The Influence of Temperature and Soaking time on the Microstructure and Mechanical Properties of annealed AISI 1045 Steel

Abstract

In this present work AISI 1045 medium carbon steel was subjected to different conventional heat treatments mainly a full annealing, normalizing and hardening.  The annealing processes were first carried out at annealing temperatures 850,900 and 950°C for one-hour soaking time. Later the periods of annealing were changed from five minutes up to two hours all of which at 850°C austentization temperature.  In addition, normalizing and hardening processes were performed at an intermediate austenitization temperature of (850°C) and the soaking time mainly one hour. Therefore, the main objective of the current study is to investigate the effect of both annealing temperatures and soaking times on the microstructure, macrohardness and impact toughness of 0.45%C.  Meanwhile, the results of 0.0.45%C steel annealed at 850°C for one hour were compared to that of normalized and hardened steels.It was concluded that, the change in the macrohardness and absorbed energy of 0.0.45%C annealed steel was mainly attributed to the morphology, grain size and the amount of formed austenite through its influence in defining the final microstructure of the products at room temperature.In contrast, the proportion of ferrite and pearlite micro-constituents in the structure of normalized steel was found to have a predominant role in such behavior whereas the macrostructure of hardened steel reveals almost martensite phase that made this steel possess the maximum hardness and the lowest impact toughness among all tested samples.