Avaliação metalúrgica da liga de alumínio AA6056 soldada por "friction stir welding" nas condições T4 e T6

Com o desenvolvimento do processo de soldagem por "Friction Stir Welding" tornou-se possível a obtenção de uma junta soldada com propriedades superiores a aquelas realizadas a partir de processos convencionais de soldagem (MIG, TIG, etc ). Além disto, com este processo é possível minimizar a incidência de imperfeições que ocorrem quando certos materiais são soldados por técnicas convencionais. A partir disto, este trabalho visa avaliar as propriedades metalúrgicas de uma liga de alumínio AA6056 soldado em duas condições de envelhecimento: T4 (envelhecimento natural) e T6 (envelhecimento artificial), com duas condições de soldagem. Os resultados indicam variações de dureza em toda a extensão da solda, desde o centro da solda ("nugget") passando pela zona termomecânica afetada, zona termicamente afetada, até o metal base. Observou-se, também, que a solda que apresentou um desempenho superior foi a realizada com a maior velocidade de soldagem aplicada no material envelhecido naturalmente, mas com um envelhecimento artificial aplicado posteriormente ao processo de soldagem, em uma temperatura de 190°C durante 2 horas

Características de tenacidade à fratura da liga de alumínio AA6056 T4 e T6 soldada pelo processo de fricção e mistura mecânica

As propriedades mecânicas e metalúrgicas de uma junta soldada devem ser minuciosamente estudadas para que se possa qualificá-la para aplicação em engenharia. Assim, com o desenvolvimento de novos processos de soldagem torna-se necessário um estudo detalhado para determinação destas propriedades. Este é o caso da soldagem por Fricção e Mistura Mecânica (Friction Stir Welding) em que, ao contrário das outras técnicas convencionais, a temperatura de fusão do material não é atingida durante o processo. Com isto, vários problemas que são relacionados às altas temperaturas desaparecem e, além disto, excelentes propriedades mecânicas são atingidas. Neste trabalho buscou-se verificar a influência de dois tratamentos térmicos (T 4 e T6) aplicados à liga de alumínio AA6056 soldada Fricção e Mistura Mecânica, principalmente nas diferentes regiões resultantes deste processo (zona termomecanicamente afetada, zona termicamente afetada e centro da solda). Para isto foram realizadas metalografias, ensaios de microdureza e ensaio de tenacidade à fratura em cada região. Os resultados indicam que o envelhecimento artificial altera a microdureza, mas não aumenta a tenacidade à fratura. Caso este envelhecimento for aplicado, recomenda-se fazê-lo antes do processo de soldagem para atingir uma maior tenacidade.The mechanical and metallurgical properties of welded materiais must be completely understood to qualify it application. The development of new welding techniques requires a detailed study to determine it properties. This is the case of friction stir welding method (FSW) where the melting temperature is not reached in the weld zone in opposite of other conventional welding processes. The consequence is the disappearance of many problems related to high temperature and excellent mechanical properties. The aim of this work is to determine the influence of the T4 and T6 conditions in the fracture toughness of AA6065 aluminium alloy friction-stir welded, especially in the different zones resulting from the process (thermomechanically affected zone - TMAZ, heat affected zone - HAZ and nugget. The results indicate that the artificial aging modifies the properties but does not result in higher fracture toughness. lf T6 heat treatment is necessary it should be done prior to the welding process to achieve higher fracture toughness

Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications

The use of adhesives for fixing low-weight elements is showing increasing interest in the industry, as it would reduce the weight of the assembly, costs, and production time. Specifically, the application of pressure-sensitive adhesives (PSAs) to join non-structural naval components to aluminium substrates has not yet been reported. In the present work, a study of the mechanical behaviour of different double-sided PSAs applied on bare aluminium alloy substrates is performed. The influence of surface roughness, surface chemical treatments, and the matrix of the adhesives is studied through different mechanical tests, such as shear, T-peel, and creep. The application of an adhesion promoter improved the mechanical behaviour. Low roughness substrates provided better performance than ground samples. Acrylic foam adhesives were subjected to creep tests, whose results were fitted to a simple mathematical model, predicting the fracture time as a function of the applied load

Pulsed Laser Welding Applied to Metallic Materials-A Material Approach

Joining metallic alloys can be an intricate task, being necessary to take into account the material characteristics and the application in order to select the appropriate welding process. Among the variety of welding methods, pulsed laser technology is being successfully used in the industrial sector due to its beneficial aspects, for which most of them are related to the energy involved. Since the laser beam is focused in a concentrated area, a narrow and precise weld bead is created, with a reduced heat affected zone. This characteristic stands out for thinner material applications. As a non-contact process, the technique delivers flexibility and precision with high joining quality. In this sense, the present review addresses the most representative investigations developed in this welding process. A summary of these technological achievements in metallic metals, including steel, titanium, aluminium, and superalloys, is reported. Special attention is paid to the microstructural formation in the weld zone. Particular emphasis is given to the mechanical behaviour of the joints reported in terms of microhardness and strength performance. The main purpose of this work was to provide an overview of the results obtained with pulsed laser welding technology in diverse materials, including similar and dissimilar joints. In addition, outlook and remarks are addressed regarding the process characteristics and the state of knowledge

Effect of process parameters on pulsed laser welding of AA5083 alloy using response surface methodology and pulse shape variation

Aluminium alloys exhibit eco-friendly aspects related to global environmental issues, such as almost unlimited recyclability. Nevertheless, some intrinsic characteristics are challenges to explore all their benefits. In the welding process, the high thermal conductivity and low melt point require high control of heat input. Alternatively, the pulsed laser mode provides a sharp beam focus with precise control enabling regulating the energy delivered. In this sense, this present work analysed the effect of pulsed laser welding parameters on 3-mm-thick AA5083 aluminium alloy sheets. Trials targeted to develop sound welds with minimum defect and high penetration depth adopting statistical methods. The optimum parameter arrangement was achieved by varying peak power, spot diameter, and pulse duration. Finally, the best parameter combination was applied using different pulse shapes to mitigate crack formation and pores. As a result, the pulse shape with step-down at the end of each pulse generated crack-free spot welds

Low-Energy Pulsed-Laser Welding as a Root Pass in a GMAW Joint: An Investigation on the Microstructure and Mechanical Properties

Root pass is a fundamental step in multi-pass welding. In gas metal arc welding (GMAW), the weld bead qualities depend on the process parameters, filler materials, and welder abilities. This work investigates the effect of a Nd: YAG pulsed laser as a first pass to reduce the welders' reliance on the AH36 low-alloy steel with 5.5 mm thickness. This autogenous automatable process delivers reduced thermal impact due to the concentrated high-energy source, pulse overlap, and higher penetration depth-to-power ratio than continuous lasers. The outcomes indicate that the PL as a root welding generated a small HAZ compared to the GMAW condition. In addition, the subsequent arc passes positively affected the microstructure, reducing the hardness from around 500 to 230 HV. The PL + GMAW achieved similar strength results to the GMAW, although its Charpy impact values at -50 degrees C were around 15% lower than the arc condition.This work was financial supported from the Program for the Promotion and Impulse of Research and Transfer of the University of Cadiz (Reference project: IRTP02_UCA)

Mechanical behaviour of double side high performance PSA adhesive applied to painted naval structures

The use of adhesives constitutes a well-established technology in the aeronautical and automotive industries. A rising interest in the use of these materials has appeared in naval industry, where using adhesives in non-structural areas implies the reduction of welding to fix low weight components, making the joining process cheaper and faster. Among the different families of available adhesives, double-sided Pressure Sensitive Adhesives (PSAs) are considered of great industrial interest. A high performance PSA has been employed to join specimens of carbon steel coated with an epoxy painting scheme approved by the naval sector. The present paper reports for the first time the influence of some experimental application variables of this PSA-coated naval steel system on its mechanical behaviour. Standard shear and tensile tests have shown that the curing conditions, surface preparation and paint roughness have considerable effects on the resistance of these adhesive joints

Equipamento de solda por fricção a topo em elementos tubulares e método de solda por fricção a topo em elementos tubulares

Mattei, FabianoEngenhariaDepositad

Equipamento de movimentação e posicionamento de elementos tubulares para soldagem

PETROBRASUniversidade Federal do Rio Grande do SulEngenhariaDepositad

Tubo rígido metálico com extremidades mais espessas, riser submarino, processo e sistema de fabricação de tubo rígido metálico com extremidades mais espessas

PETROBRASUniversidade Federal do Rio Grande do SulEngenhari