Aluminum bronze flux?

- Should any flux be used with aluminum bronze? Borax or other glassy slags as usually used with copper alloys, or none (the aluminum oxide layer, if
any, protecting it)? I presume degassing doesn't apply, as aluminum reacts? Or is hydrogen still at work here? Hmm, I suppose it would be...
Actually asking this for someone else, although I think I'll try C630 Ni-Al bronze some day.
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @ http://webpages.charter.net/dawill/tmoranwms
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Aluminum bronzes can dissolve gasses as easily as certain other bronzes or aluminum. The gasses that will dissolve depends on the specific aluminum bronze. I used to pour a 7 % Aluminum, 2% Silicon, balance copper Aluminum bronze (like CA 956) that would gas up readily and also was prone to dross and shrink defects.
You should do a google search and look for a flux, like this URL:
http://budgetcastingsupply.com/Price_Sheet.html
I can't endorse this because I never bought anything from them. Most all the fluxes for copper base or aluminum base I have bought from Foseco but they usually sell to medium to larger commercial accounts (foundries). They may sell to small foundries or home foundries.
Aluminum Bronze fluxes are potassium fluorides and other chemicals. Borax is Sodium Borate and the thermodynamics of the fluxing action is different. I.e. Borax wouldn't be the ideal flux for aluminum bronze to the chemistry and temperatures involved. Potassium fluorides do work well with these bronze chemistries and temperatures.
I'm not clear on how you would degas? If you intend to bubble dry Argon or Nitrogen in a graphite lance you can do this to also get the oxides to come up for skimming off, besides for partial degassing also. A lot depends on the melting conditions, such as gas-fired, etc. and if you are keeping your tools clean and dry and handling the molten metal well.
As for the oxide layer, the problem is the skin does tend to protect but while pouring you may notice it constantly breaks. When the stream comes from the ladle into the downsprue it's like pouring through a thin tube. But, you will notice the "tube" or skin of oxidized metal breaks and is swept into the flowing metal stream, only to be replaced by a new skin immediately while the pour is in process. These broken pieces of "skin" are the dross defects in the casting. If you need an exceptionally clean, dross-free casting you might try placing a ceramic filter in the gating system (these can cost $2 to $9 depending on quantity purchased, and filter size) into the gating system so the metal in the casting will look great.
Mark

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Aluminum
dross
Ok. I understand they are all prone to shrinkage, due to the almost eutectic nature of the melting points.

Expensive anyway...

They
On a visit to a local foundry a few weeks ago, I got some silvery drops the guy says degas it, I'd be more inclined to guess fluidizing since these are solid (very brittle) and look like lead.

- Would calcium fluoride or sodium/potassium chloride suffice?

different.
Figured as much... noticed that borax sucks a brass monkey on aluminum... :-o
AFAIK, borax works fine on general bronzes. Has worked fine so far. ;)

Is KF typical for bronze, or just the aluminum variety?

or
come
your
I'll melt it with a propane crucible furnace, when I do. Any difference between SiC and clay-graphite for this?

are
Okay, figured as much. (On a brass pour which I overfluxed and got unexpectedly soupy slag, I got crunchies along the gating for a number of inches... Likewise, I usually get a darker skin around the sprue and gates for a few inches in aluminum castings.)

filter
Yep. Guy I visited uses them in clean bronze castings.
Wonder if you can reuse them after fishing out of the melt........
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @ http://webpages.charter.net/dawill/tmoranwms
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replying to Mark, TDN wrote: lakeside supplies a solid alloy that eliminates hydrogen gas and also deoxidizes aluminum and manganese bronze.
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On Thursday, September 30, 2004 at 12:38:21 AM UTC-4, Tim Williams wrote:

I think you are talking about casting. The aluminum bronze electrodes I have are flux covered.
Dan
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On Tue, 30 May 2017 16:34:36 -0700 (PDT), " snipped-for-privacy@krl.org"

I have a feeling Tim doesn't care anymore since his post is 13 years old. Eric
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On Tuesday, May 30, 2017 at 8:01:15 PM UTC-4, snipped-for-privacy@whidbey.com wrote:

Damn. Forgot to look at the date.
Dan
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