Stainless soldering issue

[DesignerGuy16]

I've got a 3/8 diameter 304 SS rod with holes drilled to accept some cold drawn 17-7 spring wire.

We were welding the end of the spring wire to the rod, but the strength wasn't there. We specified some Harris Stay-Brite 8 silver solder and Stay-Clean liquid soldering flux.

Problem is the solder isn't even adhering to the 304 SS rod, yet alone flowing between the hole and wire.

My guys are using a propane torch with some temp crayons to get the temperature right. I've watched them and can say they aren't grossly overheating the rod.

The technical guys I've talked to are at a loss. The temperature is right (solder flows at 535 deg F, and we're heating to around 550-600). The clearance is ~.003-.005, which should be perfect according to Lincoln Electric.

My next course of action is trying some Eutectic 1800 for a higher silver content, but I'm uncomfortable with having to heat to 1200 deg F as I already have some warping in the rod.

Any thoughts? Is it just an issue with the difference in base materials maybe? Is there something we're missing in the prep maybe?

James Spisich
Design Engineer, CSWP

 

[arunmrao]

Perhaps the clue is available in one of the published articles below.

http://www.bssa.org.uk/topics.php?article=150

http://www.azom.com/details.asp?ArticleID=1178#_Recommended_Procedure_for

 

[tomwalz]

I'll go with oxide layer.

You can create oxides by heating stainless steel including some Chromium oxides which can be really hard to remove. Generally HF is recommended to remove them.

Try a brand new piece of stainless. Degrease with spray on oven cleaner. (Any strng caustic with a wetting agent and a rinsing agent will work. Oven cleaner is just readily avaialble.) Abrade the joint area with emery paper or similar.

Solder immediately using plenty of flux.

Stainless is going to want to create an oxide layer. Flux is an oxygen interceptor.

Immediately after abrading stick it in some flux.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[DesignerGuy16]

I think what complicates this is there's about 40 wires that have to be soldered in using a fixture. Maybe I'll look at them changing the fixture so they can do one at a time, or at very least a few at a time instead of trying to do them all.

I'll try that with some chemicals to strip the oxide layer and have them install into the fixture and apply flux quickly after.

James Spisich
Design Engineer, CSWP