• Transactions of Materials Processing
• /
• v.17 no.6
• /
• pp.401-406
• /
• 2008

The frictional behavior of stamping process is a function of interface parameters such as sheet and tool material, lubricant, surface roughness, contact pressure, sliding speed etc. Among these parameters the thing that can be controlled by a steel maker is the surface roughness of sheet. In this study, effects of surface roughness on the frictional behavior of steel sheet for automotive were investigated to find out the way to improve the frictional characteristics of steel sheet. The cold rolled steel sheets with various surface roughnesses were prepared for the test. The flat type friction test was conducted with different lubricant conditions. The surface roughness effect on frictional behavior depends on the viscosity of lubricant. The frictional characteristic of steel sheet was influenced by the amplitude of roughness as well as the shape of that.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.102-105
• /
• 2008

To investigate the evolution of deformation texture during cold rolling deformation, cold rolling process on a commercial Al-5% Mg sheet was carried out at different rolling reduction ratio. The evolution of annealing texture in cold-rolled Al-5% Mg sheet was also investigated. The evolution of recrystallization texture during annealing process strongly depends on the rolling reduction ratio before heat treatment. Visco-plastic self-consistent (VPSC) polycrystal model was used to predict r-value anisotropy of the cold-rolled and annealed Al-5% Mg sheets. The change of volume fraction for the major texture components was also analyzed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.140-143
• /
• 2003

The drawbead is an important part in sheet metal forming for automotive part and its effect is affected by various process parameters. Therefore in this study, drawbead friction test was performed at various process parameters - panels (cold rolled and galvanized sheet steel), lubricants (having three different viscosities), bead materials(steel, iron) and surface treatment of bead (Cr plating). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by the nature of zinc coating, viscosity of lubricants, surface treatment of a bead and hardness of coated layer.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.411-414
• /
• 2008

In order to study the effect of lubrication during hot rolling, ferritic stainless steel (FSS) sheet were hot-rolled with and without application of lubrication. The effect of two hot rolling processes on the evolution of texture and microstructure after hot rolling, cold rolling and subsequent recrystallization annealing was studied by means of macro-texture analysis and microstructure observations. After hot rolling, the specimen rolled with lubrication showed rolling textures at the sheet surface, while the specimen rolled without lubrication displayed shear textures in the outer layers of the sheet. Hot rolling with lubrication was beneficial to the formation of strong recrystallization textures at sheet surface. However, hot rolling with lubrication led to the formation of orientation colonies in outer thickness layers of the recrystallized sheet.

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.342-344
• /
• 2007

The resistance spot weldability of surface textured cold-rolled steel sheet was evaluated. One steel sheet(T4.5) showed reduced electrode life with less than 2000 welds, and all other steel sheets(E2.2, E4.5, T2.2) made more than 2500 welds. The carbon imprint test revealed that there is sudden electrode diameter increase around 1700 welds. It is believed that the increased electrode diameter decreased current density, and resulted in decreasing weld electrode life due to small weld button size. It is considered that surface roughness difference may attribute to heating during weld cycle and reduced the weld electrode life.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.03a
• /
• pp.85-88
• /
• 1997

The effect of lubrication on the evolution of the cold rolling texture in low carbon steels was studied by X-ray texture measurement. The cold rolling texture was inhomogeneous through the thickness of the rolling sheet. The type and sharpness of the texture through the thickness and the degree of inhomogeneity were found to be dependent on the friction acting between rolls and the rolled materials. The degree of the through thickness inhomogeneities was higher in the specimen rolled without lubrication. The friction acting on the roll surface led to the formation of the Goss-Orientation in the rolling texture.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.10a
• /
• pp.328-329
• /
• 2007

A study on the texture and the formability after frictional rolled and subsequent heat-treated AA 1050 aluminum alloy sheets have been carried out. The specimens after the frictional rolling showed a very fine grain size, a decrease of <100>//ND, and an increase of <111>//ND textures. The change of plastic strain ratios has been investigated and it was found that they were higher than those of the initial Al sheet.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.4
• /
• pp.103-107
• /
• 1989

The effects of annealing temperature on the magnetic properties (maximum permeability, coercive force and remanence) and mechanical properties (hardness, tensile strength and elongation at rupture) were analyzed using the nondestructive impulsive magnetic analyzer in a medium carbon cold rolled steel sheet. This nondestructive method was very useful for the analysis of magnetic and mechanical properties of materials. As it was known in the literature, the three distinct processes that indicate the recovery, recrystallization, and grain growth of a metal were measured with the non-destructive analyzer.

• Journal of the Korean Society for Heat Treatment
• /
• v.24 no.5
• /
• pp.251-261
• /
• 2011

The changes in microstructure and texture during annealing were examined in a series of 0.015% C-1.5% Mn cold-rolled sheet steels with 0~0.5% Mo. Orientation distribution function data were calculated from the (110), (200), (211) pole figures determined on the rolled plane of cold-rolled and annealed steel sheets. Regardless of Mo content and annealing conditions, martensite volume fraction was less than 1.0%, not affecting the texture evolution. Textural change at the cooling stage after heating at $820^{\circ}C$ for 67 sec was not observed. Increasing the Mo content and annealing temperature markedly strengthened the intensities of ${\gamma}$-fiber texture, resulting in the increase in $r_m$ value. The desirable texture evolution for deep drawability in the 0.5% Mo steel may be mainly caused by the grain refining effect of Mo carbide in the hot-rolled steel sheet.

• Journal of the Korean Society for Heat Treatment
• /
• v.17 no.2
• /
• pp.78-86
• /
• 2004

Effects of the annealing parameters on the formation of ferrites transformed at low temperatures were studied in cold-rolled ultra low carbon steels with niobium and/or chromium. Niobium and chromium were found to be effective in the formation of the low temperature transformation ferrites. The low temperature transformation ferrites more easily formed when both higher annealing temperature and longer annealing time, allowing substitutional alloying elements to distribute between phases, are in combination with faster cooling rate. It was found from EBSD study that the additions of niobium or chromium resulted in the increase in the numbers of high angle grain boundaries and the decrease in those of the low angle grain boundaries in the microstructures. Both granular bainitic ferrite and bainitic ferrite were characterized by the not clearly etched grain boundaries in light microscopy because of the low angle grain boundaries.