The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the pr...The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.展开更多
Thermo-Calc software package (TCP+DICTRA) was used to simulate the carbide transformation process in die steel for plastic. Combined with TEM analysis, the calculated result confirms that the carbide in equilibrium st...Thermo-Calc software package (TCP+DICTRA) was used to simulate the carbide transformation process in die steel for plastic. Combined with TEM analysis, the calculated result confirms that the carbide in equilibrium state is M_7C_3 carbide. The dissolution of M_7C_3 carbide in steel is predicted by DICTRA program. It was shown that the temperature remarkably affects the dissolution process of M_7C_3 carbide, but the influence of alloy elements such as manganese and molybdenum can be neglected in this steel.展开更多
55Cr17Mo1VN high nitrogen martensitic stainless steel is usually applied to the high-quality mold,which is largely produced by the pressurized electro slag remelting process.The microstructure evolution of quenching a...55Cr17Mo1VN high nitrogen martensitic stainless steel is usually applied to the high-quality mold,which is largely produced by the pressurized electro slag remelting process.The microstructure evolution of quenching and tempering heat treatment were investigated and an optimal heat treatment process to achieve excellent mechanical properties was found out.The main precipitates in the steel included carbon-rich type M_(23)C_(6) and nitrogen-rich type M_(2)N.With increasing austenitizing temperature,the equivalent diameter of the precipitates got fined,and retained austenite content increased significantly when the austenitizing temperature exceeded 1020℃.The fracture mode gradually changed from brittle fracture to ductile fracture with increasing tempering temperature from 200 to 550℃.The experimental steel tempered at 350℃ achieved a good combination of hardness(60.6 HRC)and strength(2299.2 MPa)to meet service requirements.Flake M_(23)C_(6) precipitated along martensite lath boundaries and the secondary hardening phenomenon occurred when the tempering temperature was 450℃.Due to the high nitrogen content,M_(2)N precipitated from the inside of laths and matrix when tempered at 550℃.展开更多
文摘The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.
文摘Thermo-Calc software package (TCP+DICTRA) was used to simulate the carbide transformation process in die steel for plastic. Combined with TEM analysis, the calculated result confirms that the carbide in equilibrium state is M_7C_3 carbide. The dissolution of M_7C_3 carbide in steel is predicted by DICTRA program. It was shown that the temperature remarkably affects the dissolution process of M_7C_3 carbide, but the influence of alloy elements such as manganese and molybdenum can be neglected in this steel.
基金This research was sponsored by the National Natural Science Foundation of China(Grant Nos.U1960203,U1908223,and 51774074)Talent Project of Revitalizing Liaoning(Grant No.XLYC1902046)+1 种基金State Key Laboratory of Metal Material for Marine Equipment and Application(Grant No.HG-SKL(2019)13)the"Innovation&Entrepreneurship Talents”Introduction Plan of Jiangsu Province in 2018.
文摘55Cr17Mo1VN high nitrogen martensitic stainless steel is usually applied to the high-quality mold,which is largely produced by the pressurized electro slag remelting process.The microstructure evolution of quenching and tempering heat treatment were investigated and an optimal heat treatment process to achieve excellent mechanical properties was found out.The main precipitates in the steel included carbon-rich type M_(23)C_(6) and nitrogen-rich type M_(2)N.With increasing austenitizing temperature,the equivalent diameter of the precipitates got fined,and retained austenite content increased significantly when the austenitizing temperature exceeded 1020℃.The fracture mode gradually changed from brittle fracture to ductile fracture with increasing tempering temperature from 200 to 550℃.The experimental steel tempered at 350℃ achieved a good combination of hardness(60.6 HRC)and strength(2299.2 MPa)to meet service requirements.Flake M_(23)C_(6) precipitated along martensite lath boundaries and the secondary hardening phenomenon occurred when the tempering temperature was 450℃.Due to the high nitrogen content,M_(2)N precipitated from the inside of laths and matrix when tempered at 550℃.
