This paper deals with the influence of various austenitizing temperatures on microstructure and kinetics growth of austenite grain in 9 CrNB steel. High austenitizing temperatures (1070 °C, 1150 °C, 1170 °C, 1190 °C, 1210 °C and 1230 °C) with a holding time 120 min were used. The microstructure was formed by martensite after austenitization. The occurrence of delta ferrite was observed in microstructure at temperature higher than 1190 °C. Delta ferrite was located at the grain boundaries and its amount was about 3 % at the austenitization temperatures of 1190 °C and 1210 °C and up to 5.5 % at the temperature of 1230 °C. In terms of the kinetics of austenite grain growth, it can be concluded, that up to temperature of 1170 °C there is an increase in grain size. At the higher austenitization temperature (over 1190 °C) we observed the decrease of grain size.Keywords: Austenitizing temperature, heat treatment, delta ferrite, grain growth, low carbon 9Cr steel
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