Selection of calcium silicon alloy submersible furnace lining refractory materials
At present, the production of calcium silicon alloys at home and abroad generally uses submerged arc furnaces for smelting. According to different feeding methods, there are four types: mixed feeding method, two-step method, layered feeding method and electrosilicothermal method. The two-step method and the electrosilicothermal method are rarely used in our country.
Calcium silicon alloy smelting is carried out at high temperatures. For large-scale calcium silicon alloy electric furnace smelting, the alloy liquid temperature is as high as 2000°C when it comes out of the furnace. Therefore, the life of the furnace lining, especially the life of the tap hole, directly affects the age of the furnace.
When the calcium silicon alloy electric furnace is smelting iron, the temperature is high. At the same time, a large amount of high-temperature furnace gas is violently discharged. The tap hole has to withstand the joint erosion of high temperature, chemical, mechanical and other factors. Therefore, the tap hole and iron water tank of the electric furnace have become the most important. Consumable parts. Usually, tapholes and iron troughs for smelting ferroalloys are made of carbonaceous, magnesian (such as ferrochromium), and high-aluminum (such as ferrosilicon) refractory materials. Small calcium silicon alloy electric furnaces use carbonaceous refractory materials, which have a short service life and burnout. The damage is serious, it is difficult to plug the holes, and it may even lead to furnace leakage accident and furnace shutdown, seriously affecting the normal production.
Combined with the use environment and site conditions, the tap hole of this electric furnace is made of silicon nitride combined with silicon carbide refractory materials, which have high refractory resistance. After the refractory materials are roasted at high temperatures, their load softening points are also high, both above 1750°C. Thermal conductivity is relatively high, heat conduction and heat dissipation are good, and high temperature oxidation resistance is good. The binder formula used is: 100kg electrode paste powder with a particle size less than 1mm, add 2% cellulose and 20%~30% glass water to make a paste. Maintenance: Use anhydrous gun mud containing 5% to 8% silicon carbide as the plugging material during production. Regularly repair the outside of the taphole and the severely oxidized parts of the tap trough with tamping paste containing silicon carbide. . The formula of tamping paste for repair is: electrode paste powder: silicon carbide powder = (6.5~7.5): (2.5~3.5). The use of special taphole materials, special binders and regular maintenance processes ensure that the taphole remains in good operating condition after 3 years of continuous operation. During use, there has been no slag iron in non-tapping conditions. Burn-through phenomenon caused by hole outflow.
Configuration selection of calcium silicon alloy molten iron ladle lining refractory materials
Calcium silicon alloy is a ternary alloy composed of the elements silicon, calcium and iron. The products mainly come in two physical forms: block and powder. Its calcium content is generally between 24% and 31%, and its silicon content is between 55% and 65%. As an ideal composite deoxidizer and desulfurizer, calcium silicon alloy is widely used in low carbon steel and stainless steel. It is an indispensable additive for obtaining high-quality steel and special steel.
The molten iron ladle plays a connecting role in the entire calcium silicon alloy production. The calcium silicon alloy solution smelted in the submerged arc furnace is poured into the molten iron ladle, and then transported to the next production process by the molten iron ladle.
Large electric furnaces smelt silicon-calcium alloys. A furnace of molten iron is produced every 1.5 to 2 hours. Each furnace has about 2.4 to 2.8 tons of alloy liquid and about 0.8 to 1.2 tons of slag. The generated slag is frequently discharged with the molten iron and poured into the molten iron ladle. middle. Due to the action of flowing periodic high-temperature molten iron and slag, its use conditions are very harsh, and are mainly affected by the following damaging factors: violent impact of flowing high-temperature molten iron and slag (especially 1~5m away from the tap hole); high temperature Chemical erosion and penetration of molten iron and slag; sharp changes in intermittent tapping temperature, and frequent alternation of rapid cooling and rapid heating. Obviously, the refractory temperature of traditional silicon or high-aluminum refractory linings cannot withstand the erosion and erosion of fluids above 1900°C. They are easily burned through and have low safety.
After on-site practice, graphite bricks impregnated with phosphoric acid were used to fix the graphite brick group to build the inner layer of the bottom and wall of the package. Calcined anthracite particles were mixed with refractory cement to build the outer layer of the molten iron package wall. This method better solves the problem that the molten iron ladle is easy to burn through, greatly extends the service life of the ladle lining, and is low in cost.
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