Formation mechanism of vermicular and lacy ferrite in austenitic stainless steel weld metals

摘要

Solidification and subsequent transformation of austenitic stainless steel weld metals that solidified in the ferritic-austenitic mode were investigated from the viewpoint of crystallography. The formation mechanisms for the vermicular and lacy ferrite observed in the weld metals were clarified. The ferrite morphology is determined by both the crystallographic orientation relationship between ferrite and austenite established at the stage of ferrite nucleation and the relationship between the welding heat source direction and the preferential growth directions of ferrite and austenite. In particular, for the formation of continuous lacy ferrite, it is necessary that the ferrite continues to grow with the Kurdjumov-Sachs orientation relationship with austenite that is established at the stage of ferrite nucleation.