Titanium has the characteristics of low density, high specific strength, corrosion resistance, high elasticity, low damping, non-magnetism and good high and low temperature performance. It is known as “space metal” and “ocean metal” and is widely used in aerospace, seawater desalination, and ships. , chemical industry, automobile, electric power and many other fields of national economy and national defense construction. Due to the low yield of seamless pipes, long production cycle and high cost, while the production process of pure titanium welded pipes is short, low production cost and high production efficiency, vigorously developing thin-walled welded pipes has become a trend in today’s pipe production. In Japan, Europe and the United States, titanium and titanium alloy thin-walled seamless pipes are gradually being replaced by titanium welded pipes. They are used in condensers and condensers in Binhai power stations and nuclear power plants, which not only improves the heat exchange efficiency, but also improves the efficiency of the condenser. And the service life of the condenser unit, the economic benefits are significant.
When welding titanium pipes, you must ensure:
(1) The metal in the welding area is not contaminated by active gases N, 0, H and harmful impurity elements C, Fe, Mn, etc. above 250°C.
(2) Coarse grain structure cannot be formed.
(3) Large welding residual stress and residual deformation cannot be generated. Therefore, the welding process must follow the predetermined construction sequence, strictly follow the process quality management standards, and implement quality control throughout the entire process. The factors of human, machine, material and method are all under good control, so as to ensure the welding quality of titanium pipes within a reasonable construction period.
The burst pressure of the titanium welded pipe was 61.76MPa. A small crack appeared in the longitudinal weld of the titanium welded pipe, and the water in the pipe burst out from the weld. Seamless titanium pipe: The burst pressure was 68.10MPa. A large crack appeared at the connection between the pressure test plug and the pipe. The water in the pipe burst out from the connection between the pipe and the plug. The seamless pipe itself was not damaged. During the use of titanium tube heat exchangers, condensers, condensers, etc., vibrations induced by the shell-side fluid cause vortices, buffeting, elastic excitation and acoustic resonance of different fluids. These oscillations combine to form severe vibrations. , which causes the pipe to continuously hit the baffle, causing the pipe to be cut and penetrated by the edge of the baffle, and the connection between the pipe and the tube sheet to be stretched to leak. Therefore, fatigue vibration tests were conducted on titanium welded pipes and titanium seamless pipes, and the fatigue times of titanium welded pipes and titanium seamless pipes under the same conditions were counted to determine whether replacing titanium seamless pipes with titanium welded pipes would have an impact on the service life of the equipment.
(1) Expansion properties of welded titanium pipes: Under the same expansion pressure, the pull-off force of welded titanium pipes is 2.5-3.1MPa greater than that of seamless titanium pipes. After expansion, the welded titanium pipes are combined with the expansion tooling. Tighter, the expansion joint has better airtightness.
(2) The welded titanium pipe can withstand the maximum design pressure of 35MPa within the defined range of the pressure vessel and maintain the pressure for 3 minutes without leakage.
(3) Titanium welded pipe and titanium seamless pipe at frequency 30.
The principles and processes for rolling welded titanium pipes are the same as those for seamless titanium pipes. However, the presence of weld beads requires additional factors to be considered in order to determine the best and most stable roll expansion process. Among these factors, the most important are the metallurgical quality and surface condition of the pipe. For example, where it is desired to use pipe in the annealed rather than welded condition, excessively protruding filler beads must be avoided for tight-fit connections in tubesheet designs. It has been demonstrated that air-annealed flared pipes with polished rings on the head The bonding strength is better than that of tubes expanded in the bright annealed or bright stress relief annealed state.
On the other hand, rough tube surface or tube sheet surface can improve mechanical strength, but has poor sealing performance. The surface finish of the titanium tube plate holes manufactured by precision machining or machining and hinged tube plate holes is 0.75-1.5-101, and the finish of the tube head polishing ring also reaches the same level, so that the strength and sealing properties can be optimally matched. .