Influence of ZrO2 Active Flux on Arc Characteristic during Tungsten Inert Gas Welding of 309 Stainless Steel and Weld Property
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Abstract
309 stainless steel was tungsten inert gas welded with ZrO2 active flux (with mass fractions of 0,0.25%,0.50%,1.00%, respectively) and the effects of ZrO2 on the welding arc characteristc, fusion depth, and on the microstructure and property of weld were studied. The results show that when welding with ZrO2, the arc illustrated pulse characteristics. The arc voltage decreased first and then increased with increasing mass fraction of ZrO2. The fusion depth after welding with ZrO2 was more than 2 times larger than that after welding without ZrO2. The weld obtained by welding with 0.50wt%ZrO2 possessed a microstructure of austenite and few δ ferrite, and the austenite grains in some regions were equiaxed. The addition of a small amount of ZrO2 decreased hardness and yield strength in bending of the weld zone. With increasing mass fraction of ZrO2, the hardness of the weld zone decreased, the yield strength in bending decreased first and then increased, the thermal conductivity decreased and the specific heat capacity increased.
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