Joint microstructures, mechanical properties and fatigue behavior of ferritic stainless steel SUS430 welds with different filler metals were investigated. Two filler metals with different chemical compositions, Filler I and II, had been used for the MIG butt welding of SUS430. Filler I showed coarser grains in the microstructure than Filler II including Al and Ti. In both welded joints, the hardness of heat affected zone (HAZ) was the highest due to the formation of hard needle-like martensite. The welding heat input of Filler I welded joint was higher than that of Filler II. Consequently, martensite content of Filler I was more numerous and bigger than the Filler II. Fully reversed axial fatigue tests had been performed using smooth specimens of welded joints and base-metal specimens at ambient temperature in laboratory air. In both welded joints, fatigue fracture took place at base metal region due to the higher hardness in weld metals and HAZ regions than the base metal.
