When a design calls out for a tab to be inserted into a slot and then welded over, what type of joint would this be considered? Is it a prequalified joint? What kind of weld symbol would be appropriated?
Assuming the tab is flush with the outside surface of the slot, I would classify it as a square groove. Two arrows would be required to weld both sides of the slot on the outside surface or you could use the all around symbol.
You didn't provide all the details; we can't provide the complete answer to your quandary. Partial details - partial answer.
If that's the case, which I am ok with, at what point would it go from a tab/slot to a plug weld? If the tab only came up through about half-way would it still be the same joint?