| 摘要 |
PURPOSE:To improve remarkably the low-temp. toughness of the same-metal welded part by heat-treating the same-metal welded part under specified conditions when a low-temp. steel pipe contg. Ni is welded by using a same-metal welding material and then the same-metal welded part is hardened and tempered. CONSTITUTION:When a low-temp. steel pipe contg. Ni is welded by using a same-metal welding material and then the same-metal welded part is submitted to short-time hardening and tempering, the same-metal welded part is kept at 550-650 deg.C for 1-10min before the part is hardened to improve the low-temp. toughness of the same-metal welded part. The welding material is preferably composed of <=about 0.08% C, about 0.01-0.45% Si, about 0.3-1.0% Mn, <=about 0.01% P, <=about 0.01% S, <=about 0.035% O, <=about 0.01% N, and the remainder of an appropriate amt. of Ni, Fe, and inevitable impurities. |
