A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The ...A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The UHCS produced by this new process has a microstructure with recrystallized ferrite matrix and fine and uniform carbide particles. After this spheroidizing, the UHCS exhibits good mechanical properties at ambient temperature, for example σb= 1 100 MPa, σs =915 MPa, δ=8% and high ratio of σs/σb.展开更多
Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of ...Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength, flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.展开更多
DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and th...DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and the mass fraction of carbon dissolved in the matrix of the steel quenched were investigated. It is discovered that the hardness of the steel increases with quenching temperature in the range of 840-900℃ and remains constant in the range of 900 to 1100℃. It decreases rapidly when the temperature is higher than 1100℃. The mass fraction of carbon dissolved in the matrix of the steel quenched at 840℃ is 0.38, but when the quenching temperature is increased to 1150℃, it increases to 0.98. The carbides formed during sintering are still present at grain boundaries and in the matrix of the steel quenched at low quenching temperatures, such as 840℃. When the quenching temperature is increased to 1150℃, most of the carbides at grain boundaries are dissolved with just a small amount of spherical M23C6 existing in the matrix of the quenched steel.展开更多
The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultra-high carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformatio...The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultra-high carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformation between Acm to Arcm The transformation during deformation is still considered as a diffusion-controlled process. With the increase of time and reduction, the pearlite fraction increased. At the beginning of the transformation, the pearlite was lamelliform. When the rate of reduction was increased to 70%, some of the induced lamellar pearlite was broken up under deformation.展开更多
The 1,000 MPa ultra-high strength hot-rolled plate steel with low-carbon bainitic microstructure was developed in the laboratory for coal mine refuge chamber. The static recrystallization behavior, microstructure evol...The 1,000 MPa ultra-high strength hot-rolled plate steel with low-carbon bainitic microstructure was developed in the laboratory for coal mine refuge chamber. The static recrystallization behavior, microstructure evolution, and mechanical properties of this hot-rolled plate steel were investigated by the hot compression, continuous cooling trans- formation, and tensile deformation test. The results show that the developed steel has excellent mechanical properties at both room and elevated temperature, and its microstructure mainly consists of lath bainite, granular bainite, and ferrite after thermal-mechanical control process （TMCP）. The ultra-high strength plate steel is obtained by the TMCP process in hot rolling, strengthened by bainitic transformation, microstructure refinement, and precipitation of alloying elements such as Nb, Ti, Mo, and Cu. The experimental steel has relatively low welding crack sensitivity index and high atmospheric corrosion resistance index. Therefore, the developed steel has a good balance of strength and ductility both at room and elevated temperature, weldability and corrosion resistance, and it can suffice for the basic demands for materials in the manufacture of coal mine refuge chamber.展开更多
基金Item Sponsored by Provincial Natural Science Foundation of Hebei Province of China (500023)
文摘A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The UHCS produced by this new process has a microstructure with recrystallized ferrite matrix and fine and uniform carbide particles. After this spheroidizing, the UHCS exhibits good mechanical properties at ambient temperature, for example σb= 1 100 MPa, σs =915 MPa, δ=8% and high ratio of σs/σb.
文摘Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength, flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.
文摘DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and the mass fraction of carbon dissolved in the matrix of the steel quenched were investigated. It is discovered that the hardness of the steel increases with quenching temperature in the range of 840-900℃ and remains constant in the range of 900 to 1100℃. It decreases rapidly when the temperature is higher than 1100℃. The mass fraction of carbon dissolved in the matrix of the steel quenched at 840℃ is 0.38, but when the quenching temperature is increased to 1150℃, it increases to 0.98. The carbides formed during sintering are still present at grain boundaries and in the matrix of the steel quenched at low quenching temperatures, such as 840℃. When the quenching temperature is increased to 1150℃, most of the carbides at grain boundaries are dissolved with just a small amount of spherical M23C6 existing in the matrix of the quenched steel.
文摘The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultra-high carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformation between Acm to Arcm The transformation during deformation is still considered as a diffusion-controlled process. With the increase of time and reduction, the pearlite fraction increased. At the beginning of the transformation, the pearlite was lamelliform. When the rate of reduction was increased to 70%, some of the induced lamellar pearlite was broken up under deformation.
基金supported by the National Natural Science Foundation of China (Nos. 51174057 and 51274062)the National High Technology Research and Development Program of China (No. 2012AA03A503)Research Fund for the Doctoral Program of Higher Education of China (No. 20130042110040)
文摘The 1,000 MPa ultra-high strength hot-rolled plate steel with low-carbon bainitic microstructure was developed in the laboratory for coal mine refuge chamber. The static recrystallization behavior, microstructure evolution, and mechanical properties of this hot-rolled plate steel were investigated by the hot compression, continuous cooling trans- formation, and tensile deformation test. The results show that the developed steel has excellent mechanical properties at both room and elevated temperature, and its microstructure mainly consists of lath bainite, granular bainite, and ferrite after thermal-mechanical control process （TMCP）. The ultra-high strength plate steel is obtained by the TMCP process in hot rolling, strengthened by bainitic transformation, microstructure refinement, and precipitation of alloying elements such as Nb, Ti, Mo, and Cu. The experimental steel has relatively low welding crack sensitivity index and high atmospheric corrosion resistance index. Therefore, the developed steel has a good balance of strength and ductility both at room and elevated temperature, weldability and corrosion resistance, and it can suffice for the basic demands for materials in the manufacture of coal mine refuge chamber.
