输氧管焊缝热影响区环形裂纹产生的部位及原因分析  

Location and Cause Analysis of Ring Cracks in Heat Affected Zone of Oxygen Pipe Welds

作　　者：曹海平[1] 张紫平[1] 

机构地区：[1]大唐国际化工技术研究院有限公司,北京100067

出　　处：《化肥设计》2017年第3期34-38,共5页Chemical Fertilizer Design

摘　　要：某煤炭化工企业在使用NO6600镍基合金管输送氧气的过程中,焊缝附近出现了环状裂纹,造成输氧管线发生泄漏。宏观观察发现,裂纹是沿着平行于焊缝的方向发生的周向贯穿型开裂,裂纹断口整齐,从断裂形态上判断为脆性断裂。利用扫描电子显微镜(SEM)观察可以看出,裂纹断裂是沿着晶界发生的脆性开裂,属于解理性断口。根据输氧管内壁黑色腐蚀产物的成分(EDS)分析,发现在裂纹区域有害元素w(S)高达3.07%~7.87%。XRD分析发现腐蚀产物相主要为FeNi2S4、Ni3S4等硫化物,这就揭示了输氧管环状裂纹的萌生、扩展与断裂的主要内在原因是硫化物应力腐蚀,硫化物的生成引发了合金焊缝热影响区(HAZ)发生了晶界脆化腐蚀,引发裂纹萌生、扩展,输氧管特定的工作条件这个外因促进和加速了裂纹的扩展,最终导致贯穿裂纹的产生。In the use of NO6600 nickel-based alloy tube to transport oxygen in the process,the weld of a coal chemical industry near the ring cracked,resulting in leakage of oxygen pipeline.Macroscopic observation found that the crack was parallel to the weld in the direction of the circumferential through the type of cracking,and the crack fracture was neat.From the fracture morphology,it was brittle fracture.By means of scanning electron microscopy（SEM）,it can be seen that the fracture of the crack was a brittle fracture along the grain boundary,which belongs to the cleavage fracture.According to the analysis of the composition of the black corrosion products in the inner wall of the oxygen pipe,it was found that the harmful element w（S）was as high as 3.07% ~ 7.87%in the crack area.XRD results showed that the corrosion product phase was mainly sulfide such as FeNi_2S_4 and Ni_3S_4,which revealed that the main cause of the initiation,expansion and fracture of the annular crack was that the sulfide stress corrosion and the sulfide formation lead to alloy weld.The HAZ had a grain boundary embrittlement corrosion,which leaded to crack initiation,expansion,and oxygen-specific operating conditions.This external factor promoted and accelerated the expansion of the crack,leading to the formation of crack.

关 键 词：裂纹失效 热影响区 煤气化 氧气管 镍基高温合金 

分 类 号：TQ545[化学工程—煤化学工程]