The mechanism of penetration increase in A-TIG welding

doi:10.1007/s11706-011-0125-5

Front Mater Sci

2011, Vol. 5

Issue (2) : 109-118 https://doi.org/10.1007/s11706-011-0125-5

RESEARCH ARTICLE

The mechanism of penetration increase in A-TIG welding

Rui-Hua ZHANG¹(

), Ji-Luan PAN¹, Seiji KATAYAMA²

1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China; 2. Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

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Abstract

The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux we developed for stainless steel. The effect of flux on the flow and temperature fields of weld pool is simulated by the PHOENICS software. It shows that without flux, the fluid flow will be outward along the surface of the weld pool and then down, resulting in a flatter weld pool shape. With the flux, the oxygen, which changes the temperature dependence of surface tension grads from a negative value to a positive value, can cause significant changes on the weld penetration. Fluid flow will be inward along the surface of the weld pool toward the center and then down. This fluid flow pattern efficiently transfers heat to the weld root and produces a relatively deep and narrow weld. This change is the main cause of penetration increase. Moreover, arc construction can cause the weld width to become narrower and the penetration to become deeper, but this is not the main cause of penetration increase. The effects of flux on fluid flow of the weld pool surface and arc profiles were observed in conventional TIG welding and in A-TIG welding by using high-speed video camera. The fluid flow behavior was visualized in real-time scale by micro focused X-ray transmission video observation system. The result indicated that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration could be apparently identified in the case of A-TIG welding. The flux could change the direction of fluid flow in welding pool. It has a good agreement with the simulation results.

Keywords A-TIG welding penetration increase numerical simulation X-ray high-speed video camera

Corresponding Author(s): ZHANG Rui-Hua,Email:zrh@lut.cn

Issue Date: 05 June 2011

Cite this article:

Rui-Hua ZHANG,Ji-Luan PAN,Seiji KATAYAMA. The mechanism of penetration increase in A-TIG welding[J]. Front Mater Sci, 2011, 5(2): 109-118.

URL:

https://academic.hep.com.cn/foms/EN/10.1007/s11706-011-0125-5
https://academic.hep.com.cn/foms/EN/Y2011/V5/I2/109

Fig.1 The application of flux.

Fig.2 Macrostructure of Type 304 stainless steel welded joints (12-mm-thick): without flux (TIG); with flux (A-TIG).

Fig.3 Fusion zone shape of welded and simulated for TIG welding.

Fig.4 Temperature and velocity field without activating flux.

Fig.5 Temperature and velocity with activating flux.

Fig.6 Fusion zone shape of welded and simulated for A-TIG welding.

Fig.7 The compare of fluid flow fields without and with flux.

Fig.8 X-ray transmission in-situ imaging system.

Fig.9 Images showing arc constriction (argon shielding): without flux; with flux.

Fig.10 Images showing arc constriction (helium shielding): without flux; with flux.

Fig.11 Observation results of molten pool surface and tracer during TIG welding.

Fig.12 Observation results of molten pool surface and tracer during A-TIG welding.

Fig.13 Observation results of tungsten particle behavior: without flux; with flux.

Fig.14 Schematic of melt flows inside molten pool: without flux; with flux.

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