本研究選用304型不鏽鋼與純銅，以脈衝式雷射銲接進行對接接合，以田口方法設計出4項控制因子，3項水準，建立出L9(34)直交表，研究不同參數對於銲道品質、微觀結構與機械性質之影響，並利用各組之抗拉強度大小，以田口方法之望大特性找出最佳參數組合，並以最佳組合之參數進行對接，以抗拉強度作為判斷依據，是否為最佳參數。在銲接實驗後，進行目測檢驗銲道外觀，初步發現參數5、7、8之銲道正與背面產生裂痕，其餘參數之試片皆無裂痕產生。觀察金相微觀組織，觀察銲道之斷面，發現部分參數之斷面接合狀況不佳，因雷射銲接之特性，不鏽鋼之斷面顯示晶粒細化，並延晶界邊緣裂開，但不鏽鋼與銅具有良好之接合。透過微硬度試驗，銲道中的不鏽鋼與銅皆受到雷射能量導致晶粒細小與再結晶，硬度略降低，平均為137 HV，不鏽鋼母材硬度約204 HV，銅母材硬度約93 HV。數據顯示參數之改變對於硬度變化之趨勢並無顯著影響。透過田口方法之望大特性方程式，當雷射能量為10.5 J時，最佳參數組合為重疊率60 %、焦點偏移距離0.2 mm、焦點高度為對焦在材料表面，銲槍偏擺為4 °，以此參數所測得之抗拉強度為203 MPa，約銅母材強度74.2 %。其金相組織顯示不鏽鋼與銅接合狀況良好，無發生凝固裂紋之現象，根據破壞斷面之SEM圖發現有酒窩狀結構，屬於延性破壞，也可觀察到部分區域仍有原材料斷面形貌，此現象造成抗拉強度值略比參數3號低。

This study selected 304 stainless steel and pure copper, which were butt-welded using pulsed laser welding. The Taguchi method was employed to design four control factors with three levels, resulting in an L9(34) orthogonal array. The study investigated the effects of different parameters on weld quality, microstructure, and mechanical properties. By evaluating the tensile strength of each group, the Taguchi method's "larger-the-better" characteristic was used to identify the optimal parameter combination. The tensile strength served as the criterion for determining whether the parameter combination was optimal. After the welding experiments, visual inspection of the weld appearance showed that cracks appeared on the front and back of the welds for parameters 5, 7, and 8, while no cracks were found in the welds of the other parameters. Microstructural analysis of the weld cross-sections revealed poor joint conditions for some parameters. Due to the characteristics of laser welding, the stainless steel's cross-section showed grain refinement with cracks along the grain boundaries, but the stainless steel and copper exhibited good bonding. Through microhardness testing, it was observed that both stainless steel and copper in the weld zone underwent grain refinement and recrystallization due to laser energy, resulting in a slight reduction in hardness, with an average of 137 HV. The hardness of the stainless-steel base material was approximately 204 HV, and that of the copper base material was about 93 HV. The data showed no significant trend in hardness variation with parameter changes. According to the "larger-the-better" characteristic equation of the Taguchi method, the optimal parameter combination was achieved with a laser energy of 10.5 J, an overlap rate of 60 %, a focal offset of 0.2 mm, a focal height focused on the material surface, and a welding torch oscillation angle of 4 °. The tensile strength measured under this parameter combination was 203 MPa, which is approximately 74.2 % of the copper base material strength. The metallographic structure indicated good bonding between stainless steel and copper, with no occurrence of solidification cracks. Based on SEM images of the fracture surface, dimple-like structures were observed, indicating ductile fracture. Some regions still showed the original material's fracture morphology, which slightly lowered the tensile strength compared to parameter 3.

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