DZIURKA Rafal AGH University of Science and Technology

Spoluautoři PACYNA Jerzy

The hereby work presents the influence of heating rate on the phase transformations during tempering. The tempering of the as-quenched samples of three Cr-Mn-Mo model alloys with different carbon content was made at 350°C. The temperature 350°C was chosen because the irreversible temper brittleness effect occurs. The investigations of phase transformations during tempering of the steels were made on the grounds of dilatometric curves recorded during heating from as-quenched state. Heating to 350°C was made with two different heating rates (150°C/s and 5°C/s). Dilatometric investigations were performed by use of the DT 1000 dilatometer made by Adamel, and L78 R.I.T.A. (Rapid Intensive Thermal Analysis) dilatometer made by Linseis. The methodology of the dilatometric investigation and the method of the characteristic points determination were described. As it is known, the temperatures of starting and ending of individual phase transformations increase with the heating rate increase. It is possible to obtain a difference in the advancement of various phase transformations during tempering, through different heating rates to the selected temperatures. It is possible to reduce probability of the occurrence of some phase transformations (e.g. transition carbides) in favor of other (e.g. cementite carbides). The difference in advancement of the various phase transformations can effects on various mechanical properties of the steels above all toughness and hardness.

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