Metallurgical Help

[Hillbillysmith]

I have a metallurgical question that I would like answered and it is; I have heard that its possible to successfully weld "standard" copper with 318 stainless steel filler metal without it cracking. How is this so?? I mean, atomically, how can a ferrous metal be used to join a non-ferrous weld joint without lamelliar tearing, underbead/longitudnal/transverse cracks?

Now, on a second note, I know this is not an acceptable practice to do at any time. Im only asking for the pricipal of "food for thought" so please no comments such as; "if it needs to be welded do it right" etc.

Thanks,
-Hillbilly

[Timothy Miller]

I doubt it almost nothing sticks to copper. You might get it to stick if you use gobs of heat. If it were to work the strength would be very low.

[Nakedanvil - Grant Sarver]

And yet we can "braze" two pieces of steel together with bronze or copper without "lamelliar tearing, underbead/longitudnal/transverse cracks"?

I don't even think "lamelliar" is a word, is it?

Certainly you can have an "atomic" bond between the two, what matters which is the parent and which is the filler?

I remember watching Dimitri Gerakaris welding bronze and copper and steel together with mig and E70s wire.

[Dragons lair]

OK didn't work last time. trying again, Had a client buying copper sinks(3rd world) Holes bad or missing welds.
I used electrical wire. Stripped and tig welded or gas welded. Worked great.
Ken.

[Thomas Dean]

We used to weld 1/8" x 2" 316L SS strips to 1/8" (11ga.) copper sheets for our alcohol reactors on a regular basis. (we made 200proof ethel alcohol!) It took 20 sheets to line the inside of the reactor. copper and silver are the only things that would withstand the acid. The joint was made with the TIG process using copper wire and 'Bay State 11" flux, yes, flux. These joints were examined with dye penatrant to insure there were no cracks. So, yes you CAN weld copper to stainless. We no longer make the alcahol so we don't do this any more. But I did it for nearly 20 yrs before we shut down and sold that plant. The reactors were 7"thick, operated at 1250PSI & 500degrees F. the copper liner was to protect the walls of the reator from the acid. The silver was 99.9997% pure and we TIG welded it with silver wire! Butt welds on 1/32" silver is fun, there is no color in the weld puddle, like alum., and when you burn through it leaves a BIG hole! sorry about the long rant....just reminishing I guess....

[Timothy Miller]

Yes but he is talking about welding two sheets of copper together with stainless wire. I could see welding copper to stainless with copper wire or stainless to stainless with copper wire. You might even be able to weld stainless to copper with stainless wire. But copper to copper with stainless wire. the stainless has a higher melting temp than the copper. Copper is also not easy to weld even with a TIG welder and a good clean setup. You would be basically be fusing the copper to a solified weld bead of stainless. I guess its possible to sort of stick it together but the weld quality would me poor and why the hell would you want to. If you want the look of a silver weld bead use Cu/NI 70/30 welding wire. Its a lot closer metallurgically to the copper and has a closer melting point.

[Hillbillysmith]

Thank you to those who had constructive comments. I'm still looking into how this is possible but I'm leaning more towards the Cu/Ni 70/30 filler comment.

Yes, lamellar is a word. According to AWS (American Welding Society), lamellar tearing is the separation of a metal along its thickness due to the diffusion of hydrogen in the material caused by shrinkage from heat or weld. Typically the metal has alot of inclusions within the "crack".

Reference to back-up my information;
"Lamellar tearing. The existence of lamellar tearing is widely accepted as being the result of weld shrinkage stress acting through the thickness direction of steels with high inclusion contents (Ref. 16). However, prior to the introduction of clean steels in the 1970s, the diffusion of hydrogen from deposited weld metals was recognized as one of the factors influencing lamellar tearing (Ref. 17). Research carried out in 1972 (Ref. 18) reported that lamellar tearing was influenced by a combination of contracting stress, presence of nonmetallic inclusion, and hydrogen diffused from the weld metal. Hydrogen in this instance acts in a similar way to that reported for cracking associated with an H2S environment. It was concluded that inclusion content was the main factor and must be limited if lamellar tearing was to be controlled. Figure 10 shows an example of lamellar tearing.

Lamellar tearing has virtually been eliminated due to the production of clean steels with sulfur levels below 0.005%."

-Directly from the Welding Journal printed by The American Welding Society: http://www.aws.org/wj/jan04/still_feature.html

-Hillbilly

[Nakedanvil - Grant Sarver]

Just pulling your chain because you had spelled it lamelliar. Like I said I can remember Dimitri Gerakaris welding bronze and copper and steel together. Don't think it was all that great, but it seemed to hold everything together. Seems to answer "can it be done". Probably never certify on it though. But you did say "so please no comments such as; "if it needs to be welded do it right." So the answer is you can "paste" stuff together that way.

[Thomas Dean]

Yes but he is talking about welding two sheets of copper together with stainless wire. I could see welding copper to stainless with copper wire or stainless to stainless with copper wire. You might even be able to weld stainless to copper with stainless wire. But copper to copper with stainless wire. the stainless has a higher melting temp than the copper. Copper is also not easy to weld even with a TIG welder and a good clean setup. You would be basically be fusing the copper to a solified weld bead of stainless. I guess its possible to sort of stick it together but the weld quality would me poor and why the hell would you want to. If you want the look of a silver weld bead use Cu/NI 70/30 welding wire. Its a lot closer metallurgically to the copper and has a closer melting point.

My bad. I miss read his first sentence, and I agree to the CU/NI 70/30 wire. I have found if you use Helium as your shield gas (TIG process) you can use less amps to make the weld on copper, about 1/2 the amps. Also, it does not leave a black sooty look as it does on alum.

[monstermetal]

I didnt read all the posts but I can tell you that I have not only tig welded two sheets of copper together with Inconel FE 625 super-alloy but that I then hammer formed and planished the sheets... the Inconel is not crack prone like other stainless alloys and will move to a degree (during heavy forming the edges will crack away from the copper because it will not "move" as far)


What I cant tell you is why or how it works... But I dont question the result... if you dont have to worry about a silver streak running down the copper then it is WAY easier to weld than with copper filler.... and let me say again WAY eaiser... Like no big deal. The Inconel flows because even though it has a much higher melting point than the copper (like 3200F) it is not a heat sink like copper... so it will melt while the copper is still sucking up heat and make a nice puddle....

[Nakedanvil - Grant Sarver]

Interesting stuff Larry. Take that one off of my long list of things I don't know and add it to my much shorter list of things I do know. Funny, the first list seems to grow faster than the second.