HEATING APPARATUS AND HEATING METHOD
FIG8 is a diagram schematically illustrating a hardening pattern of a workpiece according to a test example 
In Test Examples 1 to 3, a quenching process was performed on both side surfaces Wa, Wb of the workpiece W using the heating apparatus 1, and a quenching coolant was sprayed to the workpiece W at a predetermined flow rate to cool the workpiece W on the downstream side of the coil 10 in the feeding direction of the workpiece W. Heating conditions of Test Examples 1 to 3 are described in Table 1, and hardening patterns of the workpiece W in Test Examples 1 to 3 are schematically illustrated in FIG8.Table 1Ex. 1Ex. 2Ex. 3Cooling fluidNot sprayedSprayedSprayedSet power (kW)505080Oscillation frequency (kHz)252525Workpiece feeding speed (mm/sec)8080120Coil coolant temperature (□C)Supply port141414Discharge port282627Hardened layer depth (mm)1.8-2.11.8-1.91.7-1.9Crystal grain size (GSNo.)11.711.811.7
diagram
110
coil
130
nozzles nozzle
['1. A heating apparatus comprising: a coil configured to receive AC power to form a magnetic field that inductively heats a workpiece; and a spray unit configured to spray cooling fluid including a liquid to a heating target portion of the workpiece placed in the magnetic field in a form of a mist at least during a period in which the AC power is supplied to the coil.']