Joining stainless tube to steel pipe

I'm making a steel-post-and-stainless-cable railing for my deck. The posts are standard 1-1/2 inch pipe. The cable will be attached with swaged fittings at the end and corner posts, but will simply pass through holes in the intermediate posts. I want to keep water from getting inside the posts where the cable passes through, so I plan to drill through the posts, and insert a short stainless tube across the dimeter of the pipe. I've experimented with both brazing and soft soldering the stainless tube in, and both appear to work, but the soldering is much easier. Also, the heat needed for brazing tends to melt the end of the stainless tube (5/16 OD, 1/4 ID), so the soldered job looks better, too. The posts will be painted.

So here are the questions:

  1. Will the soft soldered joint take normal outdoor Nebraska thermal cycles (-20 F to 105 F) without cracking over time and allowing rust to get a foothold? There is no real mechanical stress to the joint other than from temperature changes.

  1. Are there soft solders that are stronger than those for plumbing?

  2. Should I consider something else, like hard solder (I think this takes a temp as high as brass brazing, doesn't it?) or epoxy?
Reply to
ed_h
Loading thread data ...

Silver solder, which requires a temperature much lower than brazing. It is much stronger than soft solder, and easier to apply. Check with your local welding supply house, and be certain to purchase the proper flux. There's a black one on the market that is reputed to be superior to the ordinary borax product, a white paste that is applied to the joint before soldering. It is much easier to overheat than the black one, and is highly recommended for joining dissimilar metals.

Harold

Reply to
Harold and Susan Vordos

It's the black one you should buy, not the white one. Sorry for the poor terminology.

Harold

Reply to
Harold and Susan Vordos

  1. Consider drain holes, 'cause no mater what, you will get mositure.
Reply to
Brian Lawson

A tin-silver solder works great on stainless, provides good color match, is considerably stronger than plumbing solder and works at low temperature -- about 430F. Harris Staybrite is one such material. Flux can be Harris Staykleen or ordinary tinner's fluid.

It will handle thermal cycles. It's used in refrigeration and in food & beverage applications. Joints must fit well; it is quite fluid and doesn't "bridge" gaps well. Staybrite 8 is a similar material with higher silver content, will bridge gaps better because it has a plastic range. It's harder to find, though.

A stronger material would be a silverbrazing material. It may not be a good color match because most silversolders contain some copper, and you'll get some discoloration of the stainless from heat. It runs at about 1200 to 1400F. It'd be stronger than you need here; I'd go with the Staybrite.

Reply to
Don Foreman

Look at this. Four reasoned, polite, and helpful responses in less than 24 hours. Maybe there is something to this Internet thing after all.

Reply to
ed_h

Thanks for the lead. I researched Stay Brite. It is a little hard to find, but is available mail order, anywhere from $50-$90 for a one pound spool. However, McMaster carries a silver/tin solder with just about exactly the same composition (from the MSDS sheets) for about $35. If anything, it has slightly higher silver content. It doesn't list a brand, but I wouldn't be surprised to see that it is Stay Brite when I get it. They also have a flux that appears to be very close to Harris Stay Clean (again from the MSDS sheets). Thanks for the advice.

Reply to
ed_h

That's the stuff. $35/lb is about right; that's what Staybrite goes for at my local welding store.

Reply to
Don Foreman

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.