4140 heat treating. Temper or not
4140 heat treating. Temper or not
(OP)
I recently found some documentation regarding brittleness concerns with 4140 if you do not pull back the hardness enough and indication was that if you are desiring a hardness of roughly HRC50 or above, to not introduce any temper because it would actually increase the brittleness of the part. I am curious if anyone has heard of this? I remember seeing a graph and indicated the concerns relative to hardness and the toughness and hardness were not linear, there was a dip in the graph.
We have been doing some small parts without temper for a while now but interested to put this to bed. We flame heat and oil quench and achieving about an HRC50. We really only need a hard case layer but due to the material and cross section, through hardening is almost unavoidable. We have not had any failures yet but would like to avoid that if at all possible.
We have been doing some small parts without temper for a while now but interested to put this to bed. We flame heat and oil quench and achieving about an HRC50. We really only need a hard case layer but due to the material and cross section, through hardening is almost unavoidable. We have not had any failures yet but would like to avoid that if at all possible.





RE: 4140 heat treating. Temper or not
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RE: 4140 heat treating. Temper or not
RE: 4140 heat treating. Temper or not
rp
RE: 4140 heat treating. Temper or not
At the lower temps you will at least get a little stress relief, which will help toughness.
With 4140 your as quenched hardness should be RC 58-60.
You shold be able to temper at 400F-500F and still be above RC 50 and have a lot better toughness.
This is what they do to springs after winding them.
You need to cool gently in still air, rapid coolign will re-introduce stresses.
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Plymouth Tube
RE: 4140 heat treating. Temper or not
Question, why does the notch toughness graph indicate clearly that there is a zone in which we are reducing toughness though? It looks like anything over 100*F for a temper and you are actually reducing toughness??? I guess I am confused to not looking at this graph correctly
RE: 4140 heat treating. Temper or not