780MPa-grade cold-rolled light-weight high-strength steel and preparation method thereof

Abstract

The invention discloses 780MPa-grade cold-rolled light high-strength steel and a preparation method thereof. The steel comprises 0.13%-0.23% of C, 0.9%-1.6% of Si, 1.2%-2.2% of Mn, 0.03%-0.05% of P, less than or equal to 0.03% of S, 3.2%-4.8% of Al, 0.1%-0.5% of Cr, 0.001%-0.005% of B, and the balance Fe and inevitable impurities, wherein the (12C+1.1Mn) / (Al+0.6 Si) is greater than or equal to 0.7 and less than or equal to 1.1. The casting blank heating temperature ranges from 1200 DEG C to 1250 DEG C, the initial rolling temperature ranges from 1000 DEG C to 1150 DEG C, the final rolling temperature ranges from 890 DEG C to 940 DEG C, and the coiling temperature ranges from 500 DEG C to 700 DEG C; the cold rolling reduction rate is 40%-80%; the quenching temperature is 800-880 DEG C, the heat preservation time is 60-240 s, the cooling rate is greater than 30 DEG C / s, and the quenching cooling temperature is 20-200 DEG C; and the continuous annealing temperature ranges from 800 DEG C to 880 DEG C, the annealing time ranges from 120 s to 300 s, the cooling rate ranges from 15 DEG C / s to 60 DEG C / s, and excellent strength and ductility are achieved.

Description

technical field [0001] The invention belongs to the field of steel manufacturing for automobiles, and relates to a cold-rolled light-weight high-strength steel and a preparation method thereof. The steel type is suitable for manufacturing automotive body structural parts, safety parts, anti-collision parts and other products. Background technique [0002] In recent years, with the continuous improvement of energy-saving and environmental protection requirements, lightweight and electrification have become the mainstream trend of the development of the automobile industry. The research, development and extensive use of high-strength and ultra-high-strength automotive steel have become an effective means to achieve lightweight automobiles. With the continuous increase in the strength of steel used in automobiles, it is becoming more and more difficult to reduce the weight of auto parts simply by increasing the strength of the steel plate. People try to use Al, Mg, carbon fiber...

AI Technical Summary

Problems solved by technology

Using the hot rolling process, high-strength and lightweight dual-phase steel with a strength level of 700-800MPa is produced, but the elongation of the product of this invention is low, and it is difficult to meet the stamping needs of auto parts

[0005] In summary, the existing lightweight high-strength automotive steel has problems such as high cost, complicated process, and poor product formability, which make it difficult to meet the needs of automotive parts.

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