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keyhole-mode welding
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Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005627
EISBN: 978-1-62708-174-0
... constant power density boundaries, showing the relationship between the focused beam diameter and the absorbed beam power for approximate regions of keyhole-mode welding, conduction-mode welding, cutting, and drilling. absorbed beam power conduction-mode welding cutting drilling electron beam...
Abstract
This article provides a history of electron and laser beam welding, discusses the properties of electrons and photons used for welding, and contrasts electron and laser beam welding. It presents a comparison of the electron and laser beam welding processes. The article also illustrates constant power density boundaries, showing the relationship between the focused beam diameter and the absorbed beam power for approximate regions of keyhole-mode welding, conduction-mode welding, cutting, and drilling.
Image
in Introduction to High Energy Density Electron and Laser Beam Welding
> Welding Fundamentals and Processes
Published: 31 October 2011
Fig. 4 Constant power density boundaries showing the relationship between the focused beam diameter and the absorbed beam power for approximate regions of keyhole-mode welding, conduction-mode welding, cutting, and drilling
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Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001357
EISBN: 978-1-62708-173-3
... Abstract Plasma arc welding (PAW) can be defined as a gas-shielded arc welding process where the coalescence of metals is achieved via the heat transferred by an arc that is created between a tungsten electrode and a workpiece. This article discusses the melt-in mode and the keyhole mode...
Abstract
Plasma arc welding (PAW) can be defined as a gas-shielded arc welding process where the coalescence of metals is achieved via the heat transferred by an arc that is created between a tungsten electrode and a workpiece. This article discusses the melt-in mode and the keyhole mode of the PAW process, as well as the advantages and disadvantages. It describes the components of a basic PAW system, namely the power source, plasma control console, water cooler, welding torch, and gas supply system for the plasma and shielding gases. The article provides information on the applications of the PAW process and discusses the typical components and joints used. It concludes with information on personnel requirements and safety issues.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005582
EISBN: 978-1-62708-174-0
... operating modes, often described as the melt-in mode and the keyhole mode: The melt-in-mode refers to a weld pool similar to that which typically forms in the gas tungsten arc welding (GTAW) process, where a bowl-shaped portion of the workpiece material that is under the arc is melted...
Abstract
Plasma arc welding (PAW) can be defined as a gas-shielded arc welding process where the coalescence of metals is achieved via the heat transferred by an arc that is created between a tungsten electrode and a workpiece. This article focuses on the operating principles and procedures, current and operating modes, advantages, disadvantages, and applications of PAW. It discusses the personnel and equipment requirements, as well as the joints used in the process. The power source, plasma control console, water cooler, welding torch, and gas supply system for the plasma and shielding gases are also reviewed.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005636
EISBN: 978-1-62708-174-0
... for conduction-mode laser and electron beam welding. Heat transfer in keyhole-mode laser and electron beam welding is much more complex. Similar to the handling of heat transfer from metal droplets in GMAW, heat transfer from the keyhole can be either simulated directly or approximated using a volumetric heat...
Abstract
This article provides a comprehensive review and critical assessment of numerical modeling of heat and mass transfer in fusion welding. The different fusion welding processes are gas tungsten arc welding, gas metal arc welding, laser welding, electron beam welding, and laser-arc hybrid welding. The article presents the mathematical equations of mass, momentum, energy, and species conservation. It reviews the applications of heat transfer and fluid flow models for different welding processes. Finally, the article discusses the approaches to improve reliability of, and reduce uncertainty in, numerical models.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005600
EISBN: 978-1-62708-174-0
... a keyhole in the metal, providing both deep penetration and high processing speeds. These two modes are described in the section “Modes of Operation” in this article. In addition, the major process variables for either mode of operation include three sets of welding parameters: the variables...
Abstract
Hybrid laser arc welding (HLAW) is a metal joining process that combines laser beam welding (LBW) and arc welding in the same weld pool. This article provides a discussion on the major process variables for two modes of operation of HLAW, namely, stabilization mode and penetration mode. The major process variables for either mode of operation include three sets of welding parameters: the variables for the independent LBW and gas metal arc welding processes and welding variables that are specific to the HLAW process. The article discusses the advantages, limitations, and applications of the HLAW and describes the major components and consumables used for HLAW. The components include the laser source, gas metal arc welding source, hybrid welding head, and motion system. The article also describes the typical sources of defects and safety concerns of HLAW.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005603
EISBN: 978-1-62708-174-0
... or keyhole containing evaporated atoms of the substrate and ionized gas. These conditions are illustrated for diffuse and concentrated intensity distributions in Fig. 7 and 8 , respectively, and coarsely reflect the two primary conditions for beam welding, that is, conduction- and keyhole-mode welding...
Abstract
Three types of energy are used primarily as direct heat sources for fusion welding: electric arcs, laser beams, and electron beams. This article reviews the physical phenomena that influence the input-energy distribution of the heat source for fusion welding. It also discusses several simplified and detailed heat-source models that have been used in the modeling of arc welding, high-energy-density welding, and resistance welding.
Image
Published: 30 November 2018
Fig. 1 Modes of laser welding. (a) Conduction-limited laser welding. (b) Penetration (keyhole) laser welding. Source: Ref 5
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Image
Published: 31 October 2011
Fig. 15 Schematic illustration of the (a) melt-in or conduction versus (b) keyhole modes in high-energy-density welding processes, including plasma arc welding, electron beam welding, and laser beam welding. Source: Ref 2
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Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005579
EISBN: 978-1-62708-174-0
... by welding parameters and material properties ( Ref 23 ); unsteady Marangoni flow in a molten consisting of immiscible dissimilar metals ( Ref 24 ); welding of stainless steel plates containing different concentrations of sulfur ( Ref 25 ); heat transfer and fluid flow during keyhole mode laser welding ( Ref...
Abstract
Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects in gas tungsten arc (GTA) welds. This article describes the surface-tension-driven fluid flow model and its experimental observations. The effects of mass transport on arc plasma and weld pool are discussed. The article reviews the strategies for controlling poor and variable penetration and describes the formation of keyhole and fluid flow in electron beam and laser welds. It also explains the fluid flow in gas metal arc welding and submerged arc welding, presenting its transport equations.
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001334
EISBN: 978-1-62708-173-3
... and, when it falls into the keyhole at irregular times, it nearly fills the cavity and produces large penetration variations. Gas Metal Arc Welding Fluid flow certainly occurs in GMA weld pools, but reports on the details of its nature and effects are quite limited. In the spray transfer mode...
Abstract
High-velocity gas motion occurs in and around the arc during welding. This article describes the phenomena of gas flow in gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). The effect of trace element impurities on GTA weld penetration of selected alloys is presented in a table. The article concludes with a discussion on submerged arc welding (SAW).
Series: ASM Handbook
Volume: 2A
Publisher: ASM International
Published: 30 November 2018
DOI: 10.31399/asm.hb.v02a.a0006502
EISBN: 978-1-62708-207-5
... the weldability of aluminum alloys, such as dual spot welding for keyhole stability, pulsed mode for eliminating solidification cracking, laser spot stirring for porosity suppression, and laser-hybrid methods for improving gap-bridging ability and weld penetration depth. The addition of filler metal can...
Abstract
Most welding lasers fall into the category of fiber, disc, or direct diode, all of which can be delivered by fiber optic. This article provides a comparison of the energy consumptions and efficiencies of laser beam welding (LBW) with other major welding processes. It discusses the two modes of laser welding: conduction-mode welding and deep-penetration mode welding. The article reviews the factors of process selection and procedure development for laser welding. The factors include power density, interaction time, laser beam power, laser beam diameter, laser beam spatial distribution, absorptivity, traverse speed, laser welding efficiency, and plasma suppression and shielding gas. The article concludes with a discussion on laser cutting, laser roll welding, and hybrid laser welding.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005638
EISBN: 978-1-62708-174-0
... for more details.) Penetration (keyhole-mode) laser welding occurs when laser power density is above the vaporization threshold for the parent material ( Fig. 1 ). Penetration (keyhole) welding is accomplished when the focused beam achieves a power density greater than the critical value (∼10 6 W/cm 2...
Abstract
This article reviews weld quality monitoring considerations for two automotive materials, steel and aluminum, with a focus on photosensor technology. It provides an overview of the process description, process parameters, and weld characteristics of laser welding. The article discusses real-time or in-process monitoring, which is done with optical, acoustic, and/or charged-particle sensors. It highlights the advantages, applications, and selection criteria of weld monitoring system and concludes with examples of laser weld monitoring in the production of tailor-welded blanks.
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001481
EISBN: 978-1-62708-173-3
... the heat source for high-energy-density welding, one first needs to determine the type of welding process being formulated. Depending on the weld parameters, high-energy-density welding can simulate either a conduction-mode weld process or a keyhole weld process. If a strict conduction-mode weld process...
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005641
EISBN: 978-1-62708-174-0
..., such as aluminum and copper, Nd:YAG, disc, and fiber lasers have better coupling, especially for conduction-mode welding, because of their shorter wavelength (1.06 μm). When conduction-mode welding of all materials, and even in keyhole welding of reflective material, care should be taken to prevent reflected...
Abstract
This article provides an overview of the fundamentals, mechanisms, process physics, advantages, and limitations of laser beam welding. It describes the independent and dependent process variables in view of their role in procedure development and process selection. The article includes information on independent process variables such as incident laser beam power and diameter, laser beam spatial distribution, traverse speed, shielding gas, depth of focus and focal position, weld design, and gap size. Dependent variables, including depth of penetration, microstructure and mechanical properties of laser-welded joints, and weld pool geometry, are discussed. The article also reviews the various injuries and electrical and chemical hazards associated with laser beam welding.
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001370
EISBN: 978-1-62708-173-3
.... It provides information on the applications of microwelding with pulsed solid-state lasers. The article describes the modes of laser welding such as conduction-mode welding and deep-penetration-mode welding, as well as major independent process variables for laser welding, such as laser-beam power, laser-beam...
Abstract
Laser-beam welding (LBW) uses a moving high-density coherent optical energy source, called laser, as the source of heat. This article discusses the advantages and limitations of LBW and tabulates energy consumption and efficiency of LBW relative to other selected welding processes. It provides information on the applications of microwelding with pulsed solid-state lasers. The article describes the modes of laser welding such as conduction-mode welding and deep-penetration-mode welding, as well as major independent process variables for laser welding, such as laser-beam power, laser-beam diameter, absorptivity, and traverse speed. It concludes with information on various hazards associated with LBW, including electrical hazards, eye hazards, and chemical hazards.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005639
EISBN: 978-1-62708-174-0
... (∼10 W). Because highly focusable beam power sources (single-mode fiber lasers and small electron beam welders) of up to ∼1 kW are presently available, quite fast travel speeds should be energetically possible. At 1 kW, still assuming a cubic fusion zone 100 μm on a side and its energy requirement...
Abstract
Microjoining with high energy density beams is a new subject in the sense that the progress of miniaturization in industry has made the desire to make microjoints rapidly and reliably a current and exciting topic. This article summarizes the current state of microjoining with both electron and laser beams. It considers the elementary physical processes such as heat and fluid flow to introduce the reader to the phenomena that affect melting, coalescence, and solidification needed for a successful microweld. The various forces driving (and resisting) fluid flow are analyzed. The article discusses the equipment suitable for microjoining and the metallurgical consequences and postweld metrology of the process. It also provides examples of developmental welds employing laser and electron beam microwelding techniques.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005615
EISBN: 978-1-62708-174-0
... instantaneous local melting and vaporization of the workpiece material. This high power density characteristic can lead to keyhole formation. Keyhole-mode welding distinguishes EBW (and other high energy density processes) from other welding methods. Principles of Operation To illustrate the nature...
Abstract
This article introduces the operating principles and modes of operation for high-vacuum (EBW-HV), Medium-vacuum (EBW-MV), and nonvacuum (EBW-NV) electron beam welding. Equipment, process sequence, part preparation, process control, and weld geometry are described for electron beam welding. Advantages are described in terms of welding near heat sensitive components or materials and producing deep penetration or shallow welds with the same equipment.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005573
EISBN: 978-1-62708-174-0
..., the isotherms will degenerate into surfaces that are parallel to the welding x -direction, as shown in Fig. 2 ( Ref 1 ). Conduction of heat will then occur exclusively in the directions normal to the x -axis, meaning that the mode of heat flow becomes essentially two-dimensional (i.e., restricted to the y...
Abstract
This article reviews the classical models for the pseudo-steady-state temperature distribution of the thermal field around moving point and line sources. These include thick- and thin-plate models and the medium-thick-plate model. The analytical solutions to the differential heat flow equation under conditions applicable to fusion welding are provided. The article also provides an overview of the factors affecting heat flow in a real welding situation using the analytical modeling approach because this makes it possible to derive relatively simple equations that provide the required background for an understanding of the temperature-time pattern.
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005552
EISBN: 978-1-62708-174-0
... energy densities. The PAW process is capable of operating in either mode, depending on the current at which welding is being performed. Figure 15 schematically compares the melt-in (or conduction) and keyhole modes of welding for the PAW process, as an example. Fig. 15 Schematic illustration...
Abstract
This article overviews the classification of welding processes and the key process embodiments for joining by various fusion welding processes: fusion welding with chemical sources for heating; fusion welding with electrical energy sources, such as arc welding or resistance welding; and fusion welding with directed energy sources, such as laser welding, electron beam welding. The article reviews the different types of nonfusion welding processes, regardless of the particular energy source, which is usually mechanical but can be chemical, and related subprocesses of brazing and soldering.