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Up Topic Welding Industry / Technical Discussions / thin gauge stainless
- - By makeithot (***) Date 09-22-2007 23:13
18g to be exact . Would it be normal practice to butt weld this material, I had to weld some in the field for a lap pool trough made by some one else they had aready done some of it but did not complete the out of position work. As most of the work had been done there was not any length left to do lap joints. I did manage to get 3 of 4 joints done the last because there was no room to add rod I bent a return with a pair of vise grips clamped it and welded without filler.  
Parent - - By Tommyjoking (****) Date 09-23-2007 02:45
Richard,

Well ..."Normal practice"??    I won't touch that description LOL!!!!

Sounds like you had a good dose of the SS draw/pucker curse

Umm .032 filler and tig as your already doing I sounds like.  Yes butt welds are normal but the thinner you go with SS the exponentially harder they are to make come out good.  A little bit of gap to allow for draw (much as you can stand but no more then 3/32), lots of clamps.  Lots of tacks and then tack in between over and over till they are at least 3/4" apart. If possible welding it against a copper backing strip or against thick steel blocks with a separation/groove of about .125 right under the joint and backing gas shot into that gap/groove.  On a full pen weld backing gas is a must unless there is a tight fit keeping air off the backside of that joint.  Its hard to get good results on sheet SS without being able to jig it up.  The best way to avoid pucker and drawing is to have reinforcement clamped around the material on both sides as close as possible to the joint. In a field weld thats not always possible...you said it was out of position so you probably did not have any option of putting heavy weights along each side of the joint.....think 1-2 inch thick flatbar strips.   Another thing that helps keep long joints under better control with SS is backstepping your welds....same tacking routine but skip weld every 4" or so and then come back and weld the empty areas.   There is nothing wrong with a fusion weld as long as its sufficient strength wise and your not getting it too hot...too hot and it will centerline crack everytime on ss.    Like I said before sheet ss is hard to work with it takes much more effort to keep it lined up and flat.  It sounds to me like you did what you had to do to get it done.  Kinda a short reply to what is a lengthy subject.....I work with this material everyday down to .018 so if you want to ask me about any techniques in particular I would be more then happy to pass on my experiences with it if there is something in particular  you are curious about. 

Best Regards
Tommy
Parent - - By makeithot (***) Date 09-23-2007 17:55
Thanks Tommy, I did pretty much every thing you discribed except for the number of tacks and I did use a copper backing strip which seemed to work well to absorb the heat and control the distortion. I did not how ever leave a gap but fit every thing tight. was a person to leave a gap how do you set up the gas as there is nothing to contain it on the back side of the weld.
Parent - By Tommyjoking (****) Date 09-24-2007 04:10
the gap does not matter in regards to gas  (use tape where you are not welding)...you just need enough flow to ensure no air is getting in there.   Pieces of copper with a longitudinal hole drilled thru and lots of vent holes drilled laterally are very usefull.......however just running a line at one end with it enclosed well to ensure that gas is running down the joint can be suffecient.   Argon is heavier then air so if its like on a 1g joint it has nowhere to go but up therefore the oxygen will be kept at bay.  
Up Topic Welding Industry / Technical Discussions / thin gauge stainless

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