Heat treating device and heat treating method
A heat treatment apparatus 10 comprises a supporting unit 20 for supporting a columnar workpiece 12 turnably, and an induction-heating coil 30 for induction-heating the workpiece 12 supported turnably by the supporting unit 20 . Below the workpiece 12 supported by the supporting unit 20 , a cooling tank 50 is provided which contains a liquid coolant. The workpiece 12 is made of steel such as carbon steel for mechanical structure, and spring steel. The workpiece 12 is made of a material which has a magnetic transformation point at 770° C. The material is ferromagnetic below this temperature, and becomes paramagnetic above this temperature.
1. A heat treatment method for a workpiece, comprising supporting the workpiece turnably around a turning axis, induction-heating a belt zone, extending parallel to the turning axis, of the workpiece by bringing an induction-heating coil near to the belt zone,
allowing the workpiece to turn by a magnetic force, when the belt zone has been heated above a predetermined temperature, to bring another portion other than the belt zone near to the induction coil, and
induction-heating the portion.
2. A heat treatment method for a columnar workpiece, comprising supporting the columnar workpiece turnably in a periphery direction,
induction-heating a belt zone, extending in a height direction, of the columnar workpiece by bringing an induction-heating coil near to the belt zone,
allowing the columnar workpiece to turn by a magnetic force, when the belt zone has been heated above a predetermined temperature, to bring another portion other than the belt zone near to the induction coil, and
induction-heating the portion.
3. A heat treatment method for a tubular workpiece, comprising supporting the tubular workpiece to be turnable in a periphery direction of the tubular workpiece by a rod-shaped supporting means inserted into a hollow of the workpiece, induction-heating a belt zone, extending parallel to the supporting means, of the peripheral face of the tubular workpiece by bringing an induction-heating coil near to the belt zone, allowing the tubular workpiece to turn by a magnetic force, when the belt zone has been heated above a predetermined temperature to bring a portion other than the belt zone near to the induction coil, and
induction-heating the portion.
4. A heat treatment method for a helix member, comprising
supporting the helix member turnably in a direction of the periphery thereof by a ceramic supporting rod inserted into a hollow of the helix member formed from a material which is transformed from ferromagnetic to paramagnetic by temperature elevation above the magnetic transformation point,
induction-heating opposed portions of the peripheral face of the helix member, supported by the supporting rod on the both sides of the supporting rod, by bringing an induction-heating coil near to the opposed portions,
allowing the helix member to turn by a magnetic force, when the belt zone has been heated above a predetermined temperature, to bring portions other than the opposed portions near to the induction coil, and
induction-heating the portions.
5. The heat treatment method according to claim 4 , wherein the helix member is allowed to fall, when the helix member has heated up to a predetermined hardening temperature, into a cooling tank containing a coolant by pulling the supporting rod out of the hollow portion of the helix member.
6. A heat treatment method for a coil spring, comprising supporting the coil spring turnably in a direction of the periphery thereof by a ceramic supporting rod inserted into a hollow of the coil spring formed from a material which is transformed from ferromagnetic to paramagnetic by temperature elevation above the magnetic transformation point,
induction-heating opposed portions of the peripheral face of the coil spring, supported by the supporting rod on the both sides of the supporting rod, by bringing an induction-heating coil near to the opposed portions,
allowing the coil spring to turn by a magnetic force, when the belt zone has been heated above a predetermined temperature, to bring portions other than the opposed portions near to the induction coil, and
induction-heating the portions.
7. The heat treatment according to claim 6 , wherein the coil spring is allowed to fall, when the coil spring has heated up to a predetermined hardening temperature, into a cooling tank containing a coolant by pulling the supporting rod out of the hollow portion of the coil spring.