780 MPa-grade alloying hot galvanizing DH steel and preparation method thereof

Abstract

The invention discloses 780 MPa-grade alloying hot galvanizing DH steel and a preparation method thereof. The steel comprises 0.11-0.17% of C, 1.4-2.4% of Mn, 0.15-0.60% of Si, 0.02-1.0% of Al, 0.20-0.70% of Mo, 0-0.03% of P, 0-0.03% of S, 0-0.005% of B, 0-0.05% of V, 0-0.05% of Ti and the balance iron and inevitable impurities. The heating temperature of casting blank is 1170-1280 DEG C, the rolling temperature is 1020-1140 DEG C, the final rolling temperature is higher than or equal to 910 DEG C, the coiling temperature is 550-700 DEG C, the cold rolling reduction ratio is 40-80%, the annealing temperature is 770-870 DEG C, the annealing time is 30-300 seconds, the galvanizing temperature is 450-470 DEG C, the alloying temperature is 470-530 DEG C, the heat preservation time is 5-60 seconds, A50 of a steel plate finished product is 20-25%, the hole expansion rate is larger than or equal to 25%, and the requirements of automobile steel for high formability and high hole expansion performance are met.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled steel, and relates to an alloyed hot-dip galvanized DH780 automobile steel with excellent cold-bending performance 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 ...

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Problems solved by technology

[0003] Patent document CN 106119716 A discloses a plastically enhanced cold-rolled hot-dip galvanized dual-phase steel and its production method. Its main chemical components are: C: 0.12%-0.18%, Si: 0.3%-0.6%, Mn: 1.3 %~2.3%, Al: 0.4%~0.9%, P≤0.01%, S≤0.01%, the production process mainly adopts cold-rolled hot-dip galvanizing treatment, the patented product has poor plasticity, and does not involve alloyed hot-dip galvanized products

[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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