malefacter:
Your post did not specify what type of "torch" you used, so consider the following. According to information which I found via a quick search of the Internet, the temperature of embers in a fireplace (one of the methods which Richard Carleton Hacker recommended - reference trailboss' post above) may range from 1,200 to 1,500-degrees Fahrenheit, and that of a butane/air mixture flame (via a butane lighter - another method which Mr. Hacker recommended) is estimated from 1,472 to 1,652-degrees Fahrenheit. The temperature of an oxygen/acetylene flame averages 5,972-degrees Fahrenheit. Given the drastic differences in temperatures between the first two and the last, then assuming that you used the last, it is small wonder that your pipe disintegrated.