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I have an old microwave/convection oven that came with 2 metal circular trays for cooking on (in convection mode), a tall one and a shorter one that fits underneath it. However, a long time ago, one of the legs of the taller one snapped off, leaving me with just the shorter one. This is OK usually, except when I want to cook 2 things at once (that don't fit on one tray). I can get a replacement for >$40, but I'm just not interested in spending that much.

I recently had the idea to solder a new leg to the tray. Presumably I'd need some high-temperature solder. Considering it may come in contact with food, it'll have to be lead-free too (maybe flux is also a problem?). I'll have a soldering iron that can supposedly reach 896ºF, and the oven has a max temperature of 450ºF. I need solder that is both solid and stable up to at least ~500ºF (It can't just not melt, it has to be able to hold its shape!). I honestly couldn't find anything that meets my criteria; some contain lead, most melt too low, and some just too high. Does anyone know if such a thing even exists?

Thank you!

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  • Is brazing a possibility? This sounds too hot for a solid solder joint. – JPhi1618 Feb 4 '20 at 19:13
  • @JPhi1618, not really. I don't have the tools or skills necessary to braze anything. That's why I'm hoping I can use a high-temperature solder that can withstand the oven's temperature. – Rafael Feb 4 '20 at 19:18
  • Why not just bend&wrap the new leg around the old frame? It's easy to do that & end up with a stable platform. – Carl Witthoft Feb 4 '20 at 19:26
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    @JPhi1618 silver solder is not brazing - the filler metals are different... – Solar Mike Feb 4 '20 at 21:07
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    can't you just keep a wood block or wire "sculpture" under it to replace the leg? Or maybe bolt on a piece of pipe? If you insist on the orig leg, look into spot welding, using something like super-capacitors or car batteries: this leaves behind no contaminates and can easily melt (tiny amounts of) steel. Might also ask a metal shop if they could tack it on for you; might even do it for free if you ask nice enough... – dandavis Feb 4 '20 at 21:36
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There is some serious fake information on the "Net" regarding "silver solder". ; starting with Oatey ( Home Depot) who flat out lies about what they call "silver solder". The Halstead net site is good. AWS ( American Welding Society) identifies silver solders as having 45 % to about 60 % silver with copper, zinc, cadmium in various amounts. Melting ranges of 1125 F to 1250 F and must be heated above those temperatures to flow. These alloys have AWS designations of B Ag-1 up to B Ag-7. I would not consider a product to actually be silver solder unless it had an AWS designation. ( I am using a 1971 ASM reference and AWS may have added designations or even changed their system ).( Irony , I gave my 1987 ASM reference to a local teacher a few days ago because I had not used it in years).

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  • I would use real silver solder but if the metal is cast it may fall apart at the higher heat, the non lead solder I use has a melting point of 625 f but I don’t know what all is in that (I still use 60/40 Rosen core for most electrical applications) . – Ed Beal Feb 4 '20 at 21:25
  • @blacksmith37, I don't have the capabilities to melt anything above the max of my soldering iron (~900ºF). Any AWS certified silver solder won't work for me. – Rafael Feb 4 '20 at 21:31
  • @EdBeal, what solder do you use? It sounds perfect! – Rafael Feb 4 '20 at 21:31
  • Worthington lead free, the spool says 500f but my solder station says 625f , , I turned it down to 500, just now and it would not melt, trued at 525, 550 no melt started melting at 575 but not hot enough to flow and tin the iron, at 600 it will tin the iron, I was able to connect 2 leads together at 600 but they are not bright, 625 works for electrical connections and stays bright, not sure what in in it the label states 97/3 Rosen core, I was fixing some boards so it only took a minute to test. – Ed Beal Feb 4 '20 at 21:49
  • @EdBeal, thanks for the info. But are you sure that your soldering station's temperature calibration is accurate? If the manufacturer says it melts at 500ºF, and your station says minimum 575ºF, then maybe it's just not calibrated. – Rafael Feb 4 '20 at 22:18
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Not gonna work.

The problem is you are trying to use a metal fusing technique, using a thermoplastic material (i.e. whose properties remain basically the same, and can be re-melted at will). And using the tools you already have on hand.

The crux of the problem is that the tools you already have are incapable of making the material significantly hotter than the service you wish to put it into. Any solder your iron could melt, will also be melted by the oven.

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  • Why not? The oven reaches 450ºF, and the iron reaches 900ºF. That means the iron can melt many solders that the oven cannot! Although practically, putting in a 451º melting point solder is not a good idea, even with a 100º buffer, there's still a 350º range! I would call that significantly hotter. – Rafael Feb 4 '20 at 21:45
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    @Rafael Because you're depending too much on assumptions. You assume your 900F soldering iron can effectively transfer 900F into material of that size and conductivity. You assume a material's melting point only has to be somewhat higher than X to perform well at X temp. Not good assumptions. – Harper - Reinstate Monica Feb 4 '20 at 21:55
  • What I'd ideally like is a solder with a melting point of ~800ºF. The soldering iron should be able to melt that. Even if we assume that the oven (which's highest setting is 450ºF) will occasionally reach 500ºF, there's a 300º range between the oven and the solder's melting point! The material properties of the solder would be fine at those temperatures, especially considering that many average solders only melt at +300º from room temperature. – Rafael Feb 4 '20 at 22:14

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