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Journal of Metals, Materials and Minerals

Publication Date

2026

Abstract

Railway rails subjected to repetitive wheel-rail contact loads experience surface damage, including shallow cracks, groove wear, and material loss. Conventional arc welding repair presents limitations in costs, repair time, and quality consistency. This study investigates thermite welding for surface repair of pearlitic rail steel grade R260, emphasizing the effects of mold overflow configuration on thermal behavior, molten metal flow, and weld quality. A finite element framework incorporating thermal-fluid coupling was developed to simulate temperature distribution and molten metal penetration. Three mold overflow configurations were evaluated: overflow at the wear groove outer edge (Case 1), near the pouring gate (Case 2), and above the pouring gate (Case 3). The Herschel-Bulkley model captured yield-controlled flow and shear-thinning behavior of molten thermite steel. Numerical predictions were validated experimentally. Case 1 achieved a 1620℃ peak temperature with shallow heat dispersion, causing incomplete fusion. Case 2 reached 1750℃ to 1800℃ but exhibited porosity from unbalanced flow. Case 3 demonstrated optimal performance: 1880℃ peak temperature, uniform thermal distribution, complete groove filling, and minimal defects. Microstructural examination confirmed dense welds with negligible porosity meeting ISO 5817 standards. Strong correlation between numerical and experimental results validates the modeling framework, demonstrating that mold overflow geometry critically governs heat transfer, flow stability, and weld integrity. Case 3 represents the optimal configuration for thermite-based rail surface repair, providing practical design guidance for improving repair efficiency in railway maintenance operations.

DOI

10.55713/jmmm.v36i2.2508

First Page

1

Last Page

10

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