Butt-welding S.S. 16ga. sheets with minimal distortion

Date 07-09-2007 08:07 Edited 07-09-2007 08:13

I am really not sure how things will react with a concrete backing but....

Does this have to be a full pen weld? Since its being screwed down anyway could you just lightly fuse the metal at the surface and be good enough? If not then your right that heat input will be a problem.

Do you plan on setting a gap? That will help prevent buckling but could be hard to hold on such long lengths. How close to the edge and how far apart will the screws be...and how deep are the anchors?

Copper is good for drawing heat away from you joints that will help. Basically your trying to limit the effect/draw of the heat input by removing it from all but the weld joint itself so... We use copper strips clamped around the stainless near the joint...it has the effect of temporary reinforcement plus it absorbs the heat. Since you don't have the option of clamping your might consider some weights to apply on top of a strip of heavy bar stock on each side of the joint. If more than one person is welding at the same time I think that having them weld parallel on opposing sides of each sheet might also help. Interesting problem....I can't wait to hear some others take on this one.

Regards
Tommy

By METALFABRICATOR Date 07-11-2007 03:14

Hi Tommy,
Thank you for the great advice. I just wanted to answer a few of your ? . As for the anchoring, it's really up to me. Any spacing, any distance off the edge, and any type of anchor as long as it is S.S. and flat headed. As for the actual weld, they require a seal weld only (fusing O.K.). I can gap the fit as I wish. However, I thought if I did it would only require more heat to make the weld. What do you think? We will have two welders going - any advice as to what sort of sequence would be best

With regard to DaveBoyer's post, I, as well, was concerned about the concrete. Therefore, I wonder if it would be smarter to fit and weld the joint placed on top of a sacraficial strip of the same material. This, in itself, could help absorb some heat from the weld. I could also use the "heat sink" that Greg G recomended which was easily accessible through my welding supplier after all. Of course, what I'll loose here is the restraint because I can't anchor with this strip underneath.

I have every intention of starting with a test piece about 8 or 10 foot long. I am able to do this without absorbing much cost becuase I need some 3" strips. These will be bent to form angles which will be used to frame three obstuctions already mount to the floor in the field I am cladding.

Thanks Again,
Charles

By Tommyjoking (****)

Date 07-11-2007 10:45 Edited 07-11-2007 11:37

Charles, please forgive me but I am going to try my best to be thourough as I can. "great advice" thx but no not really I am just fishing the possiblities.

"I have every intention of starting with a test piece about 8 or 10 foot long." Dang striaght and probably more than one!!! I cannot express how imprtant it will be for you to prove out the method before doing this one.

Firstly with regards to the end result being totally flat.....I dont think that is possible at all. I do think you can do this and keep it very flat...but not as flat as a floated concrete floor. If nothing else temperature differentials will affect this covering for its entire service life..metal expands and contracts with temp changes at a much different rate than the concrete. How flat its really got to be is the key to this job!!!!!

The fusion method is the way to go here since you said its allowed. Also understand that your welders should not be penertrating more than 50% thats about .030. If backing strips no matter what the thickness will prevent the use of the screws then I am against that....if a thin backing strip can be used with the screws and anchors that will only help. A mechanical anchoring will really help in regards to buckling of the sheet. Now the bad news...since its 16ga I would not want more than 5-6 inches of distance between the anchors....and I would have them about 1/5 inch from the edge minumum. I know thats a bitch but hopefully the job is not already bidded or its range bidded. I have no idea where you would get ss anchors .....If its permissible I would use zinc..avoid the plastic type. A 1/2" to 3/4" #8 or #10 would handle the job.

When you fuse weld stainless with no gap you will get "rooftop" or arching of the material at the joint. One way to help reduce this ( you cannot eliminate it entireley) ir by placing chiller blocks at the weld deposit quickily. Chiller block a small aluminumum pan of ice water or dry ice in water placed directly on the weld deposit within a minute or so of the weld. This artificial cooling is dubious in weld quality however for the stresses involved in this application it may be very appropriate. A good shot of compressed air can have a similiar effect.

The process: Please understand that all that follows is consdering a heavy weight and thick bar stock strip is placed beside each weld area and moved along accordingly (1/2 inch distance max on Both sides) Fit and anchor all the plates with no gap to 1/32. You have not said how it will be tied in to the walls I would rather start there but........In the center of the workspace.... Start your welders in parraell tacking each end in on opossite sides then welding no more than four inch stitch welds on each end. Divide that distance and place a four inch weld in the center again simultainliuosly on oppsite sides of the sheet. Now move out to the next joint 90 degrees from there and repeat. Keep this process up till you covered up to the wall joints...by the way what is being used to "seal" at the walls??? By doing this you are providing tension across the sheets ...kind of pre stressing the fit. Now go back and divde the distance between the welds and do a four inch stitch again. After rotatating 90 degrees around the sheet...I think you should repeat on the same sheet then complete the weld in parraell. Move out to the next opposite sheet and repeat... untill your welders are working the wall opposite each other unto completion. As far as obstructions ...just apply this same process around them ....keep thinking pulling tight against somthing else like a tug of war and you will get it right. Just weld/pull oposite.

This should be a pricey job to say the least if they expect a flat floor that will last! So take it into consideration that a stainless floor like a a slab will not be acheivable...unless they want to by a pre cut sheet to drop in from above. but I think you can get close!!! iN THE END YOU JUST NEED TO TRY IT OUT test wise and see if it meets the customers wants. Thats how I would handle it if it were my money on the line.

Best of luck to you Charles!!!

Ok you guys can tear it apart now.

Tommy

By Joseph P. Kane (****)

Date 07-09-2007 13:57

I do not believe that this can be done in place, if you want it kept flat. There will be considerable warpage. If you could weld the seams first on a JetLine Seamer and planish the seams flat, you would have a chance. My advice is; Do not lay out any of your own money on this project and try not to be responsible for the results.

I have had projects like this offered to me in the past. Thank God I did enough investigation before hand, and did not take the jobs.

By Greg G. (**)

Date 07-09-2007 15:22

I have a suggestion for you. It is a paste and it is call " Heat Fence" it works great. Just put it along both sides of the joint and it absorbs most of the heat that will cause problems for you. It my come in a roll like tape or in a tube and you apply it just like you would tooth paste on the material. Do not spread out as it will loss it's effectiveness. I do not know your flatness requirements but I can tell you this will help a lot.
Ask your salesman at the welding supply, he will have it or he can get it. Some people do not know about this so you might have to educate him on it a little. After you are done you just pull it up and throw it away. PS. you will not be able to keep the material 100% flat.

By TimGary (****)

Date 07-09-2007 17:10

My expierience with welding on top of concrete has resulted in the concrete adversly reacting to the heat through minature explosions. This "popping" causes flakes of concrete to fly every where and will contaminate the joint with sand like particles that will cause numerous pinholes.
I suggest doing a test piece so you can see what I mean.

Tim

By Greg G. (**)

Date 07-09-2007 17:38

He might be able to fuse weld it with a good fit. Then he will be able to move faster over the joint. Like you said he should try a sample piece. I don't know the flatness or the strength needed. But check into the heat fence it will help if not in the application then in another.

By DaveBoyer (*****)

Date 07-10-2007 03:51

Pay attention to Joe Kane's and Tim Gary's posts. Not only will the concrete spall and contaminate the weld, those concrete chips will be between the plates and the floor like scattered gravel. If the plates were not in contact with the floor the problem would be less likely.

By Greg G. (**)

Date 07-10-2007 04:42

If he is not willing to try it on a sample piece how will he know for sure. I think that if moves fast enough, he might be suprised.

By Tommyjoking (****)

Date 07-10-2007 06:55 Edited 07-12-2007 02:59

Dave excellent point...how could you keep busted concrete from getting in the joint much less from building up under the plates! Distortion can be controlled to an extent...the concrete makes this really screwed up. Joe is absolutely right ..don't let yourself tie money into this....I really think its dodgey myself....I just wonder if its impossible or not...is there a way to make it happen reliably.

I do agree all I have seen concrete do with the heat necessary for any kind of welding is basically explode at the point of exposure....just run a torch flame across a concrete floor with a good grinding sheild on. Without a gap (which a dont see how you can do it really without some kind of backing strip) the chances of distortion are much higher. Fusing a sample plate fastened in the same way over a test piece of concrete might be worth trying. If some backing strips at the joint of either copper or 304 were permissible (flatness) it might be a solution. If its do-able at all any way you slice it the amount of heat used will be very critical.

ooops...

By bozaktwo1 (***)

Date 07-11-2007 17:13

I have done a lot of 304 16 ga. counter tops like this, and yes the heat input is critical to control angular distortion in the joint. In my opinion, if he spaces the fasteners alongside the joint and closely enough together, a consistent seal/fused weld shouldn't cause too much distortion (there is always some); then planish each section as it cools. I think that if he fuses it to about a 50% penetration, there won't be enough heat input to cause damage to the floor on the backside. I have seen this happen, but the amount of heat that it took was pretty significant. Also, this assumes there is moisture in the concrete, right? Wouldn't a dry floor reduce the possibility of explosion?

By METALFABRICATOR Date 07-11-2007 03:24 Edited 07-11-2007 03:28

Hi,
Thank you for the great advice. My supplier has sold a product by "Tempil" that he recommends and says it comes in a cartridge like what is used in a cauking gun. Only about $15-$20 a tube. So this stuff really works huh?
Thanks Again,
Charles

By Greg G. (**)

Date 07-11-2007 16:10

Yes, this stuff is wonderful. I am wondering why more people don't use this stuff. I hope it helps you solve your problem. Please let me know if it was a success or not. You know plumbers use this stuff all the time.

By aevald

Date 07-11-2007 17:40

Hello METALFABRICATOR, you received a number of really excellent replies to your question and I, like the others might have a couple of suggestions that you might take into consideration also. When you get ready to fit the edges of the pieces together you might want to butt the two edges together with the shear burr side up as much as possible, thus when you fuse these together there will already be somewhat of a readily available filler to help with bridging and filling the joint. When you fit pieces with both of the shear burr sides down there can be an amplifying effect of the draw of the joint due to the slight rolled edges.
   Try to make sure that you have as tight of a fit as possible to avoid the need for additional filler, plenty of tack welds hot and fast (yet small) to avoid having the edges melt away from one another, probably no more than 1 1/2" to 2" apart.
   To help with the heat sink and suppliment the heat barrier substance you might want to have a couple of 3/4" to 1" x 3" or so copper bars a couple of feet long with one edge machined with a bevel along the long side. take two of these bars and place them so that the weld seam is between the two bevels and just close enough and centered on the joint to allow access with your torch assembly. Find some REALLY HEAVY weights that you can place across the ends of these bars to hold them down. Then weld a couple inches or so and planish the weld and skip around to minimize the heat to any one area.
   These are just a few more suggestions to possibly help you with your project. Good luck and keep us apprised of your success. Regards, aevald

By Greg G. (**)

Date 07-11-2007 17:55

That is some good advice. Sounds like you have done some fuse welding on sheet metal before. Keeping the material from deforming can be troublesome without any bends in the material. I think that he can do it if he moves fast an does not penetrate to much.

By aevald

Date 07-11-2007 18:19

Hello Greg G. I agree with your speed suggestion also. He would experience less heat attributed distortion with the faster travel and less dwell time for the overall welds. I thought about suggesting possibly using a pulsed welder set to a fairly high pps. instead of his current machine choice, but that may not be in the cards for him. My logic there is that sometimes at the higher travel speeds the pulsed currents help to promote a more consistent fuse and are less likely to allow the arc to wander in a situation like he has described. Just a few more thoughts. Regards, aevald

By Tommyjoking (****)

Date 07-12-2007 03:06

Allen,

Just a question its been mentioned serveral times here....Planishing....I am familiar with a roll type planishing machine (usually right beside a seam welder). But in this case are you using the term in regards to beating it down with a hammer...right??

Best Regards
Tommy

By aevald

Date 07-12-2007 03:59

Hello Tommyjoking, I believe you could either use a hammer (not my preference) or you could possibly use an air hammer with a flat-nosed tool bit. Essentially, whatever type of process you can come up with that will help to stretch the weld back out a bit and relieve the shrinkage stresses. Hope that's what your question was about and that I understood it correctly. Regards, Allan

By DaveBoyer (*****)

Date 07-12-2007 04:07

Do You have to seal weld the fastners too?

By METALFABRICATOR Date 07-12-2007 22:34

No. Here is another thought and maybe worth trying. I have used an epoxy anchor to set sheets on the floor in the past. This allowed me to get away from screws or other mechanical anchors. To my knowledge, these sheets are still anchored to the floor quite well. I have no idea if there will be enough strength to hold it after welding.
Thanks, Charles

By DaveBoyer (*****)

Date 07-13-2007 04:24

Epoxys will not handle temps above 300F, so don't use it too close to the welds where it will get too hot.

By DaveBoyer (*****)

Date 07-13-2007 04:32

If You don't have to seal weld the fastners, what is the point of welding the plate joints? Set the whole damn thing in an elastic epoxy and be done with it.

By METALFABRICATOR Date 07-12-2007 22:39 Edited 07-13-2007 00:15

Thank you for the great advice. I have always heard it was best (for distotion purposes) to leave a small gap between any butt-welded joints. What do you think? Is it in this case that the benefits of not contaminating the joint would outway that of minimizing distortion?
Thanks, Charles

By DaveBoyer (*****)

Date 07-13-2007 04:28

A gap equal to the ammount of the heated material's expansion sounds like a good idea to Me. Maybee .010"?

By monsoon12 (**)

Date 07-16-2007 02:11

Im just wondering if you can weld some of the sheets off site?Like when i use to run pipe.We would weld everything possible before installing.This way minimizing the welding on site.Im not sure if you would be able to use that type of method.If you were able to then it gives you more options in your welding.When i use to weld on custom boats that had thin steels we use to use a method with some angle iron an cut small oval holes were the weld would pass by.They stayed straight an you can use the angles over an over again cause you just had to tack them in place.Well hope it helped alittle an good luck,