It doesn't look so much torn as cracked all the way around. It has to do with the dissimilar metals. Many suppliers of wedges recommend welding with a low hydrogen rod. (I think 7018 is a low hydrogen rod) Or maybe preheating and cooling slowly.
There are a lot of welding experts on here and I am sure they will give good advice but you could also check out
WeldingWeb™ - Professional Welding Forum - Powered by vBulletin they are a lot like this website, good people, good advice.