That's a 'NO'. Sorry,
JasonJas . ANy weld repair will not be as strong as the original, which was already not strong enough.
THis was likely caused by a too-short seatpost, though. Seatposts have a 'minimum insertion' mark, but I am never sure if the seatpost is designed for the mark to be at the top of an unsupported extension on top of the seat tube, or if it is better to make sure the mark is down near the tube junction where there is support.