Abstract
By investigating the sand adhering phenomena on the foundry products and the laboratory specimens, the chief causes were analysed and therefrom the factors of its prevention were determined. “Burn-on”, the phenomenon which is generally called for “Hard adherence of sand or core”, in Japanese foundries can be cl ssif ed into two types; one is the adhesion of fused and sintered sand on the casting surface, and the other is caused by the penetration of metal into the mould surface. The adhesion phenomena mostly found in foundries belong to the latter type, which was chiefly investigated in this work. Macroscopic and microscopic examinations show that the slag formation between cast metal and the mould surface is an effective factor of preventing penetration, provided that the casting temperature, the solidifying time, the static pressure of metal, etc., are not extremely severe. The oxidation of the interface between the metal surface and the mould is violent, and the penetrated metals are much decarbonized. Some examples of selective oxidation of Mn and Fe are listed-up by analysing the slag layer. For the static pressure of molten metal, the result of the laboratory test and calculation show that the metal penetration is very remarkable when the blacking, slag formation and the back pressure do not exist. From the thermochemical point of veiw concerning the process of penetration, it is concluded that the fundamental natures of moulding sand, that is, the high purity, good refractoriness and the round shape are the most important factors of preventing penetration. In addition, required factors of preventing penetration in the foundry practice are summarized.
