Development of Methodology to Analyse the Amplitude of Ultrasonic Signal from Shell/Core Interface of ICDP Rolls

ICDP rolls are produced by centrifugal casting and have outer shell made of indefinite chill cast and core is of nodular or flake graphite cast iron. During casting of the rolls, aim is to achieve full metallurgical bond between the shell and the core. Any disbonding, presence of flux/ slag at the interface or excess of carbides, microporosities, graphite flakes, non-metallic inclusions may reduce the strength of the bond and that ultimately leads to big spalling. Hence it is a general practice of the roll manufacturer to assess the interface quality of rolls using non-destructive technique especially ultrasonic. While testing with conventional UT, the sponsor is reporting that the UT signal amplitudes are gradually increases from trailing to leading edge with identical gain, even in case of flaw free rolls. This is a general observation in all the ICDP rolls and non-existence of flaw has also been verified by cutting the roll. This project makes the challenge to identify the causes for such variation in UT signal amplitudes and subsequently need to develop a methodology to determine the interface echo amplitude based on the attenuation/velocity of shell, interface and core regions through the ultrasonic C scan imaging and authentication could be made by correlating the results of C-scan imaging with microstructures of the various regions.