980 MPa-grade high-formability cold-rolled DH steel and preparation method thereof

Abstract

The invention discloses 980 MPa-grade high-formability cold-rolled DH steel and a preparation method thereof. The steel comprises 0.16 %-0.23 % of C, 1.8 %-2.8 % of Mn, 0.3 %-1.5 % of Si, 0.02 %-1.2 %of Al, 0.02 %-0.50 % of Mo, 0.02 %-0.70 % of Cr, less than or equal to 0.01 % of P, less than or equal to 0.01 % of S, less than or equal to 0.05 % of Nb, less than or equal to 0.04 % of Ti and the balance iron and inevitable impurities. The heating temperature of a continuous casting blank is 1150-1300 DEG C, the initial rolling temperature is 1000-1150 DEG C, the final rolling temperature is greater than or equal to 880 DEG C, and the coiling temperature is 500-700 DEG C; the cold rolling reduction rate is 40 %-80 %; the annealing temperature is 760-880 DEG C, the annealing time is 10-600 s, the slow cooling outlet temperature is 660-760 DEG C, the rapid cooling rate is larger than 20 DEG C/s, the overaging temperature is 350-450 DEG C, and the overaging time is 30-3600 s; and the finishing elongation rate is 0.3 %-0.7 %. According to the steel and the method, the tensile strength of a steel sheet is 980-1100 MPa, the A <80> is 16 %-20 %, and the reaming performance is excellent.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled steel, and relates to a DH980 cold-rolled automobile steel plate with high formability and a preparation method thereof. Background technique [0002] In the automotive industry, higher requirements have been put forward for body weight reduction, emission restrictions, and safety standards. In order to better serve users, the automotive industry has more and more demands for parts with high formability. Traditional dual-phase steels are difficult to meet the requirements of high-drawability complex punching cups, and TRIP steels are widely used due to high alloy content and expensive production costs. DH steel is the English abbreviation of Dual Phase Steels with Improved Formability, which was first mentioned in the VDA 239-100 cold-formed steel plate standard issued by the German Association of Automobile Manufacturers in 2016. DH steel has good formability due to the introduction of a cer...

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Problems solved by technology

[0003] Patent document CN 106119716 A discloses a 1000MPa grade cold-rolled hot-dip galvanized dual-phase steel with enhanced plasticity and its manufacturing method. Its main chemical components are: C: 0.15-0.23%, Si: 0.1-0.5%, Mn: 1.8-2.3%, P: ≤0.01%, S: ≤0.01%, Al: 0.5-1.0%, Cr: 0.3-0.6%, Ti: 0.01-0.04%, the balance is Fe and unavoidable impurities, the patent produces The process mainly adopts hot-dip galvanizing process, the product has poor plasticity and insufficient formability

[0004] Patent document CN 109554616 A discloses a 700MPa hot-rolled TRIP-assisted dual-phase steel and its preparation method. Its main chemical components are: C: 0.14%-0.16%, Si: 0.42%-0.65%, Mn: 1.6% ~1.7%, Al: 0.5%~0.8%, P≤0.014%, S≤0.003%, the production process mainly adopts hot rolling, the strength level is 700MPa, the strength level of this patented product is far from meeting the performance requirements of DH980

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