本研究目的為探討在鎂合金AZ61上，塗覆不同氧化物活性助銲劑（TiO2、ZrO2、Fe2O3），以不同塗覆量、不同銲接電流下，對銲道所造成的影響。在進行銲接時，記錄銲道的熱影響區溫度變化。銲接後切取試片進行深寬比的量測、顯微組織的觀察、微小硬度的量測與EDS銲道成份分析。
結果顯示，氧化物活性助銲劑在適當塗覆量下與較大銲接電流中均可使銲深寬比增加，TiO2粉末增加幅度較大，在來依次為Fe2O3與ZrO2粉末，每種助銲劑能增加深寬比的塗覆量有一極限值，超過此一極限值則深寬比開始下降。
銲道溫度量測結果指出，添加氧化物活性助銲劑皆會造成銲接時入熱量的增加，由此可推測電弧壓縮理論與陽極斑點理論為影響氧化物造成鎂合金深寬比增加的因素之一。硬度量測結果指出，助銲劑的使用會造成硬度值下降，推測銲接入熱量的增加造成銲道內晶粒成長。由SEM觀察可知，助銲劑粉末的種類與銲接入熱量為決定助銲劑是否殘留於銲道中的重要因素。

關鍵字：鎂合金、氬銲、助銲劑、入熱量

The effects of fluxes (TiO2, Fe2O3, ZrO2) with different painting quantity and welding current on the weldability of magnesium alloy were investigated. The effects of chemical of composition of fluxes on the geometry of welding pool and the variations of welding temperature of HAZ were measured during welding. The depth-to-width ratio, heat input, microstructure, microhardness of specimens were measured. The chemical compositions of weld bead were obtained by EDS.
The results show that the penetration and depth-to-width ratio increase with using an optimal thickness of oxide activating fluxes. Significant increment in penetration was obtained with TiO2. Less ZrO2 could reach no significant affectivity under the higher welding current.
The results show that the heat inputs of weld increase the application of with the oxide activating flux. Both the contraction of the arc and anode spot contraction model are the mechanism to increase the depth-to-width ratio.
The result of microhardness measurement shows a hardness reduction when active fluxes were used in the weld zone. The mechanism is agreed with growth of the grain size due to the increscent of heat input with the active flux.

Key word：magnesium alloy、TIG、flux、heat input

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