450 MPa-grade hot-dip galvanized dual-phase steel and production method thereof

Abstract

The invention discloses 450 MPa-grade hot-dip galvanized dual-phase steel and a production method thereof, and belongs to the technical field of cold-rolled strip production. The dual-phase steel comprises the following chemical components in percentage by mass: 0.03%-0.10% of C, 0.20%-0.60% of Si, 1.20%-2.00% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.015%-0.070% of Als, less than or equal to 0.0060% of N and the balance of Fe and inevitable impurities. The microstructure of the dual-phase steel comprises the following components in percentage by volume: 90%-96% of ferrite and 4%-10% of martensite. The preparation method comprises the steps of smelting, hot rolling, acid rolling and hot galvanizing. According to the production method of the dual-phase steel, the sparse cooling mode is adopted, and stable control over the structure performance is facilitated; the opening and closing mode of cooling water between descaling and the rack is defined, and good surface quality can be obtained; and through cooperation of smelting and hot galvanizing processes, the good mechanical properties and surface quality of the 450 MPa-grade hot-dip galvanized dual-phase steel plate are achieved, and the good market competitiveness is achieved.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled strip production, and in particular relates to a 450MPa grade hot-dip galvanized dual-phase steel and a production method thereof. Background technique [0002] With the continuous development of automobile lightweight and the continuous improvement of occupant safety requirements, the proportion and amount of high-strength steel in automobile body-in-white have increased rapidly in recent years. Due to its high strength, low yield ratio and good forming It is more and more favored by the automobile industry, and the proportion of applications in automobiles is constantly increasing. Compared with cold-rolled dual-phase steel, galvanized dual-phase steel also has excellent anti-corrosion properties, which can ensure that automobiles have good corrosion resistance and perforation ability. Currently, it is mainly used in structural parts and reinforcements of mid-to-high-end cars. With the cont...

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Problems solved by technology

This patent adopts the ultra-low carbon (0.0036~0.0049%C) route, which needs to go through a vacuum RH furnace during smelting, which increases the process cost, and adds a large amount of Mn, Nb, Ti, and B elements, which increases the cost of the alloy and significantly improves the refractory temperature. Crystallization temperature (soaking temperature is 810-830°C), high process cost

The most important thing is that it is strengthened by phosphorus (P) (P: 0.078~0.095%), which is prone to grain boundary segregation. Although the elongation may be good, the forming effect is not good

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