The effects of sulfide stress cracking on the mechanical properties and intergranular cracking of P110 casing steel in sour environments

Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on specimens, which were pretreated under the following conditions for 168 hours： temperature, 60 ℃; pressure, 10 MPa; H2S partial pressure, 1 MPa and CO2 partial pressure, 1 MPa; preload stress, 80% of the yield strength （os）; medium, simulated formation water. The reduction in tensile and impact strengths for P-110 casing specimens in corrosive environments were 28% and 54%, respectively. The surface morphology analysis indicated that surface damage and uniform plastic deformation occurred as a result of strain aging. Impact toughness of the casing decreased significantly and intergranular cracking occurred when specimens were maintained at a high stress level of 85% %.

Sulfide Stress Cracking Assessment of Carbon Steel Welding with High Content of H<SUB>2</SUB>S and CO<SUB>2</SUB>at High Temperature: A Case Study

In the oil and gas industry, it has been established that for pipelines fabricated with carbon steels, their limitation is related to H2S and CO2 environments, which is 7 to 10 psia of partial pressure of CO2. Therefore, in carbon steel cracking is shown, after 7 or 10 psia of partial pressure of CO2. The experimental work was performed under static conditions in autoclaves within a pH of 3 to 3.8;partial pressures of 16 - 96 psi for H2S and 15 - 53 psi for CO2, in the temperature range of 25°C - 150°C. It was observed that the average yielding stress used in Sulfide Stress Cracking (SSC) tests decreases with temperature increment. Hydrogen Induced Cracking (HIC) evaluations showed that X52 steel, under conditions, was not susceptible to HIC. Results of SSC did not show indications of cracking after exposure to sour solutions, except for the specimen exposed to high H2S and CO2 content (96 psi of H2S and 53 psi of CO2 of the partial pressure) and high temperature (150°C). Microcracks located between the upper and lower weld beads were also observed. However, the highest average corrosion rate was 0.27 mm/year (10.6 mpy), which occurred in samples exposed to 96 psi of H2S and 53 psi of CO2 at 150°C. Likewise, the highest localized corrosion (severe pitting attack) was obtained at the same environment with a corrosion rate of 4.2 mm/year (167 mpy). The oil and gas industry could use carbon steels pipelines in partial pressure higher than 10 psia.

P110S钢级油管管体断裂原因

某油井P110S钢级油管接箍下方8 m位置处发生断裂,采用宏观观察、化学成分分析、金相检验、扫描电镜和能谱分析、X射线衍射分析等方法对油管断裂原因进行分析。结果表明:该批油管力学性能不稳定,油管断口上的腐蚀产物主要为FeS;油管的强度较高、使用温度较低且质量较大,导致油管内部形成硫化物应力腐蚀开裂。

L245A级钢管在湿H_2S环境下的氢致开裂(HIC)与硫化物应力腐蚀开裂(SSCC)试验研究

管线钢在湿H2S环境下运行必须考虑其抗氢致开裂(HIC)和硫化物应力腐蚀开裂(SSCC)性能,因此,在确保L245A级钢管力学性能合格的前提下,根据NACETM0284—2003和NACETM0177—2005标准,按照L245A级钢管及焊缝所处的不同介质浓度和运行压力设计了8组试验。通过降低介质浓度和运行压力对L245A级钢管在湿硫化氢环境下的抗氢致开裂性能和硫化物应力腐蚀开裂性能(SSCC)进行了试验评定;通过4组试验得出:L245A级钢管在标准湿H2S环境下不会产生氢致开裂,发生硫化物应力腐蚀开裂,在设计条件和工作条件下不发生应力腐蚀开裂的结论。同时笔者对管道在湿H2S环境下的安全运行提出了建议。

X80管线钢焊接接头SSCC研究及数值模拟

硫化氢应力腐蚀破裂(sulfide stress corrosion cracking,SSCC)是制约管线钢应用的主要因素。针对X80管线钢焊接接头进行恒位移硫化氢应力腐蚀试验研究,分别测得母材、焊缝和热影响区的应力强度因子门槛值KISCC和裂纹扩展速率da/dt。通过对X80管线钢焊接接头的金相显微组织、断口形貌观察以及硬度测试,分析了X80管线钢SSCC性能的影响因素。并对WOL试样进行了三维弹塑性有限元分析,得到裂纹尖端应力场分布和氢浓度的分布特征。结果表明,热影响区的KISCC最小,裂纹扩展速率最大,具有较差的抗应力腐蚀开裂的能力,其应力腐蚀试验结果与有限元数值分析相互验证。

国产X70管线钢与焊接接头组织及SSCC性能

输气管道的服役条件多为潮湿环境,输送介质含H2S.随着国产X70管线钢在西气东输工程中的应用,国产高强度管线钢硫化物应力腐蚀开裂(SSCC)性能研究显得尤为重要.为此,测试、分析了国产X70管线钢及其焊缝的组织,进一步采用慢应变速率法(SSRT)研究了H2S对国产X70管线钢及其焊接接头SSCC的影响,国产X70管线钢及其焊接接头在含H2S腐蚀介质中应力腐蚀敏感性随H2S浓度的增加而增加,在H2S质量分数为50×10-400时,母材的脆性系数为19. 9500,焊缝的脆性系数高达59. 1900.若以2500视为安全值,则在H2S浓度为50×10-40时的母材就SSCC而言是安全的,而焊缝却是不安全的.

高强度抗硫管钢的抗硫化氢应力腐蚀影响研究

随着深井、超深井的不断开发,兼顾超高强度和高抗硫性能的抗硫管需求越来越多,而随着钢的强度增加,其抗硫化氢应力腐蚀开裂敏感性也随之增加。基于对低合金钢抗硫化氢应力腐蚀影响机理的认识,通过成分合理设计、超纯净钢冶炼、环形炉加热制度、热处理性能窄幅控制等措施,开发了基于微观组织、析出相、强度、夹杂物、偏析等控制的110 ksi(1 ksi=6.895 MPa)及以上钢级高强度抗硫管产品。

硫化氢应力腐蚀开裂A法试验影响因素探讨

硫化氢应力腐蚀开裂A法试验广泛用于抗硫油套管的产品检验,影响检验结果的除了材料自身性能之外,还有众多因素可能会对检验结果产生影响,如试样加工、试验设备、试验条件、试验后评价等。分析这些影响因素,探讨相关影响因素的解决或控制方法。

X65管线钢焊接接头在H_2S/CO_2环境中抗SSCC性能

我国渤海湾某油田开展了天然气利用项目,天然气外输海管选用国产X65管线钢手工电弧焊接铺设完成。随着油田不断深入开发,外输天然气中H2S含量持续增长,CO2含量高达10%左右,使该海底管线面临着潜在的应力腐蚀开裂风险。参考NACE相关标准,研究了不同工况条件下X65管线钢焊接接头在H2S/CO2环境中的抗硫化物应力腐蚀开裂(SSCC)性能。结果表明,该X65管线钢焊接接头在H2S/CO2环境中抗SSCC性能优良,但在低温偏酸性条件下表现出一定的SSCC敏感性。建议在管线的运维过程中采取措施控制外输温度并尽量降低酸性气体含量,以防止SSCC发生。

L245钢抗SSC、HIC的性能试验

采用NACE TM0284-2003和NACE TM0117-2005实验方法对L245钢进行评定。结果表明:在湿H2S环境下,L245钢具有良好的抗氢致开裂(HIC)和硫化氢应力腐蚀(SSC)的能力。在试验结果基础上,对其腐蚀机理及影响因素进行了讨论。

L245NS抗硫弯管力学性能及HIC和SSC试验分析

对采用感应加热技术生产的L245NS级Φ406.4 mm×10.31 mm抗硫弯管进行了力学性能、氢致开裂（HIC）及硫化物应力腐蚀开裂（SSC）试验评价,并结合了弯管的微观组织特征分析。结果显示,经890~930℃感应淬火＋580~630℃回火空冷后,L245NS弯管强韧性能、HIC试验结果符合标准要求;其中,弯管内、外弧侧管体强度和冲击韧性相对母管均有不同程度的提高;HIC裂纹多形成在贝氏体组织及带状组织周围;在NACE TM 0177—2005试验环境下,L245NS弯管表现出良好的抗SSC性能。

加氢装置碳钢高压空冷器预硫化过程泄漏分析

针对加氢装置碳钢高压空冷器催化剂预硫化时泄漏失效问题,调研不同制造厂高压空冷器管接头的焊接方法、焊接材料、预热和焊后热处理等焊接工艺,分析不同焊接工艺与失效的关系、以及不同标准的差异,并对加氢装置生产运行和催化剂预硫化两种工况进行对比,分析了加氢装置碳钢高压空冷器在预硫化时发生湿硫化氢应力腐蚀开裂的原因,提出碳钢高压空冷器设计、焊接工艺、使用的要求,具有实践指导意义。

X65级海管环缝无衬垫封底全自动焊工艺及焊缝性能研究

在一些国外海洋油气田开发项目中,输送含有酸性腐蚀介质的海底管道环缝焊接强制要求采用无铜衬垫封底焊接技术,确保焊缝在硫化氢(Hydrogen Sulfide,H2S)酸性腐蚀服役过程中不会出现硫致应力开裂(Sulfide Stress crack,SSC)。为解决铜衬垫在封底焊接过程中铜原子受热扩散进入焊缝金属并对其性能产生破坏性影响的问题,采用表面张力过渡(Surface Tension Transfer,STT)封底焊接和熔化极气体保护焊接(Gas Metal Arc Weld‐ing,GMAW)填充盖面焊接技术,开发了一种适用于海管S型铺设的无衬垫封底全自动焊工艺并对焊缝性能进行测试研究。结果表明,横向拉伸、全焊缝拉伸、侧弯、冲击、宏观硬度及H2S腐蚀试验等均满足项目焊接规格书及DNV OS F101(2013)标准要求;焊接接头试样均通过了NACE 0177标准下的硫致应力开裂试验,可应用于含H2S酸性环境下X65级碳钢海管的焊接施工。STT表面张力过渡封底焊接属于单面焊双面成形技术,焊接热输入小,飞溅极少,焊缝成形好,是无衬垫封底焊接技术的一种可靠选择。

C110级油套管钢的显微组织和晶体学特征对硫化物应力开裂的影响

通过单轴拉伸试验即NACE-A法评估了C110级油套管钢的抗硫化物应力开裂(sulfide stress cracking,SSC)性能,对拉伸试验断裂和未断裂的试样进行了金相检验,以揭示显微组织、夹杂物、晶界和位错对C110级油套管钢抗SSC性能的影响。结果表明:断裂试样中的裂纹从夹杂物处萌生和扩展,裂纹附近区域几乎都是变形晶粒,晶粒中心平均取向差较大,从而增大了钢的SSC倾向。未断裂试样中以再结晶晶粒和亚结构晶粒为主,且高角度晶界较多,能有效阻止裂纹的萌生。

微观组织结构对镍基825合金力学性能和硫化物应力腐蚀开裂的影响

目的揭示微观组织结构对镍基825合金硫化物应力腐蚀开裂的影响规律及机理。方法利用金相显微镜(OM)、扫描电子显微镜(SEM)和背散射电子衍射(EBSD)分析了2种镍基825合金的金相组织、夹杂物种类及等级、晶界类型以及残余应变和晶粒尺寸分布。通过显微维氏硬度计评价了合金的力学性能,同时采用氢微印、动态充氢慢应变速率拉伸试验和三点弯曲试验,评估了合金的氢脆倾向和硫化物应力腐蚀开裂敏感性。结果2种镍基825合金的夹杂物均以B类和D类Ti N为主。2种合金中B类夹杂物均以晶界分布为主,D类夹杂物在合金1#中集中分布,在合金2#中随机分布。合金1#中B类夹杂物等级为0.91,D类夹杂物等级为1.4,合金2#中2种夹杂物等级分别为0.54和1.33。氢微印试验发现氢在合金1#的晶内、晶界处均大面积存在,而在合金2#中则分布稀疏。EBSD发现2种合金均为等轴奥氏体,合金1#晶粒尺寸稍大,晶界以随机大角度晶界为主且存在较高的残余应变集中,而合金2#晶粒细小且尺寸分布更均匀,随机大角度晶界和低Σ界面为其主要晶界类型,残余应变分布均匀。合金1#的硬度为184.67HV,屈服强度为285.30 MPa,而合金2#的硬度和屈服强度分别为207.75HV和300.03 MPa。在动态充氢慢应变速率拉伸试验中,2种合金均出现了氢脆倾向,合金1#的断裂延伸率降低了2.6%,而合金2#只降低了1.6%。三点弯曲试验中合金1#表面发生严重均匀腐蚀,出现了以穿晶为主的宏观裂纹,裂纹萌生部位的基体元素显著降低,在其周围还发现了夹杂物及其脱落留下的微孔,而合金2#表面仍有金属光泽,只有微米级的裂纹萌生于应力集中处。结论大量夹杂物的存在降低了合金1#的屈服强度并导致晶界残余应变集中,同时作为有效氢陷阱增加了镍基825合金硫化物应力腐蚀开裂的敏感性。此外,夹杂物与金属基体之间形成微电偶,促进周围金属阳极溶解,进一步增加了合金的开裂敏感性。

乙烯裂解炉对流段LMPH模块进口弯头失效原因分析

某石化企业2#乙烯裂解炉对流段LMPH模块进口弯头发生腐蚀开裂,影响装置正常工作。通过采用宏观检查、化学成分分析、腐蚀产物分析和扫描电镜观察等方法,确定了弯头失效的原因为硫化物和氯化物导致的应力腐蚀开裂,并提出了材质升级和改进弯头焊接工艺等措施。

Effect of pH and applied stress on hydrogen sulfide stress corrosion behavior of HSLA steel based on electrochemical noise analysis

The influence mechanism of pH and the externally applied stress on sulfide stress corrosion cracking behavior based on the joint analysis of the in situ electrochemical noise and microstructure was studied.The results showed that{\mathrm{H}}^{+}in solution changes the composition and structure of corrosion product film by affecting the concentration of{\mathrm{S}}^{2-}and{\mathrm{Fe}}^{2+}near the anode surface.When the pH increased from 2.6 to 3.6 and 4.6,the corrosion product film changed from porous Mackinawite to dense and stable FeS.The change in corrosion product type delayed the crack initiation time by 10.5 and 45.5 h,while the uniform corrosion time was prolonged by 6.1 and 46 h,respectively,delaying SSC behavior.After increasing the applied stress,the local plastic deformation on the material surface increases the porosity and crack rate of the corrosion product film and becomes a fast propagation channel for SSC cracks.When the applied stress is 110%of the actual yield strength of the material,the initiation time of stress corrosion cracking is 6 and 18.1 h earlier than that of 90%and 100%,respectively.The local corrosion time was extended by 23.5 and 8.2 h,respectively,accelerating SSC behavior.

Analysis of cracks origin behaviors during sulfide stress corrosion (SSC) in HSLA steel at different temperatures by electrochemical noise

The sulfide stress corrosion(SSC)behaviors of the high strength low alloy steel at the different temperatures were investigated by the microstructural observation and electrochemical noise(EN)analysis.With the corrosion temperature increasing from 20 to 40℃,SSC ruptured time is prolonged.The increase in corrosion temperature results in the decrease of the saturation solubility of H_(2)S in the solution and thus increases pH value of solution.The increase in corrosion temperature decreases the size of the holes and cracks in the corrosion product film on the surface of the sample,which is due to the formation of the dense FeS corrosion product film.The current kurtosis results indicate that the time for the first occurrence of crack initiation is postponed by the increase in the corrosion temperature.The standard deviation of current noise signals,current kurtosis,power spectral density and energy distribution plot results shows a great consistency,which suggests that EN analysis method can reflect SSC behaviors in real time.

换热器应力腐蚀开裂失效分析

换热器在化工生产中应用十分广泛,发生应力腐蚀开裂是换热器损坏的一个重要原因。某化工厂的一台CO_(2)换热器在检验时,发现管程出口侧有多根换热管发生严重开裂。为查明开裂原因,对换热管进行了取样分析,采取化学成分分析、金相分析、扫描电镜分析和能谱分析等多种方法对试样进行了检测。基于裂纹的宏观形貌和试样的理化检测结果分析,得出换热管开裂的原因是换热管贴胀变形部位在湿硫化氢和氯化物环境下发生应力腐蚀开裂。为保证设备可靠运行,给出了相应的建议。

超级13Cr油套管在含H_2S气井环境下的腐蚀试验

近20年来,在国内外H2S/CO2共存环境、高含Cl-的深井或复杂水平井中,为保障井筒寿命并控制耐蚀合金管柱成本,超级13Cr不锈钢油套管的应用逐步增多,而ISO等标准中对于超级13Cr油套管的适用条件规定严格,特别是在超级13Cr的抗硫化物应力开裂影响因素方面,不同学者研究认识不统一。为此,模拟陕北某区块含H2S气井腐蚀环境,利用电化学系统和高压腐蚀测试系统,评价了超级13Cr油套管的电化学和抗硫化物应力开裂能力。结果表明,在模拟环境下的超级13Cr电化学腐蚀速率为0.01mm/a,而传统13Cr的腐蚀速率为0.26mm/a。同时在抗硫化物应力开裂试验中,加载80%AYS和90%AYS下的超级13Cr没有出现NACE标准溶液试验下的开裂问题。该结果为类似气井环境下的超级13Cr应用提供了一定的参考。