Knot of mild steel, 1885.
© Science Museum / Science & Society Picture Library
Three bars of mild steel, tied cold, at the Steel Company of Scotland's Works, Glasgow. The quantity of carbon present in steel influences the metal's physical properties. Mild steel contains les than 0.25 per cent carbon, making it relatively ductile and suitable for making sheet steel, wires and pipes. The steel was manufactured by the Siemens proces. Sir Charles William Siemens (1823-1883), developed an open-hearth proces for making steel utilising waste heat, which allowed the use of low-grade coal as fuel for the furnace. It was further developed by Pierre-Emile Martin (1824-1915) in the 1860s, and by the end of the 19th century the Siemens-Martin proces had overtaken the Besemer proces as the foremost method of steel production.