Grain Structure of A286

I hope you guys can help; we have a major problem here! We manufacture
aerospace hardware. One job I'm working on now is a special A286
locknut (very expensive!). Before machining we have the bar
age-hardened On the spec it calls for metallurgical testing that
specifies no dual-plex grain structure. After testing it was found the
parts did have grain sizes from 2 to 8 (not good because that's a
dual-plex structure). The material is A286 AMS5731. We've been trying
to contact the metal supplier (Carpenter Technology) but they won't
respond at all. Meanwhile we bought more material and cut a 1-inch
sample piece to age and re-test before attempting to remake the job.
We've tried to re-solution and age but that didn't work, either. I've
been making sinilar parts for over 20 years and never had this trouble
before. What's going on?!?! I hope you can help before I tear the
rest of my hair off.
Dave
Reply to
Monterey Machine
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================ Dave:
One quick question -- where did you buy the second batch of material and are the heat/cert numbers the same as the first batch?
I am taking the liberty of reposting your question to another newsgroup I subscribe to -- sci.engr.metallurgy. The very knowledgable people there should be able to give you a definitive answer and possibly suggest suppliers, heat treaters, etc.
==> Note to sci.engr.metallurgy -- please [cross] post responses to alt.machines.cnc
Thanks
Unka George (George McDuffee)
There is something to be said for government by a great aristocracy which has furnished leaders to the nation in peace and war for generations; even a democrat like myself must admit this. But there is absolutely nothing to be said for government by a plutocracy, for government by men very powerful in certain lines and gifted with the "money touch," but with ideals which in their essence are merely those of so many glorified pawnbrokers.
Theodore Roosevelt (1858-1919), U.S. Republican (later Progressive) politician, president. Letter, 15 Nov. 1913.
Reply to
F. George McDuffee
material and are the heat/cert numbers the same as the first batch?<
Thanks for responding. The new batch of material from Carpenter is a different heat lot and a larger diameter (it was all they had in stock). You were saying if small contaminants were in the material it could cause the dual-plex grain structure; on the drawing specs it requires the finished parts to be sampled for hardness, micro-structure and chemical analysis. We will compare the chemical analyses of the original material cert to the analysis done by MMA Laboratories in Huntington Beach, CA (the original certs indicate the material was made in the USA by Carpenter). Do you have any other theory on what can cause dual-plex grain structures? Also, can you recommend a good metallurgist? Thanks again, Dave
Reply to
Monterey Machine
================ I suggest trying the sci.engr.metallurgy newsgroup -- very knowledgable people there.
I am out of my depth beyond knowing that contaminants can cause grain size/boundry problems. [I can however spin a good story about how "soft" malleable iron can wreck HSS broaches when contaminated with copper although well with in specifications...]
One other item you might want to check is to see exactly what heat treat process was used and how closely it is controlled. There can be a tendency for a heat treater to consolidate lots from different customers to reduce costs. Also see if any of the HT personnel are new and/or if the heat treater has been acquired as some sort of "roll-up" or "stealth chain" move.
Grasping at straws here, but have you had a microstructure done on the material *BEFORE* heat treating? If it is dual-plex before HT this might indicate something.
Let us know the rest of the story.
Unka George (George McDuffee)
There is something to be said for government by a great aristocracy which has furnished leaders to the nation in peace and war for generations; even a democrat like myself must admit this. But there is absolutely nothing to be said for government by a plutocracy, for government by men very powerful in certain lines and gifted with the "money touch," but with ideals which in their essence are merely those of so many glorified pawnbrokers.
Theodore Roosevelt (1858-1919), U.S. Republican (later Progressive) politician, president. Letter, 15 Nov. 1913.
Reply to
F. George McDuffee

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