Effects of shielding gas hydrogen content on the arc behavior in gas tungsten arc welding
- Colorado School of Mines, Golden, CO (United States); and others
The primary role of the shielding gas in gas tungsten arc welding (GTAW) is to protect the weld pool and tungsten electrode from the oxygen and nitrogen in the surrounding atmosphere. Traditionally inert gases such as argon and helium have been used, either as pure gases or mixed with each other. However, additions of small amounts of hydrogen have been reported to improve weld bead penetration and enable higher welding speeds to be used. The present work was performed to investigate the effect of small hydrogen additions on the arc behavior in GTAW, and to further the fundamental understanding of the effect of shielding gas on arc characteristics. GTAW bead-on-plate welds were made on 12.5 mm x 150 mm x 75 mm Type 304 stainless steel test coupons. The welding current, voltage, and their variations were continuously monitored during welding. After welding, each test coupon was sectioned and prepared using standard metallographic techniques and etched in Vilella`s etch for macroexamination of the weld bead cross section. Bead width, depth, and cross-sectional area were measured using a LECO image analysator system. The influence of hydrogen content in an argon has tungsten arc was characterized. The electrical behavior of the arc, including the arc resistance, was measured as a function of current and hydrogen content. A better fundamental understanding of arc behavior and energy transfer was achieved using these experimental gas mixes. The results allow the following conclusions to be drawn: (1) Small additions of hydrogen in the argon based shielding gas in gas tungsten arc welding significantly change the weld bead geometry due to changes in the arc column. (2) Selection of the right argon, hydrogen shielding gas mixture to give the optimum arc column characteristics for a given condition can improve weld quality and increase productivity. (3) The resistance of the arc column was found to be an adequate parameter to describe the arc column behavior.
- OSTI ID:
- 115466
- Report Number(s):
- CONF-9404233-; TRN: 95:002927-0044
- Resource Relation:
- Conference: 75. American Welding Society (AWS) annual meeting, Philadelphia, PA (United States), 10-15 Apr 1994; Other Information: PBD: 1994; Related Information: Is Part Of 75th Diamond anniversary American Welding Society annual meeting; PB: 273 p.
- Country of Publication:
- United States
- Language:
- English
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