乙烯裂解扭曲片管穿孔失效的原因

Piercing Failure Reasons of Ethylene Cracking Twisted-Tape-Tube

采用化学成分分析、宏观观察、金相观察、能谱分析和X射线衍射分析等方法,对乙烯裂解扭曲片管穿孔失效原因进行了分析。结果表明:扭曲片管穿孔失效是硫化腐蚀造成的;扭曲片管的氧、氮含量高,并有铸造缺陷(疏松)和冶金缺陷(夹杂物),加上工作介质中高的硫、钠含量,使硫在缺陷处滞留和聚集,形成的腐蚀产物与金属镍形成了低熔点共晶Ni-Ni3S2,其在工作条件下变成液体后,使管壁的局部腐蚀加速,最后造成穿孔失效。

Cheroical composition analysis, macroscopic observation, metallographic observation, energy spectrum analysis and X ray diffraction analysis were used to analyze the piercing failure reasons of ethylene cracking twisted-tape tube. The resuhs show that the piercing failure of twisted-tape-tube was caused by sulifide corosion. Some reasons, such as high oxygen and nitrogen content, cast defect （microshrinkage） and metallurgy defect （inclusions） with high sulfur content and sodium content, made sulfur detain and gather at defects positions and forme Ni-Ni3S2 low melting point eutectic, which accelerating local corrosion of internal wall of twisted-tape-tube and causing piercing failure at last.