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Titanium tube heat exchanger tube plate welding

When assembling, use acetone to clean oil, water and impurities on the surface of the tube and orifice plate. For hole plate requirements, the aperture is greater than the tube diameter of 0.5mm, to ensure clearance. Before welding, the site shall be strictly cleaned to reduce the content of iron ions in the air. Secondly, the welding equipment shall be carefully cleaned, and then the workpiece surface shall be thoroughly cleaned and dried with sandpaper and acetone. The time interval between cleaning and welding shall not exceed 2h, and the welding shall be cleaned with white silk cloth after drying. Strengthen the windproof measures on site to enhance the protection effect. In order to ensure the uniform protection of the three welding zones, first carefully check whether the various vents on the nozzle of the welding gun are smooth, in the surrounding holes have been covered with 4-5 layers of fine copper net, in order to achieve the purpose of uniform air flow protection. In order to improve the cooling speed, shorten the residence time at high temperature, so as to get good protection, using the characteristics of fast heat absorption of pure copper, titanium and titanium alloy do not melt in other metals (except silver), in order to achieve the purpose of rapid cooling, processing more than 20 quasi 20mmx50mm pure copper rod, and drilled 4mmx20mm holes in the center of both ends of the copper rod. The main reason is that in the welding process, the copper rod inserted into the titanium tube end absorbs heat quickly, and is timely emitted into the space by the small hole, which speeds up the cooling speed of the three areas of titanium metal welding. In addition, the small hole also makes it easy to access (the copper rod into the titanium tube depth of 1mm). Pure copper in addition to the role of heat absorption cooling, but also played a role in blocking protection. Due to the low thermal conductivity and poor heat dissipation of titanium, small welding process parameters are selected to reduce the heat input, appropriately prolong the residence time of the molten pool and reduce the porosity. In order to improve the protection effect of welding pool, the air should be sent 5s in advance, and the air should be stopped for 10s after the arc is extinguished. During welding, the Angle between the welding torch and the tube plate is 75°~85°, and the Angle between the tungsten pole and the tube wall is 0°~15°. The arc is initiated on one side of the welding plate. When the first drodrop is melted on the weld, the welding starts normally, and the arc is generally suppressed at about 2mm, so as to improve the protection effect and increase the welding depth. The arc extinguishing should be closed on the copper bar, and air should be continued for more than 10s after the arc extinguishing to achieve good protection and cooling purposes. In order to prevent the tube sheet from overheating and deformation, and to facilitate heat dissipation and cooling, disperse symmetrical welding is adopted. In the welding process of titanium tube heat exchanger tubesheet, through continuous exploration, the following experience is summarized: Because liquidity is quite good after melting, higher than that of other than silver metal, so in all position welding, suggested that at one o 'clock arc, welding counterclockwise to 11 o 'clock in the use of high frequency arc extinguishing, increase the frequency of arcing, prevent the drop flow too fast, affecting the welding quality and weld appearance, to avoid the weld its thickness unevenness. When extinguishing the arc, it should pass the starting point of 4~6mm, and extinguish the arc on the copper bar to prevent the arc pit. To sum up, it is effective to select water-cooled welding gun with large nozzle and use the characteristics of pure copper rod to accelerate the cooling speed of welding seam in the tubeplate welding of titanium tube heat exchanger. The welding quality of titanium tube heat exchanger is guaranteed by the technological measures and operation method, and good results are obtained and remarkable economic benefits are obtained.
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