PREPARATION METHOD OF DRY MAGNETIC PARTICLE FOR CRACK DETECTION

摘要

PURPOSE: Provided is a preparation method of dry magnetic particles for easily detecting cracks not less than 150 micrometers on the surface and near the surface using reduced iron powder with low logotype property. The invention enhances the detection power just with grinding process and controlling the particle size of low logotype reduced iron. This invention uses less amount of the coating powder with the particle size of less than 45 micrometers, thereby lowering the detection of non damaging cracks and preventing the lower detection rate due to the background noise. The preparation cost is lower than the conventional process because the invention uses the reduced raw ores. CONSTITUTION: The preparation method comprises grinding the raw powder which is coated with reduced iron and controlling the distribution of the particles sizes so that it has 4.5-1% of powders with 300-250 micrometers particle size, 30-20% of powders with 250-106 micrometers, 54-40% of powders with 106-45 micrometers and 11-20% of powders with 45-25 micrometers.