Tensile strength more than or equal to 780MPa grade hot-rolled dual phase steel and production method thereof

Abstract

The invention provides tensile strength more than or equal to 780MPa grade hot-rolled dual phase steel. The dual-phase steel comprises the following components in percentage by weight: 0.05-0.08 percent of C, not more than 0.5 percent of S, 0.6-1.2 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.006 percent of N, 0.01-0.1 percent of Als, 0.05-0.25 percent of Ti, less than or equal to 0.6 percent of Cr or less than or equal to 0.003 percent of B or mixture of Cr and B. The production method by using CSP comprises the following steps: melting and continuously casting to form a slab; heating the continuous cast slab; rolling; carrying out laminar cooling; reeling; and naturally cooling to room temperature. The hot-rolled dual phase steel has the tensile strength of more than or equal to 780MPa, elongation of more than or equal to 15 percent and yield ratio of less than or equal to 0.70. An insulation cover additionally covers the intermediate insulation section, and the band steel cooling speed is reduced, so that generation of pearlite phase change can be effectively prevented. Production of hot-rolled dual phase steel with thickness of 1.2-4.0mm can be realized, the product has the advantages of uniform structure, small molding resilience and no cracking, existing equipment is utilized without adopting ultra fast cooling and other equipment, the production efficiency is high, and the investment is small.

Description

technical field [0001] The invention relates to a dual-phase steel and a production method, in particular to a hot-rolled dual-phase steel with a tensile strength ≥ 780 MPa and a production method, and is particularly suitable for hot-rolled dual-phase steel with a thickness below 4.0 mm and a production method. Background technique [0002] In recent years, with the advancement of automobile energy-saving and emission-reduction technologies, automobile lightweight has become a development trend, and the demand for thin-gauge high-strength automobile steel is increasing. When used in the manufacture of automotive wheels, frames and other parts, ferrite + martensitic dual-phase steel is widely used due to its good strong plasticity, low yield ratio, high initial work hardening rate, and good bake hardenability. Application, F+M dual-phase steel is generally composed of 70%~90% ferrite and 10~30% martensite, and its production method is mainly divided into hot-rolled dual-phas...

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Problems solved by technology

[0007] The above-mentioned documents and the F+M hot-rolled dual-phase steel that have been produced have a strength level of no more than 750MPa, and have not yet involved the production method of 780MPa-level dual-phase steel

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