600MPa-grade hot-rolled steel for automobile wheels and preparation method of 600MPa-grade hot-rolled steel

Abstract

The invention relates to the technical field of metallurgy or material processing, in particular to 600MPa-grade hot-rolled steel for automobile wheels and a preparation method of the 600MPa-grade hot-rolled steel. The steel comprises the following components in percentage by mass: 0.07%-0.09% of C, 0.05%-0.20% of Si, 1.35%-1.55% of Mn, 0.015%-0.060% of Als, 0.040%-0.060% of Nb, 0.020%-0.035% of Ti, less than or equal to 0.017% of P, less than or equal to 0.004% of S, less than or equal to 0.0050% of N, less than or equal to 0.0030% of O and the balance of Fe and inevitable inclusions. According to the BG600LW high-strength wheel steel produced through the method, the forming performance meets the requirements of horn mouth expanding and three-time roll forming procedures in the wheel rim machining process, cracking does not occur, and the welding performance and the fatigue performance meet the use requirements of customers.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy or material processing, and in particular to a 600MPa grade hot-rolled automobile wheel steel and a preparation method thereof. Background Art

[0002] With the development of automobile industry technology and the increase of environmental pressure, automobile lightweighting has become a development trend in the automobile industry. Lightweighting can not only significantly reduce automobile fuel consumption and greenhouse gas emissions, but also help improve the vehicle's handling and acceleration performance, extend the driving range, and is of great significance to promoting green transportation and sustainable development. As a rotating part of the car, the car wheel plays a greater role in reducing fuel consumption and emissions. According to analysis, the energy-saving effect of the wheel as a rotating part is 1.2-1.3 times that of the non-rotating part. The development of high-performance lightweight wheel materials is important and urgent.

[0003] In order to meet the urgent demand of the automotive industry for lightweight, high-strength and high-toughness wheel materials, and to cope with the increasingly diverse customer needs in the market, steel companies continue to explore and innovate, and are committed to developing new varieties of steel with excellent comprehensive performance. In this context, Bengang, as a leading domestic steel producer, actively responded to the development trend of the industry, invested a lot of R&D resources, and successfully developed a series of plain carbon steel models suitable for high-strength wheel manufacturing, including BG330CL, BG380CL, BG420CL and BG490CL. These new steels not only have high strength characteristics, but also have good plasticity and toughness, which can meet the use requirements of wheels under complex working conditions. However, the research and development and production of high-strength wheel steel is not an easy task. It requires steel mills to have extremely high technical levels, advanced production equipment and strict quality control systems. In particular, in terms of material composition design, smelting process, heat treatment process, etc., many technical difficulties need to be overcome to ensure the performance stability and consistency of the final product. Summary of the invention

[0004] The purpose of the present invention is to provide a 600MPa grade hot-rolled automobile wheel steel and a preparation method thereof. The 600MPa grade hot-rolled automobile wheel steel has a steel grade of BG600LW, has higher strength, and is beneficial to automobile weight reduction.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a 600MPa grade hot-rolled automobile wheel steel, which comprises the following components in mass percentage: C 0.07%-0.09%, Si 0.05%-0.20%, Mn 1.35%-1.55%, Als 0.015%-0.060%, Nb 0.040%-0.060%, Ti 0.020%-0.035%, P≤0.017%, S≤0.004%, N≤0.0050%, O≤0.0030%, and the balance is Fe and unavoidable inclusions.

[0007] The main elements have the following functions:

[0008] The design of low C and low Si can reduce the carbon equivalent of steel and improve the welding performance of the plate. The addition of Mn can improve the strength of the steel. The addition of Nb and Ti can play a role in fine grain strengthening and precipitation strengthening, improve the strength of the material while improving the plasticity of the material. Low N, low O, low P, and low S control can reduce inclusions and improve the material's forming performance, welding performance, and fatigue performance.

[0009] In the above technical solution, further, the yield strength of the steel is ≥540MPa, the tensile strength is ≥600MPa, and the elongation is ≥25%.

[0010] In the above technical solution, further, the metallographic structure of the steel is ferrite+pearlite.

[0011] Another aspect of the present invention provides a method for preparing the above-mentioned 600MPa grade hot-rolled automobile wheel steel, wherein the production process of the steel comprises: smelting - continuous casting - heating - hot rolling - controlled cooling - coiling; wherein:

[0012] (1) Smelting: The S of molten iron is controlled at ≤0.005% when entering the furnace, and the thickness of iron slag is ≤20mm. Aluminum iron is used for deoxidation, medium manganese and low carbon and low phosphorus ferromanganese are used for alloying, and calcium treatment is performed in the refining process;

[0013] (2) Continuous casting: ensure low superheat in the tundish, superheat ≤ 25°C, control Als to 0.02%-0.04%, and use constant casting speed control during the continuous casting process;

[0014] (3) Heating: The heating furnace is in the furnace for 2.5-4 hours, and the slab out of the furnace temperature is 1200-1270℃. The furnace atmosphere of the heating furnace is controlled to reduce the formation of iron oxide scale of the casting and ensure uniform heating temperature;

[0015] (4) Hot rolling: Rough rolling R1 final rolling temperature 965-995°C, R2 final rolling temperature 1055-1085°C, finishing rolling start temperature 1015-1045°C, final rolling temperature 845-875°C;

[0016] (5) Controlled cooling and coiling: The coiling temperature is 565-595°C, and the controlled cooling adopts the front-stage continuous cooling method.

[0017] In the above technical solution, further, during the continuous casting process, the pulling speed is 0.9-1.45m / min, and the casting is carried out under light pressure.

[0018] In the above technical solution, further, the R1 rough rolling passes are 3 times, the R2 rough rolling passes are 5 times, the total rough rolling reduction rate is 82.6-84.3%, and the thickness of the intermediate billet after rough rolling is 36-40 mm.

[0019] The beneficial effects of the present invention are:

[0020] (1) The chemical composition of the wheel steel of the present invention is based on low carbon and low silicon components, with an appropriate amount of Mn element and a small amount of Nb and Ti elements added. While ensuring high strength, it also has good toughness and obtains the required performance and structure.

[0021] (2) The present invention reduces the internal segregation of steel by controlling the purity of molten steel, so that the steel has good forming performance, welding performance and fatigue performance.

[0022] (3) The BG600LW high-strength wheel steel produced by the method of the present invention has forming properties that meet the requirements of the flaring and three-time rolling process in the process of processing the wheel rim, and no cracking occurs. The welding properties and fatigue properties meet the requirements of customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a metallographic structure photograph of the steel in Example 1. DETAILED DESCRIPTION

[0024] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0025] Example 1-2

[0026] A 600 MPa grade hot-rolled automobile wheel steel, the composition of which is shown in Table 1, and the balance is Fe and unavoidable impurities.

[0027] Table 1 Chemical composition of steel in Example 1-2 (wt%)

[0028] Example C Si Mn P S Als Nb Ti N O 1 0.08 0.10 1.44 0.012 0.002 0.027 0.044 0.028 0.0042 0.0036 2 0.08 0.12 1.41 0.009 0.002 0.030 0.044 0.029 0.0013 0.0017

[0029] The method for preparing the above-mentioned 600MPa grade hot-rolled automobile wheel steel comprises the following steps:

[0030] (1) Smelting: The S of molten iron is controlled at ≤0.005% when entering the furnace, and the thickness of iron slag is ≤20mm. Aluminum iron is used for deoxidation, medium manganese and low carbon and low phosphorus ferromanganese are used for alloying, and calcium treatment is performed in the refining process;

[0031] (2) Continuous casting: ensure low superheat in the tundish, the superheat is ≤25℃, and the Als is controlled at 0.02%-0.04%. The continuous casting process adopts constant casting speed control. During the continuous casting process, the casting speed is 0.9-1.45m / min, and the casting is lightly pressed;

[0032] (3) Heating: The heating furnace is in the furnace for 2.5-4 hours, and the slab out of the furnace temperature is 1200-1270℃. The furnace atmosphere of the heating furnace is controlled to reduce the formation of iron oxide scale of the casting and ensure uniform heating temperature;

[0033] (4) Hot rolling: R1 rough rolling final rolling temperature is 965-995°C, R2 final rolling temperature is 1055-1085°C, R1 rough rolling passes are 3 times, R2 rough rolling passes are 5 times, the total rough rolling reduction is 82.6-84.3%, the intermediate billet thickness after rough rolling is 36-40 mm, the finishing rolling start temperature is 1015-1045°C, and the final rolling temperature is 845-875°C;

[0034] (5) Controlled cooling and coiling: The coiling temperature is 565-595°C, and the controlled cooling adopts the front-stage continuous cooling method.

[0035] The main process parameters are shown in Table 2.

[0036] Table 2 Main process parameters of Example 1-2

[0037]

[0038] The performance indicators of the automobile wheel steel of Example 1-2 are shown in Table 3.

[0039] Table 3 Performance indexes of steel in Example 1-2

[0040] Example Specification / mm Yield strength ReL / MPa Tensile strength Rm / MPa Elongation A / % BG600LW - ≥540 ≥600 ≥25 1 5.0*1545 567 629 26.5 2 5.5*1545 555 616 27.0

[0041] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A 600MPa grade hot-rolled automobile wheel steel, characterized in that: The steel comprises the following components in mass percentage: C 0.07%-0.09%, Si 0.05%-0.20%, Mn 1.35%-1.55%, Als 0.015%-0.060%, Nb 0.040%-0.060%, Ti 0.020%-0.035%, P≤0.017%, S≤0.004%, N≤0.0050%, O≤0.0030%, and the balance is Fe and unavoidable inclusions.

2. The 600MPa grade hot-rolled automobile wheel steel according to claim 1, characterized in that: The yield strength of the steel is ≥540MPa, the tensile strength is ≥600MPa, and the elongation is ≥25%.

3. The 600MPa grade hot-rolled automobile wheel steel according to claim 1, characterized in that: The metallographic structure of the steel is ferrite+pearlite.

4. A method for preparing the 600MPa grade hot-rolled automobile wheel steel according to any one of claims 1 to 3, characterized in that: The production process of the steel includes: smelting - continuous casting - heating - hot rolling - controlled cooling - coiling; wherein: (1) Smelting: The S of molten iron is controlled at 0.005% or less, the thickness of slag is 20 mm or less, aluminum iron is used for deoxidation, medium manganese and low carbon and low phosphorus ferromanganese are used for alloying, and calcium treatment is performed in the refining process; (2) Continuous casting: ensure low superheat in the tundish, superheat ≤ 25°C, control Als to 0.02%-0.04%, and use constant casting speed control during the continuous casting process; (3) Heating: The heating furnace is in the furnace for 2.5-4 hours, and the slab out of the furnace temperature is 1200-1270℃. The furnace atmosphere of the heating furnace is controlled to reduce the formation of iron oxide scale of the casting and ensure uniform heating temperature; (4) Hot rolling: Rough rolling R1 final rolling temperature 965-995°C, R2 final rolling temperature 1055-1085°C, finishing rolling start temperature 1015-1045°C, final rolling temperature 845-875°C; (5) Controlled cooling and coiling: The coiling temperature is 565-595°C, and the controlled cooling adopts the front-stage continuous cooling method.

5. The preparation method according to claim 4, characterized in that: During the continuous casting process, the pulling speed is 0.9-1.45m / min, and the casting is put in with light pressure.

6. The preparation method according to claim 4, characterized in that: The number of R1 rough rolling passes is 3 times, the number of R2 rough rolling passes is 5 times, the total rough rolling reduction rate is 82.6-84.3%, and the thickness of the intermediate billet after rough rolling is 36-40 mm.

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