What are the main factors affecting the age of UHP DC EAF? – Smelting technology
Description: Baosteel’s 150-ton ultra-high-power DC electric arc furnace was imported from France’s CLECIM company and uses water-cooled steel rod-shaped bottom electrodes. The power is 99MVA; a series of new technologies such as oxygen lance fluxing, one electric and two furnaces, water-cooled furnace wall, water-cooled furnace cover, bottom-blown argon stirring, submerged arc operation of foamed slag, and eccentric bottom tapping are adopted. Mainly include: bottom electrode sleeve brick, small furnace bottom ramming material, furnace bottom ramming material, electric furnace magnesia carbon brick, electric furnace gunning material, furnace cover castable, tapping hole gunning material, tapping hole filling material, etc. .
High Power DC Electric Arc Furnace, Electric Arc Furnace Technology, Smelting Technology, Electric Furnace Steelmaking
Main Factors Affecting the Age of UHP DC Electric Arc Furnace
1. The effect of high temperature heat:
The smelting temperature is generally above 1600 ℃, which has a great influence on the furnace age. In addition, due to the design of one electric and two furnaces, the furnace lining has to withstand rapid cooling and rapid heating. This phenomenon is unavoidable in the smelting process, but the degree and time of high-temperature thermal action should be reduced or shortened as much as possible, such as rapid furnace repair and charging, ensuring normal operation of equipment, and minimizing thermal shutdown.
2. The effect of chemical attack:
In the process of steelmaking, various chemical reactions are carried out from beginning to end, especially at the slag-steel interface, where the lining refractories are easily peeled off under the action of chemical reactions.
Chemical attack is related to the composition and fluidity of the slag. When the content of acidic or slightly acidic oxides such as SiO2, P2O5, Al2O3 or Fe2O3 in the slag is high, MgO is easily reacted to generate corresponding magnesium silicate and magnesium aluminate. The influence of the fluidity of the molten slag on chemical erosion is mainly manifested in: the alkalinity of the thin slag is low, the chemical reaction is violent and the molten pool can be rolled, which can easily increase the thermal load of the furnace lining; The smelting time also promotes the damage of the furnace lining.
In addition to this, chemical attack is also related to the composition of elements in the molten steel. When smelting steel with high Mn, Si, W or very low carbon content, or when the steel is mixed with a small amount of Pb, Zn and other elements, the erosion of the furnace lining is even more severe. If the temperature is higher than 1600°C and the manganese content in the steel is more than 10%, Mn will react with SiO2 in the refractory as follows:
While the above reaction is carried out, the softening point of the refractory material will decrease to 1150~1250℃. For this reason, when smelting steel grades such as ZGMn, the smelting temperature cannot be too high, and the operation is required to be fast and accurate.
When smelting high silicon steel, the slag contains relatively high SiO2, which reduces the basicity of the slag and erodes the furnace lining. Therefore, when a large amount of ferrosilicon is added to the furnace, the steel should be tapped as soon as possible. When smelting high tungsten steel, tungstate will appear in the molten steel, which also has a corrosive effect on the bottom of the furnace. Under the same conditions, when smelting steel with very low carbon content, due to the high content of [FeO], [FeO] will form a low melting point compound with SiO2 in the refractory material, which will inevitably cause serious erosion to the furnace lining. Pb corrodes the bottom of the furnace seriously, and can even cause a vicious accident of leakage of the furnace. The Zn element is also very harmful to the refractory material of the furnace lining, especially its oxides are easily accumulated in the pores of the refractory material, which causes the expansion of the refractory material and causes cracks.
3. Influence of arc radiation or reflection:
Electric furnace steelmaking relies on the conversion of electrical energy into heat energy to melt the cold material and heat the molten pool. The conversion and transfer of this energy is completed by the arc light of the electric arc. The radiant or reflected heat of the arc will also act on the lining to soften the refractory. At present, in the smelting process of electric furnace steel, although the influence of arc radiation or reflection on the life of the furnace lining cannot be completely avoided, it can be minimized through various ways. For example: when charging, the solid cold material should be reasonably distributed in the furnace, so that the arc light can be surrounded by the steel material within a short period of time after power transmission; in the smelting process, the arc light can be surrounded by It can also greatly reduce the damage to the furnace lining due to arc radiation or reflection.
4. The influence of mechanical collision and vibration
Unreasonable charging and distribution, there is no light waste under the heavy material, or the material basket is lifted too high, the furnace bottom and furnace slope may be subjected to the collision, vibration and impact of large heavy materials to form potholes. If the charging is unmanned or the crane is not running normally, the result will be that the material basket is pulled and slanted and the furnace wall is damaged. Or the selection of steel materials is not strict, and there is a serious explosion during the melting period, which will reduce the service life of the furnace lining. The smelting workshop is noisy, and the impact of noise waves is also another factor for damage to the furnace lining.
5. The influence of operation level
In the smelting process, low-level operation is extremely harmful to the furnace lining. Improper oxygen blowing, the temperature of the oxygen nozzle is as high as 2100 ℃, if the oxygen flame is blown to the water-cooled furnace wall after being reflected by the large scrap steel, it is very easy to blow out the water-cooled furnace wall. Improper use of the power system may cause serious damage to the refractory due to excessive temperature in the early stage or heating up after the reduction period. Improper implementation of the slag-making system, such as the oxide slag is too thick and thick and the ore is added at a low temperature, the CO bubbles cannot be discharged at the beginning, and then burst out violently. If the slag is too thin for some reason during the reduction period, the arc reflection is serious, and the damage of the furnace lining is easily accelerated. Improper control of chemical composition results in heavy oxidation and overheating of molten steel, which not only prolongs the smelting time, but also reduces the service life of the furnace lining.