Brazing Defects Solutions

Cooling the joint too fast can cause this problem.There must be time for the gas to escape while the solder is still liquid.Increase your heat cycle time.

Hi ， thanks for your good input. In my opinion, this kind of design, melted filler metal fill the gap in two direction. Too much gas need float out. In brazing joint design, this kind of joint should be avoid. Can you agree with me?

Very good and smart idea. Thanks! Is this method often used in biger parts brazing?

I agree with "Just an Engineer", remove one of the rings and be ready to add additional braze filler by hand.

Also, I would slip the copper pipe over a mandrel and "ping" it 4 times with a center punch, equally spaced around the pipe. The displaced material of the center punch ping, in two separated rows, will give it a "stand off", centered gap around it so that the brazing alloy filler can access the joint 360°, top to bottom. I hope that you have a slip fit of about 0.005", or 0.0025", at least, per side, for the braze filler material to occupy. Any greater than this and you will loose the ability of the joint to hold pressure or tension, if that is a concern. This seemingly tight clearance will allow the pings of the center punch to do their job of "stand off", in the joint.

Cu copper, P phosphorus, Ag silver. Commonly called Silfos™.

Thanks.

Basically silver soldering.

Actually,it is better than silver brazing,and it is much easier to work with.

Silver solder is much more expensive,and silver in contact with copper and acetylene gas can cause unstable acetylides.

I have used Sil-Phos for many years in HVAC applications.

It wicks well into loose joints and is vibration resistant.

I would suggest using a thin sheet of brazing material,of the size and shape of the parts to be joined.

Also before applying heat,it is important to know that most fluxes are approximately 15% to 30% water,so the flux must be removed thoroughly before applying heat or the steam generated will cause problems such as yours.

Good luck.

PN: If you are using Sil-Phos 15 ,no need for flux.The phosphorus in the alloy acts as a flux.

"... the flux must be removed thoroughly..."

Do you really mean that? I'm accustomed to heating very slowly to evaporate the water and melt the flux before increasing the heat to brazing temperature.

Thanks for the comment on Sil-Phos. I was not aware of that.

Flux is acidic.It will cause corrosion in the long term if not thoroughly removed.

The corrosion may not show up for a long time,but I am sure you have seen copper with a green edge around the solder joint.

This is corroded copper,and eventually,it will fail.

This is the recommended procedure for brazing or soldering.

True, but in that post, you said "...the flux must be removed thoroughly before applying heat or the steam generated will cause problems such as yours...."

I read that to mean you remove the flux before applying the heat to braze. Most fluxes don't become active until they are heated, so that would render the flux useless.

I've always: apply the braze filler and flux, heat slowly to evaporate the water content of the flux, heat to brazing temperature, cool to warm, then remove flux.

Am I missing something?

You are right.

I simply pasted from an article from a welding supplier on line and did not examine it properly.

If the OP has the gap clearance correct,and the metal is cleaned and fluxed with the proper flux,he should have no problem with applying the filler at one end.

Any gap over .005" is losing strength and can cause capillary failure.

I sent him a link with very detailed information on brazing.

The hardest thing to braze for me is aluminum,it does not change color when heated to brazing temperatures.

Tempil pen indicators are good,but they are not sold singly,and I do not do enough aluminum to justify buying a whole box of them.

I use the oxidized soot method to judge heat of aluminum.

There are some alloys that are low temp "brazing" (Muggyweld) for aluminum but anything below 800F is considered soldering,not brazing.

Thanks for catching my error.!

Here is a link that will provide valuable information and guidance on brazing.You may need to use Black Flux for your application.At any rate,there should only be one location for the brazing filler.It has metallic boron in it that is ideal for induction brazing.

Read the whole link.There is much information there.

https://www.lucasmilhaupt.com/EN/Brazing-Academy/Brazing-Fundamentals.htmhttps://www.lucasmilhaupt.com/EN/Brazing-Academy/Brazing-Fundamentals.htm