1.The Second Steel Plant,Xinyu Iron and Steel Group Co., Ltd., Xinyu 338001, Jiangxi, China; 2.Technology Center,Xinyu Iron and Steel Group Co., Ltd., Xinyu 338001, Jiangxi, China; 3.National Engineering Research Center of Continuous Casting Technology, CISRI, Beijing 100081, China
Abstract：In order to study the high temperature hot plasticity, the microstructure evolution and transformation point under different cooling rates for free cutting die steel were investigated using a dilatation equipment to draw CCT curve. The high-temperature tensile fracture behavior was carried out using a Gleeble-3800 hot simulation testing machine. Combined with the fracture morphology, the hot ductility rules were investigated. The experiment results showed that there were three zones for the hot ductility curves, which were the Ⅰ brittle zone, the hot ductility zone and the Ⅲ brittle zone, respectively. The tensile property for the experimental steel deformed at 950-1 150 ℃ was best, which was in the hot ductility zone. Below 950 ℃, it was the Ⅲ brittle zone. The fracture morphology was dimples and cleavages. With the increase of temperature, the dimple quantity increased and the ductility turned better. Until to 950 ℃, the fracture morphology was whole dimples. When the temperature range was above 1 300 ℃, it was the Ⅰ brittle zone, the elongation rate decreased with temperature. Increasing the cooling rate, the stress formed in the austenite during cooling increased, which caused the elongation decreased compared to the lower cooling rate.
2020, Vol. 30 
