First of all, I Love Short Circuit MIG But... Hear me out.
The problem with short circuit mig is not the process itself but that there is nothing stopping a person from using cold settings just for the sake of a prettier weld.
Spray transfer mig requires a minimum of around 24 volts along with an argon rich mix.
Once you achieve a true spray arc, lack of penetration is unlikely.
But unlike Spray transfer , Short circuit mig does not have a distinct minimum setting that ensures penetration. So the welder can chose to use very low settings.
That can actually be a benefit and it is why short circuit mig is used on very thin metal like auto body panels, and also works on up to around 3/8" thickness and can also be used in all positions.
I think the reason short circuit mig has a reputation for cold lap and lack of fusion is not so much the process as it is welders using cold settings just for the sake of a pretty weld.
Here is a quick story about cold settings.
When I worked in an aerospace welding shop at Delta TechOps. I also did quite a bit of mig welding.
It was an aircraft engine parts welding shop, but there was a dedicated area for MIG welding fabricating fixtures, stands, carts, shelves etc.
There were even two engine parts that got mig welded using a stationary mig torch and a turntable. ( thats a story for a different blog post)
A division of the machine shop called the tooling department routinely made round fixtures that were used to align, expand, and prevent distortion on round engine parts.
This tooling department.would get the ground equipment shop to flame cut donut rings out of one inch thick steel and then finish machine these rings to dimension to make these round fixtures for engine parts.
One day one of the machinists from the tooling department dropped by and asked me to weld 4 one inch thick by 24 inch diameter rings together because they weren’t able to get 4 inch thick rings cut.
They had 4 donut rings all chamfered and ready to weld but I knew they had a welder in their shop so I wondered why they didn’t just get him to weld it...and I asked about that.
Lets call the welder “John” so as not to belittle anyone.
Their answer kind of floored me.
“Whenever John welds something like this where the weld is machined off, we can peel off the rest of the weld with a can opener”
John could run the prettiest MIG bead you ever saw.
But he welded cold.
And that is one of the main problems with short circuit mig.
Adjusting the settings just for looks instead of for penetration.
These rings were one inch thick my setup was short circuit mig with 75/25 argon/co2 but I also knew that if I used settings that were good and hot, there would be no problem with machining by welds.
So I clamped the parts to a turntable and set the stationary mig torch to where I was welding slightly uphill with a 90 degree torch angle.
After I preheated to around 300F with a rosebud, I tacked each joint and then ground all the tacks smooth.
I knew I was pushing the limits of short circuit mig so I set the big Hobart machine to 23-24 volts and around 450-500 inches per minute of wire speed using .035” ER70S-6.
Those settings are in the maximum range for short arc mig but I got both voltage and wire speed balanced to where there was only a small bit of spatter and pretty smooth arc. Welding at a slight uphill angle helped a lot too and I could see the front edge of the puddle biting in.
It took several passes to fill each bevel and to add enough reinforcement so that the ring could be final machined to dimension without any low spots.
Anyway, the lesson I took away from that job was to always strive first for a sound weld with good penetration and to never use COLD short circuit MIG settings just for the sake of appearance.
Remember...A pretty weld is not always a good weld
Learn more about the affordable MIG welder package ...click here or image below
