Metal treatment – Stock – Ferrous
Reexamination Certificate
2003-05-23
2009-10-13
Yee, Deborah (Department: 1793)
Metal treatment
Stock
Ferrous
C148S332000, C148S333000, C148S334000, C148S335000, C148S336000, C148S909000
Reexamination Certificate
active
07601231
ABSTRACT:
A high-strength steel pipe excellent in weldability on site and a method for producing the steel pipe by improving the reliability of the low temperature toughness of a steel are provided. For example, the steel pipe includes elements to enhance hardenability for furthering high-strengthening and also improving toughness at a weld heat affected zone subjected to double or more layer welding. In the method, the steel is made to consist of a structure composed of bainite and/or martensite by containing prescribed amounts of C, Si, Mn, P, S, Ni, Mo, Nb, Ti, Al and N, and, as occasion demands, one or more of B, V, Cu, Cr, Ca, REM, and Mg, and regulating C, Si, Mn, Cr, Ni, Cu, V and Mo. Such elements enhancing hardenability, by a specific relational expression. The diameter of prior austenite grains may be regulated in a prescribed range. The method may include heating a casting to a temperature not lower than the Ac3point, hot rolling such casting, and thereafter cooling the resulting hot-rolled steel plate at a prescribed cooling rate.
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Patent abstract of Japanese Publication No. 09165620 published Jun. 24, 1997.
Patent abstract of Japanese Publication No. 09165621 published Jun. 24, 1997.
Asahi Hitoshi
Hara Takuya
Baker & Botts LLP
Nippon Steel Corporation
Yee Deborah
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