Increase the service life of the work lining of the middle bag and reduce the tundish nozzle

The tundish refractory lining mainly includes thermal insulation layer, permanent layer and working layer.

(1) Insulation layer (insulation layer) (10 ~ 30mm). This layer is next to the tundish steel shell. The main function is to insulate the molten steel and reduce the temperature drop of the molten steel during the pouring process. Usually, asbestos boards, insulating bricks or lightweight castables are used. 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 plays the role of safety insulation. In the mid-1970s, the permanent layer was mainly made of clay bricks. Later, it was built with high-alumina bricks. By the end of the 1980s, castables were used for integral casting. The castables were generally high-aluminum or mullite self-flowing castables.

(3) Working layer (20～50mm). This layer is the key part in contact with molten steel. This layer of material should strive for simple equipment and convenient construction during use and construction, which can reduce labor intensity and improve labor productivity, and must have good baking adaptability. It is required that the work lining material harden quickly and do not burst during baking. It has good strength, can be baked quickly or used directly without baking. It can reduce the energy consumption of the baking package and increase the utilization rate of the middle package, extend the life cycle of the middle package and reduce the number of spare packages. The work lining material should have good adhesion to the permanent layer during construction, and it should not fall back or collapse. It should have good high-temperature performance under high-temperature conditions, not only require a high degree of refractoriness and a certain high-temperature strength, but also must have good chemical stability, to ensure that there is no secondary oxidation of molten steel under high-temperature conditions. It will pollute the molten steel and will not reduce the quality of the billet. During use, it should have good resistance to erosion and penetration of molten slag, as well as the ability to resist scouring of molten steel and slag, which is conducive to improving the service life of the work lining of the middle bag and reducing the tundish.