What is the process of hardening and tempering?

Steels are heated to their appropriate hardening temperature {usually between 800-900°C), held at temperature, then “quenched” (rapidly cooled), often in oil or water. This is followed by tempering (a soak at a lower temperature) which develops the final mechanical properties and relieves stresses.

Do you need to temper after hardening?

It is mandatory to temper the steel after it has been hardened. This is simply because a new phase has been created, which is martensite. The appropriate cooling rate has been applied to transform the austenite into a complete martensite phase. The steel is now in its most brittle condition.

What temperature do you temper a knife at?

To reduce the brittleness, the material is tempered, usually by heating it to 175–350°C (347–662°F) for 2 hours, which results in a hardness of 53–63 HRC and a good balance between sharpness retention, grindability and toughness.

How many times can you quench a blade?

This doesn’t have to be as severe as one grind pass on each side in an alternating sequence, alternating sides 3 or 4 times during the process should be reasonable for a typical knife.

How is tempering done?

Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.

Is quenching the same as tempering?

The process of quenching or quench hardening involves heating the material and then rapidly cooling it to set the components into place as quickly as possible. Tempering is achieved by heating the quenched material to below the critical point for a set period of time, then allowing it to cool in still air.

What happens if you quench too much?

Often, after quenching, an iron or steel alloy will be excessively hard and brittle due to an overabundance of martensite. In these cases, another heat treatment technique known as tempering is performed on the quenched material in order to increase the toughness of iron-based alloys.

How do you harden and temper a knife?

You harden a knife by heating it to between 1800 and 2000°F and then quickly quenching it in oil or water. The good news is that your blade is very hard after the quenching. The bad news is that is also very brittle. That is where the tempering process comes in to solve the problem of brittleness.

What does it mean to temper a knife blade?

This is what hardens the blade. After the blade has cooled sufficiently, then you must “temper” the blade to slightly lower the hardness so that the steel is not too brittle and prone to chipping, cracking or breaking. Tempering is accomplished basically baking them in an oven at a much lower temperature then the heat treat temperature.

How do you heat treat a knife blade?

Process of heat treating a knife blade. After the blade has cooled sufficiently, then you must “temper” the blade to slightly lower the hardness so that the steel is not too brittle and prone to chipping, cracking or breaking. Tempering is accomplished basically baking them in an oven at a much lower temperature then the heat treat temperature.

What hardens the steel of a knife blade?

The steel actually changes crystal structure at this point. This is all part of the hardening process of the blade. Once the blade is heated to austenite temperatures, it’s important to quench the blade so that the steel cools rapidly. This is what hardens the blade.