LF device is also called ladle refining furnace. This method was developed by Japan in 1971. The reduction refining process of the electric arc furnace is transferred to the ladle refining device with heating refining function, and the influence of the melting oxidation refining process of the electric arc furnace on the reduction refining process is minimized to ensure the reduction refining effect of the device.
The LF refining furnace consists of an electrode heating system, an alloy and slag feeding system, a bottom air-permeable brick argon blowing stirring system, a temperature measurement sampling system, a wire feeding system, a furnace cover cooling system, a dust removal system and a control system. The parts that need to use refractory materials are: LF refining furnace top (furnace cover), refining ladle, bottom air-permeable bricks and tundish slides, etc.
The commonly used refractory materials of LF furnace are divided into slag line parts, furnace walls, furnace covers and ladle bottoms. The slag line is severely damaged by the erosion of high-alkalinity slag, and magnesia-carbon bricks with good thermal shock resistance are often used; the LF furnace slag penetration is serious, which is easy to cause structural spalling. The traditional high-alumina bricks can no longer meet the requirements, and materials with added carbon and MgO need to be used to overcome it. The refining ladle lining has also developed from fixed to amorphous; the furnace cover is basically made of castables; the furnace bottom is made of cast bricks or dry ramming materials.
01 Refractory materials in the slag line area
Since the LF furnace slag line area is in a high-alkalinity slag and high-stress environment, the slag line area is more easily damaged, so the refractory bricks in this area are generally magnesia-carbon bricks, magnesia-calcium-carbon bricks, and fused and combined magnesia-chrome bricks.
02 Refractory materials for the ladle wall
The high-alumina products used in the ladle wall in the early days often need to add a small amount of magnesia sand or synthetic magnesia-alumina spinel to the material to improve the corrosion resistance and high-temperature shrinkage of high-alumina products due to severe corrosion and deterioration of use conditions. At present, the refractory materials in the ladle lining have developed from shaped products to amorphous products, and the materials include high-alumina bricks, magnesium-aluminum carbon, aluminum-magnesium carbon, and unburned magnesium-calcium.
03 Refractory materials for furnace cover
Since the furnace cover is eroded by molten steel and splashing slag, and affected by thermal shock during operation, the refractory materials in the furnace cover must have good high temperature resistance, excellent thermal shock resistance and spalling resistance. At present, the refractory materials used in the furnace cover are mainly high-alumina or corundum series castables, mostly with fused corundum and special-grade bauxite as the main raw materials, pure calcium aluminate cement as a binder, silica fume and activated alumina powder as additives, after vibration molding, low-temperature baking.
04 Refractory materials for the bottom of the ladle and the air-permeable bricks
① The impact zone of the bottom of the ladle is mostly cast with high-alumina-spinel castables to form large bricks;
② Other parts can use high-calcium-magnesium dry ramming materials;
③ The base bricks of the ladle are mostly made of ultra-low cement high-alumina castables containing Cr₂O₃ and steel fibers.
④ The air-permeable bricks are made of straight-through narrow-slit corundum or chrome corundum air-permeable bricks.
05LF furnace repair material
Flame gunning material: the materials are mostly aluminum-chromium, alumina-spinel, and aluminum-zirconium;
Semi-dry gunning material: the materials are mostly magnesium oxide and aluminum silicon;
Casting repair material: the materials are mostly MgO-C castables.
For LF furnaces, brickwork is mostly used for slow turnover. Magnesium carbon bricks are used for the slag line, and aluminum-magnesium carbon bricks or magnesium carbon bricks are used for other parts. The service life is mostly 50~80 times; while for the LF furnace lining and large ladle with fast turnover bricks, the service life is basically the same, that is, magnesium carbon bricks are used for the slag line, and aluminum-magnesium castables are used for the bottom and molten pool. The service life of the slag line is mostly 60~100 times. Other parts are also about 150 times.
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