forging bronze

B

boilermaker

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Aug 26, 2005
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G'day all, firstly let me say thanks to all for creating a place where newbs like me can come and ask all sorts of stupid repetitive questions (i know i've asked more than my fair share:jerkit:).:D
Here goes another one: Can bronze be forged relatively easily? are there any red hardness / crumbling problems to be aware of? I've got some 3/4" round i want to forge down flat for some knife fittings (namely Habaki) and i cant source any flat stock so this is my only option. thanks for all yor help in advance.;)
 
Heat it up to a dull red. let it cool to black heat and quench in a bucket of water. It is now annealed. Forge at room temperature, re-annealing as needed. Do not forge hot or it will crumble.
Stacy
 
This depends on which of the many bronzes you use. One of the most common is silicon bronze , which I would recommend. Alternate annealing and cold working is the way except that it doesn't have to be quenched as Stacy suggested as it's not a precipitation hardening alloy.
 
It all different. Some can be hot forged from a red heat, some can be forged from a black heat. You'll have to experiment with a piece. I recommend hot forging especially with heavy stock because it moves faster. If you are working with thin sheet or very small pieces then anneal and cold forge. A pair of copper tongs is a nice thing to have. Steel tongs tend to mar the bronze.
 
If the bronze has a natural turquoise colored patina, it can burn off in the forge. It will show a green flame when this happens. If the surface of the bronze is clean, there shouldn't be any fumes from forging it, as far as I know.
 
Will: There should be no fumes unless you melt it.
mete: I often quench to speed the time up after it had cooled to below 700-800F.This allows easier handling of the bar stock.
All: Yes, I was assuming that he would be using silicon bronze (forging bronze). It can be forged at low red heat, but it will crumble if you get it too hot. Since Boilermaker has never forged bronze, I thought it best he start cold and work up to hot forging.
What I do with thicker material is heat it to red and start forging as soon as it loses all color (black heat), or at the lowest red I can detect. I have accidentally ruined pieces that I was forging and started too soon.
Stacy
 
The only time I forged bronze I tried it several ways and a red heat was the only way I could get it to move. It was 1" round in its first life as a door panic bar from a fire station. Heating to red, quenching, and forging cold did not work.
 
I find that the best way to deal with bronze is to cast it(either lost wax or sand) to as close to final shape as possible then forge if necessary. I have found bronze to work harden quickly, and if worked hot to start to crumble before serious dimensional reduction has occurred, on the other hand it sand casts beautifully (use 20 mule team borax as a flux on top of your crucible)
Use good ventilation, especially if you are not sure of your alloy, some brasses have lead to make them freemachining, if it is more of a brass than a true bronze it will likely have zinc (if you get a heavy white vapor make sure you do not breath it!)
Bronze is a great metal, I like using it for things I can cast. I hate brass.

-Page
 
Here's my miniature leaf blade ,6" long, made from silicon bronze .Anneal /cold work cycles starting with 1/2" dia.It takes longer .No fumes.Are some of you confusing bronze with zinc ? Bronze has no zinc, it's brass that has zinc which can be a problem .
 

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mete said:
Here's my miniature leaf blade ,6" long, made from silicon bronze .Anneal /cold work cycles starting with 1/2" dia.It takes longer .No fumes.Are some of you confusing bronze with zinc ? Bronze has no zinc, it's brass that has zinc which can be a problem .
Click to expand...

True bronze has no zinc, some of the jewelers bronzes do, I figured that while I was putting out a suggestion of melting and casting the bar of mystery metal that I would put out the caution. I had a student bring me a bar that he had bought as bronze that laid out a heavy white fume as soon as we got it up to approaching liquidus, kind of sobering!

-Page
 
Quenching from a red heat in (cold) water to anneal bronze (as opposed to air cooling) also has the advantage of establishing a more refined or smaller grain structure. This produces a tougher less brittle piece of bronze than a course structure would...

So, prior to work hardening, cold forging, or fabricating,… annealing in this manner would be a good idea.
 
Thanks all for your replies, I got the bronze from a local hydraulics shop where they use it for bushings the guy at the shop said it was S17? (i think thats what he said) bronze so i assume the S means it's a silicon bronze. As far as the fumes go i've been a welder for 12 years so unfortunatly have breated in my fair share of zinc fumes (had gal fever quite a few times and it aint pleasant:() an old timer told me once years ago that drinking milk before hot working any gal material goes some way to allieviating some of the effects from any of the fumes that may be ingested dont know if this is true though? wear a respirator or hold your breath and hope for the best?:D
 
http://www.copper.org/homepage.html
Copper alloys break into "wrought" and "castable". The range of bronzes (a copper alloy) breaks that way, too. In the link, goto "Standards and Properties" under "Resources and Tools". If you fuss around there, you'll find lists of alloys with links to properties.

Copper.org is the most helpful professional association I've dealt with... you got questions, ask and they will answer.

Mike Krall
 
Just an FYI, but this thread is eight years old.

I can't say that I ever tried to forge aluminum bronze. Normally silicon bronze is what is forged. I would think the aluminum would make forging problematic. I have never seen it mentioned in brass/bronze hot work information.
 
Might be 8 years old but I just purchased 2 15lb ingots of Silicon Bronze. I need to forge it down so it has been a very useful refresher for me. As to the Alum Bronze, not sure how it forges but it is a bear to grind or mill. As bad or worse than 304/316.

If you have to ability I would mill it rather than forge it. In fact that it how I reduced it when I have used it in the past.
 
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