Abstract: Taking 28MnCrMoRE steel oil well pipe as the research object, the effect of quenching process on microstructure and hardness of deep well oil well pipe was explored. The prior austenite grains after quenching were observed by using metallographic microscope, and the prior austenite grain size was obtained by Image-ProPlus software. The microstructure after quenching was observed and analyzed by using SEM. The hardness was measured by using Rockwell hardness tester. The results show that the average size of prior austenite grains increases from 8.21 μm to 12.67 μm in the 28MnCrMoRE steel after holding at 870, 900 and 930 ℃, respectively, for 30 min then water quenching. When quenched at 900 ℃ for 90 min, there is a significant abnormal growth of the prior austenite grains, when held for 30 min, the prior austenite grains in the tested steel are relatively small and uniform, and the grain size conforms to a normal distribution. The quenched microstructure of the 28MnCrMoRE steel is martensite + bainite + retained austenite. With the increase of quenching temperature or the extension of holding time, the content of martensite gradually decreases, the microstructure has a certain degree of coarsening, and the hardness of the tested steel first increases and then decreases, with a maximum value being 53.02 HRC.

Key words: 28MnCrMoRE steel, oil well pipe, quenching process, microstructure, hardness