| Mold flux was a key material to enhance continuous casting efficiency and improve slab quality. Its main functions were controlling heat transfer, lubrication slab, absorbing inclusion of molten steel, avoiding second oxidization of molten steel and heat preservation etc. The lubrication of mold flux achieved through mold flux film between slab and mold. With continuously advance of casting speed, the oscillation frequency of the mold expedited. When the mode of oscillation was stated, the consumption of mold flux decreased and the friction between slab and mold increased. Therefore, it was very important to improve the lubrication of mold flux. Studying film structure, properties of the mold flux film, the lubrication mechanism of flux film and discussing the approach of improving its lubrication, was important significance for optimizing the composition and properties of the mold flux and desinging high quality mold flux.At present, research methods for lubrication of mold flux were divided into two groups. The one was direct measurement, the other was theoretical analysis. Direct measurement was only on-line monitoring of friction between mold and slab. It was direct and effective. Pertinence is strong. But it couldn't forecast, and the cost of trial was expensive, and the risk of the trial was high. By this method the period of designing mold flux was long, and it couldn't describe lubrication of mold flux radically. Theoretical analysis was method of studying the relation of composition, structure and lubrication through establishing calculation model on base of analysis about lubrication mechanism. It was effective means for designing and developing mold flux.In this paper, theoretical analysis model of lubrication was established. By measuring physicochemical properties and analyzing flux film structure and influencing factors, the relation of chemical composition, physicochemical properties, structure and lubrication was studied. Applying heat transfer and transmission principle, considering comprehensively temperature field, flow characteristic and physicochemical properties of mold flux film. The mathematical models for calculation of mold flux film distribution, friction of mold and slab were established. These models could be used to study and evaluate lubrication. Based on distribution and function of flux film, device of mold flux film structure simulation was designed. The structures of different composition slag samples were simulated. The structure of mold flux film by this device agreed with the plant's film structure. It was a new method for study film structure.Through the above methods and means, Properties and structure of different chemical composition slag samples. The effects of chemical composition on high temperature properties and flux film structure were discussed. Making friction as index for evaluated lubrication, the lubrication of mold flux and influencing factors were study. The result was as follow, crystallization ratio decreased with the total thickness increasing.With cooling density strengthened, the thickness of glass increased. When basicity of mold flux increased, crystallization ratio increased, melting temperature and viscosity of mold flux decreased, the thickness of liquid film became thick, the friction between mold and slab decreased. The high basicity was not beneficial to lubrication. With the content of Al2O3 increasing, the friction increased, which was not beneficial to lubrication. With the contents of MnO, Na2O and F- increasing, the friction decreased, which was beneficial to lubrication. But the contents of Na2O and F- must be appropriate amount, more higher or lower were beneficial lubrication of mold flux.
|
PDF Full Text Request