盐化工风机叶轮早期腐蚀失效的分析与预防

Analysis and Prevention of Premature Corrosion Failure of Blower Impeller for Salt and Chemical Industry

在显微组织和裂纹形貌观察的基础上,分析了盐化工风机叶轮早期腐蚀开裂失效的原因,并提出了预防措施。结果表明:叶轮失效是由在Cl^-作用下的应力腐蚀开裂造成的;在叶轮本体上焊接扰流板后,焊接热循环使靠近熔合线的叶轮本体组织发生了显著变化,二次相的析出导致叶轮本体耐蚀性的降低,进而在工作应力和焊接残余应力联合作用下发生应力腐蚀开裂;叶轮本体上工作应力非均匀分布,越靠近叶轮心部,工作应力越大,越容易引发应力腐蚀开裂;提出了去除靠近叶轮心部4个扰流板的预防措施,经生产验证,此措施可预防叶轮的早期应力腐蚀开裂。

On the basis of microstructure and crack morphology observation,the reason for premature corrosion cracking failure of a blower impeller for salt and chemical industry was analyzed.The results show that the failure of the impeller was due to stress corrosion cracking, which was promoted by chloride ions.The microstructure near the fusion line of the impeller body changed significantly by the weld thermal cycle after welding spoilers on the impeller body.The precipitation of secondary phases led to the degradation of corrosion resistance of the impeller body directly,and then the stress corrosion cracking occurred in the combination of working stresses and welding residual stresses.The working stresses on the impeller body distributed unevenly,that is,the closer to the impeller heart,the greater the work stresses were,and the more easily the stress corrosion cracking happened.A prevention method of removing the 4 spoilers near the impeller heart was proposed.It was verified by on-site application that this method can prevent the premature stress corrosion cracking of the impeller effectively.