45 and later seat posts are welded at the top, and bottom of the casting. They are a lot easier to remove than the earlier seat posts, which are sweated in. On later frames, all you have to do is sand through the weld until you start seeing the two different metals, you can see the separation in the upper left hand corner. Sand the welds until you can see the separation all the way around the outer diameter of the seat post on the top and bottom.
Then you can knock the tube out with a hammer and punch.
I used a pipe cutter to mark a line around the circumference of the seat post, this is where I will cut the old damaged post out. This gives me a good reference point to go off of.