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

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1619 ◽  
Author(s):  
Shinichi Tashiro ◽  
Naoki Mukai ◽  
Yoshihide Inoue ◽  
Anthony B. Murphy ◽  
Tetsuo Suga ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Arc Welding ◽  
Gas Flow ◽  
Operating Conditions ◽  
Shielding Gas ◽  
Diffusible Hydrogen ◽  
Welding Torch ◽  
Deposited Metal ◽  
Suction Nozzle ◽  
Gas Nozzle

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.

Limitations of the Schlieren technique for shielding gas flow visualization in arc welding processes

2021 ◽  
Author(s):  
Mateus Barancelli Schwedersky ◽  
Álisson Fernandes da Rosa ◽  
Marcelo Pompermaier Okuyama ◽  
Régis Henrique Gonçalves e Silva
Keyword(s):  
Flow Visualization ◽  
Arc Welding ◽  
Gas Flow ◽  
Shielding Gas ◽  
Schlieren Technique ◽  
Welding Processes

Evaluation of the Stability and Precision of Powder Delivery during Laser Additive Manufacturing

2013 ◽  
Vol 380-384 ◽  
pp. 4348-4352
Author(s):  
Kai Zhang ◽  
Lei Wang ◽  
Xiao Feng Shang
Keyword(s):  
Laser Beam ◽  
Molten Pool ◽  
Gas Flow ◽  
Feeding Rate ◽  
Shielding Gas ◽  
Metal Parts ◽  
Deposited Metal ◽  
Computer Aided ◽  
The Stability ◽  
Powder Feeding

The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser forming is combination of five common technologies: lasers, rapid prototyping (RP), computer-aided design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing work piece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. In the LMDS process, the powder delivery system is an important component to perform the powder transport from powder storage box to powder nozzle, which supplies the raw material for the as-deposited metal parts. Consequently, the stability and precision of powder delivery during LMDS is essential to achieve the metal parts with high quality, so it is critical to evaluate the main factors closely related to the stability and precision of powder delivery. The shielding gas flow and the powder feeding rate were ascertained through experimental measure and formula calculation. The results prove that the suitable shielding gas flow and powder feeding rate can promote the stability and precision of powder delivery, which is the basis for the fabrication of as-deposited metal parts with flying colors.

A mathematical model of the arc in electric arc welding including shielding gas flow and cathode spot location

1995 ◽  
Vol 28 (9) ◽  
pp. 1840-1850 ◽  
Author(s):  
R Ducharme ◽  
P Kapadia ◽  
J Dowden ◽  
M Thornton ◽  
I Richardson
Keyword(s):  
Mathematical Model ◽  
Arc Welding ◽  
Cathode Spot ◽  
Gas Flow ◽  
Electric Arc ◽  
Shielding Gas ◽  
Electric Arc Welding

scholarly journals Numerical Simulation of Gas Flow in a Novel Torch for Reducing Diffusible Hydrogen

2019 ◽  
Vol 8 (5) ◽  
pp. 219-224 ◽  
Author(s):  
Shinichi TASHIRO ◽  
Naoki MUKAI ◽  
Yoshihide INOUE ◽  
Anthony B. MURPHY ◽  
Tetsuo SUGA ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Gas Flow ◽  
Diffusible Hydrogen

Spectroscopic Measurements of Hydrogen and Oxygen in Shielding Gas During Plasma Arc Welding

1993 ◽  
Vol 115 (1) ◽  
pp. 145-148 ◽  
Author(s):  
Q. Pang ◽  
T. Pang ◽  
J. C. McClure ◽  
A. C. Nunes
Keyword(s):  
Flow Rate ◽  
Arc Welding ◽  
Gas Flow ◽  
Plasma Arc Welding ◽  
Plasma Arc ◽  
Shielding Gas ◽  
Gas Flow Rate ◽  
Average Temperature ◽  
Welding Arc

In Situ optical spectroscopy has been used on plasma arc welded 2219 aluminum to measure both the average temperature of and the amount of hydrogen and oxygen in the welding arc. Hydrogen and oxygen levels of less than 75 ppm can be readily detected. It is shown that below a critical shield gas flow rate, the rapid invasion of atmosphere can be readily detected by this technique, and that this critical flow rate is dependent on the temperature of the arc.

scholarly journals Contamination of Coupling Glass and Performance Evaluation of Protective System in Vacuum Laser Beam Welding

2019 ◽  
Vol 9 (23) ◽  
pp. 5082
Author(s):  
Yongki Lee ◽  
Jason Cheon ◽  
Byung-Kwon Min ◽  
Cheolhee Kim
Keyword(s):  
Penetration Depth ◽  
Gas Flow ◽  
Laser Beam Welding ◽  
Nozzle Diameter ◽  
Shielding Gas ◽  
Gas Flow Rate ◽  
Contamination Index ◽  
Contaminant Dispersion ◽  
Protective System ◽  
Gas Nozzle

Vacuum laser beam welding enables deeper penetration depth and welding stability than atmospheric pressure laser welding. However, contaminated coupling glass caused by welding fumes in the vacuum space reduces laser transmittance, leading to inconsistent penetration depth. Therefore, a well-designed protective system is indispensable. Before designing the protective system, the contamination phenomenon was quantified and represented by a contamination index, based on the coupling glass transmittance. The contamination index and penetration depth behavior were determined to be inversely proportional. A cylindrical protective system with a shielding gas supply was proposed and tested. The shielding gas jet provides pressure-driven contaminant suppression and gas momentum-driven contaminant dispersion. The influence of the shielding gas flow rate and gas nozzle diameter on the performance of the protective system was evaluated. When the shielding gas flow was 2.0 L/min or higher, the pressure-driven contaminant suppression dominated for all nozzle diameters. When the shielding gas flow was 1.0 L/min or lower, gas momentum-driven contaminant dispersion was observed. A correlation between the gas nozzle diameter and the contamination index was determined. It was confirmed that contamination can be controlled by selecting the proper gas flow rate and supply nozzle diameter.

scholarly journals Influence of Cross-Wind on CO2 Arc Welding of Carbon Steel

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1677
Author(s):  
Shinichi Tashiro ◽  
Ngoc Quang Trinh ◽  
Tetsuo Suga ◽  
Natsume Matsuda ◽  
Naotaka Tsurumaru ◽  
...  
Keyword(s):  
Nozzle Exit ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Shielding Effect ◽  
Shielding Gas ◽  
Effective Parameters ◽  
Wind Resistance ◽  
Welding Torch ◽  
The Cross ◽  
Gas Flow Velocity

The purpose of this study is to develop a novel welding torch with high wind resistance, which can be used for welding outside a building under strong cross-wind. In this paper, a parametric study was carried out using different torch nozzle designs and shield gas flow rates for their optimization. The gas flow around the torch nozzle exit was visualized through the shadowgraph method to evaluate the interaction between the shielding gas flow and the cross-wind. Nitrogen fraction in a weld bead was measured for confirming the shielding effect. Furthermore, CFD simulation was also carried out for obtaining shielding gas flow velocity at the torch nozzle exit. From the result of the above experiments and simulation, effective parameters for improving the shielding effect against the cross-wind were comprehensively discussed. As a result, the nitrogen fraction was found to be decreased by increasing the averaged vertical gas velocity at the torch nozzle exit. For achieving this, it is especially effective to decrease the nozzle diameter or increase the gas flow rate.

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