Soldering steel

[PopcornSutton]

Years ago, stainless flashing was used quite a bit on buildings. They used irons and bar solder, usually 50/50. But in certain gun work, some parts are soldered on, this would be simple mild steel. A certain supplier sells a 5% silver/95%tin, says it flows at 475 degrees, and this is desirable so it doesn't change the temper of the steel. But I'll be damned if I can get it to work.

Been using some steel flat stock to try different fluxes, solder trying to do a tin coat and not having success. I took the flat 1/8" stock and milled the surface clean then hit it with brake cleaner before testing. I know to bring the heat up slow using a propane torch, not let the flame melt the solder but let the heat from the metal melt once up temp. but still no real success. I have the 5/95 silver/tin, 95/5 copper solder, 50/50, and some 60/40 flux core. Also typical copper flux/paste, nokorde brand and some liquid flux named Comet that the supplier of the 5/95 solder recommends. Any tips and/or tricks?

 

[dogdog]

What flux are you using ?

I used the black high temp flux to weld my stainless glass tabs that broke to stainless glass frame and 45% silver solder. Maybe try those black flux or white flux with your 5% silver ?

 

[Citation]

I've done some limited work soldering steel (and tungsten). In my case I used some very aggressive flux from McMaster. I don't recall the type but it was stuff that I always used with gloves and very good ventilation. We were making small things where the strength of the joint was sufficient so long as it was well wetted. That flux was like magic. We bought it hoping it was sufficient to get electrical solder (don't recall the type) to stick to Nitinol. It didn't do that well on Nitinol but once applied to SS or tungsten (we were using tungsten wire rope) it worked quite well.

 

[MBfreak]

I use the old fashioned " NOKORODE" brand. Bought a large tin in the 1960´s and it is still perfect.
Soldering standard steel parts, non galvanized, goes perfectly. Use 60/40 solder and a 1200 W soldering iron

Stainless-- impossible.

Ola

 

[no704]

I’ve soldered/brased SS to Titanium using special flux and filler (very expensive) using an induction heater.

 

[WildBill]

I use a tinning flux when soldering trim holes shut in car sheetmetal, sometimes with a circle plug of sheet metal if the hole is bigger than 1/8". It cleans, fluxes, and leaves a thin coating of tin which makes everything solder together. Or just acid core solder for small holes. I would think acid core might be appropriate for what OP is doing. Stainless is really hard to get anything to stick to though, we have some stainless pins at work we get a thin layer of gold plating on so they can be soldered into a circuit board.

 

[larry_g]

phosgene brake cleaner - Google Search

Read some of the above about the welding and brake cleaner. Not a safe combination.

lg
no neat sig line

 

[PopcornSutton]

I've been trying different things and had the best results using a solder I got to solder electronic connections. No other flux used, just cleaned the parts well, used brake cleaner to clean (dried off with air) tinned both parts. The tinning didn't look the best, but I clamped the pieces together and brought the temp up slowly. When right, that solder sucked right in as it should.

Never could find a way to make that 5/95 to stick to anything.