A reliable system to transfer the molten metal is needed in continuous casting in order to produce a quality surface on the continuous-cast slab and finished rolled product and obtain low concentrations of gases (nitrogen, oxygen, and hydrogen) in the steel. The conduit for the metal on the ladle-tundish and tundish-mold sections should satisfy the following requirements:-there must be a tight joint between the refractory tube and the ladle nozzle and between the submersible nozzle and the tundish nozzle, and argon must be supplied to those joints; -the materials of the tube and the submersible nozzle must be highly durable (especially in the slag zone);-it should be simple to install and replace the protective tube and the submersible nozzle (by means of a manipulator and a fitting).Before 1998, the company Severstal' used two types of conduits for the metal in continuous casting: a protective fireclay-graphite tube in a suitable fitting and submersible nozzles -for casting stainless steels; quartz tubes and submersible nozzles -for casting the other grades of steel. The fireclay-graphite tube was affixed to the ladle before the beginning of casting, and the joint between the tube and the nozzle was sealed with mortar and asbestos cord. The same method was used to install the submersible corundum-graphite nozzles on the tundish. Among the shortcomings of this method were the fact that the seal was not always tight (particularly when oxygen was used to open up the slide gate in the ladle) and the heaviness of the protective tubes and submersible nozzles. In the case of the use of tubes and submersible nozzles made of quartz, the joint was poorly formed and did not last long.
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