Effects of Chemical Composition, Ingot diameter and shape on Solidification and Macrosegregation in Large Size Ingots of High Strength Steels

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Large size forged blocks are used for the manufacturing of critical components such as shafts and dies in transportation and energy industries. The first step in producing such components is ingot casting. However, due to the large size of the ingots, chemically heterogeneous zones (macrosegregation) are produced which often cannot be eliminated during the subsequent heat treatment or forging operations leading to part non conformity and/or rejection. In recent years the demand for larger size ingots (up to 100 tons) has been continuously increasing and therefore it is of critical importance for the ingot casting/forging industry to develop methods and approaches that would allow producing large size ingots with no or little macrosegregation. The problem is even more acute in the North American context, because of the fierce competition from emerging manufacturing countries and new regulations that result in increased costs. To achieve this objective, a more in-depth knowledge of the interactions between material characteristics (composition, microstructure, etc.) and process parameters is required. The development of such knowledge base manufacturing process is the key objective of the present Collaborative Research and Development (CRD) project. In a previous collaboration with the industrial partner, Finkl Steel-Sorel, very interesting results were generated which resulted in significant progresses and savings for the industrial partner. In this project, the work will focus on studying parameters that were not addressed during the first phase, apply the developed findings to new alloys and ingot sizes and develop new methodologies that would allow producing high quality ingots and contribute to strengthening the position of the industrial partner as one of the world leaders in processing of large size ingots.Experimental study using advanced testing equipment will be conducted to develop material models describing the evolution of the microstructure. The developed material models will be implemented into Finite Element (FE) commercial codes to predict local microstructure heterogeneous zones and phase transformation characteristics in large size ingots. The research results will be validated ultimately at the industrial level.