Strain hardening rate dependency of deformation shape,strain distribution,and contact pressure during wire flat rolling

The effect of the strain hardening exponent(n)of a material on the changes in shape,strain inhomogeneity,and contact pressure was investigated during wire flat rolling to understand its effect on the deformation behavior of a flat-rolled wire and to determine the optimal working conditions with materials.The deformation behaviors of wires with various n values were systematically compared using finite element method.The shape of the deformed wire was found to depend on the n value of the material.Both the contact width and lateral spreading of the wire decrease with increasing n,resulting in a large reduction in area with the n value.The strain homogeneity of the wire increases with the n value of the wire.The improvement in the strain homogeneity with the n value is attributable to two factors:a lower strain concentration in the central region and a higher overall elongation as n increases.In addition,the average effective strain of the wire cross section decreases with the n value of a material during wire flat rolling.The contact pressure distribution on the surface of the wire differs significantly depending on the n value.In materials with a low n value,the contact pressure exhibits a higher value at the entry and edge zones of the contact surface.By contrast,materials with high n values exhibit a higher contact pressure at the exit zone.This behavior can be explained by the strain hardening behavior of the material during wire flat rolling.

Effect of reduction in area per pass on strain distribution and microstructure during caliber rolling in twinning-induced plasticity steel

The effects of reduction in area(RA)per pass during caliber rolling on microstructure and strain distribution of twinninginduced plasticity steel have been investigated to find solutions to make a more homogeneous material along the radial direction for wire rod applications.The steel wires subjected to an average RA per pass of 2.5%(skin pass caliber rolling)and 10.0%(conventional caliber rolling)were analyzed.The skin pass caliber-rolled wire was characterized as a duplex fiber texture of major<111>and minor<100>.and the textures were almost same at/between center and surface area,which is totally different from those of conventional caliber rolling and wire drawing.The skin pass caliber rolling led to more homogeneous microstructure and mechanical properties along the radial direction in comparison with the conventional caliber rolling and wire drawing due to the more homogeneous Hall-Petch hardening,dislocation hardening,and texture behavior with area,resulting in higher formability.

Effect of drawing speed on microstructure distribution and drawability in twinning-induced plasticity steel during wire drawing

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.