Patent ID: 8893538

Claim:
An instantaneous heat treatment method for a metal product, comprising: mixing substantially perfectly spherical shot having three or more approximate but different particle sizes within a range of #100 to #800 (average particle diameter: 149 μm to 20 μm), the shot having a hardness higher than the hardness of a base metal of a workpiece; and intermittently ejecting the shot in the form of a fluid mixed with compressed air onto the workpiece for a period of 0.1 seconds to 1 second, at intervals of 0.5 seconds to 5 seconds, at an ejection pressure of 0.3 MPa to 0.6 MPa, at an ejection speed of 100 m/sec to 200 m/sec, and at an ejection distance of 100 mm to 250 mm, thereby randomly forming numerous micro-concavities in a surface of the workpiece, each of the micro-concavities having a substantially circular bottom surface with diameter of 0.1 μm to 5 μm.