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The purpose of refining outside the furnace is to degas, deoxidize, desulfurize, remove inclusions, fine tune the composition and control the temperature of the molten steel to obtain the high quality molten steel required for continuous casting. In this process, refractory materials have a certain influence on the quality of molten steel.
At the time of selection, we must consider the temperature of the molten steel, stirring, treatment time, vacuum, arc heating, refined steel grade, the nature of the slag, the alkalinity of the slag, the fluidity of the slag, etc. .
Magnesia chrome brick
Magnesia-chrome brick is an alkaline refractory material mainly composed of magnesia and chrome ore. Magnesia-chrome brick has the characteristics of high refractoriness, high load softening temperature, good thermal shock resistance, strong resistance to slag erosion, and wide range of alkalinity of slag. According to different raw materials and process characteristics can be divided into:
1 silicate combined with magnesia chrome brick
The sintered magnesia and the general refractory grade chrome ore are used as raw materials, and are mixed in an appropriate ratio, and the sulfite pulp waste liquid is used as a binder, kneaded and formed, and fired at 1600 ° C.
Typical physical and chemical indicators of silicate combined with magnesia chrome brick
2 directly combine with magnesia chrome bricks. High-purity magnesia and chrome ore are used as raw materials, high-pressure molding, and fired at 1700~1800 °C to produce high-quality solid-phase combined magnesia-chrome bricks.
Typical physical and chemical indicators of several direct combination of magnesia chrome bricks
3 combined with magnesia chrome bricks (electrofusion combined with magnesia chrome bricks). Using magnesite (or light burnt magnesium powder) and chrome ore as raw materials, according to a certain proportion, into the electric furnace to melt, synthesizing fused magnesia chrome frit, then crushing, mixing, high pressure molding, burning at 1750 ° C or higher Made into.
4 and a half combined with magnesia chrome bricks. Partially fused synthetic magnesium chrome sand is used as raw material, and part of chrome ore and magnesia or sintered synthetic magnesium chrome are added as fine powder, which is prepared by high temperature firing according to conventional brick making process.
The product has compact structure, low porosity, high temperature strength, strong erosion resistance, thermal shock resistance better than recombined magnesia chrome brick, RH and DH vacuum degassing dip tube, VOD furnace, LF furnace, AOD furnace. The slag line of the refining equipment outside the furnace.
5 pre-reactive magnesia chrome bricks. Light calcined magnesium powder and chromite ore are used as raw materials, and finely ground into fine powder with a particle size of less than 0.088mm, pressed into a blank or ball, calcined into a pre-reacted sintered material at 1750-1900 °C, and then pressed into a conventional brick making process. Production, crushing, mixing, high pressure molding and firing at 1600~1780 °C.
The product has compact structure, uniform composition, low porosity, high temperature strength, good slag resistance and good thermal shock resistance, and can be used for slag line parts of refining equipment such as VOD furnace, LF, furnace and the like. The national standards for magnesia chrome bricks are shown in Table 4.
Magnesium chrome brick physical and chemical indicators
2. MgO-CaO refractory
1 dolomite brick
An alkaline refractory material containing W(CaO)>40% and w(MgO)>30% made of calcined dolomite sand as main raw material. According to different production processes, it is divided into tar-bonded dolomite brick, light-burned oil-impregnated dolomite brick and fired oil-impregnated dolomite brick.
Dolomitic bricks are highly resistant to alkaline slag, but they are easily hydrated in the air and are not easy to store for a long time. They are suitable for AOD and VOD furnaces and ladle linings.
2 magnesium dolomite brick
The basic refractory material containing MgO and CaO as main components contains 50% to 80% of MgO and 40% to 10% of CaO. According to different production processes, it is divided into tar-mixed magnesium dolomite brick, light-burned oil-impregnated magnesium dolomite brick and fired oil-impregnated magnesium dolomite brick.
Magnesia dolomite brick has high MgO content, good slag corrosion resistance, hydration resistance and high temperature strength, and is suitable for AOD and VOD furnaces and ladle lining. The typical physical and chemical properties are shown in Table 5.
Typical physical and chemical properties of magnesium dolomite brick
3 magnesium calcium carbon brick
Magnesia-calcium carbon brick is a non-burning carbon-containing alkaline refractory product made of dolomite sand, calcium oxide sand, magnesia sand and flaky graphite.
Magnesia-calcium carbon bricks have excellent properties of magnesia-carbon bricks and dolomite bricks, have good resistance to slag erosion and permeability, and are suitable for AOD and VOD furnaces and ladle linings.
4 magnesium calcium brick
The main components of magnesia-calcium bricks are magnesia and calcium oxide. When the magnesia content in the brick is higher than 60%, the corrosion resistance of dolomitic refractories can be significantly improved, and the increase of calcium oxide content is beneficial to improve. The material is resistant to penetration and thermal shock.
3. Magnesia carbon brick
Magnesia carbon brick is a non-burning carbon-containing alkaline refractory material made of fused magnesia, high-purity magnesia and flaky graphite, and a phenolic resin as a binder. The production process is basically the same as that of general refractory bricks, but not It needs to be fired and only needs to be heat treated at 200~250 °C.
Magnesia carbon bricks are divided into four categories according to the carbon content:
1C 10%, MgO76%-80%;
2C 14%, MgO 74%-76%;
3C 18%, MgO 70%-72%;
4C 5%, MgO 82%~85%.
Physical and chemical indicators of MgO-C magnesium-calcium carbon brick
1 aluminum magnesium carbon brick
The special grade clinker clinker is used as the aggregate, and fused magnesia or sintered magnesia powder and flaky graphite are added, and the phenolic resin is used as a binder, and after being press-formed, it is obtained by heat treatment at 200 to 250 °C. The aluminum-magnesium carbon brick has good resistance to slag penetration, strong corrosion resistance, good thermal shock resistance and low price, and is suitable for non-slag line parts of various refined ladle.
The national standards for aluminum-magnesium carbon bricks are shown in Table 5.10.
Physical and chemical index of resin combined with aluminum-magnesium carbon brick
2 aluminum-magnesium spinel carbon brick
Same as aluminum-magnesium carbon bricks, except that the pre-synthesized aluminum-magnesium spinel clinker is used as a raw material to replace or replace part of alumina and magnesia. Thereby, the formation of spinel during use and the resulting expansion effect can be adjusted and controlled, which is beneficial to improving the corrosion resistance and high temperature volume stability of the product, and is used for refining the non-slag line portion of the ladle.
3 magnesium aluminum carbon brick
The difference from the aluminum-magnesium carbon brick is that the content of Al2O3 and MgO is reversely changed, and the brick making process is the same. Magnesium-aluminum carbon brick has good slag resistance and strong corrosion resistance. The performance of magnesium-aluminum carbon brick is between magnesia carbon brick and aluminum-magnesium carbon brick, which can be used for the transition zone between ladle slag line and wall. Can be used on the wall of steel ladle.
5. Magnesia brick
1 burned magnesia brick
The calcined magnesia brick is a product which is fired at a high temperature of about 1500 ° C after being formed by calcination of magnesia as a main raw material. The product has good high temperature performance and strong resistance to metallurgical slag. It is widely used in steelmaking lining, iron alloy furnace, mixed iron furnace and converter permanent lining in steel industry; copper, lead and tin lining in colored industrial furnace.
2 combined with magnesium brick
The combined magnesium brick is a kind of product which is made of fused magnesia as the main raw material and is formed by high pressure molding and firing at 1800 °C. The product is commonly used in steel slag erosion and severely worn steelmaking furnace tapholes, slag line parts of non-ferrous metallurgical slag and the like.
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