Steel – what is it and how do we manufacture it?
Most of the time, when we talk of metal, we actually mean steel. It’s one of the most important, most commonly used metals in the industry, forming the backbone of so many structures that if it were suddenly all to disappear, the modern world would crumble to pieces. From healthcare, telecommunications, agriculture, to transport, water and energy – practically all layers of modern society rely on steel to varying degrees. But what exactly is steel and how is it made?
Steel is an alloy that is primarily based on iron, making it a ferrous metal (non-ferrous metals are those that do not contain iron, such as copper, aluminium, magnesium, etc.). The most common definition states that steel is iron that has had most of its impurities removed. Additionally, it has a very consistent concentration of carbon throughout the materials (0.5 to 1.5 percent). Iron only occurs as iron oxides in the earth’s crusts, and so the ores must be converted using carbon. This removes any undesirable components such as silica, phosphorous and sulfur, which can weaken steel tremendously. Because of the fact that all the impurities are removed from it, steel is much stronger than regular iron.
And thus steel is an alloy that needs to be manufactured from another raw material. In order to become steel, iron must undergo certain processes. The first one is, quite obviously, mining. Iron ore needs to be mined from the ground, and as mentioned above, it only occurs as iron oxides on the earth’s crust, which is why this is the form that is worked on. The next step is where all the impurities must be removed and carbon added. In essence, this makes steel “iron alloyed with carbon”, though the carbon component in steel is actually usually less than 1%. The whole process is performed in blast furnaces, with many auxiliary facilities used to support the operations. Temperatures within the furnace can reach well over 1500 degrees Celsius so that the iron can become molten and most of the impurities melt away.