Patent ID: 8328960

Claim:
Process A method for the production of high strength bainitic steel seamless pipes comprising the following steps: a) providing a steel having a composition comprising 0.2-0.4% by weight of C 0.05-1.5% by weight of Mn; 1.0-2.0% by weight of Si and 0-0.5% by weight of Al or, alternatively, 1.0-2.0% by weight of Al and 0-0.5% by weight of Si; 0.5-2.0% by weight of Cr; 0.2-0.5% by weight of Mo; 2.0-3.7% by weight of Ni; the remainder being iron and inevitable impurities; b) hot rolling said steel at a temperature to obtain a seamless steel pipe; c) continuously cooling the steel from the rolling temperature naturally in air or by a controlled cooling with an average cooling rate of between 0.10 and 1.0° C. per second in order to obtain mainly cementite-free bainitic structures; wherein the steel has a transversal toughness that satisfies one or more of the following: a transversal toughness at 24° C. of at least 69-75 J, a transversal toughness at 0° C. of at least 58-68 J, and a transversal toughness at −20° C. of at least 49-52 J.