I am trying to finish the gas welding part of the welding article and have managed to confuse myself when it comes to brazing. I know most, if not all, of you don't do it, and have good reasons for not doing so. I just don't remember why!

I know:
1. easiest of all welds to make (little skill)
2. lap joint as strong as the material joined
3. low heat (less distortion)
4. very quick to set up and do.
5. no splatter.

Cons:
1. butt weld not very strong
2. requires clean joint
3. not good for filling voids
4. left-over flux can lift paint and filler if not carefully cleaned after welding.

Can you guys help me? Tell me why brazing is not such a good idea?

btw, see http://www.handyharmancanada.com/The...k/contents.htm for an idea of the good parts of brazing.

 

I see brazing as being more application specific. It does have its place in the welding world. There are areas where it is benificial and other times not. If I remember right, AXracer is a jeweler. I bet he brazes on occasion with his line of work, he could probably shed a little more light on it for you. I rarely braze. The only thing I've ever thought about brazing is cast iron. If I have that to repair though, I usually just use a Nickle based rod and "butter" the base material being repaired and use a 7018 rod or just MIG out the rest. But, that is more for more "heavy" applications, and it's quicker.

What are you wanting to braze?

 

The problem is with electrolysis between the steel and braze, especially in damp climates.

 

53fatfnder,
We are writing a group article on welding for beginners. This is one of the sections of that article.

 

I braze a part if it is thin metal that I know I blow through with the mig. I reinforced the front corner holes on my hoods by brazing a flat washer to the top side of the lip, you don't see it from the bottom looking up. These are the holes in the front of the'48-50 hoods that like to crack and travel up the sid of the hood. Anyone with one of these trucks knows the area I am talking about.

 

I'm no expert for sure, but: You don't use brazing for butt welds, only for joints with large surfaces in contact with each other (lap welds). Also, although the temps are lower, they are applied over a larger area, so I don't agree with the "less distortion" in all cases. Another "con" is that if you try brazing and it doesn't hold, you'll never be able to weld it because the copper spoils the metal for welding.

 

for what its worth, brazing is good for joining dissimilar metals..like cast iron to steal etc...l

 

Like has already been stated Brazing has its place it all depends on what you are working on, and where it will be used. If working on a body panel the Mig or Tig is your ticket because of the heat. If working on Refrigration then brazing is you ticket.

 

When metal finishing prior to primer, metal that is brazed frequently is a harder compound then the surrounding sheet metal and does not metal finish nearly as smoothly as say MIG welds. IMHO.

 

Technically brazing is hot joining using a lower melting temp filler rod that forms a bond at the interface by creating a new alloy at the juncture a few molecules deep. The filler alloy bridges between the two pieces being joined, there is no actual joining of the two pieces directly to each other, so it can be separated again with a second application of heat to the joint. That's why brazing a but joint is not very sucessful, too little surface area at the joint and the bridging metal is often somewhat brittle. The problem with brazing in bodywork is that the joining alloy for steel is a brass alloy, and paint does not stick very well to brass. There would be a lot of people who polish brass that would be eternally grateful to anyone who formulates a clear coating for brass that won't eventually chip and peel off. brazing is fine for a low stress overlapping joint that doesn't need to be painted. I prefer using high tensile nickle "silver" rod for brazing steel over yellow brass rod.

 

Ax,
Could you replace the brass rod with the nickle one for bodywork? Would that help it hold putty and paint?

Also, can you lead in a brass joint? or a nickle one?

 

The nickle rod is a white brass alloy as well, that's why I put silver in quotes it doesn't contain any silver. I don't think you can lead over brass.

 

brazing uses alot of heat
also it doesnt require clean metal(atleast not mild steel)
easy to grind
can be used on alot of different metals
excellent for exhaust repairs just mig is cheaper

 

Nixer, you sure it does not require clean metal? All the books say it does - that the bond is only a few molecules deep and that any dirt or grease will stop the bond.

Have you brazed rusted mild steel?

 

*****,
Could you be confusing "Brazing" with "OA Welding"?

Brazing is more like a solder joint, where welding is actually melting/fusing the materials together.