Wettability-Enhanced SiC–Graphite Synergy in Al2O3-SiC-C Castables: Carbon Resource Comparation, Sintering Response, and Latent Rheology Effects

TL;DR

This study explores how SiC-modified graphite affects the performance of refractory castables used in blast furnaces, focusing on mechanical properties and erosion resistance.

Contribution

The novel use of SiC-modified flake graphite in refractory castables is explored, revealing microcrack-toughening effects and improved wettability.

Findings

SiC-modified graphite generates microcracks that enhance mechanical properties through crack deflection and matrix pinning.

Modified graphite improves wettability and oxidation resistance but only provides limited net improvement in erosion resistance.

A 1 wt.% modified graphite formulation showed optimal performance and an unexpected water reduction mechanism during trials.

Abstract

Research on raw materials for Al2O3-SiC-C refractory castables used in blast furnace troughs is relatively well established. However, gaps remain in both laboratory and industrial trials concerning the performance of castables incorporating SiC-modified flake graphite and alternative carbon sources. This study investigated the sintering behavior, mechanical properties, and service performance of Al2O3-SiC-C castables utilizing varying contents of modified flake graphite, pitch, and carbon black as carbon sources. Samples were characterized using SEM, XRD, and EDS for phase composition and microstructural morphology analysis. Key findings revealed that the thermal expansion mismatch between the SiC coating and flake graphite in SiC-modified graphite generated a microcrack-toughening effect. This effect, combined with the synergistic reinforcement from both components, enhanced the mechanical properties. The SiC modification layer improved the wettability and oxidation resistance of the flake graphite. This modified graphite further contributed to enhanced erosion resistance through mechanisms of matrix pinning and crack deflection within the microstructure. However, the microcracks induced by thermal mismatch concurrently reduced erosion resistance, resulting in an overall limited net improvement in erosion resistance attributable to the modified graphite. Specimens containing 1 wt.% modified flake graphite exhibited the optimal overall performance. During industrial trials, this formulation unexpectedly demonstrated a water reduction mechanism requiring further investigation.

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