Non-destructive testing method for steel parts - leakage flux appears at defects on magnetising steel with alternating field

摘要

Steel workpieces and welds are non-destructively tested using alternating magnetic fields by applying a.c. to plate-like pole pieces presented edge-wise w.r.t. workpieces. The pole pieces are surrounded by coils fed from the a.c. supply and may be resiliently urged towards the workpieces and provided with rollers to roll on the steel workpiece or weld fluorescent magnetic particles are applied to the workpieces and are subsequently blown away to leave particle deposits at the defects. Alternatively, using the roller method, a magnetically satd. tape may be provided for recording defects.