To provide you with a comprehensive understanding and understanding of the properties and uses of low cement and ultra-low cement castables
Today, the editor of Henan Chongde Refractory Technology Co., Ltd. will take you to comprehensively understand and understand the performance and use of low cement and ultra-low cement refractory castables?
We all know that refractory castables belong to amorphous refractory materials, which can be roughly divided into ordinary refractory castables, low cement refractory castables, ultra-low cement refractory castables, and cementless refractory castables.
Ordinary refractory castables are refractory castables with a CaO content greater than 2.5%, low cement refractory castables are refractory castables with a CaO content of 1.0% -2.5%, ultra-low cement refractory castables are refractory castables with a CaO content of 0.2% -1.0%, and cementless refractory castables are refractory castables with a CaO content less than 0.2%. Unlike ordinary refractory castables, the matrix of low cement and ultra-low cement uses ultrafine powder with the same or similar chemical composition as the castable material to replace calcium aluminate cement. Therefore, low cement and ultra-low cement castables have the following advantages:
1. The low CaO content in the castable can reduce the formation of low eutectic ideas in the material, thereby improving the refractory, high-temperature strength, and slag resistance
2. The water requirement of castables is only 1/2-1/3 of that of ordinary refractory castables, resulting in low porosity and high bulk density
3. After forming and curing, there is less cement hydrate generated, and there is no problem of a large amount of hydrate damage during heating and baking, which leads to a decrease in mid temperature strength. Instead, as the temperature of the heat treatment unit increases, it gradually sinters and the strength also increases.
The ingredient composition of low cement and ultra-low cement refractory castables is: refractory aggregate, refractory powder, an appropriate amount or a small amount of calcium aluminate cement (delayed hardening agent), and a trace amount of dispersant (high-efficiency adhesive release agent). The particle size composition requires the use of multi-level ingredients, divided into 5-3mm, 3-1mm, 5-3mm, 1-0.2mm, 0.2-0.074mm, 0.074-0.044mm and micrometer levels.
The use temperature of low cement and ultra-low cement refractory castables is higher than that of ordinary refractory castables of the same material. Clay and high alumina low cement castables can be used for lining various heat treatment rotary kilns such as heating furnaces and soaking pits. Mullite based low cement castable can be used for lining various high-temperature burners, as well as for wrapping and lining water-cooled pipes in heating furnaces. Corundum and chromium containing corundum low cement refractory castables can be used as linings for certain components of ladle refining devices, such as integral spray gun linings for jet metallurgy, immersion tube linings for RH or DH vacuum degassing devices, as well as high temperature wear-resistant linings for power frequency induction furnaces and petrochemical catalytic cracking reactors.
AL2O3-SiC-C based low cement castable can be used as a lining for high aluminum tapping channels, cupola tapping channels, and integral powder guns for hot metal pretreatment; Low cement castables made of MgO-AL2O3 or AL2O3-MgO-AL2O3 can be used as lining for steel drums and tapping tanks.