Types of refractory castables

The strength of granular materials in castables is generally higher than the strength of the hardening body of the bonding agent and the bonding strength between the granules, so the room temperature strength of castables actually depends on the strength of the hardening body of the bonding agent. Changes in strength at medium and high temperatures also occur mainly in the bond hardener, so it can be assumed that the strength at high temperatures is also controlled by the bond.

Most or the majority of the fusible components are always contained in the binder, and the high temperature resistance of a castable will be controlled to a considerable extent by the binder if the material used is of a certain quality in the form of granules and powders. The type and dosage of the binding agent also have a significant effect on the high temperature properties of the castables such as refractoriness and load softening temperature. In addition, the lower high-temperature volumetric stability and lower slag resistance of the castables after hardening are also relevant. Generally speaking, the thermal shock resistance of castables is superior to that of sintered products made of the same material, which is mainly due to the structural characteristics of the hardened body of the castables, which can absorb or buffer thermal stresses and strains.

Calcium Aluminate Cement Castables

Calcium aluminate cement castables are water-hardening castables made of calcium aluminate as the main component of cement as the binding agent, and bauxite clinker as the aggregate and dope. Due to the rapid hydration of calcium aluminate, this castable is characterized by fast hardening and high early strength. But to 350 ℃ began to exclude the water of crystallization, volume contraction, strength decline, so the baking furnace must be strictly according to the predetermined curve. Above 1100~1200℃, the strength of aluminate refractory castables is improved.

Phosphate refractory concrete

Phosphate refractory concrete is a new type of material with good performance formed by phosphate or phosphate solution, refractory aggregates and powders formulated and molded in a certain proportion and cured or barbecued.

Phosphate refractory concrete shall be pre-mixed, piled up and covered with straw bags, and left to stand for 24h before building the furnace, the purpose of which is to exclude harmful gases, to prevent expansion and deformation of the products and to ensure the densification. Phosphate refractory concrete is mainly used in parts requiring high temperature and high strength, and can also be used in parts requiring frequent temperature changes and wear-resisting and scour-resisting, such as the base wall of the heating furnace, cyclone separator, and so on.

Water glass refractory concrete

The main component of water glass refractory concrete is sodium silicate (Na2O-nSiO2). Water glass as a binder, because of its slow hardening at room temperature, generally add sodium silicofluoride (Na2SiF6) as a coagulant.The modulus of water glass used is 3.0, and the density is 1.38g/cm3. Water glass refractory concrete is air-hard, and can be dried directly after molding, and water or steam is strictly prohibited for maintenance.Water glass refractory concrete is mainly used for acid (except oxyfluoric acid) or acidic gas erosion parts, but shall not be used in water and water vapor action parts.

Silicate cement refractory concrete

Silicate cement refractory concrete is made with silicate cement, slag cement and other binder, and clay clinker, waste clay bricks and other aggregates. Silicate cement is a kind of fast-hard high-strength water-hardening binder, so after the concrete is mixed with water, it should be pounded quickly without stopping in the middle so as not to pound poorly. After the rubber mold is covered with straw bags and watered for maintenance. This kind of concrete has a big tendency to crack, baking should be carried out slowly, can be used as heating furnace wall, annealing furnace door, sintering rotary kiln kiln lining, and so on.