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The effects of bead surface roughness on friction, die pickup, and sheet surface damage in the drawbead test were investigated. Beads of HRC 58 hardness were prepared from centerless-ground rod by circumferential honing to 0.05 μm roughness, followed by finishing with 100, 400, or 600 grit SiC paper in the axial direction. Paraffinic base oils with viscosities of 4.5, 30, and 285 mm2/s were used neat and in conjunction with stearic acid. The effects of bead roughness depended on the nature of metal transfer, especially its distribution and firmness of attachment. The presence of a boundary additive increased, decreased, or had no effect on friction depending on the particular coating and bead finish.

Details of the development of metal transfer and friction were studied by drawing cold-rolled bare, galvannealed, electrogalvanized, and hot-dip galvanized strips with a mineral-oil lubricant of 30 cSt viscosity at 40 C, over a total distance of 2500 mm by three methods. An initial high friction peak was associated with metal transfer to the beads and was largest with pure zinc and smallest with Fe-Zn coatings. Insertion of a new strip disturbed the coating and led to the development of secondary peaks. Long-term trends were governed by the stability of the coating. Stearic acid added to mineral oil delayed stabilization of the coating and increased contact area and thus friction with pure zinc surfaces. The usual practice of reporting average friction values can hide valuable information on lubrication mechanisms and metal transfer.

This study was undertaken to examine the role of tool finish orientation on the drawing of zinc-coated steel sheets. Beads of average roughnesses of 0.1 μm and 0.2 μm, finished parallel to and perpendicular to sliding, were used in the drawbead test. Lubrication was provided by unblended base oils of 4.5, 30, and 285 mm2/s @ 40°C, used neat and with a boundary additive, 1% stearic acid. Three types of coated sheet (galvannealed, electrogalvanized, and hot-dip galvanized) were compared to bare AKDQ steel sheet. Results show that lubricant viscosity had the greatest effect on friction, while bead finish orientation and coating type influenced the nature of metal transfer and the galling of the strip. Mixed-film lubrication dominated with the medium and heavy lubricants, here contact area and friction were reduced with increasing lubricant viscosity.

The increased use of zinc coatings on steels has led to a decrease in their weldability. Weld current and time need to be increased in order to achieve sound welds on these materials compared to uncoated steels, and electrode tip life suffers greatly due to rapid alloying and degradation. In this work, typical uncoated Class II electrodes were tested along with a TiC metal matrix composite (MMC) coated electrode. Tests were conducted to study the weldability and process of nugget formation for both electrodes on HDG (hot dipped galvanized) HSLA (high strength low alloys) steels. Current and time ranges were constructed for both types of electrodes by varying either the weld current or weld time while holding all other parameters constant. Analysis of weld microstructures was conducted on cross-sectioned welds using SEM (scanning electron microscopy). Using the coated electrodes reduced weld current and times needed to form MWS (minimum weld size) on the coated steels.

TiCP/Ni coating has been deposited onto the electrodes by electro-spark deposition to improve electrode life during resistance welding of Zn-coated steels. However, welding results revealed that molten Zn penetrates into coating through the cracks and then reacts with substrate copper alloy to form brasses. In the present work, laser treatment was performed on the TiCP/Ni coated electrodes to eliminate cracks formed in the as-deposited TiCP/Ni coating. In addition, a multi-electro-spark deposition of Ni, TiCP/Ni and Ni has also been carried out to improve coating quality. On the other hand, a TiB2 coating was also investigated. those coatings were characterized by electro-microscopy, energy-dispersive X-ray analysis, X-ray diffraction and micro-hardness tests. The results showed that cracks within the as-deposited TiCP/Ni coating could be eliminated with the use of laser treatment or a multi-layer deposition process.

Strict environmental regulations are driving the automotive industry toward electric vehicles as they offer zero emissions. A key component in electric vehicles is the electric motor, where the stator and rotor are manufactured from stacks of thin electrical steel sheets. The electrical steel sheets can be cut in different ways, and the cutting methods may significantly affect the fatigue strength of the component. It is important to understand the effect of the cutting processes on the fatigue properties of electrical steel to ensure there is no premature failure of the electric motor resulting from an improper cutting process. This investigation compared the effect of three different edge preparation methods (stamping, CNC machining, and waterjet cutting) on the fatigue performance of 0.27mm thick electrical steel sheets. To investigate the effect of the edge finish on fatigue behavior, surface roughness was measured for these different samples.