Minimizing the Cycle Time of a Roller Hearth Furnace for Hot-Forming Die-Quenching

In most hot forming die quenching (HFDQ) processes, roller hearth furnace parameters, including roller speed, blank layout, and zone temperatures, are adjusted by trial-and-error. The resulting solution is always suboptimal and often leads to incomplete austenitization. This paper presents an optimization procedure for an industrial roller hearth furnace for minimizing cycle time, structured around a thermo-metallurgical model used to determine the total heat load, dropout temperature, and austenite phase fraction. Imposed constraints include minimum fraction austenite and burner capacity, and the optimization problem is solved using nonlinear programing. The outcome highlights the potential of improving process efficiency through design optimization, and the importance of high-fidelity metallurgical modelling. (paper)