Steel is a very strong alloy, and while most tools made from steel are strong enough, you can make them even stronger. Hardening the steel prevents blunting of blades and bending or breaking of tools. You can make steel last longer by heating and quenching.
Step
Part 1 of 3: Heating Steel
Step 1. Use a propane torch as a heat source
Open the gas valve near the base of the torch. Hold the striker tool near the tip of the torch, and squeeze to create a spark. The torch will light up after a few tries. Turn on the gas valve to adjust the flame so that it forms a small funnel.
- A large fire produces less heat, as opposed to a small fire.
- The firing torch only heats a small and concentrated area. For large steel, you will need to use a forge to heat the entire material.
Precautions
Always wear protective glasses and gloves before using a propane torch, read all instructions so you can handle it safely.
Step 2. Keep the steel in direct contact with the fire
Hold the steel with your dominant hand using tongs so you don't have to be near the fire. If you can't use tongs, work on another, wider fireproof surface. Use the torch with your dominant hand to heat the entire steel before focusing on the area you want to harden, such as the tip of a screwdriver or chisel.
- Wear thick gloves so you don't get burned.
- Work on metal or steel surfaces, such as anvils, to prevent fires.
Step 3. Wait until the color of the steel changes to cherry red
Pay attention to the color of the steel as it gets hotter. When it turns cherry red, it means the steel is at about 760 degrees Celsius, which is hot enough to solidify.
- The actual temperature of steel depends on the carbon content in it. Higher carbon content takes longer to heat.
- Magnets can also be used to test the readiness of steel. If the magnet is not attached to the steel, the steel is ready to be removed from the heat.
Part 2 of 3: Cooling Metal
Step 1. Put water or oil in a container deep enough to submerge the steel
Use a coffee can or other similarly shaped container as a cooling chamber. Pour water or vegetable oil so that it is 5-7.5 cm from the rim of the container. Make sure the oil or water is at room temperature.
- Water is great for quickly cooling hot metal, but it can cause thin steel to distort or crack.
- Vegetable oil has a high boiling point so hot steel takes longer to cool and reduces the chance of cracking. However, oil can spill and cause a fire if the steel is immersed in the oil too quickly.
Step 2. Transfer the heated steel directly to the cooling medium
Use tongs to bring the steel while it's still hot to the container. Back off when you completely immerse the steel in water or oil to avoid getting steam or splashing it. Keep holding the steel so you don't have to pick it up from the water/oil.
- This cooling technique will cool the steel quickly so that the alloys in it harden together.
- Put on thick gloves and a face mask before cooling the steel so that hot water and oil don't get on your hands.
- Have a Class B fire extinguisher nearby.
Step 3. Remove the steel from the cooling medium when the bubbles have stopped
The water or oil will continue to boil due to the heat flowing from the steel. Keep the metal fully submerged until there are no steam or bubbles, which should only take a few minutes. Set the steel back onto the work surface when you are finished.
Cooled steel is harder, but becomes more brittle. Do not drop or bend the steel after removing it.
Step 4. Wipe off the remaining cooling medium from the steel
Water left on the surface of steel can cause corrosion and damage. Wear gloves while drying the steel surface completely with a clean cloth.
Part 3 of 3: Forging Steel in the Oven
Step 1. Preheat the oven to 190 degrees Celsius
Allow the oven to fully heat before putting the steel in it. If the steel won't go into the oven, you'll need to use a torch for the tempering process.
Use a small toaster oven if the steel can still fit inside. That way, you can still use the oven for the whole day
Step 2. Put the steel in the oven and wait for 3 hours
Place the steel directly on the oven rack or parchment paper. Let the oven heat the steel. During the tempering process, the steel is hot enough to soften the alloy in it so that it is less brittle.
If you want to use a firing torch, focus the tip of the flame on the area you want to harden. Keep heating steel until you see the formation of a blue color on the metal.
This indicates that the steel has been processed.
Step 3. Turn off the oven and let the steel in it cool overnight
If the steel has been heated for 3 hours, allow the steel to cool slowly. Thus, the steel can be normalized while keeping the structure hard. Remove the steel from the oven the next morning.
If you are working steel with a torch, place the metal on an anvil or other large metal surface to distribute the heat
Warning
- Wear safety glasses when working on hot metal.
- Do not touch metal with bare hands as this will cause severe burns.
- Always have a fire extinguisher nearby in case of a fire.
