Steel works. Blast furnace at a steel works. Blast furnaces produce iron from iron ore. The raw materials are poured into the top of the furnace, while coke at the bottom of the furnace is heated by very hot air blown in from stove towers. Reactions within the furnace produce molten pig iron and a waste product known as slag. Pig iron is very hard but also very brittle and so is further processed before it is used to produce steel. Photographed at the Mittel Steel USA plant in Indiana Harbour, Indiana, USA.