Courtesy attributes such as durability, strength and cost, steel is considered to be one of the world’s most popular construction materials. It’s an iron alloy with 0.2-2 percent carbon content by weight.
The US, China, Japan and India are the top 4 largest steel producing countries in the world – according to the World Steel Association. China, alone accounts for almost 50 percent of this production. ArcelorMittal is one of the top-notch steel barons across the globe, followed by NSSMC Group and Baowu Steel Group and HBIS Group.
Contemporary Process of Steel Production
Since the late 19th-century, the steel production process underwent sweeping evolution; however, the basics remained the same. The original Bessemer process, which depends on oxygen to reduce the carbon content in iron, is still an integral part of modern methods. Today, the production process of steel heavily relies on recycled materials coupled with conventional raw materials, namely coal, iron ore and limestone – and the Basic Oxygen Steelmaking (BOS) and Electric Arc Furnaces (EAF) accounts for nearly all steel production.
Below, we have broken down the six steps of modern steelmaking:
This is the very first step and it involves raw materials including coke, iron and lime – all being melted together in a blast furnace. The resultant molten iron, also known as hot metal still consists of 4-4.5 percent carbon and few other impurities – making it brittle.
This process can be divided into two parts: BOS and EOS, as discussed above. BOS adds recycled scrap steel into the molten iron inside a converter. At relatively high temperatures, as oxygen is blown through the metal components, the carbon content gets reduced to 0-1.5 percent.
Contrarily, the EAF method focuses on recycling steel scrap through powerful electric arcs, where temperatures soar to 1650C and melting the metal to develop high-quality steel.
This method is a combination of BOS and EAF that works wonders in adjusting the steel composition. Certain elements are either added or removed and/or temperature is manipulated. Subject to the kind of steel you need, the following processes can be leveraged:
- Ladle furnace
- Ladle injection
- CAS-OB (composition adjustment by sealed argon bubbling with oxygen blowing)
This process is all about casting molten steel into a cooled mould – resulting in a solidified thin steel shell. Then, the shell strand is withdrawn with the help of guided rolls and left to cool and solidify fully. Later, the strand is cut into specific lengths, depending on use and application.
The steel that is cast needs to be given proper shapes and dimensions. This is where the process of hot rolling comes into the picture. By eradicating cast deficiencies, primary forming helps achieve the desired shape and surface quality.
Manufacturing, Fabrication and Finishing
In the final step, the steel gets its shape and properties. Below are the techniques involved in this process:
- Shaping (cold rolling)
- Joining (welding)
- Coating (galvanizing)
- Machining (drilling)
- Surface treatment (carburizing)
- Heat treatment (tempering)