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Metallurgical function of tundish in steelmaking process

Release time：

2022-12-24

The tundish is a refractory container used in steelmaking and continuous casting. It first receives molten steel poured from the ladle, and then distributes it to each mold through the tundish nozzle.
Role of tundish
(1) Reduce the static pressure of molten steel, maintain a stable molten steel level in the tundish, and smoothly inject molten steel into the mold; (2) Promote the inclusion in the molten steel to float further to purify the molten steel;
(3) Divert molten steel. For the multi-stream continuous casting machine, the molten steel is distributed to each mold through the tundish;
(4) Store molten steel. The drawing speed is not reduced when replacing the ladle in the multi-furnace continuous casting, which creates conditions for the multi-furnace continuous casting. It can be seen that the tundish is mainly used for reducing pressure, stabilizing flow, removing inclusions, storing and diverting molten steel.
Metallurgical function of tundish
1、 Purification function
In order to produce high purity steel, measures such as retaining wall and dam, argon blowing and ceramic filter are adopted in the tundish, which 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 in the tundish before, during and after pouring less than 5 ℃, close to the liquidus temperature, expand the equiaxed crystal zone of the billet, and reduce the central segregation, measures such as adding small scrap steel to the tundish and injecting iron powder can be taken to adjust the temperature of molten steel.
3、 Fine adjustment of composition
The aluminum, titanium, boron and other cored wires are fed into the mold from the central hole of the tundish stopper rod to realize the fine adjustment of the microalloy composition in the steel, which not only improves the yield of easily oxidized elements, but also avoids the clogging of the nozzle.
4、 Refining function
Add double-layer slag on the molten steel surface of the tundish to absorb the floating inclusions in the steel, or change the morphology of Al ₂ O ⏴ inclusions in the tundish feeding line to prevent the nozzle from clogging.
5、 Heating function
Induction heating and plasma heating are adopted in the tundish to accurately control the pouring temperature of molten steel. The longer the molten steel stays in the tundish, the more time the inclusions will float up and the cleaner the molten steel will be. In order to increase the retention time of molten steel, the effective method is to use the tundish with large capacity and deep melting pool.
Refractory for tundish
The temperature of molten steel in the tundish is about 1470~1560 ℃, because the tundish will leave a certain thickness of residual steel after casting, and the stopper and residual steel will be frozen in the tundish when the tundish is offline. The offline tundish will be removed together with the working lining after cooling, which is scrapped after one-time service. Therefore, the requirements for the working lining of the tundish are not as high as those of the ladle.
1. Permanent lining casting material
The permanent lining of tundish usually uses aluminum-silicon castable. According to the service conditions of tundish, the castable shall have good strength, volume stability and thermal shock resistance. The tundish castables produced by Kerui Refractories have a service life of about 700~800 heats.
2. Working lining dry material
The basic dry material for tundish is composed of sintered magnesia, magnesia-calcium sand or fused magnesia, magnesia-calcium sand, medium-high temperature sintering agent and a small amount of low-temperature binder. Magnesium dry working lining has the advantages of simple construction, high baking heat efficiency, easy separation of steel slag and permanent lining, fast tundish turnover, improved molten steel quality, long service life, etc.

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