Porosity formation in laser welding - Mechanisms and suppression methods

Matsunawa, Akira; Kim, Jong-Do; Katayama, Seiji

doi:10.2351/1.5059740

Cited by 27 publications

(13 citation statements)

References 1 publication

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“…About 20 years after the first trial of the animated Xray transmission image, Matsunawa et al took the in situ X-ray transmission image of the keyhole during CO 2 laser welding. [56][57][58] This is the first trial to observe the keyhole during laser welding. The principle of the equipment was almost the same as that of Fujisawa et al, but they used a microfocused X-ray with a minimum window diameter of 10 mm (normal: 100 mm) to gain a high spatial resolution and a high framing rate.…”

Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

“…Using this technique, they clearly showed the keyhole behaviour and porosity formation process during the CO 2 laser welding of an aluminium alloy and carbon and stainless steels. [56][57][58] They revealed that bubbles were intermittently formed mainly at the keyhole tip. Most of the bubbles are trapped at the solidified wall, and then the porosity is formed.…”

Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

“…Laser power modulation is one of the methods. 56,67,68 The earlier work to apply the power modulation was carried out by Otto et al 69 They revealed that the optimum laser power modulation could stabilise the welding phenomenon and obtain a constant penetration depth. The authors applied the laser power modulation to prevent the porosity.…”

Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

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High speed imaging technique Part 2 – High speed imaging of power beam welding phenomena

Tsukamoto¹

2011

Science and Technology of Welding and Joining

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The high speed imaging technique is an attractive tool to elucidate welding phenomena. In this paper, applications of this technique are reviewed in order to understand the power beam welding phenomenon. Monochromatic imaging technique, which can take pictures of plasma with any specific spectrum wavelength, is used to analyse state of the laser induced plasma and distribution of some species, such as ions and atoms of gases and metals. During electron beam welding, intermittent melting process and spiking phenomenon can be clearly recorded by a pinhole X-ray streak camera. The in situ X-ray transmission imaging system is useful to observe the dynamic keyhole and fluid flow behaviour, which cannot be directly observed by any other method. High speed observations of the solidification front clearly show the solidification cracking process. In the present paper, methods to analyse the solidification cracking using high speed imaging are also described.

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Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

Section: Observation Of Keyhole and Fluid Flow By In Situ X-ray Trans...mentioning

confidence: 99%

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High speed imaging technique Part 2 – High speed imaging of power beam welding phenomena

Tsukamoto¹

2011

Science and Technology of Welding and Joining

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“…The first reported work on X-ray transmission imaging of welding dynamics was in electron beam welding by Arata et al in 1976 [34]. Later, intensive investigations on keyhole formation [35], keyhole collapse [36], and keyhole porosity formation [37] have been conducted by the laser group in Osaka University around 2000s. Figure 11 shown the X-ray transmission imaged keyhole melt flow by tracing tungsten particle and porosity formation during laser welding [38].…”

Section: In Suit X-ray Imagingmentioning

confidence: 99%

Progress on Experimental Study of Melt Pool Flow Dynamics in Laser Material Processing

Xiao¹,

Lu²,

Fu³

et al. 2021

Liquid Metals

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Laser material processing has becoming a rapid developing technology due to the flexibility of laser tool. Melt pool is the main product from the interaction between laser and material and its features has a great impact on the heat transfer, solidification behavior, and defects formation. Thus, understanding changes to melt pool flow is essential to obtain good fabricated product. This chapter presents a review of the experimental studies on melt pool flow dynamics for laser welding and laser additive manufacturing. The mechanisms of melt pool convection and its principal affecting factors are first presented. Researches on melt flow visualization using direct and indirect experimental methods are then reviewed and discussed.

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“…An unstable keyhole is another source for porosity formation during the laser welding process of different alloys [21,23,24]. However, the possibility of the formation of these defects is less for magnesium alloys [4,9].…”

Section: Introductionmentioning

confidence: 99%

Mitigation of Pore Generation in Laser Welding of Magnesium Alloy AZ31B in Lap Joint Configuration

Harooni

Kong

Carlson

et al. 2012

Volume 3: Design, Materials and Manufacturing, Parts A, B, and C

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Magnesium, as the lightest structural metal, has been widely used in the automotive and aerospace industries. Porosity is the main issue in the welding of magnesium alloys and can be caused by surface coatings, hydrogen gas, pre-existing porosity, the collapse of an unstable keyhole and vaporization of alloying elements. In this study, the effect of the oxide layer on pore generation in the welding of AZ31B-H24 magnesium alloy is investigated. A fiber laser with a power of up to 4 kW is used to weld samples in a lap joint configuration. Two groups of samples are studied: as received (AR) surfaces (where an oxide layer remains on the surface) and treated surfaces. The surface treatment includes two techniques: mechanical removal (MR) and the use of a plasma arc (PA) as a preheating source. Also, a separate set of experiments are designed for preheating samples in a furnace in order to investigate whether the pore mitigation effect of a plasma arc is caused by preheating. Observations include a weld bead profile achieved through optical microscopy, chemical compositions tested by Electron Dispersive Spectroscopy (EDS), and mechanical properties measured with a tensile test. The results obtained show that the preheating effect of a plasma arc procedure can effectively mitigate pore generation. The tensile-shear results reveal that PA samples have a higher strength than other groups of samples.

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Porosity formation in laser welding - Mechanisms and suppression methods

Cited by 27 publications

References 1 publication

High speed imaging technique Part 2 – High speed imaging of power beam welding phenomena

High speed imaging technique Part 2 – High speed imaging of power beam welding phenomena

Progress on Experimental Study of Melt Pool Flow Dynamics in Laser Material Processing

Mitigation of Pore Generation in Laser Welding of Magnesium Alloy AZ31B in Lap Joint Configuration

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