Microstructure and Mechanical Properties of Hot-rolled Ultra-high Carbon Steel

Hot-rolling was applied to pretreated ultra-high carbon steel (UHCS).The obtained microstructure consisted of fine,spherical and dispersion-distributing carbides and partial lamellar pearlite,which effectively improved spheroidization of carbides.Different heat treatment technologies based on DET(divorced eutectoid transformation) were taken to spheroidize the hot-rolled UHCS.SEM observation shows that austenitizing state affected the spheroidization of carbides.Higher austenizating temperature or longer holding time of the ultra-high carbon steel increas particle spacing and size of carbides.Ambient tensile test indicat that the spheroidized steel reveal excellent mechanical properties,including obvious yielding phenomena with good strength and plasticity.The UHCS austenized at 850 ℃ show that σ0.2 and σb are 688 MPa and 1 005 MPa,respectively,together with extension rate of 16.7%.