H2S,CO2酸性环境中110ksi钢P110,C110套管的应力腐蚀速率

110 ksi钢级C110,P110套管在酸性油气田环境服役过程中受到应力和腐蚀的双重作用,其腐蚀速率与静态的结果不同。如何利用室内试验结果为现场选材提供依据,目前研究尚不充分。采用挂片法、高温高压恒载荷应力腐蚀试验装置和高温高压三点弯曲应力腐蚀试验装置测试了60℃,10MPa,10%（体积分数,下同）H₂S,20%CO₂酸性环境中,P110,C110套管钢分别在自由状态、拉应力以及剪应力状态下的腐蚀速率。结果表明:在酸性环境中,套管钢承受应力作用时会发生应变老化,腐蚀速率显著增大;腐蚀作用在缺口敏感和应力集中部位尤为明显,这些特殊结构部位将形成微裂纹并持续扩展,造成套管钢力学性能和使用寿命降低。本方法适合受应力和腐蚀双重作用下管材腐蚀速率的测试。     

H62黄铜套管环境致裂行为分析

某批H62黄铜套管在装配时发生断裂,采用化学成分分析、宏观分析、光学显微镜和扫描电镜观察等方法对套管断裂原因进行了分析。结果表明:该H62黄铜套管断裂方式为沿晶断裂,是装配过程中的扭曲力、内部残余应力以及环境因素共同作用导致的应力腐蚀开裂。     

60Si2MnA钢弹簧压力试验断裂原因分析

某60Si2MnA钢弹簧在压力试验过程中发生断裂失效,采用断口宏微观分析、扫描电镜及能谱分析、金相分析等方法对其断裂原因进行了分析。结果表明:弹簧表面存在较多的酸洗腐蚀坑,在压力试验过程中成为应力集中点,于腐蚀坑底萌生微裂纹,微裂纹不断扩展最终导致弹簧断裂失效。最后根据弹簧断裂原因提出了改进建议。     

套管滑套出液口部位断裂原因

某套管滑套在进行工具强度和密封性能检测时,其出液口部位突然发生断裂。采用宏观观察、化学成分分析、扫描电镜分析、硬度测试、冲击性能测试、金相检验及有限元分析等方法分析了该套管滑套断裂的原因。结果表明：该套管滑套结构设计不合理,出液口部位存在明显的应力集中,产生了缺口效应;热处理工艺不当使材料的断裂韧度显著降低,最终导致套管滑套出液口部位发生断裂。     

安全阀弹簧失效原因分析与改进措施

弹簧式安全阀是用于催化装置上的重要部件，在常温下露点腐蚀是弹簧式安全阀失效的重要原因。针对大连石化公司二催化装置T302解吸塔塔顶安全阀的失效，利用电子能谱（EDX）、SEM电镜扫描等手段对失效安全阀弹簧进行检测分析，得出安全阀弹簧失效的主要原因是安全阀接触的介质舍有H2S、SO2、H2O，这些介质在30—40℃，常压的务件下在安全阀弹簧的表面形成酸性露点而腐蚀表面形成点蚀坑，这些点蚀坑引起应力集中导致弹簧断裂，并针对具体情况提出解决方案。     

地铁受电弓预调螺杆断裂失效分析

某地铁受电弓预调螺杆在运行过程中发生断裂失效,采用化学成分分析、断口宏微观分析、金相检验、力学性能测试等方法对该螺杆的断裂原因进行了分析。结果表明:在运行过程中螺杆螺母端螺纹连接副表面发生磨损、腐蚀,且螺杆承受交变弯曲载荷作用,导致螺杆发生了腐蚀疲劳断裂。     

某油井油管短节断裂原因分析

某油井生产11个月后发生油管短节断裂失效事故。通过对失效油管短节的宏观和微观形貌观察、显微组织分析、力学性能测试、化学成分分析,查明了其断裂失效原因。结果表明:该油管短节断裂主要是由于在油井生产工况下,油管内壁发生了多裂纹源的应力腐蚀开裂,然后在腐蚀和机械载荷的共同作用下,裂纹不断扩展并相互连接,当裂纹穿透管壁后表现为腐蚀疲劳开裂,最终导致油管短节断裂失效;油管短节加工工艺不当,提高了其断裂失效的概率。     

油田套管P110钢腐蚀的影响因素

油田油套管腐蚀大,影响因素较多,为了提高管道的使用寿命,给油气田的防腐蚀提供理论依据,采用动、静态高温高压釜对油井套管P110钢进行了失重法腐蚀试验,利用SEM,EDS和XRD技术对P110钢的动、静态CO2腐蚀行为进行了研究.结果显示,CO2腐蚀产物膜的主要成分是FeCO3和Fe3C;在每种条件下,温度、CO2分压、Cl-浓度对P110钢的腐蚀速率都有其临界值.     

P110套管螺纹断裂失效分析

某油田开采井使用的P110钢级套管在使用过程中出现断裂失效。使用宏观形貌分析、化学成分分析、金相检验、力学性能测试的方法,结合现场施工过程中失效套管的使用、维护及螺纹端部的使用状况分析,详细分析了套管螺纹断裂失效的原因并提出预防措施。结果表明:该套管断裂性质属于疲劳断裂;套管上卸扣过程中的不规范操作增大了螺纹端局部接触应力,装配过程中套管与接箍螺纹的轴线偏斜导致螺纹间存在间隙,局部接触应力过大导致螺纹面上的金属产生变形和磨损;螺纹旋进阻力增大、下井前仅部分旋入,是造成套管螺纹断裂失效的主要原因。     

3Cr2W8V合金钢轴承套圈用热挤压芯棒断裂失效分析

某3Cr2W8V合金钢轴承套圈用热挤压芯棒发生断裂失效,通过断口宏观分析、化学成分分析、硬度测试、金相检验等方法,分析了其断裂失效的原因。结果表明:该芯棒的结构设计不合理且机加工表面质量不良,在拉-压交变应力和扭转应力复合作用下产生应力集中,于应力集中的过渡圆角部位的夹杂物相处开裂形成疲劳裂纹源,发生早期疲劳断裂。     

Experimental Study on Mechanical Properties Degradation of TP110TS Tube Steel in High H₂S Corrosive Environment

The research on casing corrosion in sour environment by a synergism of sweet corrosion and H₂S corrosion has become the basis of casing selection and casing string safety evaluation with more and more sour reservoirs containing high H₂S concentration being developed. It is essential to scientifically utilize casing service ability and reasonably control production rate of gas well to achieve the effective and safe developing of gas resources during the safety period of casing service with a precise casing life prediction. Scanning electron microscopy and tensile testing were applied to investigate the corrosion of TP110TS tube steel in stimulant solution with carbon dioxide (CO₂) and hydrogen sulfide (H₂S) at variable conditions of P_CO2/P_H2S, temperature and time. This paper especially focused on the degradation of mechanical properties (elastic modulus, yield strength and tensile strength) of test specimens subjected to corrosion. Experimental results suggest that the fracture mode will transit from ductile fracture before corrosion to brittle fracture after corrosion and the mechanical properties will experience obvious degradation when the specimens were exposed to corrosive environment. Service life prediction model of casing was established on the basis of experimental observations and results.     

长庆油田渗氮套管的耐腐蚀性能研究

针对长庆油田油井套管腐蚀问题,采用并评价了真空渗氮工艺.该工艺处理套管表面形成氮化层,在不降低原有机械性能的前提下提高了表面耐磨、抗蚀能力.经室内、现场试验发现,渗氮管在长庆油井腐蚀情况下的耐腐蚀性能优良.此外,还就渗氮层在不同弯曲、拉应力条件下的微观表面变化对使用性能的影响进行了研究,确定了渗氮套管下井条件.并于2003年首次在2口井得以应用.该工艺为低产低渗透油田的防腐蚀研究提供了新思路.     

耐蚀油套管管材的国内外研究现状

世界油气田中大约1/2含有H2S和CO2气体,针对CO2/H2S腐蚀所采取最安全的防护措施是使用耐蚀油套管材料。本文综述了国内外抗腐蚀油套管管材的研究现状,详细介绍了低碳钢、低合金钢、低碳3-5wt.%Cr钢、13Cr和超级13Cr不锈钢的冶金成分、组织结构及抗CO2/H2S腐蚀,特别是抗硫化物应力腐蚀开裂(SSC)的性能。指出了耐蚀油套管管材在CO2/H2S油气田应用的不足之处及在以后研发过程中有待解决的问题。     

Failure analysis of a leak-off oil pipe from injection valves of an off-shore operating diesel engine

The failure analysis of a four-stroke 3000 kW off-shore operating diesel engine is presented. The failure occurred during engine normal operation period in the leak-off oil pipe from the injection valves, which experienced a fracture through the pipe wall and a diesel engine fire as a result. A detailed analysis of all elements which had an influence on the failure initiation was carried out, namely leak-off oil pipe vibration level, pipe stress level, presence of corrosion pits on the pipe external surface under the zinc coating and engine components temperature distribution in the failure zone. It was found that the crack initiation and propagation of the leak-off oil pipe from injection valves was driven by a fatigue mechanism, which was facilitated by loose pipe supports (excessive pipe vibration) and corrosion pits on the pipe surface that acted as stress concentrators. The contact of leak-off atomized oil due to the pipe through wall fracture with the hot engine exhaust muff (390 °C approximately) caused local fire of the diesel engine.     

Analysis on the Rupture Failure of Railway Cross Rails

In this paper the failure of two railway cross rails that ruptured during a simulation test under alternating load was investigated. The railway cross rails were made of alloy steel. Visual inspection found that the macrofracture surfaces of the ruptured rails were very flat without macroscopic plastic deformation, and there were conchoidal structures on the fractures that were covered with corrosion products. These are the typical macrofracture characteristics of corrosion fatigue cracking. Tensile and impact tests showed that the mechanical properties of the steel plates met the proper specifications. Optical microscopy found the microstructure of the steel also qualified. Macrofracture analysis revealed that the two ruptures originated at the transitional line from flat plane to camber area on the outer surface of the steel plates. Microfracture observations showed that there were some machining notches near the rupture origins. It was concluded that there was localized stress concentration near the transitional line that was caused by machining notches or the transition structure from the flat plane to camber or by both. The localized stress concentration induced the initiation of a fatigue crack under alternating load, which propagated by corrosion fatigue under alternating load in a humid atmosphere.     

高速离心泵叶片断裂分析

对高速离心泵断裂叶片的材料成分,断口和力学性能进行了分析,确定了其断裂模式为腐蚀疲劳断裂,叶片根部加工粗糙,造成局部应力集中是导致叶片断裂的主要原因,对叶片的结构设计进行了探讨。     

重卡钢板弹簧断裂失效分析

通过宏观检查、化学成分分析、硬度测试以及金相检验等结果分析。确定了重型卡车用钢板弹簧的断裂原因。结果表明：因超载使钢板弹簧出现过度反弓,造成板簧卡中的螺栓杆与钢板弹簧动态接触．发生磨损腐蚀,形成凹坑．成为应力集中点;在过大的交变应力作用下．应力集中点萌生裂纹并不断扩展．最终造成钢板弹簧疲劳断裂。最后提出了防止其发生断裂失效的预防措施。     

P110石油套管水压试验开裂原因分析

通过对材料的化学成分分析、断口分析及金相检验,对φ177.8 mm×11.51 mm P110石油套管水压试验后出现的管体异常开裂现象进行分析。结果表明:导致管体纵向开裂的原因是该套管管体组织内分布着大型夹杂物,它的存在破坏了材料组织的连续性,削弱了横向抗拉强度,在应力集中的条件下,局部应力超过实际的抗拉强度从而产生开裂。     

钻杆接头台肩根部刺漏失效分析

通过力学性能测试、化学成分分析、金相检验和断口分析等方法对某井发生的钻杆接头台肩根部刺漏失效原因进行了分析。结果表明：材料冲击功低于标准要求,接头台肩根部受到严重腐蚀,形成大而深的腐蚀坑,在交变应力作用下,裂纹萌生于腐蚀坑底部,并迅速扩展,最终导致钻杆接头发生早期腐蚀疲劳失效。     

Inconel 625合金波纹管失效分析

采用化学分析,透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)等微观测试手段对失效波纹管化学成分、力学性能、断口腐蚀产物及断口微观形貌进行综合分析。研究结果表明,波纹管的失效是材料在腐蚀性环境下局部高应力处首先发生高温氧化、硫化腐蚀,产生疲劳裂纹源,在交变应力的作用下发生腐蚀疲劳而造成的。通过降低腐蚀和波纹管应力可以防止或减轻腐蚀疲劳发生,延长波纹管使用寿命。