[GypsyJr]

I've read that its not possible to get a good enough join if you try to stick weld SS and Copper. Is that 100% correct?

I've got VERY little welding experience. I welded a trike frame together rather poorly but they did hold together. Lots of overkill on the welding and I think I've laid maybe one barely respectable bead ever that was only a little over an inch long.

I snagged a box of 620-308L electrodes last night because I have a couple projects dealing with stainless and these were heavily discount. I grabbed a couple scrap pieces of stainless and just welded an inch. Then I grabbed a piece of copper and welded it to a piece of stainless. That weld was basically a 1" tack/bead. The copper receded a bit so I backed the amps off a bit and continued testing it. The weld wasn't pretty but I was unable to rip it apart. I final ripped the copper off the stainless by over bending the copper over and over.

So I ask again, is 100% true that you can't get a strong enough join stick welding copper to stainless?

I should mention the the stainless was 304 1/16" thick and the copper was a cut open and flattened 3/4" copper pipe. The stainless looked fine afterwards as did the copper but the copper was a little red on the back side.

 

[StandarDyne]

Technically, no, you can't "weld" copper to steel, since true "welding" requires melting and mixing of the weld deposit and the parent metal, and copper and steel have far different melting and boiling points. So what you will have is technically a "braze" joint (or "braze-weld" joint if you pile up the copper the same way a weld joint has piled-up steel weld filler...some people restrict use of the word "brazing" for joints that suck up the filler through capillary action, like "sweated" solder joints do, except with "brazing" filler such as bronze or silver solder).

That said, some braze or "braze weld" joints approach or even exceed the strength of truly "welded" joints if done right. So, how much strength do you need?

ETA: I never heard of copper stick-welding electrodes. What's the deal with those? "620-308L" sounds to me like a SS electrode, not copper...

 

[danielplace]

https://www.amazon.com/Blue-Demon-ECUSN-C-Pack-Bronze/dp/B010HWUY9W

 

[Rondo]

Technically, no, you can't "weld" copper to steel, since true "welding" requires melting and mixing of the weld deposit and the parent metal, and copper and steel have far different melting and boiling points. So what you will have is technically a "braze" joint (or "braze-weld" joint if you pile up the copper the same way a weld joint has piled-up steel weld filler...some people restrict use of the word "brazing" for joints that suck up the filler through capillary action, like "sweated" solder joints do, except with "brazing" filler such as bronze or silver solder).

That said, some braze or "braze weld" joints approach or even exceed the strength of truly "welded" joints if done right. So, how much strength do you need?

ETA: I never heard of copper stick-welding electrodes. What's the deal with those? "620-308L" sounds to me like a SS electrode, not copper...

You're not going to get an actual weld with the copper based filler metals. Phos-Bronze, Silicon Bronze or Aluminum Bronze. Phos and SIB approach 55K tensile where ALB will be half that. There are torch, Tig and Mig processes but it's all really brazing. Done properly or something with silver will make a sound joint and will be surprisingly strong. Good luck.