007 has a good solution:
Sawzall blades are flexible and you can cut the pipe by allowing the blade to skim the floor surface. You will however mark the floor permanently. Once the steel is cut all around the concrete inside will break off at the floor level or pretty close to it. You will still have the steel ring remaining but that shouldn't be a big deal. If the floor surface then has a pock in the concrete inside the pipe after the pipe is remove that little bit of damage is easy enough to fix.
If you cut the pipe exactly at the floor surface there shouldn't be anything to fix except a little missing concrete inside the pipe.