eutectic solder

[farmbif]

ive got a couple big oversize rolls of this stuff like 5lb rolls, supposedly its for soldering stainless steel like commercial kitchen stuff.
I saw something today that said it was a form of babbit and it doesn't turn grey like regular lead tin solder.
its very old stuff and I have no idea
doers anyone know about eutectic solder?

[Winger Ed.]

You struck Gold on that stuff.

It's 63% Tin and 37% Lead. Some variations of it has other goodies in it and up to 2% Silver.
It has good flow, higher strength and is used in some high end applications for electronics.

Stainless Steel is usually TIG welded with Stainless Steel rods.

[1hole]

Eutectic refers to the lowest temperature a given soft metal alloy will melt.

By itself, pure lead melts at one temp, tin, antimony, silver, zinc, etc., melt at other temps. But, mixed together, the lowest melting temp (the eutectic point) of any alloy will be a bit lower than the melting temp of any one of the metals in the mix. The modest eutectic heat difference of some precise solder alloys can be important in some kinds of electrical soldering.

I don't KNOW but I doubt the eutectic point of any lead alloy will make much difference in casting bullets.

[JonB_in_Glencoe]

Specifically, "the words eutectic solder describe a solder alloy that melts and freezes at one single temperature."

https://fctsolder.com/eutectic-solder/

[BattleRife]

Does it have a label or any markings on it?

Knowing that it is a eutectic composition doesn't mean much if we don't know what alloy system it is. If it's an old solder and the weight feels right I suppose we can assume it is lead-tin, in which case the eutectic is 62SN-38Pb. But it could be a trinary eutectic (three metals) or another mix, such as lead-bismuth.

[justindad]

Solder for SS on McMaster-Carr is 45% tin, 54% lead, and 1% silver… makes me think silver is required to solder stainless steel.

[Echo]

Eutectic solder (60-40, actually 63-37), when it melts, goes directly to a liquid state - from solid to liquid, with no plastic state in between. ALL electrical work should include eutectic solder. As an ex-missile man, I remember a test where an SM-62 Snark missile crashed on launch. Investigation shed to cause to be a 'Cold' solder joint. That is where the soldering took place with a non-eutectic solder, and the solderer did NOT get the joint hot enough to actually melt the solder! They just got it soft enough to fill the space, and left it at that. And cars bodies (way back!) used to have welding joints smoothed over with 30-70 solder. It could be heated up to the plastic state, prior to the liquidus state, and used like mud to cover up and smooth out the surface.

[gwpercle]

Specifically, "the words eutectic solder describe a solder alloy that melts and freezes at one single temperature."

https://fctsolder.com/eutectic-solder/

JonB ... I need to see some explaining ...
How can something ...melt and freeze ... at one single temperature .
And I'm not a graduate of MIT ... just an old Louisiana Swamp Rat ... keep keep this esplanation simple .
Gary

[popper]

That is the meaning of eutectic. generally for a binary lead/tin alloy, at the proper ratio liquid goes to solid phase. Above/below the alloy forms various combinations of liquid and solid until it all solidifies. Real 'cold' solder joints are due to the metals not getting hot enough to combine with the melted solder.
296902

[JonB_in_Glencoe]

JonB ... I need to see some explaining ...
How can something ...melt and freeze ... at one single temperature .
And I'm not a graduate of MIT ... just an old Louisiana Swamp Rat ... keep keep this esplanation simple .
Gary
The melting point and freezing point describe the same transition of matter. In this case from liquid to solid (freezing) or equivalently, from solid to liquid (melting). When the melting point equals the freezing point. This "point" is the temperature at which the solid and liquid forms of the molecule, are in equilibrium.

FYI, the meaning of equilibrium is, a state in which opposing forces or influences are balanced.

[Martin Luber]

Linotype is also a Eutectic, thats why you don't want to let it solidify in your pot. It goes from solid to liquid in one shot, usually with a squirt to the heavens.

[BattleRife]

JonB ... I need to see some explaining ...
How can something ...melt and freeze ... at one single temperature .
And I'm not a graduate of MIT ... just an old Louisiana Swamp Rat ... keep keep this esplanation simple .
Gary

Many substances melt and solidify at one temperature, the most common example being water.

Water at 0°C (32°F) can be entirely solid, entirely liquid, or a mix of the two.

If you have a bucket of water as a liquid, taking energy out of the water can lower the temperature to the freezing point. Then, if a little more energy leaves the bucket, some of the liquid turns to ice. As more energy leaves the bucket, more of the water turns from liquid to solid, but the temperature doesn't change. It is always 0C/32F.

Eventually all of the water will freeze, then if more energy is removed from the bucket, the temperature of the ice starts to drop again.

This is why ice water is such an important reference point. If you have a stable mix of solid ice and liquid water, the temperature must be 0C/32F, it is the only temperature at which that mixed state can exist. Many pure metals are used for similar temperature references at higher temps.

Non-eutectic alloys have what are called mushy stages, where they are a mix of solid and liquid over a range of temperatures.

[bangerjim]

All 316/416SST joining I have ever done is with a TIG welder. I guess they sell SN/Pb solders for the purpose, but the strength sure is not there!

Sort of like those Aluminum soldering rods the sell at flea markets.............what a joke! They always demo them by soldering a pop can together! The stuff is worthless for real life structural jointing.

I would treat those rolls of solder you have as what they REALLY are - - 45%Sn + Pb. Good for adding that 2% Sn to your melt - if needed.

I sure would not trust mud-dauber hand soldering to the SST joints I have done.

And do not get lost in the weeds about "eutectic metals". Nothing special at all.

banger