I never heard of Lincoln Stay-Silv, but if it is Harris Stay-Silv it is formulated for use with copper tubing and contains phosphorus which acts as a flux for copper but causes brittleness in steel. Probably not what you want :-)
you will find Johnson Matthey's publicity blurb for their brazes and silver solders. On p 11 you will find that that their 56% silver solders have a tensile strength of 410 n/mm^2, or 60,000 psi.
There is also a 44% alloy with a tensile strength of 545 N/mm^2, or
80,000 psi. It's a bit harder to use though.
Or here, where the UTS of a 56% silver solder is given as 71,000 psi:
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56% silver solder is strong stuff. UTS varies between about 50 ksi for cheap stuff to 70 ksi plus for the good stuff. Yield strengths of 60 ksi are not uncommon for premier brands.
Ans yes, joint strengths can be higher, up to maybe 120 ksi.
If "over here" is in the UK or EU I can perhaps put you onto a supply of "real" MAPP gas. Might need a different torch or an adapter, it has en412 (I think that's what it's called, used on butane torches and camping stuff) threads.
There is also the MAP_PRO type of gas (propylene, comes under several other names apart from MAP:PRO), but that is fairly easily available, most plumbing supply shops carry it.
(Technically MAPP is a tradename, but the people who own the name stopped making it about five years ago. People like Rothenburger and Benzomatic started selling propylene under names like MAP:PRO and MAP:PLUS instead, as a substitute.
However "real" generic MAPP gas was/is methylacetylene/propadiene mix stabilised with propane or more likely commercial propane/butane mix. while MAP:PRO and the like are pure-ish propylene.
MAPP is better, especially for welding - you can just about weld with oxy/MAPP, but forget about it with oxy/MAP:PRO.
However for air-gas torches, the difference is less important, and air/MAP:PRO is usefully hotter then air/propane. )
Harris Stay-Silv 56 does not contain added phosphorus. There are grades of Stay-Silv which do, but not the 56% grade, which is specified by Harris as being particularly good for nickel alloys and stainless (and no mention of copper pipes).
propane is hot enough, but on larger items can not supply heat fast enough. Erik has some good suggestions about using insulating fire brick to contain the heat. I have used more than one small propane torch to heat things faster.
Dan
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I did make a mental note about his suggestion. The welding shop doesn't have fire brick or glass wool, but I'm keeping my eyes open.
No I'm not. I was commenting on the strength of the solder itself independent of joint design. Joint design can indeed lead to an even stronger assembly than the tensile strength of the solder itself would suggest. Bad joint design can lead to a weaker assembly too. Eric
I was originally talking about Harris Saftey Silv. Not Stay Silv. I think the reason it is called Safety Silv is because it contains no cadmium. Anyway, it is good for steel. Eric
I don't think pink insulation, or any type of home fiberglass insulation will work. I think they use some kind of binder that you probably don't want to breathe when it outgasses from the heat. Where are you located? Anywhere near Seattle? Eric
I don't see any "Stay-Silv 56" listed in the Harris catalog and all the "Stay-Silv" I see listed does contain phosphorous. There is a "Safety-Silv 56" though.
or just google something like "silver 56% tensile" and look for the manufacturer's hits. It shouldn't take long to convince you that 70 ksi UTS, 60 ksi yield is fairly typical for a good 56% silver brazing alloy.
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