440C distortion
440C distortion
(OP)
I am designing a tubular shape detail out of 440c stainless that will be vacuum furnace heat treated to AMS 2759/5 spec's using gas quench (Rock "C" 59-61). I am trying to determine an approximate value the O.D. and I.D. may distort and grow so I can determine which diameters will require a secondary grind operation and how much grind stock should be allowed. The research I have found shows .0001-.0002 in / in. This is very vague and I am not sure how it would apply in my case. Is the distortion on the O.D and does the /in relate to O.D. and what affect does the I.D. have?
One section of the detail has a 1.178 O.D. and 1.022 I.D.
Another section of the detail has a 1.415 O.D. and 1.022 I.D.
I asked the source that will be performing the heat treat today but was not able to get an approx value.
Any help would be greatly appreciated.
Thanks,
Nickjk
One section of the detail has a 1.178 O.D. and 1.022 I.D.
Another section of the detail has a 1.415 O.D. and 1.022 I.D.
I asked the source that will be performing the heat treat today but was not able to get an approx value.
Any help would be greatly appreciated.
Thanks,
Nickjk





RE: 440C distortion
Aaron Tanzer
www.lehightesting.com
RE: 440C distortion
This is an instance where experience is your best resource. If you have no access to anyone with the needed experience, I think I'd add 0.020" to the OD and ID for grind allowance and then check to see how much distoriton you get. If you can afford to scrap the start-up parts, you may consider only 0.010", but if that isn't enough, there isn't much to do except to scrap them (there isn't going to be a good way of salvaging the distorted parts).
rp
RE: 440C distortion
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Distortion of the component during heat treatment is a separate issue, and usually occurs in the quenching operation. If the part is long and slender, or has varing thickness (especially where thin sections are directly adjacent to relatively thick sections), then heat will not be drawn out of the part in a completely uniform manner during the quench. The thinner sections will transform more quickly, resulting in transformation related stresses. This can lead to material movement, and may result in distortion or even cracking if the quench is severe enough. Parts that are gas quenched in a vacuum furnace rarely crack, but they certainly can distort for the reasons mentioned. In most cases an additional 0.010" - 0.020" grind stock allowance is usually sufficient. When more grind stock is included, the grinders usually complain rather vehemently. Best not to upset them unless it is deemed necessary.
Maui
www.EngineeringMetallurgy.com