完全オーステナイト系Fe-Cr-Ni合金の溶接高温割れ感受性に及ぼすNi量の影響

The effect of Ni content on weld hot cracking susceptibility of Fe-20%Cr-Ni alloys, which solidify as austenitic single phase, was investigated. In addition, the effect and effect mechanism of alloying elements on weld hot cracking susceptibility of such alloys was studied in the varied ranges of Ni constitution. A theory that can explain general effect and effect mechanism of alloying elements on weld hot cracking susceptibility has not completely been established in the different ranges of major constituents. However, there are many reports concerning the improvement of hot cracking susceptibility in only limited ranges of major constituents.As an experiment, a Trans-Varestraint test and hot tensile test were conducted. The influence of alloying elements on solidification temperature range and liquid fraction during solidification was also investigated using Thermo-Calc. Solidification sequence of Fe-20%Cr-Ni alloys was also investigated by freezing the solidification microstructure with liquidtin quenching during gas tungsten arc welding.As a result, the maximum hot cracking susceptibility of Fe-20%Cr-Ni alloys was observed in the Ni content range from 30% to 60%. Therefore, dependence of hot cracking susceptibility on Ni content can be explained qualitatively by the effect of increase in solidification temperature range around 45%Ni.