MANUFACTURE OF ELECTRICAL WELDED OIL WELL STEEL PIPE EFFICIENT IN LOW TEMPERATURE TOUGHNESS

摘要

PURPOSE:To obtain an electric welded oil well steel pipe improved for the low temperature impact characteristics and soundness of welded part and for machinability of screw, by a method wherein the steel lowered in C content and specified in the composition such as Mn to C ratio or the like, is hot-rolled, wound at a specified temperature and thereafter electrically seam-welded. CONSTITUTION:The steel of 0.07% max. C, 1.00-1.70% Mn, 0.3% max. Si,0.03% max. P, 0.005% max. S, 0.01-0.03% Ti, 12min the ratio of Mn to C, 0.15% max. Nb, 0.07% max. V, SolAl remained by deoxidizing regulation, remainder Fe and inevitable impurities, is hot-rolled. It is wound at 600 deg.C max., thereafter electrically seam-welded and the electric welded oil well steel pipe is obtained. Because this electric welded pipe is lowered in C content and raised in the ratio of Mn to C, the generated amount of carbide decreases and very fine ascicular ferrite is generated at any cooling rate. Further, because low alloy steel is used, the toughness of weld part is extremely improved.