Abstract
Some chemical and physical changes of the spherulitic graphite iron treated at 1400° with 0.5∼10% Mg in the form of pure Mg were investigated using specimens cast in dry sand mould 14 mm in diameter after being kept for 30 sec from the instant of the Mg-addition.
The abrupt change in some chemical and physical properties in the iron appeared at 5∼6% Mg-additions; though the amount of the free cementite in the matrix of iron increased gradually at 1∼5% Mg-additions, it suddenly began to decrease from 6% Mg-addition. The hardness of the iron increased at 1∼5% Mg-additions and then decreased from 6% Mg-addition. The number and the size of the spherulitic graphite in the iron decreased gradually at 1∼5% Mg-additions and then, from 5.5% Mg-addition, both of them increased, but the latter again decreased remarkably from 7% Mg-addition. Concerning the residual carbon and sulphur in the iron, the former decreased gradually at 1∼5% Mg-additions, and increased from 6% Mg-addition, but the latter decreased gradually at 1∼6% Mg-additions and then increased from 7% Mg-addition. The residual total magnesium showed the linear and gradual increase at 0.5∼5% Mg-additions, next, sharp increase at 5∼6% Mg-additions and then again the linear and gradual increase from 6% Mg-addition. The relative relation of both amounts of alloyed magnesium and non-metallic inclusions such as MgO, MgS in irons was discussed, and it was confirmed that the above phenomena can be explained from the author’s point of view on the above relation.
