Quench & Tempering Steel Bar
Quenching and tempering are processes that strengthen materials like steel and other iron-based alloys . These processes strengthen the alloys through heating the material while simultaneously cooling in water, oil, forced air, or gases such as nitrogen.
Why is steel tempered after being hardened?
Why Is Steel Tempered? Tempering steel after a hardening process allows for a middle ground of hardness and strength . This is achieved by allowing the carbon diffusion to occur within a steel microstructure. When steel is hardened, it can become excessively brittle and hard.
Why are steel tempered after quenching?
After being quenched, the metal is in a very hard state, but it’s brittle. The steel is tempered to reduce some of the hardness and increase ductility . It’s heated for a set period of time at a temperature that falls between 400° F and 1,105° F. ... Finally, the steel cools in still air rather than being quenched again.
What happens to steel after quenching?
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.
Do you need to temper a blade after quenching?
After the blade has been quenched, its hardness is still not suitable for usage. In its hard and brittle state, the quenched blade will shatter like glass if dropped, it must be tempered before it is put to use. ... A tempered blade will hold a sharp edge and still retain strength and flexibility.
Why do we prefer tempering 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 steel has the appropriate amount carbon present that will go into solution and transform to martensite. Process (austenitizing) temperature has been achieved.
What is the purpose of tempering steel?
The maximum hardness of a steel grade, which is obtained by hardening, gives the material a low toughness. Tempering reduces the hardness in the material and increases the toughness . Through tempering you can adapt materials properties (hardness/toughness ratio) to a specified application.
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 over temper steel?
If you quench a carbon steel from its austenite regime, you will have phase transformation and at high cooling rates to room temperature you will have martensite and possibly retained austenite, if the carbon content is high. If the cooling is stopped at a higher temperature, retained austenite fraction is higher.
What is the difference between hardening and tempering steel?
As the names imply, hardening makes the metal more rigid but more brittle , and tempering (from “temperate”, moderate), forgoes some hardness for increased toughness.
Can you temper steel twice?
Tempering is generally carried out in a single cycle temperature-time. However, the procedure may be conducted in two cycles with cooling to room temperature between the cycles . This process is known as double tempering.
Can you temper steel too much?
At 600 °C (1,112 °F) , the steel may experience another stage of embrittlement, called “temper embrittlement” (TE), which occurs if the steel is held within the temperature range of temper embrittlement for too long.
Can you over quench steel?
In order to control the finish product’s brittleness, ability to withstand tensile stress and overall strength, the metalworker must carefully control which states the metal reaches and how quickly. A misstep in any part of the process could lead to unsuitable steel.
How long should I temper my blade?
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.
Does quenching increase hardness?
Quenching improves a metal’s performance by rapidly cooling the heated metal, thereby altering its molecular structure and increasing its hardness . The rate of quenching may be adjusted to achieve the desired properties.
Can you temper a knife with a torch?
A propane (or MAPP gas) torch played evenly along the blade will get the job done. Try to get the heat color evenly across the blade. You don’t need to harden the entire knife blank. Just the blade is good enough .
