Technology Digests / Recent Developments in Thermite Welding Methods

TD26-012

May 28, 2026
Authors
  • Ananyo Banerjee
  • Denise Valdez
  • Kerry Jones
  • John Krasovic
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Key Findings

  • The UIT process has been modified with an improved impact needle design and changes to the peening unit with the goal of reducing treatment time and achieving full accuracy of impacting tight corners on weld surfaces.
  • Shear timing is critical for weld integrity since the removal of heat from the weld and subsequent cooling happens much more quickly in head repair welds than in regular full-section thermite welds. Shearing sooner can cause liquid metal to form hot tear defects and shearing late can lead to incomplete shearing due to solidification.
  • A high flow preheater is being evaluated for its ability to improve surface hardness and toughness of thermite welds via air quenching. The heater is designed to use propane for pre-heating the molds prior to welding and can be used in quenching mode with a preset duration to use surrounding air blown on the weld surface to achieve rapid cooling.

Recent Developments in Thermite Welding Methods

Over the past three decades, MxV Rail has been conducting various tests on thermite welding processes under the Association of American Railroads (AAR) Strategic Research Initative (SRI) program. As a part of the welding research, MxV Rail simultaneously evaluates technologies related to pre- and post-weld processes aimed at improving weld longevity. In the last few years, MxV Rail worked with a supplier to modify the ultrasonic impact treatment (UIT) process and trialed the supplier’s newly designed impact needles and peening unit. Additionally, along with collaborating on evaluating weld surface quench capabilities of another company’s high flow pre-heater (HFP), MxV Rail has been evaluating head repair high hardness welds of two weld kit manufacturers and the issues related to weld shearing. This Technology Digest summarizes findings from the evaluations being done on three thermite welding related processes and next steps coming up on this research. ULTRASONIC IMPACT TREATMENT (UIT) Background The…