MgO-CaO material is widely used in outside-furnace refining and cement rotary kiln firing zones because of its excellent high-temperature performance and unique function of purifying molten steel. Currently commonly used magnesium-calcium products include unburned magnesia-calcium products, burned magnesia-calcium products, ramming materials and coatings, etc. Moreover, magnesium-calcium refractory materials do not have environmental pollution problems.
MgO and CaO are both high melting point oxides, and their lowest eutectic temperature reaches 2300°C, so this type of material has high refractoriness and load softening temperature.
For low alkalinity slag, CaO in the magnesia-calcium sand dissolves first and reacts with SiO2 in the refining slag to produce high-viscosity C2S and C3S, which blocks permeability channels such as pores and reduces the erosion rate of the slag.
There is a large amount of free CaO in magnesium-calcium refractory materials. Free CaO has good plasticity and large creep at high temperatures, which can buffer the thermal stress caused by thermal shock and significantly improve the thermal shock resistance of magnesia-calcium materials.
CaO has good thermodynamic stability and its partial pressure is very low at high temperatures, followed by MgO. Magnesium-calcium materials lose weight at a very low rate in a vacuum environment. Therefore, it can be used in harsh refining environments outside the furnace.
The free CaO in the magnesia-calcium refractory material can react with impurities in the molten steel to remove non-metallic elements contained in the molten steel. It has good desulfurization and dephosphorization effects and can effectively purify the molten steel.
However, since the free CaO in magnesium-calcium materials is easily hydrated, a volume effect close to 100% will occur during the hydration process, causing the product to become pulverized and ineffective.Therefore, solving the problem of hydration resistance of magnesia-calcium materials is a key factor for the widespread use of such materials.
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