| Summary: | 碩士 === 國立交通大學 === 工學院精密與自動化工程學程 === 101 === In this thesis, the various laser parameters –Nd : YAG– that are the power and the focal depth of laser are investigated into the mechanism and microstructure properties of the welding trajectory in the frame of galvanized steel plate.
Firstly, according to the tensile experiment result, there could be seven conditions, which are the 1100(w), 1050(w), and 1000(w) of laser power and the laser focal depth such as 2, 1.5, 1, and 0 obtained the better strength of weld.
Secondly, according to metallographic test result, the microstructure organization of galvanized steel plate in the different parameters of weld and base metal material are both same, as Ferrite. In the laser welding process, the frame of galvanized steel plate was only welded partly in the highly temperature condition and not solidified. This crystal size of welding would affect its hardness, anti-tensile strength, and mechanical property.
Finally, regarding the micro-hardness test result, the center position of weld trajectory after welding, due to its cooling rate is faster than other positions, therefore, its hardness is so too. On the other hand, relative to its center, the hardness of other positions is more weakly. According to the figure of hardness distribution curve, we found that the size of weld trajectory on the experimental specimens is quite small and its width is below one millimeter.
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