Integrated Multiscale Robust Design Considering Microstructure Evolution and Material Properties in the Hot Rolling Process

Abstract

A transmission gear is generally produced by a sequence of several processes from steelmaking to final machining and surface treatment. The intermediate processes such as hot rolling induce microstructure evolution and phase transformation which play a significant role in determining the mechanical properties and fatigue strength of gears. Therefore, these intermediate processes should be carefully considered in determining the performance and properties of the end product. In this paper, an integrated multiscale robust design approach using the Inductive Design Exploration Method (IDEM) is implemented to improve robustness in the presence of uncertainty by exploring the solution space in order to find feasible solutions to satisfy technical requirements and/or customer aspirations. Four pass roll design with oval and round grooves is used to simulate the hot bar rolling process. The microstructure evolution, flow stress, and wear prediction models are implemented in the analysis model to account for the process-structure relationship in each roll pass. Surrogate models for some parameters such as ultimate tensile strength are then developed based on the analysis results. Using the relationship of processing-structure-property-performance, the integrated realization of engineered materials and products (IREMP) can be accomplished over multiple length scales. In IDEM, the range of the property-performance relationship is first evaluated by the requirements for the end product. Subsequently, the austenite and ferrite grain sizes and material properties are inductively determined by exploring the design space. Consequently roll pass design including the rolling conditions and the microstructure of billets are customized by the exploration of design variables based on IDEM.