The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 20, 2014
Filed:
May. 29, 2006
Kenji Oi, Chiba, JP;
Akihide Nagao, Kurashiki, JP;
Kenji Hayashi, Kurashiki, JP;
JFE Steel Corporation, Tokyo, JP;
Abstract
The invention provides a high tensile strength steel material having a tensile strength of 600 MPa, which is excellent in delayed fracture resistance property, and a method of manufacturing the steel material. As means for this, a steel material contains, in mass percent, C of 0.02 to 0.25%, Si of 0.01 to 0.8%, Mn of 0.5 to 2.0%, Al of 0.005 to 0.1%, N of 0.0005 to 0.008%, P of 0.03% or less, and S of 0.03% or less. In addition, the steel material contains at least one element selected from Mo, Nb, V, and Ti, and contains at least one of Cu, Ni, Cr, W, B, Ca, REM and Mg, as needed. The remainder includes Fe and inevitable impurities. In addition, in the steel material, precipitates having an average grain size of 20 nm or less, which contains at least one of Mo, Nb, V and Ti, are contained in steel in the number of at least 5 per 250000 nm, and a microstructure includes residual austenite in a volume fraction of 0.5 to 5%. When Ca to be added is specified to be 0.0010% to 0.0020%, it is specified that S is 0.0005% to 0.0020% and O is 0.0008% to 0.0025%. ACR is specified to be 0.2≦ACR(=(Ca−(0.18+130*Ca)*O)/1.25/S)≦1.0.