When assembled, acetone is used to carefully clean the oil, water and impurities on the surface of the pipe and plate. For the hole plate requirements, the aperture is greater than 0.5 mm diameter of the tube, guaranteed clearance. Before welding, strictly clean up the site, reduce the content of iron ion in the air, then carefully clean the welding equipment, then thoroughly clean the workpiece surface with sandpaper, acetone and dry, after cleaning to welding time interval of no more than 2 H, after drying white silk cloth to clean the welding. Reinforce on-site wind protection measures to enhance the protective effect. In order to ensure the uniform protection of welding zone 3, first carefully check whether the holes on the nozzle of the torch are open, 4 ~ 5 layers of fine copper net have been added to the surrounding holes to achieve uniform protection of air flow. In order to improve the cooling speed, shorten the stay time at high temperature and thus be well protected, taking advantage of the fast heat absorption of pure copper, titanium and titanium alloys do not melt to other metals(other than silver) for the purpose of rapid cooling, more than 20 pure copper rods of 20 mm x 50 mm have been processed, and the hole of 4 mm x 20 mm has been drilled in the center of the two ends of the copper rods. This is mainly due to the rapid absorption of heat from the copper rods inserted into the titanium tube during the welding process and the timely release of the holes into space to accelerate the cooling speed of the three areas of the titanium metal welding. In addition, the hole also makes it easy to get in and out(copper rod extends into titanium tube depth 1mm). Pure copper not only acts as heat absorption cooling, but also acts as blocking protection. Because of the low thermal conductivity and poor heat dissipation of titanium, small welding parameters are chosen to reduce heat input, extend the residence time of the molten pool and reduce stoma. In order to improve the protection effect of welding pool, more than 5s should be fed in advance and more than 10s delayed after arc quenching. For welding, the angle between the welding gun and the pipe plate is 75 ° to 85 °The angle between the tungsten pole and the pipe wall is 0 ° 15 ° The arc is introduced on one side of the welding plate. When the first drop melts on the weld, it starts to weld normally, and the arc is generally about 2mm low, thus increasing the protection and depth. To put out the arc on the copper rod, after putting out the arc to continue to gas more than 10 S to achieve good protection and cooling purposes. In order to prevent the tube plate from overheating and deformation, and to facilitate cooling, decentralized symmetric welding is adopted. In the course of welding the titanium tube heat exchanger plate, the following experience is concluded through continuous exploration: due to the excellent fluidity of titanium after melting, which is higher than that of other metals except silver, it is recommended to start the arc at 1 o'clock in the whole position and to weld the arc counterclockwise to 11 o'clock in the high frequency extinction arc.

Increase the arc-extinguishing frequency, prevent the droplet flow too fast, affect the welding quality and weld appearance shape, avoid the weld thickness uneven. Turn out the arc point between 4 and 6 mm, and put out the arc on the copper rod to prevent arc pit. In conclusion, in the welding of titanium pipe heat exchanger, the method of using large nozzle water-cooled welding gun to accelerate the welding speed is effective. The technology measures and operation methods used to ensure the overall welding quality of titanium tube heat exchangers, obtained good results and obtained significant economic benefits.