Rail track welding

Gapless Rail Track for Railways, Tramways, Subways and Cranes

History of Rail Welding

The following processes were or are used for producing continuous welded rail for railways, tramways, subways and cranes:
Heating by molten metals
       Cast Welding around 1894        

           — Cast Welding in 1896

           — Cast Welding around 1905
       Thermit welding
           — Alumino-thermics around 1903
           — Thermit in practice around 1905
           — Thermit process around 1910

Mobile flash butt welding machine

© Neil Turner, CC-BY-SA 2.0

Heating by electric currents
       Flash butt welding

       • Arc welding using large batteries of Accumulatorenfabrik AG around 1906

       Puddle arc welding[1]
       Historic special welding processes
           — Thomson rail welding around 1894
           — Johnson rail welding around 1894
           — Thomson rail welding around 1910
           — Compression welding from 1917

Heating by gas flames
       Gas presssure welding (used particularly in Japan)[2]



The following objectives are aimed for during the development an selection of rail welding processes:[3]

  • High quality at high reproducibility
  • Effective energy transfert with a narrow heat affected zone, to minimise the deteriosation of welds by the loads generated by the wheels of the rolling stock
  • Minimised burn-off or melting loss, to increase the applicability of mobile flash butt welding machines

Rail Surface Defects

Rail surface defects are a critical safety concern for railway infrastructure owners, managers and operators all over the world. They lead to poor ride quality due to excess vibration and noise; in rare cases, they can result in a broken rail and a train derailment. They undermine the safety and operational reliability of both moderate- and high-speed trains in passenger suburban, metro, urban, mixed-traffic, and freight rail systems.


Furthermore, the cost of rail replacements due to such defects has become a significant portion of the whole track maintenance costs, especially in European countries, e.g., Austria, Germany, and France.

Defects are typically classified as ‘rail studs’ when they initiate from the white etching layer, and ‘rail squats’ when they initiate from rolling contact fatigue. Due to the high potential damage caused by rail studs and rail squads, several research and development projects have been initiated around the world to investigate the causes of, and feasible solutions to, these defects.[4]

Rail studs

Rail studs initiate from the white etching layer (WEL) due to wheel slides or excessive traction and grow horizontally 3–6 mm below the rail surface.


Rail squats and studs have been observed in all arrays of track geometries and gradients, in all types of track structures, and in all operational rail traffics.[4] 

Rail surface defects: white etching layer (WEL) related rail studs (multiple studs)
©  Andris Freimanis and Sakdirat Kaewunruen, CC BY 4.0

Rail squats

Rail squats propagate from surface cracks initiated by rolling contact fatigue (RCF), and grow at a depth of 3–6 mm below the rail surface.


As a result, the rail surface becomes depressed and passing wheels create excess vibration, noise, and impact loads. This leads to uncomfortable rides for passengers.[4]

Rail surface defects: a rolling contact fatigue (RCF) related rail squat
©  Andris Freimanis and Sakdirat Kaewunruen, CC BY 4.0

Squats are often found in tangent tracks, in high rails of moderate-radius curves, and in turnouts with vertical, unground rails. In cases where impact forces exceed acceptable limits the safety of track components can be compromised.[4]



  1. Crane rail welding and rail steels.

  2. Ryuichi Yamamoto: Japanese research presents new formula for gas-pressure welding. International Railway Journal, 5 November 2018. 

  3. Markus Öllinger: Technologische Fortschritte beim Schienenschweißen (including an English summary), ETR Austria, No 12 December 2015, p. 85-88.

  4. Andris Freimanis<a> and Sakdirat Kaewunruen<b><*>Peridynamic Analysis of Rail Squats, Appl. Sci. 2018, 8(11), 2299; DOI: 10.3390/app8112299, distributed under the terms and conditions of the  Creative Commons Attribution (CC BY) license.
    Birmingham Centre for Railway Research and Education, University of Birmingham, Birmingham B15 2TT, UK.
    Institute of Transportation Engineering, Riga Technical University, Kipsalas iela 6A, Riga LV-1048, Latvia. 


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