大直径(大于273mm)的输水、输油及输气管道的水平固定对接,用传统的上向焊(向上立焊)工艺生产效率低、返修率高;采用管道下向焊(向下立焊)技术不仅具有质量好、速度快、低消耗等优点,而且在工艺方面有如下特点:①下向焊所使用的焊条铁水浓度低、不淌渣,适合快速施焊。②电弧吹力大,而且 Large diameter (greater than 273mm) of the water, oil and gas pipe horizontal fixed butt, with the traditional upward welding (upright welding) process low production efficiency, high rework rate; the use of pipe down to the welding Welding) technology not only has the advantages of good quality, fast speed, low consumption, etc., but also has the following characteristics in the process: (1) Downward welding of the electrode with low concentration of molten iron, no slag, suitable for rapid welding. ② arc blowing force, but also