The fire-resistant coating for lost foam casting includes 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. The mass fraction of lost foam casting coating is usually more than half, mainly including zircon powder, bauxite, talc powder, brown corundum powder, quartz powder, Laishi powder, mica powder and other refractory materials. In general, different refractory mineral materials are selected according to different materials of lost foam 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 lost foam casting coating is mainly composed of ethanol and water. For the fire-resistant coating of lost foam casting, it is necessary to consider the aspects of hanging coating, gas generation, drying and price, and more use water as its carrier, commonly known as water-based coating. At the same time, the suspension and thixotropy of water-based coatings are better and easier 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.