Microstructures and Tensile Properties of 0Cr18Ni9 Steel Thin-Wall Tube Welded Joints by P-TIG Under Different Process Parameters

Pulse tungsten inert gas arc welding(P-TIG) was applied to weld 0 Cr18Ni9 steel tubes with specification of ϕ14 mm×2 mm, and the microstructure and tensile properties of joints under different base current(20-30 A), peak current(40-60 A), pulse frequency(0.3,0.5 Hz) and pulse width ratio of 50% were studied. The results show that the microstructures of the weld of joints under different process parameters were all austenite+δ ferrite, but the shape and content of the δ ferrite were significantly different; the austenite grains in the heat-affected zone were significantly coarsened. Under the pulse base current of 20 A, the peak current of 40 A and the pulse frequency of 0.3 Hz, the ferrite in the weld of the joint was vermicular with relatively high content, and the austenite grain size in the heat affected zone was small; the tensile properties of the joint was the best with yield strength of 401.38 MPa, tensile strength of 701.51 MPa and yield ratio of 0.57, and the fracture was composed of equiaxed dimples with uniform shape and small size.