The effect of austenite temperature on the fatigue strength of mild steel

Abstract

The effect of austenite temperature on the fatigue strength of mild steel is investigated by using the Scanning Electron Microscopic (SEM). Fatigue tests under the rotating bending fatigue testing machine has been carried out to estimate the effect of austenite temperature on the fatigue strength of mild steel. The fatigue strength of these material has been studied as a function of austenite temperature from 725ºC to 875ºC test temperature and then the specimens are tempered at 150ºC with time hold up to an hour. The specimens will be put into the furnace for the heat treatment process to be done before the fatigue testing experiment is being carried out. The curve of stress versus number of cycles has been plotted in order to determine the fatigue strength of the mild steel. The initiation and propagation behaviors of micro cracks were investigated on the specimen surface. The fatigue strength rates increasing as the austenite temperature increases to 800ºC due to crack length occurs on the specimen surface and the decreasing again with higher austenite temperatures. The hardness at 800ºC was higher than that all of the austenite temperatures. The effect of austenite temperature on hardness and the relationship between the microstructure are discussed.