HIGH-TOUGHNESS, HIGH-TENSILE-STRENGTH STEEL AND METHOD OF MANUFACTURING THE SAME

摘要

High-tensile-strength steel having excellent arrestability and a TS of not less than 900 MPa, as well as a method of manufacturing the same. The steel of the invention has the following composition (% by weight): C: 0.02% to 0.1%; Si: not greater than 0.6%; Mn: 0.2% to 2.5%; Ni: greater than 1.2% but not greater than 2.5%; Nb: 0.01% to 0.1%; Ti: 0.005% to 0.03%; N: 0.001% to 0.006%; Al: not greater than 0.1%; and optional elements. Ceq of the B-free steel is 0.53-0.7%, and Ceq of the B-bearing steel is 0.4-0.58%. The microstructure of the steel may be a mixed structure of martensite (M) and lower bainite (LB) occupying at least 90 vol.% in the microstructure, LB occupying at least 2 vol.% in the mixed structure, and the aspect ratio of prior austenite grains is not less than 3 .