J. Mater. Sci. Technol. ›› 2010, Vol. 26 ›› Issue (2): 170-176.

• Research Articles • 上一篇    下一篇

Weld Shape Variation and Electrode Oxidation Behavior under Ar-(Ar-CO2) Double Shielded GTA Welding

陆善平1;李殿中2   

  1. 1. 中科院金属所特种材料研究部材料制备工艺及模拟研究组
    2. 中国科学院金属研究所材料加工模拟研究部
  • 收稿日期:2008-12-03 修回日期:2009-04-25 出版日期:2010-02-28 发布日期:2010-02-28
  • 通讯作者: 陆善平

Weld Shape Variation and Electrode Oxidation Behavior under Ar-(Ar-CO2) Double Shielded GTA Welding

Shanping Lu1), Hidetoshi Fujii2),  Kiyoshi Nogi2)   

  1. 1) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Science,
    Shenyang 110016, China
    2) Joining and welding Research Institute Osaka University, Oasaka 567-0047, Japan
  • Received:2008-12-03 Revised:2009-04-25 Online:2010-02-28 Published:2010-02-28
  • Contact: Shanping Lu
  • Supported by:

    the National Science Foundation of China under Grant No. 50874101
    the Science Program of Shenyang City under Grand No. 1071275-0-02

关键词: Double shielding, weld shape, Marangoni convection, GTA welding

Abstract:

Double shielded gas tungsten arc welding (GTAW, also known as tungsten inert gas (TIG) welding) of an SUS304 stainless steel with pure inert argon as the inner layer shielding and the Ar-CO2 or CO2 active gas as the out layer shielding was proposed in this study to investigate its effect on the tungsten electrode protection and the weld shape variation. The experimental results showed that the inner inert argon gas can successfully prevent the outer layer active gas from contacting and oxidizing the tungsten electrode during the welding process. Active gas, carbon dioxide, in the outer layer shielding is decomposed in the arc and dissolves in the liquid pool, which effectively adjusts the active element, oxygen, content in the weld metal. When the weld metal oxygen content is over 70×10-6, the surface-tension induced Marangoni convection changes from outward into inward, and the weld shape varies from a wide shallow one to a narrow deep one. The effect of the inner layer gas flow rate on the weld bead morphology and the weld shape was investigated systematically. The results show that when the flow rate of the inner argon shielding gas is too low, the weld bead is easily oxidized and the weld shape is wide and shallow. A heavy continuous oxide layer on the liquid pool is a barrier to the liquid pool movement.

Key words: Double shielding, Weld shape, Marangoni convection, Gas tungsten arc welding