| 摘要 |
A layer or sleeve 4 or 6 of carbonaceous material such as paper, or reactive metal such as aluminium or magnesium, or some combination of these materials, is provided on the lower part 3 of stem 1 or upper or lower face of the dart head 5 of a tap hole dart 2 for a steel furnace. As steel is poured through the tap hole of the furnace the dart floats, with the stem in the tap hole, at the interface of the molten steel and the overlying slag in the furnace and gaseous material vapourizing from the paper or light metal layer on the dart at the molten steel temperature serves to force the slag away from the vortex of steel flowing through the tap hole so that slag is prevented from entering into the tap hole and casting.
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