Method and apparatus for inductively heating valve seat inserts

Abstract

A method and apparatus for heating a conical valve seat surface of a valve seat ring insert which has been previously press fitted or molded into an engine component such as an engine head. The method and apparatus includes mounting an inductor for reciprocal movement axially toward and away from the valve seat of the engine head and biasing the inductor toward the valve seat, encircling the inductor with an axially biased electrically conducting hollow ring-shaped magnetic flux shield through which a coolant is circulated, and moving the inductor and conducting ring shield toward the valve seat of the engine head to locate the inductor in a preselected position providing the necessary magnetic coupling gap between the inductor and valve seat surface of the valve seat insert while the conducting ring shield is maintained in heat transfer surface contact with and stray flux shielding relation to the portion of the engine head immediately around the valve seat surface of the insert. Energization of the inductor results in inductive heating of the valve seat surface of the insert preparatory to the quench hardening thereof. During the inductive heating of the insert, the cooled conductive ring shield acts to prevent excessive heating, by induction and by heat conduction from the heated insert, of the aluminum metal of the engine head around the valve seat insert such as would normally destroy the pressure fit therebetween and damage the surrounding aluminum metal.