Tundish is a refractory container used in steelmaking continuous casting. Molten steel is first poured from ladle and then distributed to each mold by the tundish nozzle.
The role of the tundish
(1) Reduce the static pressure of molten steel, maintain the stable liquid level of molten steel in tundish, and steadily inject molten steel into mold; (2) promote the inclusions in the molten steel to float further to purify the molten steel;
(3) split molten steel. For multi-flow continuous caster, molten steel is distributed to each mold through tundish.
(4) Storage of molten steel. When the ladle is replaced by multi-furnace continuous pouring, the drawing speed is not reduced to create conditions for multi-furnace continuous pouring. It can be seen that the main functions of tundish are decompression, flow stabilization, removal of inclusions, storage and diversion of molten steel.
The metallurgical function of tundish
1. Purification function
In order to produce high purity steel, using retaining wall dam, argon blowing, ceramic filter and other measures in tundish can greatly reduce the content of non-metallic inclusions in steel.
2. Temperature regulation function
In order to make the temperature change of molten steel before, during and after the tundish less than 5℃ and close to the liquidus temperature, expand the equiaxed crystal zone of the casting billet and reduce center segregation, measures such as adding scrap steel to the tundish and spraying iron powder can be taken to adjust the temperature of molten steel.
3. Tomposition fine-tuning
Through the center hole of the tundish plug rod, core-wires such as aluminum, titanium and boron are fed into the mold to realize the fine-tuning of the microalloy composition in the steel, which not only improves the recovery rate of easily oxidized elements, but also avoids the blockage of the water nozzle.
4.Fefining function
To absorb the inclusions floating in the steel, a double layer slag was added to the water surface of the intermediate shell, or a calcium line was fed in the intermediate shell to change the Al₂O₃ inclusions to prevent the spout from blocking.
5. Heating function
Induction heating and plasma heating are adopted in tundish to accurately control the pouring temperature of molten steel. The longer the molten steel stays in the tundish, the more time the inclusions have to rise and the cleaner the molten steel will be. In order to increase the residence time of molten steel, the tundish with large capacity and deep melting pool is an effective way.
Refractory material for middle wrap
The molten steel temperature in the tundish is about 1470 ~ 1560℃, because the tundish needs to leave a certain thickness of spare steel after casting, while the stopper rod and spare steel are frozen in the tundish when the tundish is down, and the tundish is removed together with the lining after cooling, and the lining will be discarded after one-time service. Therefore, the requirement on the lining of the tundish is not as high as that of the ladle.
1. Permanent lining casting material
The permanent lining of the tundish usually uses aluminum-silicon castable, which should have good strength, volume stability and thermal shock resistance according to the service conditions of the tundish. The tundish castable produced by Corina Materials has a service cycle life of about 700 ~ 800 furnaces.
2. Work lining dry material
Tundish alkaline dry material is composed of sintered magnesia, magnesia calcium sand or fused magnesia, magnesia calcium sand and medium high temperature sintering agent, a small amount of low temperature binder. Magnesium dry lining has the advantages of simple construction, high baking thermal efficiency, easy separation of steel slag and permanent lining, quick turnover of tundish, improved quality of molten steel, long service life and so on.
