Thermite welding of railways rails

Thermite welding is the final stage in the process, enabling a continuous track to be made from LRS, long electrically welded bars.

The process is easy to set up, and requires few but qualified personnel.

It allows the track to be put back into service temporarily, slowing down traffic for only a short time afterwards; this is particularly appreciated when welding repair coupons.

The process involved pouring liquid steel, formed by the chemical reaction between aluminum and iron oxide grains, between rail ends spaced 25 mm apart and sealed side molds made of refractory material. After solidification, the ingot remelted the two rail ends, making them integral.

This practical, flexible welding method is of good quality, though still significantly inferior to electric welding, and requires a minimum of on-track supervision.

Its ease of use has made it a worldwide success for decades.

It should be pointed out that, with the development of electric welding and its application to long bars, the field of application of thermite welding is expanding on tracks using short rails (25 m as in the USA, Canada, China, Australia), generally mining tracks also requiring more repair rail coupons to eliminate non-tolerable defects.