The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the inter...The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the interference of anodic current(i=0~200 A/m2),main constituents of corrosion products of X80 steel were FeO(OH)and Fe3 O4.A double-layer film formed at i=00 A/m2,in which FeOOH was in outer and Fe3 O4 lied in inner.The formation mechanism of Fe3 O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.展开更多
Submerged arc welding(SAW) and gas metal arc welding(GMAW) experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In ...Submerged arc welding(SAW) and gas metal arc welding(GMAW) experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In GMAW,the inclusions are primarily Ti, Ca, Si, Al, and Mg compounds with no Nb and are generally less than 0.8 μm in size, whereas, in SAW weld, the inclusions are larger, mostly approximately 2-5 μm in size, and are cored with Ca and Ti, exhibiting obvious oxidation metallurgical features.The SAW joint was hot-deformed, and Nb-bearing nano precipitates were newly found in the weld metal through transmission electron microscopy, and Nb-free core-shell inclusion was found through scanning electron microscopy.The inclusions and precipitates were dispersed in or on the boundaries of acicular ferrite, contributing to acicular ferrite nucleation and grain refinement.展开更多
Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local...Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local corrosion of welded joints.A high wall shear stress(WsS)experimental setup was established to conduct the online electrochemical corrosion test.The influence of WRH sizes on local corrosion of welded joints was studied at different flow rates.The electrochemical signals of the local corrosion of X80 welded joints at different flow rates were monitored in real time using electrochemical impedance spectroscopy and wire beam microelectrode.In addition,the corrosion products composition and properties were analyzed.The results show that the micro-turbulent flow fields induced by the WRHs can enhance ion mass transfer near the welded joints.The corrosion products on the WRH surface also present different microscopic morphologies at different flow rates.In strong flow fields,the locally enhanced wsS can peel off the dense corrosion product partially,leading to the electrochemical distribution of large cathode and small anode,which accelerates the occurrence and development processes of the local corrosion of welded joints.The scientific guidelines for the corrosion protection of long-distance oil and gas pipelines can be potentially provided.展开更多
The aim of this study is to evaluate the internal corrosion process on X52 and X80 steels/real petroleum interfaces containing condensed hydrocarbon plus oilfield-produced water,which were subjected to stimulated emul...The aim of this study is to evaluate the internal corrosion process on X52 and X80 steels/real petroleum interfaces containing condensed hydrocarbon plus oilfield-produced water,which were subjected to stimulated emulsions using 50/50 vol ratio mixtures at 45℃,different hydrodynamic conditions,1 h,and 24 h.A washing process by using deionized water was proposed to simulate and identify the corrosiveness of the hydrocarbon phase after 24 h of exposure time.The characterization by electrochemical impedance spectroscopy and the monitoring of the polarization curves indicated that X80 steel/oilfield-produced water interfaces were more susceptible to corrosion than X52 steel exposed to oilfield-produced water.The combined speed rotation of 600 rpm using a magnetic stirrer+600 rpm using a rotating disk electrode decreased the corrosion rate on X52 steel.The stimulated emulsions made of hydrocarbon+oilfield-produced water and hydrocarbon+deionized water at 24 h increased the corrosion rate on X80 steel(0.34 mm/year and 0.43 mm/year,respectively),promoting the formation of erosion and pitting corrosion.These types of corrosion depended mainly on the physicochemical properties of the hydrocarbon,oilfield-produced water,exposure times,and hydrodynamic systems in which the hydrocarbon was studied.展开更多
为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法...为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性.并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响.结果表明,在0℃和-20℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J.其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性.焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体-奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.展开更多
环焊缝的强度匹配形式和耐腐蚀性对管道可靠运行至关重要。文中分别采用低强匹配、等强匹配和高强匹配三种匹配形式对D1219×18.4 mm X80螺旋焊管进行焊条电弧焊,对焊接接头进行抗氢致开裂(HIC)试验,并综合包括化学成分、微观组织...环焊缝的强度匹配形式和耐腐蚀性对管道可靠运行至关重要。文中分别采用低强匹配、等强匹配和高强匹配三种匹配形式对D1219×18.4 mm X80螺旋焊管进行焊条电弧焊,对焊接接头进行抗氢致开裂(HIC)试验,并综合包括化学成分、微观组织、接头强度和韧性等各种因素分析,研究不同强度匹配形式对X80管线钢环焊缝抗氢致裂纹性能的影响。结果表明,三种匹配方式下的X80管线钢焊接接头的抗HIC性能均能满足相关要求,且采用三种强度匹配焊条焊接接头的裂纹长度敏感率(CLR)、裂纹厚度敏感率(CTR)以及裂纹敏感率(CSR)随着匹配强度的升高而升高;焊缝金属的C、P、S含量对HIC敏感性有显著影响,降低这些元素的含量有助于提高焊缝的抗HIC性能;微观组织观察表明,焊缝金属的组织类型和形态对HIC敏感性也有重要影响,热力学平衡且稳定的细小组织是抗HIC的理想组织。展开更多
In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterizatio...In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic nitrate reduction and acidification induced by bacterially-secreted acids. However, the corrosion rate of X80 steel decreased after immersing for ca. 1 week in B. licheniformis culture due to iron biomineralization. This work provides direct insights into the mechanism of microbiologically influenced corrosion of carbon steel by the nitrate-reducing bacterium.展开更多
文摘The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS,AFM and SEM techniques.Under the interference of anodic current(i=0~200 A/m2),main constituents of corrosion products of X80 steel were FeO(OH)and Fe3 O4.A double-layer film formed at i=00 A/m2,in which FeOOH was in outer and Fe3 O4 lied in inner.The formation mechanism of Fe3 O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.
文摘Submerged arc welding(SAW) and gas metal arc welding(GMAW) experiments of Nb-bearing X80 steel were conducted with high-toughness wires.The inclusions in weld metals were analyzed in terms of their types and sizes.In GMAW,the inclusions are primarily Ti, Ca, Si, Al, and Mg compounds with no Nb and are generally less than 0.8 μm in size, whereas, in SAW weld, the inclusions are larger, mostly approximately 2-5 μm in size, and are cored with Ca and Ti, exhibiting obvious oxidation metallurgical features.The SAW joint was hot-deformed, and Nb-bearing nano precipitates were newly found in the weld metal through transmission electron microscopy, and Nb-free core-shell inclusion was found through scanning electron microscopy.The inclusions and precipitates were dispersed in or on the boundaries of acicular ferrite, contributing to acicular ferrite nucleation and grain refinement.
基金support from the National Natural Science Foundation of China(Nos.52206199,42176209,51979282,and 41676071)the Natural Science Foundation of Shandong Province(No.ZR2021MD064).
文摘Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation.The welding reinforcement height(WRH)can induce locally micro-turbulent flow field,which aggravates local corrosion of welded joints.A high wall shear stress(WsS)experimental setup was established to conduct the online electrochemical corrosion test.The influence of WRH sizes on local corrosion of welded joints was studied at different flow rates.The electrochemical signals of the local corrosion of X80 welded joints at different flow rates were monitored in real time using electrochemical impedance spectroscopy and wire beam microelectrode.In addition,the corrosion products composition and properties were analyzed.The results show that the micro-turbulent flow fields induced by the WRHs can enhance ion mass transfer near the welded joints.The corrosion products on the WRH surface also present different microscopic morphologies at different flow rates.In strong flow fields,the locally enhanced wsS can peel off the dense corrosion product partially,leading to the electrochemical distribution of large cathode and small anode,which accelerates the occurrence and development processes of the local corrosion of welded joints.The scientific guidelines for the corrosion protection of long-distance oil and gas pipelines can be potentially provided.
文摘The aim of this study is to evaluate the internal corrosion process on X52 and X80 steels/real petroleum interfaces containing condensed hydrocarbon plus oilfield-produced water,which were subjected to stimulated emulsions using 50/50 vol ratio mixtures at 45℃,different hydrodynamic conditions,1 h,and 24 h.A washing process by using deionized water was proposed to simulate and identify the corrosiveness of the hydrocarbon phase after 24 h of exposure time.The characterization by electrochemical impedance spectroscopy and the monitoring of the polarization curves indicated that X80 steel/oilfield-produced water interfaces were more susceptible to corrosion than X52 steel exposed to oilfield-produced water.The combined speed rotation of 600 rpm using a magnetic stirrer+600 rpm using a rotating disk electrode decreased the corrosion rate on X52 steel.The stimulated emulsions made of hydrocarbon+oilfield-produced water and hydrocarbon+deionized water at 24 h increased the corrosion rate on X80 steel(0.34 mm/year and 0.43 mm/year,respectively),promoting the formation of erosion and pitting corrosion.These types of corrosion depended mainly on the physicochemical properties of the hydrocarbon,oilfield-produced water,exposure times,and hydrodynamic systems in which the hydrocarbon was studied.
文摘为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊.采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性.并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响.结果表明,在0℃和-20℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J.其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性.焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体-奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.
文摘环焊缝的强度匹配形式和耐腐蚀性对管道可靠运行至关重要。文中分别采用低强匹配、等强匹配和高强匹配三种匹配形式对D1219×18.4 mm X80螺旋焊管进行焊条电弧焊,对焊接接头进行抗氢致开裂(HIC)试验,并综合包括化学成分、微观组织、接头强度和韧性等各种因素分析,研究不同强度匹配形式对X80管线钢环焊缝抗氢致裂纹性能的影响。结果表明,三种匹配方式下的X80管线钢焊接接头的抗HIC性能均能满足相关要求,且采用三种强度匹配焊条焊接接头的裂纹长度敏感率(CLR)、裂纹厚度敏感率(CTR)以及裂纹敏感率(CSR)随着匹配强度的升高而升高;焊缝金属的C、P、S含量对HIC敏感性有显著影响,降低这些元素的含量有助于提高焊缝的抗HIC性能;微观组织观察表明,焊缝金属的组织类型和形态对HIC敏感性也有重要影响,热力学平衡且稳定的细小组织是抗HIC的理想组织。
基金financially supported by the National Natural Science Foundation of China (No. 51871026)the National Key R&D Program of China (No. 2017YFF0210404)。
文摘In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic nitrate reduction and acidification induced by bacterially-secreted acids. However, the corrosion rate of X80 steel decreased after immersing for ca. 1 week in B. licheniformis culture due to iron biomineralization. This work provides direct insights into the mechanism of microbiologically influenced corrosion of carbon steel by the nitrate-reducing bacterium.
