On a welding socket of a pressure vessel of a compressor, a cast bridge had broken off exactly at the end of the socket. The rest of the outer thread of the cast bridge was thus stuck in the inner thread of the welding socket without any possibility of applying tools on the outside or a step wrench on the inside. An expensive extractor just for this application didn’t seem to make sense to me.
Insert a few sufficiently long wood screws into the broken threaded pipe. Then screw in more screws so that the screws clamp tightly to the rest of the pipe. Now you can apply a water pump pliers or pipe wrench to the screwed-in screws and remove the broken off rest. The same technique works for broken threaded fittings. It may still help to take advantage of the thermal expansion and heat the internal thread