Investigations into Flux-Free Plasma Brazing of Aluminum in a Local XHV-Atmosphere

Klett, Jan; Bongartz, Benedict; Viebranz, Vincent Fabian; Kramer, David; Hao, Chentong; Maier, Hans Jürgen; Hassel, Thomas

doi:10.3390/ma15238292

Cited by 3 publications

(1 citation statement)

References 33 publications

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“…It hinders the wetting of the filler metal, preventing proper capillary action, required to fill the gaps between the joined materials. As a result, the aluminum oxide layer disrupts the diffusion process with the base material (Klett et al, 2022). Therefore, it is necessary to remove this layer before brazing.…”

Section: Introductionmentioning

confidence: 99%

Measurement Methods for Flux Residue Quantity after Controlled Atmosphere Brazing of Aluminum Coolers

NADOLNY,

Hamrol,

Rogalewicz

et al. 2023

Management and Production Engineering Review

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The Controlled Atmosphere Brazing (CAB) process together with NOCOLOK flux is associated with the occurrence of potassium fluoroaluminate residue inside the cooler. Excess of this flux residue is known to cause gelation of the coolant, which deteriorates the efficiency of the cooler. The flux residue amount is most often measured via Atomic Absorption Spectroscopy (AAS), in accordance with DIN ISO 9964-3. This is a time-consuming measurement that requires the use of specialized equipment and costly solvents. The following article presents two innovative methods for flux residue measurement after CAB process. They include Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) and Reflected Light Microscopy (RLM) with Differential Interference Contrast (DIC) module. The accuracy of these methods has been compared to the reference AAS method to evaluate their potential as alternative, less expensive, and quicker measurement methods for determining the quantity of flux residue.

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Section: Introductionmentioning

confidence: 99%

Measurement Methods for Flux Residue Quantity after Controlled Atmosphere Brazing of Aluminum Coolers

NADOLNY,

Hamrol,

Rogalewicz

et al. 2023

Management and Production Engineering Review

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Effect of silane-doped argon shielding gases for gas metal arc welding of S355

Treutler,

Neef,

Wesling

2024

Weld World

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The welding of steel grades relies primarily on the interaction of the weld metal with doped oxygen components of the shielding gas. This mainly serves to decrease the viscosity and reduce the surface tension of the melt in order to achieve an adjusted material transition. Interference with the ambient atmosphere is undesirable in this context. In order to prevent material-related changes in the microstructure, slag initiators are admixed which promote the precipitation of low-density oxides on the weld seam surface. Manufacturing technology is increasingly striving to eliminate the interaction of atmospheric oxygen in the production process. It is primarily intended to counteract the negative effects of oxygen during manufacturing. For this objective, silane-doped gases for subtractive manufacturing processes and additive manufacturing via the PBF-LB/M process have been considered. Small amounts of silane in conventional inert shielding gases allow partial pressures of oxygen that are comparable to a high vacuum. In the scope of this publication on investigations for welding applications, blind welds on S355 substrate plates were performed using G3Si1 filler material. In addition to the recommended M21, an argon shielding gas with 1.5% silane doping and argon 4.6 are applied for welding. Apart from the observation of the resulting energy input, the weld seams are metallographically characterized. For this purpose, the formation of silicates on the weld seam surface and the development of the weld seam within the base material are investigated. The volume of the weld seam is reduced as a result of the silane doping compared to the M21 application. The composition of the weld metal is significantly influenced by the silane content, leading to an increased manganese content in particular. The silane doping results in an intensified formation of an acicular bainitic structure and an accompanying hardening within the weld metal.

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Plasma Welding of Aluminum in an Oxygen-Free Argon Atmosphere

Klett

Bongartz

Wolf

et al. 2023

Advances in Materials Science

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Plasma welding is characterized by a high concentration of energy, which allows for high welding speed and leads to less distortion and residual stresses compared to conventional welding processes. Due to the local and controlled heat input, the process is suitable for sheet metal from ≈ 0.1 mm (micro plasma) up to ≈ 10 mm. In the case of aluminum and its alloys, the natural aluminum oxide layer on the metal surface limits the productivity of the plasma welding process. The electrically isolating and thermally insulating Al2O3 layer has a significantly higher melting point compared to the aluminum (T m(Al2O3) = 2072 °C vs. T m(Al) = 660 °C). The oxide layer hinders the formation of a stable arc and can even impede the joining formation. In order to remove the oxide layer and to produce quality welds with a DC process, it is necessary to weld with reverse polarity to use the principle of cathodic surface cleaning. However, this leads to increased electrode wear and increased penetration depth, which is not always desirable. In the study presented, the use of silane to reduce the oxygen content in the welding atmosphere as well as to remove the natural aluminum oxide layer on the metal surface was investigated. As previous studies have shown that the use of silane-doped plasma-gases is suitable for removing the superficial oxide layer on aluminum components, high-quality welded joints were expected. Quality welds with sufficient dilution were achieved using a transferred arc silane-doped helium plasma. In contrast, welding with an argon-silane mixture led to excessive pores formation. Additionally challenges to stabilize the arc process were identified and ramifications with respect to process optimization are discussed.

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Investigations into Flux-Free Plasma Brazing of Aluminum in a Local XHV-Atmosphere

Cited by 3 publications

References 33 publications

Measurement Methods for Flux Residue Quantity after Controlled Atmosphere Brazing of Aluminum Coolers

Measurement Methods for Flux Residue Quantity after Controlled Atmosphere Brazing of Aluminum Coolers

Effect of silane-doped argon shielding gases for gas metal arc welding of S355

Plasma Welding of Aluminum in an Oxygen-Free Argon Atmosphere

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