brazing...help pls..?

[joel]

guys,

what is the pressure i need to braze a cooper to copper tube and an aluminum to aluminum, using oxygen and acetylene.

thankz.

[taz24]

guys,

what is the pressure i need to braze a cooper to copper tube and an aluminum to aluminum, using oxygen and acetylene.

thankz.

Don't know about ally (I thought it needed special inert gas )
But for normal copper to copper 1 bar on the O2 and 0.5 bar for the acetylene.

taz

[Karl Hofmann]

I braze Alloy with flux cored brazing rods and a Mapp gas torch... Oxy Acetylene may be a bit ferocious unless you are very carefull.

[expat]

Brazing copper to copper is not the same as aluminium to aluminium. Brazing raises the copper to the melting temperature of the brazing rod and relies on a capillary action where as with aluminium you are actually welding. It's difficult, especially with a torch as you don't see a change in the colour of the metal. It brightens or whitens a little then caves in. If you're not accustomed to welding aluminium your best bet will be to learn with a MIG. I believe a co2 argon mix will work but in doubt just use pure argon. You'll need to reverse the poles on the MIG to if you were welding steel and the machine must be properly set (wire feed/amperage). Once you've mastered this you can try TIG which is a much more refined and delicate approach than oxy acet. It's TIG that gives those beautiful woven bead welds on stainless motorbike exhausts.

[expat]

Karl, how do you get on with that? I recently welded some aluminium with the oxy acet set with a very low flame. I used thin rods and 2014 flux, I (as usual) found it tricky. It holds but it's ugly. Do you get good results.

ps I'm not posting a picture of it, just read Peter1's sig and you'll understand why

[Brian_UK]

It's amzing where you can find it but...

Here on YouTube there are a few brazing videos that may be of interest.
http://uk.youtube.com/watch?v=ZojIpKCo4TQ

[Karl Hofmann]

Expat, The brazing rods that I use are very good indeed and I can get a very good finish now but it has taken me a long time to get it right. The problem with brazing alloy is that the subject and the rod have melting points that are very close together and so care is the order of the day, lose concentration and the job melts. I have also found that any area of the job that has even the smallest evidence of corrosion causes the braze not to flow, I use a stainless steel wire brush to clean first.. As I said I prefer to use a MAPP gas torch as the heat is over a wider area and is not so fierce and concentrated

[joel]

thanks...

this is what im looking for...

more infos will be appreciated. re: brazing oxygen-acetylene welding...

regards,

Don't know about ally (I thought it needed special inert gas )
But for normal copper to copper 1 bar on the O2 and 0.5 bar for the acetylene.

taz

[expat]

Thanks Karl, I'll keep an eye out for those flux coered rods.

[Vucko Antarktik]

HELLO!
Al to Al best results brazing with TIG AC/DC put on AC position for current and 20 to 30 Amps.
Electrode is Al wire 1.5 mm*mm
Inert gas is Argon

[Karl Hofmann]

Thanks Karl, I'll keep an eye out for those flux coered rods.

Expat, They are an American made rod but I bought them from the UK importer, Southern Sales, in Southampton for around £18 quid a pack. I've tried a lot of different alloy brazing rods and have found them to be about the best. Gimme a shout if you need more details, I'll get the details off one of the packs.

Problem with TIG welding is that it does require a lot of investment just to repair a few pipes

[sumant mathure]

Hi, For brazing copper to copper tube use small torch with 3 to 6 no, nozzel, at acetylene pressure 1 & oxygen at 4, & braze with 1.6 to 2mm Copper-phos rod with 0%, 2% or 5% silver. However for Aluminium, brazing use reducing flame with slightly low pressure. However use of flux & maybe 5% Silicon Aluminium alloy is better here.

Sumant Mathure.