Heat Treating 4130 1

[mycuriousmind]

Can you wait to temper the metal after you normalize it? The specification that we use calls out the the tempering has to happen within two hours of quenching. What will happen to the metal if we wait longer?

 

[redpicker]

If you have liquid quenched the material, you run the risk of cracking is the delay in tempering is too long.

With an air cool on 4130, the risk of cracking is much reduced.

rp

 

[swall]

If you are doing a normalize and temper, the temper can be delayed until convenient. If you are doing a quench and temper, temper should follow quench as soon as possible.

 

[arunmrao]

What is the alloy,that you are liquid quenching ( I assume). It is important to at least provide a low temperature flash temper to avoid cracking due to thermal stresses.

 

[mycuriousmind]

It is 4130.

 

[tbuelna]

Excuse me for pointing out the obvious, but if your process spec requires tempering to be performed within two hours of quenching, and you fail to do so, you run the risk of ending up with non-conforming hardware.

 

[kumkumvijay]

you need to do the tempering after quenching with in 1.5hrs ( best) to avoid cracks or distortion of the part due to stress gained in the quenching process.
Also tempering break the martensite needle structure.
Tempering & normalizing both relieve the stress, so there is no need to tempered it after normalizing.

If you do normalizing or annealing before quenching & tempering process, it will help to reduce the stress accumulation, distortion in the quenching process.

 

[tbuelna]

Some critical applications (such as aircraft gears) require normalize and temper prior to any machining operations. I also believe it is helpful to temper after normalize when the part has thick sections.