Furnace to Forge: How Steel Is Made
15 Aug 2025
Steel’s everywhere. From bridges and buildings to brackets and bikes – this stuff holds the modern world together. But what is steel made of? And how does steel form into beams, bars and sheets strong enough to hold up a skyscraper?
It’s not as simple as melting down scrap and hoping for the best. Steel is made through a precise, high-heat process that turns raw earth into something dependable and durable.
Here’s a straight-talking guide to how it all works – from furnace to forge.
Article in brief
Steel starts with iron ore, coke and limestone
It’s melted in a blast furnace to create ‘hot metal’
The metal is refined, purified and alloyed to create different grades
The steel is cast, shaped and rolled into usable products
Finishing processes like galvanising or machining prep it for end use
1
What is steel made of?
So, steel is made of what, exactly? It starts with three core ingredients:
- Iron ore – Dug from the ground, it’s a mix of iron and other minerals
- Coke – A carbon-rich form of coal used as fuel
- Limestone – Helps remove impurities during melting
These get dropped into a blast furnace, where hot air is blasted in from below – hence the name. Temperatures rise above 2,000°C. The coke burns, melts the ore and the limestone binds with impurities to form slag. That slag floats and is skimmed off.
The resulting molten iron – known as hot metal – is poured into huge containers (called torpedoes) and taken to the steel plant.
2
Primary steel manufacture (BOS or EAF)
Steel can be made in two main ways at this stage:
Basic Oxygen Steelmaking (BOS)
The traditional route for large-scale production from iron ore.
- Hot metal is combined with scrap metal
- High-purity oxygen is blasted onto the surface via a cooled lance
- Lime is added again to form a new slag, removing more impurities
- This removes elements like carbon and sulphur, producing clean molten steel ready for alloying
Electric Arc Furnace (EAF)
- Primarily uses scrap steel (and sometimes direct reduced iron) as feedstock
- An electric arc from graphite electrodes melts the metal in minutes
- Alloying and refining happen inside the furnace or in ladle stations
- Favoured for flexibility, smaller batch sizes, and high recycled content
Both BOS and EAF produce high-quality steel, but the choice depends on raw material availability, product requirements, and energy costs. Globally, BOS still dominates, but EAF accounts for roughly 30% of steel production – and is the main route for turning scrap into new steel.
Energy and environmental footprint
Both BOS and EAF steelmaking demand substantial energy. BOS relies heavily on coke (a coal product), producing high CO₂ emissions. EAF uses electricity (often from fossil-fuel-based grid) which can also generate significant emissions, though using renewable power can greatly reduce its footprint.
Because steelmaking is one of the largest industrial sources of CO₂ worldwide, recycling scrap, improving efficiency, and exploring alternative production methods (like hydrogen-based reduction) are critical for reducing environmental impact.
3
Secondary steel manufacture
Not all steel grades are created equal. Some jobs need ultra-high strength. Others need to bend without snapping. That’s where secondary steelmaking comes in.
At this stage, the steel’s chemistry is fine-tuned:
- Carbon levels are adjusted depending on strength or ductility needs
- Aluminium may be added for deoxidation
- Gases are removed via vacuum processing
- Temperature is closely controlled for casting
All of this ensures the steel meets strict standards for things like structural strength, weldability and resistance to cracking.
4
Continuous casting (Concast)
Now we move from molten to solid.
The refined steel is poured – or teemed – into a continuous casting machine, where it begins to cool and solidify. Depending on the shape, the cast steel becomes:
- Slabs – For sheet and plate
- Billets – For rods, bars and wire
- Blooms – For structural beams and heavy profiles
The steel is cooled with water, straightened and cut to length. It’s now ready for hot rolling or forging.
5
Primary forging
With the cast steel now solid, it's sent to be hot rolled or forged into shape. This phase is known as primary forging.
Here, the steel gets:
- Rolled into beams, tubes, channels and profiles
- Defects smoothed out
- Final dimensions set
6
Secondary forming and finishing
Final stage. This is where the steel becomes exactly what the customer ordered.
Secondary forming processes include:
- Galvanising for corrosion resistance
- Annealing or heat treating to adjust hardness
- Cutting, welding and machining to meet exact specs
By now, the steel is ready for builders, engineers and fabricators. The raw materials are long gone – and the result is a strong, dependable material fit for almost any job.
7
So, steel – how is it made?
From raw ore to rolled profiles, the answer involves heat, chemistry and control at every stage.
- It starts with raw ingredients
- Undergoes extreme heat and high-pressure oxygen treatment
- Gets refined, alloyed, cast and rolled
- And finally shaped into the sheet, bar, beam or tube you need
No part of the process is accidental. Every step is there to make sure the finished product meets exact standards – because when it comes to steel, strength is in the details.
Need steel? We’ve got it made
At The Metal Store, we supply steel that’s already gone through all of this – and comes out the other side cut to size, delivered fast and ready to work.
Our full range includes: Mild steel, Stainless steel, Galvanised steel, Bright mild steel.
We’ll cut it. Pack it. And deliver it when you need it. You’ll even get free delivery on orders over £150 (ex VAT) to most of the UK, and £250 (ex VAT) to the Scottish Highlands.
No faff. Just steel made easy.
