How is Steel Made?
December 12, 2018
There are some things in life that many of us take for granted, and one example of this is the foundation materials upon which much of our towns and cities are built. Steel is one of the building industry’s most popular metal choices due to its impressive strength and relatively low cost. A metal that has been produced by civilisations across the world from as early as the 6th century BC, modern production methods have made this a very accessible and reliable building block for the modern world.
While the process may have modernised over time, many original techniques can still be seen in modern steel production. Here, we take a rough overview of the steelmaking process used by many in the present day.
Iron Ore Beneficiation
Steel, put simply, is a more refined version of the metal iron, which is commonly mined across the world. Many modern iron furnaces require an ore with at least 50% iron content, which can be found directly in certain minerals, such as Direct-shipping iron-ore (DSO). However, for many mines, the iron ore harvested from the earth has to go through a process called beneficiation, which removes many of the impurities from the rock to help create a material with higher iron content. One of the most common iron ores in the world is magnetite, named for its magnetic properties which make the process of beneficiation considerably easier. Other methods of beneficiation include crushing, milling and even the use of gravity in instances when the density of the iron differs from the density of the surrounding materials. The final product is often moulded into pellets before being shipped from mines to plants.
Here, the process begins to deviate depending on the plant that is producing the steel. It used to be common that specialist manufacturers would receive the refined iron ore and turn it into something referred to as pig iron. Iron ore is cooked with a mixture of limestone and coke, a residue produced when coal is heated without oxygen, resulting in an extremely high carbon content. The two extra ingredients are added at intervals during the process, each helping to create a highly carbonised metal. This is then cooled down into small ingots and sold as the building blocks to the production of different metals, commonly steel. This is useful for small producers; however, many producers now do this all in-house, moving straight onto the next stage without cooling the metal, which has made the phrase somewhat outdated.
Removing Final Impurities
The metal produced during the first stage is rich in carbon and still contains impurities that make it brittle. The final step of steel production revolves around removing the impurities and particularly lowering the carbon level. Steel is, put simply, iron but with a tiny carbon percentage, often between 0.2% and 2%. The amount of carbon, among other factors during this final stage, effects what kind of steel is produced.
Still at high temperatures, most common steel production methods involve blowing oxygen through the metal to reduce the carbon level. The ‘basic oxygen steelmaking’ method also consists of the inclusion of other metals, such as manganese, to remove tougher impurities such as sulphur. Another popular steelmaking method, Electric Arc Furnace, focuses on the use of recycled steel scraps, which are fed through the material at temperatures over 1,500 degrees centigrade to refine the final steel product. During operations like these, the use of protective equipment is of paramount importance – not only is protection for the people in the operation vital, but also the use of high-quality fibreglass insulation to protect other vital components of the manufacturing process.
Turning the metal from its molten state into the final product is a complicated process that works very differently depending on the final product. The most popular method is sand casting, thanks to its ability to be used in the mass-production of large, heavy steelworks and its equal optimisation when used for small, handcrafted materials. The sand is often combined with other materials, such as clay and oils, and results in a clean finish for the steel product.
As mentioned at the beginning, this is only a brief overview of some of the methods currently used to create the metals that support our everyday lives! Our catalogue of high-range temperature textiles are designed to help support the steel-making industry, so if you are looking for superior protection, why not explore our range or get in contact with us today?