The paper deals with the effect of heat treatment parameters on mechanical properties and microstructure of low alloy high-strength steel 55 Cr3. The material standard of this steel defines the hardening temperature interval from 830 to 850 °C, which brings about the question of minimum soaking time in order to dissolve carbide particles and to homogenize austenite before quenching. The higher is the heating rate the higher is also the temperature that ensures perfect transformation of the initial microstructure into austenite and makes optimum conditions for desired final microstructure and properties of the steel. The dilatometric analysis performed on the samples simulating different conditions of austenitization confirmed that the incomplete austenitic transformation moved the curves of pearlitic and/or bainitic transformation in CCT diagram of the steel to the left, i.e. towards shorter times. After cooling the mixed microstructure containing not only the desired phases (bainite and/or martensite) but also a significant proportion of pearlite, including the original undissolved pearlite, was detected.Keywords: Low alloy high-strength steel properties, heat treatment, dilatometric analysis, CCT diagram mechanical properties, microstructure
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