How is Steel Made?
As you may know, steel is a ferrous alloy as it’s a compound of multiple materials, one of which being iron (with the presence of steel being the determining factor as to whether a metal is ferrous or non-ferrous). You may now also be considering how steel is actually made, and perhaps what makes it just so useful.
Here at Mundy Structural Steel, we have a wealth of experience in structural steel construction, so we understand the process of making the metal. That’s why we’ve decided to run you through a basic rendition of the process in our latest blog post below.
Step one is to mine the iron ore, and this is done in many countries throughout the world including India, China, Australia, and Brazil. Sedimentary rocks are also ground up, using a magnetic roller to extract the iron ore.
Interestingly, around 98% of the iron ore mined throughout the world is used to product steel.
Iron ore is mixed with coke, which is a fuel of few impurities and a high carbon content that derives from coal. This mixture, when heated, forms molten iron.
This molten iron needs to now be heated in a furnace to remove impurities and combine different elements to form the correct steel compound. There are two methods for doing this:
Basic Oxygen Process (BOP)
In the basic oxygen process, a furnace is charged using scrap steel (25%) in order to control high temperatures from the exothermic reactions between iron and oxygen. The remaining 75% will be liquid iron.
Oxygen is blasted into this mixture using a lance that is lowered into the molten metal, combining with the compound to remove impure elements like carbon, silicon, manganese, and phosphorus. This causes an exothermic reaction.
Lime is then added to combine with the impurities and form ‘slag’.
This process takes around twenty minutes, after which a sample will be taken to check the chemical composition of the steel is correct. The molten metal will then be passed through a tap hole into a ladle for transporting to casters.
If changes to the compound are required, the secondary steel production process will begin.
Electric Arc Furnace (EAF)
The electric arc furnace uses high current electric arcs to melt steel scrap and convert it into a liquid metal. First, the scrap steel is loaded into the EAF from overhead and the lid is lowered, which contains the electrodes that will form the arc.
An electric current is passed through the electrodes in order to form the ar, where the heat generated melts the scrap steel. Other metals may be added at this point if a specific alloy is desired.
Once melted, once again, oxygen is blasted in to purify the molten metal. Lime and fluorspar are then also added to combine with the impurities released by the oxygen and form slag.
A sample of the material is taken before eliminating the slag to check the chemical composition where, if correct, it is then ladled and transported to a caster.
In the final stage of the process, the liquid metal is passed through casters and formed (usually) into one of three shapes – a slab, a bloom, or a billet. These shapes are the primary forms of the steel, and will likely later be melted down into a specific shape for the job requirements.
Slabs are usually rolled into flat products like plates.
Blooms are generally later formed into structural shapes like beams.
Billets are for the production of bars and rods.
The Bessemer Process
This process is internationally recognised as the most common method for producing steel and was pioneered as the Bessemer Process – or the first, affordable method for producing steel – by Sir Henry Bessemer in 1856.
In simple terms, the process for creating steel is by alloying iron with carbon (less than 1%, which comes from the coke) and removing impurities.
Mundy Structural Steel
If you would like to hear more about our structural steel fabrication and erection services here at Mundy Structural Steel, please contact us by calling 020 8818 6930 or filling out our simple contact form.