| 摘要 |
A hot water tank having, on the inner surface thereof, a back bead formed by TIG-welding with no back gas sealing of steel members to each other having a composition comprising, % by mass, C: at most 0.025 %, Si: at most 1 %, Mn: at most 1 %, P: at most 0.045 %, S: at most 0.01 %, Ni: from 0.1 to 1 %, Cr: from more than 21 to 25 %, Mo: from 0.1 to 2 %, Al: from 0.02 to 0.3 %, N: at most 0.025 %, and Cu: from 0 to 1 %, and containing at least one of Ti: from 0.05 to 0.4 % and Nb: from 0. 05 to 0. 5 %, with the balance of Fe and inevitable impurities, wherein the Cr concentration in the steel basis material in the area having oxide scale soluble in an aqueous chloride solution, as formed therein in the heat-affected zone on the welded back side thereof, is at least 16 % by mass in the depth region of at least 10 nm from the steel basis material/oxide scale interface. |
