Brazing 90/10 copper nickle

Date 07-23-2015 22:53

I'm working on a small pipe job that calls for brazing 90/10 copper nickel. The pipe is 3/4" to 1 1/2" dia.,sch. 10, and we are using the brazing rings that go in the fittings. The fuel gas is acetylene. I really don't have too much experience with both copper nickel and brazing but I've been trying to learn a thing or two about them. I have tried a few joints and it seems like I have to get the fitting extremely hot, just about red hot. After that the fitting is pretty much a dark grey...basically it all looks like crap. Something just tells me that I'm doing it wrong. I've looked around and I cant seem to find much information on the subject. Can anyone shed some light and give me some pointers?

By TimGary (****)

Date 07-24-2015 12:36

90/10 is pretty easy to braze. Using fittings with consumable rings is a good idea. You just have to remeber that cleanliness is next to Godliness, use plenty of clean flux, and the filler will draw toward the heat.
That thickness will take plenty of heat, but don't over do it. Try to heat it evenly so that both fitting and pipe reach the melting temp of the filler at the same time. Use a neutral to carbeurizing flame to heat the surrounding areas outside of the joint, don't direct the flame tip into the joint.
Once you see the filler flow on the pipe all around the joint, back off. If you overheat it, the flux will cook out and you'll wind up with leaks. Red hot is way too hot.
The heat discoloration and cooked flux will make the final joint look like crap. If you need it clean, wire brush it afterward.

Tim

By 803056

Date 07-25-2015 03:55

I would add that the entire joint must be heated to the appropriate temperature before introducing the filler metal. Also, add the filler metal to one location until it will take no more, work the filler around the joint slowly filling the joint as you go.

If you make a fast fillet around the joint without filling the joint as you go, the fillet will prevent capillary action from doing it's thing. The joint will not fill, instead, you will only have a fillet that provides little strength.

Al

By TimGary (****)

Date 07-27-2015 12:54

Hi Ya Al!

You're right of course, for a braze joint in which filler is added as you go.
The OP's question was for a joint with "brazing rings", which is a preformed ring of filler that is inserted into a groove machined in the id of the fitting and installed prior to fit up. In this way, the filler is melted when the base metal reaches the melting temp and capillary attraction draws the filler out of the coupling.

Tim

By 803056

Date 07-27-2015 13:26

Right you are Tim, however, there are times when the ring is insufficient to fill the joint completely and it has to be supplemented with some face fed filler metal.

With the rings it is important to heat the joint as quickly and as uniformly as possible. On larger parts it can be an advantage to use two heating torches to heat the joint in a reasonable time frame.

Best regards - Al