How to Harden Steel
Hardening steel can be somewhat of an art form, as it takes practice in seeing the colors of the heated steel and knowing how to plunge the hot steel into a liquid. It will take practice. You should know that if at first you do not succeed, you can always reheat the steel and try again.
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Things You'll Need
- Safety glasses
- Oxygen acetylene torch set
- Pliers
- Metal container of oil
- Metal container of water
Instructions
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Place the safety glasses on your head and over your eyes. Heat the steel to be hardened using the oxygen acetylene torch set with the rosebud attachment. The rosebud attachment gives the most surface area for heat transfer. Only heat the area you want to heat treat.
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Watch the steel in a dimly lit area as this will help you in seeing the colors grow in the steel. The steel will go through a series of colors in the heating of the metal. The deeper the color of orange to red signifies the temperature of the steel. The deeper the color orange to red the higher the temperature. This is very important and it takes practice to observe the colors.
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Grab the cool end of the steel with the pliers and gradually plunge the metal’s hot colored end into the oil container. The metal will snap and crackle in the cooler oil. Completely immerse the metal into the oil and withdraw. Observe the color of the metal; it should be a blue to purple hue to the steel. Re-immerse the steel again and hold it there for a few seconds more.
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Withdraw the steel from the oil and plunge the steel into the water. This will hard-set the steel. This method will take the steel and make it very hard. Never plunge the hot steel into the water first, as this method will crack and damage the steel, causing the steel to be permanently damaged.
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Tips & Warnings
Hardening steel can be extremely dangerous as you are plunging red-hot steel into oil. This should only be done in areas with plenty of fresh air.
Comments
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you can use left over motor oil.
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Thanks for knowledgeable information.
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livens
Jun 17, 2009
More importantly you need to know what type of steel you are using. That will tell you how hot you need to get the steel before quenching it, and whether it gets quenched in oil or water, and some steels get air hardened. O-1 is a common oil hardening steel, and is the easiest to harden for DIYers. Also low carbon steel, like you find at home centers, will not harden. You can use almost any oil, I use mineral oil. But peanut or motor oil works fine too. I do not see the reason for dipping in water after the oil. Also, you MUST temper the steel after quenching it. After the quench the steel will be very hard and very brittle. If you drop in on a hard surface it will probably shatter. O-1 gets tempered immediatly in a 400-450°F oven for an hour or 2, depending on the thickness of the peice. There are charts for the exact temp to temper at, depending on how hard you want the final pro... -
timothyhthoma
Apr 02, 2009
WHAT TYPE OF OIL IS USED IN THE HARDENING OF STEEL?
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timothyhthoma
Apr 02, 2009
WHAT TYPE OF OIL DO I USE?
