HIGH-STRENGTH STRUCTURAL STEEL MATERIAL HAVING EXCELLENT FATIGUE CRACK PROPAGATION INHIBITORY CHARACTERISTICS AND MANUFACTURING METHOD THEREFOR

摘要

A high-strength structural steel material having excellent fatigue crack propagation inhibitory characteristics according to an aspect of the present invention contains, by weight, 0.02-0.12% of C, 1.7-2.5% of Mn, 0.01-0.8% of Si, 0.005-0.5% of Al, and the balance Fe and unavoidable impurities, wherein a microstructure of the structural steel material is divided into a surface layer portion outside and a central portion inside along a thickness direction; the surface layer portion may comprise tempered bainite as a matrix structure, fresh martensite as a second structure, and austenite as a residual structure; and the central portion may comprise lath bainite.