Welding of copper to Stainless steel

[prc]

I have an application .Hot rolled copper plates of 3-5 mm thick are to be fixed to a base plate of stainless steel (316 or 304 ).This is done for magnetic shielding of base plate .Normally this is done by drilling 10 mm dia holes in copper plate and welding at the hole (plug welding )all around copper to steel and then fill hole till 2mm bead project out.Welding holes are provided at a pitch of 150 *150 mm.Purpose of welding is to mechanically fix the copper plate to steel and it should not come off in service due to vibrations etc.Service is under oil at 100 C .Can any one recommend the correct grade/make of electrode to be used ,Dc current value and any special procedure for welding ?or there any better method of fastening available ?

 

[unclesyd]

I would go with a silicon bronze material as the nickel alloys may cause problems if this is for magnetic shielding.

 

[metengr]

Agree with unclesyd regarding brazing because welding of copper to stainless is very difficult, at best even with nickel-base fillers. Have you considered using small, self tapping austenitic stainless screws or if the stainless plate is thin using stainless steel rivets to secure the copper sheet to the stainless plate?

 

[prc]

Let me explain the application .The copper sheet is fitted over the stainless steel plate(10-12 mm thick ) to protect the same from magnetic flux .The flux will induce a current in copper sheet which in turn will expell the intruding flux.That is regarding application .Of course use of stainless steel rivet is an option if welding is impossible.Then rivet has to be welded first and then put copper sheet and peen it .Any spec or precaution in the selection of rivet ?

 

[metengr]

Considering your additional information, riveting is the way to go not plug welding or spot braze-welding for materials of this thickness. For a 10-12mm stainless steel plate, a 304 or 316ss rivet could easily be installed and would not need to be welded. You would need to drill holes thru the copper sheet and the stainless plate to accommodate a stainless steel rivet for fastening.

 

[prc]

Thank you Metengr for your suggestion.Can you give some details of quality of stainless steel rivet /normal sizes used .Rivet is to be screwed to the base ?

 

[metengr]

prc;
I would suggest contacting several reputable fastener companies, and obtain their input regarding rivet size and style. For your application, I was envisioning a rather simple tubular rivet design that can be easily installed. You will have to drill holes thru the stainless base plate to accommodate a tubular rivet.