Tundish nozzles

Normally, zircon sand is readily available as a by-product of mtile and ilmenite mining at ca 150 per metric ton. However, zircon and baddeleyite are obtained as by-products of their operations, and therefore, the supply is limited by the demand for other minerals. In 1974, when a use for zircon in tundish nozzles developed in the Japanese steel industry, a resulting surge in demand and stockpiling raised zircon prices to 500/t. Worldwide production by country is given in Reference 80. 

Stupid. An extrusion machine in which clay is forced through the die by of a piston such machines are now rare. Submerged Entry Nozzle. A refractory component acting as both tundish nozzle... 

A primary and a secondary water circuit is used to cool the bar before it is cut (at 13 meters). In the case of an emergency (if the cooling system does not work, the mold overflows, the tundish or ladles break), the casters must try to make use of emergency furrows to collect the steel and slag in emergency containers and must close the tundish nozzles using copper stoppers. 

In the 1990s, trials of doloma-based refractories in the continuous casting of steel were started. It was felt that the high lime content (57%) of the doloma refractory would make it very effective in the prevention of alumina buildup during the continuous casting of aluminum killed carbon and stainless steels. Doloma graphite SENs and ceramic bonded doloma tundish nozzles have both been developed. 

Doloma Tundish Nozzle. When aluminum killed steels are cast, the upper tundish nozzle is prone to clogging. Alumina inclusions in the molten steel deposit on the nozzle bore and restrict steel flow from the tundish. At this point the nozzle can be physically reamed open with a rod however, this practice has an adverse effect on the steel quality, so generally the tundish is replaced by a new one. 

Argon purging of the upper tundish nozzle is common when aluminum killed steels are cast. This practice is effective in reducing the rate of alumina buildup on the nozzle bore, but it does not prevent it. Clogging of the upper nozzle limits tundish life in some steel plants. 

Doloma-based upper tundish nozzles, without argon purging, were developed in an effort to prevent clogging due to alumina buildup. The properties of the doloma nozzle are shown in Table 8. The doloma nozzles are based on... 

Doloma-based refractories have been applied to the continuous caster to prevent alumina clogging when casting aluminum killed steel grades. Tundish nozzles based on doloma have been used at BOF shops that cast a variety of aluminum killed steel grades. It was found that the sulfur content of the steel was critical with maintaining the clogging resistance of the doloma nozzles. 

The doloma nozzles have prevented alumina buildup and eliminated the use of argon in the tundish nozzle. 

Tundish. A rectangular trough lined with fireclay refractories and with one or more refractory nozzles in its base. Tundishes are sometimes used between the ladle and the ingot moulds in the teeming of steel. 

Results in practice have confirmed this theoretical potential of doloma to prevent clogging of nozzles in the tundish. 

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