What are the prominent problems with the tundish currently used in China, especially in square billet continuous casting machines

 　　At present, there are many problems with the tundish used in China, especially the tundish used in square billet continuous casting machines. Specific manifestations include:

　　(1) The shape of the inner cavity of the tundish is unreasonable. Due to the unreasonable shape of the inner cavity, the flow of molten steel in the tundish is unreasonable and the residence time is short, which cannot purify the molten steel. The distance between the landing point of the large injection flow entering the tundish and the tundish water outlet is short, or the distance difference between the two water outlets is too large; The small volume at the landing point of the large ladle results in severe steel slag mixing and lining erosion, affecting the service life of the tundish and polluting the molten steel.

　　(2) The small capacity of the tundish and shallow depth of the molten pool are not suitable for high-speed casting machines. The retention time of molten steel in the tundish is short, making it difficult to purify the molten steel and remove impurities; Difficulty in maintaining constant pouring speed during package replacement; During pouring, the steel slag inside the tundish is severely stirred, making it difficult for inclusions to float and easily enter the mold, especially during ladle replacement.

　　(3) Improper design of the position of the tundish water outlet, especially when the water outlets on both sides are too close to the two sides, can easily cause uneven pouring of the two side water outlets.

　　(4) The control device for the tundish water inlet is too thin and unreliable, making it difficult to accurately control the steel flow rate, making it difficult to stabilize the crystallizer liquid level and often causing accidents of losing control.

　　(5) The large deformation of the tundish and issues with design and manufacturing accuracy have resulted in insufficient alignment accuracy with multiple flow ports.

　　(6) The lifting device of the tundish is not flexible, and most cannot lift, which brings difficulties to the continuous casting process and causes many defects in the casting billet.

　　(7) Improper selection of distance from the bottom of the tundish to the upper mouth of the crystallizer. Most of the distances are too high, which makes it difficult to align the nozzle and also makes the nozzle too long, resulting in an increase in the consumption of refractory materials per ton of steel nozzle.

　　(8) Insufficient emphasis on the quick change technology of the immersion nozzle.

　　The above tundish is barely usable under low casting speed conditions and is not suitable for the current requirements of high casting speed continuous casting. Modern tundish should not only adapt to the conditions of constant casting speed under high casting speed, high steel volume and strength, and intense stirring inside the tundish, but also play a role in purifying steel liquid and removing inclusions. The specific measures adopted include:

　　(1) Optimize the shape of the inner cavity of the tundish to ensure a reasonable flow of molten steel within the tundish while adapting to high casting speeds, expand the volume of the large ladle at the tundish landing point, and optimize the distance between the large ladle landing point and each water outlet; (2) Adopting a large capacity deep melting pool tundish; (3) Prevent deformation of the tundish shell; (4) Adopting a solid and reliable control device for the tundish nozzle; (5) Adopting a reliable tundish lifting device under load conditions; (6) Optimize the distance between the tundish and the upper mouth of the crystallizer.