Microstructure and Mechanical Properties of GTAW Joint of High Nitrogen Austenitic Stainless Steel Medium Thick Plates for Medical Devices

Gas tungsten arc welding (GTAW) was used to weld 7 mm thick high nitrogen stainless steel.Microstructure and mechanical properties of the welded joint were studied.The results show that microstructure of weld zone and heat affected zone both was austenite and δ-ferrite.When 2% N2 was added to the shielding gas,tensile strength of the weld zone was remarkably increased to 865 MPa,close to that of the parent metal (875 MPa),and toughness was also increased.At -40 ℃,impact absorbed energy of the weld zone reached 70 J and that of the heat affected zone was about 60 J showing that the whole joint had good low temperature toughness.