engleski

The influence of austenitizing parameters on the grain size of hypoeutectoid steel

It is well known that the properties of certain steel are the result of its structure. By crossing the A3 temperature during the heating of hypoeutectoid steel, the transformation of pearlite and ferrite to austenitic structure is completed. If during the austenitizing process a rough grain austenite arises, after the quench hardening there will be also large size martensite needles, and after a longer cooling time, the ferritic-pearlitic structure will appear with the large grain size. The steel with rough grain has lower strength, impact toughness and susceptibility to brittle failure, so beside the desired structure, the goal of the appropriate selection of the heat treatment parameters is to achieve as small grain size as possible. In this paper, the effect of austenitizing parameters (temperature and time) on the hypoeutectoid steel grain size changes is experimentally investigated. The experiment was conducted according to the factorial design of experiment as a variation of two factors (the first factor is austenizing temperature and the second austenizing time) on three levels (ϑ a: 900, 975 and 1050°C, log t: 2, 3, 4 s). With the factorial design of experiment 32, the influence of individual factors (austenitizing temperature and time) and their interactions on the grain size and hardness of hypoeutectoid steel was determined statistically. The metallographic investigations of the grain size by ASTM E112 method and Vickers hardness tests HV2 were performed on the heat treated samples of hypoeutectoid RSt37-2 steel.

austenitizing; grain size; hypoeutectoid steel; factorial design of experiment

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