1. Strictly construct the furnace lining working layer and tie the furnace bottom slope
The working layer of the furnace wall is dry-built with magnesia-carbon bricks, which are stacked in staggered ways. The joints between the bricks should be less than 1mm. During the masonry, internal cracks caused by impact must be prevented. Breakage and falling pieces may occur during use, which will affect the service life. The bottom of the furnace and the working layer of the furnace slope are knotted with magnesia ramming material. The first layer of magnesia is laid with an appropriate thickness (about 40% of the total thickness). Use a compressed air vibrating hammer to pound from the furnace edge to the center from the circumference, and then from Pound radially from the center to the edge, and pound each layer 3 times to ensure that the hammers are interlocked and the layers are connected and engaged. The air pressure vibrating fork is used for furnace slope ramming, which relies on vibration to fully discharge the air in the magnesia ramming material to achieve smooth ramming, high density and strong integrity. The slope angle of the furnace is controlled to <45° to facilitate subsequent maintenance. When opening a new furnace with a qualified furnace lining, the furnace bottom should be covered with a thin steel plate to prevent impact damage to the furnace bottom due to charging. At the same time, moisture-proof measures must be taken after the offline masonry is qualified.
2. Prepare the baking and sintering of the new furnace lining
A high-quality furnace lining must have sufficient strength after baking and sintering, and the entire furnace lining must become one. The smelting of the first three furnaces before opening a new furnace is mainly based on baking the furnace lining. All scrap steel is smelted to prevent the impact damage of the furnace lining caused by the molten iron. In principle, the scrap steel is added in 2 to 3 batches, mainly light and thin materials, to reduce the impact of heavy materials on the furnace lining. impact. Using short arc and low power power supply, the secondary voltage is controlled at 45~650V and the secondary current is controlled at 40~45KA. The clustered oxygen lances on the furnace wall use burner mode to blow oxygen and assist in melting. The oxygen flow rate of each lance is controlled below 750Nm3/hr to reduce the impact of high-speed clustered oxygen flow on the furnace bottom. After each batch of materials is melted through the well to form a molten pool, the furnace must be “simmered” for 30 minutes without power, and the temperature of the molten steel is used to ensure the low-temperature sintering and compactness of the furnace lining.
3. Optimize the operating process to reduce corrosion of the furnace lining due to improper operation
Reasonable loading and distribution, and use light and thin materials as the base to prevent the impact of heavy materials on the furnace bottom and slope to cause dents and accelerate the damage of refractory materials. After the basic molten pool is formed during the smelting and melting period, carbon powder should be blown or added to the molten pool through the furnace wall carbon powder spray gun or the fourth feeding hole in a timely manner. The furnace wall cluster oxygen lance should be switched to the oxygen blowing mode, and the furnace wall cluster oxygen gun should be switched to the oxygen blowing mode, and the furnace wall cluster oxygen gun should be switched to the oxygen blowing mode in a timely manner according to the conditions in the furnace. Adjust the ratio of the oxygen flow rate of the three furnace wall oxygen lances to promote the amount of CO gas generated by the C-O reaction, increase the lasting foaming height of the molten slag in the molten pool, quickly realize the foamed slag submerged arc operation, and reduce the erosion of the furnace lining by arc light and high-temperature molten steel. . At the end of smelting, as the C-O reaction weakens, the foamed slag gradually becomes thinner. After the furnace door automatically flows out of the slag, slag materials and light-burned dolomite must be added in time to ensure that the alkalinity of the slag is always controlled between 2.0 and 2.5 and the original ( MgO) content is 5% to 8%, which reduces the erosion rate of the furnace lining. Promote the operation of retaining steel and slag to ensure that 15-20t of steel is retained in the furnace. After tapping, add 500kg of lime to thicken the slag. This not only reduces the impact of the charge on the furnace lining, but also facilitates the early production of the next furnace. Slag with a certain alkalinity reduces the reaction between SiO2, P2O5, Fe2O3 and other oxides existing in free state in the slag and MgO in the refractory material, lowering the melting point of the surface of the furnace lining refractory material and aggravating the damage of the furnace lining.
4. Strengthen later furnace lining maintenance
Later maintenance of the main parts of the furnace lining plays an important role in extending the service life. In the lower area of the furnace wall oxygen lance and the electrode “hot spot” area, strengthened gunning measures must be taken, and the tapping timing and the temperature in the furnace should be taken advantage of for high-temperature quick repair. , Thin patching, the gunning thickness is controlled at 10~20mm to improve the adhesion rate of gunning material and the rapid high-temperature sintering effect. In the later period of use, pay attention to the erosion status of the furnace slope, and promptly use ramming materials to pad the furnace slope to ensure that the angle of the furnace slope is always maintained at about 45° to prevent serious deformation of the furnace slope. At the same time, it is also necessary to prevent improper padding from causing the furnace slope to rise, reduce the molten pool volume, increase the steel water surface, and affect the stability and smoothness of the operation.
Improved usage
During the service life of the furnace lining, it is subject to corrosion damage due to mechanical effects, high temperature effects, chemical erosion and operating processes. By improving the quality of furnace lining masonry, improving operating techniques and strengthening maintenance in the later stages of furnace service, the furnace age has been gradually increased, steadily increasing from 300 furnaces to about 500 furnaces, and has remained stable. The cost of refractory materials per ton of steel has been reduced by 45 yuan. The current price is 22 yuan. The extension of furnace service life and stable use have improved production efficiency, stabilized production order, and achieved good results.