Low-yield-ratio hot-rolled steel sheet excellent in hole expansion performance for automobiles and manufacturing method thereof

Abstract

The invention discloses an automobile hot rolled steel plate with the good broaching performance and the low yield ratio and a manufacturing method thereof. Steel comprises 0.03%-0.06% of C, 0.80%-1.50% of Si, 1.0%-2.0% of Mn, 0.02%-0.06% of Als, 0.50%-0.80% of Mo, 0.03%-0.06% of Nb, 0.02%-0.05% of V, less than or equal to 0.010% of P, less than or equal to 0.003% of S, and the balance iron and inevitable impurities. The manufacturing method comprises the steps of heating a plate blank to 1220-1250 DEG C and then conducting heat preservation for 1-2 h; keeping the total reduction rate of a non-recrystallization region greater than 90% and the finished rolling temperature at 750-800 DEG C; cooling a steel plate to 620-650 DEG C at the laminar cooling rate of 10-15 DEG C / s in the laminar cooling and rapid cooling mode after finished rolling, conducting rapid cooling at the cooling rate greater than 50 DEG C / s to 500-550 DEG C and then reeling the steel plate. The finished steel plate hashigh strength and good yield ratio and hoe expansion rate for matching and is suitable for an automobile chassis, a seat or other parts.

Description

technical field [0001] The invention belongs to the technical field of steel rolling, and in particular relates to a hot-rolled steel plate suitable for producing automobile chassis, seats and other components and a manufacturing method thereof. Background technique [0002] In recent years, with the rapid development of the automobile industry, the development trend of automobile lightweight is obvious, and the research and development and application of high-strength steel for automobiles are becoming more and more extensive. However, while the strength of steel materials for automobiles has increased, higher requirements have been put forward for their cold forming properties, especially when the tensile strength of the material reaches 800 MPa and above, problems such as cracking and springback are prone to occur during the stamping process . For automobile chassis and seat parts, under the premise of the same tensile strength, low yield ratio and good hole expansion pe...

AI Technical Summary

Problems solved by technology

For automobile chassis and seat parts, under the premise of the same tensile strength, low yield ratio and good hole expansion performance are more conducive to stamping and dimensional accuracy control of parts. Materials such as hot-rolled dual-phase steel with low yield ratio and high-hole-expanding steel with good hole-expanding performance cannot meet the forming requirements well. Therefore, it is of great importance to develop high-strength hot-rolled steel plates with low yield-ratio Significance, has a good market application prospect

[0003] The patent with the publication number CN101078089A mentioned a hot-rolled high-strength steel plate with a tensile strength higher than 980 MPa and good hole expansion performance. The chemical composition of the steel plate is 0.03% to 0.10% C, 0.2% to 2.0% Si, 0.5% ~2.5% Mn, 0.02%~0.10% Al, 0.2%~1.5% Cr, 0.1%~0.5% Mo, the rest is Fe and unavoidable impurities. The martensite content in the product structure is higher than 80%, and the tensile strength is The strength is higher than 980MPa, and the hole expansion rate is relatively good, but the yield ratio of the steel plate is higher than 0.75, and the elongation is relatively low. The coiling temperature of the steel plate is required to be lower than 400°C, which is not conducive to the production of products and cold stamping.

[0004] Patent US2006096678 proposes a 780MPa grade hot-rolled high-hole expansion steel, which contains 0.04%-0.15% C, 0-1.5% Si, 0.5%-1.6% Mn, 0.03%-0.5% Mo, 0.03% ~0.15Ti, after the final rolling of the steel plate, the staged cooling process is adopted, the coiling temperature is 350-500 ℃, the microstructure of the steel plate is composed of ferrite and bainite, the tensile strength is higher than 780MPa, and the hole expansion rate is ≥60% , the disadvantage is that the yield ratio is higher than 0.80, which is not conducive to the cold stamping of the product

[0005] Patent No. CN101880825A discloses ultra-fine-grained hot-rolled dual-phase steel with a tensile strength above 750 MPa and its manufacturing method, CN1566389A discloses ultra-fine-grained low-carbon low-alloy dual-phase steel and its manufacturing method, and the high-strength steel proposed in the above-mentioned patents The structure of the steel plate is composed of ferrite and martensite, the yield strength is relatively low, but the hole expansion performance is not good;

[0006] Patent No. CN101928881A discloses a tensile strength of 590MPa grade hot-rolled high-hole expansion steel plate and its manufacturing process, and CN101353757A discloses a tensile strength of 440MPa grade hot-rolled high-hole expansion steel plate and its manufacturing method. The steel plate proposed in the above-mentioned patent has good Excellent hole expansion performance, but the strength of the steel plate is low, the yield ratio is above 0.82, the stamping is difficult, and it is easy to have a large springback during the stamping process, which affects the dimensional accuracy of the parts

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