To see the other types of publications on this topic, follow the link: Cold metal transfer welding.
Dissertations / Theses on the topic 'Cold metal transfer welding'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 33 dissertations / theses for your research on the topic 'Cold metal transfer welding.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Magowan, Stephen. "Effects of cold metal transfer welding on properties of ferritic stainless steel." Thesis, Sheffield Hallam University, 2017. http://shura.shu.ac.uk/17304/.
Full textAbstract:
Stainless steels are a classification of materials that have been available for over 100 years and over that time manufacturers have created variations on chemical composition and manufacturing route, to create materials that meet specific criteria set by the consumer. One type of stainless steel, ferritic, is restricted in applications as a result of a reduction in properties, namely toughness, when it is welded as a result of grain coarsening in the heat affected zone. Welding equipment manufacturers are constantly incorporating new technologies and capabilities into welding equipment, to make welding easier and create better welds, which then gives that manufacturer a competitive advantage. Cold Metal Transfer (CMT) welding is one such innovation and is claimed by the manufacturer to be a lower heat input process. This research project examines the effects of this lower heat welding process, on the joining of ferritic stainless steels to determine if CMT can reduce the detrimental effects, seen in this material, through welding. The research examines the mechanical and metallurgical effects of using the Cold Metal Transfer (CMT) welding process to weld various grades of ferritic stainless steel including, EN1.4016, EN1.4509, EN1.4521 and EN1.4003 and compares them to welds created using a standard Gas Metal Arc Welding (GMAW) technique, with comparisons made using tensile testing, hardness testing, impact testing, fatigue testing and microstructural characterisation. Experimental results show that grades such as EN1.4016 and EN1.4003 are more sensitive to the welding process due to a phase change to martensite present within the heat affected zone. Work has been conducted to determine the temperature at which ferrite transforms to austenite, prior to transformation to martensite under non equilibrium cooling. Some of the findings from this work included; Fatigue testing and microstructural characterisation has shown a benefit in properties for using CMT over the conventional GMAW process for the EN1.4003 material. A relationship has also been proposed which examines the effect of the percentage of fusion zone defects on the fatigue life of the welded joints. Overall it was found that there was variation in the voltage and current by 1.9 Volts and 15 Amps respectively through a 400mm weld. The ALC settings from -30% to +30% affected the net heat input by 6J/mm NDT techniques utilised in the study were ineffective at detecting the lack of side wall fusion evident in some of the welds.
2
Daniels, Thomas W. "APPLICABILITY OF COLD METAL TRANSFER FOR REPAIR OF DISSIMILAR METAL WELDS IN STAINLESS STEEL PIPING IN NUCLEAR POWER PLANTS." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429873704.
Full text
3
Benoit, Alexandre. "Développement du soudage MIG CMT pour la réparation de pièces aéronautiques. Application aux pièces en alliage base aluminium 6061." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112308/document.
Full textAbstract:
Cette étude répond à une demande industrielle de réparation d’une pièce aéronautique en alliage d’aluminium 6061 à l’aide d’un procédé de soudage à l’arc. La première partie est consacrée à la comparaison des procédés Metal Inert Gas (MIG), MIG pulsé, Tungsten Inert Gas et MIG Cold Metal transfer (CMT). C’est ce dernier procédé qui a été sélectionné pour ses aptitudes particulières, comme son bon contrôle des paramètres et le faible endommagement produit dans le métal de base. Puis, deux métaux d’apport ont été testés – les alliages 5356 et 6061 – avec deux stratégies de réparation : le soudage et le rechargement. Les résultats d’essais mécaniques ont démontré que le rechargement avec l’aluminium 5356 est l’option la plus adaptée pour cette application. Les essais sur pièce réelle ont prouvé la pertinence de cette approche.La zone affectée thermiquement générée, dans l’alliage 6061, par les procédés de soudage à l’arc a également été caractérisée. Il a été mis en évidence une variation de la microstructure associée aux changements de propriétés mécaniques de cette zone. Enfin, les essais exploratoires de soudage homogène à l’arc, c’est-à-dire, avec le métal d’apport en 6061, ont prouvé qu’il était possible, dans certaines conditions, de souder sans générer de fissuration, bien que, cet aluminium soit réputé comme étant insoudable de cette manièreThis study responds to an industrial demand of repair using an arc welding process. It concerns an aeronautical piece made in 6061 aluminium alloy. The first part of the study is devoted to the comparison of processes Metal Inert Gas (MIG), pulsed MIG, Tungsten Inert Gas and MIG Cold Metal Transfer (CMT). It is the latter process that was selected for its special abilities, such as its good control of parameters and the low damaging produced in the base metal. Then, two filler alloys were tested – 5356 and 6061 aluminium alloys– with two repairing strategies : welding and building up. The results of mechanical tests showed that building up with aluminum 5356 is most suitable option for this application. The trials on the real piece showed the relevance of this approach.The heat affected zone generated by the arc welding process in the 6061 base metal was also characterized. It was shown a varaition of microstructure associated with the change of mechanical properties in this zone. Finally, exploratory trials of homogeneous arc welding, i.e., with the 6061 filler alloy showed that it was possible, with certain conditions, to weld without generating weld cracking, although, this aluminium is deemed unweldable by this way
4
Martins, Meco Sonia Andreia. "Joining of steel to aluminium alloys for advanced structural applications." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/10288.
Full textAbstract:
When joining steel to aluminium there is a reaction between iron and aluminium which results in the formation of brittle intermetallic compounds (IMC). These compounds are usually the reason for the poor mechanical strength of the dissimilar metallic joints. The research on dissimilar metal joining is vast but is mainly focused on the automotive industry and therefore, the material in use is very thin, usually less than 1 mm. For materials with thicker sections the present solution is a transition joint made by explosion welding which permits joining of steel to aluminium and avoids the formation of IMCs. However, this solution brings additional costs and extra processing time to join the materials. The main goals of this project are to understand the mechanism of formation of the IMCs, control the formation of the IMCs, and understand their effects on the mechanical properties of the dissimilar Fe-Al joints during laser welding. Laser welding permits accurate and precise control of the welding thermal cycle and thereby the underpinning mechanism of IMC formation can be easily understood along with the factors which control the strength of the joints. The further goal of this project is to find an appropriate interlayer to restrict the Fe-Al reaction. The first stage of the work was focused on the formation and growth of the Fe-Al IMCs during laser welding. The understanding of how the processing conditions affect the IMC growth provides an opportunity to act and avoid its formation and thereby, to optimize the strength of the dissimilar metal joints. The results showed that even with a negligible amount of energy it was not possible to prevent the IMC formation which was composed of both Fe2Al5 and FeAl3 phases. The IMC growth increases exponentially with the applied specific point energy. However, for higher power densities the growth is more accentuated. The strength of the Fe-Al lap-joints was found to be not only dependent on the IMC layer thickness but also on the bonding area. In order to obtain sound joints it is necessary to achieve a balance between these two factors. The thermal model developed for the laser welding process in this joint configuration showed that for the same level of energy it is more efficient to use higher power densities than longer interaction iv times. Even though a thicker IMC layer is formed under this condition due to higher temperature there is also more melting of aluminium which creates a larger bonding area between the steel and the aluminium. The joint strength is thus improved ... [cont.].
5
O'Brien, Evan Daniel. "Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389.
Full text
6
Tvrdoň, Radek. "3D tisk kovů robotem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443161.
Full textAbstract:
The diploma thesis presents an overview of additive production technologies and a summary of technologies used for 3D metal printing using a robot. All of them are generally described and at the same time assigned to their specific commercial use, or the academic research that deals with them. The work examines the suitability of the material EN ISO 14341-A: G 3Si1 for 3D printing, for which a modification of the Col Metal Transfer technology, Cycle Step is used. The experimental printout of the sample is evaluated on the basis of surface and mechanical tests. Capillary test, examination of microstructure a macrostructure, tensile test and microhardness test. All of them were satisfactory and the suitability of the welding wire for 3D printing was confirmed by the given technology.
7
Sequeira, Almeida P. M. "Process control and development in wire and arc additive manufacturing." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7845.
Full textAbstract:
This thesis describes advancements in the modelling, optimisation, process control and mechanical performance of novel high deposition rate gas metal arc welding processes for large scale additive manufacturing applications. One of the main objectives of this study was to develop fundamental understanding of the mechanisms involved during processing with particular focus on single layer welds made of carbon steel using both pulsed-current gas metal arc welding and cold metal transfer processes. The effects of interactions between critical welding process variables and weld bead and plate fusion characteristics are studied for single and multi-layers. It was shown that several bead and plate fusion characteristics are strongly affected by the contact tip to work distance, TRIM, wire feed speed, wire feed speed to travel speed ratio, and wire diameter in pulsed-current gas metal arc welding. The arc-length control, dynamic correction and the contact tip to work distance are shown to strongly influence the weld bead geometry in the cold metal transfer process. This fundamental knowledge was essential to ensure the successful development of predictive interaction models capable of determining the weld bead geometry from the welding process parameters. The models were developed using the least-squares analysis and multiple linear regression method. The gas tungsten constricted arc welding process was utilised for the first time for out-of-chamber fabrication of a large scale and high-quality Ti-6Al-4V component. The main focus was, however, in the use of the cold metal transfer process for improving out-of-chamber deposition of Ti-6Al-4V at much higher deposition rates. The effect of the cold metal transfer process on the grain refinement features in the fusion zone of single layer welds under different torch gas shielding conditions was investigated. It was shown that significant grain refinement occurs with increasing helium content. The morphological features and static mechanical performance of the resulting multi-layered Ti-6Al-4V walls were also examined and compared with those in gas tungsten constricted arc welding. The results show that a considerable improvement in static tensile properties is obtained in both testing directions with cold metal transfer over gas tungsten constricted arc welding. It was suggested that this improvement in the mechanical behaviour could be due to the formation of more fine-grained structures,which are therefore more isotropic. The average ultimate tensile strength and yield strength of the as-deposited Ti-6Al-4V material processed via cold metal transfer meet the minima specification values recommended for most Ti-6Al-4V products. Neutron diffraction technique was used to establish the effect of repeated thermo-mechanical cycling on the generation, evolution and distribution of residual stresses during wire and arc additive manufacturing. The results show a significant redistribution of longitudinal residual stresses along both the substrate and multi-bead with repeated deposition. However, a nearly complete relaxation occurs along the built, once the base plate constraint is removed.
8
Kim, Yong-Seog. "Metal transfer in gas metal arc welding." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14199.
Full text
9
Wang, Ge. "NUMERICAL ANALYSIS OF METAL TRANSFER IN GAS METAL ARC WELDING." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/538.
Full textAbstract:
In gas metal arc welding (GMAW), metal transfer plays a crucial role in determining the quality of the resultant weld. In the present dissertation, a numerical model with advanced computational fluid dynamics (CFD) techniques has been developed first in order to provide better numerical results. It includes a two-step projection method for solving the incompressible fluid flow; a volume of fluid (VOF) method for capturing free surface; and a continuum surface force (CSF) model for calculating surface tension. The Gauss-type current density distribution is assumed as the boundary condition for the calculation of the electromagnetic force. The droplet profiles, electric potential and velocity distributions within the droplet are calculated and presented for different metal transfer modes. The analysis is conducted to find the most dominant effects influencing the metal transfer behavior. Comparisons between calculated results and experimental results for metal transfer under constant current are presented and show good agreement. Then, our numerical model is used to study a proposed modified pulsed current gas metal arc welding. This novel modified pulsed current GMAW is introduced to improve the robustness of the welding process in achieving a specific type of desirable and repeatable metal transfer mode, i.e., one drop per pulse (ODPP) mode. This new technology uses a peak current lower than the transition current to prevent accidental detachment and takes advantage of the downward momentum of the droplet oscillation to enhance the detachment. The calculations are conducted to demonstrate the effectiveness of the proposed method in achieving the desired metal transfer process in comparison with conventional pulsed current GMAW. Also, the critical conditions for effective utilization of this proposed method are identified by the numerical simulation. The welding operational parameters and their ranges are also calculated and the calculated results further demonstrate the robustness of this new GMAW technique in achieving high quality welding.
10
Jönsson, Pär Göran. "Arc parameters and metal transfer in gas metal arc welding." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12470.
Full text
11
ALLVAR, MARIE. "MIG/MAG brazing with Cold Metal Transfer." Thesis, KTH, Maskinkonstruktion (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148077.
Full textAbstract:
In the automotive industry a commonly used material is thin steel sheets coated with a thin layer of zinc for corrosion resistance purposes. Welding of this material, with the high temperatures involved, causes problems with zinc burn-off leading to reduced corrosion resistance. The zinc evaporation also causes arc disturbances leading to spatter formation, pores and difficulties achieving good visual weld quality. The joints are in many cases visible or semi-visible (e.g. visible after opening a door) and “A-grade” quality is demanded, meaning no visible discontinuities are allowed. It also implies a smooth and generally appealing appearance of the joint.An alternative to welding is brazing, and laser brazing meets the requirements but the process is associated with high costs. In the national project “LEX-B”, funded by Vinnova, the possibilities of using arc brazing, in particular one MIG/MAG brazing and two TIG brazing processes, for some automotive applications are investigated. This master thesis is connected to the first part of the project and aims at compiling data for making a selection of the most promising process to investigate and optimise further. LEX-B is conducted in cooperation between Swerea KIMAB, Volvo Trucks, Scania CV and University West. The joint of interest is a lap joint between bottom and upper sheets of 1.2 mm and 0.8 mm respectively that represents a joint on the side of a truck cabin. The requirements are visual A-grade quality and tensile shear strength of 300 MPa.In the project the MIG/MAG process Cold Metal Transfer (CMT) was compared to the TIG processes forceTIG and Plasmatron. CMT was experimentally investigated while the results for the other two processes were obtained partly from a previous study and partly from Volvo Trucks where tests were performed simultaneously. A system for measuring data for the process was developed, test specimens were brazed and examined visually and mechanical destructive testing was performed to ensure the tensile shear strength. Parameter studies were done for further process optimisation.Inom fordonsindustrin är ett ofta använt material stål i tunna ark belagda med zink p.g.a. zinkets korrossionsskyddande egenskaper. Vid svetsning av detta material uppstår problem med zink som förångas vilket leder till minskad korrosionsbeständighet. Förångningen av zink orsakar också störningar av ljusbågen vilket leder till sprut, porer och svårighet att uppnå god visuell svetskvalitet. Fogarna är i många fall synliga eller delvis synliga (t.ex. synlig efter att ha öppnat en dörr) och "A-kvalitet" efterfrågas, vilket innebär att inga synliga diskontinuiteter tillåts. Fogen ska upplevas jämn och tilltalande.Lödning är ett alternativ till svetsning, och laserlödning är en process som uppfyller kraven men är förknippad med höga kostnader. I det nationella projektet "LEX-B", som finansieras av Vinnova, undersöks möjligheterna att använda båglödning, specifikt en MIG/MAG-process och två TIG-processer, för dessa applikationer. Detta examensarbete är anslutet till den första delen av projektet och syftar till ta fram underlag för att välja den mest lovande av dessa processer för vidare utredning och optimering. LEX-B sker i samarbete mellan Swerea KIMAB, Volvo Lastvagnar, Scania CV och Högskolan Väst. Den undersökta fogen är en överlappsfog mellan en undre plåt med 1,2 mm tjocklek och en övre plåt med 0,8 mm tjocklek. Detta representerar en fog på sidan av en lastbilshytt. Kraven är visuell A-kvalitet och en drag-skjuvhållfasthet av 300 MPa.I projektet jämfördes MIG/MAG-processen Cold Metal Transfer (CMT) med TIG-processerna forceTIG och Plasmatron. CMT testades experimentellt medan resultaten för de övriga två processerna erhölls dels från tidigare tester och dels från Volvo Lastvagnar där tester utfördes parallellt. Ett mätsystem for att dokumentera processdata utvecklades och de framställda lödfogarna undersöktes visuellt och med mekanisk förstörande provning för att säkerställa drag-skjuvhållfastheten. Parameterstudier gjordes för vidare optimering av processen.
12
Sazerat, Marjolaine. "Fabrication additive arc-fil (WAAM) pour la réparation de composants aéronautiques en Waspaloy : caractérisation microstructurale, mécanique et vieillissement métallurgique." Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2024. http://www.theses.fr/2024ESMA0024.
Full textAbstract:
Le procédé de soudage Cold Metal Transfer (CMT) est envisagé comme un moyen de réparation additive pour les pièces de grandes dimensions. Cette technologie offre un taux de dépôt élevé avec un apport de chaleur réduit en raison du transfert de matière en régime de court-circuit. Son utilisation permettrait de réduire considérablement les temps d’opération liés à la maintenance, réparation et révision (MRO). Le Waspaloy, superalliage base Ni polycristallin durci par précipitation γ', est communément utilisé dans les parties chaudes des turboréacteurs. Il est, toutefois, considéré marginalement soudable en raison de sa forte teneur en aluminium et en titane. Cette particularité mène à un manque de données dans la littérature scientifique sur ce couple matériau/procédé. Ces travaux de thèse, menés à l’Institut P’ et en collaboration avec le site de MRO de Safran Aircraft Engines (Châtellerault), ont été dédiés à l’étude du Waspaloy CMT. Le premier axe d’analyse a été la caractérisation, à la fois microstructurale et mécanique, du matériau à l’état brut de fabrication. La structure granulaire et dendritique est présentée, de même que la précipitation γ' hétérogène entre les cœurs de dendrite et les espaces interdendritiques. La ségrégation chimique qui en est responsable est mise en évidence, et les propriétés mécaniques monotones, en traction et en fluage jusqu’à 850 °C, sont évaluées. Ensuite, avec l’intention d’optimiser la microstructure hétérogène par un traitement thermique post-soudage différent de celui préconisé pour le matériau forgé, un deuxième axe s’est dégagé autour de la stabilité thermique du Waspaloy CMT. Le grossissement des précipités γ' et les cinétiques de vieillissement sont approchés par la théorie de Lifshitz-Slyozov-Wagner. La formation de phases secondaires est observée, avec l’identification de carbures M23C6 par leur nature chimique et cristalline. Des diagrammes temps-température-transformation expérimentaux sont établis. La question de l’équilibre thermodynamique est abordée par l’application d’un revenu long, et numériquement par des simulations Thermo-Calc®. L’effet du traitement thermique de revenu sur le comportement en traction et en fluage est étudié, en comparaison avec le Waspaloy CMT brut de fabrication et le matériau forgé de référence. Les liens entre les propriétés obtenues et les évolutions microstructurales sont mis en lumière. L’investigation de la tenue mécanique de l’interface entre le substrat forgé et le rechargement CMT s’est également imposéeCold Metal Transfer (CMT), a wire arc welding process, is being contemplated as a means of additive repair for large aeronautical components. This technology offers a high deposition rate with reduced heat input due to short-circuit material transfer. Its use would considerably reduce maintenance, repair and overhaul (MRO) times. Waspaloy, a γ' precipitation-hardened polycrystalline Ni-based superalloy, is commonly used in the hot sections of jet engines. It is, however, considered marginally weldable due to its high aluminum and titanium content. This particularity leads to a lack of data in the scientific literature on this material/process pair. This thesis work, carried out at the Institut P' and in collaboration with the MRO center of Safran Aircraft Engines (Châtellerault), was dedicated to the study of CMT Waspaloy. The first axis of analysis was the characterization, both microstructural and mechanical, of the material in its as-built state. The granular and dendritic structure is presented, as is the heterogeneous γ' precipitation between dendrite cores and interdendritic spaces. The chemical segregation responsible for this is highlighted, and the monotonic mechanical properties up to 850°C, through both tensile and creep testing, are evaluated. Then, with the intention of optimizing the out-of-equilibrium microstructure by a post-weld heat treatment different from that recommended for the wrought material, a second focus emerged around the thermal stability of CMT Waspaloy. γ' precipitation coarsening and aging kinetics are approximated using the Lifshitz-Slyozov-Wagner theory. The formation of secondary phases is observed, with the identification of M23C6 carbides by their chemical and crystalline nature. Experimental time-temperature-transformation diagrams are established. The question of thermodynamic equilibrium is addressed through the application of a long ageing heat treatment, and numerically through Thermo-Calc® simulations. The effect of ageing on tensile and creep behavior is investigated, in comparison with as-built CMT Waspaloy and the reference wrought material. The links between the resulting properties and microstructural evolutions are highlighted. The mechanical strength of the interface between the wrought substrate and the CMT refurbishment is also investigated
13
Ludick, Mark. "Experimental sensitivity analysis of welding parameters during transition from globular to spray metal transfer in gas metal arc welding." Thesis, Peninsula Technikon, 2001. http://hdl.handle.net/20.500.11838/1269.
Full textAbstract:
Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, Cape Town, 2001Since the discovery of arc welding at the beginning ofthe century, metal transfer has been a topic ofresearch interest. Metal transfer can, in fact be related to weld quality, because it affects the arc stability. Furthermore, it determines the weld spatter, penetration, deposition rate and welding position. Gas Metal Arc Welding (also known as Metal Inert Gas- or MIG welding) is the most co=on method for arc welding steels and aluminurn alloys. Approximately 40% of the production welding in the country is accomplished by this process in which the thermal phenomena and melting ofthe solid electrode are coupled to the plasma arc and the weld pool. Thus the therrno- fluid behaviour of the electrode and detaching drops can have significant effects on the subsequent weld quality and production rate. The knowledge of how metal transfer affects this arc welding process is important for welding control and process automation, as well as in the development of improved welding consumables. Gas metal arc welding has a distinct feature, indicated by the results of Lesnewich [24], [23], that for most gases, there is a discrete metal droplet formation change between low and high current operations. Naturally the droplet size will have a significant influence on the properties ofthe welds. In globular transfer which occurs at low current, the welding electrode melts and produces large droplets (usually larger in diameter than the electrode wire diameter). This mode of transfer is associated with high spatter levels and thus undesirable in terms of welding economics. An increase in welding current will, for most welding! shielding gases, produce metal transfer with smaller droplets, which is termed spray transfer. This mode oftransfer is associated with high voltage and amperage settings, thus producing high deposition rates limited to the flaUhorizontal position.
14
Dean, Gary. "Optimization of metal transfer and fusion using current control in dip transfer GMAW." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041029.140918/index.html.
Full text
15
Liu, Xiaopei. "Dual Bypass Gas Metal Arc Welding Process and Control." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/664.
Full textAbstract:
GMAW (Gas Metal Arc Welding) is one of the most important arc welding processes being adopted in modern manufacturing industry due to its advantages in productivity, energy efficiency and automation. By monitoring and improving some of the important properties of GMAW such as production rate, metal transfer and base metal heat input, researchers could bring the process efficiency and stability to a new level. In recent years, some innovative modifications of GMAW such as Twins, Tandem and laser-MIG hybrid welding have been adopted into many industrial applications for better productivity.
In this dissertation, a novel GMAW called DB-GMAW (Dual Bypass Gas Metal Arc Welding) using two GTAW torches and one GMAW torch to construct a welding system, is proposed and developed. In DB-GMAW, two GTAW torches perform the bypass system which decouples the total welding current into base metal current and bypass current after the melt down of filler wire. Compared to conventional GMAW, DB-GMAW has many advantages in droplet formation, base metal heat input and penetration achievement due to its unique characteristics in welding arc and current flow. In the first place of the research, experimental system of DB-GMAW is constructed. Then, sufficient experiments under different parameters are performed to provide us a good understanding of the behaviors and characteristics of this novel GMAW process. Observation about metal transfer formation and base metal heat input is studied to verify its theoretical analysis. Full penetration of work piece via DB-GMAW is achieved based on a series of parameter testing experiments. Moreover, image processing techniques are applied to DB-GMAW to monitor the welding process and construct a feedback system for control.
Considering the importance of maintaining stable full penetration during many welding applications, a nonlinear model of DB-GMAW full penetration is developed in this dissertation. To do that, we use machine vision techniques to monitor the welding profile of the work piece. A control algorithm based on the nonlinear model using adaptive control technique is also designed. The achievement of this dissertation provides a fundamental knowledge of a novel welding process: DB-GMAW, and a good guidance for further studies about DBGMAW.
16
Li, Peigang. "Cold lap formation in Gas Metal Arc Welding of steel : An experimental study of micro-lack of fusion defects." Doctoral thesis, Högskolan Väst, Avd för maskinteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-5596.
Full textAbstract:
Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool. The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.
17
KOLI, YASHWANT. "MECHANICAL AND MICROSTRUCTURAL CHARACTERIZATION OF DISSIMILAR JOINT OBTAINED BY GMAW USING COLD METAL TRANSFER (CMT)." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18773.
Full textAbstract:
This research work focuses on a comparative study on weld bead geometries of three
different welding techniques: Cold Metal Transfer (CMT), Metal Inert Gas Pulse Synergic
(MIG P) and MIG Manual Standard (MIG M). Bead-on-plate tests were performed using
ER4043 (AlSi5%) as a filler material on the 3.18 mm thick plates of AA6061-T6. Current
(80 A, 100 A and 120 A) and welding speed (7.5, 10.5 and 13.5 mm/sec) were used as
input process parameters while shielding gas flow rate and contact tip to workpiece
distance (CTWD) were maintained constant as 15 l/min and 10mm respectively. The weld
beads processed by all the three techniques are compared by analysing the weld bead
geometry. Microstructural characterization is carried out using optical microscopy and
Field Emission Scanning Electron Microscope (FESEM). CMT has high dilution and
penetration with low heat input. Compared to MIG P and MIG M, CMT shows a drastic
reduction in residual stresses. Multi-response mathematical model is established for
prediction of weld bead geometry in CMT, MIG P and MIG M welding of AA6061-T6
using ER4043 (AlSi5%) as a filler material. Central composite face-centered design
(CCFCD) under response surface methodology (RSM) is employed to develop the design
matrix for conducting the experiments. The developed model is employed in finding the
optimal process parameters for good weld bead aesthetics. Current (I) and welding speed
(S) are opted as input process parameters for response output such as penetration, dilution
and heat input. This model is proficient to forecast the main effects and interactive effects
of two factor of the opted welding process parameters. Results show that higher current
values with low welding speed results in deeper penetration, high amount of dilution with
higher heat input and vice versa. With lower heat input, CMT has high dilution and
penetration with respect to MIG P and MIG M welding. The optimal process parameters
are 92.518A and 7.50mm/sec for CMT, 109.418A and 10.873mm/sec for MIG P,
110.847A and 11.527mm/sec for MIG M with 61.11%, 68.80% and 72.6% desirability,
respectively. Predicted output values generated from regression model equation obtained
from welding process parameters are very close and sometimes overlaid on actual output
that obviously demonstrates the suitability of the second order regression equations. A
vi
good amount of penetration and dilution with low heat input is required for better joint
efficiency.
The requirements projected by many industries for stronger, lighter, more efficient
and cost-effective combined alloys in the welding of two dissimilar materials or dissimilar
thickness. The current industry trend is the coalescence of various aluminium alloys of
varying thicknesses. CMT welding process was used for joining of AA6061-T6 and
AA6082-T6 using ER4043 filler wire and inspected the effect of different process
parameters on mechanical properties of welded butt joints. Current (I), welding speed or
travel speed (TS) and gas flow rate (Q) are the input welding process parameters that are
to be optimized. Different heat input is studied w.r.t welding speed, current and gas flow
rate. Heat inputs ranging from 100+, 200+ and 300+ J/mm is achieved at constant welding
speed of 9, 7 and 5 mm/sec respectively at variable currents and flow rates. Bead geometry
variables such as penetration (P), reinforcement (R) and contact angle (CA) are
distinguished at different heat inputs. Mechanical properties such as tensile test and
microhardness for different heat input were investigated. Microstructural characterization
of base metal (BM), fusion line (FL) and weld metal (WM) is carried out. High-Resolution
X-ray Diffraction (HR-XRD) technique based on cosα method is used for residual stress
measurements at different heat inputs. Tensile fractured surfaces were examined by
FESEM and energy-dispersive X-ray spectroscopy (EDX). Butt joints of various different
process parameters were fabricated with the help of full factorial CCFCD under RSM to
optimize the tensile properties, microhardness and residual stresses. Grey relation analysis
(GRA) with Principal component analysis (PCA) is incorporated with CCFCD for finding
out the optimal process parameter by considering multi-response parameters
simultaneously. ANOVA was executed to interpret the impact of process parameters on
the mechanical properties of the weldments. Results showed that the most dominant
process parameter was found to be the welding speed. The optimal process parameter
obtained via GRA-PCA technique is I3-TS1-Q1 (I - 100 A, TS - 5 mm/sec and Q - 14
L/min having heat input 352 J/mm) which produces 226 MPa of ultimate tensile strength,
12.6 % of elongation, 68.7 HV of microhardness and -152.3 MPa of compressive residual
vii
stress. Desirability of optimality level obtained through CCFCD was 65.99 % and
significantly improved to 97.07 % through GRA-PCA.
Nowadays, to enhance the structural efficiency, ultrasonic vibrations are combined
with other manufacturing processes such as welding. It gives considerable advantages in
terms of improved mechanical properties, adequate surface strength, improved material
flow and uniform grain growth etc. Ultrasonic assisted cold metal transfer (U-CMT)
welding is performed to fabricate the joints and improvements in mechanical properties
and microstructural modifications are studied. Non-destructive technique (NDT) such as
radiography technique (RT) is used to test weld consistency. Results revealed improved
weld bead geometry with the aid of ultrasonic vibrations for the same welding parameters.
The tensile strength and micro-hardness are enhanced. Samples with ultrasonic vibration
experiences grain refining as compared to without vibration samples. As compared with
CMT, U-CMT joints are rich in Al-Si eutectic structure. Al-Si structure is in globular form
with reduced porosity level.
18
Nevasmaa, P. (Pekka). "Predictive model for the prevention of weld metal hydrogen cracking in high-strength multipass welds." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514271815.
Full textAbstract:
Abstract
This thesis studies controlling factors that govern transverse hydrogen cracking in high-strength multipass weld metal (WM). The experiments were concerned with heavy-restraint Y- and U-Groove multipass cracking tests of shielded-metal arc (SMAW) and submerged-arc (SAW) weld metals. Results of tensile tests, hardness surveys, weld residual stress measurements and microstructural investigations are discussed. The analytical phase comprised numerical calculations for analysing the interactions between crack-controlling factors. The objectives were: (i) the assessment of WM hydrogen cracking risk by defining the Crack-No Crack boundary conditions in terms of 'safe line' description giving the desired lower-bound estimates, and (ii) to derive predictive equations capable of giving reliable estimates of the required preheat/interpass temperature T0/Ti for the avoidance of cracking.
Hydrogen cracking occurred predominantly in high strength weld metals of Rp0.2 ≈ 580-900 MPa. At intermediate strengths of Rp0.2 ≈ 500-550 MPa, cracking took place in the cases where the holding time from welding to NDT inspection was prolonged to 7 days. Low strength WMs of Rp0.2 ≤ 480 MPa did not exhibit cracking under any conditions examined. Cracking occurrence was, above all, governed by WM tensile strength, weld diffusible hydrogen and weld residual stresses amounting to the yield strength. The appearance of cracking vanished when transferring from 40 to 6 mm thick welds. The implications of the holding time were more significant than anticipated previously. A period of 16 hrs in accordance with SFS-EN 1011 appeared much too short for thick multipass welds. Interpass time and heat input showed no measurable effect on cracking sensitivity, hence being of secondary importance. Equations were derived to assess the weld critical hydrogen content Hcr corresponding to the Crack-No Crack conditions as a function of either weld metal Pcm, yield strength Rp0.2 or weld metal maximum hardness HV5(max). For the calculation of safe T0/Ti estimates, a formula incorporating: (i) WM strength as a linear function of either weld carbon equivalent CET or weld HV5(max), (ii) weld build-up thickness aw in the form of tanh expression and (iii) weld diffusible hydrogen HD in terms of a combined [ln / power law] expression was found descriptive.
19
McVicker, Nathaniel P. "Structural Weld Overlays for Mitigation of Primary Water Stress Corrosion in Nuclear Power Plants." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429879662.
Full text
20
Moselli, Andrea. "Sviluppo e validazione sistema di controllo di processo di saldatura meccanica a freddo applicato alla produzione di accumulatori di energia." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
La saldatura meccanica a freddo (CPW: cold pressure welding) risulta essere un argomento non molto studiato e dotato di una bibliografia piuttosto scarna in merito all’applicazione che questa tesi vuole sviluppare, ovvero la giunzione per sovrapposizione di connettori elettici di accumulatori di energia.
Lo studio qui riportato, prosegue lavori già svolti in precedenza mirati al raggiungimento del medesimo obiettivo.
Tuttavia, partendo da questi dati, il mio elaborato si propone di espandere le conoscenze in
merito a questa tecnologia e sondare la possibilità di poterla applicare realisticamente in ambito industriale dove finora non ha ancora avuto la possibilità di essere sfruttata a dovere, in favore della ben più studiata e applicata saldatura ad ultrasuoni (UMW: ultrasonic metal welding).
In particolare questo lavoro si può suddividere in due fasi ben distinte:
Nella prima parte si è ricercata la correlazione tra i parametri necessari all’applicazione in macchine automatiche, ovvero la resistenza di giunti saldati con tecnologia CPW e la riduzione di spessore degli stessi, con la prospettiva futura di poter correlare direttamente quest’ultima con la pressione che l’ha generata.
Nella seconda, dopo aver riscontrato una forte dipendenza tra i parametri oggetto di studio, si è potuto procedere a porre le basi per l’industrializzazione del processo, andando quindi a studiare la durata dei componenti e l’affidabilità degli stessi all’interno di una macchina progettata ad hoc per questa applicazione.
21
Querard, Vincent. "Réalisation de pièces aéronautiques de grandes dimensions par fabrication additive WAAM." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0001/document.
Full textAbstract:
Dans le domaine de la fabrication additive plusieurs technologies cohabitent et présentent des maturités et des applications différentes : le lit de poudre, la projection de poudre et le dépôt de fil pour ne citer que les principales. Nous avons étudié, dans le cadre de cette thèse, la réalisation de pièces de grandes dimensions du domaine aéronautique en alliage d’aluminium, par technologie WAAM (Wire Arc Additive Manufacturing) robotisée. Cette technologie repose sur l’utilisation un générateur de soudure à l'arc, d’un système de protection gazeuse et d’un système d'alimentation en métal d'apport sous forme de fil. Pour répondre à cette problématique, plusieurs voies de recherche ont été investiguées. La première traitait principalement de la génération de trajectoires : Plusieurs expérimentations ont permis de montrer l’intérêt et l’importance de la génération de trajectoires et notamment la maitrise de l’orientation outil pour la fabrication additive de pièces complexes en étudiant le respect de la géométrie souhaitée. La seconde concernait l’étude de la santé matière des pièces fabriquées. Des observations au niveau de la microstructure, mais aussi des caractéristiques mécaniques ont permis de mettre en évidence l’influence des paramètres opératoires sur la qualité de la matière déposée. Enfin, la réalisation de pièces fonctionnelles dans le cadre d’un projet financé par la DGA/DGAC et dont les partenaires étaient : STELIA, CONSTELLIUM, CT INGENIERIE et l’Ecole Centrale de Nantes, a permis de mettre en avant l’intérêt du procédé pour la fabrication de pièces aéronautiques. Un élément de structure aéronautique composé de raidisseurs a été fabriqué avec le procédé WAAM sur un substrat double courbure en alliage aluminium. Les difficultés accrues de réalisation ont pu être levées par l'emploi de la méthodologie développée dans le cadre de la thèseIn the field of additive manufacturing (AM), several processes are present and have different applications and levels of development: the main technologies are powder-bed based AM, powder projection and Wire Additive Manufacturing (WAM). We have studied, in this PhD work, the manufacturing of large scale components in aluminum alloy for aircraft industry with Wire Arc Additive Manufacturing (WAAM). This technology is based on a welding generator, a shielding gas protection and a feedstock (wire in this case). To solve this issue, several ways of research were investigated. The first one dealt with toolpath generation: several experiments have highlighted the importance of tool path generation and the tool orientation to manufacture complex parts and improve the part accuracy. The second one was about the validation of the material quality after deposit. Microstructural observations and mechanical tests have demonstrated the effect of process parameters on the deposit quality. Finally, in the context of a DGA/DGAC funded research project, whose partners were STELIA, CT INGENIERIE, CONSTELLIUM and l’Ecole Centrale de Nantes, the manufacturing of functional part in aluminum alloy has shown the interest of the process for aircraft industry. A structural component based on a double curvature geometry has been manufactured with WAAM. The methodologies developed in this PhD work have enabled us to solve the issues to manufacture that type of component
22
Rodrigues, Carlos Eduardo Aguiar Lima. "Avaliação cinemática e dinâmica da transferência metálica na soldagem mig/mag." Universidade Federal de Uberlândia, 2007. https://repositorio.ufu.br/handle/123456789/14676.
Full textAbstract:
Conselho Nacional de Desenvolvimento Científico e TecnológicoThe goal of this work is to improve the knowledge of the metal transfer in MIG/MAG welding and supply data to improve the elaboration of its models. In this intention, experiments were accomplished with steel (inverse polarity; Ar+5%O2 shield gas) and aluminum (inverse polarity, Ar shield gas) electrodes, with steel electrode and several shield gases (inverse polarity, Ar+5%O2+ of 0 to 25%He shield gases) and experiments with steel electrode in direct polarity (Ar+5%O2 shield gas). The flat position welds were filmed by a high-speed video camera using the shadowgraph technique. Kinematics and dynamics characteristics of metal transfers in those experiments were obtained experimentally (droplets arrival speed in the weld pool, in flight droplets average acceleration, effective quantity of movement), and the weld geometry, and compared whenever possible with experimental and numeric results available in literature. The results showed that the weld current influences the kinematics and dynamics characteristics of the drops in all of studied conditions, that the arc length influences the cinematic characteristics and dynamics in the welds with steel and aluminum electrodes, and in the steel welds with different shield gasses; that the shield gas doesn't exercise significant influence in the appraised characteristics, and that the current polarity only affects the cinematic characteristics and dynamics in globular transfer mode. Additionally, the welding current affects the weld penetration despite the use of approximately the same heat input, the arc length affect the steel and aluminum weld penetration and with different shield gasses, the shield gas didn't exercise influences in the values of the penetration but it altered the form of the weld and the current polarity didn't exercise influences the weld penetration, but just in width and reinforcement, being more slender the weld bead in direct polarity.
Com o intuito de aprofundar o conhecimento da transferência metálica em MIG/MAG goticular e fornecer dados para aprimorar a elaboração de modelos da mesma, foram realizados experimentos com eletrodos de aço (polaridade inversa, gás de proteção Ar+5%O2) e alumínio (polaridade inversa, gás de proteção Ar), experimentos com eletrodo de aço e vários gases de proteção (polaridade inversa, gases de proteção Ar+5%O2+de 0 a 25%He), e experimentos com eletrodo de aço em polaridade direta (gás de proteção Ar+5%O2). As soldas, em posição plana, foram filmadas em alta velocidade através da técnica da perfilografia. Determinou-se experimentalmente características da transferência metálica (diâmetro das gotas e sua freqüência de destacamento e o comprimento do arco elétrico), bem como as características cinemáticas e dinâmicas das transferências metálicas obtidas nesses experimentos (velocidade de chegada das gotas à poça de fusão; aceleração média das gotas durante a trajetória; quantidade de movimento efetiva das gotas) e a geometria dos cordões de solda, comparados sempre que possível a resultados experimentais e numéricos disponíveis na literatura. Os resultados mostraram que a corrente e o comprimento do arco influenciam as características cinemáticas e dinâmicas das gotas em todas as condições estudadas, que o gás de proteção não exerce influência significativa nas características avaliadas, que a polaridade do eletrodo só afeta as características cinemáticas e dinâmicas no modo de transferência globular e que a quantidade de movimento efetiva das gotas influencia claramente a penetração do cordão de solda apenas quando associada à mudança no modo de transferência de globular para goticular. Adicionalmente, a corrente de soldagem afetou a penetração das soldas, mesmo utilizando-se aproximadamente o mesmo calor imposto, o comprimento do arco afetou a penetração das soldas de aço e alumínio e com diferentes gases de proteção, o gás de proteção não exerceu influência nos valores da penetração, mas alterou a forma do cordão e a polaridade não exerceu influência na penetração da solda, mas apenas na sua largura e reforço, sendo mais esbelto o cordão de solda em polaridade direta.
Doutor em Engenharia Mecânica
23
Nell, Ryno Willem. "Development of a novel nitriding plant for the pressure vessel of the PBMR core unloading device / Ryno Willem Nell." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4227.
Full textAbstract:
The Pebble Bed Modular Reactor (PBMR) is one of the most technologically advanced developments in South Africa. In order to build a commercially viable demonstration power plant, all the specifically and uniquely designed equipment must first be qualified. All the prototype equipment is tested at the Helium Test Facility (HTF) at Pelindaba. One of the largest components that are tested is the Core Unloading Device (CUD).
The main function of the CUD is to unload fuel from the bottom of the reactor core to enable circulation of the fuel core. The CUD housing vessel forms part of the reactor pressure boundary. Pebble-directing valves and other moving machinery are installed inside its machined inner surface. It is essential that the interior surfaces of the CUD are case hardened to provide a corrosion- and wear-resistant layer. Cold welding between the moving metal parts and the machined surface must also be prevented. Nitriding is a case hardening process that adds a hardened wear- and corrosion-resistant layer that will also prevent cold welding of the moving parts in the helium atmosphere.
Only a few nitriding furnaces exist that can house a forging as large as the CUD of the PBMR. Commercial nitriding furnaces in South Africa are all too small and have limited flexibility in terms of the nitriding process. The nitriding of a vessel as large as the CUD has not yet been carried out commercially. The aim of this work was to design and develop a custom-made nitriding plant to perform the nitriding of the first PBMR/HTF CUD.
Proper process control is essential to ensure that the required nitrided case has been obtained. A new concept for a gas nitriding plant was developed using the nitrided vessel interior as the nitriding process chamber. Before the commencement of detail design, a laboratory test was performed on a scale model vessel to confirm concept feasibility. The design of the plant included the mechanical design of various components essential to the nitriding process. A special stirring fan with an extended length shaft was designed, taking whirling speed into account. Considerable research was performed on the high temperature use of the various components to ensure the safe operation of the plant at temperatures of up to 600°C. Nitriding requires the use of hazardous gases such as ammonia, oxygen and nitrogen. Hydrogen is produced as a by-product and therefore safety was the most important design parameter. Thermohydraulic analyses, i.e. heat transfer and pressure drop calculations in pipes, were also performed to ensure the successful process design of the nitriding plant.
The nitriding plant was subsequently constructed and operated to verify the correct design. A large amount of experimental and operating data was captured during the actual operation of the plant. This data was analysed and the thermohydraulic analyses were verified. Nitrided specimens were subjected to hardness and layer thickness tests.
The measured temperature of the protruding fan shaft was within the limits predicted by Finite Element Analysis (FEA) models. Graphs of gas flow rates and other operation data confirmed the inverse proportionality between ammonia supply flow rate and measured dissociation rate. The design and operation of the nitriding plant were successful as a nitride layer thickness of 400 μm and hardness of 1 200 Vickers hardness (VHN) was achieved.
This research proves that a large pressure vessel can successfully be nitrided using the vessel interior as a process chamber.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.
24
KARLSSON, DANIEL. "Jämförelse mellan vågformsstyrda processer och konventionell spraybåge vid användning av solidtråd : Möjligheter att uppnå av Volvo CE ställda krav och potentiella vinster." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-295500.
Full textAbstract:
Detta arbete har genomförts vid Volvo Construction Equipment i Braås. I nuläget används konventionell spraybågssvetsning med metallpulverfylld rörtråd i produktionen. Ett alternativ som övervägs är att byta till solidtråd. Huvudsyftet med detta arbete har varit att utreda huruvida några utvalda processer med 1.2 mm solidtråd är kapabla att producera ensträngs kälsvetsar som uppfyller av Volvo CE ställda krav: - Minst 3 mm i-mått. - Teoretiskt a-mått mellan 4 och 5.5 mm. - Svetsklass VD enligt Volvo standard STD 181-0004. - Kompatibel med fogföljning via ljusbåge. - Ingen spalt mellan plåtarna tillåten. Arbetet inleddes med en litteraturstudie för att framförallt beskriva svetsparametrars inverkan på svetsens inträngningsprofil och geometri. Ett stort antal svetsförsök utfördes med konventionell spraybåge samt de vågformsstyrda processerna Fronius PMC och Lincoln Electrics RapidArc. Försöken genomfördes i PA och i PB läge. I PB läget orienterades förbandet dels med gränsytan mellan plåtarna horisontellt och dels vertikalt. Flertalet av försöken genomfördes med svetstraktor. Kompletterande försök genomfördes med svetsrobot. Inträngning och kvalité bedömdes framförallt genom makroprov och syning, men också genom lasermätning. Vid inledande faktorförsök med RapidArc, PMC och konventionell spraybågsprocess användes trådmatningshastighet 13 och 15 m/min i kombination med svetshastighet 55 och 65 cm/min. Försöken visade att i PB läge med horisontell gränsyta kan 3 mm i-mått uppnås med trådmatningshastigheten 13 m/min och svetshastigheten 55 cm/min. Under avslutande svetsförsök med PMC i PB läge med gränsytan vertikalt vid 60 cm/min svetshastighet, pendling och 14.5-15.5 m/min trådmatningshastighet erhölls i-mått avsevärt överstigande 3 mm. Vid svetsförsök i PB läge med solidtråd uppnåddes kraven på 3 mm i-mått och mjuka fattningskanter med ökad svetshastighet jämfört med ett typiskt produktionsfall. I PA läge erhölls mindre skillnad gentemot ett produktionsfall. Genom ytterligare optimering av svetsprocesserna är det dock inte orimligt att svetshastigheterna kan ökas utan försämrade i-mått och fattningskanter. Möjlig kostnadsreducering för tillsatsmaterialet vid övergång till solidtråd är 30-50% beroende på att solidtråden är billigare än metallpulverfylld rörtråd. Ytterligare kostnadsreducering kan erhållas genom förbrukning av mindre mängd tillsatsmaterial. Vid genomförde svetsförsök har mindre mängd tillsatsmaterial tillförts jämfört med typiska produktionsfall. Både den konventionella spraybågsprocessen och de vågformsstyrda processerna är kapabla att producera de eftersträvade svetsarna med solidtråd. Här måste dock ett ”varnade finger” höjas; vid svetsningen krävs god kontroll av elektrodvinklarna och elektrodens position relativt fogens rot, annars erhålls betydligt sämre resultat.This thesis has been performed at Volvo Construction Equipment in Braås. Currently, conventional MAG spray transfer with metal cored wire is used in the production. The company is now considering switching from metal cored wire to solid wire. The main purpose of this thesis has been to investigate whether a few selected processes used with 1.2 mm solid wire are capable of producing single pass fillet welds that conform to the following requirements set by Volvo CE: - Minimum i-dimension 3 mm. - Theoretical throat thickness between 4 and 5.5 mm. - Weld class VD according to Volvo standard STD 181-0004. - Compatible with Through Arc Seam Tracking. - No gap between the plates is allowed. A literature study was performed primarily in order to describe the influence of weld parameters on the weld and penetration profile. A large number of weld trials were performed with conventional spray transfer and the two waveform controlled processes Fronius PMC and Lincoln Electrics RapidArc. The weld trials were performed in the weld positions PA and PB. For PB the joint root was orientated both horizontally and vertically. For the majority of trials a weld tractor was used. Complementary trials were performed by a robot. Weld testing consisted primarily of macro etch testing and visual inspection but also laser scanning. The initial trials with RapidArc, PMC and conventional spray transfer were performed with the wire feed speeds 13 and 15 m/min in combination with the travel speeds 55 and 65 cm/min. The trials showed that when using weld position PB with a horizontal joint root, 3 mm i-dimension can be achieved by using wire feed speed 13 m/min and travel speed 55 cm/min. Final trials with PMC were performed in weld position PB with a vertical joint root using wire feed speeds 14.5-15.5 m/min, a travel speed of 60 cm/min and weaving resulting in i-dimensions much greater than 3 mm being achieved. Using solid wire in weld position PB, welds with 3 mm i-dimension and good wetting of the toes were produced with increased travel speed compared to a typical production case. However, in weld position PA less difference was obtained compared to a typical production case. By further optimizing the weld processes it is not unlikely that the travel speeds can be increased while maintaining the i-dimension and good wetting of the toes. A possible cost reduction for the filler material is 30-50% because solid wire is cheaper than metal cored wire. Using less filler material will result in additional cost reductions. During performed weld trials less filler material was used compared to current production scenarios. Both the conventional spray transfer process and the waveform controlled processes are capable of producing the desired welds with solid wire. However, a cautionary tale must be told: when welding, good control of the electrode angles and position relative to the joint root is needed otherwise much worse results will be obtained.
25
GUPTA, PRASANNA. "OPTIMIZATION OF WELDING PARAMETERS IN COLD METAL TRANSFER WELDING OF STAINLESS STEELS." Thesis, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18169.
Full textAbstract:
For better efficiency, manufacturers these days are more interested in using very light weight
materials that not only reduces the overall weight of the structure but also enables the use of latest
technology. Due to their immense strength, ease in fabrication, Austenitic Stainless Steel grades
find their application in wide range of manufacturing industries such as automotive, medical,
construction, aerospace. Various problems such as burn through, distortions, spatter and other
defects were reported when thin austenitic stainless sheets were welded using conventional arc
welding process because of their high heat input. Cold Metal transfer welding is a modern era
welding technology for joining of thin sheets as optimum penetration at low heat input and spatter
free weld can be obtained. In this research work SS202 samples of thickness 1.58mm have been
welded using SS308 filler wire by CMT welding process. Three different levels of Current (80A,
100A, 120A), Welding speed (3mm/sec, 4mm/sec, 5mm/sec), and Pulse dynamic correction Factor
(-10, 0, +10) were set as input process parameter. The experiments have been carried out at most
optimum parametric combination obtained from Taguchi L9 design of experiment array. The
superiority of weld was estimated in the form of three mechanical properties Yield Strength (YS),
Ultimate Tensile Strength (UTS), and Percentage Elongation wherein highest value obtained for
the three were 379 MPa, 871 MPa, and 65.9% respectively. The experimental data obtained have
been optimized by Taguchi’s S/N ratio larger the better criteria. Further, Ultrasonic Assisted CMT
Welding have been carried out on same SS202 samples of 1.58mm thickness under same process
parameter and result have been compared with responses obtained for CMT welded samples
without Ultrasonic vibrations.
26
RAJ, PRATEEK. "STUDY OF MECHANICAL CHARACTERISTICS OF WELDED JOINTS OF DISSIMILAR AUSTENITIC STEELS SS 202 AND SS 304 BY COLD METAL TRANSFER WELDING PROCESS." Thesis, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18063.
Full textAbstract:
Welded joints of dissimilar stainless steel sheets have many industrial applications
due to their cost effectiveness, light-weight, and high efficiency. Thin austenitic
stainless steel sheets of different thicknesses are extensively used in the automation
industry. Conventional welding techniques due to their high heat input and high
spatters have always posed problems such as burn-through and distortion for
welding these joints of thin austenitic steels. The CMT welding technique is
effectively used for the joining of thin sheets due to its characteristics of lower
distortion rate and low heat input. In this research work, austenitic stainless steels
of grade SS 202 and SS 304 of thickness 1.2 mm and 2 mm respectively were
welded by CMT welding technique and studied the mechanical characteristics of
dissimilar stainless steel joints. Taguchi L9 optimization technique was used to
find the optimized process variables for obtaining the maximum tensile strength.
The maximum tensile strength of dissimilar joint welded at 115 A current, 4 mm/s
welding speed, and 10% arc length correction factor was found to be 291 MPa.
The maximum micro-hardness value of the weld zone was achieved and the lower
value was observed in the heat-affected zone (HAZ). The X-ray diffraction (XRD)
technique was utilized to detect the residual stresses of the welded joint. The
residual stress was observed in compressive nature in the weld zone and base plate
and of tensile nature in the heat-affected zone (HAZ). CMT welding process can
produce high strength dissimilar austenitic steel joints of different thicknesses.
27
Bento, Emanuel Tavares. "ANÁLISE AO PROCESSO DE FABRICO POR WIRE-ARC ADDITIVE MANUFACTURING: Projeto e Realização de uma peça de comprovação de conceito." Master's thesis, 2021. http://hdl.handle.net/10316/98134.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaA 4ª Revolução Industrial, que decorre nos tempos atuais, pretende introduzir um conjunto de novas tecnologias no tecido industrial, entre elas, o fabrico aditivo. Este, por sua vez, promete revolucionar os processos produtivos atuais, uma vez que apresenta menores limitações em termos de complexidade geométrica, sendo possível adaptar a peça à respetiva função (em vez de a adaptar às limitações do método produtivo).Embora o foco inicial do fabrico aditivo tenha sido a implementação nos polímeros, em especial como método de ‘prototipagem rápida’, a classe de materiais com mais destaque na engenharia e indústria em geral é a dos metais, daí o recente interesse nas técnicas MAM, em especial as DED, que apresentam maiores taxas de deposição.No entanto, apesar das suas inúmeras vantagens, estas são técnicas ainda relativamente recentes, que carecem das décadas de conhecimento acumulado que os métodos convencionais possuem, pelo que, na sua maioria, ainda apresentam problemas a nível dimensional e das propriedades mecânicas obtidas, pelo que serão necessários mais estudos.Entre estas técnicas encontra-se o fabrico aditivo por arco elétrico (ou WAAM), a técnica em análise nesta dissertação. Assim, o objetivo deste trabalho é auxiliar no desenvolvimento desta tecnologia, nomeadamente, na análise inicial ao processo e no desenvolvimento duma metodologia que permita usar o sistema desenvolvido para obter peças a partir do respetivo modelo CAD.Esta dissertação é, portanto, composta por uma componente teórica onde é feita uma revisão sobre o fabrico aditivo em geral, a técnica WAAM, os sistemas cinemático e de controlo e a metodologia atualmente utilizada; e por uma componente prática onde é apresentado o sistema desenvolvido e, o procedimento experimental e respetivos resultados (ou seja, os problemas encontrados, soluções desenvolvidas e peças produzidas).
The 4th Industrial Revolution, which is taking place in current times, intends to introduce a set of new technologies into the manufacturing industry, one of them being 3D printing (or additive manufacturing). This, in turn, promises to revolutionize current production processes since it has fewer limitations in terms of geometric complexity, making it possible to adapt the part produced to its respective function (instead of adapting it to the limitations of the production method).Although its initial intent was to be implemented as a ‘rapid prototyping’ method to produce polymeric parts, the most prominent class of materials in engineering and industry in general are metals, hence the recent interest in MAM (metal additive manufacturing) techniques, in particular the ones classified under the DED (direct energy deposition) category, which have the highest deposition rates.However, despite their numerous advantages, these techniques are still relatively recent, lacking the decades of accumulated knowledge that conventional methods have. For that reason, they still present problems in terms of dimensional and mechanical properties, demonstrating the need for more studies to be performed.Among these techniques, wire-arc additive manufacturing (WAAM) is the method under analysis in this dissertation. Thus, the objective of this work is to assist in the development of this technology, namely, in the initial analysis of the process and in the development of a methodology that allows for the use of the system developed as a way to obtain parts from its CAD (computer-aided manufacturing) model.Therefore, this dissertation is composed of a theoretical part where a review is made about additive manufacturing in general, the WAAM technique, the kinematic and control systems and the methodology currently used, and by a practical part where the developed system and experimental procedure (problems found, solutions developed, and parts produced) are presented.
28
Polák, Vojtěch. "Analýza jakosti „Cold Metal Transfer“ svarů." Master's thesis, 2015. http://www.nusl.cz/ntk/nusl-250185.
Full textAbstract:
This diploma thesis is focused on overall research of the quality of joining steel and aluminum alloy using the CMT welding process. The theoretical part describes the principle and the technology of the welding system that allows joining dissimilar materials by an electric arc. Attention is also given to other modes such as CMT Advanced, CMT Pulse and CMT Advanced Pulse, which further improve the innovative process. These modifications include an efficient tandem method CMT Twin that uses two electric arcs in various combinations. The main aim of the experiment is assessment of the quality of created CMT joints. Individual tests are conducted to evaluate the corrosion resistance in an aggressive environment (salt fog). The testing subsequently evaluates mechanical properties by a destructive tensile test to determine the tensile strength. Part of the quality assessment is metallographic analysis including determining the elemental composition of the weld.
29
ROY, JAYANTA GHOSH. "INVESTIGATION ON MICROSTRUCTURE AND MECHANICAL CHARACTERISTICS OF STAINLESS STEEL USING COLD METAL TRANSFER (CMT)." Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19741.
Full textAbstract:
Gas Metal Arc Welding (GMAW) is an effective process of joining of various
materials such as stainless steel, aluminum, nickel etc. The cold metal transfer (CMT)
welding is the latest innovation of GMAW process with lower heat input for specially
joining of lower thickness materials. CMT welding is much suitable for defect free welding
with superior quality of thin materials. The microstructural characterization and
mechanical properties of the CMT welded joints is found beneficial over conventional
GMAW welding processes.
Stainless steel metal is widely using in various industrial and structural applications
due to its excellent mechanical, wear and corrision properties. In this research CMT
welding process have been applied for studying the the weld bead geomentry and
fabrication of thin AISI 304 stainless steel sheets butt welded joints. Studies were carried
out to examine the effect of various input welding parameters such as welding current,
welding speed and contact-to work-distance (CTWD) on the bead geometry, dilution and
heat input of CMT weld bead. Taguchi L9 orthoganal design matrix was applied for finding
the optimal process parameters on weld bead geometry. Results shows that welding speed
is the most significant welding process parameter, followed by welding current and CTWD
on weld bead geometry.
Box-Behnken design matrix under Response Surface Methodology (RSM) technique
was applied for finding the optimal input welding parameters to in order to obtain
v
maximum tensile strength of welded joints. Welding speed, welding current, CTWD and
arc correction factors are chosen as input welding parameters and analysed the relationship
with tensile properties of welded joints. The optimal welding parameters are welding
current of 95 A, a welding speed of 8 mm/sec, CTWD 5 mm and arc correction factor of -
10 for obtaining maximum tensile strength of the welded joints. The results show that
there is no fracture on the weld joint; the tensile residual stress levels of all the samples are
in a controlled manner. FESEM images reveal a dimpled morphology and crack-free tensile
fracture surfaces in welded joints.
Ultrasonic vibrations combined fabrication techniques enhances the structural
efficiency of manufactured products. It gives an appreciable advantages in microstructural
and mechanical properties of products. Ultrasonic assisted Cold Metal Transfer (U-CMT)
welding technique is used to join the AISI 304 stainless steel. The welded joints are
analyzed using optical microscopy, FESEM and XRD. The mechanical properties of the
U-CMT welded joint are evaluated using microhardness, tensile and residual testing and
compared CMT welded joints. Two different ultrasonic vibrational amplitude 50 µm & 99
µm and three different welding currents 85A, 90A and 95A were chosen in this study. The
microhardness and tensile results of U-CMT welded joint shows considerable
improvement in their properties. The U-CMT welded samples experiences enhanced
mechanical properties due to refinement of grains in welded region, which is produced by
ultrasonic vibrations. The joint prepared by welding current of 95A with ultrasonic
vibrational amplitude 50 µm shows better welding properties than other welded samples.
30
Neilson, David Andrew Hunter. "Welding of light gauge infill panels for steel plate shear walls." Master's thesis, 2010. http://hdl.handle.net/10048/1436.
Full textAbstract:
Ductile steel plate shear walls are an established lateral load resisting system. Past research indicates that cold-rolled infill panels less than 1 mm in thickness present one solution to an overstrength problem arising from selecting an infill panel thickness based on ease of welding and handling. This research program examines several possible welding procedures and joint geometry to connect the thin infill panel to the thick boundary elements.
Primary welding parameters include short-circuiting gas metal arc welding process, electrode and shielding gas selection, heat input, and use of a chill strip. Four configurations of the infill panel-to-boundary element joint and two configurations of a lap splice joint between two sheets of thin steel in the infill panel were tested in monotonic tension and cyclic tension-compression. A quasi-static cyclic test of a single-storey moment resisting frame steel plate shear wall validated the use of one welding procedure and joint geometry.Structural Engineering
31
Lopes, César Filipe Garrido. "Tratamento térmico T6 De Soldadura Robotizada CMT Na Liga AA6061-T4." Master's thesis, 2019. http://hdl.handle.net/10316/93632.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaEsta dissertação de mestrado tem por objetivo estudar a influência das condições de tratamento térmico T6 na recuperação das características mecânicas da soldadura, perdidas devido ao processo de soldadura Cold Metal Transfer, na liga AA6061. Este estudo pretende contribuir para a otimização do processo industrial de produção de quadros de bicicleta da empresa Triangle’s.Quadros de bicicleta, produzidos nas atuais condições de fabrico, foram fornecidos pela empresa Triangle’s Cycling Equipment, S.A.. No atual processo produtivo, a matéria-prima é fornecida no estado tratado T4, submetida a deformação plástica por extrusão ou hidroformação, soldada por soldadura Cold Metal Transfer com fio de adição AA4043 e tratada termicamente. Com o objetivo de recuperar as propriedades mecânicas perdidas em todo o processo, estes quadros são submetidos a um tratamento térmico complexo, por forma a obter o estado de tratamento T6.Foram comparados os tempos e temperaturas deste tratamento com resultados obtidos em trabalhos anteriores, de forma a avaliar o progresso do processo produtivo da empresa. Foi também avaliado o comportamento mecânico do material base quando submetido a tratamento similar.Dos dois quadros analisados com parâmetros de tratamento térmico iguais, um deles revelou pior comportamento à tração, e ambos obtiveram valores de microdureza e resistência à tração inferiores aos quadros da mesma empresa estudados em trabalhos anteriores, mas com diferentes parâmetros de tratamento térmico. Algumas soldaduras revelaram diluição deficiente de Magnésio na Zona Fundida e, consequentemente, má recuperação dos valores de microdureza.
The goal of this master’s dissertation is to evaluate the influence of the time and temperature used in the heat treatment on the recovery of mechanical properties lost under the Cold Metal Transfer welding process, in the AA6061 alloy. This study intends to contribute to optimize the industrial process of production of bicycle frames of Triangle's company.Bicycle frames, fabricated in the current production conditions, were provided by Triangle’s Cycling Equipment, S.A.. In the current production process, raw material arrives at the plant in the T4 state, being subjected to plastic deformation by extrusion or hidroforming, welded by Cold Metal Transfer with an AA4043 filler wire and finally heat-treated. With the purpose of recovering the mechanical properties lost in this process, these bicycle frames are subjected to a complex heat treatment, in order to obtain the T6 treated state.Times and temperatures of this treatment were compared to results obtained in previous experiments, to evaluate the company’s productive progress. It was also evaluated the mechanical behavior of the base material submitted to the same treatment.Out of the two studied frames with the same heat treatment parameters, one of them revealed poor tensile behavior, and both obtained inferior microhardness and tensile strength values in comparison to frames of the same company, studied in previous investigations, but with different heat treatment parameters.Some welded joints revealed poor Magnesium dilution in the Melted Area and, as a consequence, poor recovery of the microhardness values.
32
Silva, Flávio. "Soldadura robotizada com tecnologia CMT." Master's thesis, 2015. http://hdl.handle.net/10400.26/8151.
Full textAbstract:
A soldadura é um processo fundamental na indústria, permitindo união de diferentes componentes. Cada vez mais existe uma preocupação com a segurança e controlo de qualidade dos automóveis. Um dos parâmetros a penetração da soldadura é essencial para manter a integridade estrutural dos componentes soldados, para tal foram analisados alguns processos aplicados na indústria automóvel. Aprofundando os conhecimentos de soldadura expondo o seu desenvolvimento ao longo dos anos e caracterizando em pormenor a soldadura TIG, MIG/MAG e CMT, nomeadamente os seus princípios de funcionamento, parametrização, vantagens e desvantagens. Foi efetuado ensaio experimental de modo a verificar as suas potencialidades e cumprimento dos requisitos necessários para soldadura de componentes a utilizar na indústria automóvel. Para tal foram efetuadas análises de macrográfica a cordões de soldadura com diferentes parâmetros, de modo a verificar a penetração da soldadura. Tendo sido também efetuada análise de micro durezas nas juntas soldadas.
33
Simonato, Guilherme. "Otimização de soldagem robotizada em ligas de alumínio com modo de transferência pulsado e CMT+P através do método Taguchi." Master's thesis, 2017. http://hdl.handle.net/10198/14594.
Full textAbstract:
Mestrado com dupla diplomação com a Universidade Tecnológica Federal do ParanáNas últimas décadas, as ligas de alumínio têm vindo a ser cada vez mais utilizadas em diferentes campos industriais. Apesar das enormes vantagens deste tipo de materiais, surgiram grandes desafios relacionados com os processos de transformação, nomeadamente, os processos de ligação por soldagem tradicionais que, para as ligas de alumínio, são mais difíceis de efetuar com a qualidade exigida. No sentido de ultrapassar estas dificuldades, algumas indústrias e centros de pesquisa têm-se dedicado ao estudo da soldagem de ligas de alumínio. Como tal, este trabalho insere-se nesta área de pesquisa. Pretendeu-se determinar os parâmetros ótimos de soldagem e influência de cada um deles na qualidade de soldagem para dois métodos distintos de transferência de material de adição processo MIG, Pulsado e CMT+P. Para tal, implementou-se um planejamento de experimentos baseado numa matriz ortogonal de Taguchi L27 utilizando os parâmetros de início e final de soldagem. Os experimentos foram executados nos laboratórios do Instituto Politécnico de Bragança, utilizando um robô industrial e foram soldadas 30 chapas da liga Al 6082-T6. Após a realização dos experimentos, fez-se controle da qualidade a partir da medição de algumas dimensões do cordão de soldagem, especificamente, largura, penetração e reforço. Os resultados das medições foram tratados estatisticamente de modo a obter os objetivos pretendidos, para tal, recorreu-se a uma análise de variância e à razão sinal/ruído desenvolvida por Taguchi. Verificou-se que as combinações ótimas são distintas para os diferentes modos de transferência, bem como, os valores obtidos nas medições para a mesma combinação de parâmetros. Quanto a influência dos parâmetros nos fatores de controle, ela varia em função do modo de transferência e do fator de controle. Assim, para o modo de transferência pulsado, na penetração o parâmetro mais influente é a correção anti-adesão (14,3%) enquanto que na largura do cordão é mais influente o pré-fluxo de gás (21,5%). Já para o modo CMT+P, o valor nominal do gás é o fator mais influente, tanto para a largura do cordão (20,6%) como para penetração do cordão de solda (13,55%). A utilização do método Taguchi demonstrou ser uma metodologia robusta para a determinação da combinação ótima de parâmetros para a obtenção de soldaduras de qualidade, bem como, permitiu definir quais os parâmetros mais influentes no controle da qualidade de soldagem.
In the last decades, the aluminum alloys are being widely used in the different fields of the industry. Despite of the great advantages of this type of materials, there are big challenges related to the transformation processes as joining with regular welding of aluminum alloys, that are hardly performed with the quality required. To overcome these difficulties, some industries and research centers are investigating the welding of aluminum alloys. As well as the present paper is part of this field of research. The goal was determining the optimal welding parameters and the influence of each one on the quality of MIG welding for two different transference methods of filling material, pulse and CMT+P. It was implemented the design of experiments based on the Taguchi orthogonal array L27 using the initial and final welding parameters. The experiments were performed at the laboratories of the Instituto Politécnico de Bragança, using an industrial robot to weld 30 plates of Al 6082-T6. After the experiments, the quality control was performed by the measurement of some dimensions of the welded bead, particularly the width, penetration and reinforcement. The data was statistically treated to achieve the aimed objectives, through the analysis of variance and signal to noise ratio developed by Taguchi. It was verified that the optimal combinations were different between the transference methods, as well as the values obtained from the measurements for the same combination of parameters. About the influence of parameters on the control factors, it varies in function of the transference method and the control factor. For the transference method pulse, for penetration the most influent parameter is the anti-adherent correction (14,3%) and for width the most influent is the gas pre-flow (21,5%). The method CMT+P the nominal gas value is the most influent factor for both width (20,6%) and penetration (13,55%). The utilization of the Taguchi method proved to be a robust methodology to determine the optimal parameters combination to get quality welds, as well as allows defining which parameters are more influents on the welding quality control.