MIG welding 3/4" base plate to 6 xx strong pipe

[ehart]

Any suggestions for machine setup for MIG welding a 6 xx strong tube ( 4 1/2" dia, 5/8" wall)
to a a 3/4" thick mild steel base plate for a steel column?

Can it be done with a Lincoln power mig 300? Or am I dreaming and do I need
a more heavy duty machine that can handle the amps?


Our engineer called for a 3/8" fillet weld with a single pass,
which seems crazy to me, but I see traffic light poles all the time that look to have a small,
single bead at the bottom.

I am planning on waterjet cutting a hole for the pipe in the base plate to have the opportunity to weld both sides.

Any suggestions welcome.

[ehart]

My mistake, its actually a 4 XX strong pipe.

[welds4d]

Personally, I would prefer to use dual shield over solid wire for that...

[ehart]

Originally Posted by welds4d

Personally, I would prefer to use dual shield over solid wire for that...

If I go with a dual shield wire, would you recommend a spray transfer?
What diameter wire?

[MoonRise]

Hmmm, 5/8 inch wall pipe going onto a 3/4 inch thick base plate, and the call out is for a 3/8 inch fillet weld???

The 'usual' weld fillet is for the fillet to be equal to the material thickness. So a little 3/8 inch fillet on 3/4 or 5/8 inch thick material seems a weeeee bit on the small side there.

As to machine settings, no idea. Because that will depend on the exact size and type of wire, as well as the shielding gas (if any) and the transfer mode used, as well as the machine.

But for that thick of a material, I really don't think short-circuit transfer mode is the way to go.

Hmmm, let's see. Even at an 'undersized' (IMNSHO) 3/8 fillet bead with NO bevel, you are still looking at ~0.28 lbs of filler metal in the weld bead. The circumference on that pipe edge is ~14 inches. Assuming a travel speed of ~14 ipm, that works out to a metal deposition rate of ~17 lbs/hr for a single pass weld. A 1/16 inch solid wire at ~400+ amps in spray transfer will get you ~15 lbs/hr, so even that size wire that fast/hot isn't quite able to put down metal that fast. A metal-core or maybe some FCAW-G (dual-shield) 1/16 inch wires cranked up near 400-500 amps might be able to put down metal that fast, but again that is hot and fast.

If this is an 'engineered' job, have the engineer research and spec out the WPS.

[Fred s]

If its gonna be solid wire, spray all day
300 amps is smallish for .045 hard wire in a big hot spray

[norite]

I'd just do like the engineer said. If it is a column then all the parts are in compression and there will be no load on the weld as long as the column remains vertical (no side load). All you need is a small weld to lock them together.

I wouldn't recommend cutting a hole through the base plate. The design may depend on the area of the base plate being what it is and if the pipe is run through the base plate and welded both sides, now the full load of the column is being applied to the welds which may not be adequate.

Sure wish I had access to a waterjet cutter though

[ehart]

Originally Posted by norite

I'd just do like the engineer said. If it is a column then all the parts are in compression and there will be no load on the weld as long as the column remains vertical (no side load). All you need is a small weld to lock them together.

I wouldn't recommend cutting a hole through the base plate. The design may depend on the area of the base plate being what it is and if the pipe is run through the base plate and welded both sides, now the full load of the column is being applied to the welds which may not be adequate.

Sure wish I had access to a waterjet cutter though

Actually it is a column for an art sculpture that is subject to wind loading. This will create
a bending moment and deflection at the base of the column ( which is why the pipe is such thick all). There will be stress on the weld bead, this is why I believe having it go through the plate will help relieve some of the stress on the weld its self.

The 3/8" weld bead seems rather small to me, do you think it depends on the process?
would it be smaller if it was SMAW?

Our engineer didn't have a feeling either way on the hole in the base plate. It also makes layout easier not having to stand the pipe up vertically for welding.

Thanks for the advice

[Scott Young]

why do you have to stand the pipe vertically. tack the plat on and weld. It would be the same as if there was a hole. I personally would bevel the plate and weld out and finish with a 3/8 fillet like described. Just clear it with the engineer. Spray or glob transfer with .035 or .045 is fine. If I were the engineer would sign off on it, esab 7100 ultra is a great dual shield wire that would make that weld a cake walk.

If you have bunch to do, get your rollers out and go to town.

[ehart]

Originally Posted by MoonRise

Hmmm, 5/8 inch wall pipe going onto a 3/4 inch thick base plate, and the call out is for a 3/8 inch fillet weld???

The 'usual' weld fillet is for the fillet to be equal to the material thickness. So a little 3/8 inch fillet on 3/4 or 5/8 inch thick material seems a weeeee bit on the small side there.

As to machine settings, no idea. Because that will depend on the exact size and type of wire, as well as the shielding gas (if any) and the transfer mode used, as well as the machine.

But for that thick of a material, I really don't think short-circuit transfer mode is the way to go.

Hmmm, let's see. Even at an 'undersized' (IMNSHO) 3/8 fillet bead with NO bevel, you are still looking at ~0.28 lbs of filler metal in the weld bead. The circumference on that pipe edge is ~14 inches. Assuming a travel speed of ~14 ipm, that works out to a metal deposition rate of ~17 lbs/hr for a single pass weld. A 1/16 inch solid wire at ~400+ amps in spray transfer will get you ~15 lbs/hr, so even that size wire that fast/hot isn't quite able to put down metal that fast. A metal-core or maybe some FCAW-G (dual-shield) 1/16 inch wires cranked up near 400-500 amps might be able to put down metal that fast, but again that is hot and fast.

If this is an 'engineered' job, have the engineer research and spec out the WPS.

Actually according to AWS the minimum leg of the fillet for a plate over 1/2" and up to 3/4" thick is 1/4". The maximum is the thickness of the thinnest plate - 1/16 of an inch.

[lotechman]

I also vote for no hole. If you do make a hole and weld from the inside it is likely the outside fillet will still be the primary stress location and the inside fillet placed on the end of the pipe will just sit there doing nothing.
A single pass fillet with only a 300 amp machine is marginal. Certainly preheat the plate. You don't need much .. say 200 F would be just fine. I would bevel the end of the pipe just a bit to increase the weld size/penetration and do it in two passes to ensure I did not have undercut or overlap. Normally a 3/8 fillet is the largest fillet allowed to be put down in one pass. A two pass weld refines the grain and on the negative side increase distortion.

[ehart]

Originally Posted by lotechman

I also vote for no hole. If you do make a hole and weld from the inside it is likely the outside fillet will still be the primary stress location and the inside fillet placed on the end of the pipe will just sit there doing nothing.
A single pass fillet with only a 300 amp machine is marginal. Certainly preheat the plate. You don't need much .. say 200 F would be just fine. I would bevel the end of the pipe just a bit to increase the weld size/penetration and do it in two passes to ensure I did not have undercut or overlap. Normally a 3/8 fillet is the largest fillet allowed to be put down in one pass. A two pass weld refines the grain and on the negative side increase distortion.

Thanks for the help. I do think however hole or not there is the same stress on the weld either way. The weld is much stronger than the
steel- 70 ksi for the weld and something like 30 - 35 ksi for the steel. The steel is made beefy to take the stress, not the weld.