In the case of smelting low carbon steel, ultra-low carbon steel and killed steel, the commonly used magnesia chrome brick, alumina magnesia carbon brick, magnesia dolomite brick, castable and commonly magnesia carbon brick cannot meet the requirements of steel quality improvement and smelting speed. Therefore, according to the requirements of steel refining and smelting conditions, low-carbon micro expansion magnesia carbon brick has been developed and produced, the furnace life has been increased and the quality of steel has been improved, and it has been widely promoted in the domestic and foreign steel industry.
At present, there are more than 30 ways of refining, including DH, Rh, AOD, VOD, LF, VaD, asea-dkf and so on. Now it has become the key link in the production process of improving the quality of molten steel (i.e. steelmaking, refining outside the furnace and continuous casting). Although the processes of various refining methods are different, there are many common points:
(1) vacuum, inert gas or reducing atmosphere are usually used to create an ideal refining atmosphere for molten steel;
(2) the molten steel is stirred by electromagnetic force, inert gas or mechanical stirring;
(3) adopt heating measures, such as arc heating, submerged arc heating, plasma heating or increasing chemical heat in molten steel, etc., to compensate the temperature loss of molten steel in the refining process.
Because of the different operation conditions of various secondary refining units, the damage mechanism of lining is also different. The main causes of lining corrosion are the dissolution of refractory into slag, the penetration of slag into refractory, thermal peeling and structural peeling.
The main purpose of adding graphite in MgO-C refractories is to solve the problem of thermal spalling and residual linear expansion. However, the amount of graphite in refractories affects the carbon content and chemical composition of molten steel. How to further reduce the amount of graphite and prevent the thermal peeling and residual linear expansion of products from increasing and decreasing properly.