サブマージアーク溶接金属の凝固過程に関する研究 ＩＩ 凝固条件と凝固組織の関係

Abstract

Relationships among the solidification variables and the primary structures which significantly affect the mechanical properties of Weld metals have been investigated using 25Cr-20Ni austenitic submerged arc welds composed of one-directionally solidified structures.Over the tested range of heat input grain growth in the heat affected zone of as-casted plates occurred to a lesser extent than solid-solution treated plates. Width of columnar grains was agree with the base plate austenite grain size at the fusion boundary, and increased toward the weld center. Quantitative correlation among columnar grain width and the solidification variables, however, was not observed.Coarsening and the morphological change of dendritic structures took place in the same manner as casting, and the primary dendrite arm spacings are in reciprocal proportion to the square root of cooling rate in the liquid-solid region. Coarsening process of cell structures can be also explained by variations in cooling rate like dendritic structures. In a elliptical shaped weld puddle solidifying with dendritic structures, cooling rate in the solid increased with an increase in the distance from the fusion boundary, whereas cooling rate in the liquid-solid region varied inversely.