X80 Steel Research Articles

Evaluation of Tribological Behavior of X65, X70, and X80 Pipeline Steels in the Presence of Hydrogen

Evaluation of Tribological Behavior of X65, X70, and X80 Pipeline Steels in the Presence of Hydrogen

The effect of hydrogen and notch orientation in SENT specimens on the fracture toughness of an API 5L X70 pipeline steel

Transporting hydrogen gas through pipelines is an important topic within the context of energy transition. An essential challenge hereto is the phenomenon of hydrogen embrittlement of pipeline steels which includes a reduction in fracture toughness. As the theories accounting for hydrogen embrittlement are still debated, improving fundamental insights into the underlying mechanisms is crucial. Fracture toughness tests on single edge notched tension (SENT) specimens have been performed to examine the influence of hydrogen on the fracture behavior of a pipeline steel. An API 5L X70 steel was selected for this purpose, characterized by a distinctive banded microstructure commonly seen in pipeline steels. The test specimens were extracted from the steel pipe, and a notch in two different orientations was machined. By using a combination of fractography and X-ray micro-CT (Computed Tomography), the fracture mechanisms are revealed. The tearing resistance characteristics of the steel, with and without the presence of hydrogen, are demonstrated through tearing resistance curves. The experiments show that the banded microstructure plays a key role in the results through the development of splits at the microstructural bands. While these splits are also present in uncharged toughness test specimens, they are increasingly present in hydrogen charged specimens suggesting a hydrogen related weakening of the banded microstructure. In addition, it is demonstrated that hydrogen induces an increasingly zigzagged crack path. This is attributed to a potential combination of accelerated void nucleation at the microstructural bands, and accelerated shear-driven fracture.

Study on the Influence of Hydrogen Blended Transportation on the Safety of Existing X70 Steel in Gas Distribution Pipeline Network

Coal to gas is one of the natural gas sources utilized in Beijing, with a hydrogen blend concentration range from 1% to 3% and reaching up to 5% in specific cases. In order to evaluate the safety of transporting hydrogen blended natural gas with X70 pipeline steel in distribution pipelines, this study first conducted the slow strain rate tensile tests under a total pressure of 4 MPa in hydrogen environment. The results show that X70 steel exhibits highly sensitive to a hydrogen blending ratio of 5%. Subsequently, four types of hydrogen compatibility tests were conducted in the above sensitive hydrogen partial pressure include the impact toughness test, fracture toughness test, fatigue crack growth test, and fastening disk pressure test. The findings demonstrated that hydrogen blended natural gas has virtual no effect on the impact and fracture toughness, with only 10% reduction in fatigue crack growth threshold. Finally, based on fatigue life analysis by fracture mechanics evaluation, it can be concluded that the existing natural gas pipe of X70 steel is capable to operate safely over 40 years under a total pressure of 4 MPa with a hydrogen blend concentration of 5%.

Research on Strain of Unequal Wall Thickness Pipeline of the X80 Pipeline under Lateral Load

X80 steel is a material with high strength and good toughness, which is widely used in long-distance natural gas pipelines. Pipelines will have different wall thicknesses, depending on the safety level requirements of different regions. Two sections of pipes with different wall thickness form unequal wall thickness of pipeline (UWTP) that is joined together by welding. UWTP pass through some geohazard areas, such as landslides. The frequency of landslides is extremely high in mountainous areas, which can seriously affect the safe operation of UWTP. In this paper, a model of a 12.8 mm wall pipe section and a 15.6 mm wall pipe section are linked by girth welds. The strain between the pipe section and the weld was quantitatively analyzed. The results show that the strain at the girth weld in the 3 o’clock direction of the pipe increases sharply. The strain in the 9 o’clock direction of the pipe is generally lower than the strain in the 3 o’clock direction. The strain value of the 12.8mm wall thickness pipe section is generally greater than the strain value of the 15.6mm wall thickness pipe section.

Effect of Welding Process Parameters on the Mechanical Properties of TIG and MIG Welds in HSS X65 Pipe-A Review

The study focused on the importance of the different welding parameters on the mechanical behavior of High Strength Steel (HSS) X65 steel pipes by reviewing the advantages of parameter optimization for the Tungsten Inert Gas (TIG) - Metal Inert Gas (MIG) welding processes. The parameters considered in the study include welding speed, welding current, welding voltage and gas flowrate of the welding. The effects of improper selection and parameter optimizations were highlighted and illustrated using different metallurgical and mechanical instances. The outcome of the study indicates that adequate parameter optimization aids in obtaining good weld quality with adequate mechanical and microstructural properties. Furthermore, it helps in the determination of variation in hardness in the heat affected zone as well as the base metal. Thus, this study provides insight to welding engineers on the importance of parameter optimization in the welding of steel pipe.

Postweld Heat Treatment on Toughness of Electric- Resistance Welded X70 Steel

The effect of postweld heat treatment (PWHT) on Charpy V-notch impact toughness of a highfrequency electric-resistance welded (HF-ERW) grade X70 pipeline steel is investigated. PWHT thermal cycles are simulated using the Gleeble on the as-welded specimens. Microstructure, along with crystallographic texture and microhardness, is characterized in specimens that are impact tested at –5°C (23°F), –30°C (–22°F), and –45°C (–49°F). The impact toughness values show a wide scatter band and decrease with the increasing peak temperature of the PWHT. For higher peak temperatures, the microstructure of the heat-affected zone (HAZ) gradually changed from equiaxed ferrite to bainitic ferrite. Furthermore, the prior austenite grain size (PAGS) increases with the increasing peak temperature. The density of high-angle grain boundaries decreases, and the fraction of cleavage planes {100} parallel to the impact fracture plane increases for higher peak temperatures of the PWHT.

Corrosion of welding reinforcement height under dynamic conditions

The presence of welding reinforcement height (WRH) within oil and gas pipelines can lead to micro-turbulence in localized areas during transportation, resulting in corrosion failure. This study employed a modular reconstruction method to simulate and reconstruct X80 steel welded joints, and investigated the erosion-corrosion behavior at the WRH using wire beam microelectrode, electrochemical impedance spectroscopy, and computational fluid dynamics simulations. The results show that the galvanic current density (GCD) in the weld metal exhibits cathodic behavior, while the GCD in the base metal and heat-affected zone shows anodic behavior. The top of WRH is susceptible to corrosion failure. As the radius of WRH increases, the corrosion rate also increases. Additionally, the corrosion rate increases similarly with an increase in flow velocity. The galvanic corrosion intensity factor (g) is 0.24, and the local corrosion is moderate. This work has scientific significance in ensuring the long-term safe operation of pipelines and reducing the risk of corrosion failure.

Evaluation of corrosion behaviour and susceptibility to hydrogen-induced cracking in high-strength low-alloy X70 steels under sour gas conditions

High-strength low-alloy (HSLA) steels find extensive usage in the oil industry for manufacturing pipes due to their requirement for materials with high mechanical and corrosion resistance. Among these steels, the HSLA X70 steels are particularly of great interest to the petroleum industry because of its high mechanical resistance, ductility and weldability. In this study, it was aimed to assess the corrosion behaviour of HSLA API X70 pipelines using electrochemical impedance spectroscopy (EIS) technique and evaluate its resistance to hydrogen-induced cracking (HIC). The analyses were conducted in non-sour and sour media, as per NACE TM0284 standard. Microstructural characterisations of polished and corroded samples were also conducted using scanning electron microscopy (SEM) and optical microscopy (OM). The results indicate that the resistance to HIC in API 5L X70 steel is compromised when exposed to surface corrosion in sour gas media. This susceptibility may be attributed to the presence of microconstituents MnS and M/A along the grain boundaries, which were found in the crack trajectory. The identified microstructural features are deemed to exert a significant influence on the propagation of cracks and the consequent susceptibility to HIC. Moreover, the EIS tests revealed the lowest corrosion resistance when exposed to H2S media, as MnS inclusions accelerate the active regions in the matrix, consequently leading to the formation of a plethora of corrosion products and the dissolution of iron.

Performance of two high-strength steels under electrochemical corrosive and stressed conditions

The corrosion behaviors of stressed API X-80 and API X-120 pipeline steels were investigated using electrochemical and slow strain rate tensile tests after being immersed in a saline solution containing 3.5% NaCl. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive x-ray spectroscopy (EDX) were used to create images of the flawed steel samples. Corrosion rates for API X-120 pipeline steel were found to be much lower than those of API X-80 pipeline steel in both stressed and saline environments. While different oxide layers were observed on the two steels, the result showed the oxide film was of iron carbonate. It was observed that the API X-120 steel surface was latently smooth in a saline solution environment which reduced the corrosion rate. As a result, the API X-120 pipeline steel was protected and had a delayed time-to-failure in comparison to the API X-80 pipeline steel when it was tested in steel under stress and in solution medium. This failure mechanism will not only be significant to the petroleum sector, but also to the industry that produces pipelines in terms of the choice of fitting material for pipe design. Specifically, this mechanism will have an impact on the design of fittings for pipes.

Effect of nano-Al2O3 particle addition on Co–P–xAl2O3 nanocomposite plating electroplated on X65 steel

PurposeThe purpose of this study is to reveal the effect of nano-Al2O3 particle addition on the nucleation/growth kinetics, microhardness, wear resistance and corrosion resistance of Co–P–xAl2O3 nanocomposite plating.Design/methodology/approachThe kinetics and properties of Co–P–xAl2O3 nanocomposite plating prepared by electroplating were investigated by electrochemical measurements, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Vickers microhardness measurement, SRV5 friction and wear tester and atomic force microscopy.FindingsA 12 g/L nano-Al2O3 addition in the plating solution can transform the nucleation/growth kinetics of the plating from the 3D progressive model to the 3D instantaneous model. The microhardness of the plating increased with the increase of nano-Al2O3 content in plating. The wear resistance of the plating did not adhere strictly to Archard’s law. An even and denser corrosion product film was generated due to the finer grains, with a high corrosion resistance.Originality/valueThe effect of different nano-Al2O3 addition on the nucleation/growth kinetics and properties of Co–P–xAl2O3 nanocomposite plating was investigated, and an anticorrosion mechanism of Co–P–xAl2O3 nanocomposite plating was proposed.

Study of temperature effect on hydrogen embrittlement in X70 pipeline steel

The study investigates the temperature effect on hydrogen embrittlement (HE) in X70 steel using Devanathan-Stachurski and tensile tests under varying cathodic hydrogen-charging currents. The most severe HE temperature threshold is identified via scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) methods. The temperature thresholds for 10 mA/cm2 and 20 mA/cm2 are 293 K and 283 K, respectively, while no critical temperature at 30 mA/cm2. The underlying mechanism is studied, and a predictive model is established. Also, the primary hydrogen-induced fracture plane is identified as {110}, beneath where hydrogen enhances plastic deformation in {110}<111> and inhibits in {112}<111>.

Dynamic buckling response of buried X70 steel pipe with bolted flange connection under two-charge explosion loads

It is of great significance to investigate the dynamic response of pipes under blasting loads for the operation, assessment, and repair of pipes. However, there are few studies available on the dynamic buckling response of pipes under multiple explosion loads. In the present study, pipe-soil coupling 3-D models are established to investigate the dynamic buckling response of X70 steel pipe with bolted flange connection (BFC) under two-charge explosion loads (Charge A lied on the ground surface and Charge B lied in the soil). The main influencing factors are also discussed, including explosion mode, internal pressure, interval time, mass ratio of charges, and diameter-to-thickness ratio (D/t ratio). When Charges A and B were exploded simultaneously, it is found that the non-pressurized X70 pipe produced more significant cross-sectional deformation than in one-point explosion (Charge A or B). Increasing D/t ratio is advantageous for the anti-explosion of the pipe with BFC. Suitable internal pressure can effectively prevent the buckling deformation of the pipe. Compared with the common straight pipe, BFC system can effectively decrease the local buckling deformation and improve the anti-explosion ability of the pipe due to its higher local stiffness and energy absorption.

Numerical analysis EF of resilience impact test behavior for X80 steel

Numerical analysis EF of resilience impact test behavior for X80 steel

Research on the characteristics of weak magnetic internal detection signals for critical damage in pipeline stress based on density functional theory

Pipeline stress-induced critical damage is a primary cause of sudden pipe ruptures. To investigate the characteristics of weak magnetic internal detection signals related to critical damage in pipeline stress, a magneto-mechanical model was developed based on density functional theory. The model could assess the corresponding relationships among the generalized stacking fault energy (GSFE), critical resolved shear stress (CRSS), atomic magnetic moment, and magnetic signals during the critical damage process of the pipeline. The analysis included examining the influential patterns of different stress directions and materials on the magnetic signals associated with critical damage, followed by the systematic experimental verification.The research results indicated that when the crystal dislocation stress exceeded the CRSS, weak magnetic signals could effectively characterize the critical damage induced by stress, accompanying by a sharp variation in magnetic signals observed during critical damage occurrence. Different stress directions lead to varying energy barriers that must be overcome for critical damage, resulting in distinct magnetic signal features. In the {112} plane, the CRSS increased by 11.07 % compared with {11¯0} plane, and the axial magnetic signal during critical damage was elevated by 1.47 % compared with {11¯0} plane. Variances in magnetic signals for critical damage were assessed for steel pipes of different materials due to differences in processing and composition. Under identical conditions, the magnetic signal difference for critical damage in X80 steel plates was 39 % higher than that in X70 steel plates. Additionally, the magnetic signal difference for critical damage in the circumferential weld of X80 was 53 % higher than that in X80. The findings provided a theoretical basis for monitoring and early warning of critical damage states in pipelines.

The Influence of Centerline Segregation on Impact Toughness in Welding Heat-Affected Zone of X70 Pipeline Steel

The influence of centerline segregation on the low-temperature impact toughness of the heat-affected zone (HAZ) of welded joints was studied by welding experiments on X70 steel plates rolled from continuous casting slabs with segregation grades of class 2 and class 3. The experimental results show that the impact toughness at HAZ from class 2 slab steel plate is more stable and has excellent low-temperature toughness than that of class 3 slab steel plate. The impact toughness of the HAZ of the class 3 slab steel plate is low to 100 J at −40 °C and has a severe fluctuation range (~150 J), and the delamination phenomenon is also observed in the fracture cross-section. The reason for this phenomenon is due to the enrichment of C and Mn elements in the centerline segregation zone. The formation of abnormal microstructure (martensite/bainite) in the segregation zone leads to stress concentration, which easily weakens the low-temperature toughness of the joint.

Influence of Xinjiang Saline Soil on Corrosion of X80 Pipeline Steel

A large-scale gas transmission pipeline project will pass through typical saline soil areas in Xinjiang, China, to find out the influence of the saline soil on the long-distance pipeline in this area, this paper investigates the corrosive behavior of X80 pipeline steel embedded in saline soil with multiple corrosion intensities. Firstly, NaCl, Na2SO4, NaHCO3, and deionized water were used to simulate the saline soil with different corrosion intensities, and then the corrosion test of X80 steel was carried out. A scanning electron microscope was used to observe the X80 steel before and after corrosion. Finally, the weight loss method was used to calculate the corrosion rate, and the corrosive behavior of X80 pipeline steel in Xinjiang saline soil environment was analyzed. The results show that: (1) X80 steel is susceptible to pitting corrosion in the saline soil environment; (2) the rate and level of corrosion were mainly related to the content of Cl− and SO4 2−. The greater the content, the stronger the pipeline is corroded; (3) the rate and level of corrosion were positively correlated with the corrosion intensities of saline soils.

Inhibitory effect of marine Bacillus sp. and its biomineralization on the corrosion of X65 steel in offshore oilfield produced water

The issue of material failure attributed to microbiologically influenced corrosion (MIC) is escalating in seriousness. Microorganisms not only facilitate corrosion but certain beneficial microorganisms also impede its occurrence. This study explored the impact of marine B. velezensis on the corrosion behavior of X65 steel in simulated offshore oilfield produced water. B. velezensis exhibited rapid growth in the initial stages, and the organic acid metabolites were found to promote corrosion. Subsequently, there was an increase in cross-linked “networked” biofilms products, a significant rise in the prismatic shape of corrosion products, and a tendency for continuous development in the middle and late stages. The organic/inorganic mineralized film layer formed on the surface remained consistently complete. Metabolic products of amino acid corrosion inhibitors were also observed to be adsorbed into the film. B. velezensis altered the kinetics of the X65 steel cathodic reaction, resulting in a deceleration of the electrochemical reaction rate. The mineralization induced by B. velezensis effectively slowed down the corrosion rate of X65 steel.

Low efficiency of cathodic protection in marine tidal corrosion of X80 steel in the presence of Pseudomonas sp.

Owing to the effects of seawater erosion, dry/wet cycles, dissolved oxygen and microorganisms, the corrosion of steel in marine tidal environments is a serious threat to the safe and stable operation of marine equipment and facilities. Among them, microbiologically influenced corrosion (MIC) of steel has received increasing attention. Cathodic protection (CP) is frequently used to control the corrosion of offshore steel structures. However, in the presence of microorganisms, implementation of CP and its specific effects remain controversial. In this study, the influence of Pseudomonas sp. on the CP efficiency of Zn sacrificial anodes (ZnSAs) during the tidal corrosion of X80 steel was studied. The results showed that CP efficiency exceeded 92% in an abiotic tidal environment. However, in the biotic tidal environment, Pseudomonas sp. significantly reduced the CP efficiency. Pseudomonas sp. and its biofilm promoted the corrosion of steel under CP, inhibited the formation of a complete calcareous deposit layer, which weakened the CP efficiency of ZnSA in the marine tidal environment.

Mitigation of Desulfovibrio ferrophilus IS5 degradation of X80 carbon steel mechanical properties using a green biocide.

Most microbiologically influenced corrosion (MIC) studies focus on the threat of pinhole leaks caused by MIC pitting. However, microbes can also lead to structural failures. Tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide mitigated the microbial degradation of mechanical properties of X80 steel pipeline by Desulfovibrio ferrophilus (IS5 strain), a very corrosive sulfate reducing bacterium. It was found that 100 ppm (w/w) THPS added to the enriched artificial seawater (EASW) culture medium before incubation resulted in 2.8-log reduction in sessile cell count after a 7-d incubation at 28 °C under anaerobic conditions, leading to 94% uniform corrosion rate reduction (from 1.3to 0.07mm/a), and 84% pitting corrosion rate reduction (from 0.70to 0.11mm/a). The X80 dogbone coupon incubated with 100 ppm THPS for 7 d suffered 3% loss in ultimate tensile strain and 0% loss in ultimate tensile strength compared with the abiotic control in EASW. In comparison, the no-treatment X80 dogbone coupon suffered losses of 13% in ultimate tensile strain and 6% in ultimate tensile stress, demonstrating very good THPS efficacy.

Corrosion testing of X52 and X80 steels immersed in stimulated emulsions using a real petroleum sample

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 °C, 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.