Brazing & Brass Rod question/problem...

[Tremdo]

Another newbie in brazing,

Little question after testing brazing with bronze.

I have try 2 types of bronze rod, the first one is a 3/32 flux coated (Lincoln Electric) bought at Canadian Tire. I have no problem to braze with that. Flow really well and get stuck to the metal like it supose to! hehe! I am also able to control the flow pretty well on that one.. But on the second rod type....


Second rod is a 1/16 not covered with flux, so i use a paste flux ( Bohemian / Cycle Design LFB ). I've heat that flux until it turn grey and start to be like a plastic finish, apply my bronze rod but... It make a drop, but the drop wont go on the metal part and get stuck on the rod. Finally able to drop the drop on the metal piece, it slip around the tube and fall beside somewhere on the table.. So it dont wanna sitck on the metal!

What i am doing wrong with that second set up?

[Eric Estlund]

It sounds like you may not be pre-heating the steel enough. If the bronze hits it and rolls it is because the rod is hot and the steel cold (causing it to re-cool, bead, and fall down).

[Tremdo]

It sounds like you may not be pre-heating the steel enough. If the bronze hits it and rolls it is because the rod is hot and the steel cold (causing it to re-cool, bead, and fall down).

Thanks a lot for the anwser, i will try to pre-heat the steel a little bit more somewhere on my next pratice.. . This happen only on non-coated flux rod that you have to pre-heat the steel/flux more..?

[Curt Goodrich]

Use the color of the steel more than the state of the flux as your indicator of temperature while brass brazing. The steel needs to be at the same temp as the melting point of the brass. Like Eric said, the steel wasn't warm enough.

[Tremdo]

So i've try back tonight.... I'm better with the flux paste set-up now! I pre-heated more the steel and you where right! It work! So i am happy about that, but now, it was really hard to have the bronze flow where i was trying to bring it. The bronze was flowing well out of the rod and stick well on the steel, but was stuck or just like getting cooler really fast once on the steel, still if i was putting more energy ''heat'' on that part! Result, small balls of bronze on the steel....

I'm using a #0 nozzle, is that enough? Was a canti braze on.

[Tremdo]

https://lh5.googleusercontent.com/-S...k/IMAG1179.jpg

https://lh5.googleusercontent.com/-U...0/IMAG1178.jpg

[Andrew R Stewart]

Looks like you need more heat still. For the flow step (what i do first) the rod should suck right in between the two pieces.The fillet step is done a touch cooler but the rod still should flow onto the joint, just not as quick as water.

Do you have a huge supply of bike bits to be using them to learn on? Most might just use pieces of scrap to learn with, being cheaper. Have you tried to make towers of brass standing up off a bit of steel? Have you tried to flow brass under a plate or sleeve? have you seen how hot steel need to get to burn a hole through it? Andy.