[b]Component Over Size Before Heat Treating & Hardening[/b]

[TorsionalStress]

I need to have parts heat-treated, case hardened and then ground.

Is there a rule of thumb that can be used to determine what the over size of parts should be left at prior to having them heat-treated & case hardened & then ground?

Any response will be greatly appreciated!

 

[metengr]

The answer to your question depends on the base material and surface hardening method, for example nitriding versus carburizing. Case hardening using carburizing will definitely affect component dimensions. Can you come back with more information?

 

[dbooker630]

You also need to consider the quenching method, is it a free quench or is it held in dies under quench pressure.

Quench temperature can also be a factor if distortion is a concern, thus causing a straightening operation.

I agree with metengr, please tell us what is the configuration of your part among the additional information.

 

[limct]

0.5mm is a common oversize allowance.
There's no rule of thumb, all of the following have to be seriously considered.

concerning effective case depth.
1) case hardening method
2) workpiece material

concerning possible dimensional change after heat treatment.
1) geometry of part
2) arrange of part in heat treatment furnace



Best regards,
ct

 

[TorsionalStress]

I thought somewhere between 0.020 – 0.030” oversize. The parts are manufactured from 4140 STEEL, Heat-Treated to RC 50 -60, 0.030” deep.

The Heat-Treating & Hardening process will be done outside our facility. The company has asked for drawings to get a better idea since as you all mentioned, the process can differ from part to part.

 

[dbooker630]

Are these parts going to be induction surface hardened or furnace carburized?

4140 is typically surface hardened by induction . Sometimes it also has to be initially furnace pretreated to get the chromium carbides in solution but with only a .030" case requirement you may not have to do that.

 

[TorsionalStress]

I think, the company who will take care of the process can tell me what procedure will be taken, since that’s what they do everyday!

 

[IRstuff]

Your supplier should be the one to tell you what oversize will be needed, based on your requirements.

TTFN

 

[TorsionalStress]

This is why drawings were sent to them! A rule of thumb would be handy though, waiting for suppliers to provide the information can take a very long time and add precious time to the project.