Metallurgical function of the tundish furnace in the steelmaking process

The tundish is a refractory container used in continuous casting of steel, which first receives the molten steel poured from the ladle, and then distributes it by the tundish nozzle to the various crystallizers.

The role of tundish furnace

(1) Reduce the static pressure of molten steel, maintain a stable molten steel level in the tundish furnace, and smoothly inject molten steel into the crystallizer; 

(2) Promote the further uplift of inclusions in molten steel to purify the molten steel and promote the inclusions in the molten steel to float further to purify the molten steel; Shunt the molten steel.

(3) Distribution of molten steel. For multi-flow continuous casters, the steel is distributed to the individual crystallizers by means of an tundish furnace.

(4) Storage of molten steel. In the multi-furnace continuous casting replacement ladle does not reduce the pulling speed, for multi-furnace continuous casting to create conditions. It can be seen that the role of the tundish furnace is mainly decompression, flow stabilization, de-inclusion, storage and diversion of steel.

Metallurgical functions of tundish furnace

I. Purification function

In order to produce high purity steel, baffle wall with dam, argon blowing, ceramic filter and other measures 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 pouring process in the tundish furnace before, during and after the steel temperature change is less than 5 ℃, close to the liquid phase line temperature pouring, expanding the billet equiaxial crystal area, reduce the center of segregation, can be taken to the tundish furnace to add a small piece of scrap, blowing iron powder and other measures to regulate the temperature of the molten steel.

3. The composition of fine-tuning

By the tundish  plug rod center hole to the crystallizer feeding aluminum, titanium, boron and other core wire to achieve the micro-alloy composition of steel fine-tuning, not only to improve the yield of oxidizable elements, but also to avoid nozzle clogging.

4. Refining function

Add double-layer slag on the surface of tundish furnace steel water to absorb inclusions floating in the steel, or feed calcium line in the tundish furnace to change the Al₂O₃ inclusions morphology, to prevent tundish nozzle clogging.

5. Heating function

Induction heating and plasma heating are adopted in the tundish furnace to accurately control the pouring temperature of molten steel. The longer the residence time of molten steel in the tundish furnace, the more time the inclusions have to float and the cleaner the molten steel will be. In order to increase the residence time of steel, an effective way is to use a large-capacity, deep melt pool tundish.

Refractories for tundish furnace

Tundish steel temperature of about 1470 ~ 1560 ℃, because the tundish furnace in the casting to leave a certain thickness of residual steel, and down the line when the plug bar and residual steel frozen in the tundish, down the line of the tundish furnace cooled down with the removal of the work lining, belonging to a one-time service after the work lining that is scrapped, so the tundish furnace of the work lining of the requirements of is not as high as that of ladle.

1、Permanent lining castables

The permanent lining of the tundish furnace usually uses aluminum-silicon castables. According to the usage conditions of the tundish furnace, the castables should have good strength, volume stability and thermal shock resistance. The tundish castables produced have a service life of about 700-800 furnaces.

2、Working lining dry material

The tundish dry material is composed of sintered magnesium sand, magnesium calcium sand or electrofused magnesium sand, magnesium calcium sand and medium-high-temperature sintering agent and a small amount of low-temperature binding agent. Magnesium dry working lining has the advantages of easy construction, high baking thermal efficiency, easy detachment of steel slag and permanent lining, fast turnover of tundish, improved steel quality and long service life.