HAl77-2铝黄铜换热管应力腐蚀开裂

Stress Corrosion Cracking of HAl77-2 Brass Heat Exchange Tube

针对换热管腐蚀泄漏问题,采用金相、扫描电镜、能谱等技术对换热管的腐蚀形貌、腐蚀产物成分进行分析。结果表明:换热管内冷却介质中高含量的氨氮对换热管应力腐蚀开裂起主要作用;管子端部与管板的胀接,使其胀管与未胀过渡区留下了较大的残余应力;换热管选用的HAl77-2铝黄铜管也不适合在含有很高氨氮介质的环境中使用。因此,在腐蚀介质、残余应力、敏感材料三个条件都具备的情况下,换热管短期内发生应力腐蚀开裂而泄漏失效。

The case history of leakage of tubes of a heat exchanger was analyzed in terms of the corrosion morphology and the composition of corrosion products by means of metallographic micro- scope, SEM and EDX. The results show that the high concentration of ammoniacal nitrogen in the cool- ing medium plays an important role for the stress corrosion cracking of the heat exchange tube, while there exists residual stress in the transition zone between the tube with the expanded joint at the tube end. In addition, the HA177-2 brass itself is sensitive to media with higher concentration of ammoniacal ni- trogen. Therefore, the stress corrosion cracking induced leakage of the HA177-2 brass could be ascribed to the presence of the residual stress and the corrosive medium to which HA177-2 brass is sensitive.