1. Selection and configuration of refractory aggregates Refractory aggregates are an important component of low-cement refractory castables, and are usually made of calcined high-quality clay clinker and high-alumina clinker. The maximum particle size of refractory aggregates is determined according to the thickness of the engineering lining. Generally, the maximum particle size is 10mm, and the particle configuration ratio is: 10-5mm accounts for 30%-40%, 5-3mm accounts for 20%-30%, and 3-0.15mm accounts for 30%-40%. In order to achieve a larger stacking density, three-level and four-level grading are usually used, and general materials are rarely used. The amount of refractory aggregate is generally 68%-72%. 2. Refractory powder and its use Refractory powder mainly uses secondary, primary or special high-alumina clinker as raw materials, and should be iron-removed after grinding. The fineness standard is 0.09mm or <0.044mm should be ≥90%. Refractory powder can be used alone or mixed in proportion. Sometimes it is necessary to add high-grade materials such as high-purity alumina powder, white corundum powder or brown corundum powder to enhance the matrix function of low-cement refractory castables. The dosage of this type of powder is generally 18%-25%, and if high-grade materials are added, the dosage is 5%-10%. 3. Types and dosages of refractory ultrafine powders There are many types of refractory ultrafine powders, and the commonly used ones are active SiO2 powder (silica fume), a-A2O3 powder, C2O3 powder, etc., and their dosage is usually 2%-12%. The total usage of refractory powder and ultrafine powder is 28%-32%. Different types of low-cement refractory castables require different dosages of ultrafine powders. The specific dosage needs to be determined through experiments. Generally, the best dosage is 4%-10%. 4. Selection and function of admixtures In low-cement refractory castables, the main admixtures used are high-efficiency water reducers and dispersants, including NNO, MFJN.SM, humic acid, citric acid and tartaric acid and their salts, sodium tripolyphosphate, sodium hexametaphosphate and boric acid, etc., and the usage amount is generally 0.033%-1.0%. When selecting admixtures, they should be compatible with ultrafine powders, and the source of materials, ease of use and cost should be considered. Generally speaking, organic admixtures have better water-reducing and dispersing effects than inorganic admixtures. In addition, expansion agents such as kyanite and sillimanite need to be added to make low-cement refractory castables present a micro-expansion state at high temperatures. 5. Formula examples of low-cement refractory castables After mastering the basic manufacturing principles, a variety of low-cement refractory castables can be designed. For example, the following formula can be used to make high-quality low-cement refractory castables: 70% 8-0mm alumina clinker aggregate, 20% alumina clinker powder of the same grade, 5% 625 CA-50 cement, 5% silica fume, 65% sodium tripolyphosphate and water. The castable has a drying compressive strength of up to 20N, a compressive strength of 70N after burning at 1450℃, and a linear shortening rate of 0.01%. The amount of water used in low-cement refractory castables is generally not more than 7%, the less the better. Through the above steps and principles, low-cement refractory castables can be effectively selected and configured, significantly improving their performance and meeting the needs of different industrial applications.