STEEL HAVING REDUCED RESIDUAL STRESS AND EXCELLENT FATIGUE CRACK PROPAGATION RESISTANCE CHARACTRISTIC

摘要

PROBLEM TO BE SOLVED: To provide a thick steel plate having reduced residual stress and excellent fatigue crack propagation resistance characteristic, and suitable for the structure of a hull, a bridge or the like.;SOLUTION: A steel having a specified chemical composition is subjected to hot rolling, and is thereafter subjected to two phase region quenching and tempering treatment under specified conditions, thus the metallic structure of the steel plate is made into the mixed one where a hard phase is composed of a tempered martensite phase having an area fraction of 15 to 85% and a Vickers hardness HV of ≥340 and a soft phase is composed of a ferrite phase whose Vickers hardness HV is limited to ≤130.;COPYRIGHT: (C)2008,JPO&INPIT