Rolls are massively manufactured and consumed in manufacturing industries. Their quality and price are strictly related to the defect size and distribution in the roll which is required to inspect with proper NDT methods. This study focus on the establishment of ultrasonic methods for inspecting the as-cast defects of shrinkage, slag and incomplete fusion in the interface of composite sleeves. These methods are to be employed in order to decide whether the roll should be accepted or rejected. An automated ultrasonic technique was used either with the contact or immersion method for three different composite rolls characterized as (1) outer tool steel and inner ductile iron with or without outer surface machining, (2) outer alloyed casting and inner ductile iron and (3) cast iron. Results showed that with the automated scanner magnetically attached to the rolls' outer surface, isolated and distributed defects could be clearly indicated by B-scan images. The minimal detectable independent defect such as porosity is around 1 mm in diameter. Distributed defects, corresponded to non-homogeneous micro-structure in rolls made by the current process, were invisible with naked eyes but clearly revealed by this method. Castings could be further refined in terms of this result which was not possible simply examined by the conventional UT. Therefore, automated ultrasonic method employed in this study could be also used as an alternative of macrostructure examination by optical method.
Roll Ultrasonic Defect