低炭素鋼大入熱エレクトロスラグ溶接金属の高靭性化

抄録

This paper deals with the improvement in the weld metal toughness by the formation of the fully acicular ferrite microstructure in the high heat input electroslag welding. Applying the high Ti bearing welding wire and the low basicity flux provided a large number of Ti containing oxide inclusions in the weld metal, which were effective for the acicular ferrite formation. B addition to the weld metal suppressed the formation of the coarse grain boundary ferrite and the proper B/N ratio of the weld metal ranged from 0.5 to 0.8. In the B/N ratio exceeding 0.8, the weld metal toughness was reduced because of the increase in the M-A constituent. The weld metal with the fully acicular ferrite and the proper B/N ratio exhibited the excellent toughness (vE0>100J) even at the high heat input as high as 100kJ/mm.