A kind of 780MPa grade high ductility cold-rolled DH steel and its preparation method

Abstract

The invention discloses a 780MPa high-plasticity cold-rolled DH steel and a preparation method thereof. Steel contains C: 0.10%~0.18%, Mn: 1.5%~2.5%, Si: 0.4%~0.8%, Al: 0.02%~0.7%, Cr: 0.02%~0.50%, P≤0.01%, S≤ 0.01%, Nb≤0.1%, Ti≤0.1%, and Si+Al: 0.5%~1.5%, the balance is iron and unavoidable impurities. The starting rolling temperature is 1050~1150℃, the final rolling temperature is ≥900℃, the coiling temperature is 550~700℃; the cold rolling reduction rate is 40%~80%; the continuous annealing preheating temperature is 200~600℃, and the annealing temperature is 760~880℃ , annealing time 10-600s, slow cooling outlet temperature 660-760°C, rapid cooling rate>20°C / s, overaging temperature 300-420°C, overaging time 30-3600s; skin elongation 0.3%-0.7%. For parts in the automotive industry that require high formability.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled steel, and relates to DH780 cold-rolled automobile steel with high ductility and 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 introducti...

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Problems solved by technology

[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 patent strength level fails to meet the performance requirements of DH780, and it is a hot-rolled product

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