To reduce refractory lining consumption in ladles, what measures should be taken?

　　We have implemented numerous measures to reduce ladle brick consumption. In ladles containing steel, the addition of aluminum silicate powder or silica sand, chromite ore, lime, dolomite, etc., directly to the slag surface can fundamentally reduce lining damage. However, the composition and quantity of additives should be calculated, and the outcome should be analyzed in advance. To ensure that the slag reacts with the additive materials first, rather than with the lining material, the chemical potential difference between the refractory lining and the slag must be smaller than that between the additive and the slag.

　　Two methods are industrially used for monolithic silica (quartz) linings: using semi-dry powder materials, with a projection device assisting in ramming the lining, and using fluid slurry, with a casting method.

　　For a quartz lining to function smoothly, it must be rapidly heated to the quartz melting temperature. This heating occurs due to heat transfer from the filled 1620~1700℃ steel to the preheated 600~700℃ lining. This rapid heating transforms β-quartz into α-quartz, which immediately transforms into quartz glass (fused silica). At 1720℃, the viscosity of quartz glass is such that its state is close to the viscosity of the corresponding refractory material (refractoriness is determined using a standard pyrometric cone). The pores are almost completely filled with the quartz glass melt. Thus, a monolithic quartz glass layer is formed on the lining surface. Uneven wear is usually observed. Examples of actual wear rates are listed in Table 11-3.

　　Service life depends on the greatest wear. When the rammed or cast layer thickness is 200mm, it is approximately 200/10-20 heats. Applying a more stable slurry, such as one containing chromite or zircon, to areas with severe wear can reduce uneven wear.

　　According to reports, a certain steel company described the impact of lining service conditions on the service life of its 180t ladle using a formula.

　　Where y is the average service life of the monolithic lining, heats; x is the heat preservation time of the metal in the ladle from the converter tapping to the start of casting, min; xz is the total residence time of the metal and slag in the ladle, min; x is the slag basicity; x is the metal temperature at the time of tapping from the converter, ℃; xs is the low iron oxide content in the slag, %; x6 is the thickness of the upper part of the monolithic lining, mm.

　　The service life and economic efficiency of quartz linings using the casting method are, like the ramming method, sometimes greater than the service life of linings built with clay bricks. Extensive practical application has shown that with intermediate repairs, the service life of monolithic ladle linings can reach 30-40 heats.

　　Spray patching of ladle linings is an effective method for improving service life. Table 11-4 shows a comparison of sprayed and unsprayed monolithic ladle linings.

　　When smelting high-quality steel, the use of monolithic linings does not increase non-metallic inclusion contamination.

　　A further measure to improve the service life of monolithic linings is the use of alkaline slurries. They are more stable than quartz slurries against alkaline slags. However, there are also problems: the higher thermal conductivity causes agglomeration, while the high thermal expansion causes delamination of the lining from the permanent layer. Solving these difficulties requires, to some extent, the use of appropriate lining structures. A schematic diagram of the ramming of alkaline materials in a 320t ladle lining is shown in Figure 11-9.

　　A heat insulation layer is built between the double-layer permanent masonry of the wall and the shell. An alkaline lining structure is introduced, where the composition of the surface of the rammed layer is: MgO 78%, Al2O3 %, and SiO2 2%, with periodic buffering of the heat insulation layer using cold spraying. The development direction of manufacturing alkaline monolithic linings is to utilize magnesium silicate materials, such as fired dunite, combining them with fibers or other insulating materials. Experiments have been conducted with tar-bonded alkaline refractories and magnesia-calcium refractories.

　　In the past, China's ladle linings also used clay bricks for a long time. In the past 20 years, more attention has been paid to the development of ladle lining materials, and China's ladle linings have undergone several changes. First, to improve corrosion resistance, clay bricks were replaced with high-alumina bricks, significantly improving the service life of large ladles. Some steel plants have tried using forsterite bricks and rammed quartz monolithic linings. Because these materials have slight expansion and good integrity at operating temperatures, they do not stick to slag, but their corrosion resistance is poor, and their service life is not long. However, this provided inspiration, suggesting that ladle linings must have good integrity at operating temperatures, using materials with slight expansion at high temperatures. To alleviate the thermal shock of high-temperature steel, there should be a certain amount of liquid phase in the material at high temperatures. Therefore, unburned magnesia-alumina bricks and magnesia-alumina ramming materials are used. To improve corrosion resistance, magnesia-alumina carbon bricks have also been developed.

　　Currently, small and medium-sized ladles widely use castables based on natural high-alumina clinker, with added magnesium aluminate spinel, magnesia powder, and silica micropowder. Their service life is generally over 100-200 heats. Large ladles (300t) in plants like Baosteel use castables based on corundum, with added magnesium aluminate spinel, etc., achieving a service life of over 250 heats.