Structural-Phase State Of Austenitic 20GL Steel After Thermal Treatment by Normalizing and High-Temperature Tempering

The article presents the results of a study of the influence of normalizing at 900 °C and high-temperature tempering at 650 °C on the microstructure and mechanical properties of cast steel 20GL. Heat treatment modes with and without high-temperature tempering were analyzed taking into account the geometric dimensions of the specimens. The microstructure and structural-phase composition of cast steel specimens after heat treatment were studied using transmission and scanning electron microscopy and X-ray diffraction analysis. Results showed that the selected mode ensures noticeable changes to ferrite-pearlite, homogeneous, fine-grained structure with grain size number 9 and Brinell hardness 170 HB. Mechanical tests for static tensile and impact strength resulted in selection of the optimal content of manganese in studied cast steel as 1.2 wt. %. It has been established that the processes of final deoxidation have the greatest influence on the mechanical properties of steel determining the nature and character of non-metallic inclusions.