| 摘要 |
PROBLEM TO BE SOLVED: To suppress breakage of a steel material when impact deformation is caused, even when static-deformation resistance of the steel material is made not too high (the safety ratio is made not too high). SOLUTION: The steel has the component composition composed of 0.05-0.5% C, 0.005-0.50% Si, 0.2-0.80% Mn, ≤0.050% P, 0.005-0.05% S, 0.05-0.30% Cr, 0.005-0.06% Al, 0.0005-0.0055% B, 0.0005-0.008% N, ≤0.0010% solid-solution N and the balance Fe with inevitable impurities, wherein a structure has a ferrite-pearlite structure in which a ferrite fraction is 55-97 area%, and regarding the inclusion, the diameter of the maximum nitride-based inclusion containing B is ≥100 nm, and the number of the nitride-based inclusion containing B and having the diameter of ≥100 nm is 0.010-0.05 pieces/μm<SP>2</SP>.The steel is improved in the shocking deformation resistance. COPYRIGHT: (C)2011,JPO&INPIT |
