Effect of CO/sub 2/ shielding gas on metal droplet formation in arc welding

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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The effect of shielding gas composition on welding performance and weld properties in hybrid CO2 laser–gas metal arc welding of carbon manganese steel

Journal of Laser Applications ◽

10.2351/1.2164481 ◽

2006 ◽

Vol 18 (1) ◽

pp. 12-20 ◽

Cited By ~ 18

Author(s):

Anna Fellman ◽

Veli Kujanpää

Keyword(s):

Co2 Laser ◽

Arc Welding ◽

Gas Metal Arc Welding ◽

Manganese Steel ◽

Gas Composition ◽

Shielding Gas ◽

Metal Arc Welding ◽

Weld Properties

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Material Flow Behavior on Weld Pool Surface in Plasma Arc Welding Process Considering Dominant Driving Forces

Applied Sciences ◽

10.3390/app10103569 ◽

2020 ◽

Vol 10 (10) ◽

pp. 3569 ◽

Cited By ~ 2

Author(s):

Manh Ngo Huu ◽

Anh Nguyen Van ◽

Tuan Nguyen Van ◽

Dang Tran Hai ◽

Thanh Nguyen Van ◽

...

Keyword(s):

Weld Pool ◽

Material Flow ◽

Arc Welding ◽

Shear Force ◽

Driving Forces ◽

Flow Behavior ◽

Shielding Gas ◽

Pool Surface ◽

Marangoni Force ◽

Weld Pool Surface

In this study, the effect of oxygen in the shielding gas on the material flow behavior of the weld pool surface was discussed to clarify the dominant driving weld pool force in keyhole plasma arc welding (KPAW). To address this issue, the convection flow on the top surface of weld pool was observed using a high-speed video camera. The temperature distribution on the surface along keyhole wall was measured using the two-color pyrometry method to confirm the Marangoni force activity on the weld pool. The results show that the inclination angle of the keyhole wall (keyhole shape) increased especially near the top surface due to the decrease in the surface tension of weld pool through surface oxidation when a shielding gas of Ar + 0.5% O2 was used. Due to the change in the keyhole shape, the upward and backward shear force compositions created a large inclination angle at the top surface of the keyhole. From the temperature measurement results, the Marangoni force was found to alter the direction when 0.5% O2 was mixed with the shielding gas. The shear force was found to be the strongest force among the four driving forces. The buoyant force and Lorentz force were very weak. The Marangoni force was stronger than the Lorentz force but was weaker than shear force. The interaction of shear force and Marangoni force controlled the behavior and speed of material flow on the weld pool surface. A strong upward and backward flow was observed in the case of mixture shielding gas, whereas a weak upward flow was observed for pure Ar. The heat transportation due to the weld pool convection significantly changed when only a small amount of oxygen was admixed in the shielding gas. The results can be applied to control the penetration ratio in KPAW.

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Effect of Shielding Gas Mixture on Gas Metal Arc Welding (GMAW) of Low Carbon Steel (LR Grade A)

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.705.250 ◽

2016 ◽

Vol 705 ◽

pp. 250-254 ◽

Cited By ~ 1

Author(s):

Yustiasih Purwaningrum ◽

Triyono ◽

M. Wirawan Pu ◽

Fandi Alfarizi

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Carbon Steel ◽

Arc Welding ◽

Gas Metal Arc Welding ◽

Low Carbon Steel ◽

Low Carbon ◽

Shielding Gas ◽

Weld Metals ◽

Metal Arc Welding

The aimed of this research is to determine the feasibility and effect of the mixture of the shielding gas in the physical and mechanical properties. Low carbon steel LR grade A in a thickness 12 mm were joined in butt joint types using GMAW (Gas Metal Arc Welding) with groove’s gap 5 mm and groove angle’s 400 with variation of shielding gas composition. The composition of shielding gas that used were 100% Ar, 100 % CO2 and 50% Ar + 50 % CO2. The measured of mechanical properties with regard to strength, hardness and toughness using, tensile test, bending test, Vickers hardness Test, and Charpy impact test respectively. The physical properties examined with optical microscope. Results show that tensile strength of welding metals are higher than raw materials. Welds metal with mixing Ar + CO shielding gas has the highest tensile strength. Hardness of weld metals with the shielding gas 100% Ar, 100 % CO2 and 50% Ar + 50 % CO2 are 244.9; 209.4; and 209.4 VHN respectively. The temperature of Charpy test was varied to find the transition temperature of the materials. The temperature that used were –60°C, -40°C, -20°C, 0°C, 20°C , and room temperature. Weld metals with various shielding gas have similar trends of toughness flux that was corellated with the microstructure of weld .

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