HIGH-STRENGTH DUAL-PHASE STEEL SHEETS AND HIGH-STRENGTH DUAL-PHASE PLATED STEEL SHEETS AS WELL AS METHOD OF PRODUCING THE SAME

摘要

A composite structure type high tensile strength cold-rolled steel plate whichhas a chemical composition in mass %: C: 0.01 to 0.08 %, Si: 2.0 % or less,Mn: 3.0 % or less, P: 0.10 % or less, S: 0.02 % or less, Al: 0.005 to 0.20 %,N: 0.02 % or less, V: 0.01 to 0.5 % and balance: substantially Fe andinevitable impurities, provided that contents of V and C satisfy therelationship: 0.5 × C/12 = V/51 = 3 × C/12, and has a structurecomprising a ferrite phase as a primary phase and a second phase containing amartensite phase in an amount of 1 area % or more relative to the totalstructure; a galvanized plate of a composite structure type high tensilestrength steel which comprises the above steel plate and a hot dip zincplating formed thereon; and a method for producing the steel plate. Thecomposite structure type high tensile strength exhibits excellent deepdrawability.