Anti-flaking Property of Magnesia-calcium Brick
Anti-flaking property of magnesia-calcium brick
During the use of magnesia-calcium bricks, the working layer is cracked and peeled off due to the damage of the furnace temperature and the slag penetration, especially in the VOD furnace, the spalling damage of the magnesia-calcium brick is more serious. Therefore, improving the spalling performance of magnesia-calcium bricks is also one of the ways to improve the service life of magnesia-calcium brick linings.
The spalling of magnesia-calcium bricks is divided into hot peeling and structural spalling. Magnesia-calcium bricks used in refining equipment such as AOD furnaces, VOD furnaces, and LF furnaces have partial thermal peeling due to periodic rapid changes in furnace temperature. The structural spalling is that the high-temperature slag penetrates into the interior of the use through the pores and cracks, and a metamorphic layer of a certain thickness is formed at the working end of the brick. When the furnace temperature changes abruptly, cracks in different directions are generated in the magnesia-calcium brick, cracks in different directions are generated in the magnesia-calcium bricks, and as the cracks continuously increase and expand, the metamorphic layers are continuously peeled off.
Magnesia-calcium bricks have excellent resistance to spalling compared to other magnesia-based refractory products, because CaO in magnesia-calcium bricks has large creep at high temperatures, and can buffer thermal stress generated inside bricks due to rapid temperature changes. It inhibits the generation and expansion of cracks inside the brick and improves the ability of the magnesia-calcium brick to resist thermal peeling. On the other hand, the CaO in the magnesia-calcium brick reacts with SiO2 in the slag to produce a high-melting mineral, which improves the viscosity of the slag, makes it more difficult for the slag to penetrate into the interior of the brick, and thins the metamorphic layer, thereby improving the magnesia-calcium brick. Resistance to structural spalling.
In the case of magnesia-calcium bricks, increasing the ratio of large particles and appropriately reducing the ratio of medium particles to fine powder can improve the anti-flaking performance of magnesia-calcium bricks. And adding an appropriate amount of ZrO2 fine powder, the formation of high melting point mineral CaZrO3 in the matrix, can effectively prevent the generation of cracks, improve the toughness and anti-flaking properties of magnesia-calcium brick.