solder and flux for brazing stainless?

What solder and flux should I use for brazing the handle back on a large (italian) stainless saucepan? I've had no success with the stuff used by plumbers for copper...

Clifford Heath wrote:
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Easyflow silver solder and Tenacity #5 flux should do the job.
Your post seems to imply that you've already used soft or lead solder (which is the stuff used by plumbers - plumbers don't usually do brazing). If so then you MUST remove every trace of it before attempting to use silver solder. The melting point of silver solder is much higher than that of lead solder - you will need to get the temperature up to red-hot, which is totally unobtainable with a soldering iron. If you know about silver soldering, then fine; if not then post again 'cos its very different to soft soldering.

lemel_man wrote:
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I'm guessing those are US brandnames, yes? Can you identify the ingredients so I can find a local (Australia) equivalent?
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Here, our copper gas pipes are brazed with a low-grade silver solder. Lead gets used on metal gutters and flashing though. I'm using the silver stuff, but I think it's only 4% or something.
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I know a little, learnt from my father, who used to spot-weld small S/S wires before brazing with thin high-silver solder (45%?). I've had success at that also, but have no more of the solder and haven't had success with the plumber's stuff even with his flux. I have a MAPP torch, so I have no shortage of heat :-).
Thanks for the help so far.

Clifford Heath wrote:
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No, I'm in UK and they are products produced by Johnson Matthey Materials Technology UK (JMM). Easy-Flo solder (previous spelling not correct) contains around 50% silver and has a melting point of around 680C. The standard flux for it is called Easy-Flo flux powder and, although I've found it works fine on all the SS I've used it on, the official flux to use for SS is Tenacity #5 (or #6) which is rather more active than Easy-Flo and thus can better cope with the permanent oxide layer of SS. It can also withstand higher temperatures, but this is of no consequence in this instance. Unfortunately it is also much more difficult to remove afterwards, which is the reason I tried Easy-Flo first. JMM is an international company so I would have thought their products would be available in OZ, but if not the local generic brands should be OK.
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This is not the right stuff - use the high-silver content solder your father used. The flux he used will not work with the low-silver content solder. A MAPP torch should be fine; SS is not a good heat conductor so the high temperature of MAPP should produce enough heat to locally melt the solder. Fire bricks to conserve the heat would not come amiss.
Devise a means of holding the handle in the correct position when applying the heat, ensure the area to be soldered is nice and clean and totally devoid of any previous attempts to solder it. You will be making the joint red-hot, so make sure you can't destroy non-metallic parts.
Mix some flux powder with water to make a thin paste, somewhat like cream, and apply to both surfaces to be soldered. Clamp the handle in place, cut off a small piece of the silver solder (about 2mm square) and place on the joint - this is not essential but its a very useful indicator as to when the joint is hot enough.
Apply the heat to the joint but not directly on the solder piece, and heat until the solder suddenly melts and runs into the joint. If you melt the solder before the joint reaches the correct temperature it will simply melt into a ball and stay there; when the joint is hot enough to melt the solder it will run into the joint. You can then apply some more solder from the stick as required - it will melt and run into the joint as well. It helps to dip the solder stick into the flux paste before doing this - some people just dip the hot end of the stick directly into the flux powder when some flux will melt and stick to it (the water is only useful for making the paste, it plays no part in the actual soldering process other than getting some flux powder to adhere to the joint before its hot enough to melt it). As soon as the joint contains enough solder (ie there is a nice fillet all round) remove the heat and allow to cool.
Be aware that all flux gradually looses its properties when heated. If you take too long to make the joint, the flux will fail and the solder won't run. If it takes more than a minute or so then stop and sort out where you are loosing heat, before starting again from scratch.
I hope this helps.

lemel_man wrote:
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Fantastic, thanks! Your description matches exactly what I've seen when it works, and is pretty similar to what happens (at lower heat) when soldering electronics, of which I've done quite a bit.
Must learn to weld someday... other than the tiny spot welds I can make with this dental welder :-).

wrote:
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TIG
Gunner
"If thy pride is sorely vexed when others disparage your offering, be as lamb's wool is to cold rain and the Gore-tex of Odin's raiment is to gullshit in the gale, for thy angst shall vex them not at all. Yea, they shall scorn thee all the more. Rejoice in sharing what you have to share without expectation of adoration, knowing that sharing your treasure does not diminish your treasure but enriches it."
- Onni 1:33

says...
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1) avoid using solders with lead, or brazes with cadmium.
Lead/tin soft solder is out, as is the EasyFlow 45 braze, which is about 15 percent Cad.
My personal suggestion would be to use a silver tin soft solder like Eutectic 151. That's 95 tin/5 silver and it has about three times the tensile strength of lead/tin solder.
Use a muritatic acid type liquid stainless flux like the Dunton's "nocorrode" type for stainless, it's a yellow liquid.
You won't need much heat, stainless has a very low thermal conductivity. A large solder gun could do the job probably, at most you would need a small air/acetlyene torch.
How was the handle first attached? Most of them are setup to use spot welding. If a spot weld let go, then just do a few more spot welds.
Jim

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Yup. Another 95Sn 5Ag solder is Harris Staybrite. These materials are food-safe, stick well to stainless.
Higher temp silversolders and TIG can be problematic on a saucepan because some of them have high locked-in stress from the mfg process and go nuts when heated to red heat or above. Been there done that.

Clifford Heath
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I wouldn't think that Staybrite would have enough strength for a pan handle . I've used it a lot, and I've used silver solder (brazing) more than I want to remember, and I use a hybrid of the two types that I alloy up myself. If it were my own pan and I was considering soldering I think I'd go with.... um... spot welding , yeah....
Or a real brazing solder because I personally wouldn't trust any low-melting, high-tin solder to hold on for very much long-term handling ('pan' intended) . I don't think of their solder joints as permanent. Part of this bias is probably snobbery from when I worked as a jeweler , part of it is from the stuff I do now that tears up soft-solder joints . Interesting to learn about brazing stainless though .
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