| 摘要 |
<p>The outlet nozzle and bottom end of a stopper rod are preheated in a vessel used for holding molten metal. The top of the nozzle and the bottom end of the stopper rod are surrounded by a heat barrier, i.e. a thermally insulating sheath, and heat is applied inside the sheath. The heat is pref. fed up the nozzle. Pref. the vessel is a tundish, where the nozzle also forms a casting pipe, the bottom end of the pipe being immersed below the surface of molten metal in a mould or other vessel; heat is fed up the pipe while the tundish is empty. Pref. the sheath has a conical shape, and is made of a mixt. of refractory- fibres and powder with an organic binder; or a ribrous refractory; and may contain exothermic material. Heat is pref. applied via an oxyacetylene burner, and an annular gap at the top of the sheath allows the escape of gas. For example, in the continuous casting of steel, the sheath permits the rapid preheating of the outlet nozzle and bottom end of the stopper rod; the sheath is destroyed when molten steel enters the tundish.</p> |
