Originally Posted by Mcgyver Take this as half statement, half question, cuz you guys are pro’s and I’m not. |
Pro is a relative term for metaligists. I'm more of a hacker that has had some exposure to the different processes I have needed to do over the last 30 years. My limited experiences do not qualify me as a pro. I am still learning as I go.
Originally Posted by Mcgyver With heat treating tool steels, a good part of not cracking has to do with design, not whether the heat treat is done properly. I thought a case process had a lot more design latitude, ie sharp corners, thin sections than tool steel would allow |
There is a hand in hand relationship here and either portion of the project can screw up the end result. The unexpected still happens for no obvious reason.
Originally Posted by Mcgyver why on this application would you care how tough the core was if case hardening gives you 60 Rockwell to 50 thou – what physical property of a hardened steel core matters here? |
I look at this as part of spring with a wider capability to handle cycled stresses. This application could make the difference in returning to its original shape as the material yield strength goes up, but won't snap like glass below the surface.
Originally Posted by Mcgyver One Of what do mean by being suspicious of grinding a case hardened piece – what is the concern? I would have thought that if the core is ductile it would mean less stress - I mean the quench produces stress risers right whether its case or tool steel right? |
My suspicions are based on the case no longer being equally supportive of the internal and/or applied stresses if an excessive amount is removed from one side verses another. That does not make it fact, just suspicion?
Originally Posted by Mcgyver I was under the impression that any steel after quenching could move around without seasoning, that there was no silver bullet because the act of quenching locks into the crystalline structure stresses, are you saying there steels that you are stable after hardening? I know my tool and die maker friends season their best tooling before finish grinding to try to work out these stresses. |
There are far to many variables to have a silver bullet. Reducing the chances is about as good of odds one can expect.
Martensite is transformed from austentite and is more stable for precision tooling. The seasoning process can be induced with large temperature swings over time. The best time to do this transformation is immediately after HT to the critical temp. I can see this as an option for inspection and parts expected to be stable for tight running members.
A grinding vice used on most shop mills that have trouble holding anything better than a half thou may be a bit overkill, but to each his own as the need applies and makes them sleep better at night.
DC