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keyhole instability

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Published: 31 October 2011
Fig. 10 Schematic showing keyhole instability. (a) Keyhole is formed by heat generated by electron beam. (b) Maximum penetration that can be produced by heat flow. (c) Liquid cools, causing impending collapse of displaced metal. The keyhole is filled by a lump of cooling material at the end More
Image
Published: 01 January 1993
Fig. 10 Schematic showing keyhole instability. (a) Keyhole is formed by heat generated by electron beam. (b) Maximum penetration that can be produced by heat flow. (c) Liquid cools, causing impending collapse of displaced metal. The keyhole is filled by a lump of cooling material at the end More
Image
Published: 30 November 2018
Fig. 1 Schematic of keyhole instability in laser beam welding. (a) Full development of keyhole and balance of forces. (b) Initial perturbation of keyhole through instability at rear molten wall. (c) Collapse of keyhole, entrapping metallic vapor within the root. (d) Reestablishment of full More
Series: ASM Handbook
Volume: 2A
Publisher: ASM International
Published: 30 November 2018
DOI: 10.31399/asm.hb.v02a.a0006490
EISBN: 978-1-62708-207-5
... fluidity of the molten pool. This article schematically illustrates the keyhole instability in LBW and describes the process details of LSW. Representative macrographs of butt, lap, and fillet welds produced using the LBW and LSW processes are presented. The article discusses the laser welding technologies...
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
... very high porosity compared with identical welds in other heats of material. Instability in Keyhole Fluid Flow In addition to the steady-state flow of liquid around the keyhole, significant instability in the fluid motion has been seen. For example, Mara et al. ( Ref 15 ) used side-view, self...
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
.... Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds. Mass Transport in the Arc High-velocity gas motion occurs in and around the arc during welding. The gas motion is partially due...
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
...-penetration HLAW occurs when welding in penetration mode but not fully penetrating through the joint thickness. Partial-penetration HLAW is highly susceptible to internal weld porosity due to instability at the root of the keyhole. Porosity caused by keyhole instability is typically seen in the bottom half...
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
... by acoustic frequencies generally less than 10 kHz. Hence, the core of acoustic emission (100 Hz to 20 kHz) relating to vaporization, plasma formation, instability, and mass motion of the melt pool in the keyhole is typically analyzed with quality monitoring ( Ref 9 ). The action of the molten pool...
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...
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
..., and the momentum of the evaporated metal atoms creates a reaction force that depresses the surface of the melt and may be sufficient to cause the formation of a cavity, or keyhole. With the formation of this cavity, the displaced liquid must flow elsewhere, often resulting in a raised crown around the molten-zone...
Series: ASM Handbook
Volume: 24
Publisher: ASM International
Published: 15 June 2020
DOI: 10.31399/asm.hb.v24.a0006557
EISBN: 978-1-62708-290-7
... parameters specific to the alloy system and selected processing technique. This article discusses the formation of defects within metal additive manufacturing, namely fusion-based processes and solid-state/sintering processes. Defects observed in fusion-based processes include lack of fusion, keyhole...
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005329
EISBN: 978-1-62708-187-0
Series: ASM Handbook
Volume: 19
Publisher: ASM International
Published: 01 January 1996
DOI: 10.31399/asm.hb.v19.a0002398
EISBN: 978-1-62708-193-1
... superior toughness. Charpy Impact Toughness Charpy impact toughness is the most common measure of toughness with several types of specimen configurations such as the V-notch or keyhole specimen. The loss in toughness at lower temperatures is more distinct in Charpy V-notch data as compared...
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005572
EISBN: 978-1-62708-174-0
.... Excessively long arc length can cause porosity, spatter, undercut, and poor weld shape when welding out of position. Reduced arc length tends to produce a narrower bead with a higher crown. Insufficient voltage can result in excessive short circuiting, arc instabilities, and spatter. Travel Speed...
Series: ASM Handbook
Volume: 2A
Publisher: ASM International
Published: 30 November 2018
DOI: 10.31399/asm.hb.v02a.a0006515
EISBN: 978-1-62708-207-5
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.a0005689
EISBN: 978-1-62708-176-4
... by rubbing against another of the material. of energy than for ductile fracture. body. See also fretting. compressive stress. A stress that causes an elas- Charpy test. An impact test in which a tic body to deform (shorten) in the direction of buckling. A compression phenomenon that oc- V-notched, keyhole...
Series: ASM Handbook
Volume: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.9781627081764
EISBN: 978-1-62708-176-4
Series: ASM Handbook
Volume: 24
Publisher: ASM International
Published: 15 June 2020
DOI: 10.31399/asm.hb.v24.9781627082907
EISBN: 978-1-62708-290-7
Series: ASM Handbook
Volume: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005614
EISBN: 978-1-62708-174-0
... of beam instability, magnetism of the parts, or excessive tolerances in tool fixtures. Shrinkage stresses are better managed in radial welds, as shown in Fig. 2 . The volume of molten metal is less constrained by the axial direction if the gear hub is allowed to move by using push fit...
Series: ASM Handbook
Volume: 20
Publisher: ASM International
Published: 01 January 1997
DOI: 10.31399/asm.hb.v20.a0005751
EISBN: 978-1-62708-194-8
... instability in or nitride, or a mixture of compound of such which failure occurs by unstable lateral deflec- materials; that is, it includes anions that play as a panel, plate, pipe, or other shape) that is tion due to compressive forces applied to the important roles in atomic structures and prop- built up...