How to Harden Steel With Water

Heat treating steel can fundamentally change its properties. The process can transform steel from something that is soft and malleable to a material that is hard and brittle. Using liquids to harden steel is a process known as quench-hardening. The standard method for quench-hardening with water and then tempering is taught in metal shop classes everywhere. It can be tricky, but with the right steel and the proper technique, you can quench harden steel.

Instructions

Hardening

1

Put on protective clothing. Bring the forge or furnace up to temperature. If not utilizing a forge or furnace, light your torch.

2

Use tongs to place the steel in the furnace or forge. Place the steel on a prepared firebrick hearth if using a torch. Heat the steel to between 1450 and 1500 degrees Fahrenheit. Use a pyrometer to measure the steel's surface temperature. If you don't have a pyrometer, watch for the steel to glow cherry red.

3

Grasp the steel firmly with tongs and plunge it into a container of water. Agitate the steel vigorously to ensure a thorough quench. Test the hardness of the steel by attempting to file it. The filing process should be very difficult.

Tempering

4

Clean the steel with emery cloth until you can see bright metal. Place the steel back in the forge or furnace. If you don't have a forge or furnace, begin reheating the steel with the torch.

5

Watch the steel carefully in order to track color changes. A progression of colors will take place, starting with yellows to browns and finishing with purples and blues. Stop heating at a pale straw yellow color for good edge holding ability. Continue heating to blue for higher resistance to impact.

6

Stop heating the steel when the desired temper is reached. Place the steel on an anvil or other heavy metal surface. This surface will act as a heat-sink while the steel cools. The implement can be used when it has fully cooled.