With the deepening of the demand for the degree of refining of molten steel, the residence time of molten steel in the ladle is prolonged, which makes the working conditions for lining refractory materials more stringent; in addition, the scale of steel production and the increase in steel output also further increase the turnover rate of ladles accelerate. These factors lead to a substantial reduction in package age. In order to increase the service life and improve the safety of use, the integral casting process of the permanent layer is adopted to further optimize the lining masonry mode and improve the economic benefits of the enterprise’s production.
1. Material selection and masonry process of the permanent layer
What we use is the 120t steel ladle after capacity expansion. The refractory material and masonry process of the permanent layer has experienced three modes: integral T-4 clay brick masonry, slag line T-4 clay brick molten pool pouring masonry, and lightweight castable integral pouring masonry.
1. Analysis of permanent layer original process
The permanent layer is built with T-4 clay bricks as a whole, that is, a layer of T-4 clay bricks is built outside the insulation layer. Because of the cumbersome masonry process, easy drilling of brick joints, and low service life, it is gradually eliminated. The slag line T-4 clay brick molten pool castables are built, that is, a layer of T-4 clay bricks is built at the slag line, and the molten pool part adopts the castable mode. This kind of masonry mode is carried out in stages: first, install the nozzle seat brick mold and the breathable brick cushion brick, and pour the permanent bottom layer; second, after the bottom permanent layer is hardened, place the breathable brick and the nozzle seat brick, Lay a layer of T-4 clay bricks flat on the bottom permanent layer, and use corundum castables to pour the bottom working layer; third, after the bottom wrap has been cured for 8-12 hours, build a layer of refractory fiberboard along the steel shell, that is, the insulation layer; Fourth, masonry permanent layer, the masonry of permanent layer is divided into two types, that is, overall masonry T-4 clay brick masonry and slag line T-4 clay brick molten pool pouring material masonry; fifth, masonry Working layer and sealing mouth. The advantages of this process are simple process, continuous construction, convenient maintenance, and low cost; the disadvantage is that the brick joints at the slag line are easy to drill steel, and steel cladding is prone to redness and steel leakage, so it is gradually replaced by the integral casting process of castables.
2. Analysis of overall pouring process of lightweight castables
The overall pouring process of the permanent layer: first, install the mold of the nozzle seat brick and the mold of the breathable brick, and pour the permanent layer at the bottom of the cladding; second, paste a layer of hard insulation board along the steel shell, that is, the insulation layer. Place the telescopic castable film of the permanent layer, stir the light castable with a mixer, and cast the permanent layer; third, after the health-preserving demoulding and baking for 8 hours, the working layer is built. Magnesia-carbon bricks are used for the parts; fourth, the nozzle seat bricks, breathable brick cushion bricks and breathable bricks are placed, and a layer of high-alumina bricks is laid flat on the permanent bottom wrapping layer, and the bottom wrapping working layer is poured; fifth, the tank mouth is poured. The characteristics of this process are as follows: First, the weakest part is the brick joint. This process replaces the T-4 clay brick of the original process. The castable vibrates and compacts, which improves safety; It is not easy to be damaged, and the service life is stable at more than 3 contracts; the third is that after the permanent layer is poured, the shape of the inner cavity is standardized, which is convenient for the working layer and the permanent layer to be built closely, and the quality of the masonry is improved; the fourth is that the lightweight castable has a high porosity , small volume density, small thermal conductivity and other advantages, the effect of heat insulation is better, which is beneficial to heat preservation.
2. Use effect
The overall pouring process of the permanent layer of the ladle, after several years of actual operation, has achieved good results. Steel leakage accidents, especially steel leakage accidents at the slag line bricks, have been curbed, and the safety has been greatly improved; the thermal insulation performance has been improved. The slag line part of the original process is about 270 ℃, the molten pool part is about 230 ℃, and the slag line part of the new process is about 240 ℃, and the molten pool part is about 210 ℃; the average service life of the 7 short-term layer is also changed from the original 65 times Increase to 400 times. Calculated on the basis of an annual output of 3.3 million tons of steel, the cost of refractory materials in the permanent layer of the ladle is saved (0.53-0.25)×330=924,000 yuan per year; at the same time, the use of mechanized equipment instead of manual construction reduces labor intensity.
3. Conclusion
The use of permanent layer castables with appropriate physical and chemical indicators and the selection of a reasonable overall casting process have improved the service life of the permanent layer, prevented the occurrence of malignant accidents such as steel breakout at the slag line, improved the safety of use, and enhanced the insulation of the permanent layer. Function, achieved good economic effect, has the value of popularization and use in similar steel mills.