Abstract
To select the induction hardening steels, the author studied the effect of the nonmetallic inclusions on the sensitivity to induction-hardening crack.
Namely, making use of the properties of the sulphide inclusions that of shape and distribution were changed remarkably by deoxidizing method in the steel melting, the author had prepared many crack test specimens that contained the abovementioned inclusions and various oxides, and examined the crack test by repeated quenching method on the induction hardening.
The experimental results are summarized as follows:
(1) The effect of the finely dispersed silicates, alumina and globular or polygonal sulphides in the cast steels on the crack sensitivity was not clear.
(2) On the contrary, the eutectic type sulphides in the primary grain boundaries gave a distinct effect on the crack sensitivity.
Namely, about 0·1% (area ratio) or more of the entectic sulphides increased the crack sensitivity with the 0·72%C cast steel.
