Abstract
Graphites are subjected to severe thermal shock, to thermal fatigue and to their combined effect, when they are practically used as core material in the nuclear reactor, or as electrode in the steel making furnace at very high temperature. In consequence of the combined thermal shock fatigue, three material parameters to govern the strength have been found in the general equation expressed by maximum temperature difference to resist the fracture.
An ultra-high temperature strength testing apparatus has been designed and applied to measure the tensile strength, elastic modulus, fracture strain for four grades of graphite up to 2500°C. The thermal expansion coefficients were also measured by another high temperature apparatus.
The high temperature strengths of four grades of graphite have been discussed comprehensively according to the maximum temperature difference determined by the parameters on the basis of these experimental date as functions of temperature, heat transfer and number of fatigue cycle.
