Microstructure and Decomposition Kinetics of Supercooled Austenite in Medium Carbon Steel 38G2F

The morphology of structural components in hot rolled pipes made of 38G2F steel has been studied by optical metallography. It is shown that the sections elongated along the rolling direction with a morphology different from pearlite are sections of upper bainite, the hardness of which is comparable to the hardness of pearlite (~290–300 HV μ ). Plotting the thermokinetic diagrams (TKD) of the decomposition of supercooled austenite, as well as a joint analysis of the microstructure and hardness, allowed us to determine the minimum velocity V cool ~ 0.5°C/s at which the bainite component in the pipe wall is formed. The temperature–time parameters of the decomposition of supercooled austenite with increasing austenitization temperature from 850 to 1000°C have been determined.