Abstract: A scanning induction hardening process in which a steel workpiece is surface hardened by progressively traversing its length with an inductor coil energized by an alternating electric current and immediately thereafter quenching the heated portion of the workpiece characterized in that straightening of bends in the workpiece being surface hardened is controlled during the induction hardening process by monitoring the straightness of the workpiece and utilizing information thereby obtained to control the heating and quenching of the workpiece in such a manner that a layer of hardened material of greater thickness is formed on the concave side of any bend in the workpiece such as to produce a straightening moment acting to remove the bend.