What are the roles of each raw material in ASC castables?
What are the roles of each raw material in ASC castables---- Castable manufacturer, to provide you with a comprehensive understanding of ASC castables.
ASC castable refers to the ASC castable used for the iron ditch. The castable for the iron ditch is generally divided into main ditch, branch ditch, and slag ditch castables, mainly composed of low cement or ultra-low cement castables. Its materials mainly consist of AL2O3 aggregate, SiC, carbon, cement, and various additives. The functions of various raw materials in castables are as follows:
1. AL2O3 aggregate: AL2O3 aggregate is the main component of castable and the particle skeleton that constitutes the castable. AL2O3 aggregates mainly include fused white corundum, brown corundum, sub white corundum, sintered alumina, and high alumina bauxite clinker. When used, comprehensive selection should be made based on the usage conditions of the materials. High grade materials use fused dense corundum, medium grade materials use brown corundum, and low grade materials use sintered corundum or bauxite clinker.
2. SiC: Adding SiC to the castable mainly considers: (1) it can effectively prevent carbon oxidation and improve the oxidation resistance of the refractory material for the iron trench; (2) The expansion coefficient of SiC is low, only half of that of AL2O3, which can prevent cracking during the heating and cooling process of ASC castables; (3) The high thermal conductivity of SiC can improve the thermal shock resistance of ASC castables; (4) The SiO ₂, CO, and CO ₂ produced after SiC oxidation can effectively inhibit the oxidation of materials; (5) SiC can effectively improve the anti erosion performance of materials. However, when the amount of SiC added is too large, the high-temperature strength of the material decreases, so the amount of SiC added needs to be controlled at 10% -25%. Research and on-site use have shown that high SiC content can improve the slag erosion resistance of castables. Therefore, the SiC content of castables often reaches over 20%.
3. Carbon: In AL2O3-SiC-C castable, carbon can prevent the penetration of slag into the interior of the material, confine the slag to the surface of the refractory material, and improve the material's corrosion resistance; At the same time, carbon can also improve the thermal conductivity of materials, improve their thermal shock resistance, and reduce the structural peeling and cracking of materials. Carbon can be added using raw materials such as graphite, carbon black, and asphalt coke. Of course, the effect of carbon in castables is related to the amount of carbon added and the type of carbon raw materials. Carbon is usually added in the form of asphalt balls or coke, with a dosage of about 5%.
4. Cement: The AL2O3-SiC-C castable used for iron trenches usually uses high alumina cement and pure calcium aluminate cement as binders. Adding cement is to maintain the low and medium temperature strength of the material. At the same time, adding cement will introduce a small amount of CaO, which is not conducive to the corrosion resistance of the material; In addition, as the amount of cement increases, the water demand of the castable increases, leading to an increase in porosity, a decrease in bulk density, and a decrease in corrosion resistance. Therefore, the AL2O3-SiC-C castables used for iron trenches are generally low cement castables and ultra-low cement castables, with the total CaO content in the castables controlled below 1.0% -2.5%.
5. Silicon powder (silicon): Adding silicon powder can generate SiC with carbon in the material at a certain temperature. Generated