| Friction stir welding(FSW) is a solid-state joining process which based on the friction welding, This new welding technique with uniqueness and superiority has been paid a great amount of attention by researchers ever since it was developed, and study of the welding performance of various materials also become one of the major fundamental researches. So far, the feasibility of FSW study has been shifted particularly from the joining of Al alloy to Cu, Ti, Mg alloys and stainless steel. The objective of this work was to study the welding performance and parameters of FSW for joining stainless steel, the material and geometrical shape of pin, and investigate tool wearmechanism in friction stir welded stainless steel.The 0Cr18Ni9 stainless steel sheet of 3mm thickness was welded by friction stir welding process. The joint microstructures can be divided into three regions, welded nugget zone(WNZ), thermal-mechanically affected zone(TMAZ) and heat affected zone(HAZ). And the microstructure in the WNZ consists of dynamic recrystallization grains, the obvious working-hard phenomenon occurs, the microhardness (HV) is higher 22% than that of basic material; the microstructure in the TMAZ has a different extent of distortion; the microstructure in the HAZ consists of incomplete dynamic recystallzation grains. The tensile strength of weld joint is highest under the condition of the stir-pin rotation speed 600r/min and the weld speed 700mm/min, which reaches 412MPa.Tool technology is the key factor in the friction stir welding process. From the material and the structure tools of stainless steel carry on a design, analyzes load of tools, and simulates temperature field of tools by FEA software DEFORM-3D in friction stir welded stainless steel.Under friction stir welding process of stainless steel, in this paper, tool wearmechanism in friction stir welded stainless steel was investigated theoretically and experimentally. Based on the experiments, tool wear mechanism in friction stir welded stainless steel can be summed up as follows: adhesion wear, oxidative wear, diffusion wear, micro-breakout, and brittleness rupture.The result of the investigation proved that the joints of stainless could be successfully carried out by FSW when optimal material and geometrical shape of pin and optimal welding parameters were chosen. The results, which were of great practicalvalue, not only provided a newly economical and reliable method for joining materials mentioned above, but also established foundation for the further study of FSW techniques.
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