To prevent molten steel from sticking to the inner wall of the mold during condensation, reduce friction resistance during billet drawing, improve the surface quality of the billet, and extend the service life of the mold, lubrication of the inner wall of the mold is also necessary in production. Lubrication is the use of liquid lubricants or protective slag with a boiling point higher than the temperature of the inner wall of the mold (about 200 ℃). During the vibration process of the mold, they are continuously brought into the inner wall below the steel liquid level and form an oil gas film or slag film between the steel or billet shell and the inner wall of the mold to lubricate the inner wall.

To ensure good thermal conductivity, sufficient wear resistance, mechanical strength, and hardness of the crystallizer to extend its service life, the inner wall material is mainly made of copper based alloys, commonly used including copper, copper silver alloys (with a silver content of 0.07% to 0.1%), phosphorus deoxidized copper and copper beryllium alloys, chromium zirconium copper alloys, etc. The main purpose of using copper based alloys is to increase their recrystallization temperature, improve their hardness and strength at high temperatures, and extend the service life of the inner wall. In order to further improve the wear resistance and smoothness of the inner wall and reduce the drawing resistance, some even add a coating on the surface of the copper wall. Usually chromium plating or nickel plating, tungsten plating, iron plating, and three-layer nickel plating, nickel phosphorus alloy plating, and chromium plating.