Fundamental Design of Steelmaking Refractories

2 Equilibrium and Nonequilibrium Phases

2.1 Introduction

A phase diagram study is mandated to synchronize material formation at a specific temperature, pressure, and composition. Several experimental data represent the temperature and composition limits of two or more stable constituents at different phases. Efficient heat distribution in a kiln or furnace can facilitate the desired equilibrium phase during refractory manufacturing, eventually fulfilling steel industry demand. However, any nonfavorable conditions may develop nonequilibrium phases that reduce refractory performance. For example, high-temperature refractory–slag interaction expedites the glassy phase during the steelmaking process.

There are multiple binary and tertiary equilibrium phases from refractory compositions and slag chemistry, and significant phases are represented in Figure 2.1. Not all phases are formed in one product or single contact zone; instead, these are often in a wide span of refractory products and steel processing starting from BOF to Tundish operation. Some essential and valuable explanations from the perspective of the ceramic systems are summarized to analyze the failure of refractories. Despite these combinations, there are also possibilities to form several phases in the presence of other oxides or different mixtures of oxides; such incidences are discussed in relevant chapters as required.

Figure 2.1 Major working lining refractory crystals are in the light shade zone; relatively low ...