The Effect of Argon Pressure on the TIG Arc Welding

概要

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The effects of argon pressure on characteristics of arc, weldability of mild steel plates and mechanical properties of welded joints by the TIG welding process were investigated. As the cathode, 2% thoriated tungsten electrode of 4 mm in diameter was used. Main results obtained are summarized as follows : (1) Arc voltage V_a increases with an increasing pressure. However, V_A+V_K decreases a little with an increasing pressure from 0.1MPa to 0.6MPa. It is 8.3V under 0.1MPa and 7.3V over 0.6MPa approximately. (2) The diameter and the half width of arc decrease and the current density at the center of arc increases considerably with an increasing pressure. (3) The area of the cathode spot decreases and therefore it concentrates at the electrode tip with an increasing pressure. As the result, the erosion of tungsten tips increases. (4) Under a constant welding current, depth of penetration of mild steel increases with an increasing pressure. Therefore, the optimum current for penetration welding of thin mild steel plates decreases with pressure. (5) Relatively sound penetration welds of mild steel plates of 2 and 3.2 mm in thickness can be obtained in the pressure range up to 5.1MPa. However, meandering beads were often obtained by the fluctuated arc in the pressure range over 2.1MPa. (6) Welded joints obtained in the pressure range up to 5.1MPa have sufficient tensile strength and Charpy impact value.
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1989-10-01