鋳鉄の焼入に関する研究（第1報）鋳鉄の焼入硬度硬化深度および焼入歪について

Abstract

In general,the hardening of cast iron has not so far been applied practically, because of its various troublesome factors,chemical compositions, microstructures and mechanical properties. Recently, Induction Surface Hardening has been used widely for steel. There are, however,few application to cast iron due to the difficulties accompaning its hardening. Therefore, the authors studied the hardening of cast iron, especially, Induction Surface Hardening to clarify these points and many phenomenas accompanying them. First, we investigated the hardness,hardened depth and strain of various cast irons. In these experiments, the higher input and the longer heating time were,the more Retained Austenite increased, subsequently, surface hardness dropped and the maximum hardness was displaced to inside layer (Fig. 1∼3). Quenching hardness was maximum at 850° in the case of ordinary quenching,but dropped in the range of high temperature, because of increased Retained Austenite (Fig. 4). Pearlite matrix is most desirable,for the combined carbon in matrix has remarkable influence upon the hardenability. As the size of graphite became smaller and more grobular, the quenching hardness of cast iron increased.From these points of view,Nodular Graphite Cast Iron treated with Mg has not only the best hardenability (Fig. 5∼8),but also the least strain (Fig. 9∼10).