How to braze or weld silicon bronze???

[Steve Shelby]

I'm Making a sculpture, a bird, like this one: http://www.metalartistforum.com/forum/sh...p?tid=4596, except much larger and, for the first time, I'm using 1/16" silicon bronze (alloy 655). I have never made anything out of bronze before. I'm wondering what to do when I get to joining the seam. My expertise is in silver-soldering, and I have very little experience with brazing, using that brass-colored brazing rod from the welding supply store, and when I have, I was not very happy with the results. As a matter of fact, my supply of brazing rod was purchased over 30 years ago, and I still have most of it left. The bronze is a light copper color, so I'm thinking silver solder might show up quite a bit. The brazing rod I have is yellow, like brass, so I think that wouldn't be any better than silver solder. Everything I've read about silicon bronze says it can be easily welded by any method. The problem is, it's a butt joint, which is the most difficult, IMO, and with my lack of experience, I can see me melting a hole in it and ending up with ten hours of work being scrapped. What are my options? Is there brazing rod available that would match the color of the bronze? BTW, I have to use a torch; I don't have MIG or TIG or any of that fancy stuff. Any guidance would be appreciated.

[Tony Mertens]

Talk to your local welding supply house. I know you can get silicone bronze TIG rods so they should have them for the torch. I'm not too familiar with O/A welding - they may even be the same rod for either process.

[PTsideshow]

How close is it to copper in color, As Harris 0 is a good match to copper sheet. Tractor supply sells Harris 0 gas rod, in smaller packages.You may not like buying 3 to 5 pounds. A lot of the gas rod can be used for TIG or the other way around.
Looking in the Crown Alloys rod and wire book
They have a Crown Silicon Bronze rod that can be used for TIG and Torch
The instructions for torch are dip heated rod into Tiger Flux3 and proceed to finish flowing alloy into joint until it is completed.

The rod melts at 1866'F

Royal Tiger Flux #3 is General purpose brazing flux Temp range 1550'F to 2000'F


Looking in the Airgas catalog They have Randor Silicon Bronze 36" lengths,1/16" 3/32" in one pound packages. Used for joining copper alloys.
I'm sure that Praxair has the same type.

[Vermontsmith]

Like Tony said, since you know the alloy of the base material look around for a matching filler rod of the same alloy. Ask your local welding supply place to order some in if needed. "Tig" filler rod can be used if you get it hot and dip it in a can of brazing flux prior to A/O torch brazing.

-Judson

[johnwalkeasy]

I've use a lot of silicon bronze welding rods over the last 30 years. I'd never used them with a tourch. So I can,t answer to that issue. I,ve always use a Carbon arc rod. Useing S.P. on a DC welder. You can weld steel and stainless steel. And with a tig. welder you can weld copper. I,ll try to post a picture of something I,ve made useing this process. A procress I call Steel & Bronze.

---

Biker 69, Steel & Bronze, 32" long. 2005.

[Steve Shelby]

Thanks, all for your answers. It looks like everything you're suggesting is for WELDING rather than BRAZING. Is welding my only choice other than silver-soldering (silver brazing)?

[PTsideshow]

No you can use the TIG rod with an oxyacetylene torch and brazing flux as In my first post and in Judsons post after mine. You will have to prefect your technique on some test pieces and for color match tests.
The brazing flux in my post is the same as most other good quality fluxes.
I just typed the instructions from the filler rod catalog.Tech sheet downloads for the silicon bronze alloy filler rods scroll down the page to copper based alloys 6th one down is the filler rod.
The Harris 0 filler rod is a closer match to copper color.

[Steve Shelby]

Glen, thanks again.
I looked at the alloy for silicon bronze at the link you provided. its melting point is 1866F, which is about the same as the silicon bronze I'm using for my sculpture, which is 1780-1880F. The distinction between welding and brazing, as I understand it, is with welding, you are actually melting the metal you are joining, and adding filler as necessary, and with brazing you are not melting the metal you are joining, but melting only the brazing alloy so that it flows into the joint and bonds the two pieces of metal together. So what you are talking about is welding, not brazing. I think I would want to get a lot of practice at it before trying it on a sculpture I have several hours invested in.

[PTsideshow]

Check orchid message archive in the last 3 or 4 weeks there were a number of messages on somebody finding a brass match color soft solder. Don't remember, but there were a number of messages and answers

[warrent]

Steve,
This is what I do, I cut some very thin strips of the alloy I am using. Then you are actually welding with the strips because you melt the strips into the base metal. Get some regular brazing flux. Heat the strip and then dip in the powder. The flux is only there to help get a puddle flowing. Once you get the puddle flowing the strip will melt into the base metal and you will have a little weld bead. Yes I do this with the O/A torch. Practice to get your heats correctly. A smaller tip that is cranked up works the best because you will need a lot of heat but you want to concentrate as much as possible.
You can also try regular low fuming bronze brazing rod, but you again have to melt into the base metal. I find though that you still get a little yellow.

Here is somthing that I am working on that is a bronze, not sure of the alloy so this is how I approached.