Oxy fuel brazing brass

[Chris Cramer]

I'm really struggling in just brazing heavy brass. It's said that the process is just the same as soldering with a torch. I tried using flux paste, as well as flux coated bronze brazing rods; and it's easy enough to bind the solder as that is all that melts; but unlike silver soldering it does not bind to the base material even when it is very clean without managing to melt the surface of the base material and fuse it with the pool of solder. If you ask me that is more like welding, but brazing and soldering should still hold without fusing the metal.

 

[Johnwa]

With brazing or soldering the base metal has to be as hot as the rod or solder you are using but doesn’t melt. So you can braze material that has a higher melting point than your brass rod. Since you’re doing brass on brass I would call it welding.

 

[RobinHood]

I'm really struggling in just brazing heavy brass.

I wondering if you need to preheat (in a BBQ for example) the part? It almost sounds like your part is sinking too much of the heat away.

 

[Chris Cramer]

Ah, I figured it must have been because of the lower temperature of the base brass. I was brazing the parts of the hilt and guard of my fantasy sword that were recently cast. They are all about half an inch thick so it was very difficult to bring both parts to a high enough temperature by how much heat dissipation brass has. I got the welding to work by using much more gas with the torch. I lost a lot of gas as I struggled to get the solder to bond to the brass.

 

[Mcgyver]

Why not just silver solder? right stuff for the job imo. Bronze rod melting temp is too close the brass's melting temp (1600 and 1700F). Silver soldering is brazing btw. (brazing is technically defined as when the stuff melts at over 850F). SS has very high tensile strength, 8-10 that of soft soldering. Typical SS melts at like 1300F so you don't end up with that expensive brass turning into a puff of zinc and puddle on the floor.

Once you get things clean, get used use lots of the right flux and avoid direct flame, SS is fairly easy and gives great results with brass

 

[Chris Cramer]

There is a big difference between brazing copper pipe or thin brass stock, and brazing heavy brass or copper. You need to heat almost the entire peice of brass to bring it to the right temperature, and the amount off heat that is built up in the stock is much higher than any flux will melt. Soldering thin stock is easy, because you basically apply the flux and solder and heat the stock a distance from the joint and allow the heat to travel to melt the solder and flux. In that case the solder will follow the flux.
When crafting something with cast brass or bronze, I would always avoid using silver solder because it would stand out from the rest of the peice which I want to look as good as possible after it is polished.

 

[Chris Cramer]

Being heavy brass Im thinking it would probably be best to tig weld it together; but I am out of argon.

 

[Chris Cramer]

After filling my Argon tank, I spent a lot of time tig welding, or in some cases, tig brazing the brass with silicon bronze filler metal. It's difficult to apply the filler metal as the brass melts before the zink starts to boil. If the filler is built up along the joint it will bond to the edges once the brass gets hot enough. The tig torch does a much better job of heating the brass IMO because it is more hot, and even if the rest of the metal is still absorbing heat, a close arc will deliver enough heat as an extremely concentrated source.