Numerical Simulation of the Mechanism for Penetration
Increasing of A-TIG Welding

ZHANG Ruihua¹  YIN Yan1  FAN Ding¹  KATAYAMA S J ²

(1. State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050;
2. JWRI, Osaka University, Osaka 567-0047, Japan)

Abstract: The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux developed by ourselves 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 causation of penetration increasing. And arc shrinking can cause the weld width to become narrower and the penetration to become deeper, but arc shrinking not the main causation of penetration increasing. The simulation results of the weld pool shape accord with the experiment results well.

Key words: A-TIG welding Activating flux Penetration increasing PHOENICS

CLC No: TG401

甘肃省自然科学基金资助项目(0710RJZA064). Received 20070609 , received in revised form 20071224

References

[1] HOWSE D S, LUCAS W. Investigation into arc constriction by active fluxes for tungsten inert gas welding[J]. Science and Technology of Welding and Joining, 2000, 15(3): 189-193.
[2] YANG Chunli, USHIO Masao, TANAKA Manabu. Detection of surface tension and effect of surface active flux in TIG welding [J]. Chinese Journal of Mechanical Engineering, 2000, 36(10): 59-63.
[3] SIMONIK A G. The effect of contraction of the arc dis-charge upon the introduction of electronegative elements[J]. Svar. Proiz., 1976 (3): 68-71.
[4] HEIPLE C R, ROPER J R. Surface active element effects on the shape of GTA, laser and electron beam welds[J]. Welding Research Supplement, 1983(3): 72-77.
[5] AIDUN D K , MARTIN S A. Effect of Sulfur and oxygen on weld penetration of high-purity austenitic stainless steels[J]. Mater. Eng. and Performance, 1997, 6(4): 496-506.
[6] ZHAO Yuzhen, LEI Yongping, SHI Yaowu. Effects of surface-active elements surfur on flow patterns and depth/width ratio of welding pool [J]. Chinese Journal of Mechanical Engineering, 2004, 40(9): 138-143.
[7] ZHANG R H, FAN D. Numerical simulation of effects of activating flux on flow patterns and weld penetration in ATIG welding[J]. Science and Technology of Welding and Joining, 2007, 12(1): 15-23.
[8] WANG Y, SHI Q, TSAI H L. Modeling of the effects of surface-active elements on flow pattern and weld penetration[J]. Metallurgical and Materials Transactions B, 2001, 32(2): 145-161.
[9] SAHOO P, DEBROY T. Surface tension of binary metal-surface active solute systems under conditions relevant to welding metallurgy[J]. Metall. Trans., 1987, 19B(6): 483-491.
[10] ZHANG Ruihua, FAN Ding, YU Shurong. Study activating flux for mild steel [J]. Transactions of the China Welding Institution, 2003, 24(2): 16-18.
[11] DONG C, KATAYAMA S. Basic understanding of A-TIG welding process[C]//The 57th Annual Assembly of the International Institute of Welding, Osaka, 2004: 371-382.
[12] ZHANG Ruihua, FAN Ding. Activating electron beam welding[J]. Chinese Journal of Mechanical Engineering, 2004, 40(2): 132-135.
[13] ZHANG Ruihua. Study of activating welding and numerical simulation of mechanism of weld penetration in-creased by flux[D]. Lanzhou: Lanzhou University of Technology, 2005.
[14] ZHANG R H, FAN D, KATAYAMA S. Electron beam welding with activating flux[J]. Transactions of JWRI, 2006, 35(1): 19-22.