Hot galvanizing baking chilled steel with yield strength 180Mpa and producing method thereof

Abstract

The invention relates to steel applied to automobiles, aiming at solving the deficiencies in the prior art that micro alloying elements are excessively added, the cost is high and the cost performance is low and other deficiencies. The measures are as follows: hot galvanizing bake-hardening steel with a yield strength of 180 Mpa is provided; the chemical components and the weight percentage of the chemical components are as follows: C: 0.001-0.008, Si: 0.045-0.055, Mn: 0.10-0.40, P: 0.01-0.03, Nb: 0.005-0.020, Ti: 0.0031-0.008, Als: 0.02-0.07, S: less than 0.015, N: 0.001-0.004, and the balance of Fe and unavoidable impurities; the preparation method has the following steps: rough rolling is carried out at the temperature of 1050-1100 DEG C, and finishing temperature of precision rolling is controlled within the range of 900-960 DEG C; rolling is carried out at the temperature of 700-760 DEG C, and cold rolling is carried out when the general reduction rate is between 65% to 85%; continuous annealing is carried out at the temperature ranging from 800 DEG C to 850 DEG C; cooling is carried out at the speed of 30-50 DEG C / second; pinch pass rolling is carried out for standby. The steel applied to automobiles of the invention has the characteristic that after stamping moulding and baking varnishing treatment the steel is hardened; meanwhile, and depression resistance of auto parts is improved, thus facilitating automobiles to be safer and more energy-saving.

Description

technical field [0001] The invention relates to steel for automobiles, in particular to a continuous hot-dip galvanized bake-hardened steel plate with a yield strength of 180 MPa and its production method Background technique [0002] Bake-hardening steel, referred to as BH steel, is based on low-carbon or ultra-low-carbon steel, through trace elements and corresponding process systems, a small amount of interstitial atoms C and N are dissolved in the production process, so that the steel plate in the delivery state The yield strength is relatively low, easy to form, the dislocation density of the steel base increases during the stamping process, and the interstitial atoms C and N diffuse toward the dislocation during the painting and baking process to pin the dislocation. Aging increases the yield strength of the steel, ultimately resulting in the production of auto parts with high dent resistance. [0003] The characteristic of bake-hardened steel is consistent with the t...

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Problems solved by technology

[0006] After searching, it was found that Pohang Iron and Steel Company of South Korea also carried out its development and research work. Its invention patent applied in the country, in order to improve the yield strength and dent resistance of steel, added Nb, Ti, B and Mo trace elements. Although the yield strength and dent resistance meet the requirements, from an economic point of view, it exists: as many as 4 types of trace alloy elements are added, which makes the addition complicated, high cost, low cost performance, and low strength. The r value is 1.5~1.6, that is, the formability is low, and the timeliness is only three months

[0007] Japan's JFE Iron and Steel Company patent JP2007009317 discloses literature reports that the low-carbon steel used, and the added trace alloy elements are Nb, Ti and B, in order to improve the yield strength and dent resistance of the steel, and its deficiency is still trace alloy More elements are added, and the cost performance is also lower

There is also an invention patent with a Chinese patent number of 200610169850, which discloses a trace alloying element added to ultra-low carbon steel as Ti and V. The amount of Ti added is large, and V is expensive, resulting in a large cost

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