450mpa-grade hot-dip galvanized dual-phase steel and its production method

Abstract

The invention discloses a 450MPa grade hot-dip galvanized dual-phase steel and a production method thereof, belonging to the technical field of cold-rolled strip production. The chemical composition of the dual-phase steel by mass percentage is: C 0.03%-0.10%, Si 0.20-0.60%, Mn 1.20%-2.00%, P≤0.020%, S≤0.010%, Als 0.015%-0.070%, N ≤0.0060%, the remaining elements are Fe and inevitable impurities; its microstructure is: 90-96% ferrite and 4-10% martensite by volume percentage. The preparation method includes the steps of smelting, hot rolling, pickling and hot-dip galvanizing. The production method of the dual-phase steel of the present invention adopts the sparse cooling method, which is beneficial to the stable control of the microstructure and properties; the opening and closing methods of the descaling and the cooling water between the racks are defined, which is beneficial to obtain a good surface quality. Combined with the smelting and hot-dip galvanizing process, the good mechanical properties and surface quality of the 450MPa hot-dip galvanized dual-phase steel sheet have been obtained, which has good market competitiveness.

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 properties, dual-phase steel has It is more and more favored by the automotive industry, and the proportion of applications in automobiles is 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 resistance. With the continuous improvement of the equipment capacity of hot-dip galvanizing ...

AI Technical Summary

Problems solved by technology

The 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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