From clay bricks, high-aluminum lightweight bricks, high-alumina bricks to various low-cement and high-aluminum castables or ramming materials, the service life of the permanent lining of ladle is also continuously improving. With the development of out-of-furnace refining technology, it is becoming more and more important to reduce the temperature drop of molten steel in the ladle. Since October 1987, the second steelmaking plant of Tangshan Iron and Steel Company and the first steelmaking plant of Anshan Iron and Steel Co., Ltd. adopted the lightweight high-strength castables developed by the Beijing Institute of Construction and Research of the Ministry of Metallurgy for the permanent lining of 110t ladle. But its durability is not ideal. Refractory fiber insulation panels (approximately 25mm between the steel shell and the permanent layer) began to be promoted in 1996. The temperature of the outer wall of the ladle has been significantly reduced, but the service life of the permanent lining has not increased, but has shown a downward trend.
The ladle adopts refractory fiber insulation board, the temperature of the outer wall is obviously reduced, but the service life of the permanent lining is not increased, but the reason for the decline is: the production of high-density refractory fiberboard is to add a certain amount of fine powder to the refractory fiber after dispersion or secondary immersion Silica sol, economical pressure dehydration compression molding, about 20% of the solid residue of the glue is deposited in the material, after drying or heating, the density is between 0.6~0.85g/m3, and the compressive strength (25% depth of reduction) Between 0.8~1.4MPa, and the linear shrinkage rate is very large, -2%~-5%. The strength of refractory fiber decreases significantly at the dew point or in the presence of steam, and is accompanied by irregular network corrosion. Moisture or water vapor enters the refractory fiber, the fiber product has a high water absorption rate, and the fiber rod is infiltrated and thickened. After drying or heating, the compressive strength is only 0.2~0.6MPa, and the surface is corroded by the irregular network. The layer is rough and uneven with great shrinkage.
Dew point is to reduce the temperature of unsaturated steam to make it become saturated steam. In the clad wall refractories with acid-base binders, the dew point temperature is between 80 and 150°C. If the castable is mixed with water or the mud masonry is mixed with water, the water vapor produced is about 100°C. In this way, when baking (when baking against the wall of the package), the direction of the water vapor or moisture overflow is opposite to the parallel direction of the high temperature surface, and it must pass through the refractory fiber insulation board. Due to the frequent erosion of water vapor or moisture, the strength of the refractory fiber heat insulation board continues to decrease and shrink, and there is actually a certain gap between the permanent layer and the steel cladding shell. The space distance of the thermal insulation layer on the unstressed furnace wall can remain unchanged, but when the ladle wall is stressed each time, especially under the squeezing force of the unpacking machine, due to the existence of the permanent layer and the steel shell In a certain space, after the force is applied, an irregular final crack will penetrate.