.120 Mild Steel Tubing Help

[turboglenn]

Pushing the bead will result in a flatter crown with less penetration.

Pulling the bead will result in a more "humped" crown with more penetration.

That's my experience, and it can be confirmed in nearly any welding reference.

I agree with you though, that a slight weave will tend to flatten the bead. Penetration on .120 material should be a non-issue assuming your other parameters are set correctly.

Hmmm... I always get less of a crown with the pull so i had to check some references and alhough it does give better penetration (as stated by you, I and references i have found) the pull technique has always given me a lower profile and less rounded bead. Now i'm not argueing as there's too many variables that can be user/operator related, but just stating that i get lower profile beads with the pull technique when all other settings are the same on the machine and on the same material and joint type.

Sitting here thinking about it I would guess that the reason i get flatter beads is from the amount of stickout I end up running based on the technique i'm using at the time ( i tend to have more stickout when pushing)

As far as the rep telling you not to weave the bead from one part to another, I can't speak from a structural integrity standpoint but i do NOT weave when butt welding thin materials or working with tubing joints. I just use small bursts traveling in a forwad direction to avoid burn through. I should also add that i'm not nearly the weldor that 90% of the members here are, I'm more of a fab guy that welds, so i'm just speaking of what tends to work best for me.

[strictlycarved]

As for the weaving im not certified for anything structural with a wire feed. I use a stick for that. But i weave very little usually not at all but i use a wire feed for building gates and building some buggy cages. Never had a weld fail with the technique that i use.

[hotsparks]

I've read on this forum, others and in books that to flatten a mig welding bead increase the voltage or reduce the wire speed.

It works for me.

John

[SundownIII]

Turboglen,

Not going to retype the whole passage, but if you're interested, I refer you to page 46 of the Miller GMAW handbook. This section deals with Direction of Travel-Type of Technique.

This manual can be downloaded or ordered in hardcopy as part of the Miller Student Pack ($25 including postage). The student pack, not only includes the GMAW handbook, but also an excellent TIG Handbook, along with a bunch of other goodies. Best $25 you can spend in welding.

Be careful of those "short bursts". Each one of them has the potential for a "cold start". A push technique is often used to reduce burnthru as the penetration is less.

When pulling the gun, the arc/heat is directed at an already molten puddle (preheated if you will), whereas with with a push the arc is directed at solid material. Think about it.

I use both techniques, just depends on what I'm trying to accomplish.

[KarateBoy]

I am a little confused.

I always PULL on thin metals to get LESS penetration. My thinking is that I am moving AWAY from the heat.

[PLWeld]

KarateBoy,
I wanted to try and help clarify this burn through discussion. If you think about burn through, at what point of the weld bead does burn through take place? At the puddle, right? So, Sundowner is right. If you are using a pull technique in an already molten puddle and already extremely heated material, as you move along you are creating more heat and thus more molten temps than the thin wall can handle.......unless, of course, you stop welding and let it cool. With a pushing technique, you would essentially be pushing the filler metal into still solid material, which has not reached the temp of weld bead or puddle yet. does that help?

Also, on the issue about weaving your weld bead, especially when welding tubing. The claim is that when weaving while welding this tubing is it generates even more heat than necessary and can cause undercutting at the shoulders of your weld bead. Make sense? I never weave when I'm welding thin wall tubing, just a nice, even straight bead and has always worked well for me.

[nocheepgas]

Also, on the issue about weaving your weld bead, especially when welding tubing. The claim is that when weaving while welding this tubing is it generates even more heat than necessary and can cause undercutting at the shoulders of your weld bead. Make sense? I never weave when I'm welding thin wall tubing, just a nice, even straight bead and has always worked well for me.

I wouldn't consider .120 as "thin wall" and always weave, making sure I get a goot tie in on both metals and fill any undercutting. Welding a buggy frame, I'd definitely weave! On thin stuff like 14 gauge or higher, then weaving does put too much heat into the metal and also creates severe warpage problems.

[On fire most of the time]

Im not so sure I'd call .120 wall thin tubing either...

Most of the roll cage material I work with is thinner than that, at .095.

My best advice to you is to stay 90' to the joint at all times, and when fitting the two pieces of tubing together, make sure that you eliminate the feathered edge of the tubing...a quick once over with a sander will fix that. Ive seen several cages crack when the fabricator didnt fit the tubes very well.

If you stay 90' to the joint, and you have the welder (and weldor) set up right, shouldnt have any issue.

[Craig in Denver]

Not going to retype the whole passage, but if you're interested, I refer you to page 46 of the Miller GMAW handbook. This section deals with Direction of Travel-Type of Technique.

Since you made me look, I'll type it.

Quoted from the Miller GMAW handbook:

"There are some distinct advantages of a push technique. One advantage is when relatively thin materials are to be welded, or when doing a process such as hardfacing. Low penetration would be required, and a push technique along with a faster travel speed can help achieve this in certain applications. The concentrated heat and arc force are now directed away from the weld puddle (and its thermal heat). This generally results in less penetration and a flatter, wider bead."

This manual can be downloaded or ordered in hardcopy as part of the Miller Student Pack ($25 including postage). The student pack, not only includes the GMAW handbook, but also an excellent TIG Handbook, along with a bunch of other goodies. Best $25 you can spend in welding.

I agree about the best spent $25 in welding, along with Lincoln's Procedure Handbook of Arc Welding, also $25.

I use both techniques, just depends on what I'm trying to accomplish.

Worth learning both directions, someday you may need it.

[Vicegrip]

To much Stick Out? More stick out the taller the bead among other things.