Let's talk silver solder for a moment

[SoCal-Doug]

So my buddy wants to upgrade his propane system to electric. Great. I've helped him build up the panel and most other tasks are complete. Final step is mounting the elements.

Being the engineer type (electrical and automation), I had drawn up some 2" TC solder "spuds" for my brew system in Solidworks, and sent them over to my CNC shop. When I requested 2 more for his rig, I discover I am out of Stay Brite 8 silver solder.

I start doing some research because my local AirGas store has the regular stay brite... Here's what I find on Harris's website

StayBrite:
Ag 3.4% to 3.8%
Sn Remainder
Solidus 430F
Liquidus 430F
Shear strength 10,600 PSI

Stay Brite #8:
Ag 5.5% to 6.0%
Sn Remainder
Solidus 430F
Liquidus 535F
Shear strength 10,600 PSI

I don't claim to be a metallurgist, but other than a higher liquification point on the "8", I don't see an advantage to using #8 with only up to a 2% higher silver content. They both have the same shear strength. If anything in a brew system gets up to 430F, I would say we have much bigger problems than a spud falling off.

What am I missing and why does all the videos and blogs say the 8 is preferred?

 

[FourSwitch]

I know as a refrigeration tech most of the silver solder I use has a certain phosphorus content. I would suspect if you find the silver solder data sheet you may find #8 lends itself to food processing better

However if they are the same then I'm stumped! Please post back and let me know!

 

[The_Bishop]

Found this on the info sheet about StayBrite #8:

Stay Brite #8 is a lead free solder engineered to provide a strong, ductile connection on copper, brass, steel, and stainless steel. The silver color is also a good color match to stainless steel. Stay Brite #8 differs from Stay Brite as its higher silver content provides a melting range vs. Stay Brite’s single temperature melting point. The melting range makes it suitable for soldering connections with a wider clearance. Stay Brite #8’s low temperature characteristic promotes capillary flow and less base metal distortion and oxidation. Stay Brite #8 is often selected for residential HVAC tube connections as an alternative to brazing.

http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Lead-Free-Solders/stay-brite-8.aspx

I'd say the heat range melting point along with the greater capillary flow and oxidation characteristics make it preferred.

 

[BlkWater_brewer]

So my buddy wants to upgrade his propane system to electric. Great. I've helped him build up the panel and most other tasks are complete. Final step is mounting the elements.

Being the engineer type (electrical and automation), I had drawn up some 2" TC solder "spuds" for my brew system in Solidworks, and sent them over to my CNC shop. When I requested 2 more for his rig, I discover I am out of Stay Brite 8 silver solder........

In today's plumbing solder, lead is no longer used. The only thing you need to solder stainless steel is a good stainless flux. You can use a special solder if you want but MAP gas, SS flux and regular solder is all you need. Ooops, sorry I was going to add; unless you're an engineer type. Sorry

 

[beermanpete]

The StayBrite is a eutectic alloy so it will not have any "waxy" phase. It will go from solid to liquid instantly. If the parts fit-up is good and you do not need/want a large fillet this is ok. The #8 will provide a waxy phase that allows you to work the solder and build up a fillet in a poorly fitted joint.

 

[SoCal-Doug]

Aha... So there is some difference in flow and build up. That makes a difference!

I'll jump on Amazon and grab a roll of #8 then. It sounds more "forgiving". I can get the stay-clean flux locally no problem, but nobody stocks the 8 for some reason.

Thanks everyone!