High strength steel for structure having excellent fatigue crack arrestability and manufacturing method thereof

摘要

The present invention provides a high strength steel material for a structure, effectively obtaining a property of suppressing the spread of fatigue cracks and high strength, and a manufacturing method for the same. According to an embodiment of the present invention, the high strength steel material for a structure, having an excellent property of suppressing the spread of fatigue cracks, includes: 0.02-0.12 wt% of C; 1.7-2.5 wt% of Mn; 0.01-0.8 wt% of Si; 0.005-0.1 wt% of Nb; 0.005-0.1 wt% of Ti; 0.005-0.5 wt% of Al; 0.02 wt% or less of P; 0.004 wt% or less of B; 0.015 wt% or less of N; 0.01 wt% or less of S; and residues including Fe and inevitable impurities. A fine structure is divided into a surface layer unit on the outer side and a center unit on the inner side in the thickness direction. The surface layer unit includes tempered bainite as a base structure. The surface layer unit includes fresh martensite as a second phase and also includes austenite as a residual structure. The center unit includes less bainite.