Low-yield-ratio and high-strength steel plate having 690-MPa-level yield strength and manufacturing method thereof

Abstract

The invention relates to a low-yield-ratio and high-strength steel plate having 690-MPa-level yield strength. The steel plate is prepared from chemical components including 0.10%-0.20% of C, 0.10%-0.40% of Si, 0.90%-1.40% of Mn, less than or equal to 0.030% of Nb, less than or equal to 0.010% of V, less than or equal to 0.025% of Ti, 0.02%-0.06% of Al, less than or equal to 0.10% of Ni, less thanor equal to 0.10% of Cu, 0.10%-0.80% of Cr, 0.10%-0.70% of Mo, 0.001%-0.005% of B, 0.001%-0.005% of Ca, less than or equal to 0.015% of P, less than or equal to 0.003% of S, less than or equal to 0.002% of O, less than or equal to 0.004% of N, less than or equal to 0.0002% of H and the balance Fe. The steel plate adopts the tempered sorbite and bainite duplex structure. The yield strength Rp0.2 ishigher than or equal to 690 MPa, the tensile strength Rm is higher than or equal to 770 MPa, the yield ratio Rp0.2 / Rm is lower than or equal to 0.88, the ductility A is higher than or equal to 16%, and the low-temperature impact Akv at subzero 40 DEG C is higher than or equal to 100 J. The manufacturing process includes steel making by the aid of a converter or an electric furnace, LF refinement,VD or RH vacuum degassing, Ca treatment, continuous casting, heating, rolling, primary quenching, secondary quenching and tempering.

Description

technical field [0001] The invention relates to a steelmaking method for iron-based steel, in particular to a method for manufacturing a low-yield-ratio, high-strength steel plate. Background technique [0002] The rapid development of the steel structure industry, building bridges, engineering machinery, mining machinery and other industries will initially increase the demand for high-strength steel plates with a yield strength of 690MPa. The traditional high-strength steel plate with a yield strength of 690MPa is generally produced by quenching + high-temperature tempering. While improving the strength, the toughness can also meet the requirements and meet the use requirements. However, the high-strength steel produced in this way has a high yield ratio, generally above 0.90, and a high yield ratio has a certain impact on the safety of bridges, construction projects and other industries. In recent years, reducing the yield ratio of quenched and tempered high-strength stee...

AI Technical Summary

Problems solved by technology

Such a high Mn content has brought great difficulties to steelmaking and continuous casting, and there is a risk of a large amount of MnS band-like precipitation due to high Mn content, and there are also problems with uniformity of properties and cutting deformation when the TMCP process is used for production

[0005] In summary, the current production technologies involving high-strength steel plates with a yield strength of 690MPa mainly include quenching + tempering or online TMCP; the traditional quenching + tempering process has a yield ratio > 0.90; the TMCP process uses low carbon (C < 0.10 %) High alloy design, low yield ratio, but high alloy cost, poor overall performance uniformity, and large residual stress

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