초록 ▼

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% bu

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.

대표청구항 ▼

[ What is claimed is:] [1.] A high-tensile-strength steel with a tensile strength of not less than 900 MPa, consisting essentially of, by weight percent: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

[ What is claimed is:] [1.] A high-tensile-strength steel with a tensile strength of not less than 900 MPa, consisting essentially of, by weight percent: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%;B: 0% to 0.0004%;Cu: 0% to 0.4%;Cr: 0% to 0.8%;Mo: 0% to 0.6%;V: 0% to 0.1%; andCa: 0% to 0.006%; and balance Fe and incidental impurities; rein the condition (a) and (b) below is satisfied, and P and S among unavoidable impurities are contained in an amount of not greater than 0.015% and not greater than 0.003%, respectively:(a): the carbon equivalent value Ceq defined by equation 1) below being 0.53% to 0.7%; EQU Ceq=C+(Mn/6)+{(Cu+Ni)/15}+{(Cr+Mo+V)/5} 1): rein each atomic symbol represents the content (wt. %) of the corresponding element;(b): a mixed structure of martensite and lower bainite occupying at least 90 vol. % in the microstructure; lower bainite occupying at least 2 vol. % in the mixed structure; and the aspect ratio of prior austenite grains being not less than 3.