CTOD 성능향상을 위한 용접부 oxide 형성 및 미세조직 영향 기초연구

Abstract

In this study, the effects of REM addition on the weld metal microstructure and nonmetallic inclusion were investigated to rationalize high CTOD value of REM added weld metal. It showed that REM added weld metal retards grainboundary ferrite formation due to the segregation of REM at grainboundary, resulting in less grainboundary ferrite compared to weld metal without REM. As cracks propagate preferentially along grainboundary ferrite in CTOD test, less amount of grainboundary ferrite is believed the reason for the high CTOD toughness in REM added weld metal. As nonmetallic inclusions contained no REM element and the characteristics of nonmetallic inclusions are almost same as those in weld metal without REM, it is believed that REM addition has little effect on the modification of nonmetallic inclusion.