Heavy Wall Pipe Research Articles

Effect of through-thickness microstructure inhomogeneity on mechanical properties and strain hardening behavior in heavy-wall X70 pipeline steels

The ever-increasing demand for oil & gas exploration from land to subsea necessitates using higher-strength and high-ductility heavy-wall thickness pipes, which may increase the microstructural inhomogeneity along the steel plate sections, ultimately impacting the mechanical properties. In this work, the differences in microstructure and mechanical properties between the through-thickness layers of a heavy-wall ferrite/bainite (F/B) dual-phase (DP) X70 pipeline steel plate were studied. The results showed that the size of the ferrite grain and the volume fraction of bainite increased from the surface layer to the mid-thickness layer of the DP X70 pipeline steel plate. The surface and mid-thickness layers had a lower uniform elongation and higher strength and hardness. In comparison, the quarter layer had higher uniform elongation and lower strength and hardness. The refined grain size and the strong {001}<110> texture were responsible for enhanced in strength and hardness. The higher γ-fiber texture at the quarter layer favored the higher plasticity. The analysis results of strain-hardening behaviors based on the modified C-J model showed that the mid-thickness layer had a higher strain-hardening capacity at the beginning of the plastic strain, leading to deformation instability and reduced material plasticity. The surface layer maintained a high hardening exponent even at high plastic strains, which facilitated the deformation properties of the material. The results provide a basis for evaluating the influence of microstructural factors on the strength and plasticity of heavy-wall X70 pipeline steel and the coordination mechanism of micro deformation in DP steels.

Spatial matching relationship of dual heat sources in electromagnetic heating of pipes

• Dual heat sources reduce the probability of latent defects in electromagnetic heating. • The mechanism of the interference of dual heat sources on the induced magnetic field. • Reveal the spatial matching relationship of dual heat sources under moving conditions. In medium-frequency heat treatment, it is difficult to thoroughly heat the interior of welds of heavy-wall pipes, and blind zones of heating or overheating zones with latent defects are very readily present. To solve the electromagnetic-heating-induced latent defects, we researched the mode of heat transfer inside the welds with heat sources under motion conditions to determine the temperature field evolution, spatial magnetic field distribution, and spatial matching relationship in cases of dual heat sources interfering with each other, tangential to each other, and not interfering with each other. With the increase in the axial spacing between the internal and external heat sources, the magnetic field intensity at the middle of the thickest part of the welding seam on the steel pipe increased and then decreased. When the heat sources interfered with each other, the temperature rise at the weld center from electromagnetic heating was no longer fast after the Curie point was reached. The induced magnetic field heating concentration positions shifted toward both sides of the weld center. The latent defect area was reduced by 18.7 mm 2 when the spacing between the internal and external heat sources was 19 mm. This study explores the dual-heat-source interaction mechanism for the first time in the heat treatment of pipes to minimize the blind zones of heating and overheating zones.

Sour-Service Risers and Accessories for HP/HT Application in the Gulf of Mexico

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper OTC 30558, “Development and Implementation of Heavy-Wall, High-Strength, Sour-Service Accessory and Risers for HP/HT Application in the Gulf of Mexico,” by Carine Landier, Jonathas Oliveira, and Christelle Gomes, Vallourec, et al., prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4–7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. As oil and gas development in the Gulf of Mexico increasingly requires high-pressure/high-temperature (HP/HT) applications, the need for sour-service (SS) resistance also has grown. To meet these needs, continual innovation and improvement is needed in SS-grade materials from a technical and cost-effectiveness perspective. The complete paper discusses the material properties achieved with several large-diameter, heavy-wall SS pipes. The complete paper presents a detailed, illustrated discussion of the applications for the high-strength SS pipe and its manufacturing process. Applications The authors write that improved materials to meet HP/HT requirements such as those in the Gulf of Mexico are needed particularly for two applications: for risers, which require high-strength, thick-wall sour service; and as a substitute for corrosion-resistant alloy (CRA) with sour carbon material on defined accessories. Vallourec has developed high-strength [125,000-psi specified minimum yield strength (SMYS)] and resistant carbon steel pipes in sizes with outer diameter (OD) up to 23 in. and wall thickness up to 2.5 in. These sizes are common in lower-strength material, but meeting the high-pressure requirements with higher-grade material enables cost savings and eliminates some CRA components. It also enables the use of much-lighter-weight pipe than the 80,000-psi SMYS material that is standard for SS applications in oversize OD and heavy wall. Risers. Most deepwater drilling is performed with classic subsea blowout-preventer (BOP) systems. Access to the well through the BOP is accomplished with low-pressure, large-diameter (19-in. internal diameter) drilling riser pipe. Pipes are supplied in weldable grades (API 5L X65–X80). Large-diameter forged flanges are then welded onto the tubes. Connections are made by multiple bolts. High pressures, required as part of the drilling process, are supplied by small-diameter choke-and-kill lines. This system has served the industry well, but, as well pressures increase, so have cost and feasibility requirements of subsea BOP technology. These costs, driven by the complexity of redundant systems, have driven a desire to explore an alternative solution—a surface BOP with high-pressure drilling riser pipe. Using a surface BOP reduces the complexity and cost of the system significantly because of the ability to inspect it. The drilling riser then carries the pressure to the surface and must be able to contain it. The high-pressure environment that instigated a new solution was based on a 15,000-psi well pressure with NACE Region 2 SS performance. Because of the requirement for weldable grades for attaching the flange as well as SS, the maximum yield strength has been limited to 80,000 psi. At that strength, a very high wall thickness is required to meet 15,000 psi and greater. This becomes very heavy and can be limited by the rig hook-load capacity. Alternatives in weldable grades are nickel-based alloys with SS performance. A full string, however, is prohibitively expensive.

Study of the influence of stochastic inhomogeneity of a pipe on stress-strain behavior

The paper is devoted to stress-strain behavior of an elastic heavy-wall pipe from incompressible material, which is under the influence of compression hydrostatic pressure. We have obtained the analyticity condition for the solution of the problem in small parameters close to zero. These parameters are independent random variables. They characterize the deviation of the cross-section outline from a circle, and the inhomogeneity of the pipe material. The solution has been found by perturbation method up to the second order of smallness. It has been concluded that in the case of experimental analysis of the pipe state under the load meeting the specified condition, the average values of stress and displacement will be close to the values obtained at axially symmetric state.

DECISION SUPPORT SYSTEM ОF DESIGNING BOTTOM-HOLE ASSEMBLY FOR DIRECTIONAL WELL DRILLING

Background The authors study the development of decision support system (DSS) for designing the bottom-hole assembly (BHA) while drilling, as well as the development of software that implements the DSS. DSS includes expert system, knowledge base, analytics and modeling subsystem, database of drilling equipment. The analytics and modeling subsystems contain algorithms for drilling calculation of the optimal BHA parameters in accordance with the requirements for the well profile, rate of penetration and reduction of sticking danger. The authors discuss how to use the developed expert system as part of an automated control system for directional well drilling. The studied drilling equipment consists of: drill bits, calibrators, downhole screw motors, drilling jar, heavy-weight drill pipes and heavy-wall drill pipes. Analyzed the main parameters of drilling equipment affect sticking danger, rate of penetration and well trajectory. The developed database structure of drilling equipment allows you to calculate the above parameters. The result of the work of the decision-making software is a report defining the types and sequence of installation of the necessary downhole drilling equipment. Aims and Objectives For DSS development for the BHA designing while drilling is necessary to develop an expert system, a knowledge base, analysis and modeling subsystem, a database of drilling equipment to implement this DSS as a part of an automated control system for directional well drilling. Results The authors developed an ontological model for describing and choosing effective BHA design by the Protege software based on evaluation and analysis of the main attributes of BHA selection experience. The authors also developed the drilling equipment database structure for BHA equipment selection based on deductive inference mechanism for decision rules of the knowledge base.

Optimization of Thermal and Deformation Effect during Plastic Deformation and Thermal Treatment of Hot Rolled Heavy Wall Pipes Made of Medium Carbon Martensitic Steel

The method of stress relaxation in isothermal aging after deformation is employed to determine recrystallization temperature range (Trec) for 38HN3MFA (35HN3MFA) steel grade. The paper shows that billet final deformation at the temperature lower than Trec followed by annealing including heating and aging at Trec enables austenite grain refinement.

Dislocation Structure of the Pipe Made of Alloy Reinforced with Incoherent Particles Under Uniform Internal Pressure

The paper deals with the formation of the dislocation structure of a heavy-wall pipe made of dispersionhardened Cu-based alloy and subjected to the uniform internal pressure. The increasing generation of shear dislocations and prismatic dislocation loops lead to the expansion of the plastic range with the pressure growth. With increasing size of strengthening particles and decreasing distance between them, the elements of the dislocation structure begin to generate more intensively similar to the strength properties of the material.

Plastic Deformation of Copper-Based Alloy Reinforced with Incoherent Nanoparticles

The paper deals with research carried out into plastic deformation of a heavy-wall pipe made of nanoparticle reinforced copper-based alloy. We present an original approach which combines methods of crystal plasticity and deformable solid mechanics, thereby allowing to study the stress-strain state of the heavy-wall pipe strengthened with incoherent nanoparticles using a homogeneous internal pressure. Dependences are constructed for the yielding area and the pressure, the limit of elasto-plastic resistance is obtained for the heavy-wall pipe and its deformation degree is described. It is shown that the particle size has an effect on strength properties of the material.

Effect of tempering time on the mechanical properties of P91 flux cored wire weld metal

ASME Grade 91 is one of the main materials for heavy-wall pipes in thermal power plants. Matching flux cored wires for welding P91 have already been available for several years and become more and more popular as flux cored arc welding (FCAW) offers several technical and economic advantages. To achieve high toughness of the weld metal at ambient temperature, temperature and/or time of post-weld heat treatment (PWHT) can be increased. As the temperature has to be kept below the transformation temperature Ac1, the range of suitable temperature is very small. In this contribution, the effect of increased tempering time on the mechanical properties at ambient temperature and elevated temperatures is investigated and the influence on long-term properties is discussed. Longer PWHT increases toughness of all-weld metal. MatCalc simulations and scanning electron microscopy (SEM) investigations indicate a coarsening effect of precipitates without detrimental effect on long-term creep properties.

Effect of nitrogen in backing gas on duplex root weld properties of heavy-walled pipe

Duplex stainless steels are increasingly used for offshore subsea components as the technology allows for deeper recovery of oil and gas reserves. Alloy UNS S31803 (EN 1.4462/UNS S32205) combines high strength with good resistance to pitting and crevice corrosion. This grade is alloyed with nitrogen and has good weldability. For heavy-walled process piping intended for subsea sour service, the properties of the root pass are of high importance. For this reason, the effect of using nitrogen in the backing gas was investigated. Test pieces were manually welded with the gas tungsten arc welding (GTAW) process using an ER2209 filler wire. Tensile, bending and hardness testing was carried out and showed acceptable results across all specimens. Higher contents of nitrogen in the backing gas showed more austenite formation and a significant increase in pitting corrosion resistance when compared with pure argon. With Ar + 2 % N2, there was no pitting, but a small weight loss of 1.7 g/m2 was measured. 10 % N2 was required to pass both the corrosion tests ASTM G48 Method A (4 g/m2) and ASTM A923 (1 g/m2). The highest average impact toughness was achieved with pure nitrogen as the backing gas.

Characterization of the multi-pass weld metal and the impact of retained austenite obtained through intercritical heat treatment on low temperature toughness

In this study, we explore the relationship between the microstructure and low temperature toughness of weld metal obtained from a real multi-pass weld joint (up to 55mm) by submerged arc welding, which was developed for high strength (yield strength over 550MPa) and heavy wall pipe fitting applications with composition of 0.1wt% C, 2.0wt% Mn and other micro-alloys. The study indicated that the necklace-type coarse martensite–austenite (M–A) constituent formed in the interlayer heat affected zone (IHAZ) of weld metal was responsible for low impact energy of 39J at −40°C. To enhance the toughness, conventional tempering and new intercritical heat treatment were designed. The results suggested that there was insignificant effect on toughness through conventional tempering, but obvious improvement through combination of quenching plus intercritical annealing and tempering. The impact energy was increased to ~98J. The microstructure that benefit toughness primarily comprised of intercritical lath-like ferrite or acicular-type ferrite, bainite/martensite, and fine acicular retained austenite, with average size of ~0.3μm. Retained austenite with volume fraction of ~6% was formed by the enrichment of Mn and Ni in reversed austenite during intercritical tempering process.

Study of microstructural evolution and strength–toughness mechanism of heavy-wall induction bend pipe

The induction bending and subsequent tempering process has recently been proven to be an optimal technological route for the manufacture of bend pipe with a better combination of strength and toughness. In this work, high temperature quenching followed by tempering treatment from 500°C to 700°C has been applied to heavy-wall bend pipe steel produced by the ultra fast cooling technology. The evolutions of microstructure and dislocation were characterized by means of an optical microscope, the positron annihilation technique (PAT), SEM, TEM, XRD and EBSD. Microstructure observations showed that fine and homogenous M/A islands as well as dislocation packages in a quasi-polygonal ferrite (QPF) matrix after tempering at 600–650°C generated an optimal combination of strength and toughness. At higher tempering temperature, the yield strength decreased dramatically; however, the impact toughness still remained at a high value of more than 300J. Dislocation analysis by means of TEM, EBSD and PAT suggested that the decrease and pile-up of dislocation could provide better toughness and tempering stability. EBSD analysis indicated that the average misorientation angle enlarged and the effective grain size diminished with the tempering temperature increasing, and these caused more energy cost during the microcrack propagation process with subsequent improvement in impact toughness. Microcracks mainly originated from the interfaces between ferrite matrix and M/A islands. The ring-type join-up of microcracks and the large number of branches formed during the propagation process effectively improved the toughness. All these results benefit the cost-effective commercialization of heavy-wall induction bend pipe with high performance.

Numerical Analysis of Hot Cracking in Laser-Hybrid Welded Tubes

In welding experiments conducted on heavy wall pipes, the penetration mode (full or partial penetration) occurred to be a significant factor influencing appearance of solidification cracks. To explain the observed phenomena and support further optimization of manufacturing processes, a computational model was developed, which used a sophisticated strategy to model the material. High stresses emerged in the models in regions which showed cracking during experiments. In partial penetration welding, they were caused by the prevention of weld shrinkage due to the cold and strong material below the joint. Another identified factor having an influence on high stress localization is bulging of the weld.

Pore pressure changes accompanying exchange sorption of CO2/CH4 in a coal briquette

The paper presents the study of CO2/CH4 exchange sorption in a coal briquette. The briquette was formed inside a heavy-walled steel pipe that served the purpose of a measuring chamber. The briquette with a porosity of 8.3%, a diameter of 0.096m and a length of 0.280m was used. Three laboratory experiments were conducted. The experiments consisted in CO2 injecting onto the input of the briquette previously saturated with CH4. In each experiment, during the exchange sorption process, the input CO2 pressure and output gas mixture pressure were stabilized at the level of 11, 12 and 13bar at the input and 10bar at the output of the briquette. Pressure changes along the briquette and concentration of the gas mixture flowing out of the briquette were analyzed. It was observed that a pore pressure depression moving along the briquette accompanies the exchange sorption. The presence of the pore pressure depression indicated existence of a separated zone where exchange sorption takes place. It was also observed that from the moment that CO2 appeared at the output of the briquette, sudden changes of its concentration were recorded. This phenomenon confirms the thesis of the exchange zone occurrence accompanying the CO2/CH4 exchange sorption in the briquette. A description method of the observed phenomenon was proposed.

Residual Stress Measurement of Large-Bore Stainless Steel Pipe with Butt-Welded Joint by Inherent Strain Method

This study describes residual stress distribution of large-bore and heavy-walled stainless steel pipe with butt-welded joint as measured by inherent strain method with distribution function in which the inherent strain distribution is represented as function. The deviation of the most probable residual stress value obtained by the method was enough small to indicate accurate measurement. The detail feature and 3D-distribution of the residual stress generated within the heavy-walled pipe with welded joint were discussed on two variously-sized pipe joints. It was found that the residual stress distribution had more complicated shape as the bore and thickness of the pipe was larger.

G030034 固有ひずみ法を用いた大口径原子力配管溶接継手の残留応力測定([G03003]材料力学部門一般セッション(3):残留応力)

Three-dimensional distribution of weld residual stress in a large-bore and heavy-walled stainless pipe with butt-welded joint was evaluated by inherent strain method with distribution function. The weld joint was made by TIG welding with single-U shape groove and its size is used in the primary coolant system in nuclear power facilities. The residual stress distribution in the circumferential direction as well as in the through-thickness direction of the joint was estimated using the measurement values obtained in the multiple positions. It was clarified that the three-dimensional stress distribution in the weld end was different from that in the other region.

A Simulation Technology for a Full Cycle of Steel Line Pipe Manufacturing Operations

At present day, pipe mill engineers have to deal with challenging technological problems of heavy-wall and high-strength line pipe manufacturing. Numerical analysis of welded large-diameter pipe manufacturing stages is the most efficient way to solve these problems. Corresponding computational technologies and applied software were developed at Physical &amp; Technical Center. Numerical structural analysis of steel plates at various stages of line pipe manufacturing is performed by the finite element method, accounting for geometric and material nonlinearities. The only thing to be done by the engineer in such analysis is to specify required input parameters. All the further process is software controlled. The discrepancy between the numerical analysis results and measured data in the overwhelming majority cases did not exceed 1%.

Guided Side-Bend: An Alternative Qualification Method for Butt Fusion Joining of Polyethylene Pipe and Fittings

Abstract Historically, the procedure for butt fusion joining of polyethylene pipe has been qualified on the basis of two fundamental tests that are widely recognized within the industry. These are the tensile-impact (T-I) test method found in ASTM F2634-07 and the reverse-bend (RB) or bend-back test as described in ASTM F2620-06. Both of these test methods have been extensively utilized within the industry, and both have some specific limitations as it relates to qualification of butt fusion joining conducted in the field. ASTM F2634-07 is a highly sophisticated testing method involving precision instrumented laboratory equipment. This makes it impractical for an on-site qualification for butt fusion procedures in the field. The bend-back test, on the other hand, lends itself to field implementation, but as the method is applied to a larger diameter, heavy-walled pipe, the practicality of performing the test and safety considerations become a limiting factor. This paper will examine an alternative test method referred to as guided side-bend or full-face testing that appears very promising as an alternative to the RB test as described in ASTM F2620-06. The test method will be fully described, and data will be presented comparing T-I results and traditional bend-back results to those obtained using the side-bend test method. The discussion of the test results and safety considerations of the proposed test method will be addressed, and conclusions will be drawn regarding its future applicability.

1031 固有ひずみ法を用いた大口径ステンレス鋼配管突合せ溶接継手の残留応力(OS10-8 供用エネルギー機器の経年変化と健全性評価-残留応力-)

This study describes residual stress distribution of large-bore and heavy-walled stainless steel pipe with butt-welded joint as measured by inherent strain method in the form of function, in which the inherent strain distribution is represented in the form of function. The deviation of the most probable residual stress value was small indicating accurate measurement. The detail feature and 3D-distribution of the residual stress generated within the heavy-walled pipe with welded joint can be evaluated in this method. It was found that the residual stress distribution had more complicated shape as the aperture and thickness of the pipe was larger.

Theoretical analysis of current distribution in electric resistance welding.

In order to manufacture a fairly heavy walled pipe, the distribution of the electric current in the strip edge of Vee apex zone was analyzed by comparing the measured and calculated electric circuit constants in Vee apex zone.From the result of the analysis it can be concluded that the current in strip edges has a tendency to flow uniformly as the strip thickness increases and, also, that the overheat at the corner of strip edges can be reduced to an allowable level by employing a small apex angle and mild welding condition.In addition, it is found that the large amount of upset is needed to obtain a sound quality of welding. So, the proper welding conditions of heavy wall are selected to be as follows, mild welding condition, i.e., slow welding speed, small apex angle and large amount of upset. A fairly heavy walled ERW pipe with large outside diameter of 24inchφ×19.05t are manufactured by applying the proper conditions. The toughness of the weld part is proved to have excellent toughness.