| 摘要 |
PROBLEM TO BE SOLVED: To produce a steel by which deterioration in the toughness of a welded joint is evaded, and capable of obtaining a liquid phase diffusion welded joint excellent in toughness and to provide a method for welding the same. SOLUTION: This steel suitable for liquid phase diffusion welding has a composition containing, by mass, 0.02 to 0.20% C, 0.01 to 1.0% Si, 0.01 to 2.0% Mn, 0.0005 to 0.03% N, 0.001 to 0.1% Ti and 0.001 to 0.1% Zr, in which, the content of P is limited to <=0.03%, S to <=0.03%, 0 to <=0.03%, and Al to <=0.01%, and the balance Fe with impurity components, and also, Ti(%), Zr(%) and N(%) satisfy 0<; (Ti(%)+Zr(%))-5N(%)<; 0.15, the average grain size of the nitrides, carbides or carbonitrides of Ti and Zr is <=0.1μm, also, the maximum grain size thereof does not exceed 1μm, and, moreover, even when the liquid phase diffusion-weld zone is heated at a temperature equal to or above the transformation point, the average crystal grain size in the weld heat affected zone is <=100μm. The liquid phase diffusion welding is executed in such a manner that the welding temperature is controlled to <=1,300 deg.C, and the time for which the weld zone is exposed to the temperature equal to or above the transformation point is controlled to <=30 min. |
