Research On Laser Welding For Ferritic Stainless Steel

It has obviously economy and social benefit to replace austenitic stainless steel by ferritic stainless steel which has less nickel. But when be heated, the ferritic stainless steel grain would quickly grow up. The traditional welding method could cause welding joint grain serious coarsening, which lead to serious embrittlement and intergranular corrosion problems. Therefore it is necessary to use new welding methods to solve the problem above to guarantee the stability of its use.In this research, the effect of laser welding process parameters on welding forming is studied. Analysed the transform of ferritic stainless steel microstructure and mechanical properties. Discussed the different factors in the role of the mechanism of laser welding process. Comparatively analysed the different influence on welding by adding several kind of welding wire, and improved the welding joint mechanics performance.Study results indicated that: laser power and welding speed were important factors to decide its thermal state, therefore, decided the weld microstructure. On keyhole welding, large amount of small equiaxial grain could obtained in center part of weld on lower laser power. Defocusing amount depended the shape of the pool, the distance between protective gas and workpiece also affected the welding quality. Air vent existed in SUS430 ferritic stainless steel laser welding butt weld, and a lot of martensite existed on weld grain boundary as well as in grain. The hardness increased with laser power increased, and get highest value on center part of the weld. With NiCr3 welding wire, SUS430 failed in base metal during tensile test, while with 308L failed in HAZ when with higher welding speed(4mm/s) and higher wire feeding speed(10mm/s).The results showed that under the appropriate parameter could 308L replace NiCr3 as welding wire in SUS430 ferritic stainless steel.