You see the weld right next to the break? That is what is called the heat affected zone of the weld. The break could be caused by the metal being bad, if the beam was torch cut so it could be bent then it could be carbon that wasnt cleaned/ground out before it was welded. Depends on the material but if it is chromoly it probably should have been stress relieved. I could list several other things but they would all be guesses. The only way to know for sure is to send it to a metalurgist to be analyzed. Also just so you know I have been a certified welder for over 30 years and have seen lots of cracks/breaks in different kinds of metals and there is always a reason why.Johnny
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