대기용해 시 내화물 도가니의 종류가 가돌리늄(Gadolinium)을 함유한 듀플렉스 스테인레스 강의 미세조직에 미치는 영향

Abstract

This paper reports the effect of a refractory crucible type on the microstructure of duplex stainless steel (DSS) cast with the addition of gadolinium using air-induction melting. Grade 4A DSSs with 1 wt% of gadolinium (Gd) were fabricated in various crucibles including alumina (<TEX>$Al_2O_3$</TEX>), magnesia (MgO), calcia (CaO) coated with yttria (<TEX>$Y_2O_3$</TEX>) and graphite. The standard free energies of the formation of calcium and yttrium oxide were lower than those of gadolinium oxide and other crucible elements based oxide. The yield of Gd in DSS using <TEX>$Al_2O_3$</TEX>, MgO, CaO-coated <TEX>$Y_2O_3$</TEX> and graphite was 5, 19, 83 and 96%, respectively. As Gd yield increased, the amount of Gd-based inclusions increased, the size of the inclusions were reduced, and the inclusions became evenly distributed.