Metallurgical Factors Influencing Hot Ductility of Austenitic Steel Piping at Weld Heat-Affected Zone Temperatures

The variable hot ductility of wholly austenitic Type 347 steel was found to be associated with the variable temperature of formation of a liquid phase (liquation temperature) in the microstructure of the steel. In wholly austenitic materials a low liquation temperature leads to poor hot ductility. The liquation temperature of the steel was determined to be a function of its columbium, carbon, and nitrogen contents. When ferrite is present in the steel, poor hot ductility can also occur as a result of the crack sensitivity of the two-phased structure.