Steel And How It Is Manufactured
Steel is an alloy made primarily from iron that has been manufactured and used for thousands of years. The oldest piece of steel ever found dates back to around 1800BC, and was unearthed in an archaeological dig in Anatolia (which comprises most of modern-day Turkey). Other ancient samples have also been found in East Africa, and these have been dated to around 1400BC. Accordingly, steel is one of the oldest smelted alloys known. It was used by the Chinese and the Roman military in pre-biblical times for weapons, though the steel industry as we know it today has its roots in the 19th century, starting with the development of the Bessemer converter and Bessemer process (a process capable of producing steel in large quantities).
Modern steelmaking is a far cry from the older, more expensive and complicated methods that were used prior to the development of the Bessemer process. There are two different kinds of steelmaking, primary and secondary, and they are defined by the type of iron that is used as the feedstock. In primary steelmaking, new iron is used, and in secondary, scrap steel is recycled.
The first step in making steel is always smelting the iron ore, to produce a material known as pig iron. Doing so usually involves using a blast furnace to separate the oxygen from the iron ore (which is comprised of iron molecules bonded with oxygen molecules). Once this is done, the resulting pig iron undergoes a process known as basic oxygen steelmaking. It has a variety of other names, including Oxygen Converter Process and Linz-Donawitz-Verfahren steelmaking. This method involves blowing oxygen through the molten pig iron to capture some of the carbon present in it, and remove it from the mixture. This results in the production of low-carbon steel, or mild steel, which are forms of steel with a low tensile strength. They are cheap and shapeable, and are suitable for a number of purposes. There are a variety of other steel types, based on their carbon content, from the aforementioned low-carbon steel up to ultra-high carbon steel. The malleability of steel decreases as its carbon content increases, so the ultra-high variety is often used for punches or knives.
Steel is often heat treated after manufacturing, to further suit it for whatever purpose for which it is intended. A large number of different types of heat treatment exist, including normalizing (to increase steel strength), quenching (to increase it even further) and spheroidizing (to soften high-carbon steels). There are several other things steelmakers can do to change the physical properties of the steel, also, including adding extra elements such as vanadium, nickel and chromium.
Steel, once manufactured, is shaped into pieces ready for distribution. A piece of steel ready to be sent out is called a steel merchant bar, and it can exist in several different shapes; the pieces can contain corners, be rounded, and also be different lengths and thicknesses. Thanks to the nature of the modern steelmaking industry, any requirement can be fulfilled, resulting in the many varied and diverse uses of steel we see today.