Development of dissimilar welding technique between PNC-FMS wrapper tube and SUS316 steel (1); Investigation of ferrite formation and evaluation of charpy impact property

not registered; Mizuta, Shunji ; not registered  

Ferritic/Martensitic steel (PNC-FMS) with superior resistance to swelling is being developed as wrapper tube for the long-life core of large-scale fast breeder reacor. If the ferrite phase would be formed at heat affected zone(HAZ)in welding between PNC-FMS wrapper tube and SUS316 steel,and thus toughness degradation would be suspected due to ferrite formation. In this study, the formation of the ferrite in applying TIG welding and EB welding are investigated using base metal of 3 types, which are Ni max./Cr min., Ni min./Cr max. and the center of chemical composition in the specification. The effect of the amount of the ferrite formation and characteristics of toughness change with thermal aging were evaluated. The results are summarized as follows. (1)The ferrite generation can be suppressed in the combination of welding process and chemical composition. (a)In case of specification center, the ferrite formation can be suppressed about 1% by EB welding. (b)In case of Ni max./Cr min. in the specification, the ferrite formation can be perfectly suppressed even in TIG welding or EB welding.