Research and Development on the Welding Process for Reducing Diffusible Hydrogen

MUKAI, Naoki; Maruyama, Tokuji; Suzuki, Reiichi

doi:10.2207/qjjws.36.86

Cited by 9 publications

(2 citation statements)

References 6 publications

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“…Furthermore, the presence or absence of seams on a wire electrode also contributes to the amount of diffusible hydrogen in a weld bead [19]. For instance, the effectiveness of Mukai et al's [20] novel welding torch for reducing diffusible hydrogen was strongly affected by the use of a seamed flux-cored wire. Ushio et al [21] observed that the effect of Ohmic heating and arc heating on the melting rate of flux-cored wire is reduced compared to the effect on the melting rate of solid wires.…”

Section: Introductionmentioning

confidence: 99%

Effect of Flux Ratio on Droplet Transfer Behavior in Metal-Cored Arc Welding

Trinh

Tashiro

Suga

et al. 2022

Metals

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The effect of flux ratio on metal transfer behavior during metal-cored arc welding was elucidated through investigation using a standard solid wire and three metal-cored wires with flux mass ratios of (2-2) 10%, 15%, and 20%. Investigation was performed using a shadowgraph technique based on images recorded with a high-speed camera equipped with back-laser illumination. We observed that the droplet transfer frequency increased with both the welding current and flux ratio, with the effect of flux ratio being more dominant at low currents. We surmise that this is because the wire sheath area decreases as the flux ratio is increased. Hence, when the welding current is the same, a reduction in the sheath area (i.e., an increase in flux content) leads to an increase in the current density in the sheath, which enlarges the electromagnetic force at the tip of the wire and aids droplet detachment. Conversely, Joule heating is higher at high welding currents than at low currents. This increased temperature shortens the flux column inside the wire, such that the current flow into the molten droplets is more uniform. Hence, the droplet transfer frequency does not increase significantly if the flux ratio is increased in the high current range.

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Section: Introductionmentioning

confidence: 99%

Effect of Flux Ratio on Droplet Transfer Behavior in Metal-Cored Arc Welding

Trinh

Tashiro

Suga

et al. 2022

Metals

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“…This torch was based on the results of the study on the evaporation of moisture and other hydrogen sources as well as its penetration route to the weld pool. Then, the feasibility of reducing the diffusible hydrogen content during gas metal arc welding (GMAW) and FCAW was discussed [4,14]. As a result, this torch was found to be effective for both GMAW and FCAW.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Behavior of Hydrogen Source in a Novel Welding Process to Reduce Diffusible Hydrogen

et al. 2020

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This study aims to reduce the diffusible hydrogen content in deposited metal during gas metal arc welding (GMAW) and flux-cored arc welding (FCAW) which induces cold cracking. To achieve this, a novel welding torch with a dual gas nozzle has been developed. This special welding torch decreases the hydrogen source gas evaporated from a welding wire by the suction from the inner gas nozzle. In order to improve the suction efficiency of this evaporated gas, precise control of the suction gas flow is indispensable. In this paper, a simplified numerical simulation model of this process has been described. This model can take account of the evaporation of the hydrogen source gas from the wire while simulating the behavior of the shielding gas and the arc. Using this model, the effect of suction nozzle structure and torch operating conditions on suction gas flow pattern and suction efficiency was also investigated to understand the process mechanism. Furthermore, the diffusible hydrogen content in deposited metal was measured by chromatography as a validation step. Results show that some of the shielding gas introduced from a shielding nozzle was drawn inward and also branched into an upward flow that was sucked into the suction nozzle and a downward flow to a base metal. This branching height was defined as the suction limit height, which decisively governed the suction efficiency. As a result, in order to reduce the diffusible hydrogen, it was suggested that the suction limit height should be controlled towards below the wire position, where the evaporation rate of the hydrogen source gas peaks through optimization of the suction nozzle design and the torch operating conditions.

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