Cause Analysis on Magnetic Mark Display of a Batch of Bolts

Taking a batch of bolts with magnetic mark display as the research object, the causes of magnetic mark display were analyzed. After eliminated the banded segregation, the magnetic mark display no improvement.The causes of no improvement of magnetic mark display after eliminated band segregation of the bolts were studied by means of tower hairline detection, metallographic examination and energy spectrum analysis. The results show that the magnetic mark dislay of the bolts were not caused by banded segregation, but by metallurgical defects (inclusion exceeding standard) of the raw materials.