PURPOSE: To produce a tough steel pipe having high strength, excellent corrosion resistance and less anisotropy of toughness, by subjecting a specifically composed ingot successively to heating, hot rolling, quick cooling, reheating, diametral reducing and air cooling under specific conditions.

CONSTITUTION: The ingot made of the compsn. contg., by weight %, 0.2W0.55% C, 0.01W0.6% Si, 0.3W1.8% Mn, and 0.005W0.06% Sol Al, and consisting of the balance Fe and unavoidable impurities is heated in a 1,050W1,250°C range. The ingot is then pierced by a piercer and is hot rolled by a mandrel mill. The finishing temp. is set at ≥800°C. The rolled steel is further quickly cooled down to ≤350°C at ≥200°C/min cooling rate in a 800W500°C range to form the structure substantially consisting of ≥50vol% martensite and the balance bainite. The steel is then reheated to the Ac1 transformation point W (Ac1 transformation point - 200°C) at which there is substantially no formation of martensite; thereafter, the steel is subjected to the diametral reducing at ≥5% reduction ratio by using a reducer and is air cooled, by which the rolled steel pipe is formed.