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:
Oct. 13, 1998
Filed:
Dec. 13, 1996
Nippon Steel Corporation, Tokyo, JP;
Abstract
A steel pipe having excellent corrosion resistance in an environment containing wet carbon dioxide and a small amount of hydrogen sulfide and having also excellent weldability is produced at a low production cost and with high productivity. The production method comprises heating to a temperature of 1,050.degree. to 1,300.degree. C. a slab containing, in terms of wt %, 0.01 to less than 1.2% of Si, 0.02 to 3.0% of Mn, 7.5 to 14.0% of Cr and 0.005 to 0.5% of Al, reduced C, N, P and S contents, at least one of Cu, Ni, Co, Mo and W, a balance of Fe and unavoidable impurities, and having an MC value of at least 0, finishing hot rolling within an austenite monophase temperature range, coiling the steel sheet as a hot coil having a sheet thickness of 3.0 to 25.4 mm, cooling the coil at a cooling rate of at least 0.01.degree. C./sec to at least 500.degree. C. to convert the steel sheet to a steel substantially consisting of martensite, reheating the steel to a temperature of 550.degree. C. to not more than an A.sub.c1 transformation point, holding it for at least 15 minutes, cooling the steel web to a normal temperature, cutting it into a predetermined width, and welding both ends of the steel by electric resistance welding while the steel coil is continuously shaped into a cylindrical shape.