Masazô Okamoto and Renpei Yoda
The principal factors are (i) the kind of inoculants, (ii) the size of inoculants and the addition-method, (iii) the time and the temperature at inoculation, and (iv) the relation between the temperature of Mg-treatment and that of inoculation. The factors (i) and (ii) were already described in the previous reports. The object of the present paper is to explain the influence of time and temperature at both Si-inoculation and Mg-treatment on the inoculation by measuring the rate of spherulitic graphitization of ironc. The effects of the abovementioned principal factors are summarized as follows : (1) Inoculants like Ca-Si are inadequate for the inoculation against strongly deoxidized iron such as Mg-treated one. (2) The inoculating effect is found to be best when the size of inoculants is moderate and the addition-method is appropriate to attain uniform action of the inoculants throughout the molten iron. (3) The rate of spherulitic graphitization of iron inoculated with Si after Mg-treatment is inferior to that of iron inoculated with Si before Mg-treatment. The phenomenon is attributed to the fact that Si in molten iron inoculated after Mg-treatment is hardly consumed for the deoxidation of molten iron and the inoculant becomes more effective. (4) Mg-treatment at high temperature followed by Si-inoculation at low temperature results in good inoculating effect of Si against Mg-treated iron. It signifies that high temperature of Mg-treatment causes the decrease of the amount of residual Mg in molten iron,and low temperature of Si-inoculation brings about steep concentration gradient of local hypereutectic domains in such a melt.
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