| Summary: | 碩士 === 國立屏東科技大學 === 車輛工程系所 === 100 === The purpose of this thesis is to investigate the coloration process analysis for 304 stainless steel using fiber laser. This paper is mainly divided into three parts. First, the laser processing parameters on the coloration developments on surface of stainless steel will be investigated. The processing parameters include laser power, scanning velocity, pulse frequency, and line spacing. The coloration obtained by different laser processing parameters will be identified their RGB values and be converted to the XYZ system via the CIE formula. The main wave length for color will be analyzed via the chromaticity diagram to find the coloration variation trend. Secondly, how the surface morphology of the base metal oxide formed by laser coloring treatment affect the coloration will be also discussed. Besides, the refractive index and the angle of refraction for the metal oxide could be derived by the thin-film interference theory. Finally, the laser induced thermal deformation for 304 stainless steel sheet in coloring processing will be investigated.
The experiment results indicated that laser power is the most important parameter for the laser coloring processing. When the laser power is less than the energy threshold, the coloration variation process would be not visibly occur on the stainless steel surface. Moreover, by the analysis of the chromaticity diagram, the laser scanning velocity and pulse frequency could indirectly influence the lightness of the color. Besides, laser line distance and overlapping percentage of laser spot also significantly affect the color variation due to the thermal accumulation effect. In order to analysis the surface morphology of the work piece treated by laser coloring, an atomic force microscopy will be used to measure the surface roughness. The results showed that the green color could obtain the least roughness then the other four colors. Finally, it could be found that color white induced the smallest thermal deformation of the steel sheet in laser coloration processing. It implied that the work piece marked the beautiful color code or pattern will take the risk to increase the thermal deformation, and coding or marking on with color white could effectively improve processing efficiency and avoid causing larger thermal deformation.
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