Development Of Refractory Lining

The refractory lining of the tundish mainly includes an insulation layer, a permanent layer, and a working layer.
(1) Insulation layer (insulation layer) (10-30mm). This layer is adjacent to the steel shell of the intermediate ladle, and its main function is to insulate the molten steel and reduce the temperature drop during the pouring process. It is usually made of asbestos board, insulation bricks, or lightweight casting materials. The best effect is aluminum silicate fiber felt, which has low thermal conductivity and is easy to build.
(2) Permanent layer (100-200mm), which is in contact with the insulation layer and mainly serves as a safety insulation layer. In the mid-1970s, the permanent layer was mainly built with clay bricks, and later with high alumina bricks. By the late 1980s, castable materials were used for overall pouring, usually high alumina or mullite self flowing castable materials.
(3) Working layer (20-50mm). This layer is in contact with molten steel and is a critical part. This layer of material should strive for simple equipment, convenient construction, reduced labor intensity, improved labor productivity, and good baking adaptability during use and construction. It is required that the working lining material hardens quickly, does not burst, has good strength, can be quickly baked or directly put into use without baking, reduces baking energy consumption, increases the utilization rate of the intermediate ladle, and prolongs the service life of the intermediate ladle, Reduce the number of spare packages. The working lining material should have good adhesion with the permanent layer during construction, without falling back or collapsing. It shall have good high temperature performance under high temperature service conditions. It is not only required to have high refractoriness and certain high temperature strength, but also must have good chemical stability to ensure that there will be no secondary oxidation of molten steel under high temperature conditions, no pollution to molten steel, and no reduction in the quality of steel billets. During use, it should have good resistance to slag erosion and penetration, as well as the ability to resist steel and slag erosion, which is beneficial for improving the service life of the working lining of the intermediate ladle and reducing the intermediate ladle
Consume refractory materials and reduce the pollution of refractory materials on molten steel. The working lining should have a certain metallurgical function, which can react with inclusions in the steel liquid, absorb N, S, P, and non-metallic oxide inclusions in the steel liquid, and improve the quality of the steel liquid. The working lining should have good thermal shock resistance and good volume stability, and not explode when in contact with molten steel, ensuring that the tundish has good integrity. The working lining of the tundish should also have low thermal conductivity and good insulation performance, which can reduce the heat loss of the tundish and maintain the stability of the molten steel temperature in the tundish. The working lining after use should be easy to unpack, and the working layer and permanent layer should be easily separated, which can reduce the damage of the refractory material of the working lining to the permanent lining of the intermediate package and help extend the service life of the intermediate package.
In the early days of the working layer, aluminum refractory bricks were used. Later, in order to maintain the temperature change of the steel liquid in the tundish during pouring not exceeding 15 ℃, the working layer began to use insulation board working lining. Later, the insulation board was replaced by fire-resistant coating materials and fire-resistant spraying coatings with the same function. With the development of multi furnace continuous casting technology and rapid nozzle replacement technology, the latest dry vibration materials began to replace fire-resistant spraying coatings with significant advantages. The refractory materials used for the working layer of the tundish have gone through the development process of refractory clay bricks (permanent layer refers to the working layer), insulation boards, spray coatings (plastering), and the latest dry vibration materials (i.e. dry working lining). The insulation board is generally made of silica, magnesium and magnesium olivine; Other forms of refractory materials are mostly magnesium, magnesium chromium, and magnesium calcium.
(4) The bottom material of the bag is basically equivalent to the working layer. The working layer at the bottom of the tundish is easily damaged by the impact of molten steel, and requires corrosion resistance and wear resistance. The impact area of molten steel is often reinforced with prefabricated blocks made of corundum and magnesium castables. Some companies also use waste skateboard bricks and magnesium carbon bricks for reinforcement in the castables.