| 摘要: | 在車輛工業最常用的就是6061-T6鋁合金，其最常應用的焊接方式為惰氣鎢極電弧銲接及真空硬銲，而現今各種規範都只針對熔融銲接的方式來做疲勞的壽命評估，所以本研究就針對惰氣鎢極電弧銲接(TIG)及真空硬銲(VB)探討兩種不同銲接方式的機械性質分析，經由硬度測試、拉伸、疲勞及金相的觀察，來探討兩種機械性質的差異性，並進一步探討現有規範的適用性。由金相及微硬度測試的分析，可以發現惰氣鎢極電弧銲熱影響區影響寬度約為銲道的寬度。而真空硬銲由於在長時間高溫的環境下，VB母材受到退火的影響使得析出硬化成份成長粗化，造成硬度下降，由於材料及銲道擴散層都為平均加熱，所以硬度並無明顯的差異，硬度與惰氣鎢極電弧銲的熱影響區相近；由拉伸及疲勞測試可發現，在惰氣鎢極電弧銲接受拉伸及疲勞的斷裂點不同，拉伸斷裂點於強度最弱的熱影響區，疲勞斷裂則是在缺陷最多易產生裂縫成長的銲道。在真空硬銲方面拉伸及疲勞斷裂點皆為銲接擴散層，由於材料強度並無明顯的變化，因此最容易在產生缺陷的位置造成破壞。在與各規範比較發現，惰氣鎢極電弧銲在低週疲勞104循環下的應力範圍與IIW預測最為接近，但是各規範越到高週壽命預估與實際實驗差距越大有過度保守的趨勢。尤其是Euecode 9規範評估最為保守。而真空應銲由於銲接品質受到多種因素的影響如硬銲持溫時間及銲接固定壓力，造成銲接品質不均，使得疲勞性質離散度大，無法從規範中穩定評估。The 6061-T6 aluminium alloy is commonly used in automobile industry, and inert gas tungsten arc (TIG) welding and vacuum brazing(VB) welding are the most popular to be applied. Nowadays, the existing regulations only focuses on the specific fatigue assessment of melting welding. As a result, the study analyzes the differences of mechanical properties of inert gas tungsten arc (TIG) welding and vacuum brazing(VB) welding through hardness test, static fatigue test, tensile test, and metallographical observation and investigates the applicability of existing regulations as well.According to the analysis of metallographical and hardness tests, the result is discovered that the influenced width of inert gas tungsten arc (TIG) welding is almost equal to the width of welding, whereas the base material of vacuum brazing(VB) welding exposes in hot environment for long time to annealing, precipitation hardening phase grows, which decreases the hardness; in the meanwhile, the material and welding diffusion layer are heated equally, so there is no obvious differences of hardness with heat affect zone of inert gas tungsten arc (TIG) welding. The breaking point of tensile and fatigue of gas tungsten arc (TIG) welding is different from the tests. The break of tensile test occurs in heat affect zone whereas it appears in the weak welding fulled with cracks in fatigue test. However, for vacuum brazing(VB) welding, the breaking points of tensile and fatigue both occur within welding diffusion layer. Since there is no significant differences of strength of the material, the damages appear within the positions where the weaknesses will grow easily.Compared with each regulation, the prediction of inert gas tungsten arc (TIG) welding is in accordance with IIW within the stress range of lower cycle 104, but the trend becomes conservative for every regulation has hugh differences between higher cycle prediction and results from experiment, and this can be seen the most from the regulation prediction assessment of Euecode 9. On the other hand, the vacuum brazing(VB) welding can be not be stable predicted since it is easily influenced by properties such as the time length of holding temperature and the fixed pressure, the quality is unstable and the statistics of fatigue is distributed differently. |
