Microstructure and properties of a low-cost 800 MPa galvanized ultra-high strength dual-phase steel

doi:10.13251/j.issn.0254-6051.2021.08.015

Abstract

Abstract: Microstructure of hot-rolled, cold-rolled and hot-dip galvanized 800 MPa grade dual-phase steel was observed by means of optical microscope and transmission electron microscope (TEM). The mechanical properties at different positions of the whole rolled plate after hot-dip galvanizing were analyzed and compared. The results show that when the tested steel is annealed at 795 ℃ for 150 s and hot-dip galvanized, the microstructure is mainly composed of ferrite and martensite, the grain size of ferrite is between 2.3-6.0 μm, and the volume fraction of martensite is about 21%. After galvanizing, the tensile strength and yield strength are 825 MPa and 505 MPa respectively, the elongation after fracture is 19%, and along the width of the plate, the fluctuation of tensile strength is within 20 MPa, that of the yield strength is within 4 MPa, and that of the elongation is within 1%. When the transverse 180° bending test with bending diameter of 3 times of the plate thickness was conducted, the results show that no cracking happens from the head to the tail of the hot-dip galvanized whole coil steel, indicating that the requirements of user for high bending performance are met.

Key words: ultra-high strength dual-phase steel, hot-dip galvanizing, microstructure, martensite content, bending performance

CLC Number:

TG166.4

Liu Jingbao, Tian Xiugang, Zhang Jie, Wei Huanjun, Yang Lina, Wang Zhao, Li Mengxing. Microstructure and properties of a low-cost 800 MPa galvanized ultra-high strength dual-phase steel[J]. Heat Treatment of Metals, 2021, 46(8): 73-76.

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