JPS6475629A - Method for hardening inside and outside peripheral surface of small-bore cylindrical body - Google Patents

Abstract

PURPOSE:To form desired quench hardened layers on the inside and outside peripheral faces of a small-bore cylindrical body while assuring toughness in the core part of the cylindrical body by forming the quench hardened layer over the entire section of the cylindrical wall of said cylindrical body, then subjecting the outside peripheral face to high-frequency heating and rapid cooling while subjecting the entire inside peripheral wall to controlled cooling. CONSTITUTION:The entire section of the cylindrical wall of the small-bore cylindrical body W is heated by using a suitable heating means and is rapidly cooled to form the quench hardened layer H thereon. A cooling jacket J bored with many cooling fluid injection holes S is then disposed in the cylindrical body W and the cooling fluid of the controlled flow rate is supplied from a pipeline P to the jacket to cool the entire inside peripheral wall of the cylindrical body W. A heating coil C having a heating conductor part (c) and a jacket part (j) for hardening is simultaneously moved in an arrow direction relatively with the cylindrical body W. The above-mentioned heating conductor part (c) is connected to a power supply E for high-frequency heating. The cooling fluid of the controlled flow rate is injected from the above-mentioned cooling jacket part (j) to rapidly cool the cylindrical body at the point of the time when the outside peripheral face of the cylindrical body W is heated to the prescribed hardening temp. The quench hardened layers H, h of the desired depth are thereby formed on the inside and outside peripheral faces of the cylindrical body W with the softened and tempered structure R held in-between.