INFLUENCE OF MICROSTRUCTURE ON THE PREMATURE FAILURE OF A 2ND-INTERMEDIATE SENDZIMIR MILL DRIVE ROLL

Although a precise understanding of roll failure genesis is complex, t he microstructure of a broken roll can often unravel intrinsic deficie ncies in material quality responsible for its failure, This is especia lly relevant in circumstances when, even under a similar mill-operatin g environment, the failure involves a particular roll or a specific ba tch of rolls. This paper provides a microstructural insight into the c ause of premature breakage of a second-intermediate Sendzimir mill dri ve roll used at a stainless steel sheet rolling plant under the Steel Authority of India Limited. Microstructural issues influencing roll qu ality, such as characteristics of carbides, tempered martensite, retai ned austenite, etc., have been extensively studied through optical and scanning electron microscopy, electron-probe microanalysis, image ana lysis, and x-ray diffractometry. These are discussed to elucidate spec ific microstructural inadequacies that accentuated the failure. The st udy reveals that even though retained austenite content is low (6.29 v ol%) and martensite is non-acicular, the roll breakage is a consequenc e of intergranular cracking caused by improper carbide morphology and distribution.