Thick-specification 380MPa-grade automobile spoke steel with good weldability and production method of thick-specification 380MPa-grade automobile spoke steel

Abstract

The invention discloses thick 380 MPa grade automobile spoke steel with good weldability and a production method of the thick 380 MPa grade automobile spoke steel. The thick 380 MPa grade automobile spoke steel comprises the following chemical components in percentage by mass: 0.05 to 0.07 percent of C, 0.03 to 0.10 percent of Si, 0.90 to 1.05 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.035 to 0.050 percent of Alt, 0.0008 to 0.0020 percent of Ca and the balance of Fe and inevitable impurities. The microstructure of the thin-gauge and thick-gauge 380MPa-grade automobile spoke steel is composed of ferrite and a small amount of pearlite, and the thin-gauge and thick-gauge 380MPa-grade automobile spoke steel not only has good matching of high strength and high toughness, but also has the advantages of good welding performance and excellent cold machining forming.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical material production, and in particular relates to a thick-gauge 380MPa grade automobile spoke steel with good weldability and a production method thereof. Background Art

[0002] Under the dual pressures of rapid economic development and resource shortage, energy crisis and environmental protection, people's development requirements for automobiles are safety, energy saving, environmental protection, comfort and low cost. With the development of the commercial vehicle transportation industry, wheels are an important part of the vehicle, and their performance and quality have an important impact on the overall performance of the vehicle. Therefore, the demand for wheel steel is also increasing, especially in terms of strength, toughness and wear resistance. 380MPa grade thick specification wheel steel has been widely used in the field of commercial vehicle wheel manufacturing due to its high strength and good comprehensive performance. With the continuous development of the commercial vehicle transportation industry, the performance and quality requirements of wheel steel are also getting higher and higher. In the future, the research and development direction of thick specification 380MPa wheel steel will focus more on improving its strength, toughness and wear resistance, and explore new production processes and micro-alloying technologies to further improve the comprehensive performance and service life of wheel steel. In summary, as a high-performance commercial vehicle wheel material, thick specification 380MPa wheel steel has unique requirements and advantages in production process, chemical composition design and performance characteristics. With the advancement of technology and the development of the market, its application prospects will be broader.

[0003] Patent publication number CN 112662855 A (hereinafter referred to as document 1) discloses a method for improving the low-temperature impact toughness of 380MPa grade hot-rolled wheel steel. First, the invention mainly introduces the controlled rolling and controlled cooling process of the intermediate billet, but does not explain the specific thickness of the intermediate billet; secondly, the invention does not clearly list key process parameters such as specific chemical element content, heating temperature, soaking temperature, furnace temperature and coiling temperature.

[0004] Patent publication number CN 111057951 A (hereinafter referred to as document 2) discloses a 380MPa grade automobile wheel steel hot-rolled pickled plate and its production method. The patent improves the strength by adding vanadium and titanium elements to the steel to meet the performance requirements of the wheel steel. The addition of vanadium and titanium alloy elements increases the alloy cost of the wheel steel, and then the surface quality is ensured by pickling, which further increases the manufacturing cost.

[0005] Patent Publication No. CN 109628839 A (hereinafter referred to as Document 3) discloses a wheel steel with excellent welding performance and a production method, wherein the main chemical composition ratio is C: 0.031-0.061%, Si: 0.25-0.35%, Mn: 1.35-1.55%, Nb: 0.010-0.020%; Als: 0.015-0.045%, P≤0.005%, S≤0.0015%. Although the wheel steel described in the invention has higher strength than the present invention, the strength is mainly improved by increasing the content of alloy elements Si and Mn, and the precious metal element Nb is added. Due to the excessively high Si content, not only the welding performance is reduced, but also a large amount of red rust is generated, resulting in poor surface quality. The high Mn content is easy to segregate and form a banded structure, making the mechanical properties of the material anisotropic, and the cross-sectional shrinkage rate is seriously reduced, which has an adverse effect on the subsequent processing and use of the steel. In addition, the high Mn content will deteriorate the welding performance of the steel. Summary of the invention

[0006] In view of the problems existing in the prior art, and in order to meet the market demand for automobile wheel spoke steel, further expand the market share, and enrich the product variety structure, based on advanced equipment and process characteristics, the present invention adopts reasonable composition design and process technology to provide a thick specification 380MPa grade automobile wheel spoke steel with good weldability. The production results and user use effects show that all performances of the product meet the relevant technical requirements and user use requirements. The present invention is specifically implemented through the following technical solutions.

[0007] In a first aspect, the present invention provides a thick-gauge 380MPa grade automobile spoke steel with good weldability, the chemical composition of which is as follows by mass percentage: C: 0.05-0.07%, Si: 0.03-0.10%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0008-0.0030%, and the remainder is Fe and unavoidable inclusions;

[0008] The mechanical properties of the thick-gauge 380MPa grade automobile spoke steel meet the following requirements: yield strength 326-340MPa, tensile strength 410-436MPa, and elongation 30-34%; and

[0009] The thickness of the thick-gauge 380MPa grade automobile spoke steel is above 16.0mm.

[0010] In some embodiments, the chemical composition of the thick-gauge 380 MPa grade automobile spoke steel is, by mass percentage, C: 0.05-0.07%, Si: 0.03-0.05%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0010-0.0030%, and the rest is Fe and unavoidable inclusions.

[0011] In some embodiments, the chemical composition of the thick-gauge 380 MPa grade steel for automobile spokes is, by mass percentage, C: 0.060%, Si: 0.05%, Mn: 0.90%, P: 0.015%, S: 0.005%, Alt: 0.050%, Ca: 0.0030%, and the rest is Fe and unavoidable inclusions.

[0012] In some embodiments, the chemical composition of the thick-gauge 380 MPa grade automobile spoke steel is, by mass percentage, C: 0.070%, Si: 0.03%, Mn: 1.00%, P: 0.010%, S: 0.003%, Alt: 0.045%, Ca: 0.0020%, and the rest is Fe and unavoidable inclusions.

[0013] In some embodiments, the chemical composition of the thick-gauge 380 MPa grade steel for automobile spokes is, by mass percentage, C: 0.050%, Si: 0.04%, Mn: 1.05%, P: 0.012%, S: 0.004%, Alt: 0.035%, Ca: 0.0010%, and the rest is Fe and unavoidable inclusions.

[0014] In some embodiments, the thickness of the thick-gauge 380 MPa grade steel for automobile spokes is 16.0-18.0 mm.

[0015] In some embodiments, the microstructure of the thick-gauge 380 MPa grade steel for automobile spokes is composed of ferrite and a small amount of pearlite.

[0016] In a second aspect, the present invention provides a method for producing thick-gauge 380 MPa grade automobile spoke steel, which comprises the following processes: smelting - continuous casting - slab heating - rolling - cooling - coiling; wherein:

[0017] The smelting-continuous casting process comprises: KR desulfurization-converter-LF refining-RH vacuum treatment-slab continuous casting-slow cooling, and the composition of the molten steel supplied to the casting machine is C: 0.05-0.07%, Si: 0.03-0.10%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0008-0.0020%, and the rest is Fe and unavoidable inclusions;

[0018] The slab heating process includes: sending the slab after surface cleaning into the heating furnace, strictly controlling the slab heating temperature, furnace time, soaking temperature, soaking time and furnace discharge temperature, the heating temperature is controlled at 1200±20°C, the furnace time is controlled at 160-270min, the soaking temperature is controlled at 1200±20°C, the soaking time is controlled at 25-50min, and the furnace discharge temperature is controlled at 1180±20°C;

[0019] The rolling process includes a rough rolling stage and a finishing rolling stage. The rough rolling stage adopts a 3+3 mode two-stand rolling mill for rough rolling, and the finishing stage adopts a 7-stand continuously variable crown (CVC) rolling mill for finishing rolling. The finishing stage adopts speed increase rolling; the finishing rolling entrance thickness is 40mm, the starting rolling temperature of the finishing rolling is not less than 1020°C, and the final rolling temperature of the finishing rolling is 860±15°C;

[0020] The cooling process adopts laminar cooling equipment, and the cooling mode adopts the self-learning calculation result of the computer secondary system, specifically adopts front dispersion cooling, and the cooling speed is 25-27°C / s;

[0021] The coiling temperature is 580±20°C.

[0022] The present invention provides a thick specification 380MPa grade automobile wheel spoke steel with good weldability through reasonable component design and combined with optimized production process parameters. The microstructure of the product is composed of ferrite and a small amount of pearlite, and the mechanical properties are as follows: yield strength 326-340MPa, tensile strength 420-436MPa, and elongation 30-34%. The product not only has a good match of high strength and high toughness, but also has good welding performance and excellent cold processing forming advantages. At the same time, it shows excellent fatigue resistance under the conditions of heavy load or high-speed operation of commercial vehicles. In addition, the production method of the product is simple and easy, suitable for industrial mass production, and various performances meet the requirements of relevant standards and user needs. Furthermore, unlike the above-mentioned document 1, the present invention not only clarifies the specific thickness of the intermediate billet, but also lists the key process parameters such as the specific chemical composition and various temperatures; unlike the above-mentioned document 2, the present invention adopts the C-Mn component system for hot-rolled delivery and has good surface quality, thereby reducing the production cost of the product; unlike the above-mentioned document 3, the component design of the present invention does not contain Nb, and the addition amounts of Si and Mn are relatively low, which not only improves the surface quality and welding performance, but also reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a microstructural photograph of the thick-gauge 380 MPa grade automobile wheel spoke steel with good weldability produced in Example 1. DETAILED DESCRIPTION

[0024] The purpose of the present invention is to provide a thick-gauge 380MPa grade automobile wheel spoke steel with good weldability and a production method thereof. The thick-gauge 380MPa grade automobile wheel spoke steel mentioned in the present invention has a reasonable chemical composition design and has the characteristics of high strength, good toughness and wear resistance. These performance characteristics enable it to meet the use requirements of commercial vehicle wheels under complex road conditions.

[0025] The present invention is described in detail below through specific examples. The examples are intended to help understand the present invention but are not intended to limit the present invention.

[0026] Example 1

[0027] The molten iron is pre-treated for desulfurization, and the top and bottom combined blown converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1645℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1560℃. The LF refining outside the furnace is subjected to temperature measurement and composition fine-tuning. The chemical composition of the LF refining casting machine is shown in Table 1. The overheat of the slab continuous casting is 27℃, and then the slab is cleaned, slowly cooled, and the quality of the continuous casting is checked. The slab heating temperature is 1215℃, and the heating time is 258min. The heated slab is dephosphorized by high-pressure water. The width is set by a fixed width press, and 2-stand rough rolling and 7-stand CVC finishing rolling are used. The finishing rolling start temperature is 1031℃, the finishing rolling final rolling temperature is 860℃, and the finished product thickness is 16.0mm. Laminar cooling uses front dispersion cooling, cooling rate is 27℃ / s, the temperature of the steel strip is reduced to 580℃ for coiling, and finally the product performance test is carried out, as shown in Table 2 below. Figure 1 , which shows the microstructure of the thick gauge automobile spoke steel obtained in this embodiment, and it can be seen that the microstructure is ferrite and a small amount of pearlite.

[0028] Example 2

[0029] The molten iron is pre-treated for desulfurization, and the top and bottom combined blown converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, scrap steel is added to the converter, and the converter tapping temperature is 1641℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1562℃. The LF refining outside the furnace is subjected to temperature measurement and composition fine-tuning. The chemical composition of the LF refining casting machine is shown in Table 1. The overheat of the slab continuous casting is 32℃, and then the slab is cleaned, slowly cooled, and the quality of the continuous casting is checked. The slab heating temperature is 1220℃, the heating time is 263min, and the heated slab is dephosphorized by high-pressure water. The width is set by a fixed width press, and 2-stand rough rolling and 7-stand CVC finishing rolling are used. The finishing rolling start temperature is 1030℃, the finishing rolling final temperature is 870℃, and the finished product thickness is 17.0mm. Laminar cooling adopts front dispersion cooling with a cooling rate of 26°C / s. The temperature of the steel strip is reduced to 590°C for coiling, and finally the product performance is tested, as shown in Table 2 below.

[0030] Example 3

[0031] The molten iron is pre-treated for desulfurization, and the top and bottom combined blown converter is used to decarbonize and dephosphorize the molten iron to obtain molten steel. Argon is blown throughout the converter smelting process, and scrap steel is added to the converter. The converter tapping temperature is 1652℃. Then the molten steel after converter smelting is subjected to LF refining outside the furnace, and the refining temperature is ≥1563℃. The LF refining outside the furnace is subjected to temperature measurement and composition fine-tuning. The chemical composition of the LF refining casting machine is shown in Table 1. The overheat of the slab continuous casting is 31℃, and then the slab is cleaned, slowly cooled, and the quality of the continuous casting is checked. The slab heating temperature is 1218℃, the heating time is 257min, and the heated slab is dephosphorized by high-pressure water. The width is set by a fixed width press, and 2-stand rough rolling and 7-stand CVC finishing rolling are used. The finishing rolling start temperature is 1032℃, the finishing rolling final rolling temperature is 873℃, and the finished product thickness is 18.0mm. Laminar cooling adopts front dispersion cooling with a cooling rate of 25°C / s. The temperature of the steel strip is reduced to 585°C for coiling, and finally the product performance is tested, as shown in Table 2 below.

[0032] Comparative Example 1

[0033] The production method is the same as that shown in Example 1, except that the chemical composition of the LF refining feed casting machine is different from that used in Example 1, as shown in Table 1. Finally, the product performance test is carried out, as shown in Table 2.

[0034] Comparative Example 2

[0035] The production method of Comparative Example 2 is the same as that of Example 3, except that the coiling temperature is different from that of Example 3, specifically, the coiling temperature of Comparative Example 2 is 520° C. Finally, the product performance is tested, as shown in Table 2 below.

[0036] Table 1: Chemical composition (wt%) of Examples 1 to 3 of the present invention and Comparative Examples 1 to 2

[0037] Example C Si Mn P S Alt Ca 1 0.060 0.05 0.90 0.015 0.005 0.050 0.0030 2 0.070 0.03 1.00 0.010 0.003 0.045 0.0020 3 0.050 0.04 1.05 0.012 0.004 0.035 0.0010 Comparative Example 1 0.060 0.05 0.60 0.015 0.005 0.050 0.0030 Comparative Example 2 0.050 0.04 1.05 0.012 0.004 0.035 0.0010

[0038] Table 2: Mechanical properties of the steel coils of Examples 1 to 3 of the present invention and Comparative Examples 1 to 2

[0039]

[0040] It can be seen from the contents recorded in Tables 1 and 2 above that the mechanical properties of the thick-gauge 380MPa grade automobile spoke steel provided by the present invention can meet the following requirements: yield strength ≥220MPa, tensile strength 380-480MPa, elongation ≥25%, preferably: yield strength 326-340MPa, tensile strength 410-436MPa, elongation 30-34%. The product not only has a good match of high strength and high toughness, but also has good welding performance and excellent cold working forming advantages. At the same time, it exhibits excellent fatigue resistance under the conditions of heavy load or high-speed operation of commercial vehicles. In addition, the production method of the product is simple and easy, suitable for industrial mass production, and all performances meet the requirements of relevant standards and user needs. According to the test results of Comparative Example 1, when the chemical composition of the product cannot meet the requirements of the present invention, the mechanical properties of the product will be unqualified. For example, when the Mn content in Comparative Example 1 is lower than the standard requirement, the strength of the product obtained is lower than the standard requirement, which cannot meet the user's needs. According to the results of Comparative Example 2, when the chemical composition of the product meets the requirements of the present invention, but the production process cannot meet the requirements of the present invention, for example, when the coiling temperature is lower than the set value, the performance of the obtained product cannot meet the requirements. The low coiling temperature in Comparative Example 2 leads to high strength and cracking in the bending test, which cannot meet the user's needs.

[0041] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thick gauge 380MPa grade automobile wheel spoke steel with good weldability, the chemical composition of which is as follows by mass percentage: C: 0.05-0.07%, Si: 0.03-0.10%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0008-0.0030%, and the remainder is Fe and unavoidable inclusions; The mechanical properties of the thick-gauge 380MPa grade automobile spoke steel meet the following requirements: yield strength 326-340MPa, tensile strength 410-436MPa, and elongation 30-34%; and The thickness of the thick-gauge 380MPa grade automobile spoke steel is above 16.0mm.

2. The thick-gauge 380 MPa grade automobile spoke steel according to claim 1, wherein the chemical composition, by mass percentage, is: C: 0.05-0.07%, Si: 0.03-0.05%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0010-0.0030%, and the remainder is Fe and unavoidable inclusions.

3. The thick-gauge 380 MPa grade automobile spoke steel according to claim 1 or 2, wherein the chemical composition, by mass percentage, is: C: 0.060%, Si: 0.05%, Mn: 0.90%, P: 0.015%, S: 0.005%, Alt: 0.050%, Ca: 0.0030%, and the remainder is Fe and unavoidable inclusions.

4. The thick-gauge 380 MPa grade automobile spoke steel according to claim 1 or 2, wherein the chemical composition, by mass percentage, is: C: 0.070%, Si: 0.03%, Mn: 1.00%, P: 0.010%, S: 0.003%, Alt: 0.045%, Ca: 0.0020%, and the remainder is Fe and unavoidable inclusions.

5. The thick-gauge 380 MPa grade automobile spoke steel according to claim 1 or 2, wherein the chemical composition, by mass percentage, is: C: 0.050%, Si: 0.04%, Mn: 1.05%, P: 0.012%, S: 0.004%, Alt: 0.035%, Ca: 0.0010%, and the remainder is Fe and unavoidable inclusions.

6. The thick gauge 380 MPa grade steel for automobile spokes according to any one of claims 1 to 5, wherein the thickness is 16.0 to 18.0 mm.

7. The thick gauge 380 MPa grade automobile wheel spoke steel according to any one of claims 1 to 6, wherein the microstructure thereof is composed of ferrite and a small amount of pearlite.

8. The method for producing thick-gauge 380 MPa grade automobile spoke steel according to any one of claims 1 to 7, comprising the following process: Smelting - continuous casting - slab heating - rolling - cooling - coiling; among which: The smelting-continuous casting process comprises: KR desulfurization-converter-LF refining-RH vacuum treatment-slab continuous casting-slow cooling, and the composition of the molten steel supplied to the casting machine is C: 0.05-0.07%, Si: 0.03-0.10%, Mn: 0.90-1.05%, P≤0.015%, S≤0.005%, Alt: 0.035-0.050%, Ca: 0.0008-0.0020%, and the rest is Fe and unavoidable inclusions; The slab heating process includes: sending the slab after surface cleaning into the heating furnace, strictly controlling the slab heating temperature, furnace time, soaking temperature, soaking time and furnace discharge temperature, the heating temperature is controlled at 1200±20°C, the furnace time is controlled at 160-270min, the soaking temperature is controlled at 1200±20°C, the soaking time is controlled at 25-50min, and the furnace discharge temperature is controlled at 1180±20°C; The rolling process includes a rough rolling stage and a finishing rolling stage. The rough rolling stage adopts a 3+3 mode two-stand rolling mill for rough rolling, and the finishing stage adopts a 7-stand continuous variable crown rolling mill for finishing rolling. The finishing stage adopts speed increase rolling; the finishing rolling entrance thickness is 40mm, the starting rolling temperature of the finishing rolling is not less than 1020°C, and the final rolling temperature of the finishing rolling is 860±15°C; The cooling process adopts laminar cooling equipment, and the cooling mode adopts the self-learning calculation result of the computer secondary system; The coiling temperature is 580±20°C.

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