500MPa-grade cold rolling dual-phase steel and production method thereof

Abstract

The invention discloses a 500MPa-grade cold rolling dual-phase steel and a production method thereof. The method comprises the working procedures of hot rolling and cold rolling continuous annealing; the dual-phase steel comprises the following chemical components by mass percent: 0.06-0.09% of C, 0.32-0.39% of Si, 1.40-1.49% of Mn, less than or equal to 0.015% of P, less than or equal to 0.01% of S, 0.020-0.050% of Als, less than or equal to 0.007% of N, 0.0005-0.0015% of B and the balance of Fe. According to the 500MPa-grade cold rolling dual-phase steel, on the basis of the components of C-Si-Mn dual-phase steel, the content of the Si is reduced, the content of Al is properly increased, and the stability of austenite is improved by the Si and the Al; furthermore, the B element is fed into the steel, and the content of the N is reasonably controlled, so that AlN particles are generated by part of acid-soluble aluminum (Als) in the steel, BN is produced by part of B in the steel, and elution is enhanced; and therefore, the production difficulty is reduced, the smelting castability is not influenced, the cost is low, the production continuity is better, and the product quality is stable. According to the method, the alloy element is not fed into the steel, so that the components of the C-Si-Mn serial dual-phase steel can be improved; the cold rolling dual-phase steel with low yield ratio and high elongation can be produced by steelmaking improvement, the hot rolling process and the cold rolling continuous annealing process.

Description

technical field [0001] The invention belongs to the technical field of metallurgical plate production, in particular to a 500MPa grade cold-rolled dual-phase steel and a production method thereof. Background technique [0002] At present, the composition systems for producing 500MPa grade cold-rolled dual-phase steel are mainly C-Si-Mn series, C-Si-Mn-Cr series, C-Si-Mn-Cr-Mo, C-Si-Mn-Nb and C -Al-Mn 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 temperatur...

AI Technical Summary

Problems solved by technology

Nb can stabilize and enhance the stability of austenite and refine grains, but the effect is not obvious

Al has a significant effect on improving the stability of austenite, but the Al content is too high (about 1.0%), resulting in a significant decrease in smelting castability, which is not conducive to continuous production; reducing the Al content will lead to a decrease in austenite stability and increase production control difficulty

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