A286 stake studs problems
A286 stake studs problems
(OP)
I am with a cold heading company, we have been experiancing an issue where our customer cannot stake an M10 stake stud into the their exhaust flange (won't fully seat). We have been providing this stud for a number of years and just since 11/05 have had this issue. We have investigated and cannot find any process that have changed either in our process or the customers. We did have a the steel analized metalurgically and discovered a condition that we were told was called Eta phase. Our knurls are "rubbing" away during the stake operation. We have found the surface hardness to be slightly softer than the core after the studs have been precipitation hardened per ASTM A453M. We have tried different steel suppliers and different heat treat facilities, knurl diameters, but have hit a dead end every time. Any help in pointing me in a direction to finding a root cause to this would be greatly appreciated.





RE: A286 stake studs problems
This sounds like a geometry/force problem, not a materials one. Even if both the stud and flange are harder/stronger, a larger force will seat them (unless debris has become trapped between the flange and stud).
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: A286 stake studs problems
RE: A286 stake studs problems
You should have microhardness values taken at the splines. Also, do some lab installations of the splined studs into the flanges. Look to see if the splines are sheared due to low fracture toughness, or grossly deformed due to low strength.
Eta is Ni3Ti, one of the possible phases in this system. I don't have a lot of experience with that, so I can't comment much.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: A286 stake studs problems
If anyone else has any more info on the Ni3Ti, it would be helpfull i think to better understand this possible phase.
Thanks,
GunnyD