Abstract
The effect of inoculants in Mg-treated iron was clarified by means of microstructure-test on the boundary zone between inoculants and molten iron. The action of inoculants only or that of inoculants plus Mg alloy, each of them being set at the bottom of shell-mould, was also investigated in both conditions of bottom-pour and lip-pour. The results obtained were as follows: (1) The local concentration gradient of Si is set up due to the incomplete solution and diffusion in process of the reaction of Si with molten iron, thereby producing nuclei of graphite and SiC from super-saturated molten iron. The nuclei of SiC decompose easily as the decrease of the concentration gradient of Si in iron proceeds. (2) The effect of inoculants or inoculants plus Mg alloy in lip-pour of molten iron is superior to that in bottom-pour. The effect of the size is found to be best in moderate size of both the inoculants and the Mg alloy. (3) The inoculating effect of Si in Mg alloy containing Si is inferior to that of Si mechanically placed together with Mg-alloy. In the former case of the addition of Mg alloy containing Si, the rate of local concentration gradient of Si in molten iron decreases, and the inoculation becomes less effective.
