HIGH-STRENGTH WITH LOW RATIO OF FLOWABILITY LIMIT TO STRENGTH LIMIT OF ZINC COATED SINKING STEEL SHEET, HIGH-STRENGTH WITH LOW RATIO OF FLOWABILITY LIMIT TO STRENGTH LIMIT OF ANNEALED COATED BY SINKING STEEL SHEET, METHOD OF PRODUCTION OF HIGH-STRENGTH WITH LOW RATIO OF FLOWABILITY LIMIT TO STRENGTH LIMIT OF COATED BY SINKING STEEL SHEET AND METHOD OF PRODUCTION OF HIGH-STRENGTH WITH LOW RATIO OF FLOWABILITY LIMIT TO STRENGTH LIMIT OF ANNEALED COATED BY SINKING STEEL SHEET

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to metallurgy, particularly, to high-strength hot-dip galvanised steel sheet used in motor-car production. Sheet is made of steel containing in wt %: 0.03-0.20 C, 1.0 or less Si, 1.5-3.0 Mn, 0.10 or less P, 0.05 or less S, 0.10 or less Al, 0.010 or less N, 0,5 or less Cr and 0.01-0.50 Mo, Fe and unavoidable impurities making the rest. Sheet microstructure comprises ferrite and secondary phase. Fraction of ferrite area makes 50% or more while fraction of secondary phase area including martensite makes 7-25%. Martensite crystal grain mean size makes 1-8 mcm. Sheet features yield point-to-breaking point ratio making 0.7 or less, high mouldability and coating properties.;EFFECT: high-strength hot-dip galvanized steel sheet.;10 cl, 3 tbl, 1 ex