In an ideal state, the nozzle refractory and molten steel do not react chemically, but in fact, the chemical reaction between the refractory material on the nozzle surface and the molten steel continues to occur, resulting in A1 deposition. During continuous casting, only the molten steel and the nozzle will directly contact the precipitation, as long as The surface of the nozzle is covered with sediment, which will cause the solid fine debris in the casting to adhere to the wall of the nozzle.
NaO generally does not exist in pure state in aluminum-carbon refractory materials. At the casting temperature, the oxides in molten steel are reduced by carbothermal, and CO and SiO gases are precipitated. The undissolved aluminum in molten steel undergoes secondary oxidation at the melting interface of the refractory material. Induced deposition, due to the diffusion of SiO and CO gas to the deposition melt interface, the generated A1 deposit grows, which is characterized by a dendrite structure. The A1 deposition reaction includes: reaction in the refractory; at the interface between the refractory and the molten steel The total reaction: the molten steel temperature drops also affects the A1 deposit on the nozzle surface.
Controlling the total amount of molten steel inclusions (ie, cleanliness) before flowing through the nozzle is an effective way to minimize the clogging of the nozzle, and the factors affecting the cleanliness of the molten steel: protect the steel flowing from the ladle into the tundish with argon gas Water flow; adopts a precision-designed flow adjustment device to extend the residence time of molten steel in the tundish, so that the inclusions can fully float; control the fluctuation of the molten steel surface in the tundish and crystallizer; the tundish uses a covering agent, the tundish covering agent layer It is difficult for tundish covering agent to have two functions of heat insulation and prevention of molten steel secondary oxidation at the same time, so it is recommended to use a double-layer covering agent for tundish. The alkaline molten covering agent layer is in contact with the molten steel surface, and its function is waterproof molten steel dioxide In order to absorb the inclusions to the maximum, the upper layer adopts a heat-insulating covering agent layer.
