It has been well known that mechanical properties of steels are improved by gain refinement, smaller cementite particle and finely dispersing cementite particle, It is enabled by super rapid induction tempering the the smaller cementite particle and the finely dispersing cementite particle. In this study, mechanical properties of induction quenching and tempering carbon steel using super rapid induction heating system were investigated. Dtail, the effect of quenching time on tensile properties is examined. The quenching time was changed in four steps of 0.44 s (1163 K), 10 s (1233 K) +10 s (1153 K), 20 s (1273 K) and 20 s (1433 K). As a result, it was found that the tensile strength of QT steel indicated an increase tendency with hardness. The yield strength was in proportion to a square root of grain size. However, the ductility improvement effected by super rapid induction quenching was not found, reduction of area did not depend on grain size.
