Effect of Solidification Phase on the Toughness of Steel Weld Metal (Report 3)

Effect of Solidification Rate on the Tougness of as-solidified Steel

Abstract

Previous reports showed that the toughness of as-solidified steel was significantly influenced by the injurious sulfur-segregation through the Fe-Ni-C ternary peritectic reaction. This peritectic reaction may be affected by the solidification rate.
Then, in this study the influences of solidication rates on solidification structures, sulfur-segregation and toughness were investigated using as-solidified steel through and not through the Fe-C and Fe-Ni peritectic reaction. The solidification rates were changed by three kinds of molds, corresponding to manual arc welding or TIG welding, submerged arc welding and electroslag welding.
The results obtained are as follows;
1) In the cases of 0.3 mm/sec and 1.4 mm/sec solidification rate, the toughness of as-solidified steel deteriorates abruptly and the solidification grain boundary is etched remarkably at about 0.1 % of carbon content and 2.5 % of nickel content.
These critical contents decrease with an increasing solidification rate.
2) Micro-segregation of sulfur on solidification grain boundary and deterioration of stoughness increase with a decreasing solidification rate.