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Hosseini, V., Hurtig, K. & Karlsson, L. (2020). Bead by bead study of a multipass shielded metal arc-welded super-duplex stainless steel. Welding in the World
Open this publication in new window or tab >>Bead by bead study of a multipass shielded metal arc-welded super-duplex stainless steel
2020 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Article in journal (Refereed) Epub ahead of print
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.

Keywords
Multipass welding; Super-duplex stainless steel; Ferrite content; Sigma phase; Nitrides
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14753 (URN)10.1007/s40194-019-00829-7 (DOI)2-s2.0-85075381068 (Scopus ID)
Funder
Vinnova, 2016-02834EU, Horizon 2020, 823786
Available from: 2019-12-12 Created: 2019-12-12 Last updated: 2020-01-17Bibliographically approved
Devotta, A. M., Sivaprasad, P. V., Beno, T., Eynian, M., Hurtig, K., Magnevall, M. & Lundblad, M. (2019). A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime. Metals, 9(5), Article ID 528.
Open this publication in new window or tab >>A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime
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2019 (English)In: Metals, Vol. 9, no 5, article id 528Article in journal (Refereed) Published
Abstract [en]

In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
flow stress; modified Johnson-Cook model; dynamic strain aging
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13989 (URN)10.3390/met9050528 (DOI)2-s2.0-85066741813 (Scopus ID)
Funder
Swedish Research Council, 20110263, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2020-01-15Bibliographically approved
Valiente Bermejo, M. A., Hurtig, K., Eyzop, D. & Karlsson, L. (2019). A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel. Applied Sciences, 9(6), Article ID 1050.
Open this publication in new window or tab >>A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel
2019 (English)In: Applied Sciences, Vol. 9, no 6, article id 1050Article in journal (Refereed) Published
Abstract [en]

Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate—and not the time exposed at the critical temperature range—seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and σ-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and σ-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
multi-pass welding, nitrides, secondary austenite, superduplex stainless steel, thermal cycles, welding, sigma-phase
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13730 (URN)10.3390/app9061050 (DOI)000465017200015 ()2-s2.0-85063719317 (Scopus ID)
Funder
Knowledge Foundation, 20140046
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2020-01-14
Hosseini, V., Hurtig, K., Eyzop, D., Östberg, A., Janiak, P. & Karlsson, L. (2019). Ferrite content measurement in super duplex stainless steel welds. Welding in the World, 63(2), 551-563
Open this publication in new window or tab >>Ferrite content measurement in super duplex stainless steel welds
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2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 2, p. 551-563Article in journal (Refereed) Published
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.

Keywords
Ferrite fraction, Ferrite number, Image analysis, Round Robin, Super duplex stainless stee, l Point counting
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13198 (URN)10.1007/s40194-018-00681-1 (DOI)000462318600028 ()2-s2.0-85063276679 (Scopus ID)
Funder
Vinnova, 2016-02834Knowledge Foundation, 20140130
Note

First Online: 05 December 2018

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2019-06-11Bibliographically approved
Raza, T., Hurtig, K., Asala, G., Andersson, J., Svensson, L.-E. & Ojo, O. A. (2019). Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718. Metals, 9(8), Article ID 881.
Open this publication in new window or tab >>Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718
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2019 (English)In: Metals, E-ISSN 2075-4701, Vol. 9, no 8, article id 881Article in journal (Refereed) Published
Abstract [en]

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
selective laser melting; Alloy 718; heat treatments; gas tungsten arc welding; heat affected zone cracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14595 (URN)10.3390/met9080881 (DOI)000484510000071 ()2-s2.0-85073280907 (Scopus ID)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2020-01-14
Hosseini, V., Högström, M., Hurtig, K., Valiente Bermejo, M. A., Stridh, L.-E. & Karlsson, L. (2019). Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization. Welding in the World, 63(4), 975-987
Open this publication in new window or tab >>Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization
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2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 4, p. 975-987Article in journal (Refereed) Published
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).

Keywords
Duplex stainless steels; Additive manufacturing; GMAW; Thermal cycles; Austenite fraction; Secondary phases
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13947 (URN)10.1007/s40194-019-00735-y (DOI)000468518900005 ()2-s2.0-85066099481 (Scopus ID)
Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2020-01-15
Li, P., Hurtig, K., Högström, M., Svensson, L.-E. & Scotti, A. (2018). A contribution to the study of negative polarity in GMA welding. The International Journal of Advanced Manufacturing Technology, 95(5-8), 2543-2553
Open this publication in new window or tab >>A contribution to the study of negative polarity in GMA welding
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2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, no 5-8, p. 2543-2553Article in journal (Refereed) Published
Abstract [en]

GMAW using the electrode with negative polarity (DCEN) has been frequently suggested as a potential means of increasing production capacity. The objective of this work was to further study the performance of negative polarity in GMAW of carbon steels. In this project phase, bead-on-plate welds were carried out in flat position to assess the effect of different potential shielding gas compositions on bead geometry, finishing and spattering. The characteristics were compared with DCEP at the same current, but depositing the same volume of material per unit of length (more industrial related comparison). The arc length was kept the same by adjusting voltage to reach shortest arcs, yet with suitable non short-circuiting metal transfer mode. An approach to measure bead convexity was also proposed and assessed. The results showed that DCEN is feasible as a means of increasing GMAW production capacity. However, to become DCEN applicable with GMAW, the results suggest an Ar based blend with around 6.5 % of O2 is the most appropriate shielding gas, as much as that there is a demand for a standard electronic controlled power source able to work in constant current mode. 

Keywords
Welding; Production; GMAW; Negative Polarity; Fusion rate; Weld bead geometry
National Category
Other Mechanical Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11817 (URN)10.1007/s00170-017-1349-z (DOI)2-s2.0-85035104454 (Scopus ID)
Projects
Maplab
Funder
Region Västra Götaland, RUN 612-0254-15
Note

Funders: Swedish Agency for Economic and Regional Growth, 20200328.

Available from: 2017-11-26 Created: 2017-11-26 Last updated: 2019-05-28Bibliographically approved
Singh, S., Hurtig, K. & Andersson, J. (2018). Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 314. Paper presented at 8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018. Procedia Manufacturing, 351-357
Open this publication in new window or tab >>Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 314
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, p. 351-357Article in journal (Other academic) Published
Abstract [en]

This study investigates the solidification cracking susceptibility of the austenitic stainless steel 314. Longitudinal Varestraint testing was used with three different set of welding test parameters. Weld speed, current and voltage values were selected so that the same heat input resulted in all the test conditions. From the crack measurements it was seen that the test condition with the lowest current and welding speed value also produced the least amount of cracking with very good repeatability.

Keywords
Solidification cracking, Steel 314, Varestraint testing, Welding parametres
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12852 (URN)10.1016/j.promfg.2018.06.103 (DOI)2-s2.0-85065672039 (Scopus ID)
Conference
8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018
Funder
Swedish Energy Agency
Note

Del av specialnumret Proceedings of the 8th Swedish Production Symposium (SPS 2018) Redaktörer: M. Onori, L. Wang, X. V. Wang och W. Ji

The authors would like to acknowledge Sumitomo SHI FW for providing the test material. The support from KME through funding from the Swedish Energy Agency and GKN Aerospace Sweden AB is highly appreciated.

Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2019-06-05Bibliographically approved
Hanning, F., Hurtig, K. & Andersson, J. (2018). Measurement of the thermal cycle in the base metal heat affected zone of cast ATI ® 718Plus TM during manual multi-pass TIG welding. Paper presented at 8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018. Procedia Manufacturing, 25, 443-449
Open this publication in new window or tab >>Measurement of the thermal cycle in the base metal heat affected zone of cast ATI ® 718Plus TM during manual multi-pass TIG welding
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 443-449Article in journal (Refereed) Published
Abstract [en]

This paper presents a method to acquire thermal data in the base metal heat affected zone (HAZ) during manual multi-pass TIG welding of ATI ® 718Plus TM , representing conditions close to an actual repair welding operation. Thermocouples were mounted in different locations along side walls of linear grooves to record temperature data. The thermal cycling was found to be largely independent of location within the HAZ. The recorded temperatures were below the incipient laves melting temperature, indicating that the current test setup requires optimisation to study HAZ liquation. Based on the results of this study, a modified thermocouple mounting technique is proposed. © 2018 Elsevier B.V. All rights reserved.

Keywords
Nickel-based superalloys, Welding, Temperature measurement
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13922 (URN)10.1016/j.promfg.2018.06.115 (DOI)2-s2.0-85065664942 (Scopus ID)
Conference
8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018
Funder
Swedish Energy Agency
Available from: 2019-06-05 Created: 2019-06-05 Last updated: 2019-07-23Bibliographically approved
Hosseini, V., Karlsson, L., Hurtig, K., Choquet, I., Engelberg, D., Roy, M. J. & Kumara, C. (2017). A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients. Materials & design, 121(May), 11-23
Open this publication in new window or tab >>A novel arc heat treatment technique for producing graded microstructures through controlled temperature gradients
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2017 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 121, no May, p. 11-23Article in journal (Refereed) Published
Abstract [en]

This paper introduces a novel arc heat treatment technique to produce samples with graded microstructures through the application of controlled temperature gradients. Steady state temperature distributions within the sample can be achieved and maintained, for times ranging from a few seconds to several hours. The technique reduces the number of samples needed to characterize the response of a material to thermal treatments, and can consequently be used as a physical simulator for materials processing. The technique is suitable for conventional heat treatment analogues, welding simulations, multi-step heat treatments, and heat treatments with controlled heating and cooling rates. To demonstrate this technique, a super duplex stainless steel was treated with a stationary TIG arc, to confirm the relationship between generated steady-state temperature fields, microstructure development, hardness, and sensitization to corrosion. Metallographic imaging and hardness mapping provided information about graded microstructures, confirming the formation of secondary phases and microstructure sensitization in the temperature range 850–950 °C. Modelling of temperature distributions and thermodynamic calculations of phase stabilities were used to simulate microstructure development and associated welding cycles.

Keywords
Stationary arc, Heat treatment, Graded microstructure, Super duplex stainless steels, Physical simulation, Welding
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-10760 (URN)10.1016/j.matdes.2017.02.042 (DOI)000399625000002 ()2-s2.0-85013031461 (Scopus ID)
Funder
Knowledge Foundation
Note

Funders: EPSRC (EP/L01680X/1) through the Materials for Demanding Environments Centre for Doctoral Training.

Available from: 2017-02-28 Created: 2017-02-28 Last updated: 2019-05-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0234-3168

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