MIG Penetration??? Part II (sorry but it's a bit long)

[BillC]

I must confess that at this point MIG scares me a little (OK, a lot...). At school I have been practicing on 1/4 inch material running around 25 Volts with the Millermatic 10A wire-feeder at setting 38 (whatever that correlates to in IPM) with C25 shielding gas at 20CFM. Is this a Globular transfer setting or is it still in the short-arc range?

Today I decided to practice on 1/8 steel and I set the machine to 22 Volts trying to run short-arc. I adjusted the wire-feed until I got what I think is a decent bead profile, then ran a fillet on one side of the 1/8 steel. The bead looked great until I hit the steel with a hammer and the weld came unglued after two strikes... There was NO penetration into the base metal.

I repeated the experiment with the machine set back at 25 Volts. I beat the vertical plate flat onto the fillet and had a heck of a time bending it back up straight again. The worst it showed was a crack along the upper toe of the fillet weld, but it never gave up...

Is MIG really that unforgiving or am I just doing stupid things? It is scary that a decent looking weld can fail that easily. I admit that I did not clean all the mill scale off, but the arcs were steady in both cases.

Any feedback? Thanks!!!

[Scott V]

Bill what size wire you running?It sure seems like you would be in the Globular state mess to me.I would back your voltage,and wire way down for what your welding.That way you might beable to see whats going on with the puddle,maybe your wire is buried in the puddle,and it's laying on top?

[BillC]

Originally posted by Scott V
Bill what size wire you running?It sure seems like you would be in the Globular state mess to me.I would back your voltage,and wire way down for what your welding.That way you might beable to see whats going on with the puddle,maybe your wire is buried in the puddle,and it's laying on top?

Sorry Scott,

It is .035 ER70-S6 wire. I was very careful to run these stringers with no whip or weave and doing my best to keep the arc in the root and ahead of the puddle...

[Dan]

Bill

Since you are in a school enviroment I will assume for now, until you tell me different, that the Millermatic 10A is a seperate feeder and Power source. If this is true and the power source has a voltage and amperage meter, take advantage of these features, and have someone else in the class assist you by tuning in the machine for you while you are welding. For short circuit transfer on the 1/8" steel you will want a load voltage of about 18 to 18.5 volts and the amperage to be somewhere between 125 to 145 amps. Exactly were these settings fall is going to depend alot on the joint design you are welding.

[BillC]

Thanks Dan,

Yes, the Millermatic 10A is the wirefeeder, and the Power source is Miller, but I can't remember the model. Big wheel on the right front face that you rotate to raise and lower the voltage, which you read off a pointer that moves vertically to the left of the wheel.

Anyway, it does have analog gages for voltage and current, so I will ask one of my classmates or my instructor to read these while I set up the machine tonight.

On a side note, it would appear from your suggested amperage range that 1/8 inch steel is really the limit for MIG on the 135 Amp class MIG machines.

Thanks again,

[Seldom]

You asked two questions here- "Is MIG really that unforgiving or am I just doing stupid things?"

The answer to the first part of your question is – ABSOLUTLY!
The answer to the second part is –NO, your just learning but don’t fall into the old trap that more heat is always better.
Nothing is better then skill!

[morpheus]

I've been there and done exactly what happened to you Bill.

It sounds like you're getting a molten puddle and then just continually feeding wire into the puddle. which I've proven that you can make it look like a good weld. this quote from Rocky a few months ago really turned the light on for me:

Originally posted by Rocky D
The secret to making a good MIG weld is recognizing that the penetration is accomplished only when the arc flame touches new metal...since the wire is adding filler all the time, adding to the puddle only piles up the filler on top of itself. To prove this, you can make a weld on a thick copper plate, then peel the weld off and look at your penetration. Where the arc touches, you will see a little groove.

once you realize that you're only getting penetration when the arc flame touches new metal and that the particular welding stroke you're using is to just backfill it all came together for me.

good luck Bill.

- jack

[BillC]

Originally posted by morpheus
I've been there and done exactly what happened to you Bill.

It sounds like you're getting a molten puddle and then just continually feeding wire into the puddle. which I've proven that you can make it look like a good weld. this quote from Rocky a few months ago really turned the light on for me:<<SNIP>>

Jack,
I remember Rocky's quote, and it turned on the lightbulb for me as well... In this case, I did not whip or weave, just a steady travel trying to keep the arc down in the root of the fillet and ahead of the puddle. I'll try more tonight...

Thanks for the input!

[BillC]

Originally posted by Seldom
You asked two questions here- "Is MIG really that unforgiving or am I just doing stupid things?"

The answer to the first part of your question is – ABSOLUTELY!
The answer to the second part is –NO, your just learning but don’t fall into the old trap that more heat is always better.
Nothing is better then skill!

Seldom,
As you have stated earlier, there are a lot of people out there who have purchased MIG machines because they are so "easy to use." Many of these people are blissfully modifying their trucks or building motorcycle frames or whatever. Hopefully most of them are smart like Jack and test their welds before building actual parts.

Regarding learning, you are correct. This is all part of my learning curve and I am sure that there is more problem with my technique than with the MIG process in general. I have to laugh... This is a four week mini-semester and I signed up for MIG thinking I could easily get a decent overview of the process in four weeks. All was going according to plan until I pulled out the hammer. The more I learn the less I know... But I do know that I will be continuing MIG when we come back in August...

[Dan]

Originally posted by BillC
Thanks Dan,

Yes, the Millermatic 10A is the wirefeeder, and the Power source is Miller, but I can't remember the model. Big wheel on the right front face that you rotate to raise and lower the voltage, which you read off a pointer that moves vertically to the left of the wheel.

Anyway, it does have analog gages for voltage and current, so I will ask one of my classmates or my instructor to read these while I set up the machine tonight.

On a side note, it would appear from your suggested amperage range that 1/8 inch steel is really the limit for MIG on the 135 Amp class MIG machines.

Thanks again,

Bill

I ve welded with several set ups like you are describing so, I know exactly what you are describing.

The sad part about this is if your instructor(s) was actually a good teacher he or she would have already had you and your classmates setting the machines to an approximate setting by using the meters and then adjusting the machine with in this established voltage and amperage range until you achieve the proper results. When I went to school ( 15 years ago) my instructors gave us an established voltage and amperage range to work in on each material thickness, and we had a lab partner who helped tune the machine in.

Since the first day that I started posting on this site I have always stated that with a solid wire and shielding gas 1/8" is the maximum thickness that should be welded with a 135 amp MIG machine. This was even during the time when the manufactures of these 135 amp machine were rating them for 3/16" with a solid wire. These 135 amp machine are actually even borderline for 1/8", because at there 125 to 135 output amperage range they are only capable of out putting around 17 to 16.5 volt. Due this low output voltage capability on these machine you have to incorporate a weave into your travel or the risk of cold lapping is going to greatly increase.

Ideally, the 135 amp machine MIG aren t the best choice to use for welding thicker then 1/8" with fluxcore wire too.

[Planet X]

Being 'home-schooled' in the Mig process I would like to direct your attention to this book Manual and Robotic Gas Metal Arc Welding including Pulsed GMAW Weld Process Training Weld Process Control by Ed Craig It will be the best $80 you will ever spend on your welding education. Oh yes and go out and get yourself a fillet gauge so you don't have to break the 'over-welding' habit.

[river1]

what is a fillet gauge and where would someone get one?

thanks jim

[Dan]

Bill

the statement of Rocky's that Jack quoted is the exact reason why I ve always used some type of oscillation (mostly a side to side weave) on 1/8" - 1/4" with the short circuit transfer mode.

A guy at my work built a guard rail out of 1 1/2"X1 1/2"X.120 wall SQ tube using the exact same short circuit transfer settings that I use. However when a forklift accidently clipped the rail almost every weld failed. Everyone of these welds only had little areas were there was actually any fusion into the basemetal. Now after this, I was assigned to rebuild the rail from the exact same size tubing. So, I built the rail installed it, and about a month later a forklift hit the rail again. This time however not a single weld joint fail. However what did happen was quite amazing, and gained me alot of respect for the quality of weld that I can produce. The forklift hit the rail so hard that it actually sheared a section of the 1 1/2" sq tube. As hard as the forklift had to hit the rail to do this I was very pleased that not a single one of my welds showed any sign of failing. Anyway the reason I told this story was because the guy that built the first rail was assigned as my helper for building the second rail so that I could teach him. On the .120 wall tube he was traveling straight along, like you stated you were, letting the weld puddle develope. Almost ever weld that we broke of his had very little fusion. So, I showed him how I actually use a slight side to side weave. When we tried to break my welds, the wall of the square tube actual broke at the toe of the fillet instead. Anyway, this guy started using the slight side to side weave motion that I use, and it wasn t long before his weld joints were holding up as good as mine.


By the way, for short arcing on the 1/4" mild steel at school give some where around 19 load volts and 160 to 170 amps a try. Try using a side to side weave and do your best to stay on the leading edge of the weld puddle. For now too I would just focus on pushing the weld puddle that way you can see how things are developing.

[chip hayden]

this discussion reminds me of what i did for a class demonstration when the first 110V wire machines hit the market.
with a small group of students i would run a stringer bead on a piece of 1/4 hot-rolled plate around an 1 1/2" long. i would then have the students lift their hoods and ask them how the weld looked. obviously, because i was the teacher and they didn't have that much experience, they would tell me how good it looked. what they didn't know was that i had "reversed" the leads so i was welding solid wire with straight polarity.
well, after they were duly impressed with my "expert weld", i would take my thumbnail and 9 times out of 10 lift that stringer bead right off the plate and hand it to them to prove the quality of my weld. looks can be deceiving.

[Seldom]

My hats off to Dan and Chip!
Two great examples of helping folks become aware of mig-SC limitations. I guarantee Dan’s example raised the level of awareness of everybody on the shop floor and Chip’s dramatic demo had a greater impact and value to those students then a whole bunch of hours in the booths.

River1
Since Planet-X hasn’t come back on yet-
As far as fillet gauges are concerned, just ask for them down at your welding supply store. You won’t have to spend a lot of money and they’ll show you how they work.