The source of steel is iron ore, that is, the existing form of iron element (Fe) in nature. Pure iron does not exist in nature. Iron ore is mainly divided into magnetite, hematite and limonite, which are all iron oxides. The difference lies in their oxidation mode. The higher the iron content in iron ore, the better. In theory, the highest iron content in iron ore is about 72%, and the iron content above 60% is called rich iron ore. Iron ore is first reduced to iron in the furnace, and then sent to the steelmaking furnace for decarbonization and refining to steel. Scrap steel can also be smelted and regenerated in the steelmaking furnace.