Study On 1Cr18Ni9Ti Austenitic Stainless Steel Of Ultra-narrow Gap Welding With Constricted Pulsed Arc By Fine Granular Flux

Austenitic stainless steels have excellent mechanical properties and good corrosion resistance, so it is widely used in the many industries. However, austenitic stainless steels welded joints often occurs intergranular corrosion when using conventional welding methods, especially with a large heat input. This phenomenon is due to the less Chromium at the Austenitic grain boundaries, which seriously affects the performance. The ultra-narrow gap welding method with pulsed arc has low heat input and very narrow joint gap, which has a unique advantage in austenitic stainless steel welding.This paper adopts Ultra-narrow Gap Welding with Constricted Pulsed Arc by fine Granular flux on 1Cr18Ni9 Ti austenitic stainless steels. Analysis the joint cross-section morphology respectively with different welding current and obtains a reasonable matching range about 24-34 V and 140-300 A. The forming of welds are as follows: “bad side wall fusion”, “good weld” and “undercut” as the arc voltage increases; There is no obvious impact on the macro-morphology joints when changing the pulse frequency, no matter how to change the pulse frequency, weld always appears a convex shape; The microstructure is as follows: white austenite grains which contains black lath ferrite inside. With different pulse frequency in welded joint, the microstructure of backing welding center is equiaxed and the filling and capping welding are columnar grain; Researches the influence of microstructure by changing the heat input and pulse frequency, the results shows: with the increase of heat input, no obvious grain coarsening phenomenon can be found; No obvious grain refining can be found in the weld center and the both sides of bond line with different pulse frequency; The study on mechanical properties shows: the average yield and tensile strength are higher than the standard value and the joint has a high elongation. However, the reduction of section area is less than the standard value. No crack and breakage can be found in the bending test. The impact energy is lower than the standard; Tensile and impact fracture contains various equiaxed dimples. Hardness test shows: backing welding hardness is lowest, the hardness of weld zone and base metal are similar. The corrosion rate is lower than the base metal.