Combined mechanical and thermal processing method for production of seamless steel pipe

A process for producing a seamless steel pipe comprising the steps of:

• a. primary hot working a bloom into a mother tube of intermediate cross-section comparatively nearer to that of the finished pipe product;
• b. removing scale from the outside surface of said mother tube while being entirely austenitized;
• c. secondary hot working said mother tube into a pipe of final dimensions with a degree of work applied thereto, measured in terms of equivalent strain (.epsilon.) as expressed by the following formula, of not less than .epsilon. = 0.02.
• .epsilon. = .sqroot.2/3) .sqroot. (.epsilon..sub.1 - .epsilon..sub.2).sup.2 + (.epsilon..sub.2 - .epsilon..sub.3).sup.2 + (.epsilon..sub.3 - .epsilon..sub.1).sup.2
• wherein
• .epsilon..sub.1 = ln(l.sub.2 /l.sub.1)
• .epsilon..sub.2 = ln(t.sub.2 /t.sub.1)
• .epsilon..sub.3 = ln[(2r.sub.2 - t.sub.2)/(2r.sub.1 - t.sub.1)]
• in which l.sub.1, t.sub.1 and r.sub.1 are the length, thickness and radius of the mother tube respectively, and l.sub.2, t.sub.2 and r.sub.2 are the length, thickness and radius of the pipe of final dimensions respectively;
• and
• d. directly quenching said pipe of final dimensions;
• and
• e. tempering said quenched pipe below the Ac.sub.1 transformation point for the steel.