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Up Topic Welding Industry / Technical Discussions / Stainless 316 Handrail
- - By JettIndFab Date 04-05-2007 14:06
We are Fabricating a SS316 handrail using 1-1/2" sch 40 pipe with a #4 finish.
we seem to be having a major problem with distortion, that we only slightly had with the aluminum and steel railing that we have done (this is the first time doing SS railing).  We have a plywood "teepee" shaped bench setup for guys to weld on both sides of the table.  we are using angle screwed to the table to act as our jig, then clamping the pipe to the angle.  there are approx. 2 clamps per post, intermediate rail, and top rail between posts.  we are seeing distortion of the intermediate rail and top rail between the posts, as well as a curve to the entire piece (10'-20' long).  we are all scratching our heads and trying different things such as, doubling the amount of clamps, lowering amperage to lower heat input, skipping around the welds instead of a left to right sequence, with no success.  Our next trial is to weld one side with a lower amperage then the other side, and/or weld both sides with one amperage then flip it again and run over the welds again to try and draw it back. ANY suggestions anybody may have is greatly appreciated.

We are Tig welding the joints using 98 amps (90 & 98 for the above trial), 1/16" Tungsten-2% ceriated, and 1/16" Radnor 308L Filler metal, DC negative current, 100% Argon flowing at 15cubicft/hr, and laying down an 1/8" weld joint.  Using welders: Miller Syncrowave 250, and Lincoln Squarewave 255.

PLEASE HELP:confused:   -THANK YOU-
Parent - - By aevald (*****) Date 04-05-2007 15:01
Hello JettIndFab, is there a reason that you are using the 308L filler instead of 316L? Not that it may actually make a lot of difference in a handrail fabrication application, but I am curious. Also the choice of 1/16" filler may not be the best as it will possibly require a prolonged dwell time in the puddle and cause more overall heat input which will be tied directly to the amount of distortion that you are seeing in your rails. You might try using a 3/32" filler, laying it in the seam of the joint and trying to use just enough heat to get it to fuse at both edges as you move the torch along the seam. If you have problems with the puddle drawing away from the rod without pushing it back into the puddle try a similar approach with an 1/8" filler. As you are finding out, stainless will crawl around somewhat unmercifully. You may have to get creative with some heat sinks or possibly come up with some creative fixtures that will introduce a back-bend into the weld-joint area after the rail has been tacked together, but before the welding takes place. Hope this might help a little bit. There will likely be others to give you some really good suggestions as well. Keep us posted on your progress. Good luck and regards, aevald
Parent - By js55 (*****) Date 04-05-2007 15:17
Low thermal conductivity, high thermal expansion. The beast of SS. Aevald said it. Low heat and some fixturing is all you can do. Those are the basics. I'm not sure there are any secrets with this. Its a result of inherent material properties.
Parent - - By G.S.Crisi (****) Date 04-05-2007 15:28
Stainless steel handrails? Good heavens! What a luxury! Stainless steel handrails are unthinkable in underdeveloped countries like mine.  
That's but one difference between first and third world countries ..................
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By aevald (*****) Date 04-05-2007 18:38
Hello Giovanni, from your perspective I can see where you might view a SS handrail as a luxury, yet, in this case it's application might have to do with an issue of cleanliness and lack of a bacterial harboring ability. Some industries require this type of rail. I don't know if that is the case here, but it is a possibility. I hope this explanation might make a bit of sense. On the other hand, it could be just as you said, the difference of someone having way too much money to spend on handrail. Regards, Allan
Parent - - By G.S.Crisi (****) Date 04-05-2007 19:26
Allan,
I understand perfectly your point. Here in Brazil, when cleanliness and prevention of bacterial growth are needed, as in certain food and pharmaceutical industries, we use aluminum handrails.
Giovanni S. Crisi 
Parent - By aevald (*****) Date 04-05-2007 22:20
Thank you for your comment Giovanni, it is interesting that you folks use aluminum, is that the case due to a cost and availability issue? Although, I do recall fabricating a great deal of aluminum handrailing for Nabisco Corp. on one project. It was a food related processing system. Regards, Allan
Parent - - By yorkiepap (***) Date 04-05-2007 17:52
Hey JettIndFab,
I've done quite a few railings, not quite as long, and generally the jigging would probably be the best route to start to reduce your distortion. I completely agree with Allan Evald's summation, especially with trying to really apply some heatsink to the tubing. Additional clamping will benefit also. Can you heatsink your tubing internally? Any thought given that you may have better results by switching to MIG welding?

Keep us posted...Good luck...Denny
Parent - - By aevald (*****) Date 04-05-2007 18:31
Hello Denny, you brought up a very good point regarding using a GMAW process instead of the GTAW. I can only guess that when he made the statement of having a #4 finish on this rail that aesthetics might be an issue in this application and achieving a uniform and clean weld finish is an issue here. Certainly a properly done GMAW weld would aid in his distortion issues, but might bring up some weld finish challenges. That's only a guess on my part though. Great point Denny, regards, Allan
Parent - - By MDG Custom Weld (***) Date 04-05-2007 19:40
We have done similar products in 304 tubing, and 316.  Heat sinks work with limited success because of the poor thermal transfer rates of SS.  It's hard to get enough heat out of the part quickly, and usually the part has already warped before the heat makes it to the cooling blocks of the sink. 

We set them up as drawn per the print, and weld it up taking exact notes on the welding pattern.  Then using a 10'x10' surface plate, we measure the distortion encountered.  With the amount of distortion accounted for, we adjust the fixture to 90% of the actual number measured.  This gives us some room to vary our parameters as needed to fill gaps and any other manufacturing variance.  It works well, but you have to factor in the time and material to make your "prototype" part.

Aevald and Denny also touch on a good point, GMAW when ever possible.  Even if you have to spend 10 more hours polishing, its worth it compared to scraping parts due to warp.
Parent - - By devo (***) Date 04-05-2007 20:14
  How is it that GMAW will give less distortion than GTAW?  Is it the travel speed?  I always assumed Tig would give the least distortion.  Is this unique to stainless or is it all metals?  Help this rookie understand.
Parent - By aevald (*****) Date 04-05-2007 22:12
Hello devo, the short answer is that the higher travel speeds and in most instances, lesser amounts of penetration, yield less overall heat input and thus help to limit the distortion somewhat. I believe you will find this will hold true with all of the materials that could be GTAW or GMAW welded. There is a much more scientifically based explanation as well but I don't know all of the details of that. So I'll leave that for someone else to answer. Regards, aevald
Parent - - By Joseph P. Kane (****) Date 04-05-2007 20:09
Try Sub-contracting it to Galloway in Tennessee.  They are cheap and really really good.
Parent - By jon20013 (*****) Date 04-06-2007 09:38
Since you should have some idea of which way the distortion is going (in general terms) try overstressing your joints in the opposite direction... I would definately go with a minimum of 3/32" filler too if you're looking for 1/8" fillets... reduce weld times will help reduce distortion but 316 (as js55 points out) is the beast of a material that already moves all over when welding...
Parent - By dschlotz (***) Date 04-07-2007 20:15
I know your pain, as I have been there many times before. Stainless is very tricky to work with because of the movement, (nontechnical term for heat warp)after welding. I have built miles of handrail in 40+ yrs. Whether it's mild steel, aluminum or stainless, the problem is caused by heating one side of the pipe with a circumferential weld, such as where the leg attaches to underside of the top rail. That side of the pipe shrinks (gets shorter) and the top does not. Hence the hated bump. I have had good success straighting rails by heating the top of each leg in the area directly opposite and approximately equal in size to the weld that holds the leg in place. You probably don't see warped legs at the mid rail joints except at terminal ends where they are welded only on one side.

You will have to play with the heat a little to get the results you need. I use this method. I heat until I see movement and let it air cool, without using force . If I get it right the first time I am amazed and smile because it takes a little getting used too. I never cool down with water as I feel it is too unpredictable and may even cause wrinkles on thin wall material.

The other posters are giving you good information when they advise you to use as little welding heat as is required.

Dennis
Parent - By deacon3j Date 04-12-2007 02:50
Hi folks, I'm Dave the lead welder in the shop that is doing the handrail. I started learning this trade 38 years ago and not a project goes by that I don't learn something. This has been a real challenge! I learned long ago that stainless has it's own set of rules that it doesn't bother to follow!! I've read all your responses here and in other forums that this has been posted to with great interest. I've taken all your suggestions to heart and tried to apply them to the project with limited success. What may work on 1 piece of railing may not work on the next.
Here's what we have done.
Cut our weld sizes down as far as we dare and still have good welds. !/8 being the norm.
Clamped, clamped and clamped some more.
Staggered the weld patterns.
Stress relieved the joints with a dead blow hammer immediately after welding.
Adjusted weld settings both up and down, changed filler wire diameter.
Taken some old blacksmithing ideas and applied them, heat, quench and draw, PRAY.
All with moderate success, some better than others! 308l filler wire was what our supplier recommended to us. I went to them with questions before we cut the first piece of pipe. They said the same as everyone else, good luck Dave. lol!! We are slowly winning the battle. Thanks everyone for your advice, Dave Jones
Parent - By Sourdough (****) Date 04-13-2007 18:44 Edited 04-13-2007 18:47
How are you assembling this rail? Are you butt welding everything, or plug welding?

I don't think I've ever done a railing that hasn't needed some racking afterwards. They move a lot, no matter how well you clamp everything. Fortunately I have a waterjet to help with cuts.
Up Topic Welding Industry / Technical Discussions / Stainless 316 Handrail

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