Welding of Tube Sheet of Titanium Tube Heat Exchanger
Published by Publisher: Changyi new mateDate: 4/18/2026 2:13:37 PM Read: During assembly, use acetone to carefully clean oil, water and impurities on the surface of the tube and orifice plate. The requirements for the orifice plate are that the aperture is 0.5mm larger than the tube diameter to ensure clearance. Before welding, strictly clean the site to reduce the content of iron ions in the air. Secondly, carefully clean the welding equipment, and then thoroughly clean the surface of the workpiece with sandpaper and acetone and dry it. The time interval between cleaning and welding shall not exceed 2 hours. After drying, wipe it with white silk cloth before welding can be carried out. Strengthen on-site wind prevention measures to enhance the protection effect. In order to ensure uniform protection of the third welding area, first carefully check whether each outlet hole on the welding gun nozzle is smooth, and 4 - 5 layers of fine copper mesh have been covered around the holes to achieve uniform air flow protection. In order to improve the cooling speed and shorten the residence time at high temperatures, so as to obtain good protection, taking advantage of the characteristics of pure copper that absorbs heat quickly and the characteristics of titanium and titanium alloys that do not melt in other metals (except silver). In order to achieve the purpose of rapid cooling, more than 20 pure copper rods with a diameter of 20 mm x 50mm were processed, and a 4 mm x 20mm hole was drilled in the center of both ends of the copper rod. The main reason is that during the welding process, the copper rod inserted into the titanium pipe end quickly absorbs heat and is dissipated into the space in time through the small holes. Accelerate the cooling rate of the three areas of titanium welding. In addition, the small holes also make it easy to enter and exit (the copper rod extends into the titanium tube to a depth of 1mm). In addition to absorbing heat and cooling, pure copper also plays a blocking and protective role. Because titanium has low thermal conductivity and poor heat dissipation, small welding process parameters are selected to reduce heat input, appropriately extend the residence time of the molten pool, and reduce the generation of air holes. In order to improve the protection effect of the welding pool, the arc should be started for more than 5 seconds in advance, and the gas should be stopped for more than 10 seconds after extinguishing. During welding, the included angle between the welding gun and the tubesheet in the front-to-back direction is 75�~85�, and the included angle between the tungsten electrode and the tube wall is 0�~15�. The arc is started on one side of the welding plate. When the first droplet is melted on the weld, normal welding is started, and the arc is generally lowered to about 2mm to improve the protection effect and increase the penetration depth. The arc extinguishing should be put on a copper rod, and the air supply should be continued for more than 10 seconds after extinguishing the arc to achieve good protection and cooling. In order to prevent overheating and deformation of the tubesheet and facilitate heat dissipation and cooling, dispersed and symmetrical welding is adopted. During the welding process of the tube sheet of titanium tube heat exchanger, through continuous exploration, the following experience was summed up: Since the fluidity of titanium after melting is quite good, which is higher than that of other metals except silver, when welding in all positions, it is recommended to start the arc at 1 o'clock, and weld it counterclockwise to 11 o'clock. Use high-frequency arc extinguishing to increase the arc extinguishing frequency to prevent molten droplets from flowing too fast, affecting the welding quality and the appearance of the weld, and avoiding uneven thickness of the weld. When extinguishing the arc, it should pass the arc starting point 4~ 6mm and extinguish the arc on the copper rod to prevent the formation of arc pits. To sum up, in the tube-sheet welding of titanium tube heat exchangers, it is effective to choose a large nozzle water-cooled welding gun and take advantage of the fast heat absorption characteristics of pure copper rods to speed up the cooling speed of the weld seam. The process measures and operating methods adopted ensured the overall welding quality of the titanium tube heat exchanger, achieved good results and achieved significant economic benefits.
