In the process of steelmaking electric furnace working, it is usually in alkaline corrosive atmosphere, so the refractories used in electric furnace are mainly alkaline refractories, such as MgO-C brick, asphalt impregnated MgO brick, MgO-Cr2O3 brick, MgO Cao ramming material, and a few are neutral refractories, such as Al2O3-C material, high aluminum material, etc.
Generally speaking, the main damage factors of refractories are erosion, oxidation, erosion, melting, peeling and hydration, among which oxidation, chemical erosion and erosion are the dominant factors：
(1) chemical erosion:
The chemical reaction between iron oxide (FeO) or acidic components in slag, such as SiO2, Cao and MgO, is as follows:
FeO+MgO=FeO·MgO（1）
SiO2+2MgO=2MgO·SiO2（2）
CaO+SiO2+MgO=CaO·MgO·SiO2（3）
All of the above reactions can turn the furnace lining into slag and cause damage to the refractory.
- Oxidation is a main cause of erosion of refractories in the lining of electric furnace，In this process, the carbon component of refractories is oxidized by oxygen components (such as iron oxide, oxygen, magnesium oxide), which leads to decarburization damage of refractories.
FeO+C(s)=Fe+CO(g)（4）
O2(g)+2C(s)=2CO(g)（5）
MgO(s)+C(s)=Mg(g)+CO(g)（6）
Iron oxide in the slag reacts with graphite or tar / resin in the hot side of the brick lining, or graphite or binder in the cold side of the brick lining eroded by oxygen. In both cases, the strength of the brick is reduced and may be eroded by slag or molten steel. In the actual furnace atmosphere, starting from 1700 ℃, the reaction (6) is particularly easy to occur, and the Mg (g) produced is easy to diffuse, resulting in tissue degradation, which is also one of the main factors causing high-temperature damage of magnesia carbon brick.
（3）Scour or mechanical impact：
由When the molten steel or slag flows through the refractory surface and physically abrades or scours the furnace lining, it causes physical damage. The erosion mechanism is the most common at the tap hole, slag line, electrode port or exhaust port platform of electric furnace. Spalling is a complicated damage mechanism of refractories. This is caused by the stress of refractory caused by rapid heating and cooling of refractory lining. This stress often exceeds the strength of refractories, which leads to the intersection and penetration of cracks, and the fragments of furnace lining will peel off or completely fall off, which generally occurs on the top of electric furnace.
（4）Hydration is also a factor in the damage of refractories。
In the process of use, water is easy to penetrate into the furnace cover or wall, and water or steam can corrode the refractory lining, in which magnesium oxide (or other basic oxide) reacts with water (or steam) as follows and is hydrated.
MgO(s)+H2O(l/g)=Mg(OH)2(s)（7）
Reaction (7) will lead to the performance of refractories greatly weakened, slag resistance and poor permeability of molten steel. From the above analysis of damage causes, it can be seen that the refractories selected for various parts of the steel-making furnace have the following requirements for performance：
- Good chemical and volume stability；
②The material composition is not easy to react with molten steel and SiO2, and it is not easy to produce nodulation；
③Not easy to be wetted and penetrated by molten steel；
④Good cold and heat resistance, not easy to be damaged and peeled off；
⑤High density, low porosity, uniform distribution of pores, and impermeability of molten steel；
⑥High strength, resistant to mechanical impact and scour。
