Mechanical Properties and CO2 Corrosion Behavior of High Strength and Toughness X80 Pipeline Steel

A type of X80 grade high strength and toughness pipeline steel was designed and researched. The strengthening mechanism of the steel was analyzed by SEM, TEM and XRD, and the CO2corrosion behavior of the steel was simulated by high-temperature and high-pressure autoclave. The result shows that the microstructure of the base metal is mainly acicular ferrite with a small amount of granular bainite. Acicular ferrite consists of laths which occlude and interweave with each other, and there are many dislocation and carbonitrides distributing in acicular ferrite, which made the pipeline steel have good strength and toughness. Under the simulation of the actual working conditions, the activity of reactants is low at 30°C, so the corrosion rate is smaller at this temperature; the maximum of corrosion rate occurs at 60°C; when the temperature increases to 90°C, the corrosion rate is lower than that of 60°C, that is because hindering corrosion effect which take by the acceleration deposit of corrosion product is better than the acceleration corrosion reactions.

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Mechanical Properties and CO2 Corrosion Behavior of Q125 Grade Oil Tube Steel Used in Deep Oil Well

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.1471 ◽

2012 ◽

Vol 524-527 ◽

pp. 1471-1479 ◽

Cited By ~ 1

Author(s):

Di Tang ◽

Li Dong Wang ◽

Hui Bin Wu ◽

Jin Ming Liang

Keyword(s):

Corrosion Rate ◽

Corrosion Behavior ◽

Pitting Corrosion ◽

High Strength ◽

Strengthening Mechanism ◽

Dislocation Motion ◽

Tube Steel ◽

Co2 Corrosion ◽

Oil Well ◽

Austenite Grain

A type of Q125 grade high-strength low carbide oil tube steel was designed and researched. The strengthening mechanism of the steel was analyzed by SEM and TEM, and the CO2 corrosion behavior of the steel was simulated by high-temperature and high-pressure autoclave. The result show: the size of original austenite grain, packet and block are about 10-15μm, 2μm and 200nm, respectively, so the strength of the steel matched toughness well. The precipitate of (Nb,Ti)(C,N) whose size is about 60nm can restrain coarsening of the original austenite grain through pitting austenite grain boundary; The precipitate of (Nb,Ti)C and nanometer sized precipitate of NbC can be an effective barrier for dislocation motion, so that has great contributions to improve the strength of the steel. The average and pitting corrosion rate increased first and then dropped down with the increasing of temperature. There is a maximum of average and pitting corrosion rate at 90°C; Simultaneously, when the temperature is 90°C, there is a biggest difference between average corrosion rate and pitting corrosion rate.

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Electrochemical Investigation of Corrosion of X80 Steel under Elastic and Plastic Tensile Stress in CO2 Environment

Metals ◽

10.3390/met8110949 ◽

2018 ◽

Vol 8 (11) ◽

pp. 949 ◽

Cited By ~ 2

Author(s):

Wei Wu ◽

Hailong Yin ◽

Hao Zhang ◽

Jia Kang ◽

Yun Li ◽

...

Keyword(s):

Corrosion Rate ◽

Tensile Stress ◽

Corrosion Behavior ◽

Electrochemical Impedance ◽

Pipeline Steel ◽

Open Circuit ◽

Co2 Corrosion ◽

X80 Pipeline Steel ◽

X80 Steel ◽

Co2 Environment

An investigation into the electrochemical corrosion behavior of X80 pipeline steel under different elastic and plastic tensile stress in a CO2-saturated NaCl solution has been carried out by using open-circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analysis techniques. The results show that the corrosion rate of X80 steel first increases and then slightly decreases with the increase of elastic tensile stress, whereas the corrosion rate sharply increases with the increase of plastic tensile stress. Both elastic and plastic tensile stress can enhance steel corrosion by improving the electrochemical activity of both anodic and cathodic reactions. Moreover, compared with elastic tensile stress, plastic tensile stress has a more significant effect. Furthermore, electrochemical reactions for CO2 corrosion and mechanoelectrochemical effect are used to reasonably explain the corrosion behavior of stressed X80 steel in CO2 environment.

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The Toughness Index of X80 Mother Linepipe Steel and Its Optimum Microstructure

Volume 1: Codes and Standards ◽

10.1115/pvp2008-61062 ◽

2008 ◽

Author(s):

Xiaoli Zhang ◽

Yaorong Feng ◽

Yinglai Liu ◽

Chuanjing Zhuang

Keyword(s):

Experimental Data ◽

Acicular Ferrite ◽

Pipeline Steel ◽

Granular Bainite ◽

X80 Pipeline Steel ◽

Type Steel ◽

Toughness Index ◽

X80 Steel ◽

Linepipe Steel ◽

Selection Of

Large amount of experimental data indicated, that the index of CVN toughness and shearing area of mother pipe of X80 are (200J, 90%). And the results showed that when charpy toughness was closing to 200J, the shearing area would reach to 90%; when the charpy toughness increased continuously, the shearing area would not increase further more. So the selection of charpy toughness value as 200J for pipeline steels is reasonable, and also its corresponding shearing area. To gain thus component index, the optimum microstructure of X80 steel should be strip-like ferrite mastered, small amount of granular bainite contained-acicular ferrite type steel, and, in which the size of MA island should be less than 1μm. This kinds of optimum microstructure of X80 pipeline steel will exert its softening role in improving toughness and simultaneity not decrease its strength.

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Microstructure and Mechanical Properties Analysis of X70 Pipeline Steel with Polygonal Ferrite Plus Granular Bainite Microstructure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.161.67 ◽

2012 ◽

Vol 161 ◽

pp. 67-71 ◽

Cited By ~ 1

Author(s):

Zhan Zhan Zhang ◽

Xiu Rong Zuo ◽

Yue Yue Hu ◽

Ru Tao Li ◽

Zhi Ming Zhang

Keyword(s):

Mechanical Properties ◽

Pipeline Steel ◽

High Strength ◽

Polygonal Ferrite ◽

Granular Bainite ◽

X70 Pipeline Steel ◽

Microstructure And Mechanical Properties ◽

Drop Weight ◽

Bainite Microstructure ◽

Strength And Toughness

Microstructure and mechanical properties of X70 pipeline steel with polygonal ferrite plus granular bainite were characterized using tensile tests, Charpy V-notch impact tests, drop weight tear tests, hardness tests and scanning electron microscopy. The results of experiment indicated that X70 pipeline steel with polygonal ferrite plus granular bainite showed an excellent combination of high strength and toughness. The base metal with polygonal ferrite plus granular bainite microstructure exhibited perfect mechanical properties in terms of the transverse yield ratio of 0.81, elongation of 46%, an impact energy of 335 J at -10 °C and a shear area of 90% at 0 °C in the drop weight tear test. The heat affected zone contained coarse grain zone and fine grain zone, which exhibited good low temperature toughness of 216 J at -10 °C. The weld metal primarily consisted of intragranularly nucleated acicular ferrites which led to the high strength and toughness.

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Study on Microstructure and Properties of X80 Pipeline Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.941-944.138 ◽

2014 ◽

Vol 941-944 ◽

pp. 138-141 ◽

Cited By ~ 1

Author(s):

Xiang Dong Huo ◽

Feng Dong ◽

Lie Jun Li

Keyword(s):

Grain Refinement ◽

Impact Energy ◽

Acicular Ferrite ◽

Precipitation Hardening ◽

Pipeline Steel ◽

High Strength ◽

Experimental Methods ◽

Microstructural Characteristics ◽

X80 Pipeline Steel ◽

Toughness Improvement

Experimental methods, such as OM, SEM and X-EDS, were used to study the microstructure of X80 pipeline steel. It mainly consists of fine acicular ferrite (AF). X80 pipeline steel possesses high strength and impact energy at-30°C approaches to 400J. Grain refinement and precipitation hardening are the main reasons for high strength, and toughness improvement can be attributed to grain refinement and particular microstructural characteristics of AF.

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Microstructure and Mechanical Properties of Fiber Laser-Metal Active Gas Hybrid Weld of X80 Pipeline Steel

Journal of Pressure Vessel Technology ◽

10.1115/1.4006347 ◽

2012 ◽

Vol 135 (1) ◽

Cited By ~ 6

Author(s):

Lei Zhenglong ◽

Tan Caiwang ◽

Chen Yanbin ◽

Sun Zhongshao

Keyword(s):

Fiber Laser ◽

Acicular Ferrite ◽

Pipeline Steel ◽

Welding Process ◽

Granular Bainite ◽

Hybrid Welding ◽

X80 Pipeline Steel ◽

The Difference ◽

Pipeline Welding ◽

And Performance

Fiber laser-metal active gas (MAG) hybrid welding process was explored to join X80 pipeline steel to improve the efficiency and performance of pipeline welding. During the hybrid welding process, five different positions are applied to simulate the practical pipe girth welding. The weldability is evaluated concerning the bead shape, hardness, tensile, impact properties, and microstructures of welded joints. The results reveal that the tensile strength is higher than that of the base metal and the weld has a good impact ductility and an excellent bend performance. At the same time, the difference in microstructure between the laser zone and arc zone of laser-MAG hybrid welding of X80 pipeline steel is observed. Compared with the arc zone, the laser zone has finer weld grains and a narrower heat affected zone (HAZ). The fusion zone microstructure of the arc zone mainly consists of columnar proeutectoid ferrite (PF) and fine acicular ferrite (AF), whereas that of laser zone comprises acicular ferrite, upper bainite (Bu), and granular bainite (BG), which verifies technical feasibility of hybrid welding in pipeline steel and lays a good foundation for practical application.

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Corrosion Behavior of X70 Pipeline Steel and Corrosion Rate Prediction Under the Combination of Corrosive Medium and Applied Pressure

Volume 1B: Codes and Standards ◽

10.1115/pvp2017-65651 ◽

2017 ◽

Author(s):

Kaikai Li ◽

Wei Wu ◽

Guangxu Cheng ◽

Yun Li ◽

Haijun Hu ◽

...

Keyword(s):

Natural Gas ◽

Corrosion Rate ◽

Tensile Stress ◽

Partial Pressure ◽

Corrosion Behavior ◽

Pipeline Steel ◽

Applied Pressure ◽

Chloride Concentration ◽

X70 Pipeline Steel ◽

Co2 Partial Pressure

Natural gas transmission pipeline is prone to internal corrosion due to the combination of corrosive impurities in the pipe (such as CO2, H2S and chlorides) and applied pressure of the pipeline, which seriously affects the safe operation of the pipeline. In this work, the corrosion behavior of a typical X70 pipeline steel was investigated by using potentiodynamic polarization and electrochemical impendence spectroscopy (EIS). The polarization and EIS data under different CO2 partial pressures (0–1 atm), H2S concentrations (0–150 ppm), chloride concentrations (0–3.5 wt%) and tensile stress (0–400 MPa) were obtained. The results show that corrosion rate increases with the increase of CO2 partial pressure and chloride concentration, respectively, while first increases and then decreases with the increase H2S concentrations. The corrosion rate is less affected by elastic tensile stress. In addition, a quantitative prediction model for corrosion rate of natural gas pipeline based on adaptive neuro-fuzzy inference system (ANFIS) was established by fitting the experimental data which maps the relationship between the key influencing factors (i.e. CO2 partial pressure, H2S concentration, chloride concentration and tensile stress) and the corrosion rate. The prediction results show that the relative percentage errors of the predicted and experimental values are relatively small. The prediction accuracy of the model satisfies the engineering application requirement.

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Effect of Ferrite Volume Fraction on Mechanical Properties of X80 Pipeline Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.989-994.212 ◽

2014 ◽

Vol 989-994 ◽

pp. 212-215

Author(s):

J. Liu ◽

G. Zhu ◽

W. Mao

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Work Hardening ◽

Single Phase ◽

Volume Fraction ◽

Pipeline Steel ◽

X80 Pipeline Steel ◽

Hardening Behavior ◽

Two Phases ◽

Better Than

The effect of volume fraction of ferrite on the mechanical properties including strength, plasticity and wok hardening was systematically investigated in X80 pipeline steel in order to improve the plasticity. The microstructures with different volume fraction of ferrite and bainite were obtained by heat-treatment processing and the mechanical properties were tested. The work hardening behavior was analyzed by C-J method. The results show that the small amount of ferrite could effectively improve the plasticity. The work hardening ability and the ratio of yield/tensile strength with two phases of ferrite/bainite would be obviously better than that with single phase of bainite. The improvement of plasticity could be attributed to the ferrite in which more plastic deformation was afforded.

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