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Chips Ahoy

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This is pic of a zink fire we had a couple days ago while pouring bronze. We should have waited until the crucible was in the pouring shank (out of the furnace) before removing the glass & dross. You can see the ladle of glass & dross in the scoop above and to the right of the furnace, in front of the guy with the proximity suit. The fire lit before he got less than 24" away with the scoop. There was no danger, he has the proper 3M mask on, and you can see he was upwind by the smoke plume. During the melt, we have it lite off frequently when we extract the pyrometer. It burns up until the hole in the glass "heals".
Why did I post this? Be careful guys. This is a fun and rewarding sport, but have the right gear and think it all the way thru before you start.
1603597526102_IMG_0792.jpg
 

MRA

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Is that bronze, or brass?

My mate and I made some brass a while back using scrap copper and a load of wheel-balancing weights, which are no longer lead here in the UK due to enviro regs but rather zinc (or sometimes, steel). We got the copper runny and the first few we threw in, went off like a less-fierce magnesium fire. We were outside, but there was still a fair bit of breath-holding going on. Not having a helmet with an air supply, I might use the furnace blower to create an air current in the right direction, next time.
 

Chips Ahoy

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It is bronze. A couple of ways to reduce or eliminate the fumes/fire are, use an electric furnace hense no open flame or using glass to "seal" the surface of the molten metal.
You are correct in melting the copper first then adding the PREHEATED zinc.
I have about decided to only pour brass or bronze only if I have to. The projects we are working on can use alumi-bronze just fine and we won't have to deal with the fires and fumes from zinc.
 

MRA

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What mix for bronze are you using, with zinc in it? I generally make mystery bronze from a 90-10 copper-tin mix plus various bits of bronze scrap, and this does not create much in the way of fumes - seems to machine ok, though of course every batch is different. I have tried with a glass 'lid' too - it pulls off like sticky toffee, and in my use seems more important when trying to make brass (rough recipe 70-30 copper-zinc). Mine is a waste-oil burner which I blow in with forced air - a fairly messy thing all round but very cheap to run, which is one of my personal objectives, though not of course everybodies.
 

Chips Ahoy

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I dunno the pedigree of the bronze, we don't purchase it for the foundry. It is all donated scraps, for example we have a 5gal bucket of sprinkler heads, a 5gal bucket of identical pump housings, water meter housings and a bucket of who knows what identfied only by color after saw cuts. Our aluminum runs the same kind of gamit of un-identifiable stuff with a few exceptions like just under a hundred pounds of 6061- T6 of course the T6 goes away when melted, and some of the fellows purchase larger branded ingots from a commercial foundry.
What I am lining up to do now is make an AlumaBronze. The goal is 80% copper, using a collection of known copper plumping fittings and pipe, 12% 6061 aluminum and 8% tin... all by weight. The tin has some trace zinc and silver. The aluminum will provide a "sprinkle" of silicon, iron and magnesium. This is a formula we have the resources to repetedly duplicate if it turns out to be redily machinable it will (hopefully) resemble 517 bronze... i think. BTW. I don`t know these things first hand ...yet. I am going on what I've read and thru what some more experienced friends have shared.
 
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MRA

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Sounds like some of your scrap bronze is perhaps brass, given the zinc fumes you're observing. Thanks for the heads up on aluminium bronze - I had not read it up, and now I have it looks very much worth a go. Scrap alloy is much easier to get hold of (for nothing!) than tin. The resulting metal appears to look a good bit more like brass, too, than normal bronzes, which might be useful in some circumstances. If I get anywhere, I'll add a thread here.
cheers
Mark
 

Chips Ahoy

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Actually, the pump housings and meter housings appear to be more reddish and display a series of rings when sawn. That would indicate a silicon bronze, about 20% zinc. For our uses the strength and machinability seem to be more than adequate, we just don't want to work with the mess of zinc. We also find that a drawback to using glass, somehow it seems to condense on the outside of the crucible and plinth in effect gluing them together. This can allow the plinth to drop off at anytime after lifting the crucible. That is unnerving.
 

Ed T

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In a past life, aluminum bronze was difficult to machine. It may depend on the exact alloy. The stuff we were using was continuous cast bar IIR.
 

Chips Ahoy

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I've not machined any of the "home brew" alumu-bronze yet. A friend who has said it machines ok but is tough on the band saw. Now he was just mixing only copper and aluminum. I am going to go ahead with adding tin mixture as third major component. I don't know when, but I will post the results when we have test machined a succesful pour.
 

awake

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I'm pretty sure I've read that aluminum bronze is the hardest variety of bronze - FWIW.
 

dnalot

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I have a steady supply of old propellers that are made of aluminum bronze for use in my foundry. Care must be taken to not work harden the material when machining. I find it machines well but can be a ***** to drill. It looks like brass but does not corrode or tarnish like brass.

Mark T
 

abby

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Zinc flare is very common in foundries casting brass but I have never experienced it with bronze or gun-metal (red brass in the states) as the zinc content is nil or very low.
The zinc oxide resulting from the flare can fall like snow , obviously not recommended for inhaling.
Use the correct flux and pouring temperature and you will minimise this problem.
Aluminium bronze is a useful alloy , as already stated it is often found as boat propellers , it is also common as the selector forks and sync cones in manual auto gearboxes. It looks like yellow brass but is much harder and has a slight pull to a strong magnet which is handy for recognition.
I have poured a lot of ally bronze when casting various replacement auto parts including knock-on wheel nuts for classic XK jaguar restorers. It is not pleasant to cast as the aluminium forms an oxide layer very quickly, the castings must be "bottom poured" to avoid entraining the oxide in the casting.
Shrinkage in uneven section castings also needs extra care in running and feeding to avoid cavities.
I have never tried to weld or braze aluminium bronze but silver soldering is nigh on impossible , or at best extremely difficult as the formation of oxide , even with strong flux , prevents the solder wetting and flowing.
When machining , tools need to be very sharp , I had an order for several sets of gear selector forks which I investment cast , these turned out to be very accurate needing only a reamer to take a thou or two from the slide bar holes , only a brand new reamer would touch the job !
I do not think there is any merit in using aluminium bronze as a bearing material over phosphor bronze which is far easier to cast and machine.
Dan.
 

awake

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Hmm ... I wonder if A/C Tig brazing (or welding) would be needed for aluminum bronze ...
 

MRA

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I've had drills seize in rock-hard brass - guess I now know what it is! It'll be fun to have a go at casting it, anyway. I have had a series of problems with a motorbike gearbox with not-particularly hard steel selector forks - it would be interesting to make some this way, but I still haven't progressed to investment casting. Perhaps this might be something good to try with lost PLA, if I could interest my 3D printing friend (who has the same bike!).
 

josodl1953

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Aluminium bronze is a particularly tough and heat resistant material. It is used for high -grade marine propellers for the navy and also for valve guides. I made valve cages for my Edwards. Drilling must be done carefully and indeed, rubbing and thus hardening of the surface must be avoided. Turning: no problem


Jos
 

Chips Ahoy

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Well now, Jos, that is interesting. Do you have a gut feeling how it might do as a cylinder on a steam engine?
Scotty
 

josodl1953

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I never heard of steam engine cylinders made of aluminium bronze but I'm more an IC than a steam man.
I agree with Abby that tin bronze or phosphorous bronze is more suited for applications where friction should be minimized. As far as heat resistance is concerned, temperatures in an steam cylinder are considerably lower than , for instance, exhaust valve guides in an IC engine ,which makes the need for a heat resistant material less important. Having said that, if you have ample supply of aluminium bronze, you can always give it a try.

The proof of the pudding is in the eating....

Jos
 

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