Welds can be stronger than the original steel, but it needs to be a world-class weld. As stated by others, such an inexpensive part should just be replaced.
The strut rod is tempered steel. Once you get it hot by welding it...it will lose its temper. Yes it could be done by a top notch professional but the price it would cost to pay a real professional and have the part re-tempered you will come out hundred dollars cheaper buying a new strut rod.
Don't worry guys. I already have one boxed up to go out to him tomorrow, along with the window regulator he has been looking for.
