Process for hardening the edge portion of a recess in a metallic article using induction heating, and locally hardened twist beam axle obtained by this process

摘要

A motor vehicle steering wheel shaft (1) has a tubular steel construction with a recess (2) formed by depressing the tube wall to create a double wall recess the edges (3) and throats (8) of which are induction heated by means of coils arranged on the inside and outside of these areas.