Exothermic Welding

What Does Exothermic Welding Mean?

Exothermic welding is a fusion welding process. Unlike many other welding processes, the source of energy does not come from electricity, combustion or mechanical means. Instead, the energy is obtained from a chemical reaction. The heat from this chemical reaction coalesces two or more materials together.

Exothermic welding creates the heat necessary for welding using the chemical reaction that occurs when aluminum powder is combined with a metal oxide. The two or more materials that are to be combined are placed together with a special crucible. The combination of aluminum powder and metal oxide is then ignited. This sets off the chemical reaction. The heat from this chemical reaction melts the powders. The molten metal flows down the crucible and melts the materials to be welded. Once the chemical reaction is finished, the metal solidifies. The crucible is removed and the slag and excess metal is cleaned up. This is typically done by a grinding process.

Exothermic welding is also known as thermite welding.

Corrosionpedia Explains Exothermic Welding

Exothermic welding is most commonly performed to join rails for railroads. Thick railroad rails would take a long time to weld with other welding processes. Also, joint preparation would have to be performed to ensure that other welding processes could penetrate through the thickness of the rails. Exothermic welding does not require much joint preparation and the actual welding can be performed much faster than most other processes.

The main competitor of exothermic welding is flash butt welding. However, because welding railroad rails requires large amounts of electricity due to their thickness, and since they are almost always in remote locations, exothermic welding is often preferred over the flash butt welding process.