Low-cost high-strength steel for automobile axle housings and method for producing the same

Abstract

The application provides a low-cost high-strength steel for automobile axle housings and a preparation method thereof, which comprises the following components in percentage by weight: C: 0.05-0.10%, Si: 0.10-0.20%, Mn: 1.10-1.20%, P: 0.020% or less, S: 0.008% or less, Nb: 0.020-0.030%, Ti: 0.040-0.055%, Als: 0.015-0.055%, N: 0.005% or less, and the balance of Fe and inevitable impurities; the preparation method comprises the following steps: heating, rough rolling, finish rolling, laminar flow cooling and coiling a slab with the above components in sequence to obtain the low-cost high-strength steel for automobile axle housings. The low-cost high-strength steel for automobile axle housings has matched strength, plasticity and toughness, excellent cold forming and hot forming properties, and excellent welding and fatigue properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot rolling plate strip, in particular to a steel for automobile axle housing, and especially to a low-cost high-strength steel for automobile axle housing and a preparation method thereof. BACKGROUND

[0002] The axle housing is one of the main components of the automobile chassis system, which is used to support the frame, and the inside of the axle housing is equipped with a reducer, a differential and a transmission device for driving the wheels, etc., so it needs to have sufficient strength, good stamping forming performance and welding performance, etc. Before the manufacture of the automobile axle housing, the casting process was mostly used, but the manufacturing process of the cast axle housing is complex, the production efficiency is low, it is heavy and the cost is high. The manufacturing process of the hot-rolled steel plate stamping half-axle housing and then welding has the advantages of high production efficiency, light weight and low cost, so the hot-rolled steel plate stamping and welding axle housing has become the development direction of the manufacture of the automobile axle housing.

[0003] With the development of the manufacturing technology of the automobile axle housing and the promotion of the domestic truck load limit compulsory measures, and in order to meet the needs of the automobile industry for energy saving and weight reduction, the application of high-strength grade hot-rolled steel plate for automobile axle housing has become a major development trend of the axle housing steel, and the matching of the forming performance and high strength of the axle housing steel becomes more and more important. The stamping process of the stamping and welding axle housing is divided into cold stamping and hot stamping processes. The cold stamping process has a higher requirement for the cold forming performance of the steel plate; the hot stamping process is to heat the steel plate to about 800℃ in a medium-frequency induction furnace, then stamp and control the cooling, so the mechanical properties of the steel plate after hot stamping will decrease due to the problems such as grain coarsening, which leads to the mechanical properties of the steel plate after hot stamping being lower than the required value.

[0004] The Chinese patent with publication number 106244919A discloses a low-alloy high-strength stamping automobile axle housing steel and a production method thereof, which is composed of the following components in percentage by weight: C 0.14-0.18%, Si 0.20-0.40%, Mn 1.45-1.60%, P≤0.020%, S≤0.015%, Nb 0.038-0.045%, V 0.05-0.10%, Ti 0.015-0.030%, N≤0.0050%, Als 0.035-0.050%, and the rest is Fe and inevitable impurity elements. The product has a tensile strength of 600-650MPa, but a high content of Nb, V and Ti elements is added, the alloy composition is complex, the alloy cost is high, and the high content of C and Mn elements reduces the welding performance.

[0005] The Chinese patent with publication number 109097702A discloses a high-strength axle housing steel with good fatigue performance and welding performance and a preparation method thereof, which is composed of the following components in percentage by weight: C 0.04-0.07%, Si 0.05-0.15%, Mn 1.30-1.60%, P≤0.013%, S≤0.004%, Nb 0.045-0.070%, Ti 0.010-0.020%, N≤0.003%, Alt 0.010-0.030%, O 0.001-0.002%, and Ti-2×O-3.4×N<0.007, and the rest is Fe and inevitable impurities. The tensile strength of the product of the invention is ≥600MPa, and good fatigue performance and welding performance are realized by strict control of chemical composition and controlled rolling and controlled cooling process, but the production control difficulty is increased.

[0006] The Chinese patent with publication number 113957347B discloses a 590MPa grade thick gauge cold stamping axle housing steel and a preparation method thereof, which is composed of the following components in percentage by weight: C 0.07-0.10%, Si 0.05-0.10%, Mn 1.50-1.60%, P≤0.020%, S≤0.008%, Nb 0.030-0.040%, V 0.07-0.10%, N 0.010-0.015%, Als 0.015-0.050%, and the rest is Fe and inevitable impurity elements. The tensile strength of the product of the invention is ≥590MPa, but higher content of Nb and V elements is added, the alloy cost is high, and the welding performance is reduced due to higher content of Mn element. SUMMARY

[0007] According to the above technical problems, a low-cost high-strength automobile axle housing steel and a preparation method thereof are provided.

[0008] The technical means adopted by the present application are as follows:

[0009] A low-cost high-strength automobile axle housing steel includes the following components in percentage by weight: C: 0.05-0.10%, Si: 0.10-0.20%, Mn: 1.10-1.20%, P≤0.020%, S≤0.008%, Nb: 0.020-0.030%, Ti: 0.040-0.055%, Als: 0.015-0.055%, N≤0.005%, and the balance is Fe and inevitable impurities.

[0010] Further, the carbon equivalent CEV of the low-cost high-strength automobile axle housing steel is ≤0.30%, and the welding crack sensitivity index Pcm is ≤0.17%.

[0011] Further, the low-cost high-strength automobile axle housing steel has yield strength ≥500 MPa, tensile strength ≥600 MPa, elongation after fracture ≥20%, 180° bending test D=2a, full-size V-shaped notch longitudinal impact energy KV2 ≥150 J at 0 ℃, and part vertical bending fatigue life ≥80 million times.

[0012] Further, the low-cost high-strength automobile axle housing steel has yield strength ≥500 MPa, tensile strength ≥600 MPa, elongation after fracture ≥20%, 180° bending test D=2a, full-size V-shaped notch longitudinal impact energy KV2 ≥150 J at 0 ℃, and part vertical bending fatigue life ≥80 million times.

[0013] Further, the low-cost high-strength automobile axle housing steel has yield strength ≥500 MPa, tensile strength ≥600 MPa, elongation after fracture ≥20%, 180° bending test D=2a, full-size V-shaped notch longitudinal impact energy KV2 ≥150 J at 0 ℃, and part vertical bending fatigue life ≥80 million times.

[0014] Further, the low-cost high-strength automobile axle housing steel has yield strength ≥500 MPa, tensile strength ≥600 MPa, elongation after fracture ≥20%, 180° bending test D=2a, full-size V-shaped notch longitudinal impact energy KV2 ≥150 J at 0 ℃, and part vertical bending fatigue life ≥80 million times.

[0015] The role and mechanism of each element and main process in the application are as follows:

[0016] Carbon: Carbon is an effective strengthening element in steel, which can dissolve into the matrix to play a role of solid solution strengthening, and can form carbide precipitated particles by combining with Nb and Ti to play a role of fine-grain strengthening and precipitation strengthening. Increasing the carbon content is beneficial to improving the strength, but excessive carbon content will form a large number of coarse and brittle carbide particles in the steel, which is not conducive to plasticity and toughness. Excessive carbon content is also prone to form segregation bands in the center of the steel plate, which is not conducive to bending performance, forming performance, etc. Meanwhile, excessive carbon content will increase the welding carbon equivalent and the welding crack sensitivity index, which is not conducive to welding processing. Therefore, the value range of C in the application is set to 0.05-0.10%.

[0017] Silicon: Silicon can dissolve in ferrite and austenite to improve the hardness and strength of the steel, but excessive content will reduce the plasticity and toughness of the steel, making it difficult to remove scale during rolling, and also leading to a decrease in welding performance. Therefore, the value range of Si in the application is set to 0.10-0.20%.

[0018] Manganese: Manganese has a strong solid solution strengthening effect, can significantly reduce the phase transition temperature of the steel, and refine the microstructure of the steel, which is an important strength and toughness element. However, excessive Mn content is prone to cause cracks in the continuous casting process, may cause composition segregation in the center of the steel plate, and also reduces the welding performance of the steel. Therefore, the value range of Mn in the application is set to 1.10-1.20%.

[0019] Phosphorus and sulfur: Phosphorus and sulfur elements will have an adverse effect on the microstructure and performance of the steel plate. Excessive P content will significantly reduce the plasticity and low-temperature toughness of the steel, and S will form sulfide inclusions to deteriorate the performance of the steel. Therefore, the value range of P and S in the application is set to P ≤0.020% and S ≤0.008%.

[0020] Nb: Nb can pin the austenite grain boundary to prevent grain growth, eventually refine the grain, which is beneficial to improve impact toughness, but the fine-grain strengthening makes the yield strength rise more obviously, resulting in the increase of yield ratio and the decrease of forming performance, and the fine-grain strengthening effect will be significantly reduced after hot forming, and too high Nb content will increase the production cost; therefore, the value range of Nb in the present application is set to 0.020-0.030%.

[0021] Ti, N: Ti(C,N) precipitates formed by Ti and N can effectively refine austenite grains, produce precipitation strengthening effect, and pin the grain boundary to inhibit the microstructure coarsening during hot forming and welding, thereby ensuring the performance after hot forming and welding performance. Increasing the content of Ti element can increase the volume fraction of Ti(C,N) precipitates, but too high Ti or N element content can easily form micron-sized TiN, resulting in the decrease of forming performance and fatigue performance; therefore, the value range of Ti in the present application is set to Ti 0.040-0.055%, and the value range of N is set to N≤0.0050%.

[0022] Al: Al added to steel can improve the steel quality, but too high Al content can easily cause the oxynitride of Al to precipitate at the austenite grain boundary, resulting in the generation of cracks in the casting blank; therefore, the value range of Als in the present application is set to 0.015-0.055%.

[0023] The present application also discloses a preparation method of the low-cost high-strength steel for automobile axle housing.

[0024] Further to the heating step, the slab is heated in a regenerative heating furnace, and the slab is heated to homogenize the as-cast structure and composition segregation and to make the alloying elements solid solution, but too high heating temperature and too long heating time can cause burning, overheating and overburning problems. Therefore, the heating temperature in the heating step is set to 1200-1240 DEG C, and the heating time is set to 190-400 min.

[0025] Further to the rough rolling step, the rough rolling needs to achieve sufficient deformation to ensure austenite recrystallization, refine the austenite grains and prevent the occurrence of mixed crystal structure; if the intermediate blank thickness is too large, the rough rolling deformation may be insufficient, and the rolling load of the finish rolling increases, and if the intermediate blank thickness is too small, the finish rolling deformation may be insufficient. Therefore, the rough rolling step in the present application is set to 6 passes of rough rolling, and the deformation of each pass is≥18%; when the finished product thickness is 6.0-10.0 mm, the intermediate blank thickness is 50-54 mm; and when the finished product thickness is >10.0-16.0 mm, the intermediate blank thickness is 53-57 mm.

[0026] Further to the finishing step, the last three stands are basically rolled in the non-recrystallization region of austenite after the finishing, a large deformation rate is adopted to flatten and elongate the austenite grains which have been refined to a certain degree by rolling in the recrystallization region, increase the grain boundary area of the austenite in unit volume, and generate a large number of deformation bands and high-density dislocations in the grains, thereby increasing the nucleation rate of ferrite and obtaining fine structure after phase transition; if the finishing start rolling temperature is too high, the deformation in the non-recrystallization region of austenite during the finishing process is insufficient, which is not conducive to the refinement of the structure; if the finishing end rolling temperature is too low, the difference between the start rolling temperature and the end rolling temperature is too large, the cooling rate during the finishing process is too fast, and there is a risk of rolling in the two-phase region after the finishing, and the comprehensive performance of the product is poor; if the finishing end rolling temperature is too high, the deformation in the non-recrystallization region is insufficient, which is not conducive to the refinement of the final structure. Therefore, in the present application, seven passes of finishing are provided in the finishing step, the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively, the finishing start rolling temperature is ≤1030℃, and the finishing end rolling temperature is 850-890℃.

[0027] Specifically to the laminar cooling step, the front section cooling mode is adopted to achieve a large supercooling degree to refine the final structure, and a large cooling rate is adopted to improve the center banded structure to some extent, and is also conducive to the precipitation of fine and dispersed second phase to enhance the effects of fine-grain strengthening and precipitation strengthening. Therefore, the front section cooling mode is adopted in the present application, and the cooling rate is 60-100℃ / s.

[0028] Specifically to the coiling step, if the coiling temperature is too low, the cooling rate during the cooling process will be too large, which will lead to abnormal structure and inhibit the supersaturation precipitation of TiC in ferrite to reduce the volume fraction of TiC particles; if the coiling temperature is too high, the grains will be coarse, and the TiC particles will also be coarsened. Since the precipitation strengthening increment of the precipitated phase is related to the volume fraction and size of the particles, the precipitation strengthening increment increases with the increase of the volume fraction and the decrease of the size of the precipitated particles, therefore, by selecting a suitable coiling temperature range, the dispersed and nanoscale TiC particles formed by the supersaturation precipitation of Ti element in ferrite during the coiling stage can significantly improve the precipitation strengthening effect of Ti element. Therefore, in the present application, the coiling temperature is set to 600-640℃.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] The present application plays the fine-grain strengthening and precipitation strengthening effect by adding a certain amount of Ti element combined with controlled rolling and controlled cooling process, thereby reducing the Nb and Mn elements while ensuring the strength performance, reducing the alloy cost, and the carbon equivalent and the welding crack sensitivity index of the product. Meanwhile, the addition of Ti element can pin the grain boundary through its precipitates to inhibit the microstructure coarsening in the hot forming process and the welding process, thereby ensuring the performance after hot forming and the welding performance. The automobile axle housing steel prepared by the composition and the preparation method of the present application has the yield strength ≥500 MPa, the tensile strength ≥600 MPa, the elongation after fracture ≥20%, the 180° bending test D=2a, the full-size V-shaped notch longitudinal impact energy KV2 ≥150 J at 0℃, the vertical bending fatigue life of the part ≥800,000 times, and the strength decrease after heating to 800℃ for 3 min and then air cooling to room temperature is less than 50 MPa, realizing the excellent matching of strength, plasticity and toughness, and having excellent cold forming and hot forming performance, and excellent welding performance and fatigue performance.

[0031] Based on the above reasons, the present application can be widely popularized in the field of low-cost high-strength automobile axle housing steel and the like. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0033] Figure 1 The metallographic structure diagram of the low-cost high-strength automobile axle housing steel in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments. In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0035] For the purpose of facilitating the understanding of the present application, the present application is further illustrated below in combination with examples and comparative examples.

[0036] The low-cost high-strength steel for automobile axle housing disclosed in the present application comprises the following components in percentage by weight: C 0.05-0.10%, Si 0.10-0.20%, Mn 1.10-1.20%, P≤0.020%, S≤0.008%, Nb 0.020-0.030%, Ti 0.040-0.055%, Als 0.015-0.055%, N≤0.005%, and the balance of Fe and inevitable impurities.

[0037] For the purpose of further understanding the present application, three groups of examples and two groups of comparative examples are provided to illustrate the composition and preparation method of the low-cost high-strength steel for automobile axle housing according to the present application.

[0038] The carbon equivalent of the steel for automobile axle housing is:

[0039] CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15.

[0040] The weld crack sensitivity index of the steel for automobile axle housing is:

[0041] Pcm=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B.

[0042] The yield strength, tensile strength and elongation after fracture of the steel for automobile axle housing are tested according to the "Metallic Materials Tensile Testing-Part 1: Method of Test at Room Temperature" (GB / T 228.1); the bending property is tested according to the "Metallic Materials Bending Test Method" (GB / T 232); and the impact property is tested according to the "Metallic Materials Charpy Pendulum Impact Test Method" (GB / T 229).

[0043] Example 1

[0044] A low-cost high-strength steel for automobile axle housing, the chemical composition of which is shown in Table 1, and the balance is Fe and inevitable impurities.

[0045] The application discloses a preparation method of a low-cost high-strength steel for an automobile axle housing. Figure 1

[0046] Example 2

[0047] The low-cost high-strength steel for the automobile axle housing contains the chemical components shown in Table 1, and the balance is Fe and inevitable impurities.

[0048] The application discloses a preparation method of a low-cost high-strength steel for an automobile axle housing.

[0049] Example 3

[0050] The low-cost high-strength steel for the automobile axle housing contains the chemical components shown in Table 1, and the balance is Fe and inevitable impurities.

[0051] ​A preparation method of a low-cost high-strength automobile axle housing steel, according to the composition, a conventional method is used to smelt into a slab, the slab obtained by smelting is continuously processed, and heating, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed, and the specific processing process is as follows: the heating temperature is 1220 DEG C, and the heating time is 230 min; after 6 rough rolling passes, the deformation of each pass is greater than or equal to 18%, and the intermediate blank thickness is 56 mm; after 7 finish rolling passes, the reduction of the last three racks is greater than or equal to 17%, greater than or equal to 13% and greater than or equal to 10% respectively, the finish rolling opening rolling temperature is 1050-1030 DEG C, and the finish rolling temperature is 850-880 DEG C; the front cooling mode is used, the cooling speed is about 60 DEG C / s, and the coiling temperature is 600-630 DEG C. The metallographic structure is ferrite + pearlite, the volume fraction of ferrite is 94%, and the volume fraction of pearlite is 6%.

[0052] Comparative Example 1 (Comparative Example 1 specifically refers to Example 3 in “A low-alloy high-strength stamping automobile axle housing steel and a production method thereof” (CN106244919A))

[0053] An automobile axle housing steel, the chemical components are shown in Table 1, and the balance is Fe and inevitable impurities.

[0054] A preparation method of an automobile axle housing steel, according to the composition, a conventional method is used to smelt into a slab, the slab obtained by smelting is continuously processed, and heating, rough rolling, finish rolling, air cooling and coiling are sequentially performed, and the specific processing process is as follows: the heating temperature is 1188 DEG C, the rough rolling opening rolling temperature is 1030 DEG C, the finish rolling opening rolling temperature is 944 DEG C, the finish rolling temperature is 882 DEG C, the reduction of the finish rolling stage is greater than or equal to 60%, the post-rolling is not controlled cooling, and the air cooling is performed to room temperature. The metallographic structure is ferrite + pearlite.

[0055] Comparative Example 2 (Comparative Example 2 specifically refers to Example 4 in “High-strength axle housing steel with good fatigue performance and welding performance and preparation method thereof” (CN109097702A))

[0056] An automobile axle housing steel, the chemical components are shown in Table 1, and the balance is Fe and inevitable impurities.

[0057] A preparation method of an automobile axle housing steel, the smelting process adopts an RH process and performs Si-Ca treatment, the continuous casting speed is controlled to be 1.2 m / min, the continuous casting water amount is 4012 L / min, and electromagnetic stirring is used; the slab obtained by smelting is continuously processed, and heating, rough rolling, finish rolling, laminar cooling and coiling are sequentially performed, and the specific processing process is as follows: the heating temperature is 1205 DEG C, the coiling temperature is 588 DEG C, the post-rolling is subjected to laminar cooling, the front cooling is used, and the water cooling cooling speed is 110 DEG C / s.

[0058] Comparative Example 3 (Comparative Example 3 specifically refers to Example 2 of "590 MPa Grade Thick Specification Cold Stamping Bridge Shell Steel and Preparation Method Thereof" (CN113957347B))

[0059] A steel for automobile axle housing, the chemical composition of which is shown in Table 1, and the balance is Fe and inevitable impurities.

[0060] A preparation method of a steel for automobile axle housing, according to the composition, a conventional method is used to smelt into a slab, and the smelted slab is continuously processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are sequentially performed. The specific processing process is as follows: the heating temperature is 1220℃, and the heating time is 222min; after 6 passes of rough rolling, the deformation amount of each pass is ≥19%, and the full-length full phosphorus removal is performed in odd passes, and the intermediate blank thickness is 55mm; after 7 passes of finishing rolling, the reduction rates of the last three racks are 18%, 13% and 10% respectively, 3 racks of cooling water are used, the finishing rolling opening temperature is 1010℃, and the final rolling temperature is 855℃; the front cooling mode is used, the cooling speed is about 25℃ / s, and the coiling temperature is 570℃. The metallographic structure is ferrite + pearlite.

[0061] Table 1 Chemical composition of examples and comparative examples (mass percentage / wt%)

[0062] C Si Mn P S Nb V Ti Alt Als N O CEV Pcm Example 1 0.06 0.15 1.13 0.010 0.004 0.023 0.049 0.032 0.0042 0.25 0.12 Example 2 0.07 0.18 1.15 0.008 0.005 0.027 0.045 0.039 0.0038 0.26 0.13 Example 3 0.08 0.13 1.17 0.011 0.003 0.025 0.051 0.028 0.0036 0.28 0.14 Comparative Example 1 0.16 0.37 1.56 0.010 0.009 0.036 0.08 0.028 0.038 0.0045 0.44 0.26 Comparative Example 2 0.059 0.08 1.45 0.007 0.0022 0.052 0.015 0.028 0.0025 0.0015 0.30 0.13 Comparative Example 3 0.09 0.06 1.53 0.013 0.003 0.035 0.08 0.032 0.013 0.36 0.18

[0063] The specific mechanical property test results of the examples and comparative examples are shown in Table 2.

[0064] Table 2 Performance test results of examples and comparative examples

[0065]

[0066]

[0067] Note 1: Bend indenter diameter D, sample thickness a;

[0068] Note 2: Impact test, half-size sample is used for Example 1, three-quarter-size sample is used for Comparative Examples 1 and 3, and full-size sample is used for Examples 2 and 3; the impact test temperature of the examples and Comparative Example 1 is 0℃, and the impact test temperature of Comparative Example 3 is -40℃;

[0069] Note 3: The heat treatment process is heating to 800℃ for 3min and then air cooling to room temperature.

[0070] According to the chemical composition in Table 1 and the performance test results of the obtained examples and comparative examples in Table 2, the alloy cost of the examples is lower, the carbon equivalent CEV and the welding crack sensitivity index Pcm are lower, the welding performance is improved, meanwhile, higher strength can be realized, the performance after hot forming is ensured, and excellent impact toughness and fatigue performance are realized. Therefore, the low-cost high-strength automobile axle housing steel and the preparation method thereof disclosed by the present application realize excellent comprehensive performance matching at a lower alloy cost through reasonable alloy composition and production process design, the production method of the product is simple, and has a good application prospect.

[0071] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A low cost high strength steel for automotive axle housings, characterized in that, The low-cost high-strength automobile axle housing steel comprises the following ingredients by weight percentage: C: 0.05-0.10%, Si: 0.10-0.20%, Mn: 1.10-1.20%, P≤0.020%, S≤0.008%, Nb: 0.020-0.030%, Ti: 0.040-0.055%, Als: 0.015-0.055%, N≤0.005%, and the balance of Fe and inevitable impurities; the carbon equivalent CEV of the low-cost high-strength automobile axle housing steel is ≤0.30%, and the welding crack sensitivity index Pcm is ≤0.17%; The low-cost high-strength automobile axle housing steel has a yield strength ≥500 MPa, a tensile strength ≥600 MPa, an elongation after fracture ≥20%, a D=2a in the 180° bending test, a full-size V-notch longitudinal impact energy KV2 at 0°C ≥150 J, and a part vertical bending fatigue life ≥80 million times; The low-cost high-strength automobile axle housing steel has a metallographic structure of ferrite + pearlite; The volume fraction of ferrite is 90-95%, and the volume fraction of pearlite is 5-10%.

2. The low-cost high-strength steel for an automobile axle housing according to claim 1, characterized by, The strength of the low-cost high-strength automobile axle housing steel decreases by less than 50 MPa after being heated to 800°C for 3 min and then air-cooled to room temperature.

3. The low-cost high-strength steel for an automobile axle housing according to claim 1, characterized by, The low-cost high-strength automobile axle housing steel has a thickness of 6.0-16.0 mm.

4. A method for producing a low-cost high-strength steel for an automobile axle housing, characterized by, The method comprises the following steps: heating, rough rolling, finish rolling, laminar cooling and coiling a slab having the ingredients of any one of claims 1-3 in sequence to obtain the low-cost high-strength automobile axle housing steel. In the heating step, the heating temperature is 1200-1240°C, and the heating time is 190-400 min. In the rough rolling step, the slab is rolled by 6 passes, and the deformation in each pass is ≥18%; when the finished product thickness is 6.0-10.0 mm, the intermediate slab thickness is 50-54 mm; and when the finished product thickness is >10.0-16.0 mm, the intermediate slab thickness is 53-57 mm. In the finish rolling step, the slab is rolled by 7 passes, and the reduction rates of the last three stands are ≥17%, ≥13% and ≥10% respectively; the finish rolling opening temperature is ≤1030°C, and the finish rolling temperature is 850-890°C. In the laminar cooling step, the front cooling mode is adopted, and the cooling speed is 60-100°C / s; in the coiling step, the coiling temperature is 600-640°C.

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