Dual-phase steel

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Dual-phase steel is a high-strength steel which is heat treated to contain both a ferrite and martensic microstructure for extra strength. It's highly formable steel and has a low alloy content and high strength. The desire to produce higher strength steels with formability greater than conventional controlled rolled high strength micro alloyed steel led the development of DPS in 1970s[2]. Dual-phase steel features a soft ferrite microstructure, with a matrix containing islands of martensite in the secondary phase (increasing amounts of martensite increase the tensile strength.) Dual-phase steel features a low yield ratio (i.e. yield strength to tensile strength), high tensile strength and high work hardening rate.

The steel melt is produced in an oxygen top blowing process in the converter, and undergoes an alloy treatment in the secondary metallurgy phase. The product is aluminum-killed steel, with high tensile strength achieved by the composition with manganese, chromium and silicone. The martensitic phase is produced by quenching a hot cold rolled strip before entering azinc pot of ahot-dip galvanization unit. Their Advantages are as follows [1,2]: Low yield strength Low yield to tensile strength ratio High initial strain hardening rates Continuous yielding Good uniform elongation Excellent combinations of tensile strength, ductility and toughness Capacity to absorb crash energy Ability to resist fatigue

1-A.Fallahi, Microstructure-Properties Correlation of Dual Phase Steels Produced by Controlled Rolling Process, J. Mater. Sci. Technol, V01.18 No.5, 2002

2-P.C. Chakraborti, M.K. Mitra, Microstructure and tensile properties of high strength duplex ferrite-martensite (DFM) steels, Materials Science and Engineering, Pages 123-133,2007