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Old 11-28-2009, 11:49 AM
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Ries Ries is offline
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Join Date: Oct 2004
Location: Edison Washington
Posts: 1,154
Re: Silicon bronze sheet?

Muntz metal is a trade name, not an alloy name- so it can vary a bit from mill to mill, but generally its either

C365, which is 60% copper, .6 % lead, and 39.4% zinc

or its
C370, which is called "free machining" muntz, which is 60% copper, 1% lead, and 39% zinc.

Either way, its hell to weld.
The zinc and lead boil off, bubble, and release toxic fumes.

Best way to weld it is to tig weld with a silicon bronze filler rod- you wont get a great color match, and there will still be some porosity in the weld, but it will stick, structurally. You may be able to gas braze it with flux- never tried it, but it might work. Again, get it too hot, and the lead and zinc will drive you nuts.

It was never designed to be a weldable alloy- its for cold forming and machining. Maybe a bit of hot forming, at relatively low temps in big presses.
It is used for condensor tubes, screw machine parts, and other stuff that is mostly machined.
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