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Oxy welding bells

daedong

Plastic
Joined
Sep 24, 2007
Location
Australia
Hi, I cast heavy bronze bells consisting of 80% copper 20% tin, occasionally I have a cast that has some imperfections that I would like to simply fill with some sort of filler rod. I was wondering if any one can give me some advice on rod type and procedure in filling the imperfections? I have used silver solder but the colour is rather different.
 
Hi, I cast heavy bronze bells consisting of 80% copper 20% tin, occasionally I have a cast that has some imperfections that I would like to simply fill with some sort of filler rod. I was wondering if any one can give me some advice on rod type and procedure in filling the imperfections? I have used silver solder but the colour is rather different.

If you have a foundry, pour some extra melt into a trough made of angle Iron (set up on a "Vee") and use that for rod.
 
dougs answer for tig works,silicon bronze mig wire is pricey but also available. copper, maganese, silicon alloy. If you are darkening the bell you might be able to use phos-copper- that goo fills and sticks to anything copper related. bonus is relative low temp needed.
 
If you have a foundry, pour some extra melt into a trough made of angle Iron (set up on a "Vee") and use that for rod.

I don't have an alloy to look up but I'm guessing a tin copper mix would be pretty ductile, and cracking after cooling wouldn't be an issue?

Is an peening afterwards a good idea for a beefy casting or am I overthinking it?
 
Doug has the best option. Build your own tig rod out of existing same alloy.

The problems you may run into is color match, cracking issues (due to being a bell) or even a general 2 metals don't want to easily weld together.

But you never have any of those issues if you use the same base material.

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Doug has the best option. Build your own tig rod out of existing same alloy.

The problems you may run into is color match, cracking issues (due to being a bell) or even a general 2 metals don't want to easily weld together.

But you never have any of those issues if you use the same base material.

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I disagree on the cracking point. It may not matter on this alloy, but with many alloys your welds absolutely will crack if you try to use the same alloy for the filler. 5052 is one example.
 
I disagree on the cracking point. It may not matter on this alloy, but with many alloys your welds absolutely will crack if you try to use the same alloy for the filler. 5052 is one example.
I didnt know we were now talking about aluminum bells.

My fault.

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I agree with casting filler rods of the same material. Use standard brazing flux.

Generous preheat in a firebrick enclosure and let it cool down slowly afterwards.

In school we were taught to weld cast iron that way. Bronze should be similar.
 
Use TIG not oxy. Oxy requires longer to bring the bell up to welding temp. It puts a lot of heat into the bell. With TIG the heat will be localized.
 
I didnt know we were now talking about aluminum bells.

My fault.

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It's not just aluminum that has the issue. That was a single example of widespread concern across many alloys. I don't recall bronze having a particularly high elongation at break compared to other alloys that have this issue. I did not compare thermal expansion and other values, but I have seen plenty of bronze crack, and without any of the other alloying ingredients that bronze typically has, I think it is a valid concern to consider, at least with a test weld before messing up a casting.

Preheat and peening may help this.
 
If you have a foundry, pour some extra melt into a trough made of angle Iron (set up on a "Vee") and use that for rod.

Thats an idea, but i would like something with just a little lower melting point. So is there any thing that I can add to the bell metal that is 80% copper 20% tin?
 
This is one bell that I am debating whether to fill the small holes on the ridge as you can see. This bell weighs 17.5 Kgs so it will take a fair amount of heat before welding!

I have used at times 15% silver solder but the colour is not a good match

bellimperfection.jpg
 
Welding with filler material made at the same time/same alloy as the casting is a technique you should experiment with for repairs. However, it is still not a guarantee of a color match as the arc or flame will vaporize different amounts of elements due to the much greater heat than used in the original casting.

Another possibility would be to make a casting of the original material that could be used to make a plug. Possibly your sprue or riser could be used. The plug could be either pressed or threaded into a machined area.

That is a nice looking casting! More pictures of your bells and casting equipment would be appreciated.
 
Thats an idea, but i would like something with just a little lower melting point. So is there any thing that I can add to the bell metal that is 80% copper 20% tin?

The melting point lowers with increasing tin, but don't over do it. There's a phase change at ~75/25. Go past the phase change and all bets are off for solidification behavior.
 
The melting point lowers with increasing tin, but don't over do it. There's a phase change at ~75/25. Go past the phase change and all bets are off for solidification behavior.
The bell alloy i use is already 80% /20% but yes I think I will try making some filler rods around the 75/25

metalmagpie, the moulds for these bells take many, many weeks. its done by layer after layer of mud and clay then there is all the wax work that I do freehand. I have remelted plenty of bells due to failer as these bells are not done with any hi-tec method but rather the way they did it 1000 yrs ago with no-one to teach me.
 
The bell alloy i use is already 80% /20% but yes I think I will try making some filler rods around the 75/25

metalmagpie, the moulds for these bells take many, many weeks. its done by layer after layer of mud and clay then there is all the wax work that I do freehand. I have remelted plenty of bells due to failer as these bells are not done with any hi-tec method but rather the way they did it 1000 yrs ago with no-one to teach me.

I have done a fair bit of art type welding of copper, brass, and bronze and find as gbent says the color rarely matches bit it is not always hateful, I would be inclined as mentioned above machine/drill out the inclusion and make a plug to fit but slightly high then tig weld and grind/polish
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