Brazing...

[hilsideser]

What do I need for doing brazing work?
(I haven't done any in 30 years or so and need a refresher course.)

 

[GregW]

Hi Patrick,
Do you have a torch and tanks already? For brass onto steel, you'd want some brazing flux.

 

[hilsideser]

No. Been watching the trading news paper here called The IWANNA. Seen three or four sets with tanks come on.

 

[MGBGT_noob]

Will a propane torch provide enough heat for brazing, or do you need to use something hotter, like MAPP?

 

[PAUL161]

Propane alone will not give you enough heat, but used with oxygen it will. Oxygen and Mapp gas will give a little hotter flame than propane. Propane and oxygen are used almost extensively in the commercial industry due to it's lower cost than acetylene. Acetylene, the once standard of the industry, is more expensive than propane, but is still used where a higher heat range is needed.

 

[Scott_Hower]

Acetylene, the once standard of the industry, is more expensive than propane, but is still used where a higher heat range is needed.

Agreed. It's also highly unstable. "DA" is nasty stuff; I've been in an acetylene plant where it's being reacted and the cylinder fill hall where the controlled filling occurs; probably the scariest moment of my life. DA goes BOOM if filled too fast into a cylinder.

 

[PAUL161]

Acetylene, the once standard of the industry, is more expensive than propane, but is still used where a higher heat range is needed.

Agreed. It's also highly unstable. "DA" is nasty stuff; I've been in an acetylene plant where it's being reacted and the cylinder fill hall where the controlled filling occurs; probably the scariest moment of my life. DA goes BOOM if filled too fast into a cylinder.

If I remember correctly, the acetylene cylinders were internally insulated for that reason.
Right after I was discharged from the Navy, I went to work for Air Reduction in the manufacturing of liquefied gases. Good job, good pay, good benefits, but after 3 years working inside and a fair amount of desk work, I had to get out.

 

[Scott_Hower]

Acetylene, the once standard of the industry, is more expensive than propane, but is still used where a higher heat range is needed.

Agreed. It's also highly unstable. "DA" is nasty stuff; I've been in an acetylene plant where it's being reacted and the cylinder fill hall where the controlled filling occurs; probably the scariest moment of my life. DA goes BOOM if filled too fast into a cylinder.

If I remember correctly, the acetylene cylinders were internally insulated for that reason.
Right after I was discharged from the Navy, I went to work for Air Reduction in the manufacturing of liquefied gases. Good job, good pay, good benefits, but after 3 years working inside and a fair amount of desk work, I had to get out.

Correct. The guts of the cylinder contain a porous material into which the acetylene is dissolved.

Never heard of Air Reduction... I work for Air Products & Chemicals.

 

[vette]

Hi Patrick, I don't want to seem calus, but why would you want to braze. I feel that with the availability of MIG and TIG welders that brazing has become obsolete. I know every time I work on a car and I come across brazing I could just scream. You can't do anything with it after it has been applied. And it usually won't hold the job together for very long. Then, you can't grind it out without distroying the underlying metal and you can't weld on top of it. The only thing that you can do is to cut out the whole section. Sure creates a lot of extra work. If you have a special application requiring brazing I'd sure like to know what it is. Maybe you could find a used MIG welder for the same effort that you use to find the braziing equipment.

Dave C. "CHEERS"

 

[PAUL161]

Air Reduction, better known as "AIRCO", was officially formed on November 16th, 1916. The company's ties go back a ways. I think some of John Ds money was in there somewhere. Here's a certificate vignette with some background info. https://www.scripophily.net/airrecoinnew.html
Air Reduction Company, Incorporated - New York 1967

 

[angelfj1]

"Never heard of Air Reduction... I work for Air Products & Chemicals"

Surprised you don't know considering BOC is one of your largest competitors! :smirk:

 

[hilsideser]

Dave, you're not being calus, I'm ignorant.
I have a small mig with a tank on it and have used it to weld metal patches into the floor of the Spit. I am looking at the stress cracks typical of the Spit around the bonnet catch levers and at the corners of the head lights/ bonnet. You think this is a mig job as oposed to brazing?

 

[DrEntropy]

Braze will just crack again. Too brittle. And THEN you're really up th' creek as NOTHING is gonna "stick" to it afterwards. Knit it together with the MIG rig.

 

[Scott_Hower]

"Never heard of Air Reduction... I work for Air Products & Chemicals"

Surprised you don't know considering BOC is one of your largest competitors! :smirk:

Trust me, I know all about BOC. I spent 7 months living in Poland working the M+A integration deal.

 

[lawguy]

I did some brazing on my motorized bike project (see avatar). I used straight MAPP- which worked OK, but if i did it again, I would used MAPP with O2. However, on sheetmetal, MAPP isn't bad. I use brazing rods that were coated with flux, no extra flux. It is absolutely critical that the surface be clean with no rust- can't braze to rust. On a floor pan, I would prefer to weld if I had access, but I think it could be brazed. Problem is, it takes a while to get it hot enough (why i would use O2 with the MAPP).

I think brazing gets overlooked sometimes and it can be a great technique in the right circumstances.

 

[PAUL161]

Braze will just crack again. Too brittle. And THEN you're really up th' creek as NOTHING is gonna "stick" to it afterwards. Knit it together with the MIG rig.

You know Doc, we tried brazing roll bars on dirt track sprint cars back before Mig was in the norm, for more flexibility. but the strength wasn't there for a hard impact even though it would hold in a roll over. We went back to stick welding and aircraft type tubing. <span style="font-weight: bold">And, your right, paint wouldn't stick to it!</span>

 

[eschneider]

I've seen a few articles lately about MIG-brazing. Uses a brazing wire in a standard MIG machine, but I've read that it can be tricky to get the feed correct so that the wire doesn't get tangled.

I haven't tried it, but I plan to give it a whirl when I can find some time. My biggest concern is whether or not the braze will flow into the joint....

From an engineering perspective, brazing is stronger than welding in SHEAR loads, less brittle, and seals the weld area better. IF ITS DONE CORRECTLY (pretty rare)

most brazes I've seen consist of a glob of brazing wire haphardly bridging a 1/4" gap. Definitely not the way to braze.

MIG is definitely easier to produce consistent, reliable joints.