와전류법을 이용한 크랭크샤프트 크랙 검사

Material in automotive industry has changed to reduce cost of manufacturing. In that aspect, micro-alloyed steel used for material of crankshaft has substituted quench and tempered steel to have equal quality and result in a drop in cost. The quench and tempered steel is usually treated by heating. But micro-alloyed steel which just add alloying elemnts such as vanadium, boron and so on is applied without overall heat treatment. The surface of crankshaft made with micro-alloyed steel is locally processed by induction hardening. The process can cause a crack on grinded surfaces because of residual tensile stress. Therefore crack inspection is required. Magnetic testing is used manually in line. Magnetic testing is subjective to detect defects. Eddy current(EC) testing use electronic signal automatically and is objective to detect cracks. In this paper, it is estimated that eddy current method is valid.