Comparative analysis on delta ferrite determination for austenitic stainless steels

ABSTRACT In the welding of austenitic stainless steels, the determination of delta ferrite (δ-ferrite) is very important to assess the susceptibility of weld metal to hot cracking, one of the major problems related to weldability, metallurgical and mechanical behavior of this type of steels. The determining δ-ferrite in the weld metal can be performed with predictive methods from the chemical composition of weld metal provided by the welding consumable (the diagram of Schaeffler, Delong, WRC 1988, WRC1992), by metallography and using nondestructive testing technique by magnetic determination of ferrite. This paper presents a comparative analysis of the predictive determination of δ-ferrite and the magnetic method using austenitic stainless electrodes for SMAW process using different classifications and diameters. The filler metals used correspond to different batches of such consumables and it has used a standardized methodology for magnetic determination. The correlation between the two methods seems to work best for NF values between 4 and 8. Errors and the correlation between the two methods applied to determine NF are not acceptable when the electrodes deposit solder metals with high NF values, greater than 18.