The Effect of Small Changes in Flux Basicity on the Acicular Ferrite Content and Mechanical Properties of Submerged Arc Weld Metal of Navy HY-100 Steel

摘要

The effect of small differences in flux basicity on the microstruc-ture and mechanical properties of submerged arc weld metal of Navy HY-100 steel has been investigated. It was found that an increase in the flux basicity index from 2.5 to 3.0 (calculated by the formula proposed by Tuliani, Boniszewski and Eaton, 1969, Weld. Met. and Fab. 37 (8): 327-329) led to a decrease in the total oxygen content of the weld metal from 0.034 to 0.027 wt-%. This decrease in weld metal oxygen content led to increasing average nonmetallic inclusion size and an increased propensity for acicular ferrite formation, which were found to increase both the strength and toughness of the weld metal. These results suggest that careful control of the chemistry of both the filler metal and flux is necessary to produce consistently high strength and toughness in weld metal during the submerged arc welding of HY-100 steel.