stainless steel fcaw on high vacuum chambers

By Joseph P. Kane (****)

Date 02-28-2008 04:55

I don't recommend anything but multi-pass GTAW for Torr level vacuum chambers.

By gonzo

Date 02-28-2008 05:19

thank you for the fast response. I build large vacuum chambers 8to 16 ft in Di.
for the vacuum industrie just trying to cut time on the welding process.I've heard
about flux core sst but I had my doubts about it .Worried about pin holes
and trapped flux...outgassing afterwards . once again thank you....gonzo

By Joseph P. Kane (****)

Date 02-28-2008 19:03

If you are making CJP welds, a GTA three pass root (on the vacuum side) followed by FCAW will be very good, provided you do not burn through anywhere. I used to repair coatings chambers, after some hack tried to repair them with MIG or Stick. They couldn't even draw it down into 10-2 Torr. You could pour acetone on the outside and watch the meter drop into the molecular range! I would remove all the repairs and attempt to get a CJP weld with multi-pass GTA weld. The Secret is cleanliness and always MULTI-PASS stringer beads. Always use new SS brushes to clean between each pass. Always use new cotton rags with lots of acetone to wipe down. When I got done the machine would always go down to 10-6 or 10-7 Torr.

By gonzo

Date 02-29-2008 04:47

thank you for info .most of the chambers whe weld only get welded on vacuum side .
Thats why there trying to get me to use flux .butt I will make note of your advice
for when we do CJP welds thanks again for info .I'm just ring to see if its possible to
find a FCAW that can be clean and lay smooth

By 803056

Date 02-29-2008 05:10

I take it that those pore holes you allude to are a possible source of the water we see bleeding out of the metal when we preheat with a torch Joe?

Best regards - Al ;p

By Joseph P. Kane (****)

Date 03-01-2008 20:13

Al

Those pores--Friends of your's??

By 803056

Date 03-01-2008 21:49

Yes, I have a close repore with them. Oops, my mistake; "I have a close rapport with them." :)

Al

By SteveinAZ Date 03-01-2008 19:45

I'd agree on the multipass GTAW for the root. If you are just trying to fill the joint after your GTAW root passes, and FCAW is the way you wish to go, then I would recommend ESAB (the old Alloy Rod guys) "Shield Bright" products. They seem to have a wider parameter range (less susceptable to voltage) than some of the other brands we have used. Toes wet out very well, and gives a nice, smooth bead with easy to remove slag. They make this in numerous alloys. Also, no matter who's product you choose, make sure it is FRESH, and best if hermetically sealed to keep out any atmospheric moisture...you need to keep it dry...a spool may run $500 and if exposed to excessive humidity, you may as well flush the $500 down the drain. Steve

By gonzo

Date 03-01-2008 20:54

thanks for the info steve I'll check ESAB and see what they have .....once again thankx