1Hitachi Central Laboratory, Hitachi, Ltd., Tokyo
By the previous thermodynamical study, it has been shown that Ge might be ideal as the refining reagent for the vacuum melting of Fe, Ni and their alloys, and that Ge might effectively decrease the dissolving gases in the melt without leaving non-metallic inclusions within the ingot. In the present study the effect of Ge additions on the dissolving gases and the distribution of non-metallic inclusions were investigated experimentally , in the wide range of the Fe-Ni binary system vacuum melted in the scale of laboratory and semi-industry, by means of the vacuum fusion gas analysis and the electron microscope. The results obtained are summarized as follows:—
(1) The addition of Ge astonishingly decreases the dissolving gases, such as oxygen and nitrogen. The oxygen content is rapidly decreased from a few hundreds ppm to 10 ∼ 20 ppm by the addition of only a few per cent Ge. The refining ability of Ge is more effective in the melting on the industrial scale in a poorer vacuum condition. For example, in the large ingot of 20 kg, the oxygen content of the ingot with Ge is about 10 ppm, that without Ge being 200 ppm.
(2) It is found to have close correlation between the dissolving oxygen content and the amount of non-metallic inclusions, i.e., as the former becomes lower, the latter also decreases. The diameter of the most of the non-metallic inclusions is found to be about 1 μ .
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