This is what sprung my door out. While making the first cut along the top of the CC, there was a loud pop and the seam opened up a bit. I welded hinges across the cut (while the other 3 sides remain uncut) but the door still sprung out of round. That is, the curvature of the door did not match the curvature of the pipe. The pipe was made in Korea.mp4 wrote:Heat is one factor - the other is the process of rolling the original barrel. It may have had to be squeezed together to weld it up from the factory and then springs open as soon as it is cut open.