Thermite Welding

Hazardous. This blueprint is age-gated and it does not run the reaction. Thermite is a genuine energetic material: once started it cannot be stopped, cannot be extinguished with water, and produces molten iron at around 2500 °C that will pass through a concrete floor. What follows is a thermodynamic investigation on paper and a scale — the chemistry is calculated and measured, never ignited.

Almost every welding process carries heat to the joint by electricity or by a flame. Thermite carries it in the reagents themselves. Aluminium has a far greater appetite for oxygen than iron does, so a mixture of aluminium powder and iron oxide, once started, tears the oxygen off the iron and releases enough energy to leave the product iron molten. Pour that iron into a mould around a joint and the joint is welded — with no power supply, no gas bottle and no machine, anywhere in the world.

Hans Goldschmidt was granted German patent DRP 96,317, “Process to manufacture metals and alloys”, on 13 March 1895, and followed it with DRP 116,400 in 1899 for aluminothermic butt welding of rails, which is what the process is still used for today. His original goal was not welding at all: he wanted carbon-free chromium and manganese for alloying, and the heat was a by-product he then found a use for.

That is what makes thermite unusual among welding processes: the energy comes out of a bag rather than a wire — and it is still, in 2026, how continuously welded railway track is joined in the field.