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Metals & Mining
Effect of Microstructure on Hydrogen Diffusivity, Trapping and HIC Resistance in Two API X65 Steels
Pereira, Viviam Serra Marques (University of São Paulo) | Hincapie-Ladino, Duberney (University of São Paulo) | Nishikawa, Lucas Pintol (University of São Paulo) | Goldenstein, Helio (University of São Paulo)
Abstract The paper compares Hydrogen Induced Cracking (HIC) resistance and Hydrogen Permeation (HP) results for two API X65 microalloyed steels, with different contents of Mn and Nb: one containing low Mn and high Nb (L-Mn) and the other, high Mn and low Nb (H-Mn). The main objective is to correlate the microstructural differences between these steels with hydrogen diffusion and trapping behavior and hydrogen-induced cracking resistance. Both steel plates were characterized with optical and scanning electron microscopy in their transverse sections, in relation to the rolling direction. HIC resistance tests were made in accordance with the NACE TM0284-11 standard; samples obtained from the transverse section were also submitted to Hydrogen Permeation tests, based on the ASTM G148-97 standard. NACE solution A saturated with H2S was used in the two procedures. Besides, Thermal Desorption Spectroscopy measurements were made, in order to show which steel trapped more hydrogen atoms, and carbides/carbonitrides volume fractions were estimated with ThermoCalc software. The L-Mn steel presents a homogeneous microstructure through the plate thickness, composed of refined ferrite and small pearlite islands. The H-Mn steel has a heterogeneous microstructure through the plate thickness, composed of ferrite and pearlite bands, and presents centerline segregation. Hydrogen permeation tests showed that, despite all the microstructural differences, the hydrogen effective diffusion coefficient (Deff) was almost the same for both steels – the Deff obtained for the L-Mn steel is slightly higher than for the H-Mn steel. Contrary to expectations, the L-Mn steel presented higher hydrogen subsurface concentration (C0) and number of trapping sites per unit volume (Nt) values. Thermal Desorption Spectroscopy analysis confirmed that the L-Mn steel traps more H atoms than the H-Mn one. These results, along with the similar Deff values, can be explained by the presence of nanoprecipitates of microalloying elements, which, according to ThermoCalc simulations, appear in higher volume fraction in the L-Mn steel. Finally, the HIC tests results showed that the L-Mn steel has a better performance in sour environments; this behaviour is related with its special microstructural features.
Investigation of Electroless Nickel-Phosphorus Coating as an Alternative to Corrosion/Fouling Resistant Alloys in Downhole Service
Zhu, Da (RGL Reservoir Management Inc.) | Uzcategui, Alberto (RGL Reservoir Management Inc.) | Gong, Lu (University of Alberta) | Qiu, Xiaoyong (University of Alberta) | Huang, Jun (University of Alberta) | Sun, Chong (University of Alberta) | Luo, Jing-Li (University of Alberta) | Zeng, Hongbo (University of Alberta)
Abstract Harsh physical and chemical environments found in downhole operations have traditionally required the use of exotic corrosion-resistant materials, which are expensive, difficult to source and challenging to machine. This paper evaluates high-phosphorous electroless nickel (EN) coating as an alternative to these materials. The performance of this coating on carbon steel is compared to the performance of corrosion resistant alloys for fouling and surface characterization, and adhesion of inorganic and organic materials in a series of laboratory and field tests. In this paper, we first describe the complex and hostile thermal-chemical environment that exists for well completions commonly used in oil and gas production. The chemistry, physics and engineering governing principles of corrosion and fouling are reviewed. The set-up of the laboratory facilities and test procedures for fouling are described in detail. The performance of EN coated carbon steel is compared to several corrosion resistant alloys commonly used in downhole operations: 13Cr-L80, 28Cr-L80, 316L stainless steel, and Inconel 625. Examination of these specimens indicates the extent of corrosion and accumulation of fouling substances on EN coated and uncoated carbon steel at each time point.
Study of the Mechanical Properties and Fracture Morphology of Niobium Microalloyed 80 ksi Class Thick Plates Produced by Controlled Rolling Followed by Accelerated Cooling
Viana, R. T. (Gerdau Ouro Branco) | Gorni, A. A. (Gerdau Ouro Branco) | da Silveira, J.H.D. (Gerdau Ouro Branco) | Camey, K. (Gerdau Ouro Branco) | de Faria, R. J. (Gerdau Ouro Branco)
Abstract This paper describes the first production trials of 80 ksi class thermomechanically controlled processing (TMCP) thick plates at the new Gerdau Ouro Branco plate mill. These trials were very successful, as the product fully satisfied the mechanical properties requirements for such grade, enabling the start of commercial delivery of this material. In addition, experience gained in this process will promote further technological improvement of this class of products, as well more sophisticated plates. The occurrence of separations in the fractured surface of Charpy specimens was considered with detail.
Abstract In recent times, demand for steels, such as H-shaped steel for offshore structures for the world energy market is rapidly increasing. Such beams are often manufactured with steel plates and are welded to ensure the toughness, which is represented with Charpy V-notch energy, at low temperatures of -40 °C in H-shape steel. However, welded beams have several disadvantages, e.g., requirements of cost and operation period for welding fabrications and inspections and quality control in heat affected zones. Rolled H-shape steels enable to overcome these difficulties if they satisfy the mechanical property requirements such as Charpy V-notch absorbed energy at -40 °C. In previous studies, grain refinement by facilitating intragranular ferrite nucleation on inclusions in steels has been analyzed to improve strength and toughness. For example, vanadium-nitride is reported to be particularly capable as ferrite nucleation sites. Furthermore, precipitates and inclusions can be useful for rolled H-shapes to improve the toughness by the refinement of ferrite grains. Chemical composition, particularly of microalloying elements, which form precipitates and inclusions, has to be carefully optimized to satisfy alloy ranges identified in EN10225 classification. This study attempts to reveal the effects of microalloying elements in H-shapes for the low temperature applications. Series of experimental ingots were casted in a vacuum melting furnace and were laboratory rolled to plates. These test materials were investigated by mechanical tests and metallographic observations such as optical and transmission electron microscopy. The results of these experiments suggested that the toughness can be improved by the ferrite refinement using vanadium-containing nitrides on prior austenite grain boundaries. Based on these experimental results, actual H-shapes were examined in the practical production line and it was confirmed that these results could meet the EN10225 Class S355 classification, where the Charpy V-notch minimum average impact energy at -40 °C required were 50 J in base metals and 36 J in weld heat affected zones.
Influence of the Gas Protection Composition on Dilution of 4130 80K Material Overlaid with 625 Alloy by Hot Twin Wire GTAW Process
Filho, M. A. Deitos (Universidade Tecnológica Federal do Paraná) | Maranho, O. (Universidade Tecnológica Federal do Paraná) | Gandelman, A. (Universidade Tecnológica Federal do Paraná) | Santana, A. Beltrao (Universidade Tecnológica Federal do Paraná)
Inconel 625 is a nickel-based alloy used in oil and gas equipment due to its outstanding corrosion resistance in seawater, chloride-containing environments, and mainly due to corrosion resistance against the production fluid coming from the reservoirs. However, since Inconel 625 is a high-alloyed material, quite more expensive than low-alloy steels used on most parts of christmas trees and other subsea equipment, their use is desired to be optimized as much as possible. One technique largely employed in the oil and gas industry is the cladding of less noble materials with alloy 625 by Gas tungsten arc welding (GTAW) process. The optimization of the weld dilution of overlays together to the quantity of deposited filler metal is a subjected under study for several researchers around the world, however, not much literature is found about this type of study for Inconel 625 by GTAW hot wire method. This work aims to help academic and oil and gas business community providing information related to alloy 625 overlay welding. Weld beads of Inconel 625 (ERNiCrMo-3) were deposited on AISI 4130 80k by GTAW twin hot wire process, with three shielding gas compositions. The usage of helium on gas mixtures utilized on this work showed two antagonistic behaviors regarding the improvement of the quantity of filler metal used and the weld dilution. The smallest reinforcement was obtained with the highest quantity of helium on shielding gas mixture, while highest amount of helium caused an increase in the weld penetration, and thus in the dilution. Pure argon showed the best dilution results, but bigger reinforcement than helium high amounted shielding gas mixture.
- South America > Brazil (0.69)
- North America > United States (0.47)
Abstract Many offshore oil & gas reservoirs contain unwanted components that complicate the safe transportation of the hydro carbons to onshore refineries. Over time these unfavorable constituents corrode unprotected carbon steel pipelines. In 2013 a pipeline failed in the Caspian Sea within weeks under operational conditions. This high profile failure has already caused many oil companies to rethink their established methodology for pipe lines. Using cladded pipes is a method to safely transport contaminated oil & gas from the well to the cleaning facility. There are various ways to clad pipes with a variety of corrosion resistant alloys (CRA). One category of methods is based on cladding a plate which subsequently is formed to a pipe. The hot roll bonding process is the most dominant route. The second common category of methods is a pipe in pipe solution which is referred to as mechanically cladded pipe. Both groups of methods have their benefits as well as disadvantages but both are industrially proven. There is a third way to produce clad pipes which can be classified between the two aforementioned categories above. This method starts with a carbon steel plate and CRA strip material so the cladding forms part of the pipe forming process. As this new technique produces a clad pipe product which, from a technical perspective, is situated between the established clad pipe methods, it is called Hybrid Clad®. The resulting bonding strength between the carbon steel and the CRA layer is significantly above that of existing mechanically cladded solutions but lower than metallurgical bonded clad variants. This paper will provide details of clad pipe manufacture using this new method of production whilst emphasizing the key steps which influence product quality. Secondly, the main benefits and disadvantages of the established clad pipe production methods will be compared with each other and the Hybrid Clad® solution. This comparison is intended to identify the preferred clad pipe product to provide a solution to transportation problems.
Advanced Forging Process (AFPTM), Super Duplex Stainless Steel for Increased Low Temperature Impact Toughness and Resistance to Hydrogen Induced Stress Corrosion Cracking (HISCC) Due to Cathodic Protection of API Forgings for Subsea Applications
Francis, R (RF Materials) | Byrne, Dr. Glenn (Rolled Alloys) | Warburton, Geoff (NeoNickel) | Schulz, Zach John (Rolled Alloys)
Abstract As oil wells become deeper and run at higher temperatures and pressures, there becomes a need for high strength, corrosion resistant material that will withstand the more severe service conditions of these projects. Over the years many projects in various locations around the world have successfully used duplex and super duplex stainless steels for subsea pipe lines, flow loops, flow lines and manifolds to contain the high temperatures and pressures and more demanding corrosive service required with the High Temperature High Pressure (HTHP) wells. Additionally, operators have realized that they need to qualify the manufacturers of these materials following a number of problems experienced in the field. They see that the more severe conditions require a higher level of quality and security to go with the more demanding performance required. As such, the NORSOK M650 specification is seen as way to qualify the manufacturer and ensure a higher level of quality in the product. This has not solved all problems and a few operators are placing even greater demands on manufacturers to ensure they have the required metallurgical understanding and production facilities to produce parts in these more complicated alloys. There is also a recent development for super duplex stainless steels to meet service conditions beyond usual requirements. A number of operators have projects where minimum design temperatures are calculated to be as low as −70°C, which is near the lower shelf toughness level for duplex stainless steels. This paper discusses the properties that can be achieved by optimizing the forging route and therefore minimizing nitride precipitation in these alloys. The resultant properties are sufficient to meet the impact properties typically required at temperatures down to −70°C. In addition, the improved ductility and toughness also increase the resistance to HISCC due to cathodic protection. Several end users and OEM's have already used ZERON 100 AFP to benefit from the improved toughness at design temperatures as low as −70°C. This paper will cover the metallurgy of duplex alloys and how improved understanding and processing can lead to less nitride precipitation, better morphology and austenite spacing that will have a beneficial effect on both toughness and HISCC resistance. The improved toughness values can also be seen across the full temperature range of most Oil & Gas projects with excellent properties at −50°C as well as at −70°C. Discussion of a few case histories also confirms the need for application of this Advanced Forging Process (AFP) of super duplex stainless steel.
Abstract The cellular tendon concept described in this paper is an enabling technology proposed for Tension Leg Platforms (TLP) to meet the industry's demands for producing oil and gas in ultra-deep waters beyond 1500 m. The technical merits of the concept for ultra-deepwater field development have been demonstrated in this paper using TLPs with representative large, medium or small payloads in water depths between 1,500 and 3,000 meters. The technical readiness is enhanced by using mature industry products for tendon components, and by adapting existing industry practices to construct and install the Cellular Tendons. The Cellular Tendon has advantages over conventional tendons in technical robustness and economics of the project, as well as enabling/enhancing local fabrication content. The intellectual property of this design concept is protected under a pending global patent. Background Historically, TLPs are ideal platforms for deep water drilling and oil and gas production with dry trees worldwide. Currently there are over a dozen TLPs installed in regions including the GOM, Southeast Asia, and West Africa. Several TLPs are planned for installation in the GOM, North Sea and Brazil in the near future. The application of TLPs with a conventional tendon system has reached technical and economical limit for water depths beyond 1,500 meters. For a TLP in ultra-deep water, the technical and commercial practicality is constrained by the feasibility of the tendon main body and it meeting stiffness and collapse requirements. Also, the cost of conventional tendon installation in certain regions is sometimes prohibitive for the commercial viability of the project. Design of the Cellular Tendon System The Cellular Tendon concept has the same main components as a conventional tendon. A conventional tendon consists of three major parts: a tendon top segment (TTS) interfaces with the platform, a tendon bottom segment (TBS) connects to the tendon foundation at the seafloor, and a main body that links the two through the water column. The Cellular Tendon innovation resides in the design of the main body. Instead of one pipe, it consists of multiple metallic tubules. It also has an upper transition unit to interface with the TTS and a bottom transition unit to interface with the TBS. The top and bottom interfaces—TTS and TBS--are kept the same as in conventional tendons. The same tension-monitoring units in the conventional tendons can be used in the Cellular Tendons as well. Figure 1 is the elevation view of the TLP moored to seabed by the tendons. The tendons are connected to the tendon porch through the top interface and the foundation through the bottom interface. Figure 2 is the schematic of the Cellular Tendon system. Unlike the single carbon steel pipe used as the main body in a convention tendon design, the main body consists of multiple metallic tubular strings. Each individual string is composed of pipes butt welded at their ends. All the strings are arranged in parallel and assembled on-shore. The pipe material can be carbon steel or aluminum. Conventional carbon steel pipes have been used in many existing TLP tendons are considered mature industry practice and are preferred to be used first in the field development. The number of strings in the main body is designed to meet the stiffness requirements, strength requirements, fatigue requirements, and to be practical for fabrication and installation. The outer diameter and/or wall thickness of the pipes can vary along the string. In general, the OD of the pipes is smaller and /or the pipe wall thickness is increased for those segments at greater water depths.
- South America > Brazil (0.67)
- Africa (0.55)
- Europe > United Kingdom > North Sea (0.24)
- (3 more...)
- North America > Cuba > Gulf of Mexico (0.89)
- Europe > United Kingdom > North Sea (0.89)
- Europe > Norway > North Sea (0.89)
- (2 more...)
Abstract The SDSS have been increasingly used in the offshore industry due to their excellent mechanical properties and corrosion resistance properties to the media they are exposed to. The SDSS are mainly used in subsea components such as Christmas Trees, Manifolds, BOP and also for Topside Modules in Platforms. A well balanced chemical composition guarantees the outstanding corrosion and mechanical properties of SDSS material. Ferrite forming elements such as Cr, Mo ensure a high resistance to chloride containing media as well as a high strength. Austenite forming elements Ni and Ni balance the microstructure to 50%. However, the thermal instability increases with the amount of elements and restricts the weldability compared to usual stainless weld metal of the 3xx series. In particular the GMA-, and SA welding process asks for a specific approach to minimize the tendency to pore formation. This report describes the influence of a fine tuned chemical composition and welding parameters to achieve a sound weld metal along with an optimum in corrosion resistance. 1 Superduplex Stainless Steels Superduplex Stainless Steels are materials characterized by a microstructure of austenite and ferrite, figure 1. Driven mainly by the offshore industry to increase the corrosion resistance and the mechanical properties enhancement of the conventional Duplex Steels has led to the so called Superduplex Stainless Steels. Main (Super) Duplex Steels are UNS 35750 and 35760. An overview of the chemical composition of usual Duplex steels is given in table 1. These steels are featured, compared to the conventional Duplex grades, by increased contents in Cr (22–25%), Mo (2–4%) and N (0,2 -0,35%), with possible additions of Cu and W. These increased contents lead to a higher corrosion equivalent (Pitting-Index PREN =% Cr + 3,3 % Mo + (0,5 % W) + 16 % N). This does not only improve the pitting (crevice) corrosion resistance in the as welded condition but is beneficial for a higher strength level as well. Superduplex Stainless Steels show a PREn > 40. The heat affected zone (HAZ) was already experienced as the weakest part in conventional Duplex joints. A sufficient high N-content (> 0,20%) is badly required, to control embrittlement by grain grow and increased ferrite contents in the heat affected zone, even more for Superduplex Stainless steels.
Development of X70 and Heavy Wall X65 Plates For Sour Service Pipeline Application
Bauer, Juergen (Aktien-Gesellschaft der Dillinger Huettenwerke) | Collura, Carmelo (Aktien-Gesellschaft der Dillinger Huettenwerke) | Schwinn, Volker (Aktien-Gesellschaft der Dillinger Huettenwerke) | Staudt, Thorsten (Aktien-Gesellschaft der Dillinger Huettenwerke) | Clipet, David (GTS Industries) | Amoris, Eric (GTS Industries)
Abstract Brazil due to its extraordinary oil and gas fields is one of the upcoming future markets for heavy plates for sour service applications. Such heavy plates are steels with high-class quality demands. Depending on the quality of the sources the HIC (Hydrogen Induced Cracking) resistance is a special requirement of these steels. By minimizing the HIC crack initiation sites as well as the crack propagation the HIC resistance is accessible. To achieve this, a careful design of all micro-structural features of the steel is necessary. The utilization of the latest technology for steel and plate making is the central element of the production of such steels. Suitable metallurgical processes like clean steel treatment, casting in a technically sophisticated manner as well as special rolling techniques like the TMCP (Thermo-Mechanical Controlled Process) combined with suitable ACC (Accelerated Cooling) after final rolling provide the fundamentals of a homogeneous and resistance microstructure, especially with low level of imperfections, mainly non-metallic inclusions as well as reduced mid-thickness segregations. The paper will point out the integrated overall production concept which provides the basis for the production of steel plates with consistent and reliable HIC resistance. The essential parameters will be explained, including the utilization of an appropriate quality assurance system. The second part of the paper will focus on the gradual development to the strength level of grade API-5L X70 and higher wall thickness of grade API-5L X65. The feasibility of the production of such steels will be demonstrated by the presentation of recent deliveries, also interesting for the Brazilian market. Introduction The most line pipe projects with full sour service applications use the already established API-5L X65. But the still growing global demand on crude oil and natural gas and the involved shortage of the resources necessitate the exploitation of resources under more difficult conditions. Especially for the Brazilian oil and gas pipe market with its important resources in deep sea areas heavy wall API-5L X65 and/or API-5L X70 for full sour service are very meaningful for economically efficient as well as safe exploitation. From the point of costs it is also important to go to higher strength instead of enhancing wall thickness to manage high external pressure linked with deep sea areas. That is why all heavy plate producers in the world invest a lot of efforts in research and development of high strength line pipe grades for full sour applications [1–4].