Ping Tang

Evolution of Temperature and Solid Slag Film During Solidification of Mold Fluxes

A mathematical model based on one-dimensional transient heat conduction was developed to calculate temperature distribution of slag film during cooling process. Solid slag film was obtained from a water-cooled copper detector, and the evolution of its structure was analyzed according to the calculated results and crystallization behavior of mold fluxes. During formation process of the solid slag film, the cooling rate of liquid slag first increases, and then decreases with time. The maximum value of the cooling rate may exceed 50xa0K/s. Before the solid slag film is formed, the cooling rate of molten slag on the detector side is much higher than that of slag on the liquid slag side. Experimental results indicate that the thermal history of a cooling process has an effect on the crystallization temperature of mold flux. In addition, variation of temperature can also influence the structure of solid slag film since the increase of temperature inside the slag film may lead to the crystallization of the glassy layer.

The Structure and The Crystallization Behaviour of The CaO-SiO2-Al2O3-Based Mold Flux for High-Al Steels Casting

The reaction between [Al] and SiO2 sharply converted the original CaO-SiO2-based flux into CaO-SiO2-Al2O3-based flux during the continuous casting of high-Al steels, promoting the crystallization and deteriorating the mold lubrication. Therefore, study on the structure and crystallization behavior of CaO-SiO2-based and CaO-SiO2-Al2O3-based flux is important to solve this problem. The structure and crystallization behavior were investigated by Raman spectra and the single hot thermocouple technique. The results show that the [AlO4]5- entered the silicate network (CaO-SiO2-based) and the melt converted into the aluminosilicates structure (CaO-SiO2-Al2O3-based), the formation of Al-O-Al linkages and Si-O-Al linkages increased the instability of network structure. From the time temperature transformation diagrams, the strong crystallization tendency and the variety of crystals are mainly the properties of slag film in the CaO-SiO2-Al2O3-based flux. Hence, the improvement of the structural stability and suppression the crystallization tendency of the CaO-SiO2-Al2O3-based flux are key to design a high-Al steel mold flux.