X80 Steel Research Articles

Study by finite element modeling of hydrogen atom diffusion and distribution at a dent on existing pipelines for hydrogen transport

Pipelines, especially existing natural gas pipelines, provide an efficient and economical means for hydrogen transport, accelerating realization of a full-scale hydrogen economy. However, the existing aged pipelines usually contain dents, which serve as effective traps to accumulate hydrogen atoms, potentially causing hydrogen embrittlement and pipeline failures. To date, there has been a strong interest in development techniques for assessment of hydrogen atom distribution at a dent on pipelines. In this work, a three-dimensional nonlinear finite element-based model was developed to investigate the hydrogen atom diffusion and distribution at a constrained dent on an X52 steel pipe. Parametric effects, including dent depth and internal pressure, were determined. The presence of a dent on pipelines drastically changes the local stress and strain distributions, facilitating diffusion and accumulation of hydrogen atoms at the dent. The minimum hydrogen atom concentration at the crystalline lattice sites, (i.e., 3.8 mol/m3) is located on the outer surface of the dent center, and the maximum hydrogen atom concentration (i.e., 12.1 mol/m3) is found on both sides of the dent with 103 mm from the dent center in the circumferential direction. The hydrogen atom concentration at trap sites at the dent is much lower than that at the lattice sites. The diffusion and accumulation of hydrogen atoms at the dent area is affected by two competitive mechanisms, i.e., hydrostatic stress and plastic strain, depending on the initial concentration of hydrogen atoms entering the interior of the pipe steel. At a low initial concentration such as 0.001 mol/m3, the equivalent plastic strain dominates the distribution of hydrogen atoms at the dent, and the hydrogen atom concentration at the lattice sites is much lower than the concentration at the trap sites. At high initial hydrogen atom concentrations such as 0.1 and 1 mol/m3, the hydrostatic stress is the dominant factor to determine the distribution of hydrogen atoms, which mainly accumulate at the lattice sites. With an increased depth of the dent, both the von Mises stress and plastic strain concentrations increase, and so is the hydrogen atom concentration. The increase of internal pressure from 5 MPa to 15 MPa only slightly elevates the von Mises stress, equivalent plastic strain and the hydrogen atom concentration.

Investigation on regression model for the force of small punch test using machine learning

The analytical solution for the force-deflection curve of the small punch test (SPT) is still a challenge. Machine learning is employed in the present study to establish a model for estimating SPT forces by using the strength of a material. The yield strength and ultimate tensile strength of materials and corresponding SPT force-deflection curves generated by finite element simulations are the training and testing data for machine learning. Pearson correlation analysis was performed first to measure the statistical association between the SPT force at a given deflection and the strength of materials. It was shown that a binary linear regression model was capable of correlating SPT forces to the yield strength and ultimate tensile strength of a material. The model parameters were determined after training, and then this model was tested by testing data. The accuracy of the regression model was verified by hypothetical materials, X70 steel and Incoloy 800H alloy. This study gives a new insight into the relationship between force responses of SPT and material properties, and can promote the development of novel approaches for determining material tensile properties using SPT.

Finite element simulation method for combined Ductile-Brittle fracture of small punch test in hydrogen

This paper presents a simulation method for combined ductile–brittle fracture of small punch (SP) test in hydrogen and application to test data of API X70 steel. For ductile fracture simulation, the multi-axial fracture strain damage model determined from un-embrittled material with the hydrogen-embrittlement constant determined from SP test in hydrogen is used. To simulate brittle fracture, the critical stress method is proposed, where the critical stress is determined using the V notch round bar tensile test in hydrogen. The determined models are applied to simulate the SP test in hydrogen showing combined ductile and brittle fracture mode. Simulation can well reproduce not only the load–displacement curve but also the circumferential ductile cracking, followed by radial brittle cracking, observed in the test.

Prediction of SIF range for plain API 5L Grade X65 steel under corrosion using AI & ML models

Corrosion is one of the significant aspects of science & engineering and the effects of corrosion on various infrastructures due to fatigue loading are paramount. Experimental investigations to evaluate fracture parameters and fatigue crack growth life take a considerable amount of time and effort. Recently, the computational boon in the form of Artificial Intelligence (AI) and Machine Learning (ML) has paved the way for predicting the required fracture parameters through training with the available limited experimental data. In this paper, the fracture parameter, Stress Intensity Factor (SIF) of plain API 5L X65 grade steel is predicted using the experimental data of crack growth studies performed on the specimen with single edge notch, eccentrically loaded, subjected to inert and corrosive environments (2.0% and 3.5% NaCl). From the experimental data, the fracture parameter, SIF range is determined for various crack lengths corresponding to certain loading cycles. Multivariate Adaptive regression splines (MARS), Artificial Neural Network (ANN), and relevance vector machine (RVM) based models are developed by using the experimental data to predict the SIF range. The efficiencies of the developed models are verified through several statistical parameters. The studies show that the proposed models are capable of predicting the SIF range for plain API 5L X65 grade steel effectively with the available experimental data. The predicted SIF range is highly useful for the prediction of crack growth life and the evaluation of the residual strength of structural components.

CO2 Corrosion Behavior of X70 Steel under Typical Gas–Liquid Intermittent Flow

CO2 Corrosion Behavior of X70 Steel under Typical Gas–Liquid Intermittent Flow

Impact of residual cementite on inhibition of CO2 corrosion of mild steel

A thick cementite skeleton exposed on a ferritic-pearlitic C1018 steel surface after pre-corrosion significantly compromised inhibition efficiency. However, this detrimental effect was insignificant for a lower carbon X65 steel with dispersed cementite microstructure, due to the insignificant amount of cementite that remained on its surface after pre-corrosion. After normalizing the increased cathodic area in the presence of residual cementite back to original area, both anodic and cathodic reactions were inhibited to the same extent as on bare steel with a sufficient inhibitor concentration. However, the detrimental effect of cementite cannot be completely eliminated due to its galvanic coupling effect.

Feasibility of orbital friction stir welding on clad pipes of API X65 steel and Inconel 625

Orbital friction stir welding (FSW) has been applied to clad pipes, which is certainly of interest to the oil and gas industry. In this context, an FSW system capable of performing sound joints in one pass with full tool penetration was developed. Orbital FSW was executed in 6 mm thick API X65 PSL2 steel clad pipes with 3 mm thick Inconel 625 using a polycrystalline cubic boron nitride (pcBN) tool. The metallurgical and mechanical properties of the joints were investigated. Sound joints with axial forces of 45–50 kN, tool rotational speeds of 400–500 rpm, and a welding speed of 2 mm/s were obtained, illustrating that the developed system can perform FSW joints without volumetric defects.

Electrochemical, surface analysis, computational and anticorrosive studies of novel di-imine Schiff base on X65 steel surface

The inhibitory effect of di-imine-SB namely ((N1Z, N4E)-N1, N4-bis (4 (dimethylamino) benzylidene) butane 1,4-diamine) on X65-steel in 1 M HCl has been investigated experimentally and theoretically. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss outcomes display the anticorrosion properties of “di-imine- SB”. The inhibitory efficiency exceeds 90% at the optimal concentration of 1 × 10–3 M “di-imine- SB”. The metal surface was examined further using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). The effectiveness of the di-imine-SB is returned into its adsorption on X65-steel surface and found in agreement with Langmuir adsorption isotherm. According to the standard Gibbs free energy of adsorption ({Delta G}_{ads}^{^circ }), di-imine-SB adsorption tends to be chemical rather than physical, it increases the activation energy ({mathrm{E}}_{a}) of metal dissolution reaction and makes it hard to occur. The PDP data suggested anodic and cathodic type of the di-imine-SB inhibitor. Meanwhile, increasing the resistance of X65-steel to 301 Ω cm2 after adding 1 mM of di-imine-SB confirms its protective effect. Whereas, the positive value of the fraction of electron transference (ΔN, 0.746), confirms the affinity of di-imine-SB to share electrons to the partially filed 3d-orbital of Fe forming strong protective film over X65-steel surface. Aided by Monte Carlo (MC) simulation, the calculated adsorption energy (Eads) suggests excessive adsorption affinity of di-imine-SB on metal surface over the corrosive chlorides and hydronium ions. A good correlation between the theoretical hypothesis and the experimental inhibition efficiency has been achieved. The comparative study showed the superior of the di-imine-SB as potential corrosion inhibitor compared with those reported before. Finally, global reactivity descriptors; electron affinity (A), ionization potential (I), electronegativity (χ), dipole moment (µ), global hardness (eta), electrophilicity index and, Fukui indices were also calculated and found well correlated to the reactivity of di-imine-SB.

Insight into the anti-corrosive performance of Persea Americana seed extract as a high-efficiency and sustainable corrosion inhibitor for API 5 L X65 pipeline steel in 1 M HCl solution

Presently, there is high demand for less toxic and effective corrosion inhibitors for the acidizing process owing to the toxicity of the existing inhibitors. Therefore, the objective of this study is to explore the feasibility of Persea Americana seed extracts (PASE) as sustainable corrosion inhibitors to mitigate the corrosive effect of 1 M HCl on API 5 L X65 pipeline steel using weight loss, and potentiodynamic polarization techniques. Fourier transform infrared spectroscopy (FTIR) was utilized to establish the inhibitor’s functional group. The result obtained shows that the inhibition efficiency increased with concentration, with the best inhibitor efficiency obtained as 95.65% for 5 g PASE in 1 M HCl solution. The electrochemical tests revealed that PASE behaves as a mixed-type corrosion inhibitor. The adsorption of PASE followed the Langmuir adsorption isotherm. Results from FTIR confirm that PASE extracts contain hydroxyl group compound, flavonoid, and phenolic content which can be utilized as corrosion inhibitors. The SEM analysis shows a notable difference in the steel surface with inhibitor owing to the protective barrier formed on the metal surface. In the formulation of acidizing corrosion inhibitors, PASE is a promising active compound. The data obtained from the weight loss test is in agreement with the electrochemical tests and demonstrates excellent inhibitive behavior of PASE on X65 steel in the acid solutions. This research provides insight into the development of sustainable corrosion inhibitors for X65 steel.

Electrochemical Investigations of Simulated Surface Scales Formed on X65 and J55 Pipeline Steel

Electrochemical Investigations of Simulated Surface Scales Formed on X65 and J55 Pipeline Steel

Corrosion inhibition of X70 steel by tetrabutylammonium iodide in 1 M HCl at different temperatures

Corrosion inhibition of X70 steel by tetrabutylammonium iodide in 1 M HCl at different temperatures

Synergistic effect of different testing environments on the hydrogen-induced mechanical degradation to establish the role of microstructural features on the failure of X70 pipeline steel

Hydrogen-induced mechanical degradation was evaluated in different environmental conditions on two X70 pipeline steels having the same composition but different thermomechanical processing parameters, and a further correlation between microstructural features and hydrogen embrittlement (HE) susceptibility was established. HE susceptibility was determined by performing the Slow Strain Rate Tensile Test (SSRT) in air, ex-situ hydrogen-charged, in corrosive media, in-situ hydrogen-charged and Charpy impact tests before and after hydrogen charging in a wide range of temperatures.The SSRT results indicated that the synergistic action of stress and hydrogen in in-situ charged sample leads to maximum HE susceptibility in both X70 steels. Charpy results demonstrated that ductile-to-brittle transition temperature (DBTT) increases after hydrogen charging. The texture analysis revealed that X70-2 with a higher volume fraction ratio of Ƴ-fiber/{100}<011> demonstrated improved HE resistance, whereas X70-1 with higher fractions of {113}<110> and {100} || ND demonstrated a higher DBTT than before and after hydrogen charged X70-2.

Sustainable and Green Approach for Api 5L Pipeline Steel Acidic Corrosion Inhibition Using Agro-Industrial Waste: Experimental and Theoretical

Currently, the use of synthetic inhibitors in preventing corrosion is destructive to the environment; therefore, natural inhibitors might be an alternative and innovative solution to this challenge, owing to their sustainability. Herein, wasted avocado seed extract was examined as a sustainable and green inhibitor for API 5L X65 pipeline steel at an ambient temperature using the gravimetric analysis, the potentiodynamic polarization curve, and linear polarization resistance techniques. The inhibitor’s chemical characterization was carried out with Fourier-transform infrared spectroscopy (FTIR), and the morphological characterization was carried out by detailed scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). The result showed that the extract decreased the corrosion rate by retarding the cathodic and anodic electrochemical reactions, with a maximum efficiency of 88% at 5 g/L. The extract was adsorbed physically onto the X 65 steel following the Langmuir adsorption isotherms. The electrochemical studies showed that the agro-waste was a mixed-type inhibitor. The SEM image of the X65 steel with the extract showed thin film formation on the steel surface. The extract can be substituted for synthetic inhibitors, which are toxic, scarce, and costly.

Preparation and Hydrogen Barrier Property of FexAly/Al/Al2O3 Composite Coating on X80 Steel Surface

Preparation and Hydrogen Barrier Property of FexAly/Al/Al2O3 Composite Coating on X80 Steel Surface

Robust Optimization of UOE Forming Process Considering Inhomogeneity of Material Properties

Abstract The properties inhomogeneity of steel plates will result in uncertainty of forming quality of large diameter UOE oil pipes and increase the risk of pipeline failure. In this paper, a robust design method for UOE forming process based on support vector machine and sequential response surface modeling and considering the variation of steel plates′ properties is proposed. A hundred of mechanical experiments are first carried out and the variation of X80 steel's properties is statistically evaluated. The varied properties are assigned to partitioned steel segments and taken as the noise factor in process design. The ovality of the UOE pipe is employed as the optimization objective, and the forming quality indicators including convex amount, mean outside diameter, yield strengths and Ys/Uts7, O-forming gap, the width of the U-shaped plate, inclined angle of straight arm of the U-shaped plate, etc., are taken as the constraints. Based on the semi-analytical computation of C-, U- and O-forming processes and finite element simulation of expanding process, a sequential response surface model is established by using the support vector machine method. Finally, a Monte Carlo sampling is performed to demonstrate the effectiveness of the proposed method. Compared to conventional optimization method, the robust optimization performs obviously better in reducing the ovality and increasing the robustness of UOE forming process.

Assessing the pressure losses during hydrogen transport in the current natural gas infrastructure using numerical modelling

The UK government aims to transition its modern natural gas infrastructure towards Hydrogen by 2035. Since hydrogen is a much lighter gas than methane, it is important to understand the change in parameters when transporting it. While most modern work in this topic looks at the transport of hydrogen-methane mixtures, this work focuses on pure hydrogen transport. The aim of this paper is to highlight the change in gas distribution parameters when natural gas is replaced by hydrogen in the existing infrastructure. This study uses analytical models and computational models to compare the flow of hydrogen and methane in a pipe based on pressure loss. The Darcy-Weisbach and Colebrook-White equations were used for the analytical models, and the k- ε model was used for the computational approach. The variables considered in the comparison were the pipe material (X52 Steel and MDPE) and pipe diameters (0.01m–1m). It was observed that hydrogen had to be transported 250–270% the velocity of methane to replicate flow for a fixed length of pipe. Furthermore, it was noted that MDPE pipes has 2–31% lower pressure losses compared to X52 steel for all diameters when transporting hydrogen at a high velocity. Lastly, it was noted that the analytical model and computational model were in agreement with 1–5% error in their findings.

Effect of heat treatment on the welded joint of X70 steel joined to duplex stainless steel by gas tungsten arc welding

Effect of heat treatment on the welded joint of X70 steel joined to duplex stainless steel by gas tungsten arc welding

Electrochemical evaluation of Trasar trac 102 as a corrosion inhibitor on API 5L X65 steel and theoretical study

Electrochemical evaluations of the commercially available inhibitor Trasar Trac102 were carried out under static and hydrodynamic conditions on API 5L X65 steel immersed in NaCl 3% wt. By Electrochemical Impedance Spectroscopy (EIS) techniques, obtaining the best efficiency of 95.4% under static conditions at 20 ppm. It was detected by rotating cylinder electrode that as the revolutions per minute of 100, 500 and 1000 rpm were increased, the inhibition efficiency tended to decrease as a result of the adsorption–desorption process of the organic molecules by the rotation rate. The results showed that the adsorption type of Trasar Trac102 on API 5L X65 steel in NaCl 3% wt was to form a monolayer on the metal surface according to the model fit with Langmuir isotherm. Scanning Electron Microscopy (SEM) was used for surface characterization, which shows a great difference in the target systems with corrosion products as a result of the deterioration caused by the corrosive medium and in the presence of the inhibitor. The results of the chemical analysis (EDX) show a significant decrease of oxygen in the presence of the inhibitor, suggesting that Trasar Trac102 is adsorbed directly on the steel. Dispersion-Corrected Density Functional Theory (DFT) calculations were used to characterize the interactions between the inhibitor components and the steel surface by a cluster approach. Mostly, chemisorption was explained by bonds established between oxygen atoms of inhibitor components and iron ones of the steel surface. Due to their free binding energies computed, metasilicate and mercaptobenzothiazol are expected to interact strongly and to adsorb spontaneously on the steel surface. Also, metasilicate is the component that obtained the largest charge transference to iron cluster.

Study on the Influence of Non-Metallic Inclusions on the Pitting Corrosion of API 5L X60 Steel

The most economical way to move liquids and gaseous hydrocarbons is by using pipelines. According to several international organizations and oil companies, the use of fossil fuels will continue in the following decades. For this reason, it is important to continue studying different corrosion mechanisms and their origins. One of the mechanisms that provoke small leaks, affecting pipeline hermeticity, is pitting corrosion. It is well-known that non-metallic inclusion dissolution can trigger pit nucleation. As pitting corrosion is recognized to be random in nature, it is also interesting to study the random nature of the inclusions present in API 5L X60 steel. Probability distributions commonly used to describe pitting corrosion characteristics are appropriate for studying inclusion characteristics. The size of inclusions plays a key role in pit nucleation because small inclusions tend to generate more defects, especially when these inclusions are compounds of MnS, and the steel is immersed in a corrosive solution. The results of this research work show that there is a close relationship between the random nature of pitting corrosion and inclusions.

Effects of cathodic protection potential on microbiologically induced corrosion behavior of X70 steel in a near-neutral pH solution

Sulfate reducing bacteria (SRB) are considered as one of the main causes for the failures of buried metal pipes. Although many researchers reported that more negative cathodic protection potential was required in environments containing SRB, SRB would increase the concentration of hydrogen adsorbed on steel surface and thus lead to hydrogen embrittlement. In the study, the optimum cathodic protection (CP) potentials of X70 steel in bacterial and sterile media were evaluated with electrochemical impedance spectroscopy. The morphology and composition of corrosion products were characterized by a scanning electron microscope (SEM), an energy dispersion x-ray spectrometer (EDS), and an x-ray photoelectron spectrometer (XPS). The corrosion morphology of X70 steel in NS4 medium was pits and the corrosion in the bacterial medium was more serious than that in the sterile medium. The corrosion products of X70 steel were FeOOH and Fe2O3 in the sterile medium, whereas its corrosion products in the bacterial medium were FeOOH and FeS. When CP potential was −775 mV, SRB growth was promoted and the optimal protection effect on X70 steel was achieved in the bacterial NS4 medium. Pits were still observed under the biofilm and the corresponding corrosion mechanism was extracellular electron transfer (EET). When CP potential was −875 mV, X70 steel realized the optimal protection in the sterile NS4 solution. However, CO2 hydrolysis and SRB metabolism in the bacterial medium resulted in hydrogen-induced pits. When CP potential was −1025 mV, the growth of SRB was inhibited and severe hydrogen evolution corrosion occurred on X70 steel in bacterial and sterile NS4 media. The optimal CP potential for pipeline steel in the sterile medium may lead to hydrogen corrosion in the bacterial medium when H+ concentration was high.