The viscous behavior of CaO–SiO₂–15.2 wt% Al₂O₃–4.8 wt% MgO–TiO₂–B₂O₃slags is studied. The effect of the TiO₂and B₂O₃on the viscosity and apparent activation energy, as well as the effect of B₂O₃on structure is investigated through Raman spectroscopy. The viscosity and apparent activation energy of CaO–SiO₂–15.2 wt% Al₂O₃–4.8 wt% MgO–TiO₂are decreased with increased TiO₂content, which can be explained by the network modifier role that TiO₂acts in slags. The addition of B₂O₃can reduce the viscosity of CaO–SiO₂–15.2 wt% Al₂O₃–4.8 wt% MgO–TiO₂–B₂O₃slags, and it brings about a turning point on apparent activation energy curves. Raman spectroscopy shows that B₂O₃acts as acidic oxide and increases the degree of polymerization of slags. However, with the addition of B₂O₃, the appearance of two dimensional [BO₃] structure units and the low strength energy of B–O bonds can reduce the viscous resistance in molten slags and decrease the viscosity.

This paper investigates the distribution of harmful elements in furnace burden and refractory of a water-quenched blast furnace X (BFX) through SEM images, EDS spectra and XRD results. The results show that zinc is mainly concentrated on the lumpy zone while the dominant enrichment region of alkali metal is the cohesive zone. The microstructure and XRD results of refractories in various locations indicate that the erosion caused by harmful elements begins on the hot outer surface of higher stack with the adhesion of zinc, while potassium then completely permeates into the first-layer refractory in the lower part of stack. The local expansion of volume caused by the introduction of harmful elements leads to the erosion of refractory, while the enhanced erosion from the throat to the bottom of the furnace can be explained by the rising temperature. Owing to the shifting location of the temperature isothermal, the harmful elements enrichment region transforms from hot outer surface of refractory at higher part of BFX to the cold inner surface at lower part of BFX.

The evolution of slag phases and interaction between sinter and acid pellet in cohesive zone were systematically investigated, as well as the relationship between microstructure, thermal calculation and S&M behaviour. The results indicate that both ‘component interaction’ and ‘formation interaction’ will be hindered before the formation of liquid phases. The effect of network iron at the interface on the interaction is more apparent than that of the relative position of materials. The main slag phases detected at the interface are FeO–CaO–SiO₂, FeO–CaO–MgO–SiO₂, FeO–CaO–Al₂O₃–SiO₂ and FeO–CaO–MgO–Al₂O₃–SiO₂. The relationship between interaction without load and S&M behaviour has been revealed through breaking down the complex process into the reaction between P–P, S–S and P–S. The main area that affects the pressure drop in cohesive zone is the melting region. Mixed burden is beneficial to enhance the interaction and promote the melting behaviour.

Alkali plays a significant role in the formation of brittle layer of carbon brick in the blast furnace hearth. The brittle layer in a commercial blast furnace hearth was investigated. Large amounts of potassium compounds were found in the brittle layer. Subsequently, the carbon bricks which reacted with potassium in the simulation of blast furnace hearth under different contents of potassium in the brick (0.25, 0.5, 1.0 and 2.0 wt.%) during various reaction times (0.5, 1, 2 and 4 h) were experimentally studied. Finally, the formation mechanism of the brittle layer in carbon brick was clarified. The investigation results show that a large number of cracks are present in the brittle layer. The average potassium content in the brittle layer is 1 wt.%. According to the experimental results, cracks in the carbon brick can be formed by the attack of potassium. The reason for the formation of the brittle layer in the carbon brick is that the liquid potassium permeates into the carbon brick through the pores and cracks, and then reacts with SiO₂ and Al₂O₃ in CO atmosphere. The generated potassium compounds nepheline and leucite lead to the volume expansion and the damage of the carbon brick.