Babbitt Bonding to Bronze
Babbitt Bonding to Bronze
(OP)
We are having bonding problems when spin casting. The casting of bearing shells by the spin cast process has worked well for us for years,we have not changed our methods or products. We recently undertook s job where the split shells are made from SAE 660 bearing bronze. The casting looks great and passes all bond tests, after stress relieving. We are using ASTM #2 babbitt and Flux and Solder 99.9% tin from Johnson Mfg. Problem, we accidently dropped a couple of bearings on the floor and the cast babbitt and bronze fell apart. Any suggestions where the problem is ? Shell temp 425F, babbitt temp 675F spin speed 630 rpm, water mist cooled during spin.





RE: Babbitt Bonding to Bronze
RE: Babbitt Bonding to Bronze
Yes we are with an Tin bath immersion process, cool, clean and re-immerse holding at around 400F till ready to cast
RE: Babbitt Bonding to Bronze
RE: Babbitt Bonding to Bronze
Bronze faiure - Supposedly the lead is insoluble in the alloy, and exists mostly along grain boundaries, tending to make it weak and susceptible to shock.
Tin or bond failure - If the tin/bronze joint was weak due to inadequate or inappropriate prep I'd expect trouble. Is the pre-tin mechanical prep sanding or buffing, which might tend to smear the lead? Would processes like grit blasting or vapor honing be able to clean without smearing? Maybe a chemical etch after mechanical cleaning would be required.
I'm wondering about the reasons to select a bearing bronze to serve as a housing. The ~7% lead in 660 helps it survive when lubrication is marginal. Are the bearing shells "full floating", that is, spinning in a housing while a shaft is spinning inside the babbit ID, making the bronze's bearing qualities important?
These guys say 660 is solderable, but not weldable, and barely brazeable, due to hot shortness.
http://www.anchorbronze.com/c93200.htm
It would seem your temperatures would probably not be up in the hot short range, but .............
RE: Babbitt Bonding to Bronze
RE: Babbitt Bonding to Bronze
If it was epoxy I'd machine the housing ID with rough threads and grit blast or abrade using clean fine grit abrasives (180 grit or a little finer).