[DLewis0289]

As I sit here looking at the failed UT reports, examining a macro and cussing the engineer (before offending any engineers, I am an engineer). 2" thick carbon steel plates, V-Groove, CJP (Complete Joint Penetration) with pre-heat and back gouging, etc.

This is why we are gouging tomorrow.....

The bevel was steep, but still manageable. Wire welding will let you deposit as long as you hold the trigger down. What has happened was the root pass was perfect, back gouged perfectly, filled all the way out, root pass cracks. Hell, the welds even looked good, right out of a text book.

Weld bead GEOMETRY!!!!!!! We shot so much wire down the gap (because we could) we produced a very tall but tapering thin weld bead profile at the root . As we filled and heated, the stress cracked the root.

Wire welding is a fantastic production tool, but in the unskilled operators hands or bonehead engineering procedure, could lead to catastrophic failure and in this particular case, unimaginable failure.

Procedure has been changed to a 8018 root with FCAW fill and cap. Wire is fine, but there is a reason when it comes down to the brass tacks why GTAW and SMAW are the preferred processes in my opinion.

[MinnesotaDave]

I'm not an engineer, so I'm shooting from the hip.

It sounds like you described an engineering issue, but blamed the wire.

I'm an engineer.jpg (29.65 KiB) Viewed 1682 times

[MosquitoMoto]

I don't Mig, not because I don't like Mig, just because at the moment Tig and Stick take care of all I need.

I am genuinely interested in seeing how this debate plays out. Hoping to learn something.



Kym

[DLewis0289]

It was an engineering issue and the wire facilitated the failure.

This is important....

fig 5.3.jpg (17.44 KiB) Viewed 1676 times

SMAW and/or GMAW would not lend itself this easily to high deposit rates such as this. MIG pull the trigger fill, fill and fill some more. I have seen nice looking wire welds break with very little parent metal attached. Don't get me wrong I have run miles upon miles of wire. I have also seen a lot of newbies weld just fine with wire with very little practice (flat), but don't really have a clue in the science of joining. Doing high production piping, we run a lot of pipe with wire in positioners, but the WPS keeps it in check.

I am really more pissed at myself for not anticipating it before hand and recommending a procedure amendment to the EOR for stringer controls.

[MinnesotaDave]

It was an engineering issue and the wire facilitated the failure.

This is important....

fig 5.3.jpg

SMAW and/or GMAW would not lend itself this easily to high deposit rates such as this. MIG pull the trigger fill, fill and fill some more. I have seen nice looking wire welds break with very little parent metal attached. Don't get me wrong I have run miles upon miles of wire. I have also seen a lot of newbies weld just fine with wire with very little practice (flat), but don't really have a clue in the science of joining. Doing high production piping, we run a lot of pipe with wire in positioners, but the WPS keeps it in check.

I am really more pissed at myself for not anticipating it before hand and recommending a procedure amendment to the EOR for stringer controls.

Sounds like you are talking about recommending more passes to fill so that individual welds are thinner in depth so they stay in a proper width to depth ratio.

I'm sure a welder (stick or mig) would appreciate this type of guidance.

[Antorcha]

I never MIG anything over 1/4-3/8 and don't go after 1/4 with anything less than my MM200.
That said....I love MIG for most stuff. No screwing around, nice and clean. Fast and you can't rip it apart.
Other than roof racks and crap if it goes on a vehicle or real structural item it met up with a 7018.

[thatoneguy]

While wire welding can have lack of fusion... A lot depends on the operator I think... Over time you learn to see if its penetrating or not. And you have to consider short circuit, spray transfer, etc...

[Diesel]

Got to agree with you. Mainly on the fact, a mig bead can look good but be bad. Im not knocking the penetration because it can punch through 1/2" plate with room to go if hot enough. But unless the operator knows, it is not a good idea. When I lay in a 6010/ER-70 root, I know it's in there. Mig is the only cert test I have almost failed. And I only took it because I had a few hours to kill while the boss was out. I even had the machine at 27.5/575. It was hot. I do not and will not trust a mig weld, veteran or not. Stick or tig please. That's why I will never work in a shop setting. I want out in the dirt and in the crap.

[DLewis0289]

Success, over a total of 80 linear foot of 1-1/4" plate T joint to 2-1/2" plate. CJP (complete joint penetration) with 8018 SMAW root and Dual Shield FCAW fill and cap. 100% UT inspection and passed.

IMG_20140414_072733.jpg (66.46 KiB) Viewed 1539 times

[The_Fixer]

Interesting. Over here it is routine to weld heavy plate with mig all the way, even to UT, X-Ray or pressure standards.

Full penetration welding on heavy plate primarily relies upon adequate clearance to get the nozzle in close, adequate root gap (if specified) and appropriate preheating. Followed by back gouging the root (preferably carbon arc) and dye penetrant testing. Not to mention correct welder settings as well.

Most mig welding done this way routinely pass tests. Root run failures happen for many reasons, one of the biggest would be too tight a weld prep. I suspect a lot of this would be from the joint being too tight and the welder needs to increase the stickout to get his angle right. Result is voltage drop at the arc and potential inadequate gas shielding.

Most high level structural and mining specs call for flux cored wires with argon mixes. CO2 shielding is used here and there, but its use doesn't seem to be as common any more. Even 6G tests are done with flux cored root runs.

I was running a night shift some years ago building Marion Dresser draglines for our mines. All positional welding was done with Verticor 3xp and flat welding was Fluxofil 11ni. Long flat runs were submerged arc. Almost all failures were simply visual minor finish defects which were fixed within a few minutes. Most of the guys performed some astonishingly good finish levels.

Incidentally, our weld procedure prohibited SMAW.

[DLewis0289]

You nailed it, exactly correct bevel to steep, to tight, to much stick out and fill.

[The_Fixer]

I also noticed you guys weave your welds a bit over there.

On our spec. welding here the only weld permitted to have a weave is vertical up, which I think offhand is 9x wire dia. max weave. Otherwise it is pretty much frowned upon over here.

We can get away with a minor weave in other places, but if the inspectors notice it, they will fail it. However, some will do it on everyday work where no independent inspector is involved. But for us, it is not a good habit to get into.

When I was doing my #8 ticket (at the time, a high end bare wire mig) course we were told to do smooth transitions on our multi run passes. If the inspector could actually feel the join between 2 stringer beads with his fingers, you would fail the test.

Just noticing different ways things are done. Australian and American welding codes certainly have their differences.

But your weld you showed looked very tidy though.

[DLewis0289]

My dad and I did some very heavy flat stuff for Caterpillar and ESCO using Sub-Arc years ago, beautiful welds. On your flux core 6G roots you running up or down?

[The_Fixer]

Spec is up.
We were using some sort of Lincoln flux core. I don't really remember what is was, never heard of it before. It ran very blobby, and was tricky to master.
I never did, so I ended up doing the fabrication and there weren't too many welders that passed to do it.

This is the project we used it on: http://suneng.com.au/projects/commercia ... p-stadium/
This company has wound up in Australia and moved to China, like so many big companies here are doing.

[DLewis0289]

VERY NICE project. The large plate project we were doing were trusses that were going to be embedded mostly in concrete to hold up a hi-rise, never to be seen lol. And America is right there with you guys, years ago we came up with the brilliant idea of NAFTA, North American Free Trade Agreement......all of out companies left and went to Mexico.

[AKweldshop]

Just my opinion,
but the title of the thread should read "Why I have never trusted certain individuals skills to run a wire welder."

[DLewis0289]

Lol, yes you are exactly right!