鍛造用鋼塊のボトム部介在物について

概要

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The non-metallic inclusions in the bottom portion of forging ingots can be devided into two types, internal and subsurface.At present, the frequency of defects due to the both types is kept in a very low level by several improvements based upon the investigations in Shibukawa Plant, Daido. This paper describes the following results obtained in the last several years.1) The accumulation of the internal non-metallic inclusions in the ingot bottom is attributable to showering phenomenon immediately after the teeming.i) The addition of low exothermic powder causes a sudden thermal extraction and mechanical shock to generate or to promote the showering phenomenon.ii) The use of specific insulation powder is free from the sudden thermal extraction and mechanical shock, therefore, it has a favorable effect on reducing inclusions.2) The subsurface non-metallic inclusion in the ingot bottom is caused by the entrapment of teeming powder. The reduction of the inclusion is achieved mainly by the control of pouring rate at the beginning of teeming and the use of a special flux only for bottom portion of the ingot.
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