Examination of Slit Defect Inspection Method for Steel Bars Using Only DC Magnetic Field with the Velocity Effect

C45, a ferromagnetic material, can be strengthened by heat treatment such as quenching and is widely used as a material for general mechanical parts such as springs in automobiles.However, the presence of defects or flaws can cause cracking during the quenching stage, and a high-speed inspection method for detecting defects is required.In this study, we proposed and examined an inspection method for detecting defects using only a DC magnetic field by moving a round steel bar material at a high speed of 1 m/s inside a ring-shaped permanent magnet and generating eddy currents due to the velocity effect.