Refractory materials for ferroalloy electric furnace include three parts: furnace top refractory materials, furnace wall refractory materials and molten pool refractory materials (furnace slope and furnace bottom). During the ferroalloy smelting process, the refractory materials in different parts are in different working conditions.
The furnace top refractory materials are mainly affected by the erosion and impact of high-temperature furnace gas and sprayed slag, the temperature change during the charging interval and the radiant heat of high-temperature arc light, the air flow impact and pressure change during the collapse of materials.
The furnace wall refractory materials are mainly subjected to the high-temperature radiation of the arc and the temperature change during the charging interval; the erosion and impact of high-temperature furnace gas and sprayed slag; the impact and wear of solid materials and semi-molten materials; the severe slag erosion and slag impact near the slag line. In addition, when the furnace body is tilted, it is also subjected to additional pressure.
The furnace slope and furnace bottom refractory materials are mainly subjected to the pressure of the upper furnace charge or molten iron; the temperature change during the charging interval, the impact of the furnace charge and the arc melting loss; the erosion and impact of high-temperature molten iron and slag.
In order to ensure the normal operation of the electric furnace, it is necessary to use refractory materials with high refractoriness and load softening temperature, good resistance to rapid cooling and heat, and slag resistance, large heat capacity and certain thermal conductivity to build the electric furnace lining.
The performance and usage characteristics of refractory materials for linings often used in ferroalloy production are as follows:
01 Clay bricks
The main raw material for making clay bricks is refractory clay with good plasticity and bonding strength.
The main performance characteristics of clay bricks are: strong resistance to acidic slag, good resistance to rapid cooling and heat, good thermal insulation and certain insulation performance; low refractoriness and load softening temperature. Clay bricks should not be used directly under high temperature conditions and special requirements.
In ferroalloy production, clay bricks are mainly used to build the furnace wall lining of the exposed part of the ore-fired furnace, the outer lining of the furnace wall and furnace bottom that plays a role in insulation and insulation, or for building the inner lining of the ladle.
02 High alumina bricks
The main raw material for making high alumina bricks is high alumina bauxite, and the binder is refractory clay.
Compared with clay bricks, the biggest advantages of high-alumina bricks are high refractoriness, high load softening temperature, good slag resistance and high mechanical strength. The disadvantage is that high-alumina bricks have poor resistance to rapid cooling and heating.
In ferroalloy production, high-alumina bricks can be used to build lining bricks for the tapping of submerged arc furnaces, the top of refining electric furnaces, and can also be used to build linings for ladles.
03 Magnesia bricks and magnesia sand
The main raw material for making magnesia bricks is magnesite, and the binder is water and brine or sulfite pulp waste liquid.
The main performance characteristics of magnesia bricks are: high refractoriness and excellent resistance to alkaline slag; but the thermal conductivity and electrical conductivity under high temperature are large, and the load softening temperature is low, and the resistance to rapid cooling and heating is poor. Powdering occurs when exposed to water or steam at high temperature.
In ferroalloy production, magnesia bricks are used to build the walls and bottom of high-carbon ferrochrome reduction electric furnaces, medium- and low-carbon ferrochrome converters, shaking furnaces, and refining electric furnaces, as well as the lining of the ladle containing ferrochrome and medium- and low-carbon ferromanganese. Magnesia-alumina bricks are used to build the furnace roof instead of magnesia bricks. Magnesia sand has a high refractoriness. In ferroalloy production, magnesia sand is often used to knot the furnace bottom, make and repair the furnace wall and furnace bottom, and can be used as a material for plugging eyes or making knotted ingot molds.
04 Carbon bricks
The main raw materials for making carbon bricks are crushed coke and anthracite, and the binder is coal tar or asphalt.
Compared with other common refractory materials, carbon bricks not only have high compressive strength, small thermal expansion coefficient, good wear resistance, high refractoriness and load softening temperature, good resistance to rapid cooling and heating, but also particularly good slag resistance. Therefore, all ferroalloy varieties that are not afraid of carburization can use carbon bricks as lining materials for submerged arc furnaces.
However, carbon bricks are very easy to oxidize under high temperature conditions, and their thermal conductivity and electrical conductivity are relatively large. In ferroalloy production, carbon bricks are mainly used to build the furnace walls and furnace bottoms of the submerged arc furnace that are not exposed to the air.
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