T304 Stainless .065 wall tubing

[l u k e]

I need some advice on silver soldering this tubing, what solder and flux should I purchase for a strong joint?


Both parts are T304 soldered 90* to each other with a hole through the abutting parts. The ends are machined for a perfect fit. Its a paintball gun part, a ball feed tube to be exact.

I really want a clean joint, no buildup around the tube.

I've been TIG welding these but I want to try soldering for a cleaner product. I hope thats enough info.

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[Geof]

.....I really want a clean loint, no buildup around the tube......

I've been TIG welding these but I want to try soldering for a cleaner product. I hope thats enough info.

I have used Braze 450, a type of silver solder, just with the standard flux and have silver soldered stainless okay.

I must say, however, I think you are going in the wrong direction. It is very difficult to do a nice clean joint with silver solder on tube especially using a gas torch for heat. What happens is the tube gets hot enough around the joint that the silver solder flows out away from the joint and you are left with a film or lumps of silver solder on the tube adjacent to the joint.

[l u k e]

Humm, I wonder how the factory does it. (?) The part I take off to replace with the new design has a flawless joint. The only solder is at the connection point under the tube. I wonder if it was done in an oven.

I don't have any "factory" parts right now to take pictures of, might be a week or so before I get one in.

[Geof]

Humm, I wonder how the factory does it. (?) ....

Ah yes, the magical factory, how do they do these things?

I did not mention it but there is a way, an expensive way, to make really nice silver solder joints. Expensive in capital cost but with sufficient volume cheaper than any other way.

You can get the braze 450 I mentioned in the form of foil a few thousandths of an inch thick.

You machine your parts with this amount of clearance and you make a fixture that holds them accurately and firmly in the correct alignment.

Between the parts in the fixture you have a piece of the silver solder foil coated on each side with flux; actually this piece of foil can be slightly wider than the wall thickness of the tube.

Now you put the fixtured parts either in an oven and bring them up to temperature, or more likely you use an Induction heater.

Stainless is really good for induction heating because it has a high electrical resistance and low thermal conductivity. It is possble to have specially shaped pole pieces on the electromagnets to concentrate the heating almost exactly in the joint area.

That is how you get a flawless silver solder joint.

After investing maybe a $100k in fancy fixtures and Induction unit, possibly less but I wouldn't bank on it.

[l u k e]

Yea, that's what I thought.

[Geof]

How creative are you?

I am pretty sure you could do the fixturing so the induction heater is going to be the challenge.

Have you ever seen bearing heaters, induction heaters for warming bearings to slip on shafts, or surface hardening heaters; these are induction heaters that are used to bring steel up to hardening temperature.

You may find these on Ebay and they probably would have enough power; you are dealing with a small mass of metal.

You would have to figure out the induction coil side of things once you had the high frequency power supply but I do not think that would be too difficult.

[l u k e]

Fixtures are no problem, I'll have to check into the rest. The parts on average are about (.065 wall) 1.5" x 8-10", so I don't think it would take much to heat them up. Thanks.

[Geof]

Do a bunch of Googling.

With highly localized heating which should be feasible it will not take much power to heat them.