During the use of steel smelting refractories, molten steel passes through its inner hole or surface. Excellent thermal shock resistance is the premise for the use of steel smelting refractories. Otherwise, under the harsh thermal shock conditions of molten steel above 1500 ℃, the materials are prone to cracking and fracture, resulting in material failure, production interruption and even safety accidents.
The microenvironment of different parts of steel smelting refractories is also different, resulting in different corrosion losses at different parts. According to the "barrel" effect, the erosion speed of key parts determines the service cycle, which is another remarkable feature of steel smelting refractories. For example, the slag line of submerged nozzle is alternately eroded by molten steel and slag, and its erosion speed is much higher than that of bowl, steel outlet and other parts, The corrosion resistance of slag line is the decisive factor to determine the number of continuous casting furnaces. Excellent corrosion resistance is an important condition to ensure that the steel smelting refractory can be used for a long time under the action of molten steel and slag. It is also the basis for the realization of its function. It has an important impact on the stability of steel production rhythm, the improvement of efficiency and the guarantee of product quality. The excellent function is to meet the needs of iron and steel production process and the necessary conditions for improving smelting effect, such as the ventilation and mixing function of ventilation elements, restricting the uniformity of molten steel composition and temperature and the floating efficiency of inclusions, which has a great impact on the secondary refining effect of molten steel.
Generally, the thermophysical properties and structure of refractories determine their thermal shock resistance, and their composition and microstructure determine their corrosion resistance. For steel smelting refractories, in terms of composition, structure and performance regulation, thermal shock resistance and corrosion resistance restrict each other. Improving corrosion resistance will lead to poor thermal shock resistance, and vice versa. It is difficult to make steel smelting refractories have excellent thermal shock resistance and ensure safe use and corrosion resistance and long life. In addition, for steel smelting refractories, the functional design will also affect the thermal shock resistance and corrosion resistance of the materials. For example, according to hasselman's energy theory of crack propagation, high thermal shock resistance requires materials with high thermal conductivity, low coefficient of linear expansion, high porosity and low elastic modulus.
In the design and preparation of steel smelting refractories, increasing the content of graphite and fused quartz is often used to improve their thermal shock resistance. However, the slag resistance of fused quartz is poor, the material with high carbon content and high porosity is not resistant to liquid steel erosion and produces pollution, which degrades the function of the material, and the service life is only a few hours; Containing quartz in carbonaceous materials will lead to the increase of non-metallic inclusions and seriously damage the quality of billets. Therefore, the design principle of iron and steel smelting refractories is to balance thermal shock resistance, erosion resistance and function. The goal is to improve thermal shock resistance, erosion resistance and ensure excellent function. This is not only the key to the development of high-performance iron and steel smelting refractories, but also the common key technology restricting other fire-resistant materials to improve the service life of refractories.
The iron and steel smelting refractories produced by Kerui refractory include clay refractory brick, high alumina refractory brick, corundum brick, magnesia brick, carbon brick, silica brick, lattice brick, high alumina refractory ball, iron ditch refractory castable, dry ramming material, blast furnace lining spraying coating, tundish refractory coating, etc.