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Metallurgical and tribological aspects for squat formation in the aluminothermic weld HAZ edges of rails welded using aluminothermy

Luiz Henrique Dias Alves (Department of Mechanical Engineering, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil)
Tiago Carvalho Tepedino (Department of Mechanical Engineering, Universidade Federal de Juiz de Fora, Juiz de Fora, Brazil)
Mohammad Masoumi (Center for Engineering, Modeling and Applied Social Sciences, Universidade Federal do ABC, Santo Andre, Brazil)
Gustavo Tressia (Instituto Tecnológico Vale, Ouro Preto, Brazil and Department of Mechanical Engineering, Escola Politécnica da Universidade de São Paulo, São Paulo, Brazil)
Helio Goldenstein (Department of Metallurgical and Materials Engineering, Escola Politécnica da Universidade de São Paulo, São Paulo, Brazil)

Industrial Lubrication and Tribology

ISSN: 0036-8792

Article publication date: 24 July 2020

Issue publication date: 9 November 2020

Abstract

Purpose

The purpose of this paper is to present the results of a metallurgical, mechanical and tribological characterization of the weld and heat-affected zone (HAZ) of aluminothermic welding of premium rails used in heavy haul, looking into the origins of the squat defects associated with rail wear.

Design/methodology/approach

A full factorial design of experiment was carried out for 24 welds of premium and super premium rails. The factors studied were chemical composition, welding gap and preheating time. The welds were inspected visually and by ultrasound to detect superficial and internal defects and characterized by macrographic analysis, hardness profile, tensile tests and microstructural characterization in scanning electronic microscopy. Pin-on-disk test were carried out to compare the tribological behavior of the different regions of the weld rail.

Findings

Squat formation was shown to be associated with spheroidized pearlite regions formed on the HAZ of the welds, presenting near half the hardness of the weld metal. Thermal analysis showed that spheroidized pearlite is a result of partial austenitization at these positions. Tribological tests showed that low hardness regions presented smaller wear resistance than both the weld metal and the parent rail. Tensile test of the whole region resulted in brittle fracture along the weld metal.

Originality/value

The results showed that it is essential to reduce the dimensions of the HAZ and the width of the hardness drop area to mitigate squat formation in the HAZ edges.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0020/

Keywords

Acknowledgements

Authors would like to sincerely thank to Vale SA for the Wheel–Rail chair project.

Citation

Alves, L.H.D., Tepedino, T.C., Masoumi, M., Tressia, G. and Goldenstein, H. (2020), "Metallurgical and tribological aspects for squat formation in the aluminothermic weld HAZ edges of rails welded using aluminothermy", Industrial Lubrication and Tribology, Vol. 72 No. 9, pp. 1123-1131. https://doi.org/10.1108/ILT-01-2020-0020

Publisher

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Emerald Publishing Limited

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