Coil mortar is a kind of coating material for inner surface of coreless inductor coil. It should be uniformly coated on the inner surface of the coil with a thickness of about 6 mm. Use between coils can play an insulating role. Add about 12% - 14% water to achieve uniformity. Coil mortar is used for induction coil of medium frequency coreless induction furnace. It is coated evenly on its surface and ramp. It has good insulation effect. It can effectively prevent coil fire caused by aging of coil and water leakage, and also effectively prevent coil fire caused by high temperature of molten steel. It is s ested that minor repairs should be carried out 8 hours before the construction of the furnace for air drying. Large repairs or new coils are done one day before the furnace is built.            Coil mortar has the characteristics of high strength, high density and high insulation. It is a corundum mortar specially designed to protect coreless induction furnace coils. Coil mortar has good viscosity and is easy to apply. Smearing the smooth surface formed on the coil can buffer the expansion and contraction of the working lining. In addition, coil mud can effectively prevent the leakage of metal melt and protect the coil from metal melt breakdown.