Surface roughness of solidified mold flux in continuous casting process

Heat transfer in continuous casting mold is important to decide the surface quality of the cast slab of middle carbon steel. Many researchers have rec ently studied the mechanism of reducing the heat transfer between the mold and the solidified shell, and some of them have pointed out that the interf acial thermal resistance between the mold and surface of solidified mold fl ux has caused decreasing heat transfer. In the present study, the surface roughness of solidified mold fluxes used for low carbon and middle carbon steel casting, Na2O-CaO-SiO2 and Li2O-CaO- SiO2 slag systems, was measured by a confocal scanning laser microscope com bined with an infrared image furnace. It was found that the surface roughne ss was in the range of approximately 10-30 mu m when the crystalline phase precipitated. Furthermore, the faster the cooling rate, the smoother the su rface roughness of the solidified mold flux became. In the contrast, the su rface roughness of the slag, of which critical cooling rate is faster, incr eased. The surface roughness of the mold flux for middle carbon steel casti ng became rougher than that for low carbon steel casting. As a result, the surface roughness was related to normalized cooling rate, which is the rati o of actual experimental cooling rate to critical cooling rate. The experim ental data of surface roughness were fairly in agreement with calculated va lues on the assumption of one dimensional heat transfer in the continuous c asting mold.