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  • 1.
    Ariaseta, Achmad
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Department of Metallurgical Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Bandung (IDN).
    Sadeghinia, Nima
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    Department of Mechanical Engineering, University of Manitoba, Winnipeg (CAN).
    Keyhole TIG welding of newly developed nickel-based superalloy VDM Alloy 7802023Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 67, nr 1, s. 209-222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of keyhole TIG (K-TIG) welding parameters on the weld geometry and defects of a new nickel-based superalloy VDM Alloy 780 alloy were investigated using a statistical design of experiment, and the microstructures of the heat-affected zone (HAZ) and fusion zone (FZ) of the K-TIG-welded VDM Alloy 780 were characterized. No cracks are found in the FZ and HAZ. Travel speed significantly influences the minimum weld width (Wm), face and root excess weld metal, face underfill, and average pore diameter. Welding current and the interaction current*travel speed significantly influence the face and root excess weld metals, respectively. Interdendritic microconstituents in the FZ are identified as (Nb,Ti)C particles and γ/Laves eutectic constituents based on SEM–EDS analysis. In addition, plate-like precipitates likely to be δ/η phase are observed surrounding the interdendritic Laves eutectics, and γ′ precipitates are found to be inhomogeneously precipitated in the FZ. In the partially melted zone (PMZ), (Nb,Ti)C, Laves phase, and plate-like particles are found in the liquated and resolidified regions. Constitutional liquation of (Nb,Ti)C in HAZ is observed where the liquated (Nb,Ti)C appears to be associated with the γ/Laves eutectic as a resolidified product. 

    Fulltekst (pdf)
    fulltext
  • 2.
    Aydin, Gökçe
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, Maria Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Şelte, Aydın
    Uddeholms AB, Hagfors (SWE).
    Oikonomou, Christos
    Uddeholms AB, Hagfors (SWE).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of laser metal deposition process parameters on a precipitation hardening stainless steel2023Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 67, nr 4, s. 1067-1080Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The combination of corrosion resistance and mechanical properties of martensitic precipitation hardening stainless steels (MPHSS) makes them well suited for demanding applications in aerospace, high-pressure gas bottles, or in injection molding of corrosive plastics. Directed energy deposition methods and specifically the laser metal deposition process with powder as feedstock (LMDp) have the potential to be applied in the production of such components. It is well-known that the geometrical features of the deposited beads such as aspect ratio and dilution are crucial for process efficiency and deposition quality. Therefore, this work aims at understanding the influence of the process parameters and the resulting microstructure of a MPHSS modified PH 13-8Mo alloy when using LMDp. Design of experiment (DoE) was used to plan and analyze the influence and interaction of the different LMDp process variables in the geometry of the deposits. It was found that height, width, and depth were statistically significantly influenced by speed, while height was also considerably influenced by the powder feeding rate. In terms of laser power, it was the most significant factor for the width and the depth, but it did not significantly affect the height of the beads. The results showed that the as-deposited microstructure of the modified PH 13-8Mo under the LMDp conditions investigated in this work consists of a martensitic matrix with some amount of primary δ ferrite. The presence of a low amount of retained austenite and aluminum-enriched inclusions was confirmed. This work enhances the fundamental process and material understanding of LMDp of the modified PH 13-8Mo alloy as a first stage in the fabrication of additively manufactured components.

    Fulltekst (pdf)
    Tidskriftens fulltext
  • 3.
    Baghdadchi, Amir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hosseini, Vahid
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Promoting austenite formation in laser welding of duplex stainless steel-impact of shielding gas and laser reheating2021Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, s. 499-511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Avoiding low austenite fractions and nitride formation are major challenges in laser welding of duplex stainless steels (DSS). The present research aims at investigating efficient means of promoting austenite formation during autogenous laser welding of DSS without sacrificing productivity. In this study, effects of shielding gas and laser reheating were investigated in welding of 1.5-mm-thick FDX 27 (UNS S82031) DSS. Four conditions were investigated: Ar-shielded welding, N2-shielded welding, Ar-shielded welding followed by Ar-shielded laser reheating, and N2-shielded welding followed by N2-shielded laser reheating. Optical microscopy, thermodynamic calculations, and Gleeble heat treatment were performed to study the evolution of microstructure and chemical composition. The austenite fraction was 22% for Ar-shielded and 39% for N2-shielded as-welded conditions. Interestingly, laser reheating did not significantly affect the austenite fraction for Ar shielding, while the austenite fraction increased to 57% for N2-shielding. The amount of nitrides was lower in N2-shielded samples compared to in Ar-shielded samples. The same trends were also observed in the heat-affected zone. The nitrogen content of weld metals, evaluated from calculated equilibrium phase diagrams and austenite fractions after Gleeble equilibrating heat treatments at 1100 °C, was 0.16% for N2-shielded and 0.11% for Ar-shielded welds, confirming the importance of nitrogen for promoting the austenite formation during welding and especially reheating. Finally, it is recommended that combining welding with pure nitrogen as shielding gas and a laser reheating pass can significantly improve austenite formation and reduce nitride formation in DSS laser welds. © 2020, The Author(s).

    Fulltekst (pdf)
    fulltext
  • 4.
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Gas tungsten arc models including the physics of the cathode layer: remaining issues2018Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 62, nr 1, s. 177-196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A recent review pointed out that the existing models for gas tungsten arc coupling the electrode (a cathode) and the plasma are not yet complete enough. Their strength is to predict with good accuracy either the electric potential or the temperature field in the region delimited by the electrode and the workpiece. Their weakness is their poor ability to predict with good accuracy these two fields at once. However, both of these fields are important since they govern the heat flux to the workpiece through current density and temperature gradient. New developments have been made since then. They mainly concern the approaches addressing the electrode sheath (or space charge layer) that suffered from an underestimation of the arc temperature. These new developments are summarized and discussed, the modelling assumptions are examined, and important modelling issues that remain unexplored are underlined.

  • 5.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Lindgren, Lars -Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part I: A pore-based crack criterion2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 5, s. 1489-1502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair and, if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 6.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Lindgren, Lars -Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part II: A model for estimation of grain boundary liquid pressure in a columnar dendritic microstructure2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 5, s. 1503-1519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model for computing the pressure and the thickness of the grain boundary liquid film, which are required to evaluate the crack criterion in paper 1. The third and final paper describes the application of the model to Varestraint tests of Alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 7.
    Draxler, Joar
    et al.
    Luleå University of Technology, Luleå, 97187, Sweden.
    Edberg, Jonas
    Luleå University of Technology, Luleå, 97187, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Lindgren, Lars-Erik
    Luleå University of Technology, Luleå, 97187, Sweden.
    Modeling and simulation of weld solidification cracking part III: Simulation of solidification cracking in Varestraint tests of alloy 7182019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 6, s. 1883-1901Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several advanced alloy systems are susceptible to weld solidification cracking. One example is nickel-based superalloys, which are commonly used in critical applications such as aerospace engines and nuclear power plants. Weld solidification cracking is often expensive to repair, and if not repaired, can lead to catastrophic failure. This study, presented in three papers, presents an approach for simulating weld solidification cracking applicable to large-scale components. The results from finite element simulation of welding are post-processed and combined with models of metallurgy, as well as the behavior of the liquid film between the grain boundaries, in order to estimate the risk of crack initiation. The first paper in this study describes the crack criterion for crack initiation in a grain boundary liquid film. The second paper describes the model required to compute the pressure and thickness of the liquid film required in the crack criterion. The third and final paper describes the application of the model to Varestraint tests of alloy 718. The derived model can fairly well predict crack locations, crack orientations, and crack widths for the Varestraint tests. The importance of liquid permeability and strain localization for the predicted crack susceptibility in Varestraint tests is shown. © 2019, The Author(s).

  • 8.
    Draxler, Joar
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Åkerström, P.
    Lulea University of Technology, 97187 Luleå, Sweden.
    Edberg, J.
    Lulea University of Technology, 97187 Luleå, Sweden.
    Lindgren, L. -E
    Lulea University of Technology, 97187 Luleå, Sweden.
    Singh, S.
    Chalmers University of Technology, 41296 Goteborg, Sweden .
    Raza, Tahira
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    A numerical model for simulating the effect of strain rate on eutectic band thickness2020Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 64, s. 1635-1658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large tensile strains acting on the solidifying weld metal can cause the formation of eutectic bands along grain boundaries. These eutectic bands can lead to severe liquation in the partially melted zone of a subsequent overlapping weld. This can increase the risk of heat-affected zone liquation cracking. In this paper, we present a solidification model for modeling eutectic bands. The model is based on solute convection in grain boundary liquid films induced by tensile strains. The proposed model was used to study the influence of strain rate on the thickness of eutectic bands in Alloy 718. It was found that when the magnitude of the strain rate is 10 times larger than that of the solidification rate, the calculated eutectic band thickness is about 200 to 500% larger (depending on the solidification rate) as compared to when the strain rate is zero. In the paper, we also discuss how eutectic bands may form from hot cracks. © 2020, The Author(s).

  • 9.
    Ferreira, Rafael Pereira
    et al.
    Federal Institute of Education, Science and Technology of Maranhão (IFMA), Campus Barra do Corda, Barra do Corda (BRA); Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Vilarinho, Louriel Oliviera
    Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Center for Research and Development of Welding Processes (Laprosolda), Federal University of Uberlândia (UFU), Uberlândia (BRA).
    Development and implementation of a software for wire arc additive manufacturing preprocessing planning: trajectory planning and machine code generation2022Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To overcome a shortage of flexible and low-cost solutions for wire arc additive manufacturing (WAAM) preprocessing, this work´s objective was to develop and validate an in-house computational programme in an open-source environment for WAAM preprocessing planning. Algorithms for reading STL (stereolithography) files and implementing rotation, slicing, trajectory planning, and machine code generation were elaborated and implemented in the Scilab environment (free and open-source). A graphical interface was developed to facilitate user interaction, with 5 options for path planning. The functionality of each work step is detailed. For validation of the software, single and multiple-layer prints, with different geometrical complexity and printing challenges, were built in a CNC table geared by the generated machine code. The validation criteria were deposition imperfection, morphological, and dimensional tolerances. The outputs showed that the parts were successfully printed. Therefore, this work demonstrates that Scilab provides the necessary resources for companies and universities to implement and/or develop algorithms for planning and generating trajectories for WAAM. Moreover, emerging ideas can be reasonably easily implemented in such software, not always possible in commercial packages. 

    Fulltekst (pdf)
    Springer
  • 10.
    Hanning, Fabian
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Weldability of wrought Haynes 282 repair welded using manual gas tungsten arc welding2018Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 62, nr 1, s. 39-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of the precipitation hardening superalloy Haynes® 282® to be repaired by multi-pass gas tungsten arc welding is investigated in this study. The repair welding has been carried out on forged discs having four pre weld heat treatments, resulting in different grain sizes and precipitate structures of the base material. Another set of discs has additionally been put through a post weld heat treatment. The tendency to form cracks in the heat-affected zone and the fusion zone has been investigated metallographically. No cracks in the base metal heat-affected zone were found,whereas solidification cracks were present in the weld fusion zone of all tested conditions. While high heat input during welding increased cracking by a factor of 1.5, none of the heat treatments had a measurable influence on the cracking behaviour. Voids with solid state crack-like appearance turned out tobe aluminium-rich oxides being present from the deposition of previous weld deposit layers.

  • 11.
    Hanning, Fabian
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Khan, Abdul Khaliq
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada (CAN); Manitoba Institute for Materials, University of Manitoba, Winnipeg, Canada (CAN).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olamrewaju
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada (CAN).
    Advanced microstructural characterisation of cast ATI 718 Plus-effect of homogenisation heat treatments on secondary phases and repair welding behaviour2020Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 64, nr 3, s. 523-533Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of base metal conditions on the weld cracking behaviour of cast ATI 718Plus® is investigated by comparing 4 h and 24 h dwell time pseudo-hip homogenisation heat treatments at 1120, 1160 and 1190 °C with the as-cast microstructure. Scanning electron microscopy (SEM), X-ray diffraction (XRD) on electrolytically extracted powder and transmission electron microscopy (TEM) were used to identify Nb-rich secondary phases in interdendritic areas as the C14 Laves phase and Nb(Ti) MC-type carbides. All homogenisation heat treatments but the 1120 °C 4-h condition dissolve the Laves phase. A repair welding operation was simulated by linear groove multi-pass manual gas tungsten arc welding (GTAW). The Laves phase containing microstructures resulted in lower total crack length for heat affected zone cracking. Constitutional liquation of Nb(Ti) MC-type carbides is observed as a liquation mechanism in Laves-free microstructure, while thick liquid film formation due to the Laves eutectic melting could reduce the formation of weld cracks in microstructures containing the Laves phase.

    Fulltekst (pdf)
    fulltext
  • 12.
    Harati, Ebrahim
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). ITW Welding AB, Järntrådsvägen 2, Partille, SE-433 30, Sweden.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Comparison of effect of shot-peening with HFMI treatment or use of LTT consumables on fatigue strength of 1300 MPa yield strength steel weldments2020Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 64, nr 7, s. 1237-1244Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, T-joint samples in a 1300 MPa yield strength steel were produced using conventional or low transformation temperature (LTT) type consumables. The welded samples were either subjected to high-frequency mechanical impact (HFMI) treatment or to shot-peening. Fatigue testing was performed under fully reversed, constant amplitude bending load. Shot-peening gave a significant increase in fatigue strength for more than around 50,000 cycles. Shot-peened LTT welds had the highest fatigue strength, with conventional welds being shot-peened having slightly lower fatigue strength. HFMI treatment of conventional and LTT welds improved the fatigue strength also, but to a lesser extent, keeping the slope in the SN diagram close to three, while shot-peened samples had a slope of 5–7. Significant differences in compressive residual stress were seen between the different welds, with the most compressive stress found in the shot-peened samples. This was probably one of the main reasons for the improved fatigue life of shot-peened samples. © 2020, The Author(s).

  • 13.
    Hosseini, Vahid A.
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser. Innovatum AB, Trollhättan, Sweden.
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Gårdstam, Johannes
    Swerea KIMAB AB, Kista, Sweden.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Influence of multiple thermal cycles on microstructure of heat-affected zone in TIG-welded super duplex stainless steel2016Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, nr 2, s. 233-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of heat input and multiple welding cycles on the microstructure of the heat-affected zone in autogenously TIG-welded 6 mm 2507 type super duplex stainless steel plates was investigated. In order to produce multiple thermal cycles, one to four pass bead-on-plate welds were made with arc energies of 0.47 and 1.08 kJ/mm, corresponding to heat inputs of 0.37 and 0.87 kJ/mm. Several thermocouples were attached to record thermal cycles on the front and back sides of the plates. Finite element modelling was successfully done to map and correlate measured and calculated peak temperatures. Only minor changes were seen in the ferrite content at 1 and 2 mm from the fusion boundary. Nitrides formed in all passes of the low heat input samples in a region next to the fusion boundary, but only after the third and fourth passes of the high heat input samples. Sigma phase precipitated only in a zone heated to a peak temperature in the range of approximately 828 to 1028 °C. Multiple reheating was found to promote precipitation of sigma phase relatively more than slower cooling. A precipitation free zone was observed between the nitride and sigma phase bands. The precipitation behaviour could be understood from equilibrium phase diagrams, evaluation of local thermal cycles and by correlating results from the modelling and measurements of peak temperatures. It is suggested that the peak temperature, the accumulated time in the critical temperature range between approximately 828 and 1028 °C, and the number of thermal cycles are the most relevant criteria when evaluating the risk of sigma phase formation.

  • 14.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Innovatum AB, Sharif University of Technology, Tohoku University, Chalmers University of Technology.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Eyzop, Daniel
    Outokumpu Stainless AB, Avesta Research Centre, Avesta, Sweden.
    Östberg, Agneta
    Sandvik Materials Technology, Sandviken, Sweden.
    Janiak, Paul
    Swerea KIMAB AB, Kista, Sweden.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ferrite content measurement in super duplex stainless steel welds2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 2, s. 551-563Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Approaches to determining ferrite fraction (%) and ferrite number (FN) were examined for super duplex stainless steel (SDSS) welds. A reference sample was produced by bead-on-plate gas–tungsten arc welding of a type-2507 SDSS plate. By comparing different etchants and measurement practices, it was realized that etching with modified Beraha followed by computerized image analysis (IA) was the most accurate and quickest technique to measure ferrite fraction, which determined the same ferrite fraction (68.0 ± 2.6%) as that measured by electron diffraction backscattered analysis (67.6 ± 2.3%). A Round Robin test was performed on a reference sample at University West, Swerea KIMAB, Outokumpu Stainless, and Sandvik Materials Technology to investigate the repeatability of the technique. The ferrite fraction measurements performed at different laboratories showed very small variations, which were in the range of those seen when changing microscope in the same laboratory. After verification of the technique, the relationship between ferrite fraction and ferrite number (measured with FERITSCOPE®) was determined using 14 single (root) pass welds, including butt, corner, and T-, V-, and double V-joint geometries. The best-fit equation found in this study was ferrite number (FN) = 1.1 × ferrite fraction (%). To conclude, the ferrite fraction technique suggested in the present paper was accurate and repeatable, which made it possible to determine a ferrite fraction–ferrite number formula for SDSS single-pass welds.

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    fulltext
  • 15.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Bead by bead study of a multipass shielded metal arc-welded super-duplex stainless steel2020Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 64, nr 2, s. 283-299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study aims at investigating bead geometry and the evolution of microstructure with thermal cycles in multipass shielded metal arc welding of a V-groove 13-mm type-2507 super-duplex stainless steel (SDSS) plate. The weld consisted of 4 beads produced with arc energies of 0.81-1.06 kJ/mm. The upper beads showed lower base metal (BM) dilution than the first bead. Thermal cycles were recorded with thermocouples, indicating that the cooling rate decreased in the as-deposited weld zone when adding a new bead. Ferrite fraction in the as-welded condition was lower for the upper beads. The austenite grain morphology in reheated passes varied depending on the local peak temperatures and the number of reheating passes. Sigma phase precipitated in a location reheated by the third and fourth passes that was subjected to a critical peak temperature for sigma precipitation. Ferrite content, measured using image analysis and Fisher FERITSCOPE technique, showed that the ferrite fraction moved toward 50/50% in the weld metal with an increasing number of reheating cycles. Finally, a schematic map showing an overview of the microstructure in the multipass SDSS weld was introduced.

  • 16.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Högström, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Valiente Bermejo, María Asunción
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Stridh, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 4, s. 975-987Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evolution of microstructures with thermal cycles was studied for wire-arc additive manufacturing of duplex stainless steel blocks. To produce samples, arc energy of 0.5kJ/mm and interlayer temperature of 150 degrees C were used as low heat input-low interlayer temperature (LHLT) and arc energy of 0.8kJ/mm and interlayer temperature of 250 degrees C as high heat input-high interlayer temperature (HHHT). Thermal cycles were recorded with different thermocouples attached to the substrate as well as the built layers. The microstructure was analyzed using optical and scanning electron microscopy. The results showed that a similar geometry was produced with 14 layers4 beads in each layerfor LHLT and 15 layers3 beads in each layerfor HHHT. Although the number of reheating cycles was higher for LHLT, each layer was reheated for a shorter time at temperatures above 600 degrees C, compared with HHHT. A higher austenite fraction (+8%) was achieved for as-deposited LHLT beads, which experienced faster cooling between 1200 and 800 degrees C. The austenite fraction of the bulk of additively manufactured samples, reheated several times, was quite similar for LHLT and HHHT samples. A higher fraction of secondary phases was found in the HHHT sample due to longer reheating at a high temperature. In conclusion, an acceptable austenite fraction with a low fraction of secondary phases was obtained in the bulk of wire-arc additively manufactured duplex stainless steel samples (35-60%), where higher austenite fractions formed with a larger number of reheating cycles as well as longer reheating at high peak temperatures (800-1200 degrees C).

    Fulltekst (pdf)
    fulltext
  • 17.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Innovatum AB., Trollhättan, Trollhättan, Sweden.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Engelberg, D.
    University of Manchester, School of Materials, M13 9PL, Manchester, United Kingdom.
    Wessman, Sten
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Correction to: Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals (Welding in the World, (2018), 62, 3, (517-533), 10.1007/s40194-018-0548-z)2018Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 62, nr 4, s. 893-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unfortunately due to typesetting mistakes, Tables 4-€“6 have been displayed erroneously in the article. © 2018, International Institute of Welding.

  • 18.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Innovatum AB.,Trollhättan, Trollhättan, Sweden.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Engelberg, Dirk
    The University of Manchester, School of Materials,Manchester,UK.
    Wessman, Sten
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Time-temperature-precipitation and property diagrams for super duplex stainless steel weld metals2018Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 62, nr 3, s. 517-533Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Super duplex stainless steel (SDSS) weld metal microstructures, covering the complete temperature range from ambient to liquidus, were produced by arc heat treatment for 1 and 10 min. Temperature modeling and thermodynamic calculations complemented microstructural studies, hardness mapping and sensitization testing. After 1 min, intermetallics such as sigma and chi phase had precipitated, resulting in moderate sensitization at 720–840 °C. After 10 min, larger amounts of intermetallics resulted in hardness up to 400 HV0.5 and more severe sensitization at 580–920 °C. Coarse and fine secondary austenite precipitated at high and low temperatures, respectively: The finer secondary austenite was more detrimental to corrosion resistance due to its lower content of Cr, Mo, and N as predicted by thermodynamic calculations. Increased hardness and etching response suggest that 475 °C embrittlement had occurred after 10 min. Results are summarized as time-temperature-precipitation and property diagrams for hardness and sensitization.

    Fulltekst (pdf)
    fulltext
  • 19.
    Javidi Shirvan, Alireza
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Choquet, Isabelle
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
    A review of cathode-arc coupling modeling in GTAW2016Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, nr 4, s. 821-835Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Material properties of welds are strongly influenced by the thermal history, including the thermo-fluid and electromagnetic phenomena in the weld pool and the arc heat source. A necessary condition for arc heat source models to be predictive is to include the plasma column, the cathode, and the cathode layer providing their thermal and electric coupling. Different cathode layer models based on significantly different physical assumptions are being used. This paper summarizes today’s state of the art of cathode layer modeling of refractory cathodes used in GTAW at atmospheric pressure. The fundamentals of the cathode layer and its physics are addressed. The main modeling approaches, namely (i) the diffusion approach, (ii) the partial LTE approach, and (iii) the hydrodynamic approach are discussed and compared. The most relevant publications are systematically categorized with regard to the respective physical phenomena addressed. Results and process understanding gained with these models are summarized. Finally, some open questions are underlined.

  • 20.
    Johansson, Mikael
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Stenvall, Peter
    Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Evaluation of test results and ranking criteria for Varestraint testing of an austenitic high-temperature alloy2020Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 64, s. 903-912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Varestraint testing is commonly used to evaluate hot cracking susceptibility of materials. In this paper, the dependence of operators and evaluation technique on test results is studied for a high-temperature austenitic stainless steel (UNS S31035). Samples were tested at six different strain levels ranging from 0.7 to 3.8%. Four different operators evaluated the same samples following the same instructions on how to measure the cracks manually in an optical microscope at x 25 magnification. The largest variation among operators evaluation was found for low strain levels where small and few cracks were found. In addition, one of the four operators used image analysis to evaluate the samples at x 50 magnification. The average total crack length and total number of cracks in fusion zone and heat-affected zone were approximately 1.5 times higher when using image analysis compared with manual evaluation. Image analysis at x 50 made it possible to detect smaller cracks compared with manual evaluation at x 25 magnification, contributing to an increased number of cracks detected. The maximum crack length using image analysis at x 50 was similar to manual evaluation made at x 25 magnification and was the criterion that showed the least variation in this study. However, further comparisons using other magnifications are needed to verify the agreement between manual evaluation and image analysis found in this study. An advantage with evaluation using image analysis is that it provides traceable results. A harmonized standard for Varestraint testing, and especially for evaluation, would decrease the variation among operators and laboratories.

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    fulltext
  • 21.
    Jorge, Vinicius Lemes
    et al.
    University of Uberlandia, Center for Research and Development of Welding Processes of the Federal, Uberlandia, Brazil.
    Gohrs, Raul
    IMC Soldagem, Palhoça, Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Active power measurement in arc welding and its role in heat transfer to the plate2017Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 61, nr 4, s. 847-856Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A contemporary paper claimed that a method using the resistance of impedance (active power) for arc power calculation is more accurate than the conventional approach, with consequences on the actual heat transfer to the plate. However, despite the comprehensive reasoning, no heat-related results are shown in this intriguing paper to support the claim. Thus, the aim of this work was to apply the proposed method for determining the weight of active power in the total arc power. A series of weldments was carried out, by using GTAW in constant and pulsed current modes and short-circuiting GMAW with different inductance settings. The effect of the active power on the heat transfers to the plate was assessed by both bead cross-section geometries and calorimetry. The results showed that even a significant fraction of active power of the total power was reached, no changes in bead geometry or heat input were found. A review of the assumptions used in the primal paper showed that an arc is better represented by an ER circuit than by an RLC circuit. As a conclusion, the arc as a reactance-free load presents no component such as non-active power and the conventional approaches are accurate methods to measure arc power, representing the actual active power. © 2017, The Author(s).

    Fulltekst (pdf)
    fulltext
  • 22.
    Li, Peigang
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Klement, Uta
    Department of Materials and manufacture, Chalmers University.
    Characterization of cold lap defects in tandem arc MAG welding2012Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 56, nr 9/10, s. 20-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01–1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely “spatter cold lap”, and “overlap cold lap” and “spatter-overlap cold lap”. No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 23.
    Lippold, John C.
    et al.
    Welding Engineering Program, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, (USA).
    Bollinghaus, Ing Thomas
    Department of Component Safety (Dpt.9), Bundesanstalt für Materialforschung und –prüfung, Berlin, (DEU).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Welding in the world-update 20212021Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, nr 2, s. 167-169Artikkel i tidsskrift (Annet vitenskapelig)
  • 24.
    Liskevych, Olga
    et al.
    Center for Research and Development of Welding Processes of Federal University of Uberlandia (Laprosolda), Brazil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Influence of the CO2 Content on Operational Performance of Short-Circuit GMAW2015Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, nr 2, s. 217-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CO2 blended with Ar is the most common shielding gas used for short-circuit GMAW. There has been some technical knowledge devised from the process application over the years (personal opinion and results from practice) on the selection of the gas blend composition. However, there is still lack of more scientific data to explain the performance of the mixtures. This paper presents a systematic study of the influence that CO2 content in mixture with Argon has on the operational performance of the short-circuit GMAW. The objective of this study was to describe, to quantify and to explain the alterations in the metal transfer behavior, spatter generation, weld bead geometry and bead finish due to the different CO2 contents in the shielding gas. Carbon steel plates were welded in adequate parametric conditions for each CO2+Ar shielding gas composition (CO2 ranging from 2% to 100%). These parametric conditions were found by applying a metal transfer regularity index over welds carried out at different voltage settings for each gas blend. A target of 130 A was applied as base for comparison. Laser shadowgraphy with high speed filming and current and voltage oscillograms were used as analysis tools. The results showed (and confirmed) that the increase of the CO2 content deteriorates metal transfer regularity, leading to excessive spatter generation and uneven bead appearance, but increases the penetration and the fusion area of the weld beads and improves bead convexity. In general, the CO2 content should neither be lower than 10% (unless for thin plates) nor higher than 30%.

  • 25.
    Mertinger, V
    et al.
    University of Miskolc, Miskolc (HUN).
    Varbai, B.
    Budapest University of Technology and Economics, Budapest (HUN).
    Adonyi, Yoni
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    DeBacker, J.
    TWI Ltd., Cambridge (GBR).
    Nagy, E.
    University of Miskolc, Miskolc (HUN).
    Lesko, M.
    University of Miskolc, Miskolc (HUN).
    Karpati, V
    University of Miskolc, Miskolc (HUN).
    Microstructure evaluation of dissimilar AA2024 and AA7050 aluminum joints made by corner stationary-shoulder friction stir welding2022Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fillet welds made by the corner stationary-shoulder friction stir welding process between AA7050-T7451 and AA2024-T4 sheets were characterized using different metallographic techniques and mechanical testing. Robotic welds of an aircraft’s skin-to-internal stiffeners were examined using Barker’s electrolytic and Keller’s etching techniques and correlated with electron backscattered diffraction results and energy-dispersive microprobe analysis. The composition and grain orientation maps and material flow lines demonstrated excellent weld quality in spite of the apparent inhomogeneities in the stir zone where mechanical mixing was complete. Welded joint efficiencies were in the 85-92% of the base metals and were acceptable in terms of resistance to crack initiation and propagation and corrosion resistance, even with softening of the heat-affected zones. It was concluded that several optical and electron microscopy techniques are needed to characterize these dissimilar aluminum welds fully and that post-weld mechanical and thermal treatments could even further improve their quality.

    Fulltekst (pdf)
    Springer
  • 26.
    Sikström, Fredrik
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Ericson Öberg, Anna
    Volvo Construction Equipment, Arvika, Sweden.
    Prediction of penetration in one-sided fillet welds by in-process joint gap monitoring: an experimental study2017Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 61, nr 3, s. 529-537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The challenge to predict variations in penetration depth in one-sided fillet welds during robotized gas metal arc welding has been addressed by a pilot investigation of technical possibilities and limitations. The main cause for the variation in penetration depth is considered to be variation in joint gap size. Special attention has been paid in order to adopt the experimental conditions to conform to industrial welding conditions. The employed method uses in-process monitoring of joint gap size together with an empirical model relating penetration depth to gap size in order to predict this depth. The gap size estimates are based on image information from two cameras, one visual and one infrared. The results, that are evaluated off-line, confirm the development of a real-time method providing technical solutions that are industrially tractable. The results also pinpoint areas of further improvements towards increased robustness and reduced estimation uncertainties.

    Fulltekst (pdf)
    fulltext
  • 27.
    Singh, Sukhdeep
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Varestraint weldability testing of cast ATI® 718Plus™: a comparison to cast Alloy 7182019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 2, s. 389-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Varestraint testing of the newly developed cast ATI® 718Plus™ after pseudo-HIP (hot isostatic pressing) heat treatments showed that the extent of solidification cracking was independent of the heat treatment condition. The susceptibility towards heat-affected zone (HAZ) liquation cracking was found to be related to the heat treatment dwell time rather than the temperature. The heat treatments at 1120 and 1190 °C for 24 h were the most susceptible to cracking. On the other hand, heat treatments at 1120, 1160 and 1190 °C for 4-h dwell time exhibited the least amount of cracking. The solidification cracking was found to be similar whereas the HAZ liquation cracking was lower for ATI® 718Plus™ after the heat treatment at 1120 and 1190 °C for 4-h dwell time in comparison to cast Alloy 718.

  • 28.
    Sreekanth, Suhas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Effect of process parameters and heat treatments on delta-phase precipitation in directed energy deposited alloy 7182022Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article outlines a detailed study of solution treatments and delta precipitation treatments carried out on laser-directed energy deposited (DED) alloy 718 specimens. Two different sets of DED process parameters were used in high and low energy conditions that yield different microstructural features to study the effect of process parameters on delta precipitation. These two conditions were subjected to solution treatment at 1010 °C and 1050 °C each for 1 h, which improved homogeneity and altered grain texture with introduction of annealing twins. The as-built and solution-treated specimens served as the initial reference condition for subsequent delta processing treatments (DPT) performed at three temperatures of 850 °C, 900 °C, and 950 °C to study the effect of short- and long-term exposures ranging from 1 to 48 h. When as-built specimens were subjected to DPT, interdendritic delta precipitates were observed at Nb-rich regions. In contrast, solution-treated specimens under short-term exposure to DPT resulted in intergranular delta phase precipitates whereas under long-term exposures to DPT yielded predominantly intragranular delta precipitates, which grew denser and longer with increased time of treatment. For longer exposure times of 24 and 48 h, a continuous film of intergranular delta phase was noticed. The morphology, location, and volume fraction of delta phase precipitates studied in this research are imperative for designing the performance of alloy 718 built by DED process.

    Fulltekst (pdf)
    fulltext
  • 29.
    Valiente Bermejo, María Asunción
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
    Rasmuson, H.
    ESAB AB, Göteborg, Sweden.
    Frodigh, M.
    Sandvik Materials Technology, Sandviken, Sweden.
    Bengtsson, P.
    AGA Gas AB, Lidingö, Sweden.
    Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds2015Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, nr 2, s. 239-249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of shielding gases on welding performanceand on properties of duplex and superduplex stainlesssteel welds was studied. Using argon as the reference gas,helium, nitrogen and carbon dioxide were added and fivemixtures evaluated. Bead-on-plate welds and circumferentialpipe welds were produced using mechanisedGMAwelding inthe downhand position. Welding performance, corrosion resistance,mechanical properties, microstructural features andweld imperfections were assessed and related to the shieldinggas. Shielding gases containing 30 % helium showed excellentresults; whilst pure argon showed unstable arc and poorweld pool fluidity and Ar+2 %CO2 resulted in underfill andporosity. Mixtures containing helium resulted in higher ductilitywelds and higher impact toughness values than weldsproduced with Ar+2 %CO2. Sound and balanced duplexmicrostructures free from intermetallics were found with suitableferrite contents for all the shielding gases studied. All theduplex pipe welds passed the corrosion test regardless of theshielding gas used, and the best results in the corrosion test forsuperduplex pipe welds were found when using Ar+30 %He+0.5 %CO2+1.8 %N2 as shielding gas.

  • 30.
    Valiente Bermejo, María Asunción
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för naturvetenskap, lantmäteri- och maskinteknik.
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser.
    Rasmuson, Helene
    ESAB AB, Göteborg, Sweden.
    Frodigh, Mette
    Sandvik Materials Technology, Sandviken, Sweden .
    Bengtsson, Per
    AGA Gas AB, Lidingö, Sweden.
    Effect of welding position on properties of duplex and superduplex stainless steel circumferential welds2015Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, nr 5, s. 693-703Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of welding position on properties ofduplex and superduplex stainless steel welds was studied. Circumferential pipe welds were produced using mechanised gasmetal arc welding in flat position, vertical up position and overhead position. Dilution, corrosion resistance, mechanical properties, microstructural features and weld imperfections were assessed and related to the welding position. Welds produced in flat and vertical up positions were less likely to produce porosity than those welded in overhead position, whilst underfill was not observed in overhead position welds. All the duplex pipe welds passed the corrosion test regardless of the welding position and showed sound microstructures. Under fixed arc energy conditions, welds produced in vertical up position showed the lowest dilution values whilst welds in flat position showed the highest. Excellent impact toughness values and cross tensile values were found regardless of the welding positions. Whenever possible, flat position is recommended as welds showed less proneness to porosity. Vertical up position is recommended as the second best choice.

  • 31.
    Valiente Bermejo, María Asunción
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Thalavai Pandian, Karthikeyan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Axelsson, Björn
    Alfa Laval Tumba AB, Tumba .
    Harati, Ebrahim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). ITW Welding AB, Partille .
    Kisielewicz, Agnieszka
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Microstructure of laser metal deposited duplex stainless steel: Influence of shielding gas and heat treatment2021Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 65, s. 525-541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This research work is the first step in evaluating the feasibility of producing industrial components by using Laser Metal Deposition with duplex stainless steel Wire (LMDw). The influence of Ar and N2 shielding gases was investigated in terms of nitrogen loss and in the microstructure and austenite content of different deposited geometries. The evolution of the microstructure in the build-up direction of the Ar and N2-shielded blocks was compared in the heat-treated and as-deposited conditions. The susceptibility for oxygen pick-up in the LMDw deposits was also analyzed, and oxygen was found to be in the range of conventional gas-shielded weldments. Nitrogen loss occurred when Ar-shielding was used; however, the use of N2-shielding prevented nitrogen loss. Austenite content was nearly doubled by using N2-shielding instead of Ar-shielding. The heat treatment resulted in an increase of the austenite content and of the homogeneity in the microstructure regardless of the shielding gas used. The similarity in microstructure and the low spread in the phase balance for the as-deposited geometries is a sign of having achieved a stable and consistent LMDw process in order to proceed with the build-up of more complex geometries closer to industrial full-size components.

  • 32.
    Valiente Bermejo, María Asunción
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Wessman, Sten
    Swerim AB, Kista, Sweden.
    Computational thermodynamics in ferrite content prediction of austenitic stainless steel weldments2019Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, nr 3, s. 627-635Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, four computational approaches using Thermo-Calc and DICTRA have been used to calculate the ferrite content of a set of austenitic stainless steel welds with different solidification modes and ferrite contents. To evaluate the computational approaches, the calculations were compared to the experimental results. It was found that for each solidification mode, there is one computational approach that predicts ferrite with better accuracy. For ferritic-austenitic alloys, the best accuracy is obtained when considering the peritectic model, with deviations of 1.2–1.4% ferrite. In the case of austenitic-ferritic alloys, the solidification analysed through the eutectic approach showed an accuracy of 0.6–1.6% ferrite, whilst in alloys with fully ferritic solidification, starting calculations, not from the liquid state but from fully ferritic below solidus, was the best approach, showing 2.3% ferrite deviation from the experimental measurements. Computational thermodynamics has proved to be a promising tool to explore simulation and calculation of ferrite content phase fractions in welding. However, further investigation is still needed to correlate the real microstructural features with the computational parameter “cell size”. The feasibility and accuracy of computational thermodynamics when predicting ferrite in low-heat-input welding processes such as laser welding is also another aspect for additional investigation.

    Fulltekst (pdf)
    fulltext
  • 33.
    Åstrand, Erik
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). Volvo Construction Equipment AB, Braås, Sweden .
    Stenberg, T.
    Royal Institute of Technology (KTH), Department of Aeronautical and Vehicle Engineering, Division of Lightweight Structures, Stockholm, Sweden .
    Jonsson, B.
    Volvo Construction Equipment AB, Braås, Sweden .
    Barsoum, Z.
    Royal Institute of Technology (KTH), Department of Aeronautical and Vehicle Engineering, Division of Lightweight Structures, Stockholm, Sweden .
    Welding procedures for fatigue life improvement of the weld toe2016Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, nr 3, s. 573-580Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the results of an experimental study of gas metal arc welded, GMAW, cruciform joints made of common construction steel S355. The hypothesis is that smooth undercuts in as welded conditions can give enhanced fatigue properties similarly as post treated welds. Undercuts are generally seen as a defect or imperfection. Welders try to avoid these and repair them when they occur, which result in increased production lead time. Post weld improvement methods i.e. grinding or high-frequency-impact treatment (HFMI) as fatigue-enhancing post-treatment methods enforce amongst other effects a certain smooth undercut-shaped groove in the treated weld toe region. The obtained shallower weld toe transition reduces the geometrical notch effect and increases fatigue strength. This paper presents a study whereas welded specimens with a weld toe geometry similar to what is obtained by weld toe grinding or HFMI-treatment, has been produced, fatigue tested and analyzed. The improvement of the fatigue strength is comparable to post-weld treated specimens. It has proven to be an efficient way to achieve high-quality welds without introducing any additional operations in production, thus enabling weight reduction using cost-effective methods.

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