Study of the transformation of supercooled austenite of steel using high-resolution dilatometry
The development of methods for experimental research of phase transformations, including high resolution dilatometry, allows to estimate fast processes in each moment of time, to determine the state of the test specimen with high accuracy and to detect relatively weak effects from processes in the investigated material. So requires the development of new approaches to the analysis of the data. The new method of analysis of the first derivative of the dilatogram showed good results in the analysis of processes in the intercritical temperature range during continuous heating of steels, which makes its application promising for the study of processes during cooling. Thus, the article is devoted to the study of the transformation of supercooled austenite in steel 30XGSA using high-resolution dilatometry and subsequent analysis of dilatometric data. Additionally, calorimetry, metallography and hardness testing were used in the current work. The proposed method of analysis of the dilatometric data of the transformation of supercooled austenite during continuous cooling, which consists in the analysis of the first derivative miltogramma with decomposition into components peaks, allows to separate volume effects from different phase transformations and to split the identified processes on the temperature scale. Using a new method of analysis of dilatometric data, the processes of decomposition of supercooled austenite in steel 30XGSA under cooling with velocities from 0.15 to 100 °C/s were studied and a new continuous cooling transformation diagram was constructed, where the regions of all noticed transformations were separated. A good agreement between the results obtained using the proposed approaches to dilatometry and the data of calorimetry, metallography and hardness testing results was established.