Theory and application of “smart mold powders” for continuous casting of steel

The success of the continuous casting process is inseparable from the correct use of mold powders. However, fluoride volatilization and the contradiction between slag entrapment, heat transfer, and lubrication that occurs in the mold restrict the development of green and efficient continuous casting. Through the physical and chemical research of mold powders, Chongqing University found that the intermediate elements of network formation represented by aluminum in the mold powders have remarkable effects of adapting to the working environment of the mold. These effects include: (1) These elements inhibit the degree of ion exchange between the slag and the water and fix fluorine and sodium. (2) They also form a heterogeneous network structure such that the slag produces shear and thinning behaviors and realizes slag viscosity control in different positions. (3) Under the condition of low basicity, aluminum shows a unique thermal diffusion effect, which promotes the transformation of glass slag film to a crystal slag film. On this basis, the design theory of “Smart Mold Powders” for continuous casting, which is referred to as the “SMP” theory, is proposed. This theory was used to develop environmentally friendly non-Newtonian fluids and thermal diffusion effects to mold powders. Industrial application results show that this type of mold powders can achieve environmental friendliness without fluoride reduction, minimize the rejecting ratio of cold-rolled plates, and improve the surface quality of slabs for high-nitrogen stainless steel.