Iron Refining
The process of refining iron has been around since ancient times. Historically, iron ore was smelted or heated to separate the impurities from the metal, resulting in wrought iron and then the more useable steel. Wrought iron is a much softer metal than steel and can be made into a variety of shapes more easily.
Today, most iron is still obtained from smelting ore in blast furnaces, though some is also produced by direct reduction, which is more energy efficient. The process begins by crushing and separating ore into small pieces. This ore is then charged into the top of a blast furnace and heated until it melts and forms a liquid. As the ore is heated, it reacts with impurities in the blast furnace, such as carbon, sulfur, and phosphorus, which combine with the oxygen in the air to form carbon dioxide, sulfur dioxide, and other materials.
These gases then leave the furnace through a stack and are recycled back into the furnace or vented to the atmosphere. The impurities are left behind and settle to the bottom of the furnace as a molten material called slag. The molten iron that remains rises to the top of the furnace and is tapped off into two or more channels called ladles, which hold the molten iron.
The molten iron is then worked in a refinery, a process that involves casting it into bars of various shapes and sizes, such as rods, sheets, and billets. Additional refining and alloying is often done in this stage to create a wide variety of products, such as structural steel, stainless steel, carbon steel, tool steels, and alloy steel.
In some cases, such as when producing certain types of high-end steels, additional refining may be done. This often involves a technique called vacuum arc remelting, which uses electrical arcs to reduce the gases in the molten steel, resulting in higher purity. The molten steel is also often tested for impurity levels, which allows producers to know when the desired levels have been achieved.
Iron refining is a complex and energy-intensive process, but it has been improved over the years. Today, with the help of advances in technology, producers are able to create high-quality steel products in large quantities with greater efficiency than ever before.
