Sumitomo Metal Industries, Inc.

Shingo Takeuchi

Tomohiko Omura

Mitsuhiro Numata

A method of producing steel for a steel pipe excellent in sour-resistance performance comprises controlling the amount of Ca addition charged into a molten steel in a ladle according to a N content in the molten steel prior to Ca addition. Non-metallic inclusions in the steel are mainly composed of Ca, Al, 0 and S, and 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 satisfying equation (1), and a CaS content in the inclusions satisfies equation (2),0.28&#x2266;[N]/(% CaO)&#x2266;2.0&#x2003;&#x2003;(1)(% CaS)&#x2266;25%&#x2003;&#x2003;(2)

Method of producing steel for steel pipe excellent in sour-resistance performance

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&#x2266;[N]/(% CaO)&#x2266;2.0&#x2003;&#x2003;(1)(% CaS)&#x2266;25%&#x2003;&#x2003;(2)

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Kashima, Japan

Shingo Takeuchi