Search Results for flux-cored arc welding

The toughness of girth welds in 9Cr-1Mo-V and 9Cr-0.5Mo-V steel seamless pipe (ASME SA-335 Grades P91 and P92, respectively) made using the flux-cored arc welding (FCAW) process was evaluated. Electrodes from two different suppliers were used for production quality welding of each steel. The welds received post-weld heat-treatment (PWHT) in accordance with the requirements of the ASME Code. The objective of the work was to determine if the fracture toughness of the FCAW welds was acceptable for high-temperature steam piping. Toughness was measured using standard sized Charpy V-notch impact specimens. The specimens were oriented transverse to the weld seam with notch located approximately in the center of the weld metal and parallel to the direction of weld seam. Full-range (lower to upper shelf) Charpy impact energy and shear area curves were developed for each weld joint. These were used to estimate the temperatures corresponding to 30 ft-lb average impact energy. The estimated temperatures were well below the service temperature but were above the typical hydrostatic test temperature.

As flux cored wires for gas metal arc welding offer several technical and economic advantages they are becoming more and more popular. Matching flux cored wires for welding P92 have already been available for several years. A matching flux cored wire for welding the Co-alloyed cast steel CB2, which is used for turbine and valve casings operating at steam temperatures of up to 620°C, was developed recently. To connect casings with P92 pipes, dissimilar welding of CB2 to P92 is necessary. This can be done with filler metal that matches either CB2 or P92. Pre-tests have confirmed that flux cored arc welding (FCAW) can generally be used for dissimilar joint welding of CB2 to P92. To evaluate creep rupture strength dissimilar welds were performed with filler metal matching CB2 and P92, respectively. TIG welding was used for the root and the second pass and FCAW for the intermediate and final passes. Cross-weld tensile tests, side bend tests and impact tests of weld metals and heat-affected zones were carried out at ambient temperatures after two post-weld heat treatments (PWHT), each at 730°C for 12 hours. Creep rupture tests of cross-weld samples were performed at 625°C. This study compares the results of the mechanical tests at ambient temperature and the creep rupture tests, and discusses why P92 filler metals are preferred for such welds.

The use of flux-cored arc welding (FCAW) is rapidly gaining acceptance in a variety of industries. Much of the gains are due to advances in manufacturing technology that result in superior wires that satisfy both technical and operability concerns. Additionally, productivity gains and the ability to use unsophisticated welding equipment have made these wires very popular. This paper concentrates on FCAW wires that have been formulated to address chromium-molybdenum, nickel base, and stainless steels for high-temperature and environmental applications. Mechanical properties, including creep rupture strength and ductility data, as well as corrosion in environmental components, are discussed.

Flux cored wires are worldwide used in power generation industry due to their technical and economic advantages. For welding P91 and P92 flux cored wires with a rutile slag system are available for several years. Results of long-term investigations up to 30.000 h show that specimens of all weld metal meet the requirements of the base material. Following the recent demand of reduced Mn+Ni content the chemical composition of all weld metal has been modified. For P91 a matching flux cored wire with Mn+Ni<1wt% and for P92 with Mn+Ni<1.2wt% is now available. In this paper the mechanical properties of all weld metal and welded joints are being presented. Latest developments in cast materials have shown that the so-called CB2 (GX13CrMoCoVNbNB 10-1-1) enables steam temperatures up to 620°C (1148°F). Therefore a matching flux cored wire with low Ni-content has been developed. Results of welding procedure qualification and first experience of manufacturing industrial components show the successful implementation of this new material grade and welding consumable.

Achieving high temperature creep strength while maintaining rupture ductility in weld metal for austenitic stainless steel weldments has always been challenging. In the late 1940's and early 1950's, independent work in both Europe and the USA resulting in what is known today as the 16-8-2 (nominally16% chromium -8% nickel -2% molybdenum) stainless steel weld metal. Philo 6 and shortly thereafter at Eddystone used the alloy to construct the first supercritical boilers and piping in the USA. Concurrent with domestic boiler and piping fabrication, the US Navy was also using this material for similar supercritical applications. Over the decades, enhanced performance has evolved with variations of the basic composition and by adding specific residual elements. Controlled additions of P, B, V, Nb and Ti have been found to greatly enhance elevated temperature as well as cryogenic behavior. The history of these developments, example compositions and areas of use as well as mechanical property results are presented.

Despite the significant progress achieved in power generation technologies in the past two decades, finding effective solutions to further reduce emissions of harmful gases from thermal power plant still remains the major challenge for the power generation industry as well as alloy material developers. In the European material programmes COST 522 and COST 536, based on the existing 9-12%Cr creep resisting steels, an advanced 9%Cr-Mo martensitic alloy, C(F)B2 (GX13CrMoCoVNbNB9-2-1) alloy has been developed. By modification through alloying of boron and cobalt and together with other micro-adjustment of the composition, C(F)B2 alloys has showed very encouraging properties. The current paper summaries the development and evaluation of the matching filler metals for C(F)B2 grade. The design of the filler metal composition is discussed and comparison is made with the parent materials in respect to the alloy additions and microstructure. The mechanical properties of the weld metals at ambient temperature are examined. Creep properties of both undiluted weld metals and cross-weld joints are examined through stress rupture test and the data are evaluated and compared with those of the base alloy and other existing 9%Cr-Mo creep resisting steels.

This study addresses the welding challenges encountered when joining Haynes 282, a heat-resistant superalloy, to 3.5NiCrMoV high-strength low alloy steel (HSLA) for advanced power plant applications, particularly in thick-section components like rotors. The project demonstrated successful thick-section dissimilar metal welding up to 76 mm (3 in.) using two techniques: keyhole tungsten inert gas welding and conventional gas tungsten arc welding with Haynes 282 filler metal. Various groove weld geometries were evaluated, supported by computational weld modeling to predict and minimize weld distortion. The results validate these welding approaches for critical power plant components requiring both high-temperature performance and cost-effectiveness.

This paper explores the development and qualification of a bainitic-martensitic steel grade and its matching welding consumables for power plants operating under ultra-supercritical steam conditions (605/625°C and 300/80 bar). It provides insights into recent developments and offers practical considerations for handling this material (grade T24) from the perspective of both tubular component manufacturers and welding consumable producers. The paper is structured into three main sections: (1) Development and qualification of the T24 steel base material. (2) Development, qualification, and recommendations for welding consumables compatible with T24 steel. (3) Experiences during manufacturing and installation of components using T24 steel, concluding with key takeaways.

Early supercritical units such as American Electric Power (AEP) Philo U6, the world’s first supercritical power plant, and Eddystone U1 successfully operated at ultrasupercritical (USC) levels. However due to the unavailability of metals that could tolerate these extreme temperatures, operation at these levels could not be sustained and units were operated for many years at reduced steam (supercritical) conditions. Today, recently developed creep strength enhanced ferritic (CSEF) steels, advanced austenitic stainless steels, and nickel based alloys are used in the components of the steam generator, turbine and piping systems that are exposed to high temperature steam. These materials can perform under these prolonged high temperature operating conditions, rendering USC no longer a goal, but a practical design basis. This paper identifies the engineering challenges associated with designing, constructing and operating the first USC unit in the United States, AEP’s John W. Turk, Jr. Power Plant (AEP Turk), including fabrication and installation requirements of CSEF alloys, fabrication and operating requirements for stainless steels, and life management of high temperature components

This paper addresses the limitations of P92 steel used in ultra-supercritical power plants, particularly ferrite formation in thick components and its impact on short- and long-term properties. A guideline for determining ferritic content in P92 steel is presented. Furthermore, a novel 12% Cr boiler steel grade, VM12-SHC, is introduced. This new material offers good creep properties and oxidation resistance, overcoming the limitations of P92 steel. Finally, the development of matching filler metals for welding P92 and VM12-SHC steels is presented, ensuring optimal weld compatibility and performance in power plant applications.

Inconel Filler Metal 72 (FM 72) and Incoclad 671/800H co-extruded tubing have been successfully used for over 20 years to protect boiler tubing from high-temperature degradation. A newer alloy, FM 72M, offers superior weldability and the lowest corrosion rate in simulated low NOx environments. Both FM 72 and 72M show promise in addressing challenges like circumferential cracking and corrosion fatigue in waterwall tubing overlays. Additionally, 72M’s superior wear resistance makes it ideal for replacing erosion shields in superheater and reheater tubing. Beyond improved protection, these alloys exhibit increased hardness and thermal conductivity over time, leading to reduced temperature difference across the tube wall and consequently, enhanced boiler efficiency and lower maintenance costs. This paper discusses the historical selection of optimal alloys for waterwall and upper boiler tubing overlays, analyzes past failure mechanisms, and highlights the key properties of successful choices like FM 72 and 72M.

The presented work summarizes the results of more than 10 years of research at TU Graz and TU Chemnitz and partners on a martensitic boron and nitrogen stabilized 9Cr3W3Co (MARBN) steel grade. The design philosophy of MARBN steels is presented and critical issues regarding boron and nitrogen balance are discussed. Microstructural characterization of two different laboratory heats, is presented and efforts in European projects towards an upscaling of melts are presented. Base material creep testing data at 650 °C up to 50.000 hours is presented and assessed to commercial alloys such as ASTM grades P91 and P92. An increase of creep rupture stress of more than +20% was recorded. Oxidation tests in steam at 650°C revealed an anomalous response of the material. Several specimens exhibited excellent oxidation resistance commonly only seen for grades of higher chromium content. The anomalous oxidation behaviour is identified and discussed, although the causes remain yet unclear. Results of manufacturing, characterization and testing of different MARBN welds, including gas-tungsten-arc-, gas-metal-arc-, friction stir and electron beam welds reveal a microstructure memory effect in the heat affected zone, so that no uniform fine-grained zone is present. The behaviour of crosswelds during long-term creep testing at 650 °C up to more than 32.000 hours is assessed and the susceptibility to Type IV cracking is discussed. The manuscript summarizes research of more than 10 years, presents current research activities on MARBN and describes open questions for an alloy identified as a promising martensitic steel grade for elevated temperature components.

The INCONEL filler metals 72 and 72M have been utilized significantly for weld overlay protection of superheaters and reheaters, offering enhanced corrosion and erosion resistance in this service. Laboratory data conducted under simulated low-NOx combustion conditions, field exposure experience, and laboratory analysis (microstructure, chemical composition, overlay thickness measurements, micro-hardness) of field-exposed samples indicate that these overlay materials are also attractive options as protective overlays for water wall tubes in low-NOx boilers. Data and field observations will be compared for INCONEL filler metals 72, 72M, 625 and 622.

9-12%Cr martensitic-ferritic steels continue to be developed for target temperatures of 650°C. This paper reviews the performance of two experimental European steels against the performance of the better known grade 92 alloy. It comments on the problem of type IV cracking and the effect of welding variables on cross-weld creep performance. Preliminary results from an on-going creep test programme are presented in context, and the findings compared with published data.

To operate future fusion power plants economically, the fusion community needs structural materials that can last longer and operate at higher temperatures than current materials, as well as better heat-dissipating components and a reliable supply chain for them. Additive manufacturing (AM) of existing reduced activation ferritic/martensitic steels (RAFMS) has the potential to solve these problems, which is why we developed a laser powder bed fusion (LPBF) process for Eurofer97 steel, demonstrating excellent mechanical properties (~30% improved yield strength, ~6300% improved creep rupture life, similar toughness and ductility compared to wrought Eurofer97) and low process scatter (relative standard error for yield, tensile strength and elongation on build plate <1%). The main remaining challenge is the consistent sourcing of quality Eurofer97 powder, but we have shown that this can already be done if the limits on impurity elements are slightly relaxed. Our work lays the groundwork for the manufacture of complex fusion components that can dissipate heat better and have a higher operating temperature thanks to the improved material properties. It also helps plug the current RAFMS supply chain gap, enabling easier component prototyping and small-scale manufacture that can smoothly scale in volume in the future.