Method for manufacturing thick hot-rolled dual-phase steel based on CSP (Compact Strip Production) process

Abstract

The invention discloses a method for manufacturing hot-rolled dual-phase steel based on a CSP (Compact Strip Production) process. The method comprises the following steps: (1) preparing a raw material comprising the following chemical compositions in percentage by weight: 0.055-0.070% of C, 0.40-0.50% of Si, 1.20-1.50% of Mn, less than or equal to 0.015% of P, less than or equal to 0.002% of S and the balance of Fe and unavoidable impurities; and (2) sequentially pretreating molten steel, carrying out converter top and bottom combined blowing, refining in an LF, continuously casting thin billet, soaking in a tunnel furnace, continuously rolling by virtue of an F1-F7 seven-stand hot continuous rolling mill group, cooling by virtue of a laminar cooling system, cooling by virtue of an ultra-fast cooling system and coiling. In the method, the out-of-furnace temperature of the continuous casting billet passing through the tunnel soaking furnace is equal to or greater than 1130 DEG C, the initial rolling temperature in the hot continuous rolling step is equal to or greater than 1010 DEG C, the reduction rate in an F1 stand is equal to or greater than 40%, the reduction rate in an F2 stand is equal to or greater than 33.3%, the temperature after the laminar cooling and air cooling is 600-690 DEG C, the temperature after ultra-fast cooling is 150-250 DEG C, the ultra-fast cooling speed is 70-150 DEG C/s. The microstructures of 11.0mm-thickness 590MPa-grade dual-phase steel in the thickness direction, which is produced from a simple low C-Mn-component system in an industrial mass manner, are ferrite and martensite duplex microstructures so that the dual-phase steel is excellent in comprehensive performance.

Description

Technical field [0001] The invention relates to a production process of a hot-rolled steel sheet, in particular to a method for manufacturing a 590MPa-class hot-rolled dual-phase steel with low-cost thickness specifications based on the CSP process. Background technique [0002] Hot-rolled dual-phase steel is mainly an advanced high-strength steel with a certain proportion of martensite dual-phase structure distributed on a ferrite matrix obtained from low-carbon steel or low-carbon alloy steel through controlled rolling and controlled cooling processes. Comprehensive mechanical properties, it is a widely used steel plate for automobiles. The 590MPa grade hot-rolled dual-phase steel with a thickness of 10.0~14.0mm is mainly used to manufacture truck wheels and beams, and the demand is huge. [0003] Compared with conventional hot rolling production lines, the production process of CSP (Compact Strip Production, also known as compact hot strip production process) production line is...

AI Technical Summary

Problems solved by technology

Therefore, under the conditions of the existing CSP process, limited by cooling equipment and process technology, it is difficult to achieve a stable matching of chemical composition-process window-microstructure properties for thick-gauge high-strength hot-rolled dual-phase steel, and it is impossible to realize this type of dual-phase steel. Industrial production and application of phase steel

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