Microstructure Development by Controlling Grain Size

In this Paper, a classical PID controller and an adaptive fuzzy logic controller are employed for controlling the microstructure development during hot working process. The strength of any material is dependent on the grain size of that material [4], [9]. The strength the material is increased when its grain size is reduced. In this paper, the standard Arrehenious equation of 0.3% carbon steel is utilized to obtain an optimal deformation path such that the grain size of the product should be 26 m. The 0.3% carbon steel improves in the machinability by heat treatment [8]. It must also be noted that this steel is especially adaptable for machining or forging and where surface hardness is desirable. The plant model is developed with grain size. The effect of process control parameters such as strain, strain rate, and temperature on important microstructural features can be systematically formulated and then solved as an optimal control problem. These approaches are applied to obtain the desired grain size of 26 m from an initial grain size of 180 m. The simulation is done on various grain sizes using both the controllers by MATLAB simulink toolbox. When comparing the responses, the PID controller provides better performance compared with fuzzy controller. Resulting tabulated performance indices showed a considerable improvement in settling time besides reducing steady state error.