The paper objective is to determine the most resistant type of microstructure of 10G2FB pipe steel to stress corrosion cracking (SSC). The study task is to compare SSC tendency of samples after various types of machining: controlled rolling, improvement (quenching at 920°C + high tempering at 600°C) and quenching from the intercritical temperature range (ITR) with low tempering (800°C + tempering at 200°C). The research methods include tests for resistance to SSC using the three-point bending method in a nitrate medium, metallographic studies of the microstructure of steels using a specialized microscope and measurements of microhardness. The novelty of the work lies in finding the relationship between the microstructure formed under various heat treatment conditions and the time up to destruction of samples under accelerated testing conditions. The results of the study show that after the improvement, the samples with a homogeneous structure did not rupture over a given time base of 20 hours. The samples after controlled rolling with a ferrite-pearlite structure and with pearlitic banding of the third grade were destroyed in 6.5 hours, and the samples after quenching from the intercritical temperature range (a structure characterized by different grain sizes) were destroyed in one hour of testing. Thus, the highest resistance to SSC is provided by an improvement that forms a homogeneous microstructure. The presence of banding, which was revealed in the samples after controlled rolling and in the samples after quenching from ITR, is a critical factor reducing the resistance of steel to stress corrosion cracking in an aggressive environment.
Yuliya Mordovina (Sun,) studied this question.