Кирпич с насадкой для промковша

The tundish-sizing nozzle brick is one of the important refractory materials in the continuous casting process. Its function is to control the flow and velocity of molten steel from the tundish to the crystallizer to ensure the stability and quality of molten steel pouring. The sizing nozzle plays a vital role in the steelmaking continuous casting process with its high refractory resistance, устойчивость к коррозии, and good flow control performance.

The function of sizing nozzle brick

The sizing nozzle is one of the refractory materials for continuous casting of small square billets, which plays the role of controlling the flow rate of molten steel. The molten steel flows into the crystallizer through the sizing nozzle at a uniform and stable speed, which is a necessary condition for ensuring normal continuous casting. As a flow control element, the sizing nozzle should have good anti-scouring and anti-erosion capabilities. The inner diameter cannot expand too fast during use. Once the diameter expansion size of the sizing nozzle exceeds the range allowed by the crystallizer pulling speed, it means that the sizing nozzle has been severely damaged and cannot be used anymore and the casting is stopped. The diameter expansion of the sizing nozzle has become a bottleneck problem in the research on improving the life of the tundish.

Zirconia sizing nozzle brick

Zirconia has good thermal stability, низкая теплопроводность, and stable chemical properties. It has good stability to most acids, щелочи, alkali melts, glass melts, and molten metals. Поэтому, zirconia is an ideal material for high-temperature insulation and structural materials. As early as the 1970s, it was used to melt glass and smelt steel. In the early stage of continuous casting, due to the short continuous casting time, ordinary zirconium sizing nozzle products made of zircon and zirconium oxide composite can meet production needs, with a zirconium oxide content of 72%-85%; with the development of continuous casting technology, the continuous casting time exceeds 500 минуты. Due to the reaction and decomposition of zircon with certain metal oxides in molten steel and slag, the ordinary sizing nozzle will expand, crack, and peel off. The zirconium sizing nozzle can no longer meet the needs of continuous casting. Zirconium oxide sizing nozzles with better corrosion resistance must be used. The zirconium oxide content is about 93%-95%. Zirconium oxide sizing nozzles have good corrosion resistance and excellent thermal shock stability. They can meet the needs of multi-furnace continuous casting, improve continuous casting efficiency, и снизить себестоимость продукции. В настоящий момент, zirconium oxide is the material with the best corrosion resistance among functional refractory materials for continuous casting.

During the use of the zirconia sizing nozzle, as the steel slag and inclusions in the molten steel at high temperature penetrate into the pores and react with the impurities and stabilizers in the sizing nozzle, the tight bonding between the zirconia particles is destroyed, and the stable phase changes from the high-temperature phase to the low-temperature phase due to the reduction of the stabilizer. The volume expansion caused by the phase change weakens the bonding between the particles, resulting in the rupture of the particles in the zirconia sizing nozzle, the molten steel enters the nozzle, and the small zirconia particles in the low-temperature phase are washed away by the molten steel, resulting in the continuous expansion of the sizing nozzle. The expansion of the nozzle’s inner diameter will lead to an increase in the flow rate of molten steel flowing into the crystallizer through the nozzle, and the pulling speed of the ingot must also be increased accordingly, which easily causes the ingot to break and stop casting, affecting the normal production process.