Metallurgical studies on a failed EN 19 steel shear pin

The presence of inclusion at or close to the surface of components are detrimental for their performance, especially when they are subjected to fatigue loading. Role of inclusion in fatigue performance of a shear pin, fabricated out of EN 19 steel has been studied. The shear pin was used in a chemical mixer as an overload protection, attached to agitators, rotating at different revolution per minutes (rpm) depending on the power transmitted to it through gear system. The shear pin located in the power transmission system had a notch throughout the periphery and fractured incidentally at notch, after use for a cumulative period of approximately 100 h. Extensive metallurgical investigations revealed that inclusions, present in the steel and located near the notch, a region of high stress zone, caused fatigue crack to initiate. Once the crack was initiated under fatigue, de-bonding and fragmentation of non-metallic inclusion facilitated its propagation. This paper highlights the details of investigation carried out on the fractured shear pin and established the deleterious effect of inclusion in steel, especially for fatigue performance. (C) 2007 Elsevier Ltd. All rights reserved.