Using NDT methods for inspection work rolls

The rolls used in Rolling Mill included different material and size, such as high alloy forged rolls, muti-casted iron rolls etc. The sizes are from Φ360 mm to Φ1960mm, hardness layer in difference depth by heat-treatment. New rolls and used rolls are inspected by different NDT methods to make sure its in good condition for next rolling turn. In general, longitudinal UT used for internal defects and Rayleigh (Surface) wave UT or MPT/PT used for surface cracks. We also used ECT to measure the surface cracks during grinding roll process. Finally, we will measure the hardness, hardness layers and the residual stress in rolls.