Where does the received wisdom that MIG is inferior to Arc for welding thick material come from?

[Ed.]

I suppose it all depends on the welding experience you have had, the equipment you have access to, the type of work you need to weld up and where you are going to weld. I own ARC, TIG and MIG, the majority of my welding is with MIG, which I can weld using 0.6mm wire up to 1.2mm and even 1.6mm wire however I have never had a reason to use that last thickness.I generally use 0.9mm unless the metal is either thin or thicker, Never had trouble with penetration using MIG. I regularly used to weld from 2mm up to 20mmm and choose MIG, under 2mm thick steel I use 0.6mm wire) MIG, it is much faster to tack and weld a job, with less cleanup. You also need to factor in the cost/rental of the right type of gas and gas bottle, a ARC welder is also much cheaper than an equivalent sized MIG to buy.

For home use, most homes do not have more than a 10amp GPO for electricity so very limited in the type of welder you can choose and get weld amps and voltage out of. So most are limited to 130 to 160amps? In that range an ARC welder would be better as you can use 1.6mm electrodes (if you can find them) 2.3, 3.2 ( and 4mm rods which can be used for thicker steel however your 10A amp MCB will trip after a minute or two). Similar results with MIG but on a 10A circuit you will have to watch the duty cycle on both types, an equivalent sized MIG welder will give similar results if you know what you are doing, a pretty weld does not mean it is a strong weld with good penetration.

Having said all, that I can pick up my single phase 180A inverter ARC welder with one hand where as the MIG is 3 phase and with bottle and trolley weighs close to 250-300Kg. So at the end of the day you need to use the right machine/process for the job at hand. Most Factories will use MIG for most of their welding jobs right up to welding 100mm thick steel, I won't be getting into dual shield, submerged arc and all the other tech available.

 

[Dozzer]

From my limited experience over the years in construction equipment, when we were building 25T dump trucks in a factory and welding up the skip bodies 10-12mm 400 series hardox, it was bloody great 3ph mig machines, 12 -16ft run would use a stupid number of rods, out in the field with a geny set repairing = rods.
Neither is any better, they are just better suited to different applications, and with some of the tiny Inverter IGBT units now, you can get some serious mig power in a very small package

 

[Erie Fred]

I have worked in a shop where they run gas shielded flux core at IIRC .052 wire. 650 amp machines turned all the way up.

On a good day, the operator is going thru qty (3) 50lb rolls in an 8 hour shift.
They started using the 1000lb cardboard drums to alleviate the ergonomics of lifting those reels up to the feeder.

 

[Robotstar5]

I have worked in a shop where they run gas shielded flux core at IIRC .052 wire. 650 amp machines turned all the way up.

On a good day, the operator is going thru qty (3) 50lb rolls in an 8 hour shift.
They started using the 1000lb cardboard drums to alleviate the ergonomics of lifting those reels up to the feeder.

We knew them as Marathon or bulk packs and had them on our production welders, both manual and robotic.

The Yellow things in this pic.

The wire came through a flexible conduit to a quick connector on the wire feeder.

 

[Memmeddu]

You are missing context.

The statement, by itself, is rubbish.

If you have a 130A "MIG" and a 130A ARC welder, the arc welder will likely be better for anything thicker that 3mm. Most "MIG" is done using short circuit transfer, a cold process, so it will not be good on thick material. That is generally where those statements come from.

Flux core is often better (on thicker material) - particularly with out of position work and, if using FCAW-S, out in the open.

"Better" can only be applied if the complete context is known.

Jack

That's the point
An arc welder might be more cost effective for most application.
It's as simple as a welder can be.
You just have a simple generator which is the welder itself, workpiece lead and clamp, electrode holder and lead, electrodes.
Almost wind proof
With a mig welder you have a complex generator, a wire feeder, drive rollers, workpiece lead, a mig gun, which needs contact tips, gas cup, protective shroud which projects the gas, a gas bottle and regulator to supply the shielding gas, then you have your welding wire.

Both have advantages and disadvantages and they have their specific place.
I started with arc, I still love to stick weld stuff together.
With a 200A stick welder you can do practically everything you need above 2mm material thickness.
It's slower than mig as you have to swap electrodes, and remove slag, the deposit rate is lower than mig.
For most fabrication is the only welder you need, a friend of mine and many others build their lives around a stick welder.
But if you have to do production you cannot beat wire feed welding, problem is that amps and material thickness are directly proportional.
You can stick weld very thick stuff just running beads after beads even if you have just a 160A arc welder.
You'll won't be able to achieve the right penetration with a 160A mig let's say passing over 6mm, you'll be just laying metal over metal without correctly mixing the weld with the parents metal.
You'll likely need 220 Amps to really weld 10mm stuff from my experience.
2.5mm E7018 two or three passes you'll get a way better weld on 10mm material with just 90ish amps.
I agree there's not the best process...
But a better one for the application.
Don't ask me to mig weld aluminum that's for Tig, don't ask me to mig weld a fence in a open field that's for stick.
Don't ask me to stick weld body panels that's for mig.
Don't ask me to mig weld an excavator bucket with a 150A machine I'll do with stick.
It's not that easy to get to the point I hope I've been able to explain my point of view

 

[Jelly_Sheffield]

That's the point
An arc welder might be more cost effective for most application.

If you already have an arc welder sure.

If you're buying a new welder, then the price of decent 200A arc welder is about the same as the price difference between a 180A and 300A MIG/Multiprocess unit from one of the new generation of cheap but good far eastern manufacturers...

Just the three questions "how big is each weldment?", "how easy is it to access the work area?", and "how often do I do similar types of work?" give enough scenarios in which there's multiple "right" answers to which process is more cost effective for a given user, that I don't think it's possible to generalise what's cost effective for most scenarios.

It's as simple as a welder can be.

You could say the same about Oxy-Fuel, it has the same beautiful simplicity and broad applicability as Arc (much broader than Arc in fact), and doesn't need any power source...

But it's slow, and relatively mentally and physically taxing, compared to just about everything else.

So as technology marches on, it's increasingly been confined to niche applications.

Both have advantages and disadvantages and they have their specific place.

Which is exactly why I find it kinda puzzling that this "Trueism" still gets repeated so frequently...

Especially as very capable mid-level output MIG units are increasing affordable even to a hobbyist, and FCAW rarely if ever gets a mention in these contexts, despite being kinda the best of both worlds for many applications.

 

[leadpig]

Pfffft every one knows tig is where it's at

 

[Jelly_Sheffield]

Pfffft every one knows tig is where it's at

Show Off!

Get out of here with your high skill, high quality, aesthetically pleasing welds, with minimal HAZ and oxidation, even in difficult/thin substrates.

(Whilst technically possible to do just about everything TIG is good at in some other way, it's generally difficult to suggest that those ways are a comparable or better alternative to it.)

 

[Memmeddu]

If you already have an arc welder sure.

If you're buying a new welder, then the price of decent 200A arc welder is about the same as the price difference between a 180A and 300A MIG/Multiprocess unit from one of the new generation of cheap but good far eastern manufacturers...

Yes without a doubt...
If you are going to buy a new welder and you don't own one yet, a multi mig/stick welder can be the best solution.
I started with a buzz box, after maybe 4 years, I've got my engine driven, and few months later I've got my inverter stick.
It's only 6 years later I really need a mig welder so I've got a little 140A mig/stick.
Going back I'd get a 200A machine

Just the three questions "how big is each weldment?", "how easy is it to access the work area?", and "how often do I do similar types of work?" give enough scenarios in which there's multiple "right" answers to which process is more cost effective for a given user, that I don't think it's possible to generalise what's cost effective for most scenarios.

Which should be the rule prior to buy everything really .

You could say the same about Oxy-Fuel, it has the same beautiful simplicity and broad applicability as Arc (much broader than Arc in fact), and doesn't need any power source...

Which is why I'm getting set up for that, but it's really expensive in first place, plus the gasses.
There's a lot of money involved
If I didn't find my used torch set cheap...
It would have been more than 2000 euro to get the same equipment.
Which it's enough money to get a brand new professional welder of any type.

But it's slow, and relatively mentally and physically taxing, compared to just about everything else.

So as technology marches on, it's increasingly been confined to niche applications.


Which is exactly why I find it kinda puzzling that this "Trueism" still gets repeated so frequently...

Completely agree with that

Especially as very capable mid-level output MIG units are increasing affordable even to a hobbyist, and FCAW rarely if ever gets a mention in these contexts, despite being kinda the best of both worlds for many applications.

Not exactly it has its place.
I love FCAW but you won't get great results for cheap either with that.

 

[Jelly_Sheffield]

Which is why I'm getting set up for that, but it's really expensive in first place, plus the gasses.
There's a lot of money involved
If I didn't find my used torch set cheap...
It would have been more than 2000 euro to get the same equipment.

Ouch, that's significantly more expensive than I would have anticipated.

If I walked into my local BOC tomorrow it would be about €900 for a complete outfit, and they're expensive!

Ordering online the equivalent gear (buying individual items) would come out around €400.

Not exactly it has its place.
I love FCAW but you won't get great results for cheap either with that.

I would expect a decent MIG unit to be capable of running FCAW effectively.

The big issue with FCAW-S is that there's a lot of additional complexity of finding a good wire for the application, or trying to find a default wire that will cover the whole range of possible applications you need.

In the context of this post, there's a specific challenge as sheath thickness can have a significant influence on penetration, but isn't a specified parameter in any of the nomenclature systems for wire.

 

[Memmeddu]

Ouch, that's significantly more expensive than I would have anticipated.

If I walked into my local BOC tomorrow it would be about €900 for a complete outfit, and they're expensive!

Ordering online the equivalent gear (buying individual items) would come out around €400.

Here's my torch set up
Harris 43-2 handle €330
Harris 49-3 cutting attachment €385
Harris E43 mixer and tips €100x6
Harris 6290NX tips €10x5 covering all the range
Harris flashback arrestors €20x4
Fitting adapters 9/16 to 3/8 €18x2
Twin 8x18mm hose 10 meters long €50 roughly
Harris 801-D oxygen regulator €75
Harris 801 propane regulator €65
Harris 801-B acetylene regulator €80
Oxygen bottle (customer property) €200
Albee bottle already €300 for the caution and rent contract over here let's double it because you need acetylene too
Propane tank €25
I went for the propane route as I don't need it for welding.
Total is 1900 euro for my set up, which goes up to 2400 if we add acetylene bottle and regulator
Trolley cart has not been taken in consideration
As well as a propane rosebud (200+ euro alone)

I would expect a decent MIG unit to be capable of running FCAW effectively.

A decent mig is expensive

The big issue with FCAW-S is that there's a lot of additional complexity of finding a good wire for the application, or trying to find a default wire that will cover the whole range of possible applications you need.

There's an aws chart for that, problem is that you won't find what you need sold locally

In the context of this post, there's a specific challenge as sheath thickness can have a significant influence on penetration,

Which is the main problem with both mig and Tig

but isn't a specified parameter in any of the nomenclature systems for wire.

Aws flux core wire chart, ideally E71T-GS, E71T-11, E71T-8, and E71-T1 are the only ones you ever need
Problem is that I couldn't never find E71T-8 wire over here