What is steel made of?
Iron, the major elemental component of steel, is one of the most plentiful elements in the earth’s crust. All steel alloys are primarily iron and 0.002–2.1 % carbon by weight. In this range, carbon bonds with iron to create a strong molecular structure. The resulting lattice microstructure helps achieve certain material properties, like tensile strength and hardness, that we rely on in steel.
Although all steel is made of iron and carbon, different types of steel contain different percentages of each element. Steel can also include other elements like nickel, molybdenum, manganese, titanium, boron, cobalt, or vanadium. Adding different elements to the “recipe” for a steel alloy affects its material properties. The method of manufacture and treatment of the steel further enhances those abilities.
One notable group of steel alloys contain chromium. All such alloys are known commonly as stainless steel.
How to make steel
At the most basic, steel is made by mixing carbon and iron at very high temperatures (above 2600°F).
Primary steelmaking creates steel from a product called “pig iron.” Pig iron is smelted iron, from ore, which contains more carbon than is correct for steel.
The steelmaker uses a system that bubbles oxygen through melting pig iron. This process creates equal oxidization throughout the molten metal. Oxidization removes excess carbon. It also vaporizes or binds impurities made of elements like silicon, phosphorus, and manganese.
Secondary steelmaking is done “in the ladle.” It is a process of refining and alloying steel. Secondary steelmaking can start by melting scrap, or continues a primary process. Elements can be added to get a specific alloy. The steelworker can also remove surface impurities (de-slagging). The ladle is heated and cooled to the temperatures needed for the necessary chemical processes.
