Abstract: Based on the explicit finite element software(ABAQUS/Explicit),a three dimensional model of inertia friction welding GH4169 supperalloy ring workpiece was established for the coupled thermo-mechanical analysis.The effect of mass scaling on the moment of inertia was studied.The correlation between the mass scaling and the minification of moment of inertia was preliminarily evaluated.Moreover,the temperature field of the whole welding process was well investigated.The result shows that the temperature of the welding interface center increases rapidly to 1 200℃ in the first 0.5 s,after that,the temperature mentains at a quasi-stable platform until the speed of the flywheel descends evidently.The visco-plastic metal is extruded out from the welding interface while the interface temperature tends to be uniform.