共查询到18条相似文献,搜索用时 421 毫秒
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某石油三厂硫磺装置发现,酸性气分液罐液位计管的底部焊缝处发生了明显的开裂泄漏,通过对液位计进行宏观及低倍分析、材质分析、金相检验以及电镜分析结果表明:液位计管和法兰材质均为S20430不锈钢(200系列);液位计管、法兰以及焊缝的金相组织分别为奥氏体、敏化倾向的奥氏体、铸态奥氏体和少量铁素体;液位计管的开裂失效性质为应力腐蚀,以穿晶扩展为主。造成液位计管与法兰焊接处发生开裂的主要原因为液位计管和法兰采用的均为对应力腐蚀较为敏感的材质,两者焊接区存在残余应力,液位计管底部是一个封闭区,存在酸性介质(H2S溶液和H2CO3溶液)。 相似文献
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某0Cr12Mn5Ni4Mo3Al不锈钢自锁螺母在服役过程中出现开裂。对开裂螺母进行了宏观和微观断口形貌观察、表面能谱分析、显微组织及力学性能分析与测试等。结果表明:该螺母开裂原因为应力腐蚀开裂(SCC)。裂纹起源于法兰面与螺母体交接处,螺母体与法兰面呈直角此处易积液,螺母表面处理方式为钝化和涂MoS2,其耐蚀能较差。在腐蚀性潮湿大气环境中,干湿交替作用下螺母产生局部腐蚀点,在腐蚀点处萌生裂纹,裂纹在螺母圆周切向拉应力作用下扩展直至螺母开裂。 相似文献
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以沸水堆堆芯围板焊接热影响区应力腐蚀开裂为例进行了裂纹扩展评估研究.采用有限元模拟与试验检测数据验证相结合的方法对焊接热影响区焊接残余应力场及应力腐蚀开裂扩展过程进行模拟.通过有限元方法计算了应力腐蚀开裂裂纹尖端应力强度因子,再根据应力腐蚀裂纹扩展试验数据获得裂纹尖端应力强度因子与裂纹扩展速率的关系,最终预测了沸水堆堆芯围板的使用寿命,解决了重大构件基于应力腐蚀开裂失效的安全评估问题.该研究过程为重大构件的腐蚀疲劳裂纹失效的安全使用提供了可借鉴的方法. 相似文献
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对304不锈钢氩弧焊焊接接头表面作了喷丸处理,并在金相显微镜与扫描电镜下对处理后材料表面的微观组织进行了观察,用X射线应力衍射仪测试了喷丸处理后试样的残余应力分布,并进行了NaC1水溶液应力腐蚀试验.结果表明,304不锈钢焊缝在NaCl溶液中具有明显的应力腐蚀开裂敏感性,喷丸处理能够很好地提高焊接构件抗应力腐蚀开裂能力;应力腐蚀裂纹断口表现为脆性断裂,各区的应力腐蚀裂纹属于穿晶型裂纹. 相似文献
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某液化石油气贮罐在定期检验中,发现其焊缝内表面存在大量裂纹,通过材质、硬度、宏观、金相等方面的分析,表明,裂纹属于典型的应力腐蚀开裂。通过对应力腐蚀机理、介质环境、应力水平等方面的探讨,分析了该罐发生应力腐蚀开裂的成因,并针对开裂原因有针对性的提出了一些防范措施。 相似文献
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对检修过程中发现的304不锈钢焊缝裂纹及母材本体裂纹进行分析,焊缝存在较多的焊渣,以及根部未焊透是焊缝开裂的原因。母材的金相分析表明,304不锈钢晶界存在碳化物聚集,容易发生晶间腐蚀,引起母材开裂,焊接过程中,多层多道焊也容易使得热影响区晶间腐蚀加剧,引起母材开裂。304不锈钢锻造法兰的制造过程中应避免在敏化温度停留时间过长,固溶处理时应采取快冷的方式避免晶间腐蚀。焊接返修过程中,通过严格控制焊接层间温度,采用快速小热输入的工艺参数使得返修后的304不锈钢焊接质量检验合格。 相似文献
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Stress corrosion cracking of steels in liquid ammonia The apparatus developped for the investigation of stress corrosion cracking of steel in liquid ammonia under controlled electrochemical conditions is described. The parameters of the experiments were set by a computer which also stored and correlated the experimental data. Cylindrical samples of the welding steel W. Nr. 1.0143 and of the steel STE 355 (W. Nr. 1.0562) in liquid ammonia containing ammonium chloride or lithium perchlorate as the electrolyte developped cracks only at negative electrode potentials in the regions of active dissolution and hydrogen deposition. Other parameters including contamination of the solution by air were unimportant. The results are explained by hydrogen induced stress corrosion cracking. No embrittlement was observed with passive samples. However, ultimate tensile strengths in liquid ammonia were clearly lower than at air also for samples breaking without formation of cracks. Experiments with notched sheets resulted in sharp, essentially transcrystalline cracks. Passivation of these samples was difficult in the region of the notch indicating the danger of anodic stress corrosion cracking. 相似文献
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ABSTRACTStress corrosion cracking is one of the aging phenomena for the major structure components in nuclear power plant. During the operation of a power plant, stress corrosion cracks are initiated and grown especially in dissimilar weldment of primary loop components. Among the three factors (susceptible material, residual stress, and corrosive environment) which make the SCC, the residual stress becomes a critical factor for stress corrosion crack when it is difficult to improve the material of the components and their environment under operating conditions. In this study, stress corrosion cracks were artificially produced on STS (stainless steel) 304 pipe itself by control of welding residual stress. The instrumented indentation technique and 3D finite element method (FEM) analysis (using ANSYS 12) were used to evaluate the residual stress values in the GTAW area. As the result of both FEM analysis and experiment, the stress corrosion crack was quickly generated and could be reproduced, and controlled by welding residual stress. Also non-destructive evaluation signals by Acoustic Emission will be discussed for the initiation and growth of SCC.This paper is part of a supplementary issue from the 17th Asia-Pacific Corrosion Control Conference (APCCC-17). 相似文献
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对某电厂开裂失效的不锈钢丝编制的空气滤网的分析表明:其开裂是由晶间腐蚀和应力腐蚀联合作用引起的开裂.主裂纹是应力腐蚀裂纹,不锈钢丝冷加工残余拉应力及环境中Cl离子的存在是不锈钢丝发生应力腐蚀开裂的主要原因.而用材不当,导致发生了晶间腐蚀.晶间腐蚀作为裂纹的起源,诱发并促进了不锈钢丝的应力腐蚀开裂.
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目的对氢气管道内表面开裂原因进行分析,为同类型管道的失效提供参考。方法针对设计压力4.8 MPa、设计温度50℃并在1998年投用的氢气管道,观察其宏观形貌,通过拉伸试验和硬度测试分析其力学性能,并对其进行金相组织分析和扫描电子显微镜观察,通过能谱测试分析其腐蚀产物成分。结果管壁没有明显的腐蚀减薄。管壁整体力学性能符合标准,被测试样韧性较好,未发生材质劣化。基体微观组织为正常的铁素体+珠光体,组织分布均匀,三通及弯管处的焊缝区出现了部分马氏体组织,容易诱发硫化物应力腐蚀开裂的发生。管道内壁存在裂纹及点蚀坑,裂纹扩展较深,且存在分叉,是典型的应力腐蚀特征;点蚀坑有聚集现象,有形成微裂纹的趋势。管道内壁存在腐蚀产物,说明输送的介质不纯净;腐蚀产物中含硫元素,说明介质中含有硫化物等杂质。结论管道操作压力较高,结合其他应力与介质的共同作用,导致管道内壁发生了硫化氢应力腐蚀开裂。 相似文献
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针对国产脉动真空灭菌器内腔焊缝处多次开裂现象,围绕焊接残余应力及消除方法进行了系列研究.根据市场上灭菌器异种钢间断角焊缝特征设计了7种组合结构焊板,应用X射线法定量给出了残余应力分布规律,并对用焊后浇水速冷处理工艺消除残余应力的尝试进行了试验验证.结果表明,各种焊板残余应力均达到屈服应力,由此引起的应力腐蚀与腐蚀疲劳是灭菌器内腔开裂的直接原因;二氧化碳焊接工艺残余应力较焊条电弧焊高10%~22%,残余应力与加强筋类型基本无关;浇水速冷处理工艺可有效降低表面残余应力,降幅达50%~70%,提高疲劳极限12%~14%.有效降低焊接残余应力是解决内腔开裂的重要途径. 相似文献
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Could surface layers and material embrittlement be among the causes of stress corrosion cracking? Neither the hypothesis claiming rupture of the surface layer nor the embrittlement theory yield a sufficiently consistent explanation of the susceptibility to stress corrosion cracking, since the latter can occurr even in the absence of such layers (e.g. brass in copper nitrate and copper tetrammine salts). An indispensable condition for stress corrosion cracking to occurr is the possibility that cathodically active zones are formed by corrosion products at crevices and cracks; such active zones amy be formed e.g. by Cu2O or by dissolved and redeposited noble metals. This phenomenon would also account for the specific action of certain agens: local formation or deposition of corrosion products which are not dissolved again (as e.g. noble metals may be dissolved with complex formation). The susceptibility to stress corrosion cracking is increased by mixed crystal formation, because this process enhances reactivity at grain boundaries, inner defects and creeping zones. In the case of alloys containing no noble metals, however, it is difficult, to predict susceptibility to stress corrosion cracking. 相似文献