Thermic welding is the process of seamlessly welding streetcar and railroad tracks. It is also known as the Goldschmidt Reduction process.
It was introduced by Johann ("Hans") Wilhelm Goldschmidt in 1895 when he patented the process in Germany under the corporate name of Goldschmidt AG. Goldschmidt AG is now part of the Degussa group of chemical companies [1].
In this process, thermite, a mixture of aluminum powder and iron oxides react to produce intense heat and molten iron that is used to fuse together the rails.
References
Thermic welding Wikipedia(Text) CC BY-SA