Alloyed hot-dip galvanized DH590 steel with high hole expansion performance and preparation method thereof

Abstract

The invention discloses 590MPa-grade alloying hot-dip galvanized DH steel with high hole expansion performance and a preparation method thereof. The steel comprises the following chemical components of, in percentage by mass, 0.09%-0.15% of C, 1.0%-2.0% of Mn, 0.1%-0.5% of Si, 0.02%-0.6% of Al, 0.02%-0.4% of Mo, less than or equal to 0.03% of P, less than or equal to 0.03% of S, less than or equalto 0.003% of B, less than or equal to 0.03% of Ti and the balance iron and inevitable impurities. According to the preparation method, the heating temperature of a casting blank ranges from 1200 DEGC to 1280 DEG C, the initial rolling temperature ranges from 1080 DEG C to 1160 DEG C, the final rolling temperature is greater than or equal to 930 DEG C, and the coiling temperature ranges from 600DEG C to 700 DEG C; the cold rolling reduction rate is 50%-85%; the annealing temperature ranges from 760 DEG C to 860 DEG C, the annealing time ranges from 30 seconds to 300 seconds, the slow coolingoutlet temperature ranges from 670 DEG C to 710 DEG C, the rapid cooling rate is larger than 20 DEG C/s, the galvanizing temperature ranges from 450 DEG C to 470 DEG C, the alloying temperature ranges from 480 DEG C to 530 DEG C, and the heat preservation time ranges from 5 seconds to 60 seconds; and the finishing elongation rate is 0.2%-0.6%. The elongation percentage after fracture of a finished steel plate A50 is 30%-35%, and the hole expanding rate is larger than or equal to 60%.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled steel, and relates to an alloyed hot-dip galvanized DH steel with excellent hole expansion performance for 590MPa grade automobiles. 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 introduct...

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Problems solved by technology

[0003] Patent document CN 109402355 A discloses a 600MPa grade hot-rolled TRIP type dual-phase steel and its preparation method. Its main chemical components are: C: 0.12%-0.14%, Si: 0.3%-0.4%, Mn: 1.5%- 1.7%, Al: 0.35%~0.45%, P≤0.014%, the production process mainly adopts hot rolling process, the plasticity of this patented product is poor, A 50 The elongation after breaking is only 24%, which does not involve alloyed hot-dip galvanized products and hole expansion performance

[0004] Patent document CN 103827332 B discloses a TRIP-type martensitic dual-phase steel and an ultra-high-strength steel workpiece using it. Its main chemical components are: C: 0.1%-0.7%, Si: 0.5%-2.5% , Mn: 0.5%~3.0%, Cr: 0.5%~2.0%, Mo≤0.5%, Al: 0.04%~2.5%, the production process mainly adopts cold rolling and continuous annealing process, the strength level is 1500MPa, the formability is poor, it is difficult to Meet the needs of deep drawing forming

[0005] Patent document CN 107747039 A discloses a cold-rolled dual-phase steel with high hole expansion performance and its preparation method. Its main chemical components are: C: 0.10%-0.50%, Si: 0.1%-0.5%, Mn: 1.60%- 2.00%, V: 0.01% ~ 0.03%, Al: 0.02% ~ 0.06%, P≤0.020%, S≤0.015%, N≤0.006%, the production process is cold rolling and continuous annealing system, not involving alloying hot-dip galvanizing product.

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