Brazing Stainless steel superheater return

Any tips please on brazing the above? Return comprises 2 x 5/16" dia. thin wall stainless tubes into a stainless return block. What braze rod and flux should I use?

Should any one out there be interested, the answer is weld it,which has now been done.

Have a word with CupAlloys they will steer you in the correct path

Bob

Hello John

First consideration is to use an austenitic stainless steel to prevent any corrosion of the joint in a damp or wet environment. These are the 300 series.

If you are not sure, use a magnet. Austenitic stainless is non-magnetic

Then use a flux suitable for capable of removing chromium oxide eg HT5

Nothing to choose between the silver solders other than meltng temperature. You pays your money and makes your choice.

regards

keith

PS If your stainless is magnetic you must use a silver solder that contains nickel to prevent that corrosion. Use 449 alloy but it is not as easy to use as say 455 or 438. Easier to use 300 series stainless - readily available from your usual source of tube.

Since the Superheater tube and return block are often situated in the top of the firebox, should the joint be welded and not siver-soldered?

Will the Silver-Solder Melt?

Dave

I would have thought that while there is reasonable steam flow it would be OK but as soon as the engine is stopped you would have a problem.

Russell

Russell,

True under low speed/load ... bu if the loco is working very hard, the fire is going to get even hotter .. white hot even ...

So I think silver soldering is a no-no. (The reason Stainless steel is used is to eliminate the risk of copper melting.

If the Super-heater does not enter the fire-box then you might just be ok .... not a risk I would take though.

Dave

I've always used Silverflo24 for the return bends on stainless superheaters and haven't had a problem yet. I make sure the return block is at the back of the firebox above the firehole where the temperatures are less extreme but the elements can and do glow red at times.

John

Thankyou everybody for your responses. I think its established therefore that silver soldering the unit is perfectly OK. But its working life in the firebox at sometimes very high temperatures, makes it too much of a risk for me to take. So the unit has been welded to give peace of mind...........but I had to cough up some cash to get it done, much against my principles!!!

John H