The working process of the electric steelmaking furnace is usually in an alkaline erosion atmosphere, so the refractories used in the electric furnace are mainly alkaline refractories, such as MGO-C bricks, asphalt impregnated MgO bricks, MGO-Cr2O3 bricks, MGO-Cao ramming materials, etc., and a small number of neutral refractories, such as A12O3 materials and high aluminum materials.

Overall, the main damage factors of electric furnace refractories are: erosion, oxidation, erosion, melting, peeling and hydration, of which the dominant is oxidation and chemical erosion and erosion.

(1) Chemical erosion: the chemical reaction between the acidic components of iron oxide (FeO) or slag, such as SiO2, and CaO and MgO:

FeO+MgO=FeO·MgO

SiO2+2MgO=2MgO·SiO2

CaO+SiO2+MgO=CaO·MgO·SiO2

These reactions can turn the furnace lining into slag, which leads to the destruction of refractory materials.

(2) Oxidation: It is one of the main reasons for the erosion of refractory materials in the lining of electric furnace, and the carbon component of refractory materials is oxidized by oxygen-containing components (such as iron oxide, oxygen, magnesium oxide) in the process, resulting in material loss and damage.

FeO+C (s) =Fe+CO (g)

O2 (g) +2C (s) =2CO (g)

MgO (s) +C (s) =Mg (g) +CO (g)

The iron oxide in the slag reacts with the graphite or tar/resin in the hot side of the brick lining, or oxygen erodes the graphite or bond in the cold side of the brick lining, in both cases the strength of the brick is reduced and may be eroded by the slag or molten steel. Under the atmospheric conditions in the actual electric furnace, from 1700℃ above, the reaction MgO (s) +C (s) =Mg (g) +CO (g) is easy to occur, and the generated Mg vapor is easy to diffuse and produce tissue cracking, which is one of the main factors causing high temperature damage to magnesian carbon bricks.

(3) Scouring or mechanical impact: due to the molten steel or slag flowing through the surface of the refractory material and physical wear or erosion of the lining, resulting in physical damage, erosion damage in the steel outlet, slag line, electrode port or exhaust platform of the electric furnace. Ordinary. Spalling is a kind of complicated recurrence of refractory damage mechanism, which is caused by the rapid heating and cooling of the furnace lining refractory material caused by stress, the stress often exceeds the strength of the refractory material, resulting in the intersection of cracks through the furnace lining fragments will be spalling or completely off, this situation generally occurs on the top of the electric furnace.

(4) hydration: It is a factor in the damage of electric furnace refractory, easy to penetrate the furnace cover or furnace wall during use, water or water vapor can erode the lining of refractory materials, where magnesium oxide (or other basic oxides) and water (or water vapor) are hydrated following the reaction.

MgO (s) +H2O (1/g) =Mg (OH) 2 (s)

This reaction will lead to a substantial weakening of refractory properties and poor permeability to slag and molten steel.

From the analysis of the above damage causes, it can be seen that the refractory materials selected for the steelmaking furnace and parts have the following requirements for performance:

① Good chemical stability and volume stability;

② High density, low porosity, uniform porosity distribution, molten steel is not easy to penetrate;

③ Resistance to acute cooling, acute heat performance is good, not easy to damage and spalling;

④ High strength can resist mechanical impact and erosion;

The material composition is not easy to react with molten steel and SiO2, and it is not easy to produce nodding.