A low-density, high-strength, high-wear-resistant steel and a heat treatment preparation method thereof

Abstract

The present invention discloses a low-density, high-strength, high-wear-resistant steel and a heat treatment preparation method thereof, belonging to the technical field of metal materials. The above-mentioned low-density, high-strength, high-wear-resistant steel comprises the following components in weight percentage: 0.35-0.4% C, 6-7% Mn, 5.5-6% Al, 1.2-1.3% Si, 0.3-0.4% V, 0.03-0.035% Nb and 0.002-0.003% B, and the remainder is Fe and unavoidable impurities. The present invention provides a steel material having high strength, high wear resistance and low density and a preparation method thereof. The structural characteristics of the steel material are martensite and a small amount of austenite. The density of the steel material prepared by the present invention is 7.0-7.2g / cm 3 The tensile strength reaches more than 2000MPa, the yield strength reaches more than 1200MPa, the Vickers hardness reaches more than 470HV, and it also has high wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials, and in particular to a low-density, high-strength and high-wear-resistant steel and a heat treatment preparation method thereof. Background Art

[0002] Fe-Mn-Al-C alloy steel is a new type of low-density high-strength steel. Studies have shown that for every 1% Al added by mass, the density can be reduced by about 1.3%, and it is expected to become the preferred material for lightweight advanced high-strength steel in the future. However, Fe-Mn-Al-C low-density steel has a high alloy content and complex phase composition. Directly increasing the proportion of Al components will lead to an excessively high volume fraction of ferrite, which is not conducive to improving the comprehensive performance of low-density steel. Further research is needed on its chemical composition and production process to obtain lightweight, high-performance, and wear-resistant metal materials with excellent service life.

[0003] Therefore, how to obtain Fe-Mn-Al-C low-density steel with both light weight and excellent wear resistance through alloy composition design and heat treatment process, and provide new ideas for solving the weight and service life problems of high-performance and high-wear-resistant metal materials, is a technical problem that technical personnel in this field currently need to solve. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a low-density, high-strength and high-wear-resistant steel and a heat treatment preparation method thereof, so as to solve the problem that the existing Fe-Mn-Al-C low-density steel is difficult to have both lightweight and excellent wear resistance.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A low-density, high-strength and high-wear-resistant steel, characterized by comprising the following components in percentage by weight:

[0007] 0.35-0.4% C, 6-7% Mn, 5.5-6% Al, 1.2-1.3% Si, 0.3-0.4% V, 0.03-0.035% Nb and 0.002-0.003% B, the balance being Fe and unavoidable impurities.

[0008] The beneficial effects of the present invention are:

[0009] C: The addition of C to low-density high-strength steel can expand the austenite phase and improve the stability of austenite, which has a significant solid solution strengthening effect. As the carbon content increases, the austenite content and stability also increase accordingly, causing the steel to produce stress-induced martensitic transformation (TRIP effect) during deformation, thereby improving its strength and plasticity. In addition, C can reduce the martensite start transformation temperature (M sHowever, too high a carbon content will seriously affect the welding performance of the steel, and element segregation and carbide precipitation are likely to occur during casting and processing.

[0010] Mn: Mn is an austenite stabilizing element that can expand the austenite phase region and reduce the martensite transformation temperature (M s point), increasing the content of retained austenite at room temperature. Mn element has the effect of grain refinement and solid solution strengthening. However, too high Mn content will make austenite too stable to produce TRIP effect, and may produce β-Mn brittle phase, which will affect the comprehensive performance of low-density steel.

[0011] Al: Al is one of the important elements of Fe-Mn-Al-C low-density steel. It can reduce the average molar mass of steel and cause lattice expansion, thereby achieving the purpose of reducing material density. For every 1% Al added by mass, the density can be reduced by about 1.3%. In addition, Al is a ferrite-forming element that can reduce the γ phase region, expand the α phase region, and increase the ferrite content in steel. Al has a significant solid solution strengthening effect on ferrite, thereby effectively improving the strength of steel. However, too high an Al content will lead to an excessively high volume fraction of ferrite, which is not conducive to improving the comprehensive performance of low-density steel.

[0012] Si: Si is a ferrite-forming element and can play a role in solid solution strengthening in ferrite. However, the solubility of Si in carbides is very low, which is not conducive to the nucleation and precipitation of carbides during heat treatment, so the content of Si needs to be controlled.

[0013] V, Nb: Both V and Nb elements can promote the precipitation of second phase particles, forming VC and NbC carbide strengthening phases, pinning dislocations, thereby improving matrix strength and strain hardening ability, and at the same time can effectively hinder grain growth to achieve the purpose of grain refinement.

[0014] B: In addition to effectively improving the hardenability of Fe-Mn-Al-C low-density steel, the B element can also prevent the segregation of the Mn element at the grain boundaries.

[0015] The present invention adjusts the ratio between the components and the Al element to reduce the material density, combines with the Si element to strengthen the ferrite by solid solution, and effectively improves the strength of the steel. The steel grains are refined by elements such as Mn, V, and Nb to improve the body strength and strain hardening ability. The hardenability of the steel is improved by the B element to prevent the segregation of the Mn element at the grain boundary, thereby obtaining a steel with high strength, low wear rate and low density.

[0016] Further, the following components are included in weight percentage:

[0017] 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.009% B, with the balance being Fe and inevitable impurities.

[0018] The method for preparing the above-mentioned low-density, high-strength and high-wear-resistant steel comprises the following steps:

[0019] The raw materials are first smelted and forged according to weight components, then hot-rolled to obtain steel sheets, and finally heat-treated to obtain the steel.

[0020] Further, the starting temperature of hot rolling is 1100-1300°C.

[0021] Furthermore, the hot rolling started at a temperature of 1200° C., followed by air cooling to room temperature.

[0022] Furthermore, the heat treatment method is: heating the steel under the protection of a rare gas for tempering, and then air cooling to room temperature.

[0023] Furthermore, the tempering temperature is 150-250°C, the holding time is 1-3h, and the heating rate is 10-30°C / min.

[0024] Furthermore, the tempering temperature is 150°C, 200°C or 250°C, the holding time is 2h, and the heating rate is 20°C / min.

[0025] Furthermore, the air cooling rate is 10-30°C / s.

[0026] Furthermore, the air cooling rate is 20°C / s.

[0027] The present invention has the following beneficial effects:

[0028] The present invention provides a steel material having high strength, high wear resistance and low density and a preparation method thereof. The structural characteristics of the steel material are martensite and a small amount of austenite (~5% volume fraction). Experiments have shown that the density of the steel material prepared by the present invention is 7.0-7.2 g / cm 3 The tensile strength reaches more than 2000MPa, the yield strength reaches more than 1200MPa, the Vickers hardness reaches more than 470HV, and the 10N wear rate is 0.25×10 6 μm 3 / mm or less, 30N-wear rate is 4.7×10 6 μm 3 / mm or less, it has better wear resistance and better mechanical properties compared with ZGMn8CrMo wear-resistant medium manganese cast steel and commonly used martensitic wear-resistant steel (NM400). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a process flow chart of the preparation method of Example 2;

[0030] Figure 2 The microstructure diagram of the low-density, high-strength and high-wear-resistant steel obtained in Example 1;

[0031] Figure 3 The microstructure diagram of the low-density, high-strength and high-wear-resistant steel obtained in Example 2;

[0032] Figure 4 The microstructure diagram of the low-density, high-strength and high-wear-resistant steel obtained in Example 3;

[0033] Figure 5 The microstructure diagram of the low-density, high-strength and high-wear-resistant steel obtained in Example 4;

[0034] Figure 6 It is a schematic diagram comparing the wear amounts of Examples 1-4, Comparative Example 1 and commercial NM400. DETAILED DESCRIPTION

[0035] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0036] Embodiment 1:

[0037] A low-density, high-strength and high-wear-resistant steel comprising the following components in percentage by weight:

[0038] 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.0029% B, the balance being Fe and inevitable impurities.

[0039] The method for preparing the above-mentioned low-density, high-strength and high-wear-resistant steel comprises the following steps:

[0040] The raw materials are smelted and forged according to the weight composition ratio, and then the blanks are rolled into 3 mm thin plates by hot rolling, and the initial rolling temperature is 1200°C.

[0041] Embodiment 2:

[0042] A low-density, high-strength and high-wear-resistant steel comprising the following components in weight percentage:

[0043] 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.0029% B, the balance being Fe and inevitable impurities.

[0044] The preparation method of the above-mentioned low-density, high-strength and high-wear-resistant steel (process flow chart as shown in Figure 1 As shown), comprising the following steps:

[0045] (1) Rolling

[0046] The raw materials are smelted and forged according to the weight composition ratio, and then the blanks are rolled into 3 mm thin plates by hot rolling, and the initial rolling temperature is 1200°C.

[0047] (2) Tempering

[0048] The steel was heated to 150°C and kept at this temperature for 2 h. At the same time, the environment was evacuated and argon was introduced, with the vacuum degree being 100 Pa. The steel was then air-cooled to room temperature at a cooling rate of 20°C / s.

[0049] Embodiment 3:

[0050] A low-density, high-strength and high-wear-resistant steel comprising the following components in weight percentage:

[0051] 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.0029% B, the balance being Fe and inevitable impurities.

[0052] The method for preparing the above-mentioned low-density, high-strength and high-wear-resistant steel comprises the following steps:

[0053] (1) Rolling

[0054] The raw materials are smelted and forged according to the weight composition ratio, and then the blanks are rolled into 3 mm thin plates by hot rolling, and the initial rolling temperature is 1200°C.

[0055] (2) Tempering

[0056] The steel was heated to 200°C and kept at this temperature for 2h. At the same time, the environment was evacuated and argon was introduced, with the vacuum degree being 100Pa. The steel was then air-cooled to room temperature at a cooling rate of 20°C / s.

[0057] Embodiment 4:

[0058] A low-density, high-strength and high-wear-resistant steel comprising the following components in weight percentage:

[0059] 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.0029% B, the balance being Fe and inevitable impurities.

[0060] The method for preparing the above-mentioned low-density, high-strength and high-wear-resistant steel comprises the following steps:

[0061] (1) Rolling

[0062] The raw materials are smelted and forged according to the weight composition ratio, and then the blanks are rolled into 3 mm thin plates by hot rolling, and the initial rolling temperature is 1200°C.

[0063] (2) Tempering

[0064] The steel was heated to 250°C and kept at this temperature for 2 h. At the same time, the environment was evacuated and argon was introduced, with a vacuum degree of 100 Pa. The steel was then air-cooled to room temperature at a cooling rate of 20°C / s.

[0065] Comparative Example 1:

[0066] A ZGMn8CrMo wear-resistant medium manganese cast steel comprises the following components in percentage by weight:

[0067] 0.969% C, 8.298% Mn, 1.27% Cr, 0.877% Mo, 0.52% Si, 0.0022% P and 0.006% S, with the balance being Fe and inevitable impurities.

[0068] The preparation method of the above-mentioned ZGMn8CrMo wear-resistant medium manganese cast steel comprises the following steps:

[0069] The raw materials are smelted and forged according to the weight composition ratio, and then water-toughened, that is, heated to 1200°C for 2 hours, and then water-cooled to room temperature.

[0070] Test example:

[0071] The density of the sample is measured according to the Archimedean principle.

[0072] The microstructure of the samples was observed by scanning electron microscopy.

[0073] The sliding wear test was carried out by a self-designed high-precision tangential sliding reciprocating friction and wear tester. Si3N4 ceramic balls with a diameter of 3mm and a hardness of 1500Hv were selected as the grinding pair. The sample size in the sliding wear test was 15mm×10mm×2.5mm, and the sample surface was ground and polished according to the standard metallographic preparation method. The sliding wear tests were carried out at room temperature and atmospheric conditions, with a displacement amplitude of 2500μm, normal loads of 10N and 30N respectively, an experimental frequency of 2Hz, and a cycle of 1×10 4, relative humidity 50% to 60%. The direction of the sliding wear test is perpendicular to the rolling direction of the sample. All working conditions are repeated three times to ensure the repeatability of the experiment and the accuracy of the data, and the average value of the three experiments is taken as the experimental result. The wear volume and two-dimensional profile of the wear scar of the sample after the wear test are collected using a Bruker white light interferometer 3D profiler (GTK-16-0295). In order to avoid the influence of the contact geometry effect of the grinding pair on the two ends of the wear scar during the wear test, the 4mm long area in the center of the wear scar is used to calculate the wear volume, and the wear rate (wear volume per unit length) is used as the wear resistance evaluation index.

[0074] The surface microhardness of the sample was measured by a micro Vickers hardness tester (DHV-1000ZTEST), with a load of 200 gN and a holding time of 15 s. The average value of 10 points for each sample was taken as the experimental result. The tensile specimens were prepared according to the ASTM (E-8) tensile test standard, with a gauge section size of 25 mm × 6 mm × 1.8 mm, and a CMT5305 universal testing machine was used for the tensile test, with a tensile speed of 1.5 mm / min. To ensure the accuracy of the tensile data curve, an extensometer was used to measure the elongation of the gauge section. Each group of samples was subjected to three tensile tests, and the average value of the three sets of data results was taken as the value of each mechanical property.

[0075] The experimental results are as follows Figure 2-Figure 6 And as shown in Table 1.

[0076] Table 1 Performance test results of the products of the embodiments of the present invention and the comparative examples and commercial NM400

[0077]

[0078] according to Figure 2-Figure 5 It can be seen that the low-density, high-strength, high-wear-resistant steel obtained in Example 1 of the present invention without heat treatment has only martensite structure in its microstructure, and no austenite; while the low-density, high-strength, high-wear-resistant steel obtained after heat treatment (Examples 2-4) has austenite structure. Figure 6 As shown in Table 1, the tensile strength of the low-density, high-strength, high-wear-resistant steels prepared in the embodiments of the present invention is above 2000 MPa, the yield strength is above 1200 MPa, and the Vickers hardness is above 470 MPa, which are much higher than those of Comparative Example 1 and commercial NM400. In addition, according to the results of the sliding wear test, the low-density, high-strength, high-wear-resistant steel prepared in the present invention has significantly higher wear resistance than the comparative example and commercial NM400.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-density, high-strength and high-wear-resistant steel, characterized in that: The following components are included in weight percentage: 0.35-0.4% C, 6-7% Mn, 5.5-6% Al, 1.2-1.3% Si, 0.3-0.4% V, 0.03-0.035% Nb and 0.002-0.003% B, the balance being Fe and unavoidable impurities.

2. The low-density, high-strength, high-wear-resistant steel according to claim 1, characterized in that: The following components are included in weight percentage: 0.38% C, 6.74% Mn, 6% Al, 1.27% Si, 0.38% V, 0.034% Nb and 0.009% B, the balance being Fe and inevitable impurities.

3. The method for preparing the low-density, high-strength and high-wear-resistant steel according to claim 1 or 2, characterized in that: The following steps are involved: The raw materials are first smelted and forged according to weight components, then hot-rolled to obtain steel sheets, and finally heat-treated to obtain the steel.

4. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 3, characterized in that: The starting temperature of the hot rolling is 1100-1300°C.

5. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 4, characterized in that: The starting temperature of the hot rolling is 1200°C.

6. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 3, characterized in that: The heat treatment method is: heating the steel under the protection of rare gas for tempering, and then air cooling to room temperature.

7. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 6, characterized in that: The tempering temperature is 150-250° C., the holding time is 1-3 hours, and the heating rate is 10-30° C. / min.

8. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 7, characterized in that: The tempering temperature is 150° C., 200° C. or 250° C., the holding time is 2 hours, and the heating rate is 20° C. / min.

9. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 6, characterized in that: The air cooling rate is 10-30°C / s.

10. The method for preparing low-density, high-strength and high-wear-resistant steel according to claim 9, characterized in that: The air cooling rate is 20°C / s.

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