Submerged Entry Nozzle (SEN) are usually made from a combination of carbon bonded alumina, zirconia and magnesia with graphite, which have been found to give the best response to the extreme demands of thermal shock, corrosion and erosion resistance. SEN brittle fracturing and clogging is a serious productivity and quality problem in continuous casting. The SEN critical area of failure is the steel flange where the SEN neck is fixed. Thermal shock or mechanical stress may cause cracking, which can result in premature failure. Preheating on optimal temperature before SEN installation is the standard procedure. Thermal stress effect on fracture behavior was done by analyze of material fractography, morphology, macrostructure and microstructure.