Copper Backup Bars

[mlodzik]

Is there problems with utilizing copper backing bars when welding CP moment connections? I have a project where this is being proposed, the WPS and supporting PQR gave good results. However, somewhere I have heard or read that the SAC advisory and interium code changes discourages this ... maybe due to the possibility of cracking? I have not found any such reference in any of our documents. A review of AWS D1.1 shows that, at least from the perspective of AWS, that the use of copper is allowed.<br>
<br>
Is there anyway, outside of a chemical analysis, to tell-tale if there is any mixing of elements in the weld pool by using copper backups?

 

[Ing]

Outside of chemical analysis I would proposes a &quot;dye-chek&quot; to the root since mixed cooper there would origin cracks...Ing

 

[h2only]

Copper backing bars are perfectly acceptable on carbon and low alloy steel. I have also used these on 300 stainless steel (pipe long seams) and 5083 aluminum (ditto), as well as electroslag on carbon steel and CA6NM martensitic SS. I strongly recommend that you do your homework (i.e., trials that include mock-ups), and that you can trust your shop to give you the fit-up that you will need. Your welder will soon have no problems with it.
Copper pick-up is minimal, and most carbon and low alloy steels can easily tolerate a few more tenths of a percent anyway. When I was welding pipes, the copper backing bar would last for scores of welds. Just avoid having a GMAW arc directly on the copper.
Good luck
Gord

 

[h2only]

Copper backing bars are perfectly acceptable on carbon and low alloy steel. I have also used these on 300 stainless steel (pipe long seams) and 5083 aluminum (ditto), as well as electroslag on carbon steel and CA6NM martensitic SS. I strongly recommend that you do your homework (i.e., trials that include mock-ups), and that you can trust your shop to give you the fit-up that you will need. Your welder will soon have no problems with it.
Copper pick-up is minimal, and most carbon and low alloy steels can easily tolerate a few more tenths of a percent anyway. When I was welding pipes, the copper backing bar would last for scores of welds. Just try to avoid pointing a GMAW arc directly at the copper.
Good luck
Gord

 

Any tips on welding 6mm thick copper plate to same
using TIG

 

[Ron]

Use an appropriate brazing or soldering process.