Tensile strength refers to the maximum stress that the prepared steel matrix can withstand before breaking. The greater the tensile strength, the greater the maximum stress the steel plate can withstand before breaking.

[0092] From the data of Examples 1-8, it can be seen that:

[0093] If the chemical composition of the fatigue-resistant dual-phase nano-reinforced spoke steel with ventilation holes provided in this application is used, and the corresponding preparation method is used, by limiting the addition of C, Si, and Mn to improve the tensile strength and yield strength of the steel, then adding Ti to refine the austenite grains and strengthen the steel through the first nanoparticle precipitation, adding Cr for solid solution strengthening to improve the hardenability and obtain a bainite structure, then adding Nb for recrystallization and grain refinement strengthening and the second nanoparticle precipitation strengthening, and adding V for solid solution strengthening and the third nanoparticle precipitation strengthening, the metallographic structure of the steel includes ferrite, bainite, and 2-10 nm nanoparticles, and adding Cr and V to maintain the thermal stability and aging stability of the nanostructured reinforcement layer. The nanograins 0.5-2 mm below the ventilation hole surface have a large number of dislocations, deformations, and residual compressive stresses between the grains, which hinder the initiation and propagation of fatigue cracks. The wheel spokes made using the embodiment of this application have significantly improved ventilation hole fatigue durability compared to ordinary spokes.

[0094] From the data of Comparative Examples 1-2, we can see that:

[0095] If the chemical composition of the fatigue-resistant dual-phase nano-reinforced spoke steel with ventilation holes defined in this application is not adopted, and the process parameters in the corresponding preparation method are not matched, the hardness and tensile strength of the prepared steel will be lower or higher than those in the embodiment.

[0096] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A steel for automobile spokes, characterized in that: The chemical composition of the steel includes: C, Si, Mn, P, S, Cr, Nb, Ti, V and Fe; among them, a C content of 0.18 to 0.20 weight %, a Si content of 0.26 to 0.30 weight %, a Mn content of 0.80 to 1.60 weight %, a P content of 0.015 weight % or less, a S content of 0.005 weight % or less, a Cr content of 0.55 weight %, a Nb content of 0.02 to 0.03 weight %, a Ti content of 0.035 to 0.05 weight %, and a V content of 0.05 to 0.06 weight %; The steel further comprises at least one of the following chemical substances: VC, TiC, VN, NbC, NbN, TiN, and the diameter of the chemical substance is 2 nm to 10 nm; The metallographic structure of the steel includes ferrite and bainite; wherein the volume fraction of the ferrite is 20% to 40%, and the volume fraction of the bainite is 60% to 80%.

2. A method for preparing steel for automobile spokes, characterized in that: For preparing the steel according to claim 1, the method comprises: Mechanically processing the steel substrate having the chemical composition and then preparing ventilation holes; The ventilation holes are subjected to surface tissue strengthening treatment; wherein the strengthening treatment includes: Under the conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment to obtain a steel for automobile spokes; The set starting temperature is 350°C to 450°C; the set end temperature is 50°C to 100°C; The method comprises: performing a warm heat treatment and a physical impact treatment on the ventilation hole under the conditions of a set starting temperature and a set end temperature to obtain a steel for automobile spokes, comprising: Under conditions of a set starting temperature and a set end temperature, the ventilation holes are subjected to a warm processing treatment and a physical impact treatment, and process parameters in the physical impact treatment are controlled to obtain steel for automobile wheel spokes; wherein the process parameters in the physical impact treatment include: impact pressure and impact frequency; The impact pressure is ≥1500 MPa; and the impact frequency is ≥10 Hz.

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