How does stainless steel ball burnishing of stainless steel parts work?
I'm looking for introductory information about the chemistry and
physics of the process (aimed at a professional engineer, at least
1000 words), and some detail about the chemicals involved (preferably
both what the chemicals actually are and commercial products (part
codes and supplier contact details for the chemicals) available in
Australia), and the processing parameters I should expect (eg. How
long should a batch take to burnish? How do the positions of the two
weights in the machine influence the finish achieved? What is the
effect of the machine's speed?).
Background and research already completed:
I have recently purchased an industrial burnishing machine (not this
one [http://bvproducts.com.au/Products/bowls.htm], but a machine a bit
like it). The supplier and I are trying to make it work... and having
trouble.
I'm using 5mm stainless steel balls for media and either a tallow soap
based brightening compound or a citric acid based compound. My parts
are pressed stainless steel (304) housings (2.5mm thick, geometrically
similar to a large coffee mug).
My parts are drawn, which leaves them with two distinct surface finish
regions: part the original grey of the steel, part already pressure
polished to a high brightness. My current process makes the regions
that are already bright very bright, and doesn't do much to the grey
regions, so the parts look silly. I'm sure the process is able to
bring the rougher regions to a high brightness (examples I've found so
far here [http://www.pfonline.com/articles/web100201.html] and here
[http://dougcometalfinishing.com/burnishing.html], various others
mentioning mirror pright finishes and process times between 5 and 40
minutes), but I'm not sure how. My supplier also provided me with one
sample (a year ago) with a mirror bright finish, which he said at the
time he did in 30 minutes, but we can't work out how he did it and he
can't reproduce it. My current process is taking about two hours to
produce a very inferior finish.
I've done some experimenting on my own, including peening the parts
with steel ball and hammer, and the impression of the ball alone does
not produce a bright finish - the chemical must be a part of the
process.
My current working hypothesis is that we're using the wrong
chemicals... that our sample part of a year ago was done with a
different chemical blend, which my supplier is unable to reproduce.
Other things:
* Don't bother rewording material you find on the web (links are good,
and I read fast).
* Don't talk to these guys - http://bvproducts.com.au/. |
