Effect of shear stress on heat transfer behavior of non-newtonian mold fluxes for peritectic steels slab casting

Abstract

A new mold flux based on non-Newtonian fluid for the peritectic steels casting was prepared. The heat transfer behavior and lubrication property of this non-Newtonian mold flux were examined by heat flux simulator, ultraviolet-visible-near-infrared spectrometer (UV-Vis/NIR), Raman spectroscopy, SEM, and confocal laser scanning microscopy (CLSM), and the results were compared with the conventional mold flux used in peritectic steels casting. The results showed that the heat transfer property of liquid layer of N1 slag was reduced through the destruction of silicate network structure by shear stress. Compared with the data obtained under static and stirring conditions, the qmax and degree of polymerization (DOP) of N1 slag were reduced from 0.921 MW/m2, 0.728 to 0.716 MW/m2, 0.583, respectively. However, the shear stress has no effect on the heat transfer property of liquid layer of N0 slag. Second, the heat transfer properties of solid slag layer of N0 and N1 slag were all inhibited through increasing the crystallization rate, crystallization fraction, and slag film thickness by shear stress. While, under stirring condition, the slag film thickness and t2 of N1 slag was lower than that of N0 slag. Third, the heat transfer behavior of air gap layer of N0 and N1 slag were all controlled by shear stress. The surface roughness (Ra) and shedding time of N0 and N1 slag with agitation were increased to 54.49 um, 61 s and 52.87 um, 59 s, respectively. Finally, the break temperature of N1 slag was 9 K lower than that of N0 slag.