Abstract: A built-up camshaft has cam discs which are secured to a tube under mechanical prestress, are of annular design, and are inductively hardened all the way around at a boundary layer on their outer periphery before they are secured to the tube. The hardening of the boundary layer is formed in such a manner that, due to the hardening, high residual compressive stresses (at least -450 N/mm.sup.2) are produced in an at least approximately 0.5 mm deep boundary zone near the surface in such a manner that, even after the cam discs are mounted on the tube, the superimposing residual tensile stresses in the boundary zone, induced by the joining, only partly compensate the original residual compressive stresses, i.e. there are still only residual compressive stresses (at least -150 N/mm.sup.2) in the boundary zone near the surface even after the pressing-on. Sufficiently high residual compressive stress in the boundary zone can be produced by effecting the inductive heating of the cam disc in two stages.

Abstract: A built-up camshaft has cam discs which are secured to a tube under mechanical prestress, are of annular design, and are inductively hardened all the way around at a boundary layer on their outer periphery before they are secured to the tube. The hardening of the boundary layer is formed such that, due to the hardening, high residual compressive stresses (at least -450 N/mm.sup.2) are produced in an at least approximately 0.5 mm deep boundary zone near the surface such that, even after the cam discs are mounted on the tube, the superimposing residual tensile stresses in the boundary zone, induced by the joining, only partly compensate the original residual compressive stresses, i.e. there are still only residual compressive stresses (at least -150 N/mm.sup.2) in the boundary zone near the surface. Sufficiently high residual compressive stress in the boundary zone are produced by effecting the inductive heating of the cam disc in two stages.