| The textured cold-rolled steel sheets have suitable roughness average and peak count, therefore, this kind of sheets can obtain better formability and coating performance. Due to the strong demand for high quality cold-rolled steel sheet with the expansion of the auto industry and appliance manufacturing, the prospect of the textured technology on roller surface is rising. Surface microphotograph of the sheet steel is transmitted from the surface of working rollers. Currently the commonly used textured methods have some disadvantages, steel makers need to develop new ways for roll surface texturing owing to the importance of textured technology.Considering the research actuality at home and abroad, this study designed various texturing methods of pulse electrodepositing chromium. The substrate of electrodepositing was interstitial free (IF) steel. Firstly, the nickel was plated on the IF steel. Secondly, chrome plated with direct current. Thirdly, pulse chromium plated with different pulse parameters. The relevant coating performances, such as roughness average (Ra), peak count (Pc), surface topography, binding force, wear resistance and hardness were measured subsequently. The coating textured effects under different pulse waveform were discussed, and the mechanism of pulse chrome plating texturing was investigated.Four pulse waveforms were used in experiment. They were staircase pulse waveform, square pulse waveform, superimposed pulse waveform and DC superimposed combined with DC pulse waveform. The initial temperature of electrodepositing chromium bath was55℃. The following experiment results can be obtained.After DC superimposed waveform pulse electrodepositing chrome, the coating had a wide range of Ra/Pc. Orthogonal test was employed to improve the results. The range analysis showed that vice-pulse hold time (tb) was the main factor affecting Ra, and main-pulse hold time (ta) was the main factor affecting Pc. After optimization of process parameters, Ra of coating is from1.08μm to3.63μm and Pc is from32.5pks/cm to126.5pks/cm. Observing the morphology of coating by laser scanning confocal microscope, coating surface was composed of hemispherical particles. And the particles were uniform and compact.Improved pulse electrodepositing waveform, using DC superimposed combined with DC waveform pulse chrome plating. Hemispherical crystals have been found in the surface morphology. Ra of coatings changed from1.94μm to3.81μm and Pc was from78.3pks/cm to108.3pks/cm. The relation between Ra and Pc was slight. Other relevant performance of textured coating were also tested, the range of hardness was970～1108HV. Thermal shock test showed that the binding force of coating was good. And wear resistance were also favorable. The thickness and cross-section of coating were measured by scanning electron microscopy, the thickness of chromium coating was over70μm and the combination between coatings was uniform. The structure of the coatings was detected by XRD, the main phase was chromium. And degassing hydrogen heat treatment can remove the hydride effectively.Pulse electrodepositing chrome could get textured morphology on IF steel by adjust the pulse plating waveform and process parameters. The coating surface is composed of hemispherical particles that possesses a wide range of Ra/Pc. Pulse electrodepositing chrome texturing technology have broad application prospect. |
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