HIGH STRENGTH STEEL SHEET, UNSINTERED HIGH STRENGTH STEEL SHEET AND METHOD FOR PRODUCING THEM

摘要

PROBLEM TO BE SOLVED: To provide a new low-alloy steel sheet combining high strength and satisfactory workability, and to provide a method for producing the same. SOLUTION: Lath-shaped austenite having a carbon concentration of≥0.9 mass% in a volume ratio of≥3%, and a lath-shaped martensite or granular martensite with the average grain diameter in a volume ratio of≥10% are present in the grains or on the grain boundaries of ferrite with the average grain diameter of≤10μm. The Mn equivalent calculated according to Mn+1.4Cr+3P+1.5Mo+180B by mass% of the respective componential elements to be incorporated is desirably≤2.35. COPYRIGHT: (C)2007,JPO&INPIT