Why does mig welding downhill prompt so many arguments?
Can you tell a weld is good just by looking at it?
When it comes to MIG, How clean is clean enough?
This video answers a few of these questions and probably prompts even more questions about mig welding downhill and when uphill is better.
The first joints I welded in this video were cold rolled finish and roughly 1/8" (3.2mm) thick.
I used the Hobart recommended settings for .024" (.6mm) wire.
One joint test ok, but on a second joint ...using a slightly different gun angle and technique, the results were not that great.
Just to demonstrate that a visually acceptable weld can be a cold weld with plenty of lack of fusion, I used the same settings as I used for the 11 ga (3.2mm) thick cold rolled steel.
I purposefully hung back in the puddle so that the arc would not reach the root.
Just as suspected, the root of the joint had considerable lack of fusion when I tested the weld by cutting, polishing, and etching.
Switching to a heavier machine with .035" (.9mm) wire, I expected better results.
But in fact, the test revealed severe lack of fusion due to the thick mill scale coating.
In fact, the hotter settings yielded a weld worse than the one using small diameter wire and lower amperage.
I suspect cleaning the mill scale would have helped a lot.
But I didn't clean the metal at all because I wanted to show real world conditions welders are up against.
This objective of this video is not to say all downhill mig is bad.
But rather just to show a few things like...
My rule of thumb is to weld uphill on 1/4" (6.2mm) and thicker.
I have built lots of metal racks, shelves, and fixtures using hot rolled angle.
Did I clean the hot rolled mill scale from every joint before welding?
But I also once welded a manlift work trolley using Mig.
You better believe I ground that clean and welded it hot.
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