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Welding question - think vs. thicker wall steel tubing

The Dude

Hot Rolled
Joined
Oct 19, 2010
Location
Portland, OR
Hope someone here can answer this. Looking at having a bunch of items made from 2" sq tube steel. The only question is about wall thickness. I want them as light as possible (for good reason). We plan on using 0.065" wall thickness but I got questioned on the "weldability", being told that it would need to be TIG and, therefore, would take a lot longer (suggested to go to 0.120" thk).

I don't roll over that easily on a recommendation (it was from a small shop), I am confident that 0.065" will be strong enough the design load and any "bashing". Just wondering if the welding is really that much of an issue or is it more that this guy just can't weld MIG on the thinner wall.

I know that cost of the tubing isn't much of an issue (about $1/foot) but the weight will be a functionality and safety issue (it's a cart that doesn't carry much cargo weight). So, what say the welding experts? Can I expect to pay a lot more for all things being equal except 0.065 vs. 0.120 thickness?

Thanks,
The Dude
 
well, i'd say largely a matter of skill to mig .065, shouldn't be a problem at all, but it depends a bit on joint design, fit up ,(as stated above), and performance requirements (cyclically loaded? fatigue prone?), and volume.

can you include some pics of the joints? intended application? number of units? ASTM 500B?
 
TIG is much slower, meaning your sitting on the part longer, leading to more warping.

The thinner tube has a tighter radius, so the cross
tube connections don't have as much of a gap.
 
O/A bronze welding is another option, .........I've lost count of the number feet run of bronze I've done on 1/16'' / 1.5 mm tube, .but I know it's a LOT
 
I stick welded .065 tube for most of my career. It helps if you're over 18 years of age, don't have a cell phone, don't have fishing tackle hanging from your nose, ears and lips and have been schooled in welding, just a wee bit.

Stuart
 
TIG is much slower, meaning your sitting on the part longer, leading to more warping.

Kinda disagree with that, if your any good, you can do a lot more than the rule of thumb of 1 amp per thou of thickness, on 16 gauge im commonly about 110Amps these days and with tig theres no splatter to clean off and very little weld to grind on flushed off jobs. With pulse you can bump the current even more, which lets you bump the travel speed which reduces your total heat input and drops distortion. yeah it takes some skills and a mig monkey that can't MIG 1/16" material sure as hell is not going to be fast TIG'ing it either.

With skills though and if you include all weld time + clean up TIG should not be all that much more on typical tubular structures you just spend a bit more torch time in place of grinder time and de-splattering time. End product also looks so much better.

Loads of people get hung up on the slower weld bit, but on typical fab work the actual torch on time is such a small percentage of a welders day its really not making all that much difference if it did take twice as long for a given weld not that it should! Setup and clean up are almost always the real time hogs on anything short of fully jigged production welding.
 
Hey thanks everyone (that's about the most amount of useful replies in the shortest time on anything I've every posted in a forum) . My "consensus", after reading this is that MIG should be fine. It's all square cuts so it would be fillet and butt joints (I'm assuming it's a butt joint where a tube end meets the side of a tube?).

I didn't want to get too deep into the application since that can easily derail the question. It's similar to a lumber cart like you see at Home Depot or Lowes but a much lighter carrying capacity (less than 100 lb of couch cushions). It will be about 8' long, 3' wide and 7' tall with two center casters and one on each end for easy steering. It will have three "bed" rails to form the base, three uprights on each end and some side bracing on one side (so one side is open to lay foam into). Plywood floor will be routered and nested into the bottom. Appropriate cross-members (sideways 2" tubing) and caster plates (laser cut) will be welded on. As stated originally, weight is a critical factor since these are "running around" a very high-paced factory. We thought about making them out of wood but want something sturdy and dimensional lumber isn't exactly light.

I consider this question to be "fully answered" but feel free to add comments and, once again, thanks for all the input.

The Dude
 
Kinda disagree with that, if your any good, you can do a lot more than the rule of thumb of 1 amp per thou of thickness, on 16 gauge im commonly about 110Amps these days and with tig theres no splatter to clean off and very little weld to grind on flushed off jobs. With pulse you can bump the current even more, which lets you bump the travel speed which reduces your total heat input and drops distortion. yeah it takes some skills and a mig monkey that can't MIG 1/16" material sure as hell is not going to be fast TIG'ing it either.

With skills though and if you include all weld time + clean up TIG should not be all that much more on typical tubular structures you just spend a bit more torch time in place of grinder time and de-splattering time. End product also looks so much better.

Loads of people get hung up on the slower weld bit, but on typical fab work the actual torch on time is such a small percentage of a welders day its really not making all that much difference if it did take twice as long for a given weld not that it should! Setup and clean up are almost always the real time hogs on anything short of fully jigged production welding.

I weld a pretty good amount.

It's not the "time" I'm referring to about "get it out the door" time.

If you would please Re-Read my post #5, it's about how long you
are ARCING on the part.

I have done jobs that the "nice and clean TIG" welders can't seem
to handle (needing low distortion) yet I do my MIG as "Hot and fast".

Get on the part and get off the part.

They even tried a copper plate fixture, and cooling it with ice between parts.
My fixture needed nothing like that, and no cooling down cycle,
the thru put was much higher, and I met the tight flatness tolerance,
that the TIG people couldn't hold.

It's well documented, try Ed Craig.

And your telling me MIG is any less clean ?
Same gas shielding, and it's certainly not stick welding.

Plus, the OP's requirements for a "couch cushion cart" do not require
the "cleanliness" of a surgically applied TIG weld.
 
With skills though and if you include all weld time + clean up TIG should not be all that much more on typical tubular structures you just spend a bit more torch time in place of grinder time and de-splattering time. End product also looks so much better.

Loads of people get hung up on the slower weld bit, but on typical fab work the actual torch on time is such a small percentage of a welders day its really not making all that much difference if it did take twice as long for a given weld not that it should! Setup and clean up are almost always the real time hogs on anything short of fully jigged production welding.

Hello Adama
By chance, did you get your welding processes mixed up? Are you thinking of stick welding & not MIG?:crazy:

IMG_0141.jpg

Certainly not the 0.065 material that the OP is talking about, but just using this pic for a reference. How much time do you think that I had to spend with the grinder & de-splattering here???:rolleyes5:
ZERO.:cool:
 
Nope..strictly downhand. Moved and flipped to achieve said position. The sawmills in my area were in the dark ages. We had old military surplus Lincoln 'beehive' welders...ever seen or used one Ciszewski? :)

Stuart

Hello Atomarc
Only time I ever stick weld downhill is on thin material. Go like a bugger so that you don't burn through.:eek:
"Beehive" or "Bullet"?:confused: Do you mean the old Lincoln motor-generator machines?:confused:

Addition: I did a google image search for "Lincoln beehive welder" & all I saw was a bunch of bees, ... & 1 blonde chick with a real big hairdo.:confused:
 
Last edited:
Hello Atomarc
Only time I ever stick weld downhill is on thin material. Go like a bugger so that you don't burn through.:eek:
"Beehive" or "Bullet"?:confused: Do you mean the old Lincoln motor-generator machines?:confused:

Addition: I did a google image search for "Lincoln beehive welder" & all I saw was a bunch of bees, ... & 1 blonde chick with a real big hairdo.:confused:

I said 'downhand', not downhill! Big difference.:)

Yep, talking about the old MG machines. They used them in the shipyards by the bazillion. I used them in high school welding classes in the early 60's.

Stuart
 
I think "Lincoln torpedo welder" will get you the pics of those!

I usually TIG weld most things, just my go to, but for that application, MIG should be great. .025- .030 ER70S-6 or S-2 solid wire and, what, 17.5-18V? if possible use 10-15% CO2 instead of 25% for a cooler, less aggressive arc and less spatter.

hey The Dude, that isn't a butt weld, where it "Ts" thats a "fillet" (where it meets at right angles) and "flair bevel groove" (where the radius of the tube edge meets the tube end) .. I think. we just call it a T joint.

a butt weld is where the tube meets end to end.(oh shit! I cut it too short!:eek:)

actually for that job, I would fire up one of the MIG units for sure, sounds like fun. :)
 








 
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