Method for inductively heat treating workpiece bore walls

Abstract

A method and apparatus of quench hardening to a desired depth the full axial extent of the wall surface, or selected portions of the wall surface, of an axially extending bore in an elongated workpiece wherein the bore has a selected uniform cross-sectional shape throughout the length thereof and is closed at one end, which method and apparatus involves providing an inductor with an outer shape generally matching but smaller than the cross-sectional shape of the bore to permit passage of the inductor through the bore, supporting the workpiece with the axis of the bore extending vertically and the open end facing downward, electrically energizing the inductor with a known frequency and at a selected power level, passing the energized inductor upwardly through the bore to inductively heat the wall surface of the bore progressively upwardly from the lower end thereof while progressively liquid quenching the wall surface immediately below the inductor during the upward passage thereof through the bore, and directing additional liquid quenching medium from the top of the inductor for impingement against the innermost end regions of the wall surface of the bore, at the limit of the upward passage of the inductor into the bore, to quench the innermost end regions of the bore wall surface above the reach of the progressive liquid quenching of such wall surface below the inductor when located in its limiting upward position in the bore.