슈퍼 2상 스테인리스강의 용접금속 미세조직에 미치는용접조건의 영향

Abstract

25% Cr super duplex stainless steels were shielded-metal arc welded with AWS E2594-17 rutile-type electrode to study the effects of heat inputs on the toughness and corrosion resistance of weld metals. Because of higher Ni content in electrode, weld metal had 2% higher Ni content than base metal and thus it had more austenite content. However, variation of heat inputs from 0.9 to 2.4kJ/cm gave little difference in chemical compositions and microstructure between weld metals. As σ-phase was not observed even in the weld metal with the highest heat input, the formation of σ-phase in the practical heat input ranges is impractical. The impact toughness of weld metal was influenced by the location of notch. It showed that the toughness was increased as the location of notch had reheated area. For example, the toughness was only 12J when the location had no reheated area, However, it was increased to 19J when it had reheated area. The reason for the higher toughness was attributed to the higher amount of austenite in the reheated area. Compared to 76% of austenite in the as-welded area, the amount of austenite was increased to 89% in the reheated area.