| 摘要 |
PURPOSE:To obtain the titled inexpensive steel pipe of API-N80 class having low C content and high weldability, contg. no Mo, and capable of subjecting heat treatment in a wide temp. range by normalizing a steel pipe having specified contents of C, Si, Mn, V and N. CONSTITUTION:A steel consisting of 0.30-0.35% C, 0.20-0.30% Si, 1.60-2.00% Mn, 0.050-0.090% V, 0.0030-0.0100% N and the balance Fe is heated to about 1,270 deg.C and hot rolled to a steel plate. The plate is formed into a pipelike body, and edge parts of the body are welded by heating to manufacture a steel pipe. The pipe is normalized to obtain a steel pipe satisfying API standard. This pipe contains no expensive Mo, the weld zone is not cracked at all, and hardening and tempering are not required. |
