In der Arbeit werden spezielle Kupferlote im MIG- und Laserlötverfahren an Stählen mit unterschiedlichem Festigkeitsverhalten untersucht. Die Ergebnisse sollen dazu beitragen, den Lötprozess durch den Einsatz spezieller Kupferbasislote zu optimieren und durch reduzierten Energieeintrag ein homogeneres Eigenschaftsfeld im Bereich der Fügestelle zu erzeugen. Den Verarbeitern dieser Werkstoffe soll die Möglichkeit gegeben werden, diese Werkstoffe rationeller und mit höherer Effektivität zu verarbeiten. Im Ergebnis der Arbeit sollen Verbesserungen der Eigenschaften der Lötnähte erzielt werden, die besonders in der Dünnblechverarbeitung mit Schwerpunkt Karosseriebau Anwendung finden. Wesentliche Ziele sind die Erhöhung der Festigkeitseigenschaften, eine Erhöhung der Fügegeschwindigkeit, die Verbesserung des Phosphatierungsverhaltens sowie eine Reduzierung der eingebrachten Wärmeenergie. Die Vielfältigkeit dieser Anforderungen macht es notwendig, die Versuche sowohl im Laser- als auch im MIG-Lötverfahren durchzuführen. Die Lötverfahren werden in der Praxis für unterschiedliche Anforderungen innerhalb der Karosserie eingesetzt. Das Fügen von hochfesten Strukturelementen oder Außenhautbauteilen erfordert in Abhängigkeit von den Anforderungen die Verwendung ausgewählter Zusatzwerkstoffe. Die Vielfältigkeit der Werkstoffe und der Anforderungen spiegelt sich in den Untersuchungen der vorliegenden Arbeit wieder. Für weitergehende Untersuchungen, speziell im hochfesten Blechbereich, soll die Arbeit entsprechende Grundlagen bieten. Als Vorlage für die Erarbeitung von experimentellen und theoretischen Methodiken der Prozessbetrachtung werden neben typischen Kupferloten neu entwickelte Lotlegierungen verwendet. Bei der Betrachtung der Kupferlegierungen werden die unterschiedlichen Einflüsse auf den Fügeprozess definiert und beschrieben. Es wird festgestellt, dass niedrig schmelzende Lote mit ausgewählter Legierungszusammensetzung im Gegensatz zu Eisenbasis-Schweißdrähten einen geringeren negativen Einfluss auf das Gefüge der Bleche im Nahtbereich ausüben. Um die thermische Beanspruchung, besonders in der Wärmeeinflusszone, während des Fügeprozesses gering zu halten, kann zusätzlich eine geeignete Stromquellentechnik zum Einsatz kommen. Mit Hilfe des „kalten“ Lichtbogens ist es möglich, die eingebrachte Streckenenergie weiter zu reduzieren. Faktoren, die den Energieeintrag beeinflussen, werden in der vorliegenden Arbeit in experimentellen und theoretischen Untersuchungen hinsichtlich ihrer Wirkung auf das Festigkeitsverhalten betrachtet. Es werden durch geeignete Legierungskombinationen die Einflüsse auf die Steigerung der Lötgeschwindigkeit und auf eine Verbesserung des Phosphatierungsverhaltens untersucht. Die Ergebnisse dieser Untersuchungen liefern die Informations- und Beweisbasis für die erarbeiteten Legierungssysteme und ermöglichen es, den optimierten Lötprozess an hochfesten Stahlblechen wissenschaftlich zu betrachten. Die Auswertung der wissenschaftlichen Experimente, dargestellt in den angefügten ausführlichen Tabellen, stellen die Zusammenhänge zwischen der Legierungsauswahl und der eingebrachten Streckenenergie dar. Die Erkenntnisse aus der vorliegenden Arbeit sollen für das Fügen von hochfesten Blechen die Entscheidung über die Auswahl geeigneter Zusatzwerkstoffe erleichtern. Die Ergebnisse der theoretischen Untersuchungen anhand mathematischer Modelle zur Beschreibung der physikalischen Prozesse der Wärmezufuhr durch Verwendung eines ausgewählten Lotes in Kombination mit geeigneter Stromquellentechnologie sind die Grundlage für die Optimierung des Lötprozesses. Die vorgeschlagenen Modelle zur Entwicklung und Optimierung von Lichtbogenlötprozessen mit neu entwickelten Lotlegierungen wurde im Rahmen der vorgelegten Arbeit an realen Blechqualitäten angewendet und überprüft. In den Ergebnissen hat sich bestätigt, dass die Verwendung spezieller Kupferlote zu verbesserten Verarbeitungseigenschaften führen, und damit Konzepte zum wirtschaftlich verbesserten Fügen angeboten werden.:Inhalt 1. Einleitung. Kritische Bewertung der Literatur und Problemanalyse. 11 Perspektiven 1.1. Bedeutung des Lichtbogenlötens an höherfesten Stahlblechen 11 1.2. Entwicklungsstand bei höherfesten Dünnblechen und geeigneten 12 Lotwerkstoffen 1.3. Lichtbogenlöten an höherfesten Stahlblechen und Verfahrensgrenzen 15 2. Wissenschaftliche Problemstellung und Lösungsmöglichkeiten 16 2.1. Problemdarstellung 17 2.1.1. Problematik hochfester Grundwerkstoff 18 2.1.2. Löten vs. Schweißen 18 2.2. Lösungsstrategien und angestrebte Lösungswege 20 3. Theoretische Herleitung eines Mehrphasenmodells auf Kupferbasis 22 mit erhöhten Festigkeitseigenschaften 3.1. Voraussetzungen für die Legierungsbildung in Kupfer 22 3.2. Einfluss wesentlicher Legierungselemente auf die Eigenschaften von 26 Kupferlegierungen 3.2.1. Silizium 26 3.2.2. Aluminium 28 3.2.3. Mangan, Nickel, Zinn, Silber, Mikrolegierungselemente 29 3.3. Ermittlung optimierter Legierungen 30 3.4. Gieß- und ziehtechnische Einschränkungen 33 4. Versuchsdurchführung und Untersuchungsmethoden 34 4.1. Laserlöten 34 4.1.1. Grundwerkstoffe 34 4.1.2. Lote 34 4.1.3. Versuchsaufbau 36 4.1.4. Festlegung der Prozessdaten 37 4.1.5. Versuchsdurchführung 39 4.1.5.1. Bördelnaht DX54D+Z100 39 4.1.5.2. Überlappnaht DX54D+Z100 / HC180BD 40 4.1.5.3. Ermittlung der Benetzungswinkel bei unterschiedlichen 41 Lötgeschwindigkeiten 4.1.5.4. Korrosionsverhalten 43 4.2. MIG-Löten 44 4.2.1. Grundwerkstoffe 44 4.2.2. Lote 44 4.2.3. Versuchsaufbau 45 4.2.4. Messdatenerfassung 47 4.2.5. Versuchsdurchführung 48 4.2.5.1. Überlappnaht 22MnB5+AS 48 4.2.5.2. Überlappnaht HCT780XD Z70 (DP 800), HCT690T Z100 (TRIP700) 49 4.2.5.3. Ermittlung der Benetzungswinkel 49 4.2.5.4. Untersuchung des Wärmeeintrages 50 4.2.5.5. Phosphatierungsverhalten 51 5. Versuchsauswertung 52 5.1. Laserlöten 52 5.1.1. Visuelle Prüfung 52 5.1.1.1. Bördelnaht DX54D+Z100 52 5.1.1.2. Überlappnaht DX54D+Z100 / HC180BD 55 5.1.2. Statische Zugversuche 56 5.1.2.1. Bördelnaht DX54D+Z100 57 5.1.2.2. Überlappnaht DX54D+Z100 / HC180BD 58 5.1.3. Mikroskopische Untersuchungen 60 5.1.3.1. Bördelnaht DX54D+Z100 60 5.1.3.2. Überlappnaht DX54D+Z100 / HC180BD 63 5.1.4. Benetzungsverhalten 65 5.1.5. Beurteilung des Korrosionsverhaltens 67 5.2. MIG-Löten 69 5.2.1. Visuelle Prüfung 69 5.2.1.1. Überlappnaht 22MnB5+AS 69 5.2.1.2. Überlappnaht HCT780XD Z70 (DP 800), HCT690T Z100 (TRIP700) 71 5.2.2. Statische Zugversuche 73 5.2.2.1. Überlappnaht 22MnB5+AS 73 5.2.2.2. Überlappnaht HCT780XD Z70 (DP 800), HCT690T Z100 (TRIP700) 75 5.2.3. Härteverläufe 80 5.2.3.1. Überlappnaht 22MnB5+AS 80 5.2.3.2. Überlappnaht HCT780XD Z70 (DP 800), HCT690T Z100 (TRIP700) 82 5.2.4. Mikroskopische Untersuchungen 83 5.2.4.1. Überlappnaht 22MnB5+AS 83 5.2.4.2. Überlappnaht HCT780XD Z70 (DP 800), HCT690T Z100 (TRIP700) 86 5.2.5. Benetzungsverhalten 87 5.2.6. Schutzgas 89 5.2.7. Thermische Untersuchung 90 5.2.8. Phosphatierungsverhalten 92 6. Betrachtung von Optimierungskriterien 94 6.1. Werkstofftechnische Betrachtungen 95 6.1.1. Legierungssysteme 95 6.1.2. Einfluss von Oberflächenbeschichtungen 96 6.1.3. Streckenenergiebetrachtungen 96 6.2. Betrachtung des Einflusses von Nahtgeometrie, Schutzgas und 96 Gerätetechnik 6.2.1. Nahtgeometrie 96 6.2.2. Gerätetechnik 97 7. Übertragung der Ergebnisse auf andere hochfeste Stähle 97 8. Erprobung unter seriennahen Bedingungen 99 9. Zusammenfassung und Ausblick 101 10. Anhang 104

På avdelningar i Sverige vårdas idag kritiskt sjuka patienter. Observation av vitalparametrar kan leda till att försämringar hos patienten kan förutspås. En mobil intensivvårdsgrupp (MIG) kan stötta vårdavdelningar i arbetet med kritiskt sjuka patienter. I november 2014 startade Hallands Sjukhus, Halmstad ett barn-MIG. Syftet med studien var att undersöka sjuksköterskors erfarenheter av barn-MIG på Barn- och ungdomskliniken, Hallands Sjukhus. Studien har en kvalitativ design och materialet har bearbetats genom kvalitativ innehållsanalys. För att besvara studiens syfte gruppintervjuades sjuksköterskor som deltagit vid barn-MIG bedömningar på Hallands Sjukhus. Intervjuerna resulterade i tre kategorier: delaktighet, organisation och kompetens. I resultatet framkom att sjuksköterskorna har positiva erfarenheter av barn-MIG då modellen främjar gemensamt ansvar, patientsäkerhet och kompetensutveckling. För att stärka personalens kompetens efterlyste sjuksköterskorna ytterligare utbildning i hur barn-MIG bör tillämpas. Resultatet kan ge läsaren en inblick i hur MIG-modellen kan påverka arbetet på en barnavdelning. Resultatet kan vara till nytta om läsaren avser att utforma barn-MIG på ett annat sjukhus som bedriver barnsjukvård. Vidare studier skulle kunna belysa intensivvårdssjuksköterskornas erfarenheter av barn-MIG. Om barn-MIG introduceras på fler svenska sjukhus kan klinikerna gagnas av att utbyta erfarenheter och kunskap som utvecklar barn-MIG. / In Sweden, patients with critical illness are given care in Pediatric care units. Observation of vital signs can anticipate patient deterioration. A rapid response team (RRT) can support care units in their work with patients with critical illness. A pediatric RRT was established at the Hospital of Halland, Halmstad in November 2014. The aim of this study was to investigate experiences of the pediatric RRT from nurses working at the Pediatric Department at the Hospital of Halland, Halmstad. The study has a qualitative design and the material has been processed with qualitative content analysis. To answer the aim of the study, nurses who participated in pediatric RRT assessments at the Hospital of Halland were interviewed in groups. The interviews resulted in three categories: participation, organization and competence. The result showed that the nurses have a positive experience of pediatric RRT as the model promotes shared responsibility, patient safety and skill development. To strengthen staff skills, nurses requested further training in pediatric RRT. The result can give the reader an insight into how the RRT may affect the work at a Pediatric care unit. The reader may benifit from the result if intended to design a pediatric RRT in a hospital providing pediatric care. Further study could shed light on critical care nurses' experiences of pediatric RRT. If pediatric RRT’s are introduced on a number of Swedish hospitals, departments can benefit from sharing experiences and knowledge that develops pediatric RRT.

Antalet asylansökningar ökade markant under år 2015 vilket ledde till stora påfrestningar på såväl asylsystemet som de centrala samhällsfunktionerna. Till följd av flyktingströmmen infördes lagen (2016:752) om tillfälliga begränsningar av möjligheten att få uppehållstillstånd i Sverige (TUtlL). Denna lag medförde att flertalet av utlänningslagens (2005:716) paragrafer begränsades till EU-rättens och internationella konventioners miniminivå. Uppehållstillstånd på grund av anknytning till en alternativt skyddsbehövande i Sverige får därmed numera endast beviljas i de ärenden då ett avslag skulle strida mot ett svenskt konventionsåtagande.    I MIG 2018:20 uttalade migrationsöverdomstolen att ett avslag gällande uppehållstillstånd till följd av anknytning till ett barn som beviljats tillfälligt uppehållstillstånd med status alternativt skyddsbehövande strider mot artikel 8 Europeiska konventionen om skydd för de mänskliga rättigheterna och de grundläggande friheterna och artikel 3, 9 och 10 Förenta nationernas konvention om barnets rättigheter. Syftet med uppsatsen är att utreda om det föreligger någon skillnad mellan rätten till uppehållstillstånd i Sverige för föräldrar som åberopar anknytning till sitt minderåriga eller myndiga barn, samt när ett myndigt eller minderårigt barn ansöker om anknytning till sin förälder. Uppsatsen avgränsar sig till att utreda situationer då anknytningspersonen i Sverige är alternativt skyddsbehövande. Genom att konstatera skillnader eller likheter i de ovan nämnda anknytningssituationerna önskar vi sedan påvisa huruvida MIG 2018:20 kan komma att ha inverkningar utanför dess kärnområde eller med hänsyn till internationella åtaganden. Vidare syftar uppsatsen till att ur ett rättssäkerhetsperspektiv av professor Aleksander Peczenik redogöra för om TUtlL, gällande bestämmelserna om rätten till familjeåterförening, uppfyller kraven på en rättssäker tillämpning och i fall MIG 2018:20 kommer förbättra eller försämra rättssäkerheten. För att uppnå syftet kommer relevant gällande rätt i Sverige, EU och internationellt att studeras, speciellt ovan nämnda artiklar och artikel 16.3 Förenta nationernas allmänna förklaring om de mänskliga rättigheterna. Utöver dessa kommer även vilka kriterier en individ behöver uppfylla för att anses vara alternativt skyddsbehövande och principen om non-refoulement att studeras. Vi har i uppsatsen kommit fram till att rättstillämpningen mellan anknytningssituationerna påvisar stora rättsliga skillnader främst på grund av ålder, men även till följd av att det saknas relevant och analyseringsbar praxis. Det har således endast varit möjligt att konstatera att MIG 2018:20 kommer leda till en förbättring av rättssäkerheten gällande minderåriga barn då målet ökat BarnK:s status i svensk rätt. För att rättstillämpningen ej ska strida mot internationella åtaganden bör BarnK användas gällande omyndiga barn. Det är även möjligt att konstatera att de senaste årens tillämpning av bestämmelserna om rätten till familjeåterförening inte uppfyller kraven för en rättssäker tillämpning.

The mig-10 gene in C. elegans is required for proper axon guidance and/or cell migration of certain neurons during development. In mig-10 (ct41) mutant worms, there is incomplete migration of the anterior lateral microtubule cells (ALMs), hermaphrodite specific neuron (HSN), left coelomocyte cells (ccL), and canal associated neuron (CAN) (Manser and Wood, 1990). The mig-10 (ct41) mutation also causes axon guidance defects in the IL2 neurons, and it enhances unc-6 defects in the axon guidance of the anterior ventral microtubule cell (AVM) (Rusiecki, 1999; C. Quinn, personal communication). mig-10's function in axon guidance and neuronal migration is unknown, but is believed to be involved in a signal transduction pathway that uses a G-protein, such as ras. The two mig-10 transcripts discussed in this thesis, mig-10 A and mig-10 B, encode proteins that are similar to Grb-7 and Grb-10 proteins, which are also believed to function in a signal transduction pathway (Manser et al., 1997). One of these similarities is the presence of a proline-rich region, which may be used to bind another protein (Manser et al., 1997). The MIG-10 A protein has an additional proline region, compared to MIG-10 B, which may indicate that the MIG-10 A and B proteins are utilized in different cells, or at different developmental stages. As a first step in learning where MIG-10 is expressed, mig-10 (ct41) mutant worms containing a wild-type mig-10 B::GFP fusion were constructed. Rescue of the mutant phenotype would indicate that the expression pattern of the transgene was similar to that of the endogenous gene. As this experiment did not allow for rescue, even after integration of the construct, a strain of worms containing a mig-10 promoter::GFP transgene was used. Preliminary observations of this strain indicated that mig-10 is expressed in neuronal tissue. The AIY neurons were observed in wild-type and mig-10 (ct41) worms to determine if they are affected by the mig-10 mutation as previously reported (O. Hobert, personal communication). As no difference was detected, the AIYs were not used in any further experiments. In order to determine which cells require functional MIG-10 protein for the proper development/migration of neurons to occur, mig-10 (ct41) worms containing mec-3 promoter::mig-10 A or B cDNA transgenes were constructed. The mec-3 promoter drives expression of the mig-10 cDNA in the ALM neurons and other touch cells early in the development of the embryo. If these transgenes rescued the ALM migration defect, then mig-10 would be acting cell autonomously in ALM. Partial rescue was obtained, which may be due to the need for both of the mig-10 transcripts to be expressed in the same cell; alternatively, one or both transcripts may need to be expressed in a cell nonautonomous fashion in addition to being expressed cell autonomously. Low production of the rescuing protein, or expression of the protein at a later developmental stage than is needed for rescue to occur, may also have been the cause of the partial rescue. Future work in this area includes putting mig-10 promoter::mig-10 A or B cDNA in mig-10 (ct41) background to investigate if the different transcripts rescue different aspects of the mig-10 phenotype. The mig-10 A and mig-10 B cDNA constructs could also be expressed in the same worm in an attempt to correct for partial rescue that may be due to the lack of both MIG-10 proteins.

O presente trabalho objetiva estudar a eficiência térmica do arco elétrico e de fusão para o processo de soldagem MAG, do inglês Metal Active Gas, em diferentes geometrias de juntas soldadas. As soldas foram feitas inicialmente em um calorímetro de fluxo contínuo de água, seguidas de deposição de cordão sobre chapa e soldagem de juntas em ângulo “T”, sempre em aço carbono. A metodologia de projeto de experimentos Box-Behnken foi empregada para a avaliação da influência da variação dos parâmetros de soldagem (tensão, velocidade de alimentação do eletrodo e velocidade de soldagem) nas eficiências, dentro do modo de transferência metálica por curto circuito. Diferentes equações propostas na literatura para o cálculo da eficiência de fusão são comparadas. Para a adequada aquisição da eficiência térmica pelo calorímetro, preliminarmente é avaliada a influência da vazão de água e da geometria na entrada de um calorímetro de fluxo contínuo sobre a eficiência térmica do arco. O procedimento experimental consiste em testar diferentes vazões de água e três configurações geométricas na região de entrada de água no calorímetro: com rolha reta, com difusor cônico e com obstáculo. Os experimentos foram planejados e os resultados avaliados com base na análise de variância estatística de um único fator, no caso, a vazão de água na entrada do calorímetro. A maior eficiência térmica média de 80,5% foi obtida para a vazão de 4 l/min, com baixo erro estatístico, utilizando rolha de entrada com geometria de difusor cônico. O modelo em que o fluxo entra diretamente no tubo apresentou todos os valores de eficiência térmica do arco com pequeno decréscimo numérico se comparados com o difusor cônico, enquanto a rolha com obstáculo apresentou elevado erro estatístico. Com base nos resultados descritos, a eficiência térmica do arco elétrico foi avaliada com a vazão de 4 l/min para o projeto de experimentos Box-Behnken, os valores obtidos estão na faixa de 72 a 82% conforme a combinação dos parâmetros de soldagem. A velocidade de soldagem e a tensão do arco se mostraram como os parâmetros de maior influência na eficiência térmica do arco. Os resultados relativos à eficiência de fusão indicam maiores valores nas soldas realizadas no calorímetro e por simples deposição sobre chapa. A junta T apresentou os menores valores de eficiência de fusão e de diluição para todos os casos. O parâmetro de maior influência na eficiência de fusão foi a corrente de soldagem. / The main aim of the present work is to study arc thermal efficiency and fusion efficiency to Gas Metal Arc Welding – GMAW, using different joint geometries. At first, the welds were performed in a continuous water flow calorimeter, followed by bead on plate and T – joint deposits. The Box-Behken design of experiments methodology was used to analyze the effect of welding parameters (arc voltage, wire feed speed and welding speed) on the efficiencies, when using short circuit metal transfer. The results of the fusion efficiency calculation were compared using different equations found in the literature. To correctly evaluate the thermal efficiency, it was necessary to analyze the influence of water flow rate and calorimeter inlet geometry. The experimental procedure consists of varying water flow rate and testing three different calorimeter inlet seal geometries: straight seal, conical diffuser seal and seal with water flux obstacle. The experiments were designed and the results evaluated based in a one-factor statistical analysis of variance, in this case the inlet calorimeter water flow. The highest average thermal efficiency is 80.5% to water flow of 4 l/min, with a low statistical error, using the conical diffuser seal inlet geometry. The inlet with straight seal model shown all the arc thermal efficiency values with slightly lower numerical values compared with conical diffuser, while the seal with flux obstacle exhibited high statistical error. Based on these results, the arc thermal efficiency was evaluated using 4 l/min water flow to the Box-Behnken Design, resulting values in the 72 to 82% range, depending on the welding parameters. The welding speed and arc voltage were the parameters that significantly affect arc thermal efficiency. The fusion efficiency results of the welds performed on the calorimeter and bead on plate were. The welds performed in T joints exhibit lowest fusion efficiency and dilution to each welding parameters combination tested. The fusion efficiency is strongly affected by the welding current.

A aplicação de aços de alta resistência está fortemente difundida na indústria mecânica, principalmente em aplicações onde a redução de peso é importante, como por exemplo, a indústria de implementos rodoviários e maquinários agrícolas. Esta dissertação visa analisar a influência de diferentes aportes térmicos no comportamento microestrutural e mecânico de juntas soldadas através do processo MAG de modo a obter juntas com propriedades otimizadas. Para este estudo foram utilizadas chapas metálicas com espessura de 3 mm do aço de alta resistência e baixa liga USI LNE700. Os parâmetros nominais de energia de soldagem foram variados de acordo com os valores descritos pelo fornecedor SSAB. O processo de soldagem foi realizado com o auxílio de um sistema robotizado para manter a homogeneidade ao longo da junta, distância e posicionamento correto no comprimento total da junta soldada. Os ensaios para verificação do comportamento microestrutural e mecânico foram realizados com auxílio de microscopia ótica, perfis de microdureza e ensaios de tração. Buscaram-se utilizar aportes térmicos reduzidos para minimizar os efeitos de revenimento da martensita presente no metal de base, um dos principais responsáveis pela redução das propriedades mecânicas da junta soldada. Os resultados não mostraram significativa variações na microestrutura e propriedades de tração do material, porém o preenchimento da junta soldada formada apresenta um comportamento diretamente proporcional à energia de soldagem. / The application of high strength steels is strongly diffused in the engineering industry, especially in applications where weight reduction is important, such as the industry of agricultural machines and trailers industry. This investigation aims to analyze the influence of different heat inputs on microstructural and mechanical behavior of joint welded by GMAW in order to obtain joints with optimized properties. Sheet metal with a thickness of 3 mm high strength low alloy steel LNE700 (supplier Usiminas) were used. The welding energy was varied around the nominal value informed by the steel supplier SSAB for this study. The welding process was made using robotic system to maintain homogeneity along the joint, right distance and position during the total weld joint length. The microstructural and mechanical behaviors were performed with the optical microscope, microhardness profile and traction test. We attempted to use lower heat inputs to minimize the effects of tempering of martensite present in the base metal, a major contributor to the reduction of the mechanical properties of the welded joint. The results did not show significant microestructural and tensile properties variation, however, when the welding energy is increased, the welded joint penetration formed was increased as well.

Submitted by Cleide Dantas (cleidedantas@ufpa.br) on 2014-04-07T16:26:32Z No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AspectosMetalurgicosRevestimentos.pdf: 5320680 bytes, checksum: 75f9c2d40f9a30c809779506ac9808b0 (MD5) / Approved for entry into archive by Ana Rosa Silva (arosa@ufpa.br) on 2014-06-17T14:59:39Z (GMT) No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AspectosMetalurgicosRevestimentos.pdf: 5320680 bytes, checksum: 75f9c2d40f9a30c809779506ac9808b0 (MD5) / Made available in DSpace on 2014-06-17T14:59:39Z (GMT). No. of bitstreams: 2 license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) Dissertacao_AspectosMetalurgicosRevestimentos.pdf: 5320680 bytes, checksum: 75f9c2d40f9a30c809779506ac9808b0 (MD5) Previous issue date: 2012 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho estuda o perfil metalúrgico de revestimentos em dutos depositados pelos processos MIG C e MIG AF. A indústria petroquímica, e outras que utilizam dutos como meio de transporte de seus insumos, depara-se com um grande desafio: como aumentar a vida útil desses dutos em um ambiente severo de trabalho. No caso específico da petroquímica, os dutos servem como meio de transporte para petróleo e gás, que são produtos extremamente agressivos às paredes internas desses tubos que sofrem degradação por corrosão causada, principalmente, pela composição química, pressão e temperatura desses produtos. Nesse contexto a soldagem de revestimentos realizada com ligas à base de Níquel, torna-se uma excelente opção para a construção, reparo e manutenção de equipamentos cuja aplicação seja voltada a ambientes severos de trabalho, tornando possível aperfeiçoar as características requeridas, como por exemplo, a resistência à corrosão. É nesse cenário que surge o mote para a realização desta pesquisa, baseada em trabalhos que indicam que o processo de soldagem MIG/MAG com o da adição de arame frio possui a finalidade de avaliar as características metalúrgicas do revestimento em dutos depositados pelo processo derivativo MIG convencional – MIG-C e MIG com adição de arame frio – MIG AF – utilizando a liga de Níquel ERNiCrMo-4 em dutos de aço carbono. As soldas foram depositadas em dutos de diâmetro de 228,6 mm, formando uma camada de revestimento interno de quatro passes, divididos em três segmentos da circunferência do duto, em três diferentes energias de soldagem: 1,1; 0,9 e 0,7 kJ/mm. Desses segmentos retiraram-se corpos de prova dos dutos para a produção das amostras. Após a metalografia, realizada nas amostras, seguiu-se com a análise e caracterização ao microscópio óptico, microscópio eletrônico de varredura e ensaio de microdureza. Os revestimentos apresentaram excelente qualidade superficial para todos os pacotes operacionais aplicados na obtenção das soldas. As análises das regiões estudadas: metal de base; zona parcialmente misturada e zona termicamente afetada, mostraram-se compatíveis com os da literatura estudada, tanto para o MIG com adição de arame frio, quanto para o convencional. Na ZTA, foram observados valores de Tungstênio em torno de 1,0%, o aumento dos níveis de dureza foi creditado a esse fato. Os resultados de microdureza indicaram que para ambos os casos, MIG C e MIG AF, nas 4 regiões analisadas ocorreram de maneira semelhante, sendo a região da ZTA a que apresentou maiores valores na faixa de 400 a 500 HV, enquanto que nas demais regiões a faixa ficou entre 250 a 350 HV. Os resultados indicam que o processo com arame frio, MIG AF, mostrou-se tão eficiente quanto o convencional, MIG C. A energia de soldagem aumentou a diluição de Fe no metal de solda. Precipitados ricos em Mo e Cr foram encontrados no metal de solda. / This work is a metallurgical analysis of the inner lining layer of pipeline used in welding process MIG C and MIG AF. The petrochemical industry, and others that use pipelines for transportation of their raw materials, faces a major challenge: how to increase the useful life of these products in a harsh environment work? In the specific case of the petrochemical industry, whom this research is directed, the pipes serve as means of transportation for oil and gas, products that are extremely aggressive to the internal walls of these tubes that are degraded by corrosion, caused mainly, by chemical composition, pressure and temperature these products. In this context the welding of lining made with nickel-based alloys becomes an excellent option for the construction, repair and maintenance of equipment whose application be returned in harsh environments of work, allowing the improvement of characteristics required, such as the resistance to corrosion. It is this scenario that emerges the theme for this research, based on studies that indicate that the process of welding MIG / MAG with the addition of cold wire, has to evaluate the metallurgical characteristics of the pipeline coating deposited by the derivative process MIG conventional – MIG-C and MIG with the addition of cold wire - MIG AF - using Nickel alloy ERNiCrMo-4 in carbon steel pipelines. The welds were deposited in pipes of 228.6 mm of diameter, forming a layer of internal lining of four passes, divided into three segments of the circumference of the duct, in three different welding energy: 1.1, 0.9 and 0.7 kJ / mm. These segments are removed specimens of the ducts, for the production of the samples. After metallography, performed on the samples, followed with the analysis and characterization by optical microscope, scanning electron microscope and testing of microhardness. The coatings exhibited excellent surface quality for all operational packages used in obtaining the welds. The results of the analysis of the regions studied: metal base, partially mixed zone and heat affected zone, were compatible with the literature studied for both the MIG with the addition of cold wire, as for the conventional. In HAZ were observed values of Tungsten around 1.0%, the increased levels of hardness was credited to this fact. The microhardness results indicated that in both cases, MIG C and MIG AF, in 4 regions analyzed occurred similarly, and the HAZ region which showed the highest values in the range 400-500 HV, while in the other regions range was between 250-350 HV. The results indicate that the process with cold wire, MIG AF, was as efficient as the conventional MIG C. The welding power increased the dilution of Fe in the weld metal. Precipitates rich in Mo and Cr were found in the weld metal.

soldagem de aços inoxidáveis duplex AID SAF 2205 utilizando o processo Metal Active Gas (MAG) ainda tem poucos dados e referências, estes aços são conceituados devido ao seu equilíbrio entre resistência mecânica e à corrosão, resultado de sua microestrutura composta por austenita e ferrita. A soldagem dos aços inoxidáveis duplex exige um controle de aporte térmico, da composição química do metal de adição e gás de proteção. Mínimas mudanças em parâmetros e composição dos consumíveis podem afetar diretamente a estrutura formada na região da solda. Neste trabalho, o objetivo foi estudar a influência da utilização do processo de soldagem MAG com diferentes energias aplicadas ao AID SAF 2205, sobre a resistência à corrosão das amostras resultantes. Foram usados quatro valores de energias de soldagem, entre 0,6 e 1,1 kJ/mm, sendo a maior energia limitada à espessura das chapas, que era de 5 mm. Quando foi analisada a microestrutura formada na região da solda, a quantificação de ferrita na zona afetada pelo calor apresentou uniformidade nas amostras, independendo da energia de soldagem. Contudo, a quantidade de ferrita no metal de solda diminuiu à medida que a energia aumentou. A precipitação de nitretos de cromo foi observada no interior de alguns grãos de ferrita e/ou próximo a regiões com austenita secundária intragranular. Os perfis de microdureza Vickers não apresentaram nenhum valor acima de 300 HV, e nenhum comportamento diferenciado de acordo com área de indentação. A resistência à corrosão não apresentou mudanças consideráveis, o metal base e as regiões da solda nas quatro condições se comportaram de forma muito similar. Os ensaios de imersão em cloreto férrico, seguindo a ASTM G48, permitiram observar a formação de pites, mas a quantidade e densidade destes não pode ser associada a uma região da solda específica ou variação de energia de soldagem. Os valores de parâmetros eletroquímicos, OCP, ECORR, e EPIT, após os ensaios de polarização potenciodinâmica de acordo com a ASTM G5, tiveram pouca variação, mostrando um comportamento em corrosão similar para o metal base e para os metais de solda das quatro diferentes condições de energia de soldagem empregadas. / Welding of AID SAF 2205 duplex stainless steels using the Metal Active Gas (MAG) process still has few data and references, these steels are conceptualized due to their balance between mechanical resistance and corrosion, resulting from their microstructure composed of austenite and ferrite. The welding of duplex stainless steels requires a control of the thermal input, the chemical composition of the addition metal and the shielding gas. Minimal changes in parameters and composition of consumables will directly affect the structure formed in the region of the weld. In this work, the objective was to study the influence of the MAG welding process with different energies applied to AID SAF 2205, on the corrosion resistance of the resulting samples. Four values of welding energies were used, between 0.6 and 1.1 kJ / mm, with the greatest energy limited to the thickness of the plates, which was 5 mm. When the microstructure formed in the region of the weld was analyzed, the quantification of ferrite in the zone affected by the heat showed uniformity in the samples, independent of the welding energy. However, the amount of ferrite in the weld metal decreased as the energy increased. The precipitation of chromium nitrides was observed in the intermetallic was associated with grain boundaries α / γ, inside some ferrite grains, close to regions with secondary intragranular austenite. The Vickers microhardness profiles showed no value above 300 HV, and no behavior differed according to the indentation area. The corrosion resistance did not change considerably, the base metal and the regions of the weld in the four conditions behaved very similarly. Ferric chloride immersion assays, following ASTM G48, allowed to observe the formation of pites, but the amount and density thereof can not be associated with a specific weld region or weld energy variation. The values of electrochemical parameters, OCP, ECORR, and EPIT, after the potentiodynamic polarization tests according to ASTM G5, showed little variation, showing a similar corrosion behavior for the base metal and the solder metals of the four Different welding energy conditions employed.

Les plasmas de type MIG-MAG n'étaient pas, jusqu'à présent, examinés en détail et exploités en laboratoire. En raison des applications techniques de ce type d'arc électrique, la plupart des expériences et des calculs théoriques se limitaient à l'étude des processus provenant des régions des électrodes. Des l'année 1948, au cours de laquelle les premiers brevets ont été déposés pour des arcs sous argon, les procédés de soudage MIG-MAG ont été exploités avec succès comme une des plus populaires méthodes d'assemblage de métaux. Et pourtant, malgré plus de cinquante ans d'histoire et de développement de cette méthode, la plupart des phénomènes fondamentaux qui y prennent naissance, n'ont pas trouvé d'explications. En 1953 Lubawski et Nowosilow ont présenté, pour la première fois, un arc avec une électrode fusible fonctionnant sous protection de dioxyde de carbone. On peut admettre, que à partir de ce moment, on a cherché à savoir de quelle manière le type du gaz appliqué influait sur le transfert du métal dans l'arc. En particulier, il s'agissait de déterminer comment des différences de propriétés physiques du plasma pouvaient intervenir sur les procédés intervenants dans la région de l'électrode supérieure, et pourquoi dans les mélanges gazeux riches en dioxyde de carbone on ne pouvait pas obtenir un régime de fonctionnement d'arc de type pulvérisation axiale ? Malheureusement, toutes les tentatives pour répondre à ces questions, par exemple un postulat selon lequel une modification de la distribution du courant dans l'extrémité d'électrode provoquerait une constriction de l'arc et une inversion de la force de Lorentz [83], restent toujours et uniquement seulement des hypothèses. Les travaux présentés dans cette thèse avaient pour but de comprendre l'influence du gaz utilisé sur le transfert du métal dans l'arc, et plus spécifiquement pourquoi une augmentation de la proportion de dioxyde de carbone dans le mélange gazeux provoquait un changement de son régime de fonctionnement. Les mesures réalisées ont toutes été financées par Air Liquide Welding, dans le but d'améliorer le procédé. Un motif supplémentaire de mener des recherches sur l'arc MIG-MAG, est la quasi-absence de données expérimentales concernant les distributions de température et de densité électronique dans ce type de plasma. Les données disponibles dans la littérature sont généralement le fruit de simulation numériques sans réelle validation expérimentale. Ainsi, par exemple, les valeurs de température présentées par Haidar semblent trop élevées pour un plasma dominé par les vapeurs métalliques. Le caractère particulier de l'arc de soudage, dont le spectre d'émission consiste en de nombreuses raies spectrales fortement élargies par effet Stark, a également permis de mesurer, parfois pour la première fois, les paramètres Stark des raies d'éléments métalliques. Une telle possibilité est très intéressante, car pour déterminer les élargissement et déplacement Stark de raies métalliques, il est nécessaire d'introduire les vapeurs de ce métal dans la région de décharge. En général, dans le cas des plasmas utilisés en laboratoire, cela n'est pas simple et induit de gros problèmes de demixing difficiles à résoudre, comme le montre la relativement faible quantité de données expérimentales disponibles jusqu'à présent. Ce sont pourtant des données essentielles pour la connaissance des milieux plasmagènes, notamment ceux étudiés en astrophysique.

Zugl.: Dresden, Techn. Univ., Diss., 2009