Studies on Recrystallization and Tensile Strength of Tungsten Wire

Abstract

A method to evaluate the recrystallization of tungsten wire was studied by measuring its tensile strength at room temperature after heat treatment.The tungsten wire was heated by electric current in the atmosphere of dissociated ammonia gas. We found a suitable method to determine the necessary electric current in order to heat the tungsten wire up to the desired temperature.The results are summarized as follows:(1) The necessary electric current to heat the tungsten wire up to the desired temperature in the range between 1200°C and 2000°C will be estimated approximately using the following formula;i=71.2MG·V/T·l(2) The tensile strength of the tungsten wire decreased rapidly by short time heat treatment, this means that recrystallization takes place for the most part in a short time.(3) The tungsten wire with low recrystallization temperature has low tensile strength at room temperature, and shows exaggerated grain growth after heat treatment.(4) There is close correlation between the tensile strength before the heat treatment and the tensile strength after the heat treatment.