Influence of process parameters on ferrite content in GTAW cladding metal of 304L stainless steel

The content and shape of ferrite in the weld of austenitic stainless steel would significantly affect its performance. In order to explore the influence of welding parameters on the ferrite number in the weld,GTAW procedure test of 304L stainless steel was carried out under the protection of Ar-N₂ mixed shielding gas. The effects of the three main process parameters,including nitrogen content in the shielding gas,arc voltage and welding speed,on the ferrite content and the microstructure of cladding metal were studied. The results showed that increasing the percentage of nitrogen in the shielding gas or arc voltage could reduce the ferrite number of cladding metal,while increasing the welding speed could increase the ferrite number of cladding metal. In the case of multi-layer multi-pass welding,the average ferrite number in cladding metal was lower than the predictions of WRC-1992 due to the influence of welding thermal cycle between layers. When the Ferit Scope based on magnetic principle was used to measure the ferrite number in the sheet metal cladding,the result would be lower than the actual ferrite number and the measurements would reduce with the decrease of cross-sectional area of the weld.