Strength of 45% silver solder vs brazing

sagemouseJuly 12, 2005

I had a hook on my irrigation pipe break this morning. The hook is bronze. They are no longer available. Out of production 1949. My only choice is to braze it or to silver solder it. I have some 45% solder but am wondering which is going to be the strongest in tension. This pipe is 4" dia.aluminum pipe and has approx. 50 psi when operating.

Thanks in advance.....Jim

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spambdamn_rich

That hook doesn't look like anything all that special. If it were my pipe, I'd fabricate a new hook. This can be done with some flat stock brass plate, a saw, and a hand file. Or, if you have access to one, a milling machine. Yes the milling machine would be faster. Due to the curves on the hook a CNC equipped mill would be even better. But if you have some patience it could be done, as I say, with a saw and a few hand files.

The holes could be drilled with a hand held drill, or on a drill press, or on the mill.

I wouldn't trust either solder or braze to hold the broken part together.

    Bookmark   July 12, 2005 at 9:12PM
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ericwi

What spambdamn rich said. Looks like you will have to soak the pivot bolt with penetrating oil, for at least a day or two, before disassembly.

    Bookmark   July 13, 2005 at 9:07AM
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brickeyee

It is very difficult to braze aluminum. It can be done, but it is a real pain.
Brazing is joining with a filler metal with a melting point above 840F without melting the base material.
Many brazing rods have a high silver content, and a 45% silver material may actually be a brazing filler (it depends on the other metals present that may lower the melting point).

Either brass, steel flat stock, or even aluminum flat stock can be used to turn out a new piece by hand or machine.

    Bookmark   July 13, 2005 at 9:47PM
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gooseberry_guy

If you think it would be strong enough, it should be a simple job to get a piece of aluminum bar stock about the same size as the latch hook, and using the good piece for a pattern, trace it out on the stock and cut it to shape. Do an initial rough cut with a saw, then drill out the pin hole and the radius for the hook. finish up with a rough, and then a finer cut file, and you should be back in business. If need be, clamp your old one together to the rough cut piece to file it down to a close dimension. No reason why you couldn't do the same thing with a piece of steel.

Next time, don't beat on it when it doesn't latch. LOL.

GG

    Bookmark   July 13, 2005 at 10:34PM
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Hairy_old_man

Since this is an irrigation unit from 1949, and a lot like some piping my father-in-law uses, I would say it is a cast iron latch, not aluminum. Just braze it. I have repaired a dozen or so of my father-in-law's couplers by brazing the latches. Grind the edges of the break to get more surface area, then build up the brazing material. If its like my father-in-law's couplers, there is nothing to get in the road of the latch finger, and you can more than double the width of the latch with brazing material to add strength. It will hold.

    Bookmark   July 19, 2005 at 12:02AM
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brickeyee

"Grind the edges of the break to get more surface area, then build up the brazing material."

This makes a weaker joint, not a stronger joint.

    Bookmark   July 23, 2005 at 9:52AM
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alphonse

"Grind the edges of the break to get more surface area, then build up the brazing material."

That's standard procedure for brazing cast iron. It doesn't weaken the joint. As Hairy old man says, it increases the surface area of the braze. A grind up prior to brazing is de regueur regardless.

    Bookmark   August 6, 2009 at 2:15AM
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brickeyee

"That's standard procedure for brazing cast iron. It doesn't weaken the joint. As Hairy old man says, it increases the surface area of the braze. A grind up prior to brazing is de regueur regardless."

You can clean the surfaces for brazing without grinding them.
Brazing fill is rarely as strong as the base material, and a thin joint is stronger then a wad of weaker fill dumped into the joint.

Welding requires grinding back so the weld can be full thickness and built up in the joint.

    Bookmark   August 6, 2009 at 1:42PM
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alphonse

There's a difference between brazing by capillary action and brazing by puddling.
I've never done a wicking repair on cast iron, nor have I met any metal worker in 50 years who has. Puddling is the standard.
One could argue terminology to the point of distraction. By puddling I mean the filler is used as per welding technique vs. capillary as in sweating pipe.
"Brazing fill is rarely as strong as the base material..."
Not sure what is meant by "strong". Brazing alloys often approach or exceed the tensile strength of cast gray iron (not chilled)and are the reason brazing is used for the repair along with its lack of carbon pickup.

    Bookmark   August 7, 2009 at 6:33AM
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