Boron Nitride Break Ring

The horizontal continuous steel casting method provides a number of advantages, including simple equipment process, good billet quality, energy savings, and increased metal output. It has grown tremendously in popularity internationally in recent years. The ceramic break ring is a critical component of horizontal continuous casting equipment's technical design. To begin, it is placed at the junction of the tundish and the crystallizer, and molten steel flows from the tundish to the crystallizer via the nozzle and break ring. Between the melting and solidification zones of molten steel is the break ring. It is subjected to a thermal shock of approximately 1570°C during the initial casting process and to thermal stress created by a temperature differential of approximately 150°C-1570°C throughout the continuous casting process, and it is constantly under erosion in the molten steel. As a result, it is challenging for common refractory materials to match their application criteria. UNIPRETEC developed the BN-3000 material to overcome the limitations of conventional technical ceramics in this application.

BN-3000 is a hexagonal boron nitride composite material. On the one hand, BN-3000 increases the brittleness of technical ceramics, their low thermal shock resistance, their susceptibility to molten steel corrosion, and their ability to handle more difficult faults. On the other hand, BN-3000 addresses the shortcomings of conventional hot-pressed BN engineering materials, which are prone to absorb moisture and decompose, are inconvenient to store and use, and have a high thermal conductivity, resulting in excessively high temperature rises in the continuous casting machine's three critical points and causing the continuous casting process to become unstable. Additionally, the BN-3000 can increase the break ring's storage conditions and performance.

BN-3000 exhibits superior physical and chemical properties at elevated temperatures, and its high-temperature thermal shock resistance attenuation temperature (>920°C) is significantly higher than that of conventional structural ceramic materials. Additionally, due to the material's strong high-temperature strength, moderate density, and big infiltration angle with molten steel, it exhibits good resistance to molten steel erosion and abrasion, extending the break ring's service life significantly. The break ring for horizontal continuous cast steel prepared with BN-3000 satisfies the requirements for high thermal shock resistance in the horizontal continuous casting process, can withstand thermal stress damage caused by a temperature difference of approximately 1570°C-150°C, and is resistant to the wear and corrosion requirements of melting carbon steel, alloy steel, and stainless steel.  Simultaneously, the thermal conductivity of this composite material is low, ensuring that both the inside and outside of the cast slab crystallize uniformly and finely, avoiding the high thermal conductivity of standard hot-pressed BN material, which causes the critical control parameter of the continuous casting machine-the triple point temperature-to be set too high, resulting in instability or even failure. Furthermore, this break ring is resistant to moisture, has a high manufacturing accuracy, and is not easily damaged during the assembly process. It fully complies with the industrial level continuous casting use requirements following the industrialization level continuous casting evaluation test.

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