Upgrading to bronze from aluminum

[Swede]

I've always enjoyed foundry work, but have limited myself to aluminum so far. I've got one of the old "Pyramid" brand furnaces, the company that used to advertise heavily in HSM magazine and other hobby 'zines, and I've always been impressed with it... it appears to be a pretty capable and gutsy furnace for its size.

Can I use this for bronze? Would anyone care to offer any tips beyond "toss in the scrap and see if it melts." I'm not looking to be spoon fed, but more interested in comments like "Works great, easy to do" or "It's pull your hair out difficult."

I am aware of the dangers of zinc in brass. How about bronzes as far as safety? Lots of them contain lead... Mr. Internet says lead boils at 1740 C, while Cu melts at 1084 C. and tin much lower, so I'm assuming a copper-tin alloy will melt around 1100 C. and the Pb will NOT boil off.

Can I use my petrobond sand?


Here's a pretty good table of melting points I found.

http://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html

 

[ShedBoy]

I keep meaning to chuck some in an see what happens, I know it is hotter and bronze can range from easy to machine to OMG what is this evil metal I have produced. Good question and i will be following the answers.

Brock

 

[JorgensenSteam]

I have seen some use petrobond with cast iron, so I would say it is ok with the lower temperature brass/bronzes.

I have not melted brass/bronze yet, but I avoid inhaling the fumes regardless of what I am melting. I also avoid standing downwind of the furnace exhaust.

I have toyed with a forced air respirator, but it can be cumberson when you are trying to handle and pour molten metal.

 

[maury]

Swede, Yes, petrobond works very well with bronze. I cast what I call junk yard bronze. I use mostly what the junk yard calls red brass. It has zinc, lead and tin in alloy with copper, and is a reddish coppery looking bronze. I pour it at 2150 F. As far as the sand goes, I use 120 to 150 grit sand, and get an excellent finish. Some folks take out the burnt sand each time they shake out a mold, because that should mulled before reuse. I usually do about 5 molds in a pouring day and when I shake out the mold I do it into a large tub. I do not separate the burnt sand, but I break up the clumps, spread it around, and add a bit of oil while the sand is still hot. Then I mix it with a small shovel and let it rest a month or so. That way, you only have to mull the sand when it fails the handshake test.

If you want to see a few of my bronze castings, check out the "Birth of a Swan" thread in Engines from Castings on this board.

As always, avoid breathing anything that comes out of your furnace. Usually there is enough breeze to give it a direction, always stay up-wind.

For a lot more detail, get the Chastain books on casting. I have vol.2, and to me it is excellent, it has more information per page than any other book I have ever read.

maury
www.lonestarengineworks.com

 

[Swede]

Thanks, Maury, great stuff! Bronze is one of my favorite metals... it'd be nice to cast some one of these days. While pricey, one can still find a lot of scrapped bronze plumbing fixtures begging to be melted down.