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Fusion Welding Process - An Overview Fusion Welding Processes

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Fusion Welding Process - an overview

Numerical and Computational Methods

K. Runesson, ... L.-E. Lindgren, in Comprehensive Structural Integrity, 2003

3.05.5.2.1 Preliminaries about physical couplings

The fusion welding process involves different physical phenomena in the arc and metal in addition to heat flow and deformations. Appropriate simplifications (discussed below) lead to a weakly coupled thermomechanical analysis and, possibly, a metallurgical analysis. The mechanical analysis should be carried out under the assumption of large deformations, whereas it is normally sufficient to assume quasistatic conditions.

The general couplings between the relevant physical fields were given in Figure 1. It is noted that all fields are coupled within the same spatial domain. This contrasts to, e.g., fluid–structure interaction, where the coupling is over a common interface. Thus, the couplings are essentially due to interactions that affect the material properties. The most important couplings are highlighted in Figure 3 (which is a subset of Figure 1):

Figure 3. Couplings in thermomechanical analysis of welding, subset of Figure 1.

(i)

Temperature changes drive the deformation.

(ii)

Deformation and friction at contacts generate heat in the material. Deformation may also change thermal boundary conditions due to changing contact conditions (such as fixtures).

(iii)

Latent heat arises from phase changes. Thermal properties depend on the phase composition.

(iv)

Temperature changes drive the microstructure changes.

(v)

Macroscopic stress affects the microstructure changes.

(vi)

Phase changes bring about volume and shape changes.

With the exception of Chen and Sheng (1992), the literature does not contain any CWM computation where a separate CFD analysis of the fluid flow in the weld puddle has been carried out. Instead, it is common to introduce several modeling assumptions for this high-temperature region. Typically, it may be approximated by a “soft” solid with low elasticity and strength in the mechanical analysis and a heat input model in the thermal analysis. Sometimes, the weld puddle is assigned a high value of conductivity for imitating convective heat transfer. Thus, the actual physics that takes place in the weld pool is modeled in a considerably simplified manner. The more complex models of these phenomena (Zacharia et al., 1995; Zhu, 1998; Sudnik et al., 2000) are not coupled to the mechanical analysis. However, such advanced models can be used to predict the shape of the weld pool (Sudnik et al., 2000) and to refine the heat input models.

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Resistance welding processes

Gene Mathers, in The Welding of Aluminium and its Alloys, 2002

9.1 Introduction

Resistance welding is a fusion welding process that requires the application of both heat and pressure to achieve a sound joint. The simplest form of the process is spot welding where the pressure is provided by clamping two or more overlapping sheets between two electrodes (Fig. 9.1).A current is then passed between the electrodes, sufficient heat being generated at the interface by resistance to the flow of the current that melting occurs, a weld nugget is formed and an autogenous fusion weld is made between the plates. The heat generated depends upon the current, the time the current is passed and the resistance at the interface. The resistance is a function of the resistivity and surface condition of the parent material, the size, shape and material of the electrodes and the pressure applied by the electrodes.

9.1. Principles of spot welding process.

There are a number of variants of the resistance welding process including spot, seam, projection and butt welding. It is an economical process ideally suited to producing large numbers of joints on a mass production basis. Spot welding in particular has been used extensively in the automotive industry, albeit mostly for the joining of steel and in the aerospace industry for airframe components in aluminium alloys. Seam welding is used in the production of thin sheet, leak-tight containers such as fuel tanks. Projection welding is generally used for welding items such as captive nuts onto plate. This variation is not normally used on aluminium and is not covered in this chapter. Flash welding, unlike spot and seam welding that require a lap joint, is capable of making butt welds. This is achieved by resistance heating the abutting faces and then forging them together.

There are a couple of characteristics of aluminium that make it more difficult to resistance weld than steel. The most significant is its high electrical conductivity, requiring high welding currents and large capacity equipment. Secondly, the electrodes are made from copper which alloys with aluminium, resulting in rapid wear and a short electrode life.

As with conventional fusion welding, resistance welding suffers from similar problems of oxide entrapment and hot cracking, the latter not being helped by the lack of a more crack-resistant filler metal, and porosity.

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Joining of aluminium and its alloys

S. Lathabai, in Fundamentals of Aluminium Metallurgy, 2011

20.3.4 Laser welding

Laser welding is a fusion welding process in which the heat generated by a highenergy-density photon (light) beam produces melting (Oates, 1996, p. 71; Mathers, 2002, p. 150). Since the laser beams can be focused very sharply, a smaller volume of metal is melted and less heat energy goes into the workpiece. The concentrated, high-energy-density heat source enables the weld to be made in the keyhole mode (Fig. 20.14), improving the absorption of the laser beam due to reflections within the cavity. The deeply penetrating keyhole weld produces a very narrow weld, and a correspondingly narrow HAZ, as compared to arc welding. This minimises both distortion and the loss of strength observed in the HAZ of both heat treatable and non-heat treatable aluminium alloys (discussed further in Section 20.3.5). A further advantage is the minimisation of the loss of low boiling point alloying elements in aluminium alloys such as Mg and Zn. The high-energy beam also enables very fast welding speeds to be achieved thus improving productivity.

20.14. Schematic of keyhole laser welding.

(source: Mathers, 2002)

Laser welding is being increasingly used for joining aluminium alloys, both in the aerospace and the automotive industries. The major difficulty in laser welding of aluminium alloys is that aluminium does not couple well with the 1.06 µm wavelength light emitted by the Nd:YAG laser or the 10.6 µm wavelength emitted by the CO2 laser (Oates, 1996; Mathers, 2002). This means that the laser beam tends to get reflected, rather than being absorbed by the workpiece, thus not contributing to its melting. Furthermore, once a weld pool is established, the reflectivity goes down dramatically, resulting in a power density that is too high. However, development work carried out mostly for and by the automotive industry, has addressed these problems by improved focusing of the beam and by development of control systems which can vary the energy input to compensate for the reflectivity change when the weld pool is established. A recent Audi Press Release describes the extensive use of laser welding in its sports cars, Audi TT and Audi R8, as follows: ‘Laser welding allows large sheet panels to be joined perfectly to the body structure because its linear connecting seams are stronger and more rigid than individual weld points. In the TT, laser welding is used for high-precision invisible aluminium joints between the roof and the side panel as well as for the major welds in the sill area. Together they are 5.30 metres long. The Audi A8 sedan has more than 20 meters of such welds’ (Rügheimer, 2009). The aerospace industry also has successfully used laser welding for 2xxx and 6xxx alloys in many applications and success has also been reported in the laser welding of the Al-Li alloys 2090 and 2091 (Oates, 1996, p. 71). Clearly, laser welding of aluminium alloys has come a long way.

Laser hybrid welding

The quest for high-performance welding processes has resulted in a number of relatively recent new developments in which the laser has been combined with the arc from a conventional welding power source. Although GMAW, GTAW and plasma-arc processes have been used, GMAW has been the preferred fusion welding process (Staufer et al., 2008). Figure 20.15(a) illustrates the principle of laser hybrid welding and a sectional view of a laser-hybrid joint made between two sheets of AlMgSil (AA 6082) is presented in Fig. 20.15(b). The laser hybrid process combines the advantages of each process, while their respective disadvantages disappear. As we have seen, laser welding is characterised by a very narrow HAZ, a high ratio of weld penetration depth to weld width, and high welding speeds; however, it has a low ability to bridge gaps so that tight fit up tolerances are essential. In contrast, the low-energy-density GMAW process produces a distinctly larger weld pool and has much better ability to bridge gaps. Both processes act simultaneously at the same process zone. As shown in Fig. 20.15(c), the laser hybrid process can achieve the same weld penetration using half the wire feed speed used by GMAW when used on its own and a lower power level than that used by the laser welding process, on its own (Staufer et al., 2008). In addition, the laser hybrid process can tolerate greater variations in fit-up.

20.15. (a) Schematic representation of laser hybrid welding; (b) macrograph showing cross-sectional view of a lap weld between two sheets of AlMgSi1 (AA 6082), 2 mm and 1.5 mm thick, respectively, made using AlSi5 filler wire, 1.6 mm diameter, at deposition rate of 1.7 kg/h; (c) comparison of the weld bead profiles for laser welding, laser hybrid welding and GMAW; weld penetration depth and travel speed were held constant (schematic illustrations and photo courtesy Fronius International GmbH, Austria).

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Introduction to joining methods in medical applications

L. Quintino, in Joining and Assembly of Medical Materials and Devices, 2013

2.2.1 Laser welding

Laser-beam welding is a fusion welding process where radiant energy is used to produce the heat required to melt the materials being joined.5,10–13 A concentrated beam of coherent, monochromatic light is directed by optical devices and focused to a small spot, for higher power density, on the abutting surfaces of the parts being joined (Fig. 2.2). Gas shielding is generally used to prevent oxidation of the melted material. It provides consistent joining and high flexibility. Different parts and even different metals can be joined in a non-contact process. The required accessibility to the work piece being from one side only and the opportunity to abandon filling material completely are the main advantages of laser-beam welding. Laser joining can be performed using either pulsed or continuous lasers. A pulsed laser can be used to create weld seams by means of overlapping pulses.

2.2. Laser welding.

Lasers have played an important role in the joining of materials since the invention of high-power solid-state and gas lasers in 1964, especially for resistance trimming of electronic circuits, until the introduction of a reliable high-performance laser in the late 1970s, which allowed its application for welding of sheet-metal parts.

Several types of lasers can be used in materials processing though the most common have wavelengths of 10.6 µm – CO2 lasers (gas lasers), or 1.06 µm – Nd-YAG lasers (solid-state lasers). The last decades have seen the rise of diode lasers and diode-pumped solid-state lasers. More recently high-power diode-pumped fibre lasers were developed. Fibre lasers are a serious alternative to solid-state and carbon-dioxide lasers for different materials-processing applications.

The CO2 laser is a well-established materials-processing tool, available in power output up to 50 kW, and most commonly used for metal cutting.14 CO2 laser radiation (wavelength 10.6 µm) is readily absorbed by the surface layers of most metals and plastics. The CO2 laser beam cannot be transmitted down a silica fibre optic, but its path can be determined using mirrors, lenses in optical systems and wither gantry or robotic movement.

The Nd:YAG laser (Neodymium Yttrium Aluminum Garnet) is also well established for materials processing; it has a wave length of 1.06 µm and is a smaller laser available in powers up to 10 kW. The Nd:YAG laser beam can be transmitted down a silica fibre optic enabling easy, flexible operation with gantry or robot manipulation. However, the light from Nd:YAG lasers is absorbed far less readily in plastics than that of CO2 lasers.

Small focus spots for CO2 and Nd-YAG lasers are achieved through optical systems mounted in the arm of the robot or gantry systems.

High-power diode lasers (>100 W) have been available since the late nineties.14 Recent developments have made available diode lasers up to 5 kW and competitively priced compared with CO2 and Nd:YAG lasers. Diode lasers are energy efficient compared with other solid-state lasers (i.e. power input versus power output is 30 per cent, while for Nd:YAG laser it is 15 per cent). With diode lasers a rectangular beam shape is produced, which, while being preferential for some applications, limits the minimum spot size and maximum power density available. The diode laser source is small and light enough to be mounted on a gantry or robot for complex processing.

Excimer lasers are gas lasers which were first operated in 1975, some years after the CO2 and Nd:YAG lasers.14 The gases used to produce the laser beam are inert gas (e.g. Ar, Xe, Ne). They are available with average powers up to about 1 kW and focusable to very high-power densities. There is a family of wavelengths available by exciting different phases within the laser. These are all in the ultraviolet (0.15–0.35 µm), and lie in a photon energy range capable of breaking chemical bonds and splitting molecules. Excimer laser light is absorbed by molecules in the surface of plastics (<10 µm depth) and rapidly breaks the molecular bonds within the polymer structure. Consequently, this leads to a rapid increase in pressure and expulsion of material over a very precise region defined by the laser-beam size. Excimer laser beam is transmitted by mirrors and often focused through masks to give the required features on the material surface.

Fibre lasers were created in the early sixties and used widely at low-power levels throughout the 1980s and the 1990s as optical amplifiers. In 2000 the first 100 W fibre laser was launched. The first reports on the potential of these lasers in materials processing are very recent.15,16 The multi-kilowatt range for materials processing with fibre laser is now possible with the recent commercialization of 7–10 kW power lasers.

These new lasers have multiple advantages: high efficiency, compared with the other types of lasers; a compact design, which simplifies its installation; a good beam quality, due to the use of thin fibres and thus a small beam focus diameter; and a robust set-up for mobile applications. The scaling of the laser power is achieved by a modular design comprising several single-mode lasers. The lifetime of the pumping diodes exceeds the expected lifetime of other diode-pumped lasers, which leads to low costs of ownership.

The high-power lasers can be used for deep penetration welding in a diversity of materials and constructions as the low wavelength, similar to the one from the Nd-YAG lasers, that characterizes these lasers allows its absorption by almost all metals and alloys and the fibre delivery system provides the necessary flexibility on the positioning of the beam. Also high-speed welding of sheet-metal joints can surpass the productivities achieved with high-power CO2 lasers. Due to the low wavelength its use on the welding of plastics presents the same limitations as Nd:YAG lasers.16

In general, the use of lasers to deliver the energy necessary for welding has the following advantages:

high speed;

no contact with a heated tool;

highly automated and robotically manipulated;

controlled heating for low thermal damage or distortion.

Laser techniques are also used for the welding of plastics in medical application as an alternative to vibration, ultrasonic, dielectric, hot-plate or hot-bar welding and adhesive bonding.14

Lasers are an attractive tool for processing of metals and also polymers as it allows a precise delivery of a controlled amount of energy precisely on the point where it is required (e.g starting point of a weld, spot welding). In addition, lasers are available with outputs covering a range of wavelengths, which has a large bearing on the interaction of the light with the plastic materials. An understanding of these absorption characteristics has led to the development of other novel applications in plastics processing. Common applications include end effector tools to tube bodies and hermetically sealing implantable devices.

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Developments in hybridisation and combined laser beam welding technologies*

D. Petring, in Handbook of Laser Welding Technologies, 2013

Abstract:

The laser welding process is the most flexible fusion welding process industrially available. The degree of flexibility is further enhanced and process limits are expanded if hybridisation or combination techniques are applied. After a general introduction of various related concepts, the enhancement of welding capabilities is illustrated in more detail by the state-of-the-art and latest advancements in laser-MAG (metal active gas) hybrid welding of up to 25 mm thick high-strength steel components. In addition, the manufacturing benefits of integrated cutting and welding with a multifunctional laser combi-head are described.

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Enhancing laser welding capabilities by hybridisation or combination with other processes

D. Petring, in Advances in Laser Materials Processing, 2010

Abstract:

The laser welding process is the most flexible fusion welding process available industrially. The degree of flexibility is further enhanced and process limits are expanded, if hybridisation or combination techniques are applied. After a general introduction of various related concepts, the enhancement of welding capabilities is illustrated in more detail, on the one hand by the state-of-the art and latest advancements in laser-MAG hybrid welding of up to 25 mm thick high-strength steel components. On the other hand, the manufacturing benefits of integrated cutting and welding with a multifunctional laser combi-head are described.

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Materials

Christopher Dawes CEng, in Laser Welding, 1992

Laser welding is normally a liquid-phase (fusion) welding process, i.e. it joins metals by melting their interfaces and causing the mixing of the molten metal which solidifies on removal of the laser heat source. (Metals can be welded without melting by solid-phase welding techniques such as friction or cold pressure welding.1 A laser could in theory be used as a heat source for making solid-phase welds. however, no industrial applications are known to the author.) Lasers can be used for soldering and brazing: these applications are outside the scope of this book.

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Laser welding of metals for aerospace and other applications

J. Blackburn, in Welding and Joining of Aerospace Materials, 2012

Abstract:

Laser welding is a high-power-density fusion-welding process that produces high aspect ratio welds with a relatively low heat input compared with arc-welding processes. Furthermore, laser welding can be performed ‘out of vacuum’ and the fibre-optic delivery of near-infra-red solid-state laser beams provides increased flexibility compared with other joining technologies. Consequently, laser welding may be considered as a principal candidate for the production of metallic aerospace components for high-performance environments. This chapter details laser technology and the laser-welding process, and reviews research concerned with the laser welding of titanium alloys.

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Welding Aspects of Aluminum–Lithium Alloys

G. Madhusudhan Reddy, Amol A. Gokhale, in Aluminum-lithium Alloys, 2014

9.2 Weld Metal Porosity

Weld metal porosity is the most common defect for all fusion welding processes. Therefore, control of porosity and minimizing its adverse effects on weldment properties have been of great interest. Porosity may be gas-related or result from solidification shrinkage. In terms of size, shape, and location, porosity can be described as interdendritic porosity or bulk porosity (D’Annessa, 1967; Devletian and Wood, 1983; Martukanitz and Michnuk, 1982). Interdendritic porosity occurs when gas bubbles are formed or entrapped between dendrite arms in the solidification substructure, whereas bulk porosity is the spherical pores that result from supersaturation of gases in the weld pool.

The porosity depends on both the amount of dissolved gases and the welding process variables. Hydrogen is the principal cause of gas porosity in aluminum welds (Erokhin and Obotorov, 1971; Ol’Shanskii and Dyachencho, 1977). Voids or porosity that are generally spherical in shape are caused by the sharp decrease in solubility of hydrogen during solidification: hydrogen solubility in molten aluminum is more than 10 times the solubility in the solid metal (Mondolfo, 1979; Ransley and Neufeld, 1948). Alloying additions to aluminum influence porosity formation by affecting the solubility of hydrogen in the matrix. Alloy additions of either copper or silicon to aluminum decrease the solid solubility of hydrogen and thus increase the propensity for pore formation (Devletian and Wood, 1983). Magnesium additions considerably increase the solid solubility of hydrogen in aluminum and therefore reduce the susceptibility to pore formation. Alloying additions also influence porosity formation in aluminum weld metal by affecting the solidification range and solidification mode (Kou, 1987).

The most experience of welding lithium-containing aluminum alloys comes from welding the first-generation Russian Al–Li–Mg alloy 1420. Reviews of a number of papers show that weld metal porosity is a greater problem for Li-bearing alloys than conventional aluminum alloys (Kostrivas and Lippold, 1999; Pickens, 1985, 1990). The porosity is mainly associated with a hygroscopic complex oxide skin on the components to be welded. It is believed that complex oxides of Li, Mg, and Al form at elevated temperatures during hot working or solution treatment, and these are subsequently responsible for weld metal porosity (Fridlyander, 1970). If the oxide skin is removed by mechanical or chemical means, the porosity is greatly reduced (Fedoseev et al., 1978; Ramulu and Rubbert, 1990; Madhusudhan Reddy and Gokhale, 1993; Skillingberg, 1986). The combination of machining and chemical milling, with argon shielding during welding, gives the best results (Gittos, 1987; Madhusudhan Reddy and Gokhale, 1993) (Table 9.2), which is for the second-generation Russian Al–Li–Cu–Mg alloy 1441.

Table 9.2. Effect of Surface Preparation and Shielding on Oxidation and Porosity in 1441 Al–Li–Cu–Mg Sheet Alloy Welds

S.NoSurface Condition and ShieldingWeld Quality
1As-receivedHeavy oxidation
2Wire brushedGross porosity
30.1 mm machinedGross porosity
40.2 mm machinedDense fine porosity
50.2 mm machined+argon backingFine fusion line porosity+sparse fine porosity
60.2 mm machined+chemically cleaned+argon backingLowest porosity

Source: Madhusudhan Reddy and Gokhale (1993).

Sheets welded in the as-received condition or in the wire brushed condition resulted in gross porosity, as shown in Figure 9.1. The thickness of surface layer that needs to be removed for low-porosity welds depends on the nature and extent of prior heat treatments that result in surface oxidation.

Figure 9.1. Effect of surface preparation on weld porosity in 1441 Al–Li–Cu–Mg alloy sheet, (A) as-received condition and (B) wire brushed condition (Madhusudhan Reddy and Gokhale, 1993).

Inert gas backing is not usually necessary when welding aluminum alloys, but the observation of reduced porosity listed in Table 9.2 is consistent with the results of Ischenko and Chayun (1977). The beneficial effect of inert gas backing is probably a further indication of the high reactivity of Li. The use of a vacuum heat treatment to minimize the weld zone porosity in alloy 1420 was studied by Mironenko et al. (1979a, 1979b). Vacuum heat treatment was performed for 12–24 h and in the temperature range of 450–500°C (Kostrivas and Lippold, 1999). This pretreatment appreciably reduced the weld zone porosity in both gas tungsten arc (GTA) and electron beam (EB) welds. The porosity reduction was attributed to the vacuum heat treatment driving off hydrogen entrapped in the surface layers. However, such thermal treatments will soften the base metal, and this means that ageing following welding will be required to recover the mechanical properties. In addition, this method cannot generally be used for large structural components and is expensive.

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Research on reverse dual rotation friction stir welding process

H.J. Liu, ... W.J. Duan, in Proceedings of the 1st International Joint Symposium on Joining and Welding, 2013

1 Introduction

As a solid-state joining technique which has the capability to avoid defects associated with conventional fusion welding processes, friction stir welding (FSW) has been widely applied to weld almost all series of aluminum alloys in the past two decades since it was invented by The Welding Institute (TWI) of UK in 1991 1),2),3). In conventional FSW, it is appropriate to design the tool shoulder diameter as about three times the plate thickness, aiming to obtain the optimal weld formation and mechanical properties. Therefore, there is an obvious gradient for the tangential speed on the shoulder surface, increasing from zero at the tool pin centre to the maximum at the outer diameter of the shoulder. Depending on the materials and applied welding parameters, the over-heating or even incipient melting may occur along the shoulder edge on the weld top surface. This phenomenon is particularly obvious for the thick plates because a larger shoulder diameter should be utilized. As for the heat-treatable aluminum alloys strengthened by precipitates, the over-heating or incipient melting has great deterioration on microstructures, leading to the decrease of mechanical properties. To avoid the caused deterioration, the dual rotation FSW was proposed in TWI as a variant technique 4). In the welding process, the separated tool pin and assisted shoulder rotate independently, and their rotation speeds can be different as desired. Because the majority of heat in FSW is produced by the tool shoulder 5),6), not only the overheating or incipient melting at the shoulder edge, but also the peak temperature and dwelling time at the higher temperature can be reduced through decreasing the rotation speed of the assisted shoulder while keeping a higher rotation speed of the tool pin. Such characteristic and feasibility have been confirmed by the preliminary experiments conducted on the 5083-H111 and 7050-T7451 aluminum alloys4).

In addition, the large process load of conventional FSW also constrains its application in the on-site manufacturing and in-orbit repair of large-scale aluminum alloy components. Widener et al. 7) and Crawford et al.8) carried out the research on the high-rotation-speed FSW, and observed that the process load was reduced but the flash defects and cavity defects were formed. A non-rotational shoulder was directly added to surround the rotating tool to eliminate such defects. Liu et al.9),10),11) also performed the non-rotational shoulder assisted FSW (NRSA-FSW). To reduce the process load, the diameter of the rotating sub-size concave shoulder was decreased to twice the plate thickness, while the outer diameter of the assisted non-rotational shoulder was the same as the shoulder diameter of conventional FSW tool to guarantee the weld formation, about three times the plate thickness. Experiments showed that the NRSA-FSW could produce defect-free joints in a wider range of welding parameters when compared with the FSW in which the tool had a sub-size concave shoulder and had not an assisted shoulder 10). The welding torque and axial plunge force could be reduced greatly because of the decreased diameter of the rotating sub-size concave shoulder, but the transitional force was still large because the non-rotational shoulder plunges into the specimens when it traveled forward. It can be imaged that the transitional force can be reduced by applying the dual rotation FSW, because the rotating assisted shoulder can heat the anterior materials when it rotates and moves forward with the rotating tool pin.

Combining the dual rotation FSW 4) and the re-stir FSW 12),13), a reverse dual rotation FSW (RDR-FSW) is proposed in the present research. In this FSW process, the tool pin and the assisted shoulder rotate in the reverse direction at different rotation speed. Except for inheriting advantages of the dual rotation FSW, the RDR-FSW can reduce the clamping requirement of welding samples. The welding torque exerted on the workpiece by the reversely rotating assisted shoulder is in the reverse direction to that exerted by the rotating tool pin, thus the total welding torque exerted on the workpiece by the RDR-FSW tool system is reduced. Once the process load and clamping requirement are reduced, the size and mass of the FSW equipment and the fixture can be decreased, thus it is feasible for the FSW to be applied in the on-site manufacturing and the in-orbit repair of large-scale aluminum alloy components. Additionally, the tool pin and the assisted shoulder may cause plasticized material to flow in the opposite direction due to their reverse rotation, and thus reducing the asymmetry of joints produced by the conventional FSW. In the present research, a tool system for the RDR-FSW was designed according to its working process, and a high strength aluminum alloy 2219-T6 was chosen as the experimental material to demonstrate the characteristics of the weld formation and joint properties.

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Fusion Welding Process - an overview

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