800 MPa grade cold-rolled double-phase steel and production method thereof

Abstract

The invention discloses 800 MPa grade cold-rolled double-phase steel and a production method thereof. The production method comprises a hot rolling process and a cold rolling continuous annealing process. The chemical compositions of a casting entering the hot rolling process comprise, in percent by mass, 0.14-0.17% of C, 0.45-0.55 of Si, 1.6-1.8 of Mn, 0.55-0.65% of Cr, P<=0.016%, S<=0.008%, 0.02-0.05% of Als, N<=0.004%, and the balance Fe. In the double-phase steel, the Si content is increased and the Mn content is reduced on the basis of the compositions of C-Si-Mn-Cr, so that the strength is increased without adding Al, Nb, Mo, Ti and other high-cost elements, and the purposes of reducing production difficulty and production cost while not influencing smelting castability are realized. The method improves the Si content, reduces the Mn content, improves the composition system of the C-Si-Mn-Cr system and realizes the purpose of reducing production cost. By improving the smelting, hot rolling and cold-rolling continuous annealing technologies, the cold-rolled double-phase steel with the tensile strength of 800-850 MPa, the yield strength of 450-550 MPa and the elongation percentage of 15-17% is produced, and the production method has the characteristics of simple technology, low cost and stable product quality.

Description

technical field [0001] The invention belongs to the technical field of metallurgical plate production, in particular to an 800MPa grade cold-rolled dual-phase steel and a production method thereof. Background technique [0002] At present, the composition systems of cold-rolled dual-phase steel are mainly C-Si-Mn-Cr series, C-Si-Mn-Cr-Mo, C-Si-Mn-Nb and C-Al-Mn-Mo series, etc. . The difficulty in producing cold-rolled dual-phase steel lies in the need to control a high cooling rate and a low final cooling temperature during annealing, so that there are two phases of ferrite and martensite in the cold-rolled finished product. When the cooling rate is slow or the final cooling temperature is high, the volume fraction of martensite formed is insufficient, or even martensite cannot be formed, resulting in low tensile strength of the finished product and affecting product quality. However, the high cooling rate and low final cooling temperature require higher equipment. Theref...

AI Technical Summary

Problems solved by technology

Nb can stabilize and enhance the stability of austenite and refine grains, but for cold-rolled dual-phase steel, the effect is not obvious

Al has a significant effect on improving the stability of austenite, but the current Al content in the existing technology is too high (about 1.0 to 2.0%), resulting in a significant decrease in smelting castability, which is not conducive to continuous production

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