TIG "Cold" welding

[Toymaker]

After watching several videos on the subject of "cold welding", I decided to give it a go for myself and purchased a TIG machine with a "Cold" setting. For those that don't already know, cold welding produces far less heat in the parts being welded, BUT, the electric arc at the tungsten tip still carries enough current to melt the base metals, so the welded section is not actually "cold". The reason this process is termed "cold" is because the electric pulse that melts the metal is only a few milliseconds in duration resulting in far less heat being generated in the overall parts, thereby preventing parts from heat-warping.

I'm NOT a proficient welder, my aluminum TIG welds are truly ugly,...but the photo below shows my Cold weld of two pieces of 3mm 304 stainless using no filler wire, and with a 200 Amp setting. As a size reference, the two drilled holes are 3.3mm diameter, and the two 304 pieces are at nearly 90 degrees.

 

[timo_gross]

Interesting subject. The penetration is as far as I understand not so good, so this is not a replacement for structural welds. Not the new solution:
"Boiler repair for beginners "
How does it compare to welding "normal" without filler?

I could try a few minutes with a PUK Welder by Lampert. That machine works (I think) similar. It is suitable for watch making and other tiny things.

The most fun is the Welding microscope. You can look at the work in "Daylight" and for the split second when the arc strikes, the shutter goes dark.

 

[Toymaker]

I agree that cold welding is not a replacement for traditional TIG, but it might be better suited for the model world.

One of the reasons I started this thread on cold welding is because I believe this type of welding could be very useful in the model world, where metal thickness is typically quite thin, and the welds produced are also relatively small. The width of the weld in the photo I posted is only 2mm,...I don't know how deep the penetration is.

I think cold welding should also work well on most any structure using thin-wall tubing, where too much penetration results in burn-thru.

 

[ninefinger]

I'm not sure sure of calling it "cold" welding as that term has another meaning - the welding of 2 similar (identical?) metals that are perfectly clean to one another - usually with some light to heavy pressure, they self weld without added heat (therefore cold welding).
I think what you are doing is commonly called pulse welding. There is a high amperage for some short duration, followed by a low amperage, repeated at a frequency.

 

[Bentwings]

I'm not sure sure of calling it "cold" welding as that term has another meaning - the welding of 2 similar (identical?) metals that are perfectly clean to one another - usually with some light to heavy pressure, they self weld without added heat (therefore cold welding).
I think what you are doing is commonly called pulse welding. There is a high amperage for some short duration, followed by a low amperage, repeated at a frequency.

I agree that structural welding needs exploration I’d also question stainless welding eithoutback gas. It still has melted the base metal in non inert atmosphere. Thus subject to “ sugaring I would like to see lab micosopse. It is amazing for very thin stuff . Current modeling project would be perfect test. How much are the machines? I’ve decided one many hyears hours of small TIG welding long before the pulse weld option was available this looks like a natural for aluminum fuel tanks or even thin steel tanks fittings could be installed without wsrping or damaging threads even with my poor vision I could possibly still go do fine stuff.

 

[Toymaker]

I'm not sure sure of calling it "cold" welding as that term has another meaning - the welding of 2 similar (identical?) metals that are perfectly clean to one another - usually with some light to heavy pressure, they self weld without added heat (therefore cold welding).
I think what you are doing is commonly called pulse welding. There is a high amperage for some short duration, followed by a low amperage, repeated at a frequency.

I agree with you that the term "Cold Welding" is very miss-leading, but "cold" is what the industry is using; there's a button on the front of my new machine labeled "Cold".

Cold welding differs from pulse welding in that pulse welding current never drops to zero, while cold welding is somewhat similar to spot welding where current flow drops to zero after the single pulse is delivered.

 

[Vietti]

Toymaker, Very interesting! Can you supply more details on your machine??

 

[Toymaker]

I agree that structural welding needs exploration I’d also question stainless welding eithoutback gas. It still has melted the base metal in non inert atmosphere. Thus subject to “ sugaring I would like to see lab micosopse. It is amazing for very thin stuff . Current modeling project would be perfect test. How much are the machines? I’ve decided one many hyears hours of small TIG welding long before the pulse weld option was available this looks like a natural for aluminum fuel tanks or even thin steel tanks fittings could be installed without wsrping or damaging threads even with my poor vision I could possibly still go do fine stuff.

I purchased this small Andeli machine from AliExpress for a bit over $300. It's max current is 200 Amps which I'm finding out is good for 1mm thickness or less, but barely acceptable for 3mm and thicker stainless. I should be able to add filler to my existing welds to increase the thickness, but I have not yet tried this idea.

This whole cold welding technique is very new to me, so I did a destructive test on a couple of test pieces of 304 stainless. The below 3 photos show two pieces of 304 stainless, 3mm thick, cold welded using 200 amps, without filler. I then broke the two pieces apart by bending them back-and-forth a few times. Max depth of the weld is aprox 0.7mm while the average depth is about 0.4mm. There's no discoloration on the back side, which was not gas covered.

The machine I have allows the current pulse width, (the time current is flowing) to be adjusted from 0 to 200 milliseconds; I used 70 ms for this test. I will try a 200 ms setting to see how increasing the length of time of current flow effects penetration; it should be deeper, but a test will show how much deeper.

 

[Toymaker]

Even though this YouTube video is bit negative towards cold welding, he does a great job of explaining what it is. It's also pretty cool watching him weld two pieces of aluminum foil together, and two razor blades.



I am a little disappointed that he didn't mention how the lower heat produced by cold welding prevents heat warping the parts.

My opinion concerning cold welds lower penetration: seems to me the depth of penetration can easily be increased by increasing the amps in the pulse. Lightening can be considered as natures mega cold welder (or vaporizer), as the current in a lightening strike goes from zero, to peak current, and then back to zero in a single pulse lasting only a few milliseconds, which is exactly how cold welding is achieved. I've personally seen lightening blow a 2 inch diameter hole in a piece of 3/4" thick steel plate. That experience tells me that the depth of penetration of a single pulse of current is limited only by the amps delivered in that pulse.

The little 200 Amp welder I purchased should be adequate for most of the thin sheet metal I need to weld. If I ever need to weld 1/2" steel plate using cold welds, I'll need a much bigger machine