Study On1Cr18Ni9Ti Austenitic Stainless Steel Of Ultra-narrow Gap Welding With Constricted Arc By Ultra-fine Granular Flux

Austenitic stainless steels are widely used in nuclear power equipment, pressure vessel,petrochemical and other fields due to its excellent mechanical and corrosion-resistanceproperties.However, austenitic stainless steels conventional welded joints vulnerable tointergranular corrosion because of chromium depletion at grain boundaries caused byexcessive heat input. On account of Ultra-narrow Gap Welding (UNGW) have lower heatinput, deformation and higher efficency than conventional method,thus it has particularlyadvantage for improving the mechanical and corrosion-resistance properties in austeniticstainless steel thick wall workpieces.This paper adopt Ultra-narrow Gap Welding with Constricted Arc by Ultra-fine GranularFlux on1Cr18Ni9Ti austenitic stainless steels.Study on influence of welding parameters onweld formation,microstructure,mechanical and intergranular corrosion-resistance properties ofUNGW weld joint.The results shows that when the ratio of weld length and width is1.34andheat input is1.75KJ/mm,there are no pear-shaped bead crack in UNGW weld,moreover,theheight of single bead could get to11.5mm.Define the high-quality match relationship of weldvoltage and current range in26V-32V and190A-320A,under the condition of otherparameters are fixed.As the increase of voltage,the formation of weld shows “Lack of fusionon sidewalls”,”Good fusion”and “Arc climbing up”respectively. The results of microstructureand mechanical test show under the same heat input, filling weld and cover weld are made ofcoarse austenite columnar grain which contain small quantity of lath ferrite inside,and coverweld has larger size than filling weld;backing weld is made of austenite equiaxed grain whichas well contain small quantity of lath ferrite inside. The tensile strength, yield strength andelongation ratio of welding joint is higher than base metal and the impact energy is lower thanbase metal. Besides, intergranular corrosion rate of welding joint is0.417g/(m2.h),obviouslylower than the rate of base metal.Overall, under the condition of parameters are fixed,1Cr18Ni9Ti austenitic stainlesssteels can be able to obtain excellent weld formation,mechanical and corrosion-resistanceproperties adopt Ultra-narrow Gap Welding with Constricted Arc by Ultra-fine GranularFlux.Meanwhile,this study will provide theoretical and experimental foundation for thesupplement of welding theoretical,optimation of narrow gap welding technology andrealization of industrial application of UNGW.