Practical Guide to Steel Manufacturing

1. Understanding Steel

Steel is fundamentally an alloy of iron and carbon, with the carbon content determining its properties:

• Low-carbon steel (0.05-0.3% carbon): Relatively soft and malleable, good for nails, wire, and chains
• Medium-carbon steel (0.3-0.6% carbon): Stronger, used for axes, swords, and agricultural tools
• High-carbon steel (0.6-1.7% carbon): Very hard but brittle, ideal for cutting tools and knife edges

2. Methods of Steel Production

Direct Bloomery Method

Steel can be produced directly in a bloomery furnace by carefully controlling conditions:

1. Build a bloomery furnace as described in the Iron Smelting guide
2. Use a higher ratio of charcoal to ore than for regular iron smelting
3. Maintain a moderate temperature (around 1100-1200°C) rather than maximum heat
4. Ensure consistent but not excessive airflow
5. The resulting bloom will contain areas with higher carbon content (steel)

Carburization Method

This method involves adding carbon to already smelted iron:

1. Create thin bars or sheets of bloomery iron
2. Place the iron in a sealed clay container with charcoal powder, crushed bone, or other carbon-rich materials
3. Heat the container to 900-1000°C for several hours
4. Carbon from the surrounding materials will diffuse into the iron
5. The longer the heating process, the deeper the carbon penetration

Decarburization Method

If you have high-carbon cast iron from a blast furnace, you can reduce its carbon content:

1. Break cast iron into small pieces
2. Heat the pieces in an oxidizing environment (with good air flow)
3. Repeatedly heat and hammer the iron to work out carbon
4. Continue until the desired hardness is achieved

3. Pattern Welding

Pattern welding combines different types of iron and steel to create superior tools and weapons:

1. Forge several thin bars of varying carbon content
2. Stack these bars alternately
3. Heat the stack to welding temperature (bright yellow-white)
4. Hammer the layers together to forge-weld them
5. Fold the resulting bar and repeat the process several times
6. The final product combines the hardness of high-carbon steel with the flexibility of low-carbon iron

4. Heat Treatment

Heat treatment is crucial for optimizing steel properties:

Annealing

1. Heat steel to cherry-red (700-800°C)
2. Allow it to cool very slowly (bury in sand, ash, or lime)
3. This softens the steel, making it easier to work

Hardening

1. Heat steel to bright cherry-red (800-900°C)
2. Quench rapidly in water, brine, or oil
3. This creates very hard but brittle steel

Tempering

1. After hardening, reheat steel to a lower temperature (200-650°C)
2. The temperature determines the final hardness (lower temperatures yield harder steel)
3. Allow to cool naturally
4. This reduces brittleness while maintaining hardness