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Master's Dissertation
DOI
https://doi.org/10.11606/D.97.2013.tde-07102013-114545
Document
Author
Full name
Isabel Rocha do Monte
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Lorena, 2013
Supervisor
Committee
Sandim, Hugo Ricardo Zschommler (President)
Coelho, Gilberto Carvalho
Rios, Paulo Rangel
Title in Portuguese
Caracterização microestrutural do Aço API 5L X65 soldado por feixe de elétrons com diferentes aportes térmicos
Keywords in Portuguese
Aço API 5L X65
Constituintes microestruturais
Soldagem por feixe de elétrons
Abstract in Portuguese
Esta Dissertação abrange a caracterização microestrutural do aço API 5L X65 soldado por feixe de elétrons (EBW) com cinco diferentes aportes térmicos e sem o uso de metal de adição. O aço API 5L X65 pertence à classe de aços ARBL e é empregado na fabricação de oleodutos e gasodutos. As três regiões da solda metal-base (MB), zona termicamente afetada (ZTA) e zona fundida (ZF) foram caracterizadas por microscopia ótica (MO), microscopia eletrônica de varredura (MEV), difração de raios X e medidas de microdureza Vickers. As microestruturas encontradas nestas três regiões são bastante distintas. O MB apresenta grãos ferríticos com bandas perlíticas orientadas paralelamente à direção de laminação. Devido à elevada densidade de potência do processo EBW e às elevadas velocidades de soldagem utilizadas, a ZTA é bastante estreita sendo formada por grãos ferríticos finos e bandas perlíticas degeneradas que a diferem do MB. Na interface ZTA/ZF foi possível observar a presença de grãos com morfologia acicular com a presença dos constituintes M-A (martensita-austenita). A ZF apresentou morfologia similar à encontrada em aços microligados soldados: ferrita alotriomórfica, ferrita acicular, ferrita de Widmanstätten, constituintes M-A, além de regiões bainíticas. Na parte central da chapa foi observada a segregação de manganês. A técnica EBW permite a soldagem de tubos com paredes espessas com apenas um passe. Os resultados desta Dissertação são úteis para avaliar a viabilidade técnica do uso de EBW na fabricação de tubos para o transporte de óleo e gás, especialmente em aços mais resistentes (bainíticos).
Title in English
Microstructural characterization of API 5L X65 steel welded by electron-beam with different heat inputs
Keywords in English
API 5L X65 steel
Electron beam welding
Microstructural constituents
Abstract in English
This Dissertation aims at the microstructural characterization of electron-beam welded (EBW) API 5L X65 steel using five different processing conditions (heat input) and without filler metal addition. The API 5L X65 steel is a high-strength low-alloy (HSLA) steel employed mainly in the manufacture of pipelines for oil and gas. The three regions of the welds, namely the base metal (BM), heat affected zone (HAZ) and fusion zone (FZ) were characterized by light optical microscopy using different chemical etching agents, scanning electron microscopy, X-ray diffraction and Vickers microhardness testing. The microstructures found in the three regions were quite distinct. The BM consists of elongated ferritic grains with pearlite bands oriented along the rolling direction. Due to the high power density provided by EBW, the HAZ is very narrow and consists of ferritic grains and bands of degenerated pearlite. At the HAZ/FZ interface it is possible to observe the presence of grains with acicular morphology and the presence of M-A (martensite- retained austenite) constituents. The FZ showed a morphology similar to that one found in molten microalloyed steels consisting of allotriomorphic ferrite, acicular ferrite, Widmanstätten-like ferrite, M-A constituents, as well as bainite. In the central part of the plate it was observed the presence of Mn-segregation lines along the BM. The electron beam welding was chosen because it produces a relatively small HAZ and it allows the welding of thick-wall tubes in one single pass. The results of this work are useful to evaluate the possibility of using EBW in the manufacture of pipelines for transport of oil and gas, especially in higher grade steels.
 
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EMD13002_C.pdf (4.69 Mbytes)
Publishing Date
2013-10-07
 
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