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Huysmans S.,Engie Laboratory Laborelec | Vekeman J.,Belgian Welding Institute | Hautfenne C.,Engie Laboratory Laborelec
Welding in the World | Year: 2017

Modern and future power plants will use more complex materials to withstand the higher steam temperatures and pressures as well as thermal cycling. As such, dissimilar metal welds (DMWs) will be more widespread in new design than before and will need to demonstrate resistance to combinations of severe creep, corrosion/oxidation, and low cycle fatigue. The DMWs between different steels or alloys are an underestimated topic. Experienced and documented premature failures reveal the criticality of DMWs. This study focused on the DMWs between 9Cr martensitic creep strength enhanced ferritic steels and advanced austenitic stainless steels. Two collaborative projects related to 18%Cr and 25%Cr austenitic creep resisting stainless steel delivered data concerning base metal characterization and weldability of similar and dissimilar welding. The specific features of dissimilar welding are further approached in more detail in this analysis. Two main methodologies, i.e., direct welding and buttering techniques using different filler metals were investigated and characterized via uniaxial creep rupture testing and metallographic examination particularly focusing on the fusion line carbide formation and morphology. For the limited exposure times of 10 kh in this project, the results show that aligned and coarse type I carbide formation is occurring at the 9Cr fusion line between A617 type weld metal. The selection of P87 or A82 type filler metals demonstrated isolated to partly aligned carbides, respectively, at the fusion line. To mitigate the risk to corrosion and achieve a marginal increase in creep performance, buttering techniques are recommended. © 2016, International Institute of Welding.


Verleysen P.,Ghent University | Peirs J.,Ghent University | Van Slycken J.,Ghent University | Faes K.,Belgian Welding Institute | Duchene L.,University of Liège
Journal of Materials Processing Technology | Year: 2011

The strain rate dependence of plastic yield and failure properties displayed by most metals affects energies, forces and forming limits involved in high speed forming processes. This paper investigates the influence of the strain rate on the forming properties of one laboratory made and three commercial steel grades: a CMnAl TRIP steel, the ferritic structural steel S235JR, the drawing steel DC04 and the ferritic stainless steel AISI 409. First, split Hopkinson tensile bar (SHTB) experiments are carried out to assess the influence of the strain rate on the materials' stress-strain curves. Subsequently, the obtained SHTB results, together with static tensile test results, are used to model the constitutive behaviour of the investigated steels using the phenomenological Johnson-Cook (JC) model and the Voce model, thus allowing dynamic modelling of forming processes. Finally, forming limit diagrams (FLDs) are calculated using the Marciniak-Kuczynski method. The results clearly show that the effect of the strain rate on forces and energies involved in a forming process, and the forming limits is non-negligible and strongly material dependent. © 2011 Elsevier B.V. All rights reserved.


Taban E.,Kocaeli University | Taban E.,Belgian Welding Institute | Dhooge A.,Ghent University | Kaluc E.,Kocaeli University | Deleu E.,Belgian Welding Institute
Welding Journal | Year: 2012

In this study, modified 12% Cr stainless steel with very low carbon level (0.01%) to improve the weldability and mechanical properties, still conforming to EN 1.4003 and UNS S41003 grades, was joined by gas metal arc welding. Plates 12 mm thick were welded with ER309LSi, ER308LSi, and ER316LSi austenitic stainless steel consumables. Several samples extracted from the joints were subjected to mechanical testing by means of tensile, bend, and Charpy impact toughness tests, while tensile fractographs were examined. Toughness after the postweld heat treatment (PWHT) for 30 min at 720° and 750°C was also examined. Microstructural examinations, including macro- and micrographs, grain size analysis, hardness, and ferrite measurements, were conducted. Salt spray and blister tests for corrosion testing were applied. Considering all data obtained, good strength and satisfactory ductility results were determined, while mi-crostructure-property relationship was explained. It can be recommended to use 309 and 316 welding wires for better corrosion resistance compared to 308 welding wires. More encouraging impact toughness properties related with finer grained microstructure were also obtained for the welds produced by 309 and 316 wires. Postweld heat treatment of the GMA weld with ER308LSi showed good improvement for toughness due to the tempering of the martensite at the coarse-grained heat-affected zone. Increasing heat treatment temperature from 720° to 750°C made additional improvements in toughness.


Faes K.,Belgian Welding Institute | Zaitov O.,Belgian Welding Institute | De Waele W.,Ghent University
ASM Proceedings of the International Conference: Trends in Welding Research | Year: 2013

In magnetic pulse welding, electromagnetic forces are used to deform, accelerate and weld workpieces. The process is mostly used for tubular specimens. In this study, experiments were performed to investigate the weldability of various material combinations. The weld quality was assessed based on metallographic examinations, scanning electron microscopy and hardness measurements. The weld interface morphology, the intermetallic phases and the most common weld defects are described. Copyright © 2013 ASM International® All rights reserved.


Wim D.W.,Ghent University | Koen F.,Ghent University | Wim V.H.,Belgian Welding Institute
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2012

Electromagnetic punching of tubular products is considered to be a promising innovative perforating process. The required punching energy decreases when using high velocities. Also, less tools are required when compared to conventional mechanical punching. However, the increase in punching speed can involve new strain and fracture mechanisms which are characteristic of the dynamic loading. In high energy rate forming processes the effect of temperature versus time gradient on the material properties becomes important due to the heat accumulated from plastic deformation and friction. The deformation induced heating will promote strain localization in it, possibly degrade its formability and cause premature failure in the regions of high localized strain. The feasibility of the electromagnetic pulse forming process for punching holes in aluminum cylindrical specimens has been investigated on an experimental trial-and-error basis. Experiments were performed using a Pulsar system (model 50/25) with a maximum charging energy of 50 kJ and a discharge circuit frequency of 14 kHz. Microscopic and metallographic inspection of the punched workpieces, together with hardness measurements, was performed to critically evaluate the quality of the cuts. It was observed that damage occurred at part of the edge of the punched hole during some of the perforation experiments. It was evidenced that in most workpieces, especially those performed at higher charging energy levels, a considerably high temperature must have been reached in the regions near the punched hole. The aluminum in this region was assumed to have melted and resolidified. These assumptions were affirmed by the following observations. Microscopic-size precipitates present in the unaffected base metal microstructure, had completely dissolved in that region; shrinkage cavities and dendrite rich regions were clearly visible. Next to this region, a heat affected zone was present where the grain boundaries had partially melted and precipitates partially disappeared. Considerably high temperatures, in the order of 520 to 660 7deg;C, were reached in the regions around the punched holes, leading to melting and resolidification of the material. The total width of the thermally affected regions appeared to be larger at higher energy levels. The combination of heat generated by ohmic heating and by plastic deformation in a very short time interval is the most probable cause of the high peak temperatures that have occurred during the electromagnetic punching process. © 2012 American Society of Mechanical Engineers.


Zaitov O.,Belgian Welding Institute | Kolchuzhin V.A.,TU Chemnitz
Journal of Manufacturing Processes | Year: 2014

Electromagnetic pulse metal processing techniques (EPMPT) such as welding, forming and cutting have proven to be an effective solution to specific manufacturing problems. A high pulse magnetic field coil is a critical part of these technologies and its design is a challenging task. This paper describes a Bitter coil design using a newly developed methodology for a simplified analytical calculation of the coil and complementary finite element models (FE) of different complexity. Based on the methodology a Belgian Welding Institute (BWI) Bitter coil has been designed and tested by means of short circuit experiments, impedance and B-field measurements. A good agreement between the calculated and the experimental design parameters was found. © 2014 The Society of Manufacturing Engineers.


Vekeman J.,Belgian Welding Institute | Huysmans S.,GDF SUEZ | Hautfenne C.,GDF SUEZ
Welding in the World | Year: 2016

The modern Ultra Super Critical Power Plants (USC PP) applying the 600 °C technology require advanced stainless steels in superheater/reheater systems in order to cope with the increased steam parameters. Different grades of stainless steels have been developed by increasing Cr-contents, alloying with stabilizing and precipitating elements as well as thermomechanical heat treatments resulting in high creep rupture strengths and improved oxidation/corrosion resistance. In the context of a collaborative research project, X6CrNiNbN25-20 (DMV310N/HR3C) has been investigated. The main focus of the research project was on characterization and weldability assessment. As a result, the base metal under investigation was compared with governing code cases and specifications. Base metal chemical composition, microstructures, mechanical properties, reheat cracking sensitivity, and hot ductility as well as creep rupture strengths have been investigated. A weldability assessment, including thermal simulation and welding procedure qualifications, has been performed to establish parameter windows for similar and dissimilar welding. Dissimilar welding between grade 92 and austenitic steel tubes has been performed. The project also took the opportunity to investigate the behavior of a recently developed gas tungsten arc welding (GTAW) P87 consumable for dissimilar welding. Cross-weld creep rupture tests have been conducted for both similar and dissimilar welding, while aging tests addressed microstructural stability. © 2016, International Institute of Welding.


Vekeman J.,Belgian Welding Institute | Huysmans S.,GDF SUEZ | De Bruycker E.,GDF SUEZ
Welding in the World | Year: 2014

The modern (USC PP) applying the 600 °C technology require advanced austenitic stainless steels in superheater/reheater systems in order to cope with the increased steam parameters. Different grades of austenitic stainless steels have been developed by increasing Cr contents, alloying with stabilizing and precipitating elements as well as thermomechanical heat treatments resulting in high creep rupture strengths and improved oxidation/corrosion resistance. In the context of a collaborative research project, DMV304HCu (X10CrNiCuNb18-9-3) has been selected. The main focus of the research project was on characterization and weldability assessment. As a result, the base metal under investigation was compared with governing code cases and specifications. Base metal chemical composition, microstructures, mechanical properties, reheat cracking sensitivity, hot ductility as well as creep rupture strengths have been investigated. A weldability assessment, including thermal simulation and welding procedure qualifications, has been performed to establish parameter windows for similar and dissimilar welding. Dissimilar welding between Grade 92 and austenitic stainless steel tubes has been performed. The project also took the opportunity to investigate the behavior of a recently developed gas tungsten arc welding (GTAW) P87 consumable for dissimilar welding. Cross-weld creep rupture testing has been conducted for both similar and dissimilar welding, and aging tests addressed microstructural stability. © 2014, International Institute of Welding.


Deplus K.,Catholic University of Louvain | Simar A.,Catholic University of Louvain | Haver W.V.,Belgian Welding Institute | Meester B.D.,Catholic University of Louvain
International Journal of Advanced Manufacturing Technology | Year: 2011

Residual stresses are detrimental to the fatigue, fracture and corrosion resistance of welds. The literature on residual stress measurements in aluminium alloy friction stir welds is reviewed. The results of a large number of longitudinal residual stress measurements performed by the slitting method on friction stir welds in 2024-T3, 6082-T6 and 5754-H111 aluminium alloys are compared and their origin discussed. From the current investigation, it can be derived that the type of machine used for welding has only little influence on the residual stress profile. The influence of alloy type and welding parameters on the magnitude of the residual stresses and the shape of their distribution across the weld is investigated. Their magnitude is far below the room temperature yield strength of the base material. A distribution with an "M-shape" is always found on age hardenable structural alloys (albeit more pronounced in 6082-T6 alloy than in 2024-T3 alloy), while a "plateau" is found in the case of the strain hardenable 5754 H111 alloy. The low magnitude and the differences in distribution of the longitudinal residual stress are attributed mainly to the microstructural changes in the weld centre and are discussed based on the hardness profiles performed across the welds. The paper also discusses the reasons why those results are in disagreement with a number of numerical simulations from the literature that do not account for the influence of the welding thermomechanical history on the material microstructure and properties. © 2011 Springer-Verlag London Limited.


Kwee I.,Belgian Welding Institute | Faes K.,Belgian Welding Institute
Key Engineering Materials | Year: 2016

This study investigated joining of Al to Cu sheets by electromagnetic pulse welding, which is a solid-state welding process that uses electromagnetic forces to join materials. The interfacial morphology and mechanical properties of the Al/Cu joints were analysed and related to the welding process parameters and weld properties. The centre section of the Al/Cu joints evolved from a non-welded to a welded zone. The welded zone started with a wavy interface, consisting of thick interfacial layers with defects and evolved to a relatively flat interface without an interfacial layer. The interfacial layer thickness is determined by both the discharge energy and the stand-off distance. A higher tensile force, up to 4.9 kN, was achieved at a higher energy and a lower stand-off distance of 2 mm. The tensile force is directly related to the weld width, since a higher tensile force is achieved for a higher weld width. In addition, the presence of interfacial layers can contribute to a small extent to a higher tensile force. © 2016 Trans Tech Publications, Switzerland.

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