excess penetration on 1/4" 304L butt weld

Date 04-22-2011 19:13 Edited 04-22-2011 19:18

Hello mightymoe, don't know that I know of any "tricks" right off-hand, however, if you can include additional information such as process, parameters, thickness, mechanized, hand-welded etc. I am sure that myself or others might have information that could be of help. So, if you can try to provide just a bit more info. After rereading the post I believe some things don't add up here. 1/4" 304 tube is "really" small to be calling out such a large gap and if hand-welded would certainly be a buggar, I believe butted and welded with an orbital tube welder would be the way to address this particular joint. I could certainly be mis-understanding what you are describing, my appologies if that is the case. Corrections requested. Best regards, Allan

EDIT: rereading again, are you saying 1/4" thick tube? What diameter? Purged? Filler wire diameter? Joint configuration: bevel angle, knife-edge, land/thickness, Etc.? Sorry just a little confused.

By mightymoe (**)

Date 04-22-2011 22:20

Good Questions Allan.
1/4" tube .088min wall. GTAW manual/hand welding. 1/16", 3/32", 1/8" 308L filler wire available. Purged with argon. Groove angle of about 60 degrees with a knife edge.
Arc Machine orbital welders are on the jobsite, not being used yet.(I think customer has not bought off on proceedure yet)
100% bore scoped. On that small of tube if the bore scope won't fit thru than it's no good.

By aevald

Date 04-22-2011 22:58

OUCH mightymoe, that doesn't even sound like any fun. Yet having heard more of the particulars I would almost think that if you are hand welding these you would be better served by getting away from the knife-edge 60 degree bevel configuration and going with either a square butt with no prep or just a slight prep. and then experimenting with amperage and travel speed. You might also consider using .040 filler rod or getting some .045 solid wire and using that for filler.
Additionally, I do believe that the ARC Machines orbital would definitely be the way to go. Much better chance of repeatability and consistency. I have seen these machines applied on other diameters of thinwall stainless tubing with some really nice and consistent results. They were using a square machined end prep. and fusing the joints. By precisely controlling progression and heat the finished joints actually "shrunk" and provided just a bit of internal reinforcement as well as external reinforcement. I will be interested to hear suggestions from others. Good luck and best regards, Allan

By swsweld (****)

Date 04-23-2011 00:28

Depending on the tube service I would think that the customer would require machine welding instead of manual welds. Socket fittings probably not allowed or they would already be doing that.

I'm no help with manual welding tips on SS that small. Seems that there is no room for error with those tolerances so repeatability, heat sync, degree of difficulty and many other variables would probably result in a high reject rate.

My only experience with SS that diameter was square butt, no gap, feeler gages to check for gaps, tungsten pre ground with exact same geometry, and with Diametrics Inc. not manual. All variables were so critical to produce repeatability. This was for Thimble Tube extensions at Turkey Point Nuclear Plant and the tubes carried a wire to detect neutron radiation while reactor is running (I think..was 15-20 years ago). We developed our own parameters in the shop and had 4 program changes to the program for welding a 1/4" tube.
Any sloppiness on the fit-up or execution of the set-up, tung. stick out, 0.005 gap, argon cfm too high, resulted in reject. We were able to insert a go-no-go gage in the production welds in addition to the bore scope. Too much penetration was not an option.

I think that AMI, Diametrics and probably all other brands have programs that you purchase with their machine to match the type and size of pipe/tubes that you are installing so you don't have to reinvent the wheel.

My hats off to you or any one that can make these welds.

By mightymoe (**)

Date 04-23-2011 01:23

I can't wait till the orbital is being used.
Some welds will probably have to be done manually.( welding 1/4"tube to an o-let).

By bozaktwo1 (***)

Date 04-24-2011 00:55 Edited 04-25-2011 16:53

In light of the information already posted, the only advice I have is to keep your root to a minimum, cap your tube and use a metered release for the purge, allowing the pressure in the tube to prevent excess backside build-up. This is tricky, as you'll have to continually adjust the pressure as the root is closed up. Leave it going the same as when you start, and you'll blow out. For my 2 cents, I'm with these guys: machine welds all the way.

EDIT: ROOT GAP TO A MINIMUM.