[pcook911]

I have been welding for a few years though not very regularly or with SS.

My wife is a brewer and one of the guys in her brew club asked me to weld a 1/2" NPT coupler (308 SS) in the side of a keg to use as a boil pot. I am doing sanitary welds on a keg using an argon back purge. The keg wall is ~16 gage (.06") and the thickness of the coupler is about 1/8". The coupler just barely sticks through the keg wall or basically flush with the inside. I am having trouble getting the weld metal to flow between the coupler and the wall of the keg without serious distortion. The welds look pretty good from the outside but I would like the weld to have no gaps or crevices on the inside that could trap wort, precursor to beer, and lead to bacteria growth. All of my welding in the past has been on sheet metal of the same thickness so I am new to welding something so heavy to the thin walls of the keg. I am practicing by welding couplers in the discarded lid of the keg. Anyone have any suggestions on setting or techniques that could help me out? Or maybe I just need more practice on this type of weld.

Equipment
Using Miller Dynasty 200DX with 1/16" 2% thoriated tungsten with a #8 gas lens and a 12cfs argon back purge with a tight fit between the coupler and the keg wall, .045 308L filler

So far I've tried tried

80 amp - which seemed too hot, lots of warping of the keg wall
60 amp - which seemed too hot, lots of warping of the keg wall
80 amp, 39 pps, 60% pulse on time, 30% on background - metal didn't flow down to fill the gap between the coupler and wall of the keg

TIA,
Paul

[Rick_H]

Since the keg wall was press formed it may distort a little, if you can clamp any copper, brass or aluminum around that area to try to act as a heat sink it will help.

I would think 60-75amps would be enough... I would normally suggest trying to keep the heat towards the coupler, but since your trying to do a full pen weld it really needs to be right at the weld seam. If you try pulsing try 100-120pps 75% peak, 45% background and 85 amps


FWIW, when I weld full pen on 316L .065" wall I am at 45-48amps, 10cfh backpurge, 15cfh flow with a 1/16" tung and #8 GL and cup.

Can you get any pics? Are you getting through at all to the backside? How long are you letting it purge, and how large is the vent?

[Otto Nobedder]

My suggestion would be to bore the hole in the keg to the I.D. of the coupler, and bevel the coupler about 45* to (or near) a knife-edge, stand and tack the coupler 3/32" off the keg, and weld it open-root for full penetration. The bevel to knife edge eliminates the "dissimilar thickness" issue, and gives you a keyhole you can see.

Steve S

[Rick_H]

My suggestion would be to bore the hole in the keg to the I.D. of the coupler, and bevel the coupler about 45* to (or near) a knife-edge, stand and tack the coupler 3/32" off the keg, and weld it open-root for full penetration. The bevel to knife edge eliminates the "dissimilar thickness" issue, and gives you a keyhole you can see.

Steve S

I like that suggestion.... You could also weld the I'd sand and polish out the weld till it is seamless and weld a nice bead/fillet or lap on the outside. I just welded a bung in a hopper awhile back in that method, passed all swab tests and requirements for my company.

[pcook911]

Thanks for the replies.

Steve,

I like the idea of a smaller hole and a bevel on the coupler but the hole was already in the keg. I'm guessing he bought a kit with the pre-drilled keg and a coupler that just needed the weld.

Rick,

I'll give those settings a shot. Here are three links to photos of the first attempts. I have enough problems welding on a relatively flat surface. I don't think I could weld the coupler from the inside at all! Though that would solve my problem of lack of penetration!

Thanks,

Paul

1st attempt - 80 amps
Lots of distortrion
https://plus.google.com/u/0/photos/your ... 8889770763

2nd attempt - 60 amps
Distortion, lack of penetration
https://plus.google.com/u/0/photos/your ... 8889770763

3rd attempt - 80 amps, 39 pps, 60% pulse on time, 30% background
No distortion, lack of penetration
https://plus.google.com/u/0/photos/your ... 8889770763

[Rick_H]

How did it work out?