Apparatus and method for inductively heating metallic tubing having an upset portion

摘要

There is disclosed herein apparatus and method for heating metallic tubing having a thickened portion, by passing the same through an induction heater energized with power at a relatively high frequency whereby the temperature of the body of the tubing rises at a faster rate than the temperature of the said thickened portion and passing the said tubing through an induction heater energized with power at a relatively low frequency to cause the temperature of said thickened portion of the tubing to rise at a faster rate than the temperature of the body of the tubing, the ratio of the power applied at said low frequency relative to the power applied at said high frequency being such that said body and said thickened portion attain substantially the same predetermined final temperature upon exiting from said apparatus.