9th ECCC European Continuous Casting Conference – ECCC 2017

Abstract: Mold heat transfer is important to mold life, surface quality, breakouts and many other aspects of the steel continuous-casting process. Based on a series of related investigation, the mold cooling process on continuous casting slab of high-carbon steel (wC>1.5%) was investigated. Thermodynamic calculation has been carried out on a high-carbon steel by means of Thermo-Calc program. High-temperature tensile tests performed on slab samples was conducted. The result showed that the liquidus and corresponding pouring temperature of high-carbon steel were ~100 oC lower than low-carbon steel, and the high-carbon steel exhibited a wider brittle temperature range immediately after solidification compared with those of low-carbon steel. It is difficult to form a stable liquid flux near the meniscus within a short time at initial stage of casting. The slab samples were observed in situ using confocal laser scanning microscopy (CLSM) in order to simulate various mold cooling process. The result illustrated that homogeneity of initial solidification with mild cooling process in the mold should be improved to reduce the concentration of high-carbon slab surface defects. A hot-top mold, which has a significant effect on heat transfer in continuous casting, has been applied on the present study. Low heat conduction coefficient material that can increase heat resistant and decrease heat flux was coated on hot face of mold in vicinity of meniscus. A heat flux and shell thickness in continuous casting predicted on the basis of an inverse mathematic model were conducted. The temperature of shell rises 10~15 oC with added 1 mm coating on mold by numerical simulation. In plant trial, the temperatures of hot-top mold monitored by thermocouples decrease 5~15 oC with hot-top mold compared with the original mold, as well as the temperature difference of mold cooling water that means average heat fluxes decreases, then the homogeneity of heat transfer and slab surface quality improve. Keywords: Mold Cooling Process; Hot-top Mold; High-carbon Steel; Continuous Casting