You can likely get the ends lined up and then drill a hole (both ends) which accepts a small machine bolt and nut. If you have trouble re-rolling the pipe, here’s a suggestion: Get a section of schedule 40 pipe about 2.5” diameter and use it as a mandrel to roll the pipe around It helps to have a couple extra people when you do this. Lay out your stove pipe and place the s-40 on it. Line things up to get a straight edge and straight roll. Roll the stove pipe and s-40 pipe as a unit being careful to keep a grip and prevent misalignment. Once rolled you can carefully slip the rings down over the pipe and then let the pipe expand to full diameter. You’ll have to go easy to be sure the pipe stays straight and doesn’t do the spiral. If it refuses to stay straight you can drill the ends and insert a machine bolt. Otherwise, go ahead and burn the stove/pipe again to reset things. Burn it pretty hot once, then flip the pipe and repeat.