Buzz
Steel is a widely used and durable alloy. While steel in many tools has already been hardened, you can further increase its toughness to reduce wear. Hardened steel ensures that blades remain sharp and tools don't bend or break. By simply heating and cooling it, you can significantly improve the strength of the steel!
Steps
Heat the Steel
Use a propane torch to apply heat. Open the gas valve near the end of the burner. Hold a lighter close to the burner’s tip and ignite it. The burner will catch fire once lit. Adjust the flame by turning the gas valve to create a small conical flame.
- A larger flame produces a lower temperature than a smaller one.
- The torch can only heat a small area. For larger objects, you will need a forge head to heat the entire item.
Safety Measures
Always wear gloves and safety goggles when using a propane torch.
Before using the torch, make sure to read the instructions carefully to ensure safe operation.
Hold the steel directly in the flame. Use metal tongs to grip the item with your non-dominant hand so that the flame is away from you. If you cannot hold the item with tongs, place it on a fireproof surface. Use your dominant hand to operate the torch and heat the entire object before focusing the flame on the specific area you want to temper, such as the screwdriver tip or chisel.
- Wear thick gloves to avoid burns.
- Work on a metal or steel surface, such as an anvil, to minimize fire hazards.
Wait until the steel turns red. The steel will turn red as it heats up. When the steel reaches a bright red color, around 760°C, it has reached the proper temperature for the hardening process.
- The actual temperature of the steel depends on its carbon content. The higher the carbon content, the longer it will take to heat.
- Another way to check if the steel is hot enough is by testing if a magnet will stick to it. If the magnet doesn't stick, the steel is ready to be removed from the heat.
Cool the Metal
Pour water or oil into a heat-resistant container, enough to submerge the steel item completely in it.
Transfer the heated steel into the cooling medium. Use tongs to submerge the hot steel into a container of water or oil. Step back once the entire steel object is submerged, as water or oil may splash. Keep holding the object to avoid losing track of it.
- The rapid cooling process will cause the alloy to bond tightly together.
- Wear thick gloves and a face mask before tempering the steel to prevent water or oil from splashing onto your hands.
- Have a Class B fire extinguisher nearby to prevent fires.
Remove the steel from the cooling medium once no more bubbles are formed. Water or oil will continue to boil as it absorbs heat from the steel. Keep the object submerged until no more steam or bubbles appear, which usually takes a few minutes. Place the steel back on the work surface once it’s done tempering.
Tempered steel will be harder, but more brittle. Don’t throw or try to bend the steel once it’s tempered.
Remove any remaining water or oil on the steel. Residual water on the steel can lead to corrosion. Be sure to wear gloves while using a cloth to thoroughly dry the steel.
Tempering Steel in an Oven
Preheat the oven to 190°C. Make sure the oven is fully heated before placing the steel inside. If you're unable to place the steel directly in the oven, a torch will be necessary for tempering.
- Use a mini oven if the steel item fits inside. This allows you to use the oven for other purposes later the same day.
Place the steel in the oven for 3 hours. Position the steel directly on the oven rack or baking tray. Start the oven to begin heating the steel. As it heats, the internal alloy of the steel will soften, reducing its brittleness.
If using a torch, concentrate the flame on the area you wish to temper. Continue applying heat to the steel until a blue color appears on the metal. This indicates that the steel has been properly tempered.
Turn off the oven and let the steel cool overnight. After the steel has been heated for 3 hours, allow it to cool gradually. This period allows the steel to return to its normal state while maintaining the tempered structure. Remove the steel from the oven the following morning.
- If you are tempering steel with a torch, place the steel on an anvil or another steel surface to conduct the heat.
Warning
- Do not touch the metal with bare hands as you may suffer severe burns.
- Keep a fire extinguisher nearby to prevent any fire hazards.
- Wear safety goggles and gloves while working with hot metal.
Things You Will Need
- Blowtorch
- Lighter
- Steel object
- Metal tongs
- Safety goggles
- Gloves
- Heat-resistant container
- Vegetable oil or water
- Cloth
- Oven
