Change search
Link to record
Permanent link

Direct link
BETA
Valiente Bermejo, María AsunciónORCID iD iconorcid.org/0000-0003-3374-6282
Publications (10 of 13) Show all publications
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, ISSN 2076-3417, 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 ()
Funder
Knowledge Foundation, 20140046
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2019-05-16
Valiente Bermejo, M. A. & Wessman, S. (2019). Computational thermodynamics in ferrite content prediction of austenitic stainless steel weldments. Welding in the World, 3(3), 627-635
Open this publication in new window or tab >>Computational thermodynamics in ferrite content prediction of austenitic stainless steel weldments
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 3, no 3, p. 627-635Article in journal (Refereed) Published
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.

Keywords
Computational thermodynamics, Ferrite, Welding, Stainless steels
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13200 (URN)10.1007/s40194-018-00685-x (DOI)000466107400006 ()2-s2.0-85064945437 (Scopus ID)
Note

First Online: 05 December 2018

Funders: Stiftelsen Axel Hultgrens fond; Swerim AB

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2019-05-16Bibliographically approved
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
Show others...
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: 2019-06-11
Hosseini, V. A., Valiente Bermejo, M. A., Gårdstam, J., Hurtig, K. & Karlsson, L. (2016). Influence of multiple thermal cycles on microstructure of heat-affected zone in TIG-welded super duplex stainless steel. Welding in the World, 60(2), 233-245
Open this publication in new window or tab >>Influence of multiple thermal cycles on microstructure of heat-affected zone in TIG-welded super duplex stainless steel
Show others...
2016 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, no 2, p. 233-245Article in journal (Refereed) Published
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.

Keywords
Duplex stainless steels, GTA welding, multirun welding, heat affected zone, microstructure, mathematical models, energy input
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-9001 (URN)10.1007/s40194-016-0300-5 (DOI)000374785100007 ()2-s2.0-84958787089 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2016-02-05 Created: 2016-02-05 Last updated: 2019-05-20Bibliographically approved
Valiente Bermejo, M. A., Karlsson, L., Svensson, L.-E., Hurtig, K., Rasmuson, H., Frodigh, M. & Bengtsson, P. (2016). Influenza del gas di protezione sul comportamento e le proprietà  di giunti sa dati di acciai duplex e superduplex: Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds. Rivista Italiana della Saldatura, 68(5), 635-650
Open this publication in new window or tab >>Influenza del gas di protezione sul comportamento e le proprietà  di giunti sa dati di acciai duplex e superduplex: Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds
Show others...
2016 (English)In: Rivista Italiana della Saldatura, ISSN 0035-6794, Vol. 68, no 5, p. 635-650Article in journal (Other academic) Published
Abstract [en]

The influence of shielding gases on welding performance and on properties of duplex and superduplex stainless steel welds was studied. Using argon as the reference gas, helium, nitrogen and carbon dioxide were added and five mixtures evaluated. Bead-on-plate welds and circumferential pipe welds were produced using mechanised GMA welding in the downhand position. Welding performance, corrosion resistance, mechanical properties, microstructural features and weld imperfections were assessed and related to the shielding gas. Shielding gases containing 30% helium showed excellent results; whilst pure argon showed unstable arc and poor weld pool fluidity and Ar + 2% CO2resulted in underfill and porosity. Mixtures containing helium resulted in higher ductility welds and higher impact toughness values than welds produced with Ar + 2% CO2. Sound and balanced duplex microstructures free from intermetallics were found with suitable ferrite contents for all the shielding gases studied. All the duplex pipe welds passed the corrosion test regardless of the shielding gas used, and the best results in the corrosion test for superduplex pipe welds were found when using Ar + 30%He + 0.5% CO2+ 1.8% N2as shielding gas.

Place, publisher, year, edition, pages
Istituto Italiano della Saldatura, 2016
Keywords
Argon; Atmospheric corrosion; Carbon; Carbon dioxide; Corrosion; Corrosion resistance; Electric arc welding; Gas metal arc welding; Gases; Helium; Intermetallics; Laser beam welding; Mechanical properties; Microstructural evolution; Mixtures; Nitrogen; Shielding; Welding; Welds, Corrosion tests; Duplex microstructures; Duplex stainless steel; Ferrite content; GMA welding; Microstructural features; Shielding gas; Superduplex stainless steels, Stainless steel
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10454 (URN)2-s2.0-85002857105 (Scopus ID)
Note

Published in English with a Italian translation.

Available from: 2017-01-03 Created: 2017-01-02 Last updated: 2019-05-21Bibliographically approved
Valiente Bermejo, M. A., Hurtig, K., Hosseini, V., Karlsson, L. & Svensson, L.-E. (2016). Monitoring Thermal Cycles in Multi-pass Welding. In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016. Paper presented at The 7th International Swedish Production Symposium SPS16 25th – 27th of October 2016 (pp. 1-5). Swedish Production Academy
Open this publication in new window or tab >>Monitoring Thermal Cycles in Multi-pass Welding
Show others...
2016 (English)In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Swedish Production Academy , 2016, p. 1-5Conference paper, Published paper (Refereed)
Abstract [sv]

Differently from any previous investigation in welding, this research work presents a novel development that allows temperature to be measured and recorded simultaneously with up to 32 thermocouples indifferent locations of a welding joint. Four experiments were designed to optimise the measurement technique by comparing the performance of three types of thermocouples (K, N, C) insulated with different materials and varying the insertion technique of the thermocouples in the joint. Results showed that type-K thermocouple had the best performance and proved that glass fibre insulation provided better protection than Inconel. The optimised measurement procedure developed in this work enables to monitor the thermal cycles in multi-pass welds. That information is essential in multi-pass welding of materials such as super duplex stainless steels, carbon steels or nickel alloys, as heating them repeatedly makes them susceptible to the formation of brittle phases and in turn it influences their mechanical and corrosion properties. This technique could be really important for future applications such as temperature modellingor prediction of mechanical properties and microstructure in relation to the thermal cycle experienced by alloys susceptible to the formation of undesirable phases.

Place, publisher, year, edition, pages
Swedish Production Academy, 2016
Keywords
Thermocouple, multi-pass welding, thermal cycle
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-10089 (URN)
Conference
The 7th International Swedish Production Symposium SPS16 25th – 27th of October 2016
Available from: 2016-10-31 Created: 2016-10-31 Last updated: 2019-04-03Bibliographically approved
Valiente Bermejo, M. A., Karlsson, L., Svensson, L.-E., Hurtig, K., Rasmuson, H., Frodigh, M. & Bengtsson, P. (2015). Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds. Welding in the World, 59(2), 239-249
Open this publication in new window or tab >>Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds
Show others...
2015 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, no 2, p. 239-249Article in journal (Refereed) Published
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.

Keywords
Duplex stainless steels, welding, GMAW, shielding gases
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7006 (URN)10.1007/s40194-014-0199-7 (DOI)2-s2.0-84922277059 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2019-05-14Bibliographically approved
Valiente Bermejo, M. A., Karlsson, L., Svensson, L.-E., Hurtig, K., Rasmuson, H., Frodigh, M. & Bengtsson, P. (2015). Effect of welding position on properties of duplex and superduplex stainless steel circumferential welds. Welding in the World, 59(5), 693-703
Open this publication in new window or tab >>Effect of welding position on properties of duplex and superduplex stainless steel circumferential welds
Show others...
2015 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, no 5, p. 693-703Article in journal (Refereed) Published
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.

Keywords
Duplex stainless steel, Welding, GMA welding, Welding position
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7590 (URN)10.1007/s40194-015-0245-0 (DOI)000363866000010 ()2-s2.0-84938504405 (Scopus ID)
Available from: 2015-05-08 Created: 2015-05-08 Last updated: 2017-12-04Bibliographically approved
Valiente Bermejo, M. A. (2015). Guia de les escultures de Mollet del Vallès: Metalls, tècniques i curiositats (1ed.). Ajuntament de Mollet del Vallès
Open this publication in new window or tab >>Guia de les escultures de Mollet del Vallès: Metalls, tècniques i curiositats
2015 (Catalan; Valencian)Book (Other (popular science, discussion, etc.))
Abstract [en]

This publication presents a comprehensive study on the current 35 metal artwork pieces located in public spaces of Mollet del Vallès. The sculptures are described from a technical perspective: metallic alloys, joining techniques and protective mechanisms against corrosion are described. However, this research also reveals interesting curiosities and secrets hidden by these sculptures. The information is organised in clear datasheets, where the technical details from the experimental observation and from the official technical project reports are summarised. The symbolisms, anecdotes and curiosities included in this work were gathered during fruitful conversations with authors, authorities and companies involved in the execution of the metal works. The main aim of this work is to invite the reader to stroll into town, to rediscover our heritage, to appreciate it and to make new generations love it. 

Place, publisher, year, edition, pages
Ajuntament de Mollet del Vallès, 2015. p. 117 Edition: 1
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7585 (URN)978-84-938025-8-5 (ISBN)
Available from: 2015-05-07 Created: 2015-05-07 Last updated: 2015-06-12Bibliographically approved
Valiente Bermejo, M. A. & Zhang, Z. (2015). Relevance and limitations of arc furnace casting in welding research. International Journal of Cast Metals Research, 28(2), 97-104
Open this publication in new window or tab >>Relevance and limitations of arc furnace casting in welding research
2015 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 28, no 2, p. 97-104Article in journal (Refereed) Published
Abstract [en]

The arc furnace melting technique is widely used for positive material identification in the industry of welding consumable manufacturing. It is also a convenient method for sample preparations ofvarious pre-design chemical compositions for investigations on solidification, phase transformationand microstructure of different alloys. However, up to now, welding research works using the arc furnace melting technique did not report to follow any international standard. This is the first time that an international standard involving arc furnace casting is discussed and evaluated to be applied in the welding research field. In this paper, the specimens obtained with the ASTM E1306-94 standard are assessed, and some suggestions are proposed for modification and improvement of the standard, like adding some intermediate steps including the turning over ofthe specimen and an extra melting. By adopting those proposals in the procedure, cast samples with complete melting and chemical composition homogeneity were achieved.

Keywords
Arc furnace remelting, Casting, Welding, ASTM E1306
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7048 (URN)10.1179/1743133614Y.0000000139 (DOI)000348856900005 ()2-s2.0-84920377908 (Scopus ID)
Available from: 2014-12-01 Created: 2014-12-01 Last updated: 2019-05-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3374-6282

Search in DiVA

Show all publications