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

大尺寸锻造块用于制造关键部件，如轴和模具在运输和能源行业。生产这种部件的第一步是铸锭铸造。然而，由于铸锭的大尺寸，产生了化学不均匀区（宏观偏析），通常在随后的热处理或锻造操作中无法消除，导致零件不符合和/或退货。近年来，对大尺寸铸锭（高达100吨）的需求一直在不断增加，因此，对于铸锭/锻造行业来说，开发能够生产没有或很少宏观偏析的大尺寸铸锭的方法和途径至关重要。由于来自新兴制造业国家的激烈竞争以及导致成本上升的新法规，这个问题在北美的情况下更为严重。为了实现这一目标，需要更深入地了解材料特性（成分、微观结构等）与工艺参数之间的相互作用。

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.