ABSTRACT Keyhole gas tungsten arc welding (K-GTAW) was applied to characterize the weld bead geometry in case of the 6 mm thick electrolytic tough pitch copper. Various conditions of welding speeds and preheating on the bead geometry were studied for its uniformity. Visual examination, macro bead dimensional analysis, microhardness profile across the transverse section, microstructural analyses were performed to investigate the K-GTAW on electrolytic tough pitch copper. The results revealed that full penetration of 6 mm can be obtained in a single pass using keyhole mode in GTAW. Keyhole length and width were majorly affected by the welding speed and preheating temperature. Significant variations in weld bead geometry were observed even when high heat input conditions were applied without preheating. Uniform weld bead geometry of 5 mm bead width and depth to width ratio of 0.42 was obtained for a length of 80 mm using appropriate preheating of 300°C and heat input condition of 1.37 kJ/mm (resulted from 300 amperes welding current, 120 mm/min welding speed, and 15.3 volts voltage). In the uniform weld bead geometry, the weld and heat affected zones were consisted of coarse grains relative to base material, wherein the micro hardness variations were observed.

中文翻译：

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用匙孔钨极氩弧焊加工铜以保证焊道几何形状的均匀性

摘要 锁孔钨极气体保护焊 (K-GTAW) 用于表征 6 毫米厚电解韧铜的焊道几何形状。研究了焊道几何形状的焊接速度和预热的各种条件的均匀性。进行了目视检查、宏观焊道尺寸分析、横断面的显微硬度分布、微观结构分析，以研究电解韧铜上的 K-GTAW。结果表明，在 GTAW 中使用钥匙孔模式可以在单次通过中获得 6 毫米的完全穿透。小孔的长度和宽度主要受焊接速度和预热温度的影响。即使在没有预热的情况下应用高热输入条件时，也观察到焊道几何形状的显着变化。使用适当的 300°C 预热和 1.37 kJ/mm 的热输入条件（由 300 安培焊接电流产生，120 mm /min 焊接速度和 15.3 伏电压）。在均匀焊道几何形状中，焊缝和热影响区由相对于母材的粗晶粒组成，其中观察到显微硬度变化。