TIG welding common welding consumables produces high quality welds and beautiful weld shapes. However, when welding thicker plates and pipes, the welding penetration is small and the welding productivity is low. Coating a layer of special active agent on the surface of the workpiece to be welded for TIG welding can increase the penetration depth and reduce the penetration width, which is the so-called A-TIG welding. This paper studies the influence of three different active agents on the TIG welding of a 20# steel thick-walled pipe with a thickness of ,https://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=53483826&type=,https://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=53483833&type=,https://html.publish.founderss.cn/rc-pub/api/common/picture?pictureId=53483829&type=,2.00000000,2.22033930,3.175,54 mm×8 mm. The results showed that the appearance quality of the joint with No. 3 active agent was the best, followed by No. 2 active agent, and the worst with No. 1 active agent. The penetration depths of the three active agents are all greater than 8 mm, and the penetration depth increases are all above 3.211 mm. Thick-walled pipes without active agent cannot be welded through. For the samples welded with No. 2 active flux, the average width of the front side of the weld is 8.639 mm and the average width of the back side is 7.621 mm. The effect of increasing the penetration depth is the most obvious. The microstructure of 20# steel pipe base metal is ferrite and pearlite. The structure of the heat-affected zone of the joint is larger than that of the base metal, and the grains in the weld zone are further grown. At the austenite grain boundary, acicular coarse proeutectoid ferrite is produced, and the main structure is still a mixture of pearlite and ferrite, and a small amount of upper bainite and lath martensite. The tensile specimens with three active agents all fractured on the base material, and the weld strength was higher than that of the base material.
active agentTIG weldingpenetrationmicrostructuremechanical properties