How to Harden Steel Pins by Fire

Steel can be hardened in the home workshop.

Mild steel can be case-hardened in the home workshop to increase its durability and strength. The hardening requires high temperatures because the surface of the steel object must be hot enough to become liquid. Case-hardening involves the use of a carbon compound to increase the carbon content of the steel molecules. It is effective because it helps the object's surface to resist wear while allowing the core to retain its toughness without becoming brittle.

Things You'll Need

• Heat source strong enough to heat steel to between 1,400 and l,700 degrees Fahrenheit
• Pliers or tongs
• Heat-proof gloves
• Case-hardening compound
• Water
• Container large enough to hold object being hardened
• Wire brush

Instructions

1. Heat the steel object at a high temperature until it turns cherry red -- between 1,400 and l,700 degrees Fahrenheit. Rotate object to ensure even heating. Use pliers or tongs to grip the steel object during the process and wear heat-proof gloves while holding the pliers or tongs. This will protect your hands from the heated metal.

2. Dip the steel object into a high-carbon, instant hardening compound. Stir to coat its entire surface. This step may take an hour or more.

3. Reheat the object to a cherry-red color.

4. Dip into clean, cold water.

5. Clean any scale from steel with the wire brush.

6. Repeat if necessary.

References

• Country Plans: Hardening Steel in the Home Workshop
• International Molybdenum Association: Case Hardening Steel
• Hemmings: Case Hardening in a Home Garage