The leakage of blast furnace tuyeres is an unpredictable incident, which happens several times at normal blast furnace operation. The reasons for BF tuyere damages were investigated and the liquid slag and hot metal were found as the main causes of the tuyere burn-out. Investigation was initiated in order to describe the accurate wear mechanism of tuyere erosion due to hot metal and slag. Metallographic tests were performed by analytically analyzing the removed noses of damaged tuyeres. Analyses showed Cu–Fe solid solution formation between tuyere material and the Fe-content of hot metal droplets. A thermodynamic model was prepared for the analysis of the thermal relations between the tuyere and the hot metal drop causing its damage; based on which, it can be stated that the conditions of the formation of Cu–Fe solid solution are given under the blast furnace circumstances.