I don't believe you're going to be successful with copper to steel. I used to sell welding products and we had an alloy that would join copper to stainless by brazing. Was used in the refridgeration industry. Never heard of a product for joining copper to steel. I have a spot welder and wouldn't even consider trying it.

 

Hey PAweldor...

Where in PA are you located? I'm out in Fulton County. Was just curious who you worked for when you were doing the Sales end of things?

Matt Grandi

 

harris probably makes a braze rod for it

never mind that....copper 1/100 inch thick? low heat solder of some sort

 

explain what you are doing, sheets? how big?
tubes? what?

 

Thanks for the help. More info.............I am forming a lap joint, steel can below and copper on top, the steel container is 1inch diam and 0.017" thick and the copper strip is 1/2" wide, 0.010" thick and 2 inches long. The reason why I am resistance welding is to keep the heat down (and I don't have anything fancy like a laser available to me) as the contents of the steel container are heat sensitive and can't go above 80C. So whilst the brazing suggestion would be spot on usually, the heat issue makes them a no go. I will look into soldering though - may find something that just locally heats the can and doesn't affect the contents.

 

If the copper is standard ETP (electrolytic tough pitch), you're gonna play heck trying to weld it. Cracks like the dickens. For welding, you need OFHC (oxygen free, high conductivity)

Try SilFos for a brazing alloy. 18% silver, 75% copper, balance phos. Good flow in a low temperature (1200) braze. Your LWD should also have some heat gel that you can apply around the joint to prevent heat spread away from the joint. Or, if you don't want to spring for the heat jell, you can use the time honored heat dam, commonly known as Crest toothpast. Spread a bead of that, and it will help stop the heat migration.

Regards, Kbnit

 

Sounds like a difficult project for sure. I have not tried copper to steel, or even copper to copper, but am familiar with resistance and upset welding, so the following are "educated" guesses. The high electrical and thermal conductivity of the copper compared to steel should make it very difficult to achieve enough localized resistance heating at the copper steel interface. If you are able to create enough heat to melt the copper and steel, the metallurgy may result in liquation cracking in the steel heat affected zone, so it may be best to try to keep the process solid state. It may help to form a projection dimple of some kind on the copper or the steel, in order to localize the current path and heating, and create some metal flow and deformation. Another idea may be to insert an intermediate layer of a braze alloy, maybe silicon bronze (Everdur), and try to make a resistance heated spot braze joint. To prevent overheating the electrode itself, it may help to make it out copper as well, or a high copper alloy like Elkonite TC-70, 70% copper/30% tungsten carbide. Maybe a shaped end on the electrode, with a point/bump, or multiple protrusions, would help maximize electrode to copper electrical contact thus reducing resistance heating at that interface, and also create upsetting/deformation and localized heating at the steel interface. Just some ideas. I'd try the braze alloy insert.

 

So, Poe,
what happened with your resistance weld?

 

What about glue/epoxy or a hot iron for solder?

 

Hi there.

I am still working on it (ie I still can't do it yet). I ordered some brazing material to butter the steel and copper and am waiting for a new set of electrodes to appear. I will keep you posted.

Poe

 

How about epoxy or some type of panel bonding adhesive?

 

Copper to steel is asking for the impossible in terms of welding. First, realize that nearly all resistance welding tooling is made from copper. It is a heat sink and is near impossible to resistance weld. Then, assuming you can melt it, copper to steel forms brittle compounds and will crack. Even if you make a weld you will risk breaking it in service.

It would be highly experimental, but you might stand a chance with resistance brazing. We use silicon bronze filler wire to TIG braze stainless to copper and have very good results. I found a supplier for silicon bronze sheet on the web once. If you put in a transistion layer of silicon bronze sheet you might stand a chance with resistance brazing.

 

thanks for the information.you all are gave a wonderful suggestion.:blob2: