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keyhole instability

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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
... porosity compared with identical welds in other heats of material. 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-illuminated x-ray films to show that the beam location...
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
... the surface. In some cases, instability in the molten pools leads to material ejection and results in a pore forming at the bottom of the pool. This pore is then trapped and solidified beneath the surface ( Ref 19 ). Keyhole pores vary in shape and range in size from 10 to 50 μm. Pores that are not...
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. High-velocity gas motion occurs in and around the arc during welding. The gas motion is partially due to cover gas...
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
... 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 of a partial-penetration HLAW...
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
... 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 and formation and...
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
... such instabilities is to use the procedure called Tikhonov's regularization, which modifies the least-square norm by the addition of a term having a regularization parameter and a whole-domain zero th -order regularization term ( Ref 128 ). Instabilities in the solution can be alleviated by proper...
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
... higher-atomic-number elements), but the energy-transfer efficiency for the electron beam is considerably higher than for a laser beam of comparable intensity. With a sufficiently energetic beam (laser or electron), a keyhole may develop in the weld fusion zone; in macrowelds, the laser beam may reflect...
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
.... Moreover, the slow stable crack extension prior to fracture makes it difficult to determine the maximum stress-intensity level at crack instability because the crack length is uncertain. The R -curve analysis ( Ref 9 ) is applicable for determining K c for intermediate-strength materials where the...
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: 6A
Publisher: ASM International
Published: 31 October 2011
DOI: 10.31399/asm.hb.v06a.a0005572
EISBN: 978-1-62708-174-0
... contact tip while maintaining a consistent electrical contact point. Hesitation in wire feeding or variation in the contact point can create arc variations and instabilities. To achieve consistent operation, the contact tip hole is slightly larger than the wire diameter being used. The wire sliding...
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
... the decomposition of the electrode covering, without pressure, and with filler metal from the electrode. Table 10 shows suggested procedures for the SMAW of aluminum. Fig. 20 Plasma arc welding process showing constriction of the arc by a copper nozzle and a keyhole through the plate...
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
.... This is a frequent problem if exact beam position cannot be controlled, either because 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...
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: 8
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.hb.v08.9781627081764
EISBN: 978-1-62708-176-4
Book Chapter

Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003241
EISBN: 978-1-62708-199-3
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001444
EISBN: 978-1-62708-173-3
... welding, the electron beam must pierce at least the upper tiers in such a way that the molten metal flows in behind the advancing beam, as in keyholing. The molten weld metal is held in place by the combined forces of capillarity, surface tension, and viscosity. Welding conditions must be carefully...
Series: ASM Handbook
Volume: 20
Publisher: ASM International
Published: 01 January 1997
DOI: 10.31399/asm.hb.v20.9781627081948
EISBN: 978-1-62708-194-8
Series: ASM Handbook
Volume: 6
Publisher: ASM International
Published: 01 January 1993
DOI: 10.31399/asm.hb.v06.a0001403
EISBN: 978-1-62708-173-3
... the types of materials used in automotive applications. Coated steels complicate the laser welding process, because the off-gassing of the lower-boiling-point material interferes with the maintenance of the weld keyhole. Once this keyhole is broken, the weld must be restarted, resulting in inferior...
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003509
EISBN: 978-1-62708-180-1
... the assessment of high-work-hardening materials when the level 2 approach has proved too restrictive or when a tearing instability analysis is required. The fracture assessment model adopted in the level 3 approach requires extensive material characterization data, including details of the stress...