Electro-magnetic Non-destructive Testing of Friction Welding Defects

This paper introduces a new method of testing friction welding defects of high-speed steel and 45 steel friction welding bits-initial incremental permeability method.This paper also introduces the principle of SGF-Ⅱ W type digital automatic separator of material quality for steel and iron which is developed on the gasis of initial incremental permeability method and the research result of testing friction welding defects.