Open Hearth Process

The open hearth process is a steelmaking method that melts pig iron, scrap steel and iron ore together on the shallow hearth of a large regenerative furnace, using preheated air and fuel gas to reach the high temperatures needed while burning off excess carbon to produce steel. The German-born engineer Carl Wilhelm Siemens developed the regenerative furnace design in the 1850s and 1860s, and the French engineer Pierre-Emile Martin adapted it into a working steelmaking furnace in 1865, giving the combined method its alternate name, the Siemens-Martin process. Unlike the contemporary Bessemer process, an open hearth furnace's slower pace let operators sample and adjust the melt's composition during the run, producing more consistent steel and eventually letting the open hearth process overtake Bessemer as the dominant steelmaking technology through most of the first half of the twentieth century, before basic oxygen steelmaking and the electric arc furnace superseded it in turn.