How to Heat Harden Steel
Hardening steel through the use of heat has been known for centuries. There is more to hardening steel than getting it hot and plunging it into water, however. There is a second step necessary in order to make the hardened steel less brittle.
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Things You'll Need
- Forge, blow torch or other means to heat steel to red-hot temperatures
- Tongs for handling steel
- Drum of water large enough to submerse the heated steel
- Protective clothing
- Eye protection
- Heavy gloves
Instructions
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Place the steel to be hardened into the coals or the flames of a furnace capable of heating the steel until it turns red hot. The color of the steel is the only gauge you need as to its temperature. As the steel heats it will go through several color changes, the final one being red.
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Using tongs, pick up the red-hot steel and immediately dunk it into a tank of water. This is known as quenching the metal. The water does not need to be cooled; room temperature water is all that is necessary. The steel is now extremely hard but brittle. Handle it with care at this point and do not drop it or strike it.
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Reheat the steel. Watch the color changes as the steel reheats and wait until the steel has turned a deep BLUE in color (this is the temperature just before it turns red hot). When the steel is blue pick it up with your tongs and plunge it once again into a tank of room-temperature water.This is the annealing step. Allow the metal to cool under the water.
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Remove the metal from the water and dry it. It is now heat hardened and has been made flexible enough by the annealing process that it will not shatter if struck or dropped. Your steel is now approximately 25 percent harder than it was before you began the heat treating process.
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Tips & Warnings
Use caution and common sense when heat treating metal. The temperatures involved are extreme and proper safety procedures must be observed at all times.
Be prepared in case of fire.
