rolling in a continuous roller, of the restrained or floating mandrel type (Multi-stand Pipe Mill (MPM) or continuous mandrel mill) following a first heating stage conducted at temperatures comprised substantially within the range of 1200-1300° C. for a period of approximately 1 hour in an atmosphere of combustion gases with an O2 content going from 1 to 1.5%, and a second heating stage conducted at a temperature substantially comprised within the range of 850-1100° C. in an atmosphere of combustion gases with an O2 content going from 1 to 1.5% for an approximate period of 30 minutes;
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