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Workability of Bronze?


#1

Hello everyone,

I have taken interest in working with bronze lately, I just really like the colour. I have been wondering however on whether it is ductile enough for cold working. I heard that as soon as the tin content exceeds Cu92Sn8 That the alloy is embrittled. Is this true? I especially enjoy the reddish yellow of Cu90Sn10 or even more of Cu88Sn12 However I fear these alloys will break under severe stress of hand fabrication. I know for a fact that Cu94Sn6 or Cu97Sn3 will be very ductile and able to withstand severe mechanical stress but these alloys might too red for my liking. Could anyone shed light on whether the higher tin bronzes can be worked cold? Or maybe the colour of the lower tin bronzes will be nice enough?


#2

We cast with bronze in college and it is hard and on the brittle side. I think if you didn’t have to do a lot of hammering and bending though you could solder and fabricate it. It might be more of a braze than a solder. Probable could deform it enough to dish out flat sheet also. My rule in metalsmithing is don’t let someone tell you you can’t do something. Go try it. Some old teachers were just taught by some other old teacher who may or may not have been adventurous. Who knows what they learned. It’d be cheap to experiment with. SD


#3

Thanks I will be trying out some bronze very soon.


#4

Technically everything we call silver soldering is in fact brazing.

Tony Konrath

tonykonrath@mac.com


#5

I regularly as a metalsmith hammer sheet bronze into various forms, and alloys up to 7% tin have never cracked even under the most punishing hammer blows. However I once had the chance to play with a bronze used for bells, which contains much more tin (around 20%) and found it very brittle, even after careful annealing. I have long been fascinated by the various colours of copper alloys; tin has a slow grey whitening effect on copper as you increase the amount, whereas zinc has a rapid yellowing to a bright gold, and silicon to a somewhat dull gold. Nickel has a rapid whitening effect with a slight greyness. The red colour you mention for some of the alloys makes me suspect that other metals (which are always present in commercial alloys) may be significant.