Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

Abstract

The brittle layer of carbon brick in a Chinese 4000 m3 blast furnace hearth is investigated in detail, and its formation mechanism is proposed correspondingly. The occurrence form of the brittle layer in carbon brick is characterized by chemical analysis, X‐ray diffraction, and scanning electron microscopy–energy dispersive spectroscopy. The results show that obvious harmful element (K, Na, and Zn) erosion on the sidewall of the blast furnace hearth is observed, in which Zn erosion is dominant. The K2O, Na2O, and KCl produced in the carbon brick by K and Na are the inducement of the brittle layer formation, and the ZnO formed by Zn is the main reason for the brittle layer formation. The thermal stress caused by temperature gradients in carbon brick is greater than its bending strength, which will increase the microcracks in carbon brick. The brittle layer has a lower thermal conductivity due to higher porosity, resulting in a large temperature difference. The resulting thermal stress will aggravate the embrittlement degree.