Tig brazing advice needed !

[Premiershipman]

If anyone could help with regards to tig brazing copper to copper and copper to brass it would be greatly appreciated.

Currently i am trying to braze 2mm copper into shapes using copper circles and half circles and then brazing on a brass rod to make bubble wands.

I am using Sifsilcopper 968 to braze but i am having trouble getting it to braze without overheating the copper to the point where is starts to melt. I have also tried to braze the brass rod but it ends up leaving a white/yellowy residue without really brazing well.

I have the machine set to about 40 amps and seem to get fairly decent results around 35 amps for the brazing copper to copper but it is hit and miss.

I am using sifsilcopper 968 filler rod which weldability advised to use, but its 1.2mm diameter which i know the diameter is small but its all i have, i could maybe purchase some 2.4mm filler rod if that may improve the situation or would some people suggest using sif bronze no 8 ? Or should I try using copper wire as the filler ?

Thanks for any advice people may have.

Shady

 

[Shox Dr]

I've brazed a fair bit of copper, you are better off using a 2.4mm with a rounded or slightly chamfered end.

Amps are ruffly 1/2 to a third required to welded at. I find a pedal invaluable.

This is 2" tube Well some of it

 

[Premiershipman]

Cheers shox, i wondered if i would be better switching to sifbronze to create a better weld contrast against the copper and if the sifbronze would be better for the braze onto the brass rod as i only seem to be boiling out the zinc in the brass rod.

 

[Will_Davis]

I've brazed a fair bit of copper, you are better off using a 2.4mm with a rounded or slightly chamfered end.

Amps are ruffly 1/2 to a third required to welded at. I find a pedal invaluable.

This is 2" tube Well some of it

That is some interesting piece of kit!

Beautiful brazed seams!

Excellent craftmanship!

Err, What is it???

 

[Shox Dr]

That is some interesting piece of kit!

Beautiful brazed seams!

Excellent craftmanship!

Err, What is it???

Thank you, as for what it is. Can't say. Lets just say it doesn't move much



Just noticed didn't say what I used: Sif No8

 

[Titus A Duxass]

Thank you, as for what it is. Can't say. Lets just say it doesn't move much

Got that one.

 

[garethp]

Thank you, as for what it is. Can't say. Lets just say it doesn't move much



Just noticed didn't say what I used: Sif No8

Nice looking sculpture

How did you form the coil at the top? I've thought about several projects that would involve making copper coils and I've never really come up with a way of forming them neatly.

 

[pedrobedro]

Still trying to figure out what it is

 

[gordon stephenson]

Nice one pedro!

 

[500e]

Still only moves when the revenue's arrive

 

[Premiershipman]

Anyway, getting back on track !!!

Should I step down on the tungsten size to 1.6 from 2.4 to reduce heat input, so i get some sif bronze 8 to try ??

Bear in mind that it takes 2 days and £20 to get any welding rods shipped to the IOM as local suppliers just dont have the stock that uk places do.

Trying to kind of replicate an oxy acetylene brazing setup using tig, mainly as i cant afford oxygen and acetylene/propane rent along with the other bottles !!

 

[Buzza]

Looks like some sort of customised exercise machine

 

[Shox Dr]

You'll not get the capillary action using TIG as a heat source: it's too localised. And the rods don't flow as well, whether that's due too the lack of overall heat or not I'm unsure, Hotrodder might (no might about it) have a better idea.




As for the coil it's 8mm plumbing copper formed around a suitable buck. It didn't require any prep, just took my time.

 

[jacky-s]

Nice reply Shox Dr i think the clue is in it doesnt move (still),,

 

[cardiffrob]

Off the original topic somewhat, but...

Looking at that coil reminded me to mention a nifty trick for a heat exchanger.
On my aeroplane I needed to get exhaust heat to warm air round the pipe to duct up to the carb (via a valve) to keep the carb from icing up. To help get heat into the air I needed a very long spring of the type used in the colonies to keep mosquito doors closed but they aren't commonly used in Wales.
I was advised to get a sodding great long piece of metal rod, stuff it in the chuck of a drill, wrap a piece of stainless locking wire round the chuck and then let rip. In seconds you have a very long coil, so long as you feed the locking wire along the length of the rod as it winds.
If you feed another length of straight wire down the middle of the coil you can use it to hold the coils tightly against the exhaust tube. Then you only need to cobble together 2 stainless disposable propane/butane gas torch canisters to act as a T-piece collector and duct, if you see what I mean. Nifty trick.

Sorry about the lack of brazing info. Only done it once (Sifbronze 8) and it worked OK on steel.

 

[hotrodder]

You'll not get the capillary action using TIG as a heat source: it's too localised. And the rods don't flow as well, whether that's due too the lack of overall heat or not I'm unsure, Hotrodder might (no might about it) have a better idea.

I'm making it up as i go half the time. I think the intense/localised heat source is the biggest reason too. The traditional brazing wires have a lower melting temp, a little under 900C while CuSi3 (sif968) and phosphor bronze (#8) are in the 900s to just over 1000C range*. That's not gonna help for the job at hand since pure copper melts 1084 and brasses less than that, down to 900ish depending on flavour and then there's the zinc volatisiation...

Playing around with tungsten preps (arc shape) and increasing arc length to help spread the heat might help but i think it's really a case of there being a very narrow line to walk for TIG brazing copper alloys as the melting points of everything are so close. Not done much as i only really use TIG brazing on sheet steel, usually zintec. I typically use a lay wire technique i.e. filler in/on the joint and run the arc over it. When it comes to copper it always seems to be something where colour match is the biggest deal so i weld using strips cut from the parent material- usually c101 or c106 pure copper.

*according to the numbers i'm looking at #8 is more a case of a wider 'mushy' range than a lower melting temp... 930 - 1060 versus 980-1020 for the CuSi3. Zinc boils at 907C

 

[Tigman]

I call that " Hard Soldering " get the copper cherry red using oxy/acetylene and paint the joint with the hard solder rod , the solder follows the heat ! Brazing is yellow in colour ( brass ) When joining copper tube together one end of tube is belled out the other sits inside and a Brasing Rod and Unibronze flux powder is used to brase the joint it is like welding ! I think the Tig would do this ok .

 

[TD4]

What is it

If it tastes as good as it looks you'l be very happy. I have something similar. Malcolm.

 

[Seano]

FWIW, take a look HERE for a behind the mask demo.....

 

[oggy]

I used to use a tig welder to join copper to copper to make oil coolers for range rover classics,No rods just the tungsten to fuse the two together.