Thermite welding uses molten metal to permanently join iron or steel. Thermite is a composition of 25 percent powdered aluminum and 75 percent iron oxide.
Thermite welds by creating a chemical reaction when a magnesium wire fuse ignites the thermite. The reaction is so strong it can produce temperatures up to 5,000 degrees Fahrenheit in seconds. The thermite melts and is poured into a mold; its heat melts the metals and they become joined. This style of welding is mainly used to join large pieces of metal, such as railroad tracks or ship propellers. Thermite welding was developed in the 1890s by German chemist Hans Goldschmidt.