Mechanical Nanocrystallization Surface Treatment on the Reheated 400MPa Ultrafine Grained Steel

Abstract

After reheated at different temperatures for 5 minutes, the 400MPa Ultrafine Grained Steel specimens were air-cooled to room temperature, and then carried out the mechanical nanocrystallization surface treatment and structure performance testing. On the basis of comparing the test results on the specimens before and after the mechanical nanocrystallization surface treatment, the process of mechanical nanocrystallization was analyzed briefly. The results show that: as the reheating temperature rising, the trend of grain size growing increases markedly, and the mechanical properties also drop down to different degrees; when the reheating temperature is around 800°C, because of the pearlite spheroidized significantly, its mechanical properties drop the most seriously; after the mechanical nanocrystallization surface treatment, not only its surface form a layer of fine nano-layer (about 100 nm) structure, but also its mechanical properties rise obviously, and the yield strength is over 450MPa.