The Distribution of Temperatures in a Hot/Cold Die Set: The Effect of the Pressure, Temperature, and Material

Abstract

Modern hot metalforming operations require a predictive-adaptive control program in which the predictive component precalculates the necessary parameters—such as temperatures and loads—and the adaptive component sets up, monitors and adjusts the forming equipment. One of the needs of a predictive model of the process is for an understanding of the boundary conditions at the surface of contact. For high temperature operations, one of these conditions is described by the heat transfer coefficient, relating the heat flux and the difference of the temperatures of the contacting surfaces, at the die-workpiece interface. The surface temperatures are, of course, dependent on the distribution of the temperatures within the body of the dies. The determination of these distributions is the topic of the present project. Thermocouples embedded in a cold/hot die set as well as thermocouples placed on the surface of contact are used to monitor the temperature fields, within the body as well as on the surfaces, for various interface pressures, initial temperatures and materials. The results indicate that direct measurements of the temperatures of the contacting surfaces is very difficult and may lead to significant errors. It is recommended that a mathematical model, which uses the measured internal temperatures as initial conditions, should be employed to calculate the contact surface temperatures.