Nozzle refractories and molten steel can not react chemically
Under ideal conditions, the refractories of the nozzles do not react chemically with the molten steel. However, in fact, there is a continuous chemical reaction between the refractory material on the surface of the nozzle and the molten steel, and Al deposition occurs. In continuous casting, precipitation occurs as long as the molten steel is in direct contact with the nozzle, and as long as the surface of the nozzle is covered by the deposition, solid inclusions in the casting stream will adhere to the wall of the nozzle. NaO is generally not present in pure form in aluminum-carbon refractories. At the casting temperature, carbon oxides are used to reduce the oxides in molten steel, and CO and SiO gas are precipitated. The undissolved aluminum in the molten steel undergoes secondary oxidation and deposits on the refractory interface. Due to the diffusion of SiO and CO gas toward the depositional melting interface, the resulting Al deposit grows and features dendrite growth. The Al deposition reaction is as follows: (1) Reaction in a refractory material. (2) The total reaction at the interface between the refractory material and the molten steel is: The temperature drop of the molten steel also affects Al deposition on the surface of the nozzle. The control of the total amount of molten steel solid inclusions (ie, cleanliness) before flowing through the nozzle is an effective way to minimize blockage at the nozzle. The factors affecting the cleanliness of molten steel are as follows: (1) Argon gas is used to protect the flow of molten steel from the ladle into the tundish; (2) Precisely designed flow regulating devices are used to extend the residence time of the molten steel in the tundish so that the inclusions are adequate. Floating; (3) control the liquid level fluctuation of the molten steel in the tundish and mold; (4) using a covering agent in the tundish. Tundish A layer of tundish covering agent is difficult to have both thermal insulation and secondary oxidation of molten steel. Therefore, it is recommended that double tundish be used for the tundish. Contact with the molten steel surface is a layer of alkaline molten coating agent, its function is to prevent the secondary oxidation of molten steel, to maximize the absorption of inclusions, the upper layer of insulation cover layer. Solar Lights,Outdoor Solar Light Strip,Strips Solar Light,Led Solar Light Shenzhen Huangtai Photoelectric Co.,Ltd. , https://www.huangtailed.com