Scrapyards might seem like a passing tide except this is the intrigue from which steel is made. It may seem a geek’s job to get down to the basics of how steel is made but while you sanctify yourself so much, you have no clue what the steel manufacturing process entails.
Your rough perception can be big bowels of molten ore, lots of heat and yellow helmets for the muscle industrial workers but the nitty-gritty escapes your grip. Steel manufacturing is far-fetched and this review will help you gain full insight.
What is the Process of Steel Manufacturing?
Steel manufacturing is all about producing steel from two components; metal ore and scrap. The manufacturing process presently in use isn’t the same as the one that was used in the 19th century. Call it steel making, whichever suits you, is diverse but still owes allegiance to the Bessemer process; the cradle of steel making.
The three renowned eras detailing transition and evolution of steel manufacturing are:
- The Iron Era. The Iron Era was precisely psyched to produce cast iron. It first dates back to the 6th century when it was used by the Chinese and later on adopted by the Europeans when it caught their fancy.
The cast iron that was produced in the Iron Era had up to 4.5% carbon. It was generated at high temperatures and this can account for the carbon absorbed while the melting point of the metal decreased. Blast furnaces iconized the Iron Era.
- Bessemer process. You might have figured on your own that the Bessemer process was named after its ideologist. Right after the 19th century when Europe thought the Iron era would hold up its iron industry, it buckled under the pressure of railroads construction.
By this time steel was still to pass the litmus test as a structural metal. No one was willing to indulge in its production because it was a slow and costly affair until Henry Bessemer came up with an alternative; the Bessemer process.
By introducing oxygen into molten iron, the Bessemer process was able to reduce carbon content. This was in 1856 when a ‘converter’ was designed to counter carbon dioxide holding back pure iron.
The converter; a pear shaped receptacle allowed for iron to be heated as oxygen got passed through the now molten metal. Oxygen in turn reacted with carbon in the iron to release carbon dioxide and the result; pure iron.
The Bessemer process was inexpensive as it allowed for carbon and silicon to siphon fast from iron but it had a few defects. Bessemer had to pay his investors because of the deficiency his converter had. While it got carbon out of iron, too much of oxygen remained in the pure iron and this prompted him to find a way to cut down on unwanted oxygen and get more of the carbon.
This defect was resolved by spiegelesen; a compound of iron, carbon and manganese. The manganese compounds in spiegelesen would help Bessemer get rid of the too much oxygen content and this spawned success for his converter.
The Bessemer process is significant to the steel manufacturing process because after 1876 when Phosphorus was rid out of the iron ore, steel could now be manufactured from it. What better way to do it than the Bessemer process. If you look at the years which followed thereafter until 1884, you can attest to the low costs of manufacturing steel.
- Modern steel making. You can mark the debut of this glorious period right after Phosphorus could be removed from pure iron for it to produce steel. Or relatively when the Open Hearth Process came on board.
The Open Hearth process used pig iron to produce steel and if you ask me, this is the debut for the era of modern steel making.
These eras have largely contributed to how we manufacture steel today. Even Chemistry classes implore the Open Hearth process and even though the Bessemer process is less renowned, it has made steel popular as good construction material. If you want to get the whole scope of steel manufacturing, break it down first.
The 6 Steel Making Processes
You need to have blast furnace for this one in order to melt the lime, iron ore and coke. The molten iron you get thereafter is still brittle from the impurities it harbors. This ‘hot metal’ has just about 4-4.5% of carbon.
Steel making involves two primary methods; Electric Arc Furnace (EAS) and Basic Oxygen Furnace (BOS). What separates BOS from EAS is that it adds on recycled scrap to the molten iron in the converter. Oxygen is blown through the molten ore at high temperatures to reduce carbon to up to 1.5%.
The thrill of EAS however cannot be compared to BOS. Using temperatures of up to 1650 ‘C, EAF feeds recycled scrap to melt the iron ore and convert it to high quality steel.
Secondary steelmaking treats the steel produced from both EAS and BOS in order to adjust the steel composition. It is two way; adding or removing certain elements or manipulating the environment or temperature conditions.
There are different types of steel required and secondary steelmaking uses this to consider which of the following processes to apply:
- Composition Adjustment by Sealed argon bubbling with Oxygen Blowing (CAS-OB)
- Ladle injection
- Ladle furnace
This step is the make or break. Continuous casting is responsible for solid steel that is obtained from molten steel after it is cast into a cooled mold. A thin steel shell solidifies thereafter it is withdrawn and fully cooled.
This results into a solidified strand which is cut with length in mind depending on what it is intended to be used for. For instance, slabs for flat products are cut into plates and strips while billets for long products are cut into wires or thin strips.
The cast steel is then formed into various shapes through hot rolling. Hot rolling gets rid of defects to achieve the required shape as well as surface quality.
Manufacturing, fabrication and finishing.
The secondary forming techniques which give steel its final shape are:
- Heat treatment
- Shaping- cold rolling
Steel Manufacturing Process is vast but when cast into 6 procedural steps, it becomes easier to understand what it takes to make steel. It is fascinating how the Bessemer process is paid allegiance too in making steel despite being a late 19th century concept.