Forging Bronze

[Alex Zandonella]

Hello everyone!

 

In a few weeks my girlfriend has her birthday and as a present I wanted to make her a bracelet made out of bronze so I went to my steel supplier and got a round bronze rod (25mm). Today I wanted to try forging it, after a few attempts it just kept cracking and breaking it apart. I looked up what might be causing it. Apparently it should be how the allow is made up. If there's to much zink and lead it makes it brittle. My Bronze is called here in Italy RG7 and the datasheet says about a 1,5 to 11% tin and 1 to 9% zink and some traces of nickel and lead. So technically it should work for forging. The right temperature should be on a dull orange. I tried it a few times with no success. I tried forging it cold, it worked a little better but still opened little cracks. I tried heating it up more but obviously it just started melting on the outside. Some even say that you should hit it gentle so after failing with my 4 pound hammer I tried it with my 2 pound hammer, no difference really... So I'm a bit frustrated now, not knowing what I really do wrong. Attached you can see some pieces that broke of. My guess might still be that the bronze is not suitable for forging, but as I'm not sure I wanted to ask you guys for your opinion. If it all doesn't work I might switch to copper even though I preferred bronze for the bracelet.

 

Greetings Alex

 

[Geoff Keyes]

This may help

Bronze

[Charles dP]

I’ve only tried forging bronze once and failed. Mine also crumbled on the 2nd or 3rd heat. If I remember correctly my research after indicated that I should have annealed (softened) the bronze after every heat by quenching it (i.e. heat, beat, quench, repeat). I may be wrong so hopefully somebody can confirm either way.

 

I just had a look on YouTube and there appears to be some hits on forging bronze. Have you had a look there?

Edited September 24, 2022 by Charles dP

[Gerald Boggs]

Forging brass (what everyone calls bronze) is tricky.  It's been years since I've forged any, so I'm working from long memory.  First, you're going to have a lot of trouble forging down in size, I've never known anyone that even tried, I've only forged it into tapers and easy curves for architectural work.  As for heat, it's like aluminum, using paint stir sticks (soft pine) to test temperature, forge when the brass is hot enough to burn the stick and stop before it cools down too much.

Edited September 24, 2022 by Gerald Boggs

[Gerald Boggs]

On 9/24/2022 at 6:02 AM, Alex Zandonella said:

datasheet says about a 1,5 to 11% tin and 1 to 9% zink and some traces of nickel and lead.

Interesting range of elements.  I looked up RG7 and came across this data sheet from Smiths of Britain.  With the stuff Smith has, the lead amounts are quite high, 5 to 8 percent.  This is way outside my knowledge set, but lead will melt on the kitchen stove, I don't know what effect that will have on heating it to forging range, but probably not good.  Plus there's the con with breathing lead gas and later, wearing something with that much lead.

https://www.smithmetal.com/pdf/bronze/rg7.pdf

Edited September 25, 2022 by Gerald Boggs

[Alex Zandonella]

Thanks for everyone replying!

 

 

20 hours ago, Charles dP said:

I’ve only tried forging bronze once and failed. Mine also crumbled on the 2nd or 3rd heat. If I remember correctly my research after indicated that I should have annealed (softened) the bronze after every heat by quenching it (i.e. heat, beat, quench, repeat). I may be wrong so hopefully somebody can confirm either way.

 

I just had a look on YouTube and there appears to be some hits on forging bronze. Have you had a look there?

 

About the quenching. When you anneal it doesn't it loose those properties again when you heat it up again? I mean I can try it, those pieces that crumbled of can still be used for casting sometime in the future.

If seen the video where Alec Steele was forging a bronze plate, when he worked it, it just seemed to work perfectly, didn't crumble at all, but then again he probably used bronze that's better for forging.

 

2 hours ago, Gerald Boggs said:

Interesting range of elements.  I looked up RG7 and came across this data sheet from Smiths of Britain.  With the stuff Smith has, the lead amounts are quite high, 5 to 8 percent.  This is way outside my knowledge set, but lead will melt on the kitchen stove, I don't know what effect that will have on heating it to forging range, but probably not good.  Plus there's the con with breathing lead gas and later, wearing something with that much lead.

https://www.smithmetal.com/pdf/bronze/rg7.pdf

Thank you for warning about the lead gas, I didn't even think about it!

I'm sorry for the stupid question but if it melts on such a low temperature shouldn't it just melt of from the allow when heating it up to forging temperature?

One thing I noticed aswell was where it crumbled sometimes there were yellow like stained spots that disappeared when it cooled down.

 

But nevertheless shouldn't it be possible after annealing it to forge it cold?

Edited September 25, 2022 by Alex Zandonella

[billyO]

26 minutes ago, Alex Zandonella said:

When you anneal it doesn't it loose those properties again when you heat it up again?

With non-ferrous metals, heating to a red heat and quenching does the opposite  of what happens with carbon steels.  This softens the material, allowing you to work it without cracking.  As you work the piece, it gradually gets harder and harder (thus the term work-hardening) and it will start to crack unless you soften it again.  Depending on the size of the piece and the amount of reshaping/work you are doing, this may need to happen many times during a project.

So what @Gerald Boggssaid about the process is true:  Heat>quench>hammer > heat>quench>hammer...

32 minutes ago, Alex Zandonella said:

shouldn't it be possible after annealing it to forge it cold?

Possible, but depending on the alloy one might not be as easy as others

[Jaron Martindale]

I'm not currently at home to consult my big book of metal properties( thrifting buy, nice big tome of ferrous and non ferrous chemical make-ups, common uses, ways to work it, etc etc; it does a good job of making sure people like me without a background in this stuff make good sense of it all), but I believe when I got asked to forge a sword from bronze I used 954 Bronze.

https://alloys.copper.org/alloy/C95400?referrer=facetedsearch

The book I have referenced the good forgeability of 954 due to the 3-5% of iron, especially for those of us used to steel.  Whether this is exactly true or not I'm not sure, but as long as I didn't overheat it (below a bright glow, dull glow worked fine with softer hits) it seemed to forge and bevel just fine.  Caveat for 954 is it's a water quench bronze, so it will not anneal when quenched like copper would,  you have to let it anneal similar to how you might thermo-cycle/normalize steel where you heat and let cool in still air.  This is the same alloy I believe Alec used in the video you mentioned, and is the same effect he stumbled upon.  

**Anyone with real knowledge in this area please feel free to correct me!**

 

This is a page for large blocks of 954 from Coal Iron Works, and at the Bottom is a Video of Josh Weston and David DelaGardelle Designing and Forging a MONSTROUS bronze sword!  Worth a watch if you haven't seen it yet.

https://coaliron.com/collections/steel-sales/products/aluminum-bronze-square-stock

 

This is that "executioners sword" I was asked for by a client...please don't judge me..

 

As a note, I'd like to say trying to find a Bronze alloy to forge was extremely irritating and time consuming.  I consulted A LOT of more experienced makers, including David, before I bought my bronze.  Hopefully this at least helps point you in a decent direction.  I hope the Bracelet turns out Beautiful!

[Dan Hertzson]

I have some silicon bronze that was sourced from discarded survey markers like the one in the photo below.  It forged pretty well, hot, though it was important to keep it just barely in the dull red range.  I heated to dull red and forged till it stopped moving, then repeated.  Picture to the right are items made from one of these markers.  Lovely material once you get used to it.  All punching was done hot.

 

Brass is completely different, at least the stuff I got.  There I did the anneal and quench route.  Still has a tendency to work harden and crack if you aren't careful.  

 

 

   

[Gerald Boggs]

2 hours ago, billyO said:

So what @Gerald Boggssaid about the process is true:  Heat>quench>hammer > heat>quench>hammer...

Actually, I didn't say that, as I don't know :-)   We forged all the bars hot, but we were mostly just drawing out tapers on the power hammer.

Edited September 25, 2022 by Gerald Boggs

[Alex Zandonella]

I'll try the heat-quench-hammer routine tomorrow and let you know how it worked. In case it shouldn't I found on my suppliers website another type of brass, the alloy index in Italy is CW617N. So basically he just offers those to types of bronze alloys. I'm not sure about the index internationally, but a datasheet from Germany explains that this type of brass should actually work good for forging and similar stuff.

Description says, 58% copper, 2,5% lead, 0,3% Nickel and 0,3% of iron, 0,05% aluminium, 0,3% tin and the rest should be zink. So what would you guys say? Shouldn't there be a little more steel and aluminium?

 

There's more to Bronze that hits the eyes first. I thought as a soft material there should be no problems, bronze definitely proved me wrong. But hey we learn from our mistakes, don't we?

[Matt Walker]

https://www.anvilfire.com/21st-century-blacksmithing/brass-bronze/

[Gerald Boggs]

On 9/25/2022 at 5:14 PM, Alex Zandonella said:

I thought as a soft material there should be no problems

Bronze, as in a blend of copper and tin, isn't soft.  It's one of those little oddity's in metallurgy, two soft elements blended together form a very hard metal.   I read somewhere that some bronzes can be as hard as medium carbon steel.  

Edited October 29, 2022 by Gerald Boggs
Metallurgy not meteorology :-)

[Jeff Amundson]

I made this in bronze because it lives in Hawaii. I forged it using silicon bronze, C655, which is 97% copper and 3% silicon. It crumbled if forged too hot. I would heat it medium red (best in a dark room), set it on the anvil for a few seconds, and then it would forge beautifully. It forges cold, too, until it work hardens. Heat and repeat.

[billyO]

8 hours ago, Gerald Boggs said:

Actually, I didn't say that, as I don't know

in re-reading this thread, I have no idea why I thought you did.   

Sorry 'bout that. 

 

Edited September 26, 2022 by billyO

[Jeroen Zuiderwijk]

Tin bronzes are red short, so they crumble if you try to work them hot. If shaping them, it should be done by cold working with regular annealing. Lead in the alloy doesn't help with coldworking, as it can cause earlier cracking. It's why bronze is generally cast, rather then formed by forging/coldworking. Among modern bronzes (aluminium or silicon bronze) there may be alloys that can be forged as mentioned above.

[Alex Zandonella]

So to finish I tried again with Brass. It worked a lot better. But still it wasn't easy to work with, I was not able to make a bracelet I wanted. After a few attempts I was able to make a simple bracelet and a leaf key fob. Then I thought I'll just try it with copper and boy was that a pleasure working with copper, after my first try I got it down as I wanted it. I'm satisfied with the result I'll add a photo of my finished attempts.

[Eric Niefert]

I found architectural 385 BRASS super easy to forge.  Here is the stuff I use from McMaster Carr.  

 

Easy-to-Machine Architectural 385 Brass Bars

 

• Yield Strength: 16,000 psi
• Hardness: Rockwell B40 (Soft)
• Temper: See table
• Heat Treatable: No
• Specifications Met: ASTM B455

Often called architectural bronze, 385 brass is easy to machine and has excellent formability when heated. It is typically used for handrails, ornamental trim, and hardware, such as hinges and lock bodies.