Cold-rolled hot-galvanized dual-phase steel plate with flanging property and manufacturing method thereof

Abstract

The invention relates to a cold-rolled hot-galvanized dual-phase steel plate with a flanging property and a manufacturing method thereof. The steel plate comprises the following chemical components by weight percent: 0.06% to 0.095% of C, 0.3% to 0.6% of Si, 1.4% to 1.8% of Mn, greater than 0% and less than or equal to 0.02% of P, greater than 0% and less than or equal to 0.01% of S, 0.02% to 0.05% of Al, 0.35% to 0.55% of Cr, 0.02% to 0.04% of Nb, greater than 0% and less than or equal to 0.005% of N and the balance of Fe. According to the steel plate provided by the invention, the austenite is dispersedly distributed in a ferrite matrix via the refining of austenite grains by adding the Nb element and controlling temperatures during hot rolling and finish rolling and a rolling temperature; the amount of the austenite after annealing is increased by limiting the content of C and carrying out high-temperature annealing in a continuous hot-galvanized annealing furnace, so that tissues in low-C martensite are obtained after quenching. Thus, the hardness of the martensite is decreased. As a result, a hardness difference between the martensite phase and the ferrite phase is reduced.

Description

technical field [0001] The invention relates to the technical field of cold-rolled high-strength thin plates for automobiles, in particular to a cold-rolled hot-dip galvanized dual-phase steel plate with flanging characteristics and a manufacturing method. Background technique [0002] In recent years, with the continuous improvement of people's requirements for car crash safety and corrosion resistance, steel sheets for automobiles have developed towards high strength and full coating, which has prompted high-strength IF steels, bake-hardening steels, phase-transformation-induced plasticity steels and double-layer steels. The application of hot-dip galvanized high-strength steel such as phase steel in automobile body. At the same time, in order to reduce the greenhouse effect and protect the earth's environment, strengthen the control of CO 2 The limitation of emissions, which contributes to the lightweight of automobile bodies with low fuel consumption, has become an impo...

AI Technical Summary

Problems solved by technology

For ordinary hot-dip galvanized dual-phase steel, the internal phase structure of the matrix is ​​mainly composed of martensite (hard phase) and ferrite (soft phase). The hardness difference between the two phases is large, and the hole expansion rate is poor, causing Poor flanging performance

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