HOT DIP GALVANIZED HIGH STRENGTH STEEL SHEET AND HOT DIP ZINCING HIGH STRENGTH STEEL SHEET HAVING EXCELLENT CORROSION RESISTANCE AND FORMABILITY, AND METHOD FOR PRODUCING THEM

摘要

PPROBLEM TO BE SOLVED: To provide a TRIP type hot dip galvanized high strength steel sheet and a hot dip zincing high strength steel sheet each having a uniform structure and excellent corrosion resistance and formability, and to provide methods for producing them. PSOLUTION: The hot dip galvanized high strength steel sheet is obtained by applying hot dip galvanizing to a steel sheet having a steel composition comprising, by mass, 0.05 to 0.25% C, ≤2.0% Si, 0.8 to 3% Mn, 0.0010 to 0.1% P, 0.0010 to 0.05% S, 0.0010 to 0.010% N and 0.01 to 2.0% Al, and the balance iron with inevitable impurities, and whose structure comprises retained austenite having a mean carbon content of ≥0.9% by ≥3%, and in which Mn micro-segregation in the range of 1/8t to 3/8t of the sheet thickness t lies in the range satisfying inequality (1): 0.10≥σ/Mn (1); wherein Mn denotes its additional amount; and σ denotes the standard deviation in Mn micro-segregation measurement. PCOPYRIGHT: (C)2007,JPO&INPIT