Effect of Flux Composition on Weld Metal Toughness and Workability in Submerged Aye Welding with 60kgf/$\textrm{mm}^2$ Grade C-Mo Type Wires

60kgf/$\textrm{mm}^2$급 C-MO계 와이어를 사용한 서브머지드 아크 용접금속 인성 및 작업성에 미치는 플럭스 조성의 영향

Effect of a flux composition on weld metal toughness in submerged arc welding with 60kgf/$\textrm{mm}^2$ grade C-Mo type wires was investigated and interpreted in terms of weld metal microstructure and hardenability. Flux workability was also studied by characterizing a weld bead profile. Compared to other weld metals, .weld metal used alumina basic flux with nickel showed lowest oxygen content, highest hardenability and the most acicular ferrite. The highest impact toughness of that weld metal, however, was attributed to the tough matrix due to the nickel rather than to the larger amount of acicular ferrite. Manganese silicate flux had better workability than alumina basic flux, showing broader welding conditions resulting in a depth-to-width ratio of 0.5. The composition of oxides in the weld metal was dependent on the flux composition, showing MnO-SiO$_2$-TiO in manganese silicate flux and MnO-SiO$_2$-Al$_2$O$_3$-TiO in alumina basic flux. MnO-SiO$_2$composition in both oxides was similar to a tephroite.