The fire-resistant coating forincludes refractory aggregate, carrier (solvent), suspending agent, binder and other additives.
① Refractory aggregate. It is the main component of lost foam casting coating. It has the functions of heat insulation, isolation, anti sand adhesion and reducing the roughness of casting surface. In lost foam casting coating, its mass fraction is usually more than half, which mainly includes zircon powder, bauxite, talc powder, brown corundum powder, quartz powder, Laishi powder, mica powder and other refractory materials. Under normal circumstances, different refractory mineral materials are selected according to different materials of castings. In addition, we should also take into account the prevention of sand sticking and high air permeability. Particle shape determines that it is more conducive to improve air permeability, so a certain number of spherical particles are usually selected in actual production; This is more conducive to the discharge of gas after the sample model is gasified by high-temperature molten metal solution.
② Carrier (solvent). The carrier of casting coating is mainly composed of ethanol and water. For the fire-resistant coating of lost foam casting, it is necessary to consider hanging coating, gas generation, drying, price and other aspects, and use water as its carrier, commonly known as water-based coating. At the same time, the suspension and thixotropy of water-based coatings are relatively good and easy to adjust.
③ Binder. The binder in lost foam casting refractory coating plays a very important role in the strength and adhesion of lost foam casting coating. It not only improves the strength and hanging property of the refractory coating, but also improves the suspension property, but also makes the mold coating have good adhesion, and does not react with the pattern.