Tundish Lining Construction and Refractory Material Composition

The Role of the Tundish in Continuous Casting

The tundish refractory lining acts as a transition device for molten steel between the ladle and the mold.

Its main tasks include:

1. Diversion of Molten Steel: For multi-stream continuous casting machines, the tundish distributes molten steel to each mold.

2. Steady Flow: The tundish reduces the static pressure of the molten steel, maintains a stable liquid level, and ensures the smooth injection of molten steel into the mold.

3. Storage of Molten Steel: During multiple furnace continuous casting, the tundish allows the drawing speed to remain constant when replacing the ladle, facilitating continuous casting across multiple furnaces.

4. Purification of Molten Steel: Over long pouring times, the tundish helps maintain the temperature of the molten steel and promotes the rise of inclusions. This prevents the molten steel from contacting air, thereby avoiding oxygen and nitrogen absorption.

The tundish is lined with refractory materials, and generally includes the following parts:

(1) Insulation layer (10~30mm), this layer is next to the steel shell of the tundish, usually using asbestos board, insulation brick or lightweight castable. The best effect is aluminum silicate fiber felt, which has low thermal conductivity and is easy to build.

(2) Permanent Layer (100-200mm): This layer is in contact with the insulation layer and is generally made of clay brick. The overall permanent lining is typically high-alumina or mullite self-flowing castable.

(3)  Working Layer (20-50mm): This key layer is in contact with molten steel. Insulation boards or coatings are commonly used here. Insulation boards are usually made of siliceous, magnesia, or forsterite materials. Coatings include magnesia, magnesia-chromium, and magnesia-calcium, which are applied either mechanically or manually.

(4) Tundish Well Block: Inlaid at the bottom of the tundish, this component is used to install the tundish nozzle and is usually made of high-aluminum material.

(5) Bottom Material: The furnace lining material of the tundish bottom is similar to the working layer. The bottom is highly susceptible to damage from the impact of molten steel, requiring materials that offer both corrosion and wear resistance. Common materials include high-alumina bricks, dense high-alumina bricks, and aluminum-chrome bricks. Special large high-strength tar magnesia bricks are also used, with the impact area of molten steel reinforced by stony bricks or prefabricated blocks.

(6) Cover: The tundish cover aids in heat preservation and prevents splashing of molten steel. It is typically made from clay or high-alumina castable.

(7) Slag Retaining Wall (Weir): Built within the tundish refractories, this component can be a single or double wall. The weir is usually constructed from high-alumina bricks or prefabricated blocks and serves to block slag. To improve the cleanliness of the molten steel, a molten steel filter can be installed on the slag retaining wall.