STEEL HAVING EXCELLENT HYDROGEN EMBRITTLEMENT CRACKING RESISTANCE AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide high strength steel having good hydrogen embrittlement cracking resistance and also having strength of ≥1,200MPa.;SOLUTION: This steel having excelleng intergranular strength and excellent hydrogen embrittlement cracking resistance has a composition containing 0.1 to 0.5% C, ≤0.2% Mn and 0.5 to 2.5% Mo and also satisfying Mn≥20S. The steel has a martensite or lower bainite structure. In its production method, the process where the above steel is hot-worked, is directly, or after temporaly cooling, reheated to an austenitic temperature range, is thereafter rapidly cooled and is subsequently tempered at a temperature equal to or lower than the Ac1 transformation point is adopted.;COPYRIGHT: (C)2002,JPO