Causes of refractory loss for EAF steelmaking

Source: | Author:ChangXing Refractory | Published time: 1605 days ago | 980 Views | Share:

Steelmaking electric furnaces are usually in an alkaline corrosive atmosphere during the work process, so the refractories used in electric furnaces are mostly alkaline refractory materials, such as MgO-C bricks, asphalt-impregnated MgO bricks, MgO-Cr2O3 bricks, and MgO-CaO ramming A small part of the raw materials are neutral refractory materials, such as A12O3 materials and high-aluminum materials.

In general, the main damage factors of electric furnace refractories are: erosion, oxidation, erosion, melting, spalling and hydration, of which oxidation and chemical erosion and erosion are dominant.

(1)Chemical attack: Iron oxide (FeO) or acidic components in the slag, these reactions can turn the furnace lining into slag, resulting in the destruction of refractory materials.

(2) Oxidation: It is one of the main causes of corrosion of refractory materials in the lining of electric furnaces. During the process, carbon components in refractory materials are oxidized by oxygen-containing components (such as iron oxide, oxygen, and magnesium oxide), causing the material to fall off and be damaged. The iron oxide in the slag reacts with the graphite or tar/resin in the hot surface of the brick lining, or oxygen attacks the graphite or the binder on the cold surface of the brick lining. In both cases, the strength of the brick decreases and may be caused by molten slag or molten steel. Erosion. Under the actual atmosphere conditions in the electric furnace, starting from above 1700℃, the reaction MgO(s)+C(s)=Mg(g)+CO(g) is easy to occur, and the generated Mg vapor is easy to diffuse and cause structure cracking. This is One of the main factors causing high temperature damage to magnesia carbon bricks.

(3)Erosion or mechanical shock: physical damage caused by molten steel or molten slag flowing over the surface of refractory materials and physical wear or scouring of the furnace lining, erosion damage at the tap hole, slag line, electrode port or exhaust platform of the electric furnace eclipses are the most common. Spalling is an intricate and recurring damage mechanism of refractory materials. This is caused by the rapid heating and cooling of the lining refractory material, which causes the refractory material to produce stress. This stress often exceeds the strength of the refractory material, which leads to the intersection of cracks and penetration. The fragments will peel off or fall off completely, which generally occurs on the top of electric furnaces.

(4)Hydration: It is a factor in the destruction of refractory materials in electric furnaces. It is easy to penetrate into the furnace cover or furnace wall during use. Water or steam can corrode the furnace lining of refractory materials. Magnesium oxide (or other alkaline oxides) and water (or steam) undergoes the following reaction to be hydrated. This reaction will cause the performance of refractory materials to be greatly weakened, and the permeability of slag and molten steel will be poor. From the above analysis of the causes of damage, 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 pore distribution, molten steel is not easy to penetrate;
③ Good resistance to rapid cold and rapid heat, not easy to break and peel off;
④ High strength can resist mechanical external impact and erosion;
⑤ It is not easy to be wetted and penetrated by molten steel;
⑥ The material composition is not easy to react with molten steel and SiO2, and it is not easy to produce nodules.