Development of a fast converging material specific void closure model during ingot forging

The current paper focuses on the subject of internal voids and the process of hot forging used for their elimination in the manufacturing of large steel billets. A new method is proposed to identify and compare the applicability of five different void closure models to large size ingots. The effects of remote equivalent strain, stress triaxiality state and material parameters are considered in the analysis. The Hansel-Spittel flow stress law is implemented as a foundation for the development of original rational polynomial equations capable of predicting the value of void closure equation material dependant constants. Void closure is simulated for an extended range of materials and specifically applied to a newly developed high strength steel. Coupled parameter effects and material sensitivity are visualised using novel animated 3D mapping. FEM is used to give a quantified evaluation of the effect of void positions during forging. The effectiveness of the upsetting process concerning void closure in central upper billet and core regions is discussed and optimum conditions identified.