Posted by Valerie on October 06, 1997 at 18:51:13:

In Reply to: Welding yellow brass posted by Jerry Twaddell on September 29, 1997 at 14:58:28:

: work is done in yellow brass. TIG works great and MIG OK for the bronze and aluminum, but oxidizes the zinc in yellow brass giving a rough surface. I'm using an air cooled TIG with rod that I cast from the same metal. I would deeply appreciate suggestions.

As you figured, it is the zinc that is giving you the problem. The zinc turns to a metal fume at low temperatures and interferes with your shielding gas and also the cleanliness of your tungsten with the GTAW process. Some yellow brass compositions also have lead in them which also fumes at a low temperature.

Casting your own rods is a great way to achieve color match. With the lost wax process, a drinking straw can be used to make the shape of the rod. I found it best to bottom cast rods so that the pressure forced the molten metal the whole length of the tube.

As far as getting a good weld on the yellow brass - try not to get a large molten puddle too hot for too long. My AWS (American Welding Society) Handbook says that due to the high zinc content, it is very difficult to use this with the GTAW process. They suggest using one of these rods: RBCuZn-A (Naval Brass), RCuZn-B (low-fuming brass) or RCuZn-C (another low fuming brass). These are used with oxyfuel - done as braze welding. It would seem that the rod with the "C" on the end would be the best color match becuae there is no nickel in that particular rod.

Of course, you can try doing the braze welding with your own rods. I would check out the different powdered fluxes available at your welding supplier. Heat the end of rod a little and then dip it in a hole in top of the container. When the rod is hot, it will pick up just enough flux to make it work. The disadvantage with having your uncoated rods is that you can only go so far before stopping to dip the rod again.

Another tidbit from AWS: "Copper-zinc filler metals cannot be used as electrodes for arc welding because of the low melting temperature and high vapor pressure of zinc. The zinc vapor would boil from the molten weld pool, and the weld metal would be porous."

Anyway, try the braze weld with the oxyfuel. It will take a bit of time to get the metal to molten temp, but you will not have as much problem with the fuming.

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• Re: Welding yellow brass bruce paul fink 11/11/97 (0)

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