The Composition and Production Process of Steel

Steel is one of the world's most essential engineering and construction materials, widely used in automobiles, buildings, household appliances, ships, medical instruments, and more. Fundamentally, steel is an alloy of iron and carbon, typically containing less than 2% carbon, around 1% manganese, and trace amounts of silicon, phosphorus, sulfur, and oxygen. Its production begins with the extraction of iron from iron ore by removing oxygen and impurities, followed by smelting with carbon and recycled steel to form steel.

Currently, steel production primarily relies on two process routes: the blast furnace-basic oxygen furnace (BF-BOF) method and the electric arc furnace (EAF) method, which differ in raw materials and energy consumption. The BF-BOF route accounts for about 70% of global production, using iron ore and coal as primary inputs. The process first reduces iron ore into molten iron (pig iron), which is then converted into steel in a BOF before being cast and rolled into products like coils, sheets, or bars. In contrast, the EAF route, making up roughly 30% of production, primarily melts recycled steel using electricity and can supplement its feedstock with direct reduced iron (DRI) or other iron sources. Chemical composition is adjusted through alloying additives, and oxygen may be injected to enhance refining.

Additionally, the open hearth furnace (OHF) method, an energy-intensive and environmentally disadvantageous process, now represents only about 0.4% of global steel output and is gradually being phased out.

Since steel products often remain in use for decades before recycling, EAF production alone cannot meet the growing global demand. A combination of BF-BOF and EAF methods ensures a balanced supply. Both production routes can incorporate recycled scrap steel as raw material, but integrating ore-based smelting with recycled resources is key to achieving efficient and sustainable steel production.