Steel is one of the most commonly used materials in the world and is a primary ingredient for practically everything from infrastructure to construction and even shipbuilding. Strong, versatile, flexible, and corrosion resistant, it’s used in practically every application you can think of. However, steel wouldn’t exit without raw materials such as iron. This leads us into the question “How do you turn iron into steel?”
There are several processes which can be used to turn iron into steel, but the two most common methods are by using electric arc furnaces and oxygen furnaces.
Ingredients used in steel production
Depending on the method used, different ingredients are needed, although that said, there are 4 ingredients which are widely used in steel production:
While we know that iron is used in the production of steel, coal is the main ingredient which forms steel. The ideal coal should have low sulphur and phosphorus properties. To purify the coal and turn it into the porous, high carbon substance which we know as coke, the coal has to be heated at a temperature in excess of 1000˚C.
Differing grades of steel require for different elements to be added into the mix. These can include nickel, vanadium, manganese, chromium and boron, which each have their own purpose.
This is a type of cleaning agent which, when added to the furnace, removes trace impurities such as phosphorous. This agent helps to draw out any trace impurities contained in the liquid slag, where often it’s possible to re-use it. Common substances used for fluxes include fluorides, inorganic chlorides, and limestone.
To create pig iron from the raw material which can be used, iron ore, coke, and small amounts of flux to draw out the impurities, are fed into a blast furnace. The furnace is then blasted with hot air at a temperature of about 1200˚C. This makes the coke burn, which in turn produces carbon monoxide, which then reacts with the raw iron. Finally, the impurities are drained into the liquid slag, before the melted pig iron.
Electric Arc Furnace
Also known as a mini-mill, the electric arc furnace recycles existing steel rather than processing raw iron. This particular method uses very few raw materials and because of this, is a good method of re-using materials. Scrap steel, and where necessary pig iron or DRI (Direct Reduced Iron) is fed into the furnace. The heat comes from 2 electrodes which create an arc of electricity through the scrap metal. It takes around 33 million watts to heat the scrap to a temperature of 1600˚C, which forms molten steel. Again, flux is used to skim any impurities and drain them into the liquid slag.
This is one of the most common methods of making steel. In this method, the pig iron is combined with scrap steel (roughly below 30%) together with a small amount of flux. Oxygen is then blown into the furnace raising the temperature to an excess of 1700˚.
The pressurised oxygen reacts with the pig iron (containing high levels of carbon) and the scrap, forming CO in addition to CO2. The oxygen also causes the flux to react with the different impurities to form the slag layer, or, alternatively, it oxidises and leaves through a vent at the top of the furnace. The flux is then drained to leave molten steel behind. Depending on the steel’s purpose, secondary procedures may take place and, in addition, other elements such as nickel and chromium are added to create various steel alloys.
If you’re considering any type of steel construction project and need advice, then please get in touch with the experts, here at Metro Steel. We’re happy to answer your questions and help you find the best solution for your needs. Call us today on 07 3204 1000.