Hello all
I was left conjecturing of this point...
For "heavy" structural sections - take example of H-column of web-and-flange thickness of 20mm (3/4inch) - welded around the periphery to an end-plate of similar thickness by a "small" fillet of
8mm (5/16inch)...
These are done with the section horizontal on trestles / a bench, with section rolled between runs so the weld is always horizontal-vertical.
For a MIG weld the runs will be short and quite a lot of the run will be "cold" before the weld settles into the good run condition on which the weld was selected. Given the heat-sink of the thick plate... What about using a welding condition with more power - a condition which would be giving toe-groove ("undercut") if the weld were a long run? Particularly by aiming higher on the voltage (though not enough to make the spray-cone long and unfocused)
The starting couple of inches is not going to have toe-groove... If toe-groove starts, it's going to be taking something like 0.25mm (about 10thou) out of 20mm (3/4inch) - in a region where stresses are low, at beam and column ends...
What you are mitigating is the risk of the far more serious condition of lack-of-fusion.
Codes allow some toe-groove (undercut)...
Well, this is what I was thinking about. Any comments?
Rich