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Cyber Smiths Int.
Edition 42 - Page 2 of 25 September 30, 2008

SOFA 2008 - Thermite Welding RR-Rail

A crew from Railtech Boutet, Inc. put on the top attended demonstration at Quadstate 2008. The thermite process invented in 1908 was once used for many repairs including foundry castings. Like welding rod the material could be purchased in various specifications. Today thermite is only used for welding rail and heavy duty electrical lugs.

Thermite produces liquid metal by the burning of aluminium powder mixed with an oxide of the metal to be cast. The burning aluminum strips the oxygen from the metal oxide leaving behind super heated metal. In welding steel iron oxide is used along with manganese, steel alloy and other materials in order to match the chemistry of the rail and produce a strong joint of equal hardeness.
Thermite Rail welding tools
ABOVE The Railtech rail welding setup. Steel mold frames support the biodegradable one shot mold. On top is a brick of sealing clay used like daming compound. The mold and crucible are sand with an organic binder.

A special adjustable fixture supports the large oxy-propane rosebud used to preheat the rail and mold.
Thermite Rail welding tools
Packing the sealing clay around the mold where it fits the track and where the mold halves fit together. The premixed clay is exactly the right consistency (like modeling clay) for hand packing. Track welders are allowed a limited time to setup and complete a weld so they work in a team of two. Each has their assigned jobs and must move quickly.
Thermite Rail welding tools
Preparing to preheat the rail. A large (about 2") propane rosebud torch is used to preheat the rail. Preheat time is 6 to 7 minutes at a specific torch setting. . . much more . .
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September 30, 2008
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