Railroad thermite welding is one of the oldest welding processes there are. It employs a good amount of heat that is produced due to a highly exothermic reaction of metal oxides. This, furthermore, results in a weld of high quality and excellent properties. Thus, some still use it to join long railway tracks.
You can weld in two ways. You can either heat the filler material to join the work parts or heat the actual parts that need to be welded. Once you get forging temperature, you press with force and join them.
Thermite welding can also be applied when making electrical conductive welds like copper. Additionally, a lot of other materials and alloy can be fabricated using this method. Check it out!