| 摘要 |
PROBLEM TO BE SOLVED: To provide a high tensile strength steel plate combining high strength with excellent workability without causing a decrease in productivity and an increase in manufacturing costs due to heat treatment in a plurality of stages, regulation of initial cooling temperature, etc., and also to provide its manufacturing method. SOLUTION: The high tensile strength steel plate with excellent workability has a composition consisting of, by mass, 0.005 to 0.02% C, 0.05 to 0.50% Si, 1.0 to 2.5% Mn, 0.01 to 0.08% Al, 0.010 to 0.060% Nb, 0.005 to 0.025% Ti, 0.0010 to 0.0040% B,≤0.050% P,≤0.0050% S,≤0.010% N and the balance Fe with inevitable impurities. In the steel plate, a relation of formula (1) is satisfied: (1) (hardness in the surface layer part of the steel plate)+(15 Hv)<(hardness in the central part of the plate thickness of the steel plate). COPYRIGHT: (C)2007,JPO&INPIT
|
