I'm welding a four inch solid shaft from an 18-wheeler hub to a half inch mild steel plate. There is a hole in the plate, and it's a butt weld around. This thing lasts about two months before the cracks are visible again. It keeps breaking at the interface with the steel plate. I'm welding it with 7018, preheating it to death, etc. My vote is that the geometry of the joint is causing the cracks to start as soon as the material starts to cool and has no place to loose tension. It's obviously not lamilinear tearing because the stress is in the direction of the grain in the plate. Anyway, is there any good info on contrained joints on the net? I know pipe flanges are welded all the time all day long without cracking, and its a very similar joint. Any ideas?