Abstract: Continuous cooling transformation (CCT) curves of a bainitic wear-resistant cast steel used for mining machinery were determined based on the dilatometric measurement, optical microstructure examination as well as microhardness test. The results show that the phase transformation temperatures Ac₁, Ac₃, and Ms (martensite starting transformation temperature) are 790 ℃, 845 ℃, and 303 ℃, respectively. For the cooling rate below 0.05 ℃/s, ferrite and pearlite are obtained; for that between 0.05 ℃/s and 0.1 ℃/s, the transformation products are ferrite, pearlite and bainite. For that between 0.25 ℃/s and 15 ℃/s, a bainite/martensite multiphase microstructure is obtained. When the cooling rate is higher than 30 ℃/s, the undercooled austenite almost completely transforms into martensite. The critical cooling rate of martensite is between 15 ℃/s and 30 ℃/s. With the increase of cooling rate, the microhardness increases rapidly at first and then tends to be 585 HV0.01.

Key words: bainitic wear-resistant cast steel, continues cooling transformation curve, microstructure, microhardness