THE INFLUENCE OF LOW AND HIGH ANNEALING ON THE HARDNESS OF STEEL EN 42CRMO4

Hollomon and Jaffe [1], [2] have given the functional dependence of the annealing parameters (temperature and time) P = f (T, tau). In other words, if using a combination of temperature and annealing time, resulting in equal parameters value, hardness will remain unchanged. This function refers only on steels. To determine the parameters of annealing for desired hardness after treatment, it is necessary to know the annealing diagram (H=f(T)) of the observed steel. This paper investigates the possibility of obtaining a mathematical model where the hardness is function of annealing temperature and time (H=f(T, tau)). Design of experiments and statistical analysis were performed using the program "Design Expert 6.0" [3]. The cylindrical specimens were 10 mm length and 25 mm in diameter. The experiment was conducted in two levels. The first level was related to high temperature annealing, while the second level was related to the low temperature annealing. The reason for this approach was based on significantly different microstructure that appears at low and high annealing temperatures.