The nozzle is an important channel connecting the tundish and the crystallizer. It is called the throat fortress of continuous casting. It has the function of linking the past and the future, and is an important part of the clean steel smelting process. The outlet of the submerged nozzle is immersed in the molten steel in the mold, which prevents the secondary oxidation of the molten steel, controls the flow speed of the molten steel when it enters the mold, is beneficial to the floating of inclusions in the molten steel, and can effectively prevent curling The occurrence of slag phenomenon, etc., ensures the stable operation of the continuous casting process. Submerged nozzles must have the following properties:
(1) Good thermal shock stability;
(2) Strong corrosion resistance to molten steel and slag;
(3) It is not easy to react with the inclusions in the molten steel, so as to avoid nodulation and blockage of the nozzle.
Submerged nozzle material
The material and structure of the submerged nozzle have a great influence on the flow of molten steel in the mold and tundish, and are directly related to the quality of steel products. The smelting method is different, and the material of the submerged nozzle is different. At present, the main materials of the nozzle are fused silica, aluminum zirconium carbon, aluminum carbon and so on. The structure of the submerged nozzles used is different for different types of slabs. Straight cylindrical submerged nozzles are mainly used for pouring billets, rectangular billets or small slabs, and double-sided pass submerged nozzles are mainly used for casting blooms. , slab, and the submerged nozzle of the upper pass type is mainly used for the stainless steel pouring process.
The outlet shape of the nozzle determines the impact depth of molten steel flowing into the crystallizer. In order to meet the needs of continuous casting of high-speed thin slabs, a dissipative nozzle with four side holes has been developed. Its advantage is that it can reduce the flow of molten steel into the crystallizer. The impact depth of the device is beneficial to the floating of inclusions in the molten steel, and to a certain extent alleviates the problem of nozzle blockage. The traditional straight-chamber nozzle has been improved into a stepped ring-shaped inner cavity nozzle, that is, a double-ring stepped nozzle. The inner cavity of this structure also relieves the adhesion of inclusions in the molten steel and reduces the occurrence of nozzle blockage. From the material point of view of the nozzle, focus on the development of non-metal oxide materials such as ZrB2 and BN, ZrO-CaO-C materials, low-carbon materials (carbon <5%), silicon-free Al2O3-C materials, and carbon-free and silicon-free materials. Shuikou.