摘要
对材质为20#钢的液化气管线焊缝区产生裂纹的原因进行了研究。材质化学成分检验结果符合国家标准,无冶金缺陷。对焊缝附近材料进行了取样分析,采用金相检验法检验了试验材料的微观组织及裂纹形态。裂纹起源于管线的内表面热影响区和临近热影响区的母材部位,主裂纹由内壁向外壁扩展,在主裂纹附近有大量的微裂纹。利用扫描电镜和电子探针分析裂纹中的腐蚀产物类型及其分布。研究结果表明,泄漏裂纹出现在焊缝附近,管线开裂是由应力腐蚀引起的,即碱脆所至。应力来源于焊接残余应力,碱洗液NaOH在管线中残存和管线工作温度是产生碱脆的根本原因。防止措施是消除焊接残余应力,减少管线中碱洗液NaOH的残存量,在工艺条件允许时,管线工作温度远离100℃。
The reasons of cracking at welding region of a liquefied petroleum gas pipe of 20# steel was investigated. The results that analyzed 20# steel chemical constitution accorded with national standards and didn't occur metallurgy flaw. With making sampling and analyzing the materials of the region of welding line, metallographic examination checked up microstructure and crack shape of tested materials. Crackle originated from mother metal of inner surface heat-affected zone and of range heated-affected zone of pipe. Main crackle extended from wall to ectotheca and vast microcrack were found near main crackle. Type and distribution of corrosion products of crackle were analyzed by using scanning electron microscopic and electron probe. It was demonstrated that the cracking and leak occurred near a welding line. The cracking resulted from stress corrosion (alkaline brittleness). There are some preventive measures, such as to eliminat residual stress after welding, to reduce the residual of NaOH in the pipe and work temperature of pipe to keep away from 100 centigrade degree if technological conditions permitted.
出处
《石油化工高等学校学报》
CAS
2003年第3期55-57,74,共4页
Journal of Petrochemical Universities
