Development of Ultrasonic Technique for Surface Crack Detection of Semi-HSS and HSS Rolls

The high speed steel (HSS) rolls have high hardness and good wear resistance at high temp. This type of roll is used in finishing applications for increased campaign times and better surface finish. As the hardness of HSS reaches 80/85 shore, it becomes very much crack-sensitive. Hence it is highly recommended to eliminate all kinds of surface cracks, whenever these rolls are reground, other-wise typical `cats'-tongue band type spalls may occur that lead to abnormal failure. Surface waves ultrasonic tech-nique has been used to detect the surface cracks and to establish the optimal grinding condition for obtaining correct surface contour required for the next rolling process.