How to Strengthen Metal
Certain types of metal can be strengthened through a specific sequence of heating and cooling. Steel is a prime example of a metal that fits this bill, but it must high in carbon -- like tool steel or silver steel -- for the process to work. The carbon is needed to change the crystalline structure, which is what allows the steel to change from hard to soft during the process. This technique is called hardening and tempering.
Things You'll Need
- Brazing heart
- Brazing torch
- Fire bricks
- Bucket
- Water
- Emery cloth
- Tongs
- Steel surface
Instructions
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1
Place the metal being hardened onto a brazing heart.
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2
Arrange fire bricks in a semi-circle behind the steel. The bricks stop heat from escaping and reflect it to the metal. Basically, they keep the brazing heart as hot as possible.
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3
Heat up the steel with the brazing torch. This should be done slowly at first.
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4
Focus the heat from the torch directly on the steel to intensify the heat on the metal. Stop when the steel is red hot.
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5
Grab the steel from the brazing heart with blacksmith tongs and submerge it in a bucket of water. Make sure the water is both cold and clean.
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6
Remove the steel from the bucket. At this point, the steel will be extremely hard. It is also very brittle, meaning it will easily snap.
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7
Clean the steel with an emery cloth.
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8
Return the steel to the brazing heart. Heat the steel with the brazing torch again. Remember to start slowly and to focus the heat on the metal. A blue line appears around the steel; stop the brazing torch once this line has covered the entire piece of metal. The steel is now ready to be tempered.
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9
Pick up the steel from the blazing heart; use the tongs to do this.
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10
Drop the steel onto a steel surface like an anvil. Using a steel surface will conduct the heat, which means that the hot piece of steel will take longer to cool. That is a good thing when tempering metal.
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Leave the steel to fully cool. It will no longer be brittle, and the metal will be stronger than ever.
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