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Weld optimization with new Low Temperature Transformation fillermaterials
KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this study, evaluation of typical weld geometry, residual stresses and fatigue properties of two new LTT consumables have been performed. The literature survey discusses the topics of LTT consumables regarding fatigue life, chemical composition, dilution, crack phenomena and fatigue crack repair, impact toughness, weld residuals stress and weldgeometry. The experimental part of the project included LTTMAG welding trials, fatigue specimen development and production, fatigue testing and weld residual stress measurements. All welding were performed using mechanised MAG spray arc welding, performed on 8mm and 10mm thick DOMEX 650MC as rolled steel plates. The initial trials focused on finding good weld parameter to be used for the fatigue specimen production. For the specimen production, optimisation of the robot weld path, weld geometry and weld parameters were performed. Evaluations of the weld results were done in a standard metallurgical manner, and assessed according to current standard documentation. After the specimen production, fatigue testing were performed and evaluated. Residual stress levels were measured through Xray diffraction in as welded state. Observations and results have been presented and discussed. The most interesting results are:

- The two LTT filler reduced the tensile weld residual stressby 45% respectively 30% compared to the conventional MCW weld filler.

-The fatigue testing of the two LTT fillers resulted in a characteristic Natural Mean FAT of 127 MPa respectively 115MPa.

-In weld position PB, the LTT weld consumable gave betterweld toe radius against the flange plate compared to the conventional MCW filler.

Abstract [sv]

I denna studie har utvärdering av typiska svetsgeometrier, restspänningar och utmattningsegenskaper hos två nya LTT tillsatser utförts. Litteraturstudien diskuterar ämnet LTT med avsende på utmatntningslivslängd, kemisk sammansättning, uppblandning, sprickfenomen och lagning av utmatningssprikor, slagseghet, svetsegenspänning samt svetsgometri. I den experimentella delen av projektet utfördes LTT MAGsvetsning, utvekling och tillverkning av utmatningsprovstavar, utmattningsprovning och restspänningsmätning. All svetsning utfördes med mekaniserad MAG-svetsning på 8mm och 10mm tjock DOMEX 650MC stålplåtar. De tidiga svetsförsöken utfördes för att hitta hitta bra svets parameter som skulle användas vid svetsning av utmatnings provstavarna. Provstavstillverkningen innefattade optimering av robot svetsbanan, svetsgeometri och parametrer optimering. Utvärderinga av svetsresulaten utfördes metalurgiskt och bedömdeses enligt gällande standard dokumentation. Efter provstavsproduktion, utfördes utmatnningsprovning och utvärdering. Restspänningen mättes med röntgendiffraktion. Observationer och resultat är presenterats och har diskuterats. De mest intressanta resultaten är :

- De två LTT tillsatserna minskade dragrestspänningen med 45 % respektive 30 % jämfört med ett konventionelt tillsatsmaterial (MCW).

- Utmattningsprovningen av de två LTT-tillsatserna resulterade i en karakteristisk utmatningshållfasthet av 127MPa respektive 115 MPa.

- I svetsposition PB, gav LTT tillsatserna bättre svetstå radier mot flänsen plåten jämfört med den konventionelt tillsatsmaterial(MCW).

Place, publisher, year, edition, pages
2013. , 138 p.
Series
Degree Project in Production Engineering, Second Level, 572
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-134350OAI: oai:DiVA.org:kth-134350DiVA: diva2:666046
Examiners
Available from: 2013-11-21 Created: 2013-11-21 Last updated: 2013-11-21Bibliographically approved

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