Method of producing steel for steel pipe excellent in sour-resistance performance
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United States of America Patent
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Jun 14, 2011
Grant Date -
Mar 25, 2010
app pub date -
Dec 2, 2009
filing date -
Nov 14, 2007
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Abstract
A method of producing steel pipe excellent in sour-resistance performance, uses comprises controlling the amount of Ca addition charged into molten steel in a ladle according to a N content in the molten steel prior to Ca addition. As a result of the controlling step, a CaO content in the inclusions is in the range of 30 to 80%, the ratio of the N content in the steel to the CaO content in the inclusions satisfies the relation expressed by equation (1), and a CaS content in the inclusions satisfies the relation expressed by equation (2). 0.28.ltoreq.[N]/(% CaO).ltoreq.2.0 (1) (% CaS).ltoreq.25% (2) where [N] represents the mass content (ppm) of N in the steel, (% CaO) represents the mass content (%) of CaO in the inclusions, and (% CaS) represents the mass content (%) of CaS in the inclusions.
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