Experimental research of optimization methodology for local, resistive - heating of thin molybdenum plates

Abstract

Because of the unique mechanical and chemical behavior of molybdenum and its alloys, they become one of the most advanced materials for high-temperature heating elements, the most exposed areas of furnace, the aircraft industry and the components of the crystallization apparatus at sapphire single crystal growth. This paper presents unique design an experimental system, which shall be in future optimized through simulation model, for comprehensive analysis of important parameters of resistance heating of pure molybdenum sheet with the thickness of 0,5 mm. The specific details of the shape, size and spatial distribution of the heating electrodes based on copper and graphite are investigated. Technical solutions for generation of contact pressures as well as the mechanism for moving the sheet through the zone of thermal exposure is described in detail. Details of the control of power components of the experimental system are shown schematically in the paper. Numerical simulation of resistance heating are provided in Comsol SW, which gives optimal support for experimental analysis at different conditions of electric current and voltage exposure for resistive contacts made of copper, graphite, and combination of those two materials. Further optimization is done in the way of shape and location modification of the contact electrodes, modification of the specific contact pressure-lowering contact resistance, and modification of time of stress exposure and also the distribution of temperature fields in the exposed zones of molybdenum samples. Presented are also experimental thermal characteristics of the heated volumes of molybdenum metal after the end of the heating-response to thermal exposure using a thermal image technology.