Factors affecting weld root morphology in laser keyhole welding

Frostevarg, Jan

doi:10.1016/j.optlaseng.2017.10.005

Cited by 61 publications

(20 citation statements)

References 44 publications

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“…Increasing the root width and air gap can cause higher tendency to root humping or sagging due to gravity. This has been shown in single-pass LAHW of both 12-mm steel [10]. However, in case of similar fusion zone width in the root area, humping has high probability to occur.…”

Section: Testing and Characterizationmentioning

confidence: 66%

“…Underfilling and undercuts are very common in LBW where filler wire is not used. Underfilling is mostly related to melt dropouts caused by gravity effect [9,10]. The same parameters were applied with the arc added (LAHW, Weld No.…”

Section: Testing and Characterizationmentioning

confidence: 99%

“…With application of air gap, there is possibly a lower pressure inside the keyhole root and the amount of molten metal providing more favorable melt flows redirecting extra molten material to the rear part of weld pool. This requires further investigation since there is very few papers published so far with very limited explanations [10,45]. An increased air gap might reduce the pressure at the bottom of the keyhole near the exit and improve melt flow dynamics, according to the high speed imaging studies from Ilar et al [45].…”

Section: Process Stability and Weld Qualitymentioning

confidence: 99%

“…Moreover, in deep penetration welding molten metal velocities can reach > 15 m/s at the front wall of the keyhole [49,50], depending on the process parameters. Therefore, during full penetration the molten metal flow at high speeds requires substantial surface tension or strong forces for redirection [10] to prevent humping/sagging. The added arc increases the humping probability.…”

Section: Humping Mechanismmentioning

confidence: 99%

“…It was found that 1030-μm wavelength lasers have very narrow process window due to higher absorption coefficient and subsequent melt overheat in welding of carbon steels. Based on recent results, Frostevarg [10] presented that LAHW often provides humping due to unfavorable melt dynamics in the weld pool and larger root width. However, there is still many unknown factors why and how to avoid this very frequent problem in welding of thick plates.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Bunaziv

Dørum

Nielsen

et al. 2020

Int J Adv Manuf Technol

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High-power lasers are very effective in welding of plates thicker than 10 mm due to the keyhole mode. High-power intensity generates a vapor-filled cavity which provides substantial penetration depth. Due to the narrow and deep weld geometry, there is susceptibility to high hardness and weld defects. Imperfections occur due to keyhole instability. A 16-kW disk laser was used for single-pass welding of 12-to 15-mm thick plates in a butt joint configuration. Root humping was the main imperfection and persisted within a wide range of process parameters. Added arc source to the laser beam process may cause increased root humping and sagging due to accelerated melt flow. Humping was mitigated by balancing certain arc and other process parameters. It was also found that lower welding speeds (< 1.2 m/min) combined with lower laser beam power (< 13 kW) can be more positive for suppression of humping. Machined edges provided more consistent root quality and integrity compared with plasma cut welded specimens. Higher heat input (> 0.80 kJ/mm) welds provided hardness level below 325 HV. The welded joints had good Charpy toughness at − 50°C (> 50 J) and high tensile strength.

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Section: Testing and Characterizationmentioning

confidence: 66%

Section: Testing and Characterizationmentioning

confidence: 99%

Section: Process Stability and Weld Qualitymentioning

confidence: 99%

Section: Humping Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Bunaziv

Dørum

Nielsen

et al. 2020

Int J Adv Manuf Technol

View full text Add to dashboard Cite

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Application of laser-arc hybrid welding of steel for low-temperature service

Bunaziv

Akselsen

Frostevarg

et al. 2019

Int J Adv Manuf Technol

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Laser-arc hybrid welding (LAHW) is more often used in shipbuilding and oil and gas industries in recent years. Its popularity arises due to many advantages compared to conventional arc welding processes. The laser beam source is used to achieve much higher penetration depths. By adding filler wire to the process area, by means of an arc source, the mechanical properties can be improved, e.g. higher toughness at low temperatures. Therefore, LAHW is a perspective process for low temperature service. Applicability of LAHW is under concern due to process stability and mechanical properties related to heterogeneous filler wire distribution through the whole weld metal in deep and narrow joints. This can cause reduced mechanical properties in the weld root as well as problems with solidification cracking. The fast cooling rate in the root provides hard and brittle microconstituents lowering toughness at low temperatures. Numerical simulations and experimental observations showed that an increase in heat input from the laser beam is an effective way to reduce the cooling rate, such as also possible by applying preheating.

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Understanding root humping in high-power laser welding of stainless steels: a combination approach

Zhang

Liu

et al. 2020

Int J Adv Manuf Technol

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Factors affecting weld root morphology in laser keyhole welding

Cited by 61 publications

References 44 publications

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Application of laser-arc hybrid welding of steel for low-temperature service

Understanding root humping in high-power laser welding of stainless steels: a combination approach

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