Aluminothermic Welding
An exothermic fusion welding process where a chemical reaction between iron oxide and aluminum provides the molten filler metal. It is primarily applied for continuous joining of railway tracks.
Aluminothermic welding runs via a strongly exothermic reaction between aluminum and iron oxide. This produces liquid iron that fills the parts to be joined form-fit and thus creates the joint. The liquid iron is the filler material that forms a metallurgical bond with the base material. It is important that the reaction runs completely. If you use too little aluminum or iron oxide or the starting materials are damp, you get slag and no clean melt. The result is a porous or incomplete weld that holds significantly less than the base material. In practice, this means: align the mold cleanly, store the material dry, and ignition must happen quickly and controlled. Once the reaction is running, it can't be controlled anymore – so you have to have everything properly prepared beforehand.