weld penetration

[rusmannx]

Yesterday I took my first crack at welding tube, and it didn't go very well.
This is some 2" / .125" wall stuff I got from my local machine shop (I think it
is HREW).
This is a butt-welded piece cut into a strip (like peeling a banana) after welding the tube.
I pounded on the weld face until bending the strip into a u-shape.
This crack is the backside of the weld. This heat/speed setting would
bring the inside of the tubing to a nice glowing orange, but never filled
the weld through the entire cross-section of the material. I did bevel the
outside edge, and any more heat than this made a mess.

Should my welding result in all tube material fusing from OD-ID?

 

[Wile E Coyote]

Bevel a bit more, more heat/wire speed or slower travel speed. Yes, you should be getting more penetration.
What's your welder, it's settings, shielding gas used, wire selection, etc?
Are you butting the joint tight, or leaving an ever so slight gap( roughly wide as your wire diam.) before welding?

 

[rusmannx]

Lincoln 175 (setting c-4) with .025 wire and CO2/Argon.
No gap really.
What would be an appropriate width for the bead?

 

[Jetboy]

You really should start with about 1-1.5 /16ths of an inch. Maybe even an 1/8 in of gap. With the pipe butted together you'll have a very difficult time getting adequate penetration. It's probably best to bevel the ends, but in that size and thickness of pipe a small gap will work fine. Now if you were dealing with 1/2" wall tube, you'd never get a good welt without beveling the edges. It's definately possible to crank up the heat and penetrate all the way, but it's not going to work all that well. It may be beyond the capacity of your welder to do that, but I've never used a 175 so I don't know. Anyway, try it with a small gap and you'll get better results. Good luck.

 

[Wile E Coyote]

Don't know what c-4 translates to, but try it w/ D-5 and see what that does.
You might need a small gap in the joint to aid penetration if more heat doesn't do the trick. Again, only need 1/16" gap or so. Your weld is 'sitting proud' as I see it, which means it's just sitting on the surface.

 

[rusmannx]

I'll be back at it this weekend. I'll try the gap method.
Thanks.

 

[Wile E Coyote]

The 175 is capable of proper penetration w/ 0.120 wall tubing.

 

[Jetboy]

I'll be back at it this weekend. I'll try the gap method.
Thanks.

The gap can be a little tricky, more so on thinner pipe/tube like exhaust. The best Method IMO is to kind of work side to side so that you don't overheat the center of your puddle and have it collapse through. You'll figure it out. Too much heat can make it difficult. When it's going well there will be some crowning over the joint, but not a bunch. It shouldn't look like you wrapped a rope around, but more flat. If you're getting too much build up it may indicate that you're too cold. Also It will assure you get to spend more time with a grinder.

 

[nat]

Do not gap your joints before welding. Properly fitted parts will yield significantly stronger welds. Look at the manual for your welder. Set the voltage and wire speed to what they recommend for 1/8" wall material. Practice, practice, practice.

 

[nat]

The gap can be a little tricky, more so on thinner pipe/tube like exhaust. The best Method IMO is to kind of work side to side so that you don't overheat the center of your puddle and have it collapse through. You'll figure it out. Too much heat can make it difficult. When it's going well there will be some crowning over the joint, but not a bunch. It shouldn't look like you wrapped a rope around, but more flat. If you're getting too much build up it may indicate that you're too cold. Also It will assure you get to spend more time with a grinder.

Sorry, but this is bad advice. Welding wire should not bridge a gap to create a joint.

 

[Poser]

Do not gap your joints before welding. Properly fitted parts will yield significantly stronger welds. Look at the manual for your welder. Set the voltage and wire speed to what they recommend for 1/8" wall material. Practice, practice, practice.

Ding!

 

[Pin_Head]

It is a good thing to test your welds.

Besides proper joint design (beveling and root gap), the "key" to getting full penetration on pipe is to look for the "keyhole" forming on the root pass. The keyhole is at the leading edge of the puddle and is wider than the root gap. The keyhole forms before you burn through, so you need to keep the keyhole moving forward. If you can see the keyhole, the pepetration is reaching the back side. If you don't see the keyhole, chances are you will have less that complete fusion.

Practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test, practice, test.....

 

[rusmannx]

Do not gap your joints before welding. Properly fitted parts will yield significantly stronger welds. Look at the manual for your welder. Set the voltage and wire speed to what they recommend for 1/8" wall material. Practice, practice, practice.

alrighty then, i'll NOT gap the joint, i'll try more heat/wire speed or slower forward movement.
if you were welding this joint how wide of a bead would you be leaving?
1/4"?
3/8"?
1/2"?

 

[jasonmt]

Sorry, but this is bad advice. Welding wire should not bridge a gap to create a joint.

Speaking of bad advice, on a single sided butt weld a root gap and bevel is what allows you achieve complete penetration. The filler material is not "bridging" the gap but filling it in.

There is a reason why 95%+ of code weld procedures involving this type of joint and weld process have allowances for a root gap.

Due to the nature of the transfer mode and size of machine being used in this case I would personally go with either a bevel with feathered edges butted tight or a 1/16" land and 1/16" root gap to start.

 

[nat]

Sure, you can have a small gap, less than .060" if you know how to fab and jig parts up.............

................but to recommend to somebody, learning to weld, to leave a 1/8" gap


What if this guy wants to TIG later? The cleanest TIG welds do not have filler rod, they are fusion welds. Do you really think that could be accomplished with even a .060" gap? Nope, perfect fitment is most important.

 

[Wile E Coyote]

Now, that our OP is sufficiently confused:
As I stated, a root gap near the thickness of the wire (1/16" is 0.0625" by the way) is acceptable for this application. Bevel the edge to within 50% of the edge thickness, leave a root gap, or completely butt them, and weld away. Since this is not a real-world application, it's not a cumbersome weldment that needs jigs to maintain the root gap. A guy could do this in a bench vice, for pete's sake.

I don't think it was fair to make such a black and white statement implying that no gap whatsoever is the only way to weld this joint, and then dance around the subject later.

Rusmannx, I'd recommend poking around on weldingweb.com or one of the other numerous welding specific sites where this might get more expert critique.

 

[nat]

hahahaha

Likely he is using .030 wire or something near that. By using your logic of wire size = root gap he needs to be using a gap nearer to 1/32" or .03125"

What you may not realize, capilary action will not hold molten metal on any size gap.

My original advice still stands. Learn how to properly fabricate and fit parts together. It will create a stronger joint.

Practice, practice, practice. Try and use a sledge to break your joints. Practice some more.

 

[jasonmt]

Sure, you can have a small gap, less than .060" if you know how to fab and jig parts up.............

................but to recommend to somebody, learning to weld, to leave a 1/8" gap


What if this guy wants to TIG later? The cleanest TIG welds do not have filler rod, they are fusion welds. Do you really think that could be accomplished with even a .060" gap? Nope, perfect fitment is most important.

Why confuse the issue with GTAW then autogenous GTAW, the OP was asking about a specific process that was neither.

Different processes have differnt joint designs that they work best with, you would not fit up a GTAW joint the same way as a GMAW-S joint or a SMAW joint.

Good fit-up is important but so is actually having a good grasp on the subject manner you are attempting to give advice on.

 

[fj40charles]

There is nothing wrong with beveling the metal before you weld. Try to leave a land on the bevel so you don't blow though the metal.

You'll get better penetration and for lots of people using small 110v welder, is really the only option for welding metals thicker than 1/8" with solid wire.

We should keep Tig welding out of the thread since the process is very different that wire feed welding.

 

[Wile E Coyote]

hahahaha

My original advice still stands. Learn how to properly fabricate and fit parts together. It will create a stronger joint.

Practice, practice, practice. Try and use a sledge to break your joints. Practice some more.

What you appear to fail to consider is that using a root gap in the proper application IS proper fab and fit up. TIG does not equate MIG due to transfer characteristics amongst other things.

Remember, I first stated the OP should try more heat, then a small root gap (he listed he's using 0.025 wire BTW) Using the wire as a rough gauge for gap size was just for easy visual representation, sheez.
Welding for cert is stupidly precise, but that's not what the OP is after. There's more that one way to skin this cat, can we agree on that much?

I'll def agree that relentless practice is the best medicine.


I'll not muddy up this thread anymore w/ what's turned into a pissin match. Nat, the is on me if'n we ever get the chance.