冰水機銅管破裂原因探討

Investigation on Cracking of Copper Tubes in a Water Chiller

本文針對一冰水機銅管破裂之原因進行探討。分別進行外觀觀察、材質成分分析、顯微組織觀察、破斷面觀察與腐蝕生成物分析。由觀察與分析結果推論：冰水機銅管破裂分為兩種不同型態，蒸氣區銅管的破損是應力腐蝕破裂，由管外（接觸冷媒）表面的沿晶腐蝕裂紋起始，裂紋以穿晶方式由管外往內延伸，導致銅管破損。冰水機冷卻水區銅管的破損是管內冷卻水與管壁發生局部腐蝕，管壁由內往外局部減薄，最後由機械力作用，產生延性破裂。

This study is to analyze the fracture of tubes, which had been used in a water chiller. The experimental methods included visual observation, composition analyses of both the tube and the corrosion product, observations of microstructure and fractured surface. The results revealed that the fracture mechanism of water chiller’s tubes could be divided into two types. One was stress corrosion cracking in the steam zone of the tube. Initially, the tube outer surface was corroded intergranularly in the corrosive desiccant environment, and finally, the tube was stressed to fracture transgranularly from outer to inner. The other was fracture due to local corrosion of the inner surface of the tube in corrosive chilling water environment. Then, the tube was thinned progressively from inside to outside. Finally, ductile fracture was observed by mechanical stress.