The invention relates to a process for the continuous heat treatment of steel strip material whose thickness d1, d2 periodically varies along its length, more particularly of strip flexibly rolled with a roll gap varying as a function of time, wherein the continuous heat treatment of the strip material takes place while the strip material passes through an induction furnace in which the strip material is induction heated at a constant frequency which can be selected to be such that the mathematical induction depth δ of the induced current up to which the magnetic field has been reduced to 63% of the field strength of the outer field is greater than half the thickness of the strip portions with the smallest thickness d2.