Prediction of Final Material State in Multi-Stage Forging Processes

Multi‐stage forging processes are used to manufacture reservoirs for high pressure hydrogen and tritium storage. The warm‐forging process is required to produce required macro and microscale forged material properties of 304 and 21‐6‐9 stainless steel. Strict requirements on the forged material strength, grain size and grain flow are necessitated to inhibit the diffusion of gas which inevitably leads to material embrittlement. Accurate prediction of the final material state requires modeling of each of the forging stages and tracking the material state evolution through each deformation and reheating stage. An internal state variable constitutive model, capable of predicting the high strain rate, temperature dependent material behavior, is developed to predict final material strength and microstructure. History dependent, internal state variables are used to model the isotropic and kinematic hardening, grain size and recrystallization. Numerical methodologies were developed to track and remap material sta...