Heat Treating IN718 Shafts

[jsokal]

Greetings,
I would like to have anyone's opinion regarding the vacuum fce heat treatment (solution treating 1750°F) of 50" long 2-3" thick bored out shafts made of IN718. Here is some background:
We have a new application where they want to minimize any shaft runout during the heat treatment. My opinion is simply to load them up on the large end,vertically and unrestrained. One deep thinker in our organization (PhD type)is all paranoid and wants me to suspend the shafts at the top so that they hang freely, using their weight to "straighten" the shafts. It was even suggested to hang heavy weights of the bottom!(lol this cracks me up!)
Anyway, my question is: Has anyone ever heat treated long thin shafts and done anything other than stand them up vertically.

thanks
John

 

[Maui]

What are the shaft runout tolerances that you are attempting to satisfy by adopting this new method of solution treating?

Maui

 

[TVP]

The following is an excerpt from ASM Handbook Volume 4 Heat Treating, specifically the section on "Defects and Distortion in Heat-Treated Parts":

Fixtures for holding finished parts or assemblies during heat treatment may be either support or restrain type. For alloys that are subjected to very rapid cooling from the solution-treatment temperature, it is common practice to use minimum fixturing during solution treatment and to control dimensional relations by using restraining fixture during aging. Support fixtures are used when restrain type is not needed or when the part itself renders adequate self restraint. Long narrow parts are very easily fixtured by hanging vertically."

I think your egg-head has a good point, although I am not so sure about adding mass to the end. It would be interesting to use one of the simulation programs like DEFORM-HT from SFTC to see the interaction of additional mass on a free-hanging, vertically-oriented hollow shaft during quenching from solution treatment temperature.

 

[arunmrao]

It is ok if you can suspend the parts vertically. This would minimize on your fixturing. Adding weights may not be helpful and is certainly not a common practice.

 

[EdStainless]

We have heat treated tubing of PH stainless grades by hanging them. They do come out straight. And there are no fixture marks.
I wouldn't add weights.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[jsokal]

Thanks for all the good advice,..greatly appreciated!

Maui, they are looking for runouts better than 0.010".
I think that this is a bit much to ask for in a shaft thats 53" long.

thanks again
John