Method of producing high strength steel pipe

Abstract

A method of treating steel pipe made by forming and welding a mother plate. The pipe is shrunk in the radial direction by applying compressive radial pressure to the outside surface of the pipe to reduce the pipe diameter by at least about 1%. The shrinking of the pipe increases the circumferential compressive yield strength and decreases the circumferential tensile yield strength. The pipe is then heated to a temperature below the transformation temperature of the steel but high enough to increase the circumferential tensile yield strength of the pipe, preferably at least about 15% above the tensile yield strength of the mother plate. The heating step does not significantly decrease the high circumferential compressive yield strength of the pipe. The pipe is preferably heated to a temperature within the range of from about 500.degree. F to about 1000.degree. F, and the preferred heating technique is induction heating.

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