The effect of tempering temperature on the microstructure and mechanical properties of ultra-high strength, copperbearing, low-carbon bainitic steel has been investigated in the experiment. The results showed that the...The effect of tempering temperature on the microstructure and mechanical properties of ultra-high strength, copperbearing, low-carbon bainitic steel has been investigated in the experiment. The results showed that the microstructure was mainly the laths of bainite in the as-quenched steel. The bainitic laths were restored and combined after the steel tempered at various tempera- tures. There were rnartensite/austenite （M/A） islands and numerous dislocations within and between the bainitic laths, while very t-me precipitates of ε-Cu were also observed within the laths. With increasing the tempered temperature from 400 to 600℃, the yield strength （YS） increased from 877 to 957 MPa, whereas the ultimate tensile strength （UTS） decreased from 1020 to 985 MPa. The Charpy V-notch （CVN） varied from 68.5 to 42 J, and the value was minimal for the steel tempered at 500℃. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
To improve the removal efficiency of such submicron inclusions,we designed an argon blowing method for an RH facility based on mathematical simulations.The effect of the argon blowing on the liquid steel flow and the ...To improve the removal efficiency of such submicron inclusions,we designed an argon blowing method for an RH facility based on mathematical simulations.The effect of the argon blowing on the liquid steel flow and the movement of submicron inclusions was studied using the k-ε flow model coupled with the DPM model for inclusion movement based on fluid computational dynamics in FLUENT.It was found that a more uniform argon flow can be achieved in the up-leg snorkel with a new nozzle position and inner diameter,which resulted in a favorable up-lifting and mixing movement.The new design also increased the circulation rate of molten steel in the RH chamber.The increased turbulent kinetic energy and turbulent dispersing rate enhanced the collision probability of submicron inclusions,which results in an improved removal for 0.5-1 μm inclusions.The proposed RH facility could increase the removal rate of submicron inclusions from the original 57.1% to 66.4%,which improves the magnetic properties of non-oriented silicon steel.展开更多
The cold-rolled（75% reduction ratio） Ti-IF（interstitial-free） steels of 1 mm thickness were recrystallized by annealing at 810°C for different times.The microstructure,mechanical properties and phosphorus seg...The cold-rolled（75% reduction ratio） Ti-IF（interstitial-free） steels of 1 mm thickness were recrystallized by annealing at 810°C for different times.The microstructure,mechanical properties and phosphorus segregation at grain boundary were investigated by means of optical microscopy（OM）,tensile testing and field emission transmission electron microscopy（FE-TEM）.It was observed that recrystallization was completed after annealing at 810°C for 180 s.The yield strength and tensile strength decreased as annealing time increased.The FE-TEM observation showed that after the annealing treatment,the grain boundary was broadened and the dislocations with higher density of phosphorus atoms and phosphide at grain boundaries became evident.The amount of phosphorus segregated at grain boundaries increased with annealing time.展开更多
文摘The effect of tempering temperature on the microstructure and mechanical properties of ultra-high strength, copperbearing, low-carbon bainitic steel has been investigated in the experiment. The results showed that the microstructure was mainly the laths of bainite in the as-quenched steel. The bainitic laths were restored and combined after the steel tempered at various tempera- tures. There were rnartensite/austenite （M/A） islands and numerous dislocations within and between the bainitic laths, while very t-me precipitates of ε-Cu were also observed within the laths. With increasing the tempered temperature from 400 to 600℃, the yield strength （YS） increased from 877 to 957 MPa, whereas the ultimate tensile strength （UTS） decreased from 1020 to 985 MPa. The Charpy V-notch （CVN） varied from 68.5 to 42 J, and the value was minimal for the steel tempered at 500℃. 2008 University of Science and Technology Beijing. All rights reserved.
基金Funded by the National Natural Science Foundation of China(No.51804231)the Key R&D Program of Hubei Province(No.2020BAA027)。
文摘To improve the removal efficiency of such submicron inclusions,we designed an argon blowing method for an RH facility based on mathematical simulations.The effect of the argon blowing on the liquid steel flow and the movement of submicron inclusions was studied using the k-ε flow model coupled with the DPM model for inclusion movement based on fluid computational dynamics in FLUENT.It was found that a more uniform argon flow can be achieved in the up-leg snorkel with a new nozzle position and inner diameter,which resulted in a favorable up-lifting and mixing movement.The new design also increased the circulation rate of molten steel in the RH chamber.The increased turbulent kinetic energy and turbulent dispersing rate enhanced the collision probability of submicron inclusions,which results in an improved removal for 0.5-1 μm inclusions.The proposed RH facility could increase the removal rate of submicron inclusions from the original 57.1% to 66.4%,which improves the magnetic properties of non-oriented silicon steel.
基金supported by the National Natural Science Foundation of China under Grant No.50901054
文摘The cold-rolled（75% reduction ratio） Ti-IF（interstitial-free） steels of 1 mm thickness were recrystallized by annealing at 810°C for different times.The microstructure,mechanical properties and phosphorus segregation at grain boundary were investigated by means of optical microscopy（OM）,tensile testing and field emission transmission electron microscopy（FE-TEM）.It was observed that recrystallization was completed after annealing at 810°C for 180 s.The yield strength and tensile strength decreased as annealing time increased.The FE-TEM observation showed that after the annealing treatment,the grain boundary was broadened and the dislocations with higher density of phosphorus atoms and phosphide at grain boundaries became evident.The amount of phosphorus segregated at grain boundaries increased with annealing time.
