The effect of drawing speed on temperature rise and microstructure distribution in twinning-induced plasticity(TWIP)steel during wire drawing has been investigated to improve drawability for wire rod applications.Alth...The effect of drawing speed on temperature rise and microstructure distribution in twinning-induced plasticity(TWIP)steel during wire drawing has been investigated to improve drawability for wire rod applications.Although wire drawing process is performed at room temperature,heat is generated due to the plastic deformation and friction at the wire-die interface.The steel wires subjected to the low drawing speed(LD)of 0.5 m/min and the high drawing speed(HD)of 5.0 m/min were analyzed using the numerical simulation and electron backscatter diffraction techniques.Interestingly,the specimens subjected to the HD had a higher drawability by about 18%compared to the LD,which is totally different from the general behavior of plain carbon pearlitic steels.The LD wire had uniform temperature distribution along the radial direction during wire drawing.In contrast,the HD wire had a temperature gradient along the radial direction due to the higher frictional effect at surface:the minimum temperature of 58℃ at center area and the maximum temperature of 143 C at surface area.The higher stacking fault energy of HD wire at the surface area due to the high temperature rise retarded twinning rate,resulting in the prevention of fast exhaustion in ductility in comparison with the LD wires since the earlier depletion of twins at surface area is known as the main reason for the fracture of TWIP steel during wire drawing.Consequently,HD process delayed the fracture strain of wire and increased the uniformity of microstructure and mechanical properties along the radial direction.展开更多
The effects of high drawing speeds on parameters of holey fibers are presented. A holey fiber preform structure was made by using tube-in-tube method and was drawn at high speeds with an aim of mass production to meet...The effects of high drawing speeds on parameters of holey fibers are presented. A holey fiber preform structure was made by using tube-in-tube method and was drawn at high speeds with an aim of mass production to meet the demand of next generation communication systems. Transmission parameters such as numerical aperture and normalized frequency of the fabricated holey fibers have been measured and compared with theoretical values based on effective index method. Although the fabricated holey fibers were not of high quality, the analyses of the parameters have shown promising outlook for fabrication of such fibers.展开更多
Secondary dendrite arm spacing(SDAS),which is an important parameter for solidification structure,has a significant effect on the level of segregation and the time for dispelling micro-segregation.The solidification s...Secondary dendrite arm spacing(SDAS),which is an important parameter for solidification structure,has a significant effect on the level of segregation and the time for dispelling micro-segregation.The solidification structure of billets,poured under different drawing speeds for high-carbon chromium continuous casting and etched by saturated water solution of picric acid,was investigated by OLYMPUS BX51 optical microscope;and the indexes of carbon and sulfur segregation were also determined.It is concluded that the solidification structure consists of fine grain region,columnar region,cross dendrite region and central equiaxed grain region.In the columnar grain region,the SDAS at outer arc of billet is about 30μm bigger than that of inner arc;the SDAS increases with the increasing drawing speed and the indexed of carbon and sulfur segregation change from positive segregation to the negative with the increasing SDAS.The SDAS can be used as an important parameter not only to establish reasonable secondary cooling system and drawing speed but also to judge the level of segregation in the unidirectional solidification region.展开更多
基金This research was supported by National Research Foundation of Korea(NRF-2018R1D1A1B07050103).
文摘The effect of drawing speed on temperature rise and microstructure distribution in twinning-induced plasticity(TWIP)steel during wire drawing has been investigated to improve drawability for wire rod applications.Although wire drawing process is performed at room temperature,heat is generated due to the plastic deformation and friction at the wire-die interface.The steel wires subjected to the low drawing speed(LD)of 0.5 m/min and the high drawing speed(HD)of 5.0 m/min were analyzed using the numerical simulation and electron backscatter diffraction techniques.Interestingly,the specimens subjected to the HD had a higher drawability by about 18%compared to the LD,which is totally different from the general behavior of plain carbon pearlitic steels.The LD wire had uniform temperature distribution along the radial direction during wire drawing.In contrast,the HD wire had a temperature gradient along the radial direction due to the higher frictional effect at surface:the minimum temperature of 58℃ at center area and the maximum temperature of 143 C at surface area.The higher stacking fault energy of HD wire at the surface area due to the high temperature rise retarded twinning rate,resulting in the prevention of fast exhaustion in ductility in comparison with the LD wires since the earlier depletion of twins at surface area is known as the main reason for the fracture of TWIP steel during wire drawing.Consequently,HD process delayed the fracture strain of wire and increased the uniformity of microstructure and mechanical properties along the radial direction.
文摘The effects of high drawing speeds on parameters of holey fibers are presented. A holey fiber preform structure was made by using tube-in-tube method and was drawn at high speeds with an aim of mass production to meet the demand of next generation communication systems. Transmission parameters such as numerical aperture and normalized frequency of the fabricated holey fibers have been measured and compared with theoretical values based on effective index method. Although the fabricated holey fibers were not of high quality, the analyses of the parameters have shown promising outlook for fabrication of such fibers.
文摘Secondary dendrite arm spacing(SDAS),which is an important parameter for solidification structure,has a significant effect on the level of segregation and the time for dispelling micro-segregation.The solidification structure of billets,poured under different drawing speeds for high-carbon chromium continuous casting and etched by saturated water solution of picric acid,was investigated by OLYMPUS BX51 optical microscope;and the indexes of carbon and sulfur segregation were also determined.It is concluded that the solidification structure consists of fine grain region,columnar region,cross dendrite region and central equiaxed grain region.In the columnar grain region,the SDAS at outer arc of billet is about 30μm bigger than that of inner arc;the SDAS increases with the increasing drawing speed and the indexed of carbon and sulfur segregation change from positive segregation to the negative with the increasing SDAS.The SDAS can be used as an important parameter not only to establish reasonable secondary cooling system and drawing speed but also to judge the level of segregation in the unidirectional solidification region.
