Brazing Brass

[SteveM]

One thing. If you silver solder, DO NOT use a steel backer. Not unless you want it to become part of the hinge. If you gas braze or TIG, it most likely won't be a problem, though.

That was my first thought about that, but I suspect that you could use a steel backing plate with spacers to hold the part straight while you are brazing. Maybe long spacers that would let you get to both sides of the work.

Steve

[ctwo]

If I put the pieces together, it looks like the bracket took about a 30° bow and the upper flange part was starting to buckle. I think the cause is the mounting fasteners came loose from the door and only the end fastener remained.

I filed and whacked it with a chisel. It seems a little harder than aluminum.

[ctwo]

So the guy at welding supply suggested low fuming bronze, 3/32". He thought it was brass.

I'll practice on some misc. scrap.

[DavidF]

Yep, thats looking more like brass to me.. and your probably 100% correct on the cause of failure... Can you tig??

[ctwo]

I have no tig welder, but I recently watched a video of a guy putting tungsten in his mig gun and reversing polarity, and tiggin it... I'd still need argon.

The bracket is a little flexible as I was able to pry it back a little straighter and get it ready for brazing.

I sprinkled the crack with boric acid after heating the part as much as a propane torch could, then I went to the OA torch near the edge. A piece of rod melted off and laid in the crack, so I moved the flame around each side trying to heat the base metal. I saw the rod start to liquefy and form small droplets on each side. I was expecting any second it was going to melt into the workpiece.

It melted into a ball and almost blew off the piece, so I focused the torch on one spot of the base metal, determined to melt that spot. It would not melt. I think my torch is too wimpy and braze barely started to stick. The torch has about 1/4" tip with probably 1/16" port. I have another torch with the oxygen lever, and I suspect it has something like 6 ports. I would try that next time.

But I ran out of Oxygen. The acetylene is at 300 psi. I was running about 5psi gas and 40psi was fixed on the oxygen until I open the torch and the pressure would drop about half. Also, when the part started getting real hot, it was sizzling and poping like bacon, but I could see anything happening. Maybe a bunch of flux melted down under the crack?

Anyway, I'll probably clean up the part again and give it back, tell them to find a welder.

[GlennW]

I. I have another torch with the oxygen lever, and I suspect it has something like 6 ports. I would try that next time.

That's a cutting torch.

[ctwo]

The lever, or the whole package? I'm sure you can still weld, or at least braze with it, right? Otherwise, maybe I just did not have enough O2.

Also, if the bracket is brass, isn't bronze low fuming rod not the right stuff? Should I be using low temp brass brazing rod?

[warmstrong1955]

By your picture, it appears that you are melting the filler rod onto the work-piece. In a word....WRONG!
You are supposed to heat up the work-piece, and when it's hot enough, dip the filler rod onto it, where it will melt to the work-piece. Not the other way around. The filler rod does not really go directly into the flame. If you do the opposite, you will get what you got. The process is quite similar to soldering, more than welding. Don't melt the part....but melt the filler rod into it.
If you can't get the part hot enough to melt the filler rod onto it, you may be using too small of a tip. Brass/bronze/copper will require a larger tip, as the part soaks up the heat and spreads quicker than steel & iron.
Not sure what effect acid has....but I have never used any. Get it clean, wire brush it, and braze, and clean as you go. You can see the crud on the surface as you heat, assuming you are wearing the right glasses.
Not sure what flux you used, but you may want to check that too.
Cast parts often have many impurities, including sand. When you heat them, the impurities will rise to the top, so many require brushing when you get started, and as you go. Use a stainless wire brush. If you don't have & keep things clean, the filler rod will not follow the heat well, and melt to it....like your pic as well.
Check your flame. An oxidizing flame will mess things up, and give you that popping.
You may be using too small of a tip. You need to get the part hot enough to melt the filler rod. If you don't and linger there too long, the part will oxidize, and you are again doomed.
You're way to high on the oxygen pressure. Should be closer to 5 PSI. Too much oxygen is bad.
Acetylene at 5 PSI is OK....3 would be better.

Don't use the cutting tip for brazing. Doable, but not easy, not for a rookie, and again, too much oxygen in the parts.
I've done it, but I've done a lot of brazing & welding. Never as controllable as a brazing/welding tip.

Bill

[warmstrong1955]

Pulled this off the interweb just now.
Some reference for ya.

victor_tip_charts.pdf

(276.33 KiB) Downloaded 136 times

Bill

[Glenn Brooks]

Another way to look at the casting is to compare the age of the building with development history of Aluminum bronze. A good part of the SF historical area got built hetween 1850 and 1907. Aluminium Bronze is a new age metal, and wasn’t widely available for commercial applications until the 1930’s and latter. There are color differences between the two bronzes also. This part seems golden bronze, hence color wise, probably actually “gunmetal”, aka Plain Bronze, rather than Aluminium bronze. plain bronze is copper with 12% tin added. Aluminium Bronze has Aluminium added. So the formulation makes a difference regarding what type of rod to use.

[John Evans]

Actually you don't braze brass you are welding it as the filler metal melts at the same temperature as the base metal,just like steel rod for steel.
using a silver based filler would have worked much better . Brass alloys are hot short .one moment solid the next a puddle on the floor.BTDTGTTS !!

[ctwo]

It would not be before 1955, I think.

When I turned the O2 reg, the pressure did not move until I opened the torch. It did not relieve pressure like my air compressor, and the adjuster actually came out and fell on the ground with full pressure still reading. I open the O2 on the torch and the pressure dropped some. Can't go lower that I can tell... I thought the reg was broke.

Yeah, it was like trying to bronze sand. I didn't want to mention that because I thought it might just be the boric acid.

My tanks are probably older than this part. They do not even have threads for a cap. I think they are unfillable and illegal to transport.

I digress...