Case Study: Refractory Wear Mechanisms in Indonesian Steel Plant Castings

Thesis Abstract

This study investigates refractory wear mechanisms in castings from an Indonesian steel plant to address persistent premature failure, reduced lining life, and elevated maintenance costs that threaten plant availability and product quality. The aim is twofold (i) to identify dominant wear mechanisms operating in high-alkali, high-temperature slag environments and (ii) to develop a predictive framework linking material microstructure, operating conditions, and wear outcomes to guide refractory selection and maintenance planning. Specific objectives include characterizing refractory microstructures before and after service using SEM-EDS and XRD, quantifying wear rates and corrosion depths via profilometry and metallographic sectioning across 36 representative refractory samples, evaluating residual stress and thermal gradient effects with finite element thermal modeling, and validating a regression-based model that links temperature, slag chemistry, and phase stability to wear progression. The study adopts a mixed-methods approach within a case study design. The population comprises refractory linings in the steel plant’s blast furnace and basic oxygen furnace (BOF) casting zones, with a stratified sample of 36 refractory blocks collected over 24 months of operation. Quantitative data are obtained from wear depth measurements, porosity and phase fraction analyses, hardness testing, and slag reactivity indices, complemented by qualitative expert interviews with 8 senior process engineers and refractory technicians to capture operational practices and failure interpretations. Data collection instruments include a standardized wear assessment protocol, SEM-EDS for microstructural characterization, X-ray diffraction for phase identification, nanoindentation for local mechanical properties, and thermal imaging for in-situ temperature profiling. Validity and reliability of instruments are ensured through calibration against certified reference materials, inter-laboratory cross-checks, and pilot testing with 4 blocks. Data analysis employs multiple linear regression and ANOVA to quantify relationships between operating variables (temperature, slag composition, thermal cycling) and wear metrics, hierarchical clustering to classify wear patterns, and survival analysis to compare refractory performance across materials. The study will integrate material science theory with corrosion and wear engineering, drawing on Mott–Lawson diffusion-precipitation concepts and canonical slag-refractory interaction models, and will test two theoretical propositions (i) greater thermal-gradient-induced stress accelerates microcracking and spallation in aluminosilicate refractories under high-oxide slag exposure, and (ii) phase stability of multi-component bricks modulates corrosion resistance through protective glaze formation. The expected findings include (a) a ranked spectrum of wear mechanisms (spalling, chemical corrosion, slag attack, and phase transformation-induced softening) with quantified contributions under varying slag chemistries; (b) identification of critical operating windows where wear accelerates and potential refractory substitutions that mitigate degradation; (c) a validated predictive model that estimates remaining service life of linings under real plant conditions; and (d) a material selection map linking brick chemistry, microstructure, and processing to observed wear outcomes. The study contributes to knowledge by integrating empirical wear data from a Southeast Asian steel facility with a mechanistic framework for slag-refractory interactions, advancing predictive maintenance strategies and material design for Indonesian- and regionally similar steel plants. Conclusions are anticipated to emphasize the importance of controlling thermal gradients, optimizing slag compatibility, and adopting multi-layered brick systems with enhanced phase stability. Recommendations include implementing a routine wear-monitoring dashboard, updating furnace operating procedures to minimize rapid thermal cycling, and developing a localized refractory specification that prioritizes phase-stable aluminosilicate composites with tailored porosity and bonding to improve service life under Indonesian operating conditions.