The coil grout is a coating material for the inner surface of a coreless sensor coil. Coil grout should be applied to the inner surface of the coil evenly at a thickness of about six millimeters. Used between the coil can play the role of insulation. Add about 12% to 14% water to achieve smear uniformity. Coil grout coil is used for induction coil of medium frequency coreless induction furnace, In its surface and ramp evenly applied, Play a very good insulation effect, effectively prevent the aging of the coil, and leakage caused by the coil ignition, also effectively prevent the molten steel due to the high temperature caused by the furnace. It is recommended that small repairs be carried out 8 hours before the furnace so as to dry. Large repair or smear the new coil before the day of the building.