METHOD OF ELECTROMECHANICAL MANDRELLING Russian patent published in 2016 - IPC B24B39/02 

FIELD: metallurgy.

SUBSTANCE: mandrel bar is moved along hole axis, and on the hole surface the strengthened ring areas with different hardness are formed by heating of the said ring areas to hardening temperature with simultaneous passing of the electric current through the contact place between the mandrel bar and hole surface. The mandrel bar is moved relatively to the treated hole of the part from bottom part of hole to the top part with negative allowance, and carbonisation and cooling of the hardened ring areas are performed.

EFFECT: higher wear resistance of part.