OT- Need a portable flameless silver soldering device

crossthread · Mar 12, 2014

I have a friend who works in the laboratory equipment field. I often machine up a doohickey for him to get something up and running. He also works on the ultra-low freezers and cryostats. The problem is that to replace a compressor, filter dryer, accumulator or something like that he has to silver solder the part in. A lot of the labs he works in will no longer allow an open flame so his acy/ox torch is out. He asked me if I had any ideas how he could heat up copper pipe to brazing temperature without a flame. I thought of the induction heaters and they are available with a wrap around design (so you can get it off the tubing after it is soldered) but cost an arm and a leg. Way out of his budget since he is a one man company. I looked up some homemade units but I was not impressed with ease of construction since they require tuned tank circuits and I don't have the equipment for that. I am thinking along the lines of a band saw welder. Basically a big honker step down transformer with some clamps (possibly with carbon pads) that could be placed on either side of the joint. It may be that copper is too good a conductor and will not work. Any ideas? Thanks.

Nick Mueller · Mar 12, 2014

Someone posted a link to induction heaters to loosen nuts/bolts (automotive repair field) just within the last two weeks. These were only at about $1000 if I remember correctly.

Here they are: Induction Innovations, Inc. Mini-Ductor II

No, I haven't tried these. But I wanted one for that purpose. I have been thinking about building my own too. Still in the back of my head ...

HTH,
Nick

Mcgyver · Mar 12, 2014

I've seen carbide tips being silver soldered on to saw blades by induction....irrc they were sort of U shaped and small. Might cause sticker shock though. Nick's is a good idea- use something thats built cheap enough for more of a mass market

you are going to have a hard time resistance welding or heating to ss temps. irrc copper conducts about 10x better than steel. look at how the points on a spot welder just sit there while the steel between them welds.

duckman · Mar 12, 2014

How about using a resistance heater, basically 2 contacts with usually carbon tips, touch either side of what you want to hear apply power, usually low volts and some amperage. This is used in brass model building so you don't heat some thing else and have it fall off. its very localized heat. I'm going to try it using an electric etcher that I have. Nick that Mini-Ductor would not work on copper or brass, no iron.

L Vanice · Mar 12, 2014

I have a jewelry making "soldering machine." It is a heavy box with a transformer in it. One output wire has an alligator clip or pair of pliers to attach to the metal part. The other output is a metal clamp that holds a carbon electrode. You put some flux at the joint along with a small piece of what jewelers call silver or gold "solder" which is what welders call brazing material. An arc forms when the desired joint in the metal work piece is touched to the carbon. It gets the metal red hot in a very localized area and the "solder" flows into the joint. These devices are used as an alternative to the Tescom "Little Torch" miniature oxy-acetylene rigs. They are meant for tiny jobs like resizing rings or repairing eyeglass frames where you want to keep the heat in a small area.

I expect the jewelry machine would be too small for any but the smallest (1/8"?) copper tubing. But a portable electric stick welder with a carbon electrode in the rod holder would probably work for big tubing. The risk I see is that the arc is so localized that you could melt a part of the fitting before the opposite side got hot enough to flow the brazing material. You would have to move the arc around.

Larry

Mcgyver · Mar 12, 2014

duckman said:
that Mini-Ductor would not work on copper or brass, no iron.

I don't know that tool, but induction heating irrc based on eddy currents. The heater uses magnetism but the work doesn't have to be magnetic only conductive. There's u tube videos of guys melting aluminum for example and it hangs in mid air as a molten ball until the power is turned off

Fulmen · Mar 12, 2014

Induction heats by two different mechanisms: Magnetic hysteresis (in magnetic materials) and eddy currents. As I understand it hysteresis is simpler, so for ferrous metals only it's the preferred method. Eddy currents require higher frequencies and higher currents.

Don Clement · Mar 12, 2014

Resistance soldering is flame-less. see: Resistance Soldering: The Solution

Don Clement

paulz · Mar 12, 2014

Nick Mueller said:
Someone posted a link to induction heaters to loosen nuts/bolts (automotive repair field) just within the last two weeks. These were only at about $1000 if I remember correctly.

Here they are: Induction Innovations, Inc. Mini-Ductor II

No, I haven't tried these. But I wanted one for that purpose. I have been thinking about building my own too. Still in the back of my head ...

HTH,
Nick

We have one at the shop. Works great for heating up bolts, I don't know how it would do for the Op's application though.

ETA, I tried it on some copper tubing today. It never got the tube hot enough to melt soft solder. Works great on steel though.

Mark Rand · Mar 12, 2014

Realistically, it would be better to ask the labs if they preferred an open flame or no joint. Silver soldering/brazing temperatures are just as dangerous as open flames. You can take ignorantly applied H&S too far... :typing:

Mcgyver · Mar 12, 2014

Fulmen said:
Induction heats by two different mechanisms: Magnetic hysteresis (in magnetic materials) and eddy currents. As I understand it hysteresis is simpler, so for ferrous metals only it's the preferred method. Eddy currents require higher frequencies and higher currents.

in that case, I may be wrong and that tool might only be good for magnetic materials

CalG · Mar 12, 2014

A buzz box welder and some "fabricated Tongs"

Don Clement said:
Resistance soldering is flame-less. see: Resistance Soldering: The Solution

Don Clement

Along with a pedal actuated contactor to control the on/ off .

Not sure if the inverter boxes would like being dumped to short, but in stick welding , that is inevitable!

So for a couple of hundred plus some " engine-uity" one could get close to good enough.

That is, IF the described units work as advertised ;-)

crossthread · Mar 12, 2014

Thanks everyone for the great information. The resistance soldering sounds promising and not very expensive. The only drawback I see from visiting their web site is that they seem to be for low heat applications (lead/tin) and I'm not sure it would bring the copper tubing up to silver soldering temps. The induction heaters would get me to the temps I need but they are pricey for the occasional job. I like your thinking Calg. I have some very large 110 to 12 volt transformers that came out of 300 amp industrial chargers. I may go out to the shop and clamp some kind of electrodes to a pipe and fire it up. I noticed in the resistance soldering FAQ that they use copper plated SS for the electrodes due to the low resistance of copper. I might try and clamp a few old carbon brushes to the pipe and hook the transformer to these with jumper cables. Just a proof of concept. Thanks again for the replies and ideas.

Mcgyver · Mar 12, 2014

Don Clement said:
Resistance soldering is flame-less. see: Resistance Soldering: The Solution

Don Clement

these look like soft soldering heaters, are there ones that get things to silver soldering temps?

Bill D · Mar 12, 2014

I have to wonder if any electric heating methods would induce stray currents and fry electronics in the lab. How about the strong magnetic fields damaging sensors etc. A torch does not affect stuff that is not near by, electricity can go a long way down a wire or piece of metal.
Bill D.

CalG · Mar 12, 2014

Just for consideration........

Low resistance conductors want LOW voltage at high amps to make heat.

I have a thermal vacuum evaporator in the lab that will evaporate any metal (even Wolfram!) But the transformers are set about 3V on 240V input. (Up to 10 V for thin wire filament heaters)

Currents can go as high as 500 amps to heat "boats".

I noticed the commercial resistance soldering unit offers a 10.1V output. To me, that would be quite a bit on the high side for getting heat into a piece of copper tubing. Might work for Stainless though. But they also include silver and hard solders in the text regarding possible processes.

Remember, Volts drive amps, but it's the amps that do ALL THE WORK! ;-)

If it were my doing, I would look to making 5 volts push a couple of hundred amps to do the job. But even then, 1000 watts doesn't sound like enough........

L Vanice · Mar 12, 2014

Mcgyver said:
these look like soft soldering heaters, are there ones that get things to silver soldering temps?

Yes, see post #5.

Larry

CalG · Mar 12, 2014

Bill D said:
I have to wonder if any electric heating methods would induce stray currents and fry electronics in the lab. How about the strong magnetic fields damaging sensors etc. A torch does not affect stuff that is not near by, electricity can go a long way down a wire or piece of metal.
Bill D.

Bill,

less than 10V in a resistance set up won't do much damage to any lab equipment as long as the amps don't sneak down some "path of least resistance" ;-)

Don Clement · Mar 12, 2014

CalG said:
That is, IF the described units work as advertised ;-)

Resistance soldering does works extremely well. Have used resistance soldering for waveguides, copper plumbing, and RF hardline with excellent results. RF hardline is particularly hard to solder without distorting the Teflon dielectric inside. Resistance soldering really makes soldering hardline easy because only the area to be soldered gets hot. BTW I used an RF S parameter network analyzer to check the quality of the hardline after resistance soldered. Yes you are right one could easily make a DIY resistance solderer. Nothing special there.

Don Clement

janvanruth · Mar 12, 2014

diy high frequenty induction? heater

Don Clement said:
Resistance soldering does works extremely well. Have used resistance soldering for waveguides, copper plumbing, and RF hardline with excellent results. RF hardline is particularly hard to solder without distorting the Teflon dielectric inside. Resistance soldering really makes soldering hardline easy because only the area to be soldered gets hot. BTW I used an RF S parameter network analyzer to check the quality of the hardline after resistance soldered. Yes you are right one could easily make a DIY resistance solderer. Nothing special there.

Don Clement

Just recently i saw a couple of youtubes where they made a high frequenty heater out of the electronics/transformator of a microwave.
Lookes quite simple and is cheap.

OT- Need a portable flameless silver soldering device

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