Research On Process And Properties Of Hot Wire TIG Welding

TIG welding methods as using of inert gas shielded, arc burning fairly stable and the weld joint is excellent, is the preferred method of welding process in high-end industrial sector welding work pieces and precision parts. However, the arc power of TIG is limited because of current-carrying capacity of its welding electrodes is finitude , and the deposition efficiency is low. Particularly welding the middle thickness of the welded structure, the need to open and multi-layer welding groove. Hot-wire TIG welding is based on cold wire TIG welding in general, adding a single hot-wire source to preheating the welding wire. The whole weld heat input does not change, but melting speed of the wire is increase so as to enhance welding productivity.The hot-wire source which supplies a constant power output is used in the test. this paper analyzes the work principle of hot-wire source with constant power output and the theoretical calculated the preheating temperature of the welding wire at different hot-wire current and wire feed rate.Using cold and hot wire welding process and H08CrMoVA wire overlaying weld on the Steel Q235 with the diameter 45mm and wall thickness of 8mm pipe by hot wire TIG bulb-tubulating machine.To change the size of welding current and hot-wire current measured under a certain current of wire feed rate to calculate deposition efficiency. While welding the main current of 120A, hot-wire current of 40A, the deposition efficiency of hot wire TIG welding increased 150% than the main current of the same cold wire TIG welding. To study the impact between main welding current and the hot-wire current on the deposition efficiency ,gradually increasing the main current and decreases hot-wire current educing that the deposition efficiency of the wire increases gradually come to the main currents is the most main factors to the deposition efficiency of wire. Fixing the main welding current, hot-wire current and welding voltage, changing welding speed to determinate the wire feed speed, an optimum match value between welding speed wire feed rate is found, that is, when welding speed is multiple of 10.32 to wire feed rate, production efficiency is the best. Observed microstructure after welding, coarse Widmanstatten structure is found in the heat-affected zone.Using cold and hot wire welding process and H08CrMoVA wire butt weld on the Steel Q235 with the diameter 42mm and wall thickness of 8mm pipe by hot wire TIG bulb-tabulating machine. Main current pulse is used in order to improve stiffness of welding arc. After timing found that hot wire TIG process is 25% faster than cold wire TIG process while welding a whole pipe to improve the production efficiency. Results of tensile tests and X-ray nondestructive testing for shows that the tensile strength of welded joints with cold and hot wire process has reached the standard of 12CrMoV base material and there is also no emergence of pores, slag and other defects in the welded joints. Coarse Widmanstatten structure does not appear in the weld microstructure of Microscopic observation.