Evaluation of Solidified Shell Thickness by Thermocouple in Mold

High speed continuous casting technology has been developed to improve productivity. The method of real-time calculation of the solidified shell thickness by using multiple thermocouples embedded in the mold copper plates was tested at JFE Steel Kurashiki No.4CCM, and the possibility of detecting various types of breakouts in high-speed casting was demonstrated. The main results are summarized as follows. (1) The real-time calculation of solidified shell thickness at mold outlet position was successfully achieved on the basis of the local heat flux calculated by two thermocouples, 5 mm apart in copper plate depth direction. (2) The calculated solidified shell thickness was in good agreement with that of the observed by FeS addition. (3) The retardation of solidification was evaluated by the calculation in consideration of heat input caused by the steel stream impingement from the submerged entry nozzle. The index on the narrow face was increased on high speed casting condition in narrow width slabs. (4) The instantaneous local heat flux drop on the thermocouple measurements was observed when the slag rim or scum entrapment to the solidified shell was occurred. The calculated solidified shell thickness at mold outlet position was reduced to about 2/3.