A method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tubes

Abstract

The present invention provides a method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded pipes, comprising the following steps: S1: processing and treatment of the sealing plate and the area to be connected of the flange; S2: preparation of the flange, a connection structure is set at one end of the flange for connecting a pressure device; S3: welding the two ends of the thin-walled titanium welded pipe to the connection surfaces of the sealing plate and the flange respectively, and the wall thickness of the thin-walled titanium welded pipe is 0.3-1mm; S4: heat treatment of the titanium welded pipe after welding; S5: connecting one end of the flange away from the titanium welded pipe to the pressure device for pressure testing of the titanium welded pipe. The present invention sets a sealing plate and a flange as a seal and a connector of the thin-walled titanium welded pipe, connects the thin-walled titanium welded pipe to the sealing plate and the flange through a reasonable welding process and a post-heat process, facilitates the pressure bearing performance test of the thin-walled titanium welded pipe, solves the problem of difficulty in connecting the thin-walled titanium welded pipe to the pressure device, has high reliability, and effectively reduces the test cost.

Description

Technical Field

[0001] The invention relates to the technical field of titanium material processing, and in particular to a method for connecting a tube sheet and testing the pressure bearing performance of a thin-walled titanium welded tube. Background Art

[0002] Titanium materials have outstanding advantages such as excellent corrosion resistance, high specific strength and non-magneticity. The titanium welded pipes prepared by welding cold-rolled titanium strips have the advantages of corrosion resistance, erosion resistance, short production process, low cost and high efficiency. They are used to prepare heat exchangers, condensers, evaporators and transmission pipelines and other equipment. They have compact and efficient structure, high heat exchange efficiency, not easy to scale, acid and alkali corrosion resistance, long service life, small equipment size and weight, and are widely used in seawater desalination, coastal power stations, petrochemicals, nuclear power, ships and marine chemical industries.

[0003] Titanium is characterized by poor thermal conductivity and large heat capacity. During welding, the grain growth tendency of the weld and heat-affected zone is obvious, and coarse-grained structure is easily formed. Welding defects such as cracks, inclusions and pores may also be formed in the weld, resulting in a decrease in the plasticity and fracture toughness of the welded joint. There is a high degree of fluctuation near the weld of the titanium welded pipe prepared by the self-melting welding process. Generally, the inner weld has a small amount of excess height and the outer weld has a slight depression. The melting zone of the welded pipe is an uneven casting structure. The organization of the melting zone and the heat-affected zone is significantly different from the matrix of the titanium material; in addition, forming and welding cooling will increase the internal stress in the titanium welded pipe. These factors may affect the fatigue performance, corrosion resistance and pressure bearing capacity of the titanium welded pipe. Among the various performance tests on titanium welded pipes, the pressure bearing capacity test is more difficult, because titanium welded pipes are smooth pipes, which need to be sealed and connected to relevant devices before pressure testing; therefore, in actual use, titanium welded pipes are often required to be connected to tube sheets, etc., but due to the very active chemical properties of titanium, it is very easy to react with other elements and compounds at high temperatures. When titanium is directly welded with iron or aluminum, brittle and hard compounds will be generated, resulting in performance deterioration; in addition, since the wall thickness of thin-walled titanium welded pipes is relatively thin, and it is easy to absorb nitrogen, hydrogen, oxygen and other elements during welding, causing pollution and performance deterioration, the connection and pressure bearing performance testing of titanium welded pipes are more difficult, and there are few pressure testing methods and process regulations for titanium welded pipes.

[0004] Publication number: CN102175531B discloses a hydraulic destruction device for testing the circumferential performance of a large thin-walled cylindrical part of a titanium alloy, including a force reducing cylinder connected to a first support ring and a second support ring, a second flange arranged on the upper end face of the second support ring and the two are detachably connected, a first flange arranged on the lower end face of the first support ring and the two are detachably connected, a titanium alloy cylinder to be tested is sleeved on the outside of the force reducing cylinder, the upper end of the titanium alloy cylinder to be tested is diagonally welded to the first flange, and the lower end of the titanium alloy cylinder to be tested is diagonally welded to the second flange, the force reducing cylinder, the first support ring, the first flange, the titanium alloy cylinder to be tested, the second flange and the second support ring constitute a closed liquid chamber cavity, and the upper end face of the force reducing cylinder is symmetrically opened with an exhaust hole and a water inlet hole. The device designs a set of complex connectors to form a closed chamber for testing the pressure bearing performance of titanium welded pipes, and the parts have high geometric accuracy requirements and are difficult to process.

[0005] Therefore, there are difficulties in the pressure test of 0.3-1 mm thin-walled titanium welded pipe in the prior art. Summary of the invention

[0006] In view of this, the present invention aims to propose a method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tubes, so as to achieve the purpose of pressure bearing testing of 0.3-1 mm thin-walled titanium welded tubes.

[0007] In the prior art, there are two methods for connecting the titanium welded pipe and the pressure device in the pressure bearing performance test of the titanium welded pipe: first, one end of the outer diameter of the titanium welded pipe is directly threadedly connected to the pressure device, and the other end is sealed with a sealing device; second, both ends of the titanium welded pipe are sealed with seals and then connected to the pressure device.

[0008] However, these two methods are not suitable for testing the pressure bearing performance of thin-walled titanium welded pipes. When the diameter of the titanium welded pipe is between 0.3mm and 1mm, the titanium welded pipe wall is too thin, and the pressure bearing capacity of the titanium welded pipe is limited during mechanical processing. It is easy to produce indentations and pits, and deformation occurs. It is impossible to process the thin-walled titanium welded pipe by processing the outer diameter thread, which also affects the pressure bearing capacity of the titanium welded pipe. Conventional sealing parts, such as rubber gasket seals and O-ring seals, are not reliable under extreme working conditions such as high pressure, and there is a problem of easy failure, which affects the pressure test results; while metal gasket seals have high production costs and high technical requirements during installation, and the flatness of the gasket and the contact surface must be ensured.

[0009] In order to solve the sealing problem in the existing thin-walled titanium welded pipe pressure performance test, the present invention designs a new sealing structure and adopts a reasonable welding process to enhance the weld quality of the test piece, avoid welding defects in the welding process of the thin-walled titanium welded pipe, eliminate the internal stress of the test piece after welding, so that the test piece does not affect the original mechanical properties of the titanium welded pipe, and facilitates the pressure performance test of the thin-walled titanium welded pipe.

[0010] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0011] A method for tube-sheet connection and pressure bearing performance testing of a thin-walled titanium welded tube comprises the following steps:

[0012] S1: Processing and treatment of the sealing plate and flange to be connected;

[0013] S2: Preparation of flange, a connection structure is set at one end of the flange for connecting the pressure device;

[0014] S3: Weld the two ends of the thin-walled titanium welded pipe to the connection surfaces of the sealing plate and the flange respectively, and the wall thickness of the thin-walled titanium welded pipe is 0.3-1mm;

[0015] S4: Heat treatment of titanium welded pipe after welding;

[0016] S5: Connect the end of the flange away from the titanium welded pipe to the pressure device to perform a pressure test on the titanium welded pipe.

[0017] Furthermore, in step S1, a groove is provided on the end surface of the sealing plate with the axis of the end surface of the sealing plate as the center, and the bottom diameter of the groove is larger than the diameter of the titanium welded pipe.

[0018] Furthermore, in step S1, the cross section of the sealing plate is circular, the axial cross section of the groove is conical, the angle between the side wall of the groove and the axis is acute, and the opening angle of the two side walls of the groove is θ.

[0019] Furthermore, in step S1, the end face diameter of the sealing plate is 5-70 mm larger than the diameter of the titanium welded tube; the end face thickness of the sealing plate is 3-30 mm, the opening angle θ ranges from 40° to 170°, and the surface finish of the groove is not less than 12.5 μm.

[0020] Furthermore, in step S1, the sealing plate and the flange are made of pure titanium.

[0021] Further, in step S2, the flange includes a flange plate and a flange gasket, one end of the flange gasket is connected to the flange plate, the flange gasket is a hollow tube, and the outer diameter of one end of the flange gasket away from the flange plate is provided with an external thread for connecting a pressure device.

[0022] Furthermore, the outer diameter D1 of the flange is 40-150mm, the thickness is 5-50mm, and the diameter D2 of the center hole is 5-40mm; the diameter of the flange gasket matches the size specifications of the pressing device, the flange gasket wall thickness is 2-15mm, the diameter is 10-60mm, and the length is 30-260mm; the external thread has a size of M10-60mm×1-4mm and a length of 10-40mm.

[0023] Furthermore, in step S3, the specific steps of welding are:

[0024] S31: Check the surface of the titanium welded pipe to be welded, the sealing plate and the flange end surface. If there is oil or dirt, wipe it clean with a clean white silk cloth and acetone and dry it to keep the welding area dry and clean;

[0025] S32: After cleaning, welding should be performed as soon as possible. The titanium welded pipe should be placed in the center area of ​​the sealing plate groove. Tungsten inert gas arc welding should be performed using TA1 welding wire with a diameter of 0.3-1.8 mm. Direct current positive polarity should be used to melt-fill the titanium welded pipe and the sealing plate. The nozzle diameter should be 5-30 mm, the welding current should be 5-70 A, the arc voltage should be 1-12 V, and the welding gun argon gas flow rate should be 0.5-15 L / min.

[0026] S33: Check the weld. If there is no crack in the weld, the titanium welded pipe is not burned through or has holes, and the color of the weld is silvery white, light yellow, golden yellow or partially light blue, it is qualified;

[0027] S34: If the flange end is grooved, use S32 for welding; if the flange end is not grooved, weld directly.

[0028] Furthermore, in step S4, after the titanium welded pipe is welded to the sealing plate and / or flange, annealing is performed at a temperature of 300-700°C.

[0029] Furthermore, in step S5, the specific steps of the pressure bearing performance test are:

[0030] S51: Connect the threaded titanium tube on one side of the flange to the pressure device to perform a water pressure test;

[0031] S52: During the water pressure test, the corresponding pressure when the titanium welded pipe ruptures or leaks is the maximum pressure;

[0032] S53: If leakage or rupture occurs at the connection between the sealing plate or flange end face and the titanium welded pipe, the result will be invalid. It is allowed to re-test the pressure after re-welding.

[0033] Compared with the prior art, the method for tube-sheet connection and pressure bearing performance testing of a thin-walled titanium welded tube of the present invention has the following advantages:

[0034] The present invention provides a sealing plate and a flange as a seal and a connector for the thin-walled titanium welded pipe, which is used to connect the titanium welded pipe to a pressure device and seal the zero-one port of the titanium welded pipe during a pressure performance test, thereby facilitating the pressure performance test of the thin-walled titanium welded pipe and having high reliability.

[0035] The present invention connects the thin-walled titanium welded pipe with the sealing plate and the flange through reasonable welding process and post-heat process. The sealing structure formed by welding the sealing plate and the flange can withstand extreme working condition tests such as high pressure, solves the problem of difficulty in connecting the thin-walled titanium welded pipe with the pressure testing device, avoids the problems of indentations and pits on the thin-walled titanium welded pipe and failure of the sealing device during the pressure bearing performance test, and effectively reduces the test cost.

[0036] The present invention arranges special processing for the sealing plate and the flange, and performs argon arc welding (TIG) connection with the thin-walled titanium welded pipe, so as to realize the connection between the titanium welded pipe and the titanium plate, the titanium welded pipe and the flange, and perform pressure testing on the titanium welded pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 It is a cross-sectional view of the sealing plate;

[0039] Figure 2 This is the left view of the cover plate;

[0040] Figure 3 This is the flange cross-sectional view;

[0041] Figure 4 This is a picture of the pressed sample. DETAILED DESCRIPTION

[0042] In order to make the technical means, objectives and effects of the present invention easy to understand, the embodiments of the present invention are described in detail below with reference to specific drawings.

[0043] It should be noted that all the terms used in the present invention to indicate directionality and position, such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "lower", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between the components in a certain state, and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0044] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0046] The invention discloses a method for connecting a tube sheet and testing the pressure bearing performance of a thin-walled titanium welded tube, comprising the following steps:

[0047] S1: Processing and treatment of the sealing plate and flange to be connected;

[0048] S2: Preparation of flange, a connection structure is set at one end of the flange for connecting the pressure device;

[0049] S3: Welding the two ends of the thin-walled titanium welded pipe to the connection surfaces of the sealing plate and the flange respectively;

[0050] S4: Heat treatment of titanium welded pipe after welding;

[0051] S5: Connect the end of the flange away from the titanium welded pipe to the pressure device to perform a pressure test on the titanium welded pipe.

[0052] This technical solution sets up sealing plates and flanges as seals and connectors for thin-walled titanium welded pipes, which are used to connect the titanium welded pipes to the pressure-bearing device and seal the zero and one ports of the titanium welded pipes during pressure performance tests. At the same time, the thin-walled titanium welded pipes are connected to the sealing plates and flanges through reasonable welding processes and post-heat processes, which facilitates pressure performance tests of the thin-walled titanium welded pipes.

[0053] The sealing structure formed by welding the sealing plate and the flange can withstand extreme working conditions such as high pressure testing, solves the problem of difficulty in connecting the thin-walled titanium welded pipe with the pressure device, avoids the problems of indentations and pits on the thin-walled titanium welded pipe and failure of the sealing device during the pressure performance test, has high reliability, and effectively reduces the test cost.

[0054] Specifically, in step S1, a groove is provided on the end surface of the sealing plate with the axis of the end surface of the sealing plate as the center, and the bottom diameter of the groove is larger than the diameter of the titanium welded pipe.

[0055] The diameter of the bottom surface of the groove is larger than the diameter of the titanium welded tube, so that the titanium welded tube can be inserted into the bottom of the groove, which is convenient for the titanium welded tube to be stably placed on the end face of the sealing plate and facilitates subsequent welding work; at the same time, during the welding process, the sealing material can be filled in the gap between the groove and the titanium welded tube, which is beneficial to enhance the sealing performance of the connection.

[0056] The groove arrangement not only ensures welding quality and sealing performance, but also adapts to different working conditions and simplifies the installation process.

[0057] Specifically, the end face diameter of the sealing plate is 5-70 mm larger than the diameter of the titanium welded pipe; the end face thickness of the sealing plate is 3-30 mm, the opening angle θ ranges from 40° to 170°, and the surface finish of the groove is not less than 12.5 μm.

[0058] Preferably, the cross section of the sealing plate is circular, and the end face diameter of the sealing plate is 10-50 mm larger than the diameter of the titanium welded pipe; the end face thickness of the sealing plate is 7-20 mm.

[0059] The sealing plate is set to be circular and its diameter is larger than the diameter of the titanium welded pipe, so that the sealing plate can adapt to various titanium welded pipe diameters and facilitate the welding process between the titanium welded pipe and the sealing plate; the determination of the thickness of the sealing plate ensures the strength of the overall structure and can withstand greater pressure and stress.

[0060] The sealing plate structure can ensure welding quality and sealing performance during the welding process, adapt to different working conditions and installation requirements, enhance structural strength and stability, and play an important role in optimizing stress distribution, thereby improving the performance and reliability of the entire system; at the same time, it also saves materials and reduces the weight of the device.

[0061] Preferably, the cross section of the sealing plate is square or rectangular.

[0062] This setting allows the sealing plate to be made of materials according to actual conditions, which helps to reduce the actual processing and production costs and facilitates the placement of titanium welded pipes during pressure performance testing.

[0063] Preferably, the axial cross section of the groove is conical, the angle between the side wall of the groove and the axis is acute, the two side walls of the groove have an opening angle θ, the opening angle θ ranges from 60° to 150°, and the surface finish of the groove is not less than 3.2 μm.

[0064] The groove is set to be conical with an angle of 60°-150°, which can facilitate the filling of sealing materials during welding or installation, and at the same time facilitate the smooth insertion of the titanium welded pipe into the groove, thereby improving installation efficiency. The improvement of the surface finish of the groove can enhance the contact area between the titanium welded pipe and the sealing plate, thereby helping to improve welding quality and sealing effect.

[0065] The groove structure and geometric accuracy of the device can enhance the sealing performance and welding quality of the device, facilitate the rapid installation and fixation of the titanium welded pipe to the sealing plate, and help improve the installation efficiency.

[0066] Specifically, in step S1, the end surface of the flange can cover the cross section of the titanium welded pipe.

[0067] The cross-sectional area of ​​the flange is set to be larger than the diameter of the titanium welded pipe, so that the flange can adapt to various titanium welded pipe diameters and facilitate the welding process between the titanium welded pipe and the flange.

[0068] The flange structure can ensure welding quality and sealing performance during the welding process, adapt to different working conditions and installation requirements, and improve the performance and reliability of the entire system.

[0069] Preferably, the end face of the flange is 10-50mm larger than the diameter of the titanium welded pipe; the end face thickness of the sealing plate is 7-20mm, a groove is set on the end face of the flange with the end face axis of the flange as the center, the bottom diameter of the groove is larger than the diameter of the titanium welded pipe, and the geometric size and precision of the flange groove are consistent with the groove of the sealing plate.

[0070] The flange is set to have a diameter larger than the diameter of the titanium welded pipe, so that the flange can adapt to a variety of titanium welded pipe diameters, solves the matching problem between the flange and titanium welded pipes of various diameters, and facilitates the welding process between the titanium welded pipe and the flange; the determination of the flange thickness ensures the strength of the overall structure and can withstand greater pressure and stress.

[0071] The flange structure can ensure welding quality and sealing performance during the welding process, adapt to different working conditions and installation requirements, enhance structural strength and stability, and play an important role in optimizing stress distribution, thereby improving the performance and reliability of the entire system; at the same time, it also saves materials and reduces the weight of the device.

[0072] Preferably, the flange end face may not be provided with a groove, and the flange end face is directly welded to the titanium welded pipe.

[0073] The flange end face of this configuration eliminates the groove structure, reduces the machining process, saves parts processing time and processing costs, and at the same time facilitates the flange to connect titanium welded pipes of various diameters and specifications, thereby improving the versatility and flexibility of the flange.

[0074] Specifically, in step S1, the sealing plate and the flange are made of pure titanium.

[0075] The material of the sealing plate and flange is pure titanium, which limits the chemical elements of the welding base material and avoids the generation of brittle and hard compounds by other chemical elements of the sealing plate and flange during welding, thereby causing performance deterioration and affecting the pressure performance test results of the titanium welded pipe.

[0076] Specifically, in step S2, the flange includes a flange plate and a flange gasket, one end of the flange gasket is connected to the flange plate, the flange gasket is a hollow tube, and the outer diameter of one end of the flange gasket away from the flange plate is provided with an external thread for connecting a pressure device.

[0077] One end of the flange is provided with an external thread for connecting the pressing device, so that the flange can be quickly connected to the pressing device, solving the problem of difficulty in connecting the titanium welded pipe with the pressing device.

[0078] The threaded connection structure of this setting is simple, reliable, and easy to disassemble, which helps to improve the efficiency of performance test installation, reduce production costs, and reduce the risk of failure.

[0079] Specifically, the outer diameter D1 of the flange is 40-150mm, the thickness is 5-50mm, and the diameter D2 of the center hole is 5-40mm; the diameter of the flange gasket matches the size specifications of the pressing device, the flange gasket wall thickness is 2-15mm, the diameter is 10-60mm, and the length is 30-260mm; the external thread size is M10-60mm×1-4mm, and the length is 10-40mm.

[0080] Preferably, the outer diameter D1 of the flange is 50-120mm, the thickness is 10-25mm, and the diameter D2 of the center hole is 10-30mm; the diameter of the flange gasket matches the size specifications of the pressing device, the flange gasket wall thickness is 3-10mm, the diameter is 20-50mm, and the length is 50-200mm; the external thread has a size of M20-35mm×2-3mm and a length of 15-30mm.

[0081] The specific structural dimensions of the flange can cover the diameter of existing thin-walled titanium welded pipes, solve the pressure performance test connection requirements of thin-walled titanium welded pipes during actual testing, and the flange matches the titanium welded pipe size, using less material, which helps to save material usage and reduce the weight of the device.

[0082] Specifically, the flange gasket and the flange plate are integrally formed or welded.

[0083] The flange connection form enables each manufacturer to select a processing method according to their actual conditions, helps them utilize existing materials and equipment for production, reduces restrictions on production methods, and improves the adaptability of processing methods.

[0084] Preferably, the flange gasket and the flange plate are connected by argon arc welding.

[0085] This setting uses argon gas protection for argon arc welding, which can effectively isolate oxygen, nitrogen and hydrogen in the air to avoid their adverse effects on the arc and molten pool, thereby reducing the loss of alloy elements and ensuring a dense, spatter-free and high-quality welded joint; the arc of argon arc welding burns stably, the heat is concentrated, and the arc column temperature is extremely high, which greatly improves the welding production efficiency; at the same time, its heat-affected zone is narrow, and the weldment after welding has little stress, deformation and crack tendency; argon arc welding can weld almost all types of metals, especially for some difficult-to-melt or easily oxidized metals, such as magnesium, titanium, molybdenum, zirconium and aluminum and their alloys, and performs well.

[0086] Specifically, the thin-walled titanium welded pipe has a wall thickness of 0.3-1 mm, a diameter of 5-70 mm, and a length of 50-1300 mm. The material of the titanium welded pipe is industrial pure titanium, including TA1 / Gr1 and TA2 / Gr2.

[0087] Preferably, in step S3, the diameter is 10-50 mm, the length is 100-1000 mm, and the material of the titanium welded pipe is industrial pure titanium, including TA1 / Gr1 and TA2 / Gr2.

[0088] The material grade and specific size of the thin-walled titanium welded pipe are set to help ensure the welding quality during the welding process and improve the use effect of the processing test method.

[0089] Specifically, in step S3, the specific steps of welding are:

[0090] S31: Check the surface of the titanium welded pipe to be welded, the sealing plate and the flange end surface. If there is oil or dirt, wipe it clean with a clean white silk cloth and acetone and dry it to keep the welding area dry and clean;

[0091] S32: After cleaning, welding should be performed as soon as possible. The titanium welded pipe should be placed in the center area of ​​the sealing plate groove. Tungsten inert gas arc welding should be performed using TA1 welding wire with a diameter of 0.3-1.8 mm. Direct current positive polarity should be used to melt-fill the titanium welded pipe and the sealing plate. The nozzle diameter should be 5-30 mm, the welding current should be 5-70 A, the arc voltage should be 1-12 V, and the welding gun argon gas flow rate should be 0.5-15 L / min.

[0092] S33: Check the weld. If there is no crack in the weld, the titanium welded pipe is not burned through or has holes, and the color of the weld is silvery white, light yellow, golden yellow or partially light blue, it is qualified;

[0093] S34: If the flange end is grooved, use S32 for welding; if the flange end is not grooved, weld directly.

[0094] Preferably, in step S32, tungsten inert gas arc welding is performed using TA1 welding wire with a diameter of 0.5-1.5 mm, direct current positive polarity, and the titanium welded pipe and the sealing plate are melt-filled, with a nozzle diameter of 10-20 mm, a welding current of 10-60 A, an arc voltage of 2-8 V, and a welding gun argon gas flow rate of 1-8 L / min.

[0095] In the above application scenarios, titanium welded pipes, sealing plates and flanges are pre-treated to remove contaminants and clean them with acetone to solve the problem of moisture on the surface of welding materials and melting reaction of impurity elements affecting welding quality; by setting reasonable welding process parameters and welding environment, the problem of obvious grain growth tendency in the weld and heat-affected zone during welding, easy formation of coarse-grained structure, and possible formation of welding defects in the weld, such as cracks, inclusions and pores, resulting in a decrease in the plasticity and fracture toughness of the welded joint is solved.

[0096] This welding method controls the grain growth of the weld and heat-affected zone, ensures the welding quality, and avoids the reaction of abnormal external elements with the welding material to affect the pressure-bearing performance of the titanium welded pipe; at the same time, the formulation of processes and inspection methods ensures the stability of the quality of welding products.

[0097] Specifically, in step S4, after the titanium welded pipe is welded to the sealing plate and / or flange, annealing is performed at a temperature of 300-700°C.

[0098] Preferably, the annealing temperature is 400-600°C.

[0099] In the above application scenarios, limiting the annealing temperature can eliminate the thermal stress and structural stress generated after the titanium welded pipe is welded, control the grain growth of the weld and the heat-affected zone, and ensure the pressure-bearing performance of the titanium welded pipe.

[0100] This setting helps prevent the titanium welded pipe from welding cracks or deformation due to stress concentration, enhances the load-bearing capacity and fatigue resistance of the welded joint, and improves corrosion resistance and fatigue resistance.

[0101] Preferably, the annealing environment is vacuum annealing.

[0102] The annealing environment setting can prevent the titanium welded pipe and the sealing plate and / or flange welded parts from being directly exposed to the air during annealing, avoid pollution and performance deterioration caused by the thin wall thickness of the thin-walled titanium welded pipe absorbing nitrogen, hydrogen, oxygen and other elements during annealing, and improve production efficiency.

[0103] Preferably, low temperature atmospheric annealing can be performed in special cases, with the low temperature being ≤500°C.

[0104] The annealing environment is set to control the annealing temperature to be no higher than 500°C, thereby avoiding pollution and performance deterioration caused by the absorption of a large amount of nitrogen, hydrogen, oxygen and other elements during annealing, eliminating the vacuum environment, saving energy and reducing production costs.

[0105] Specifically, in step S5, the pressure bearing performance test includes the following specific steps:

[0106] S51: Connect the threaded titanium tube on one side of the flange to the pressure device to perform a water pressure test;

[0107] S52: During the water pressure test, the corresponding pressure when the titanium welded pipe ruptures or leaks is the maximum pressure;

[0108] S53: If leakage or rupture occurs at the connection between the sealing plate or flange end face and the titanium welded pipe, the result will be invalid. It is allowed to re-test the pressure after re-welding.

[0109] This pressure bearing performance test procedure can solve various situations that may occur during the actual testing of titanium welded pipes, avoid errors in data collection, and improve the accuracy of test results; at the same time, repair welding is used to remedy leaks or cracks in welds, reducing the cost and time of parts production and effectively improving the efficiency of pressure testing.

[0110] Specifically, in step S5, the pressure bearing performance test is performed using air pressure.

[0111] The pressure-bearing performance test of the titanium welded pipe by setting up air pressure detection can solve the detection difficulties when there is a lack of water pressure detection facilities, enrich the testing means and methods, and expand the application scope of the method of the present invention.

[0112] Example 1

[0113] Welding and pressure testing of 25×0.5mmTA1 titanium welded pipe.

[0114] One end of the 25×0.5×500mmTA1 titanium welded pipe is sealed with a titanium plate and the other end is welded with a flange end. The other end of the flange is a threaded titanium pipe. The sample was tested and the O and N contents of the titanium welded pipe were 0.053% and 0.0063% respectively, the tensile strength was 325MPa, the yield strength was 252MPa, the elongation was 46%, and the flattening and expansion tests were qualified.

[0115] like Figure 1-2 As shown, the titanium round plate used for sealing welding is made of TA1 material, with a thickness of 12mm and a diameter of 50mm. A prism is processed in the center area of ​​the plate, with a bottom diameter of 27mm, an upper diameter of 35mm, and a height of 3mm; Figure 3As shown, a flange with a titanium tube is prepared by welding technology. The diameter of the flange boss is 50mm, the height is 20mm, and the inner diameter of the center hole is 15mm. The surface processing of the titanium flange uses the same method to process a prism. The connected titanium tube has a diameter of 24mm, a wall thickness of 4mm, and a length of 100mm. The external thread of the open end of the titanium tube is M24mm×2mm and a length of 15mm. The threaded titanium tube and the flange are connected together by argon arc welding, and the flange is directly welded without processing.

[0116] Clean the surface of the titanium welded tube and the titanium plate used for sealing with white silk cloth and acetone, put the titanium welded tube into the center area of ​​the prism of the titanium plate, weld it with an argon arc welder, and use TA1 welding wire with a diameter of 1mm for melting welding. When welding, first perform symmetrical spot welding, and finally use a small current and small input for full welding. The welding current is 12A, the arc voltage is 5V, and the argon gas flow rate of the welding gun is 4L / min. There are no cracks in the weld, and the titanium welded tube is not burned through or has holes. The color of the weld is silver-white and light yellow. After welding, stress relief annealing is performed at 500℃. There is slight oxidation on the surface of the titanium tube. It has been evaluated that it has no effect on the pressure test. Figure 4 shown.

[0117] The titanium welded pipe was subjected to water pressure tests at different pressures, with the water pressure values ​​being 10MPa, 15MPa, 20MPa and 30MPa, and the pressure holding time being 20s. The welded pipe did not leak or deform, indicating that the weld quality of the titanium welded pipe is reliable and the pressure bearing capacity exceeds 30MPa.

[0118] Example 2

[0119] Welding and hydrostatic testing of 48×0.5mmTA1 titanium welded pipe

[0120] The 48×0.5×300mmTA1 titanium welded pipe is sealed at one end and welded with a titanium flange at the other end, and the titanium flange has a threaded pipe. The sample was tested and the O and N contents of the titanium welded pipe were 0.051% and 0.0059% respectively, the strength was 323MPa, the yield strength was 255MPa, the elongation was 49%, and the flattening and expansion tests were qualified.

[0121] The titanium round plate used for sealing is made of TA1 material, with a thickness of 15mm and a diameter of 80mm. A prism is processed in the central area of ​​the plate, with a bottom diameter of 50mm, an upper diameter of 58mm and a height of 3mm. A flange with a titanium tube is prepared by welding technology. The flange boss has a diameter of 75mm, a thickness of 20mm and an inner diameter of the center hole of 15mm. The surface of the titanium flange is processed into a prism using the same method. The connected titanium tube has a diameter of 27mm, a wall thickness of 5mm and a length of 150mm. The external thread at the open end of the titanium tube is M27×2mm and a length of 150mm. The titanium tube for water pressure test is connected to the flange by argon arc welding, and the flange is directly welded without processing.

[0122] The titanium welded pipe and the titanium plate used for sealing welding were cleaned with white silk cloth and acetone, and the titanium welded pipe was placed in the center area of ​​the prism of the titanium plate, and welded with an argon arc welder. TA1 welding wire with a diameter of 1.5 mm was used for melting welding. Symmetrical spot welding was first performed during welding, and finally full welding was performed with a small current and small input. The welding current was 13A, the arc voltage was 5V, and the argon gas flow rate of the welding gun was 4L / min. There were no cracks in the weld, and the titanium welded pipe was not burned through or broken. The color of the weld was silvery white and light yellow. After welding, vacuum stress relief annealing was performed at 480℃.

[0123] The titanium welded pipe was subjected to different water pressure tests, and the pressure was increased until the titanium welded pipe leaked and was damaged. When the pressure exceeded 20MPa, the titanium pipe bulged and the diameter of the middle area of ​​the pipe increased. When the bursting pressure was 30MPa, a small crack appeared at the weld in the bulging area in the middle of the titanium welded pipe, and water burst out.

[0124] Example 3

[0125] Welding and hydrostatic testing of 20×0.5mmTA2 titanium welded pipe.

[0126] The TA2 titanium welded pipe with a diameter of 20mm, a wall thickness of 0.5mm and a length of 300mm is sealed with a square titanium plate at one end and welded with a flange at the other end. The flange has a threaded titanium pipe for testing. The sample was tested and the O and N contents of the titanium welded pipe were 0.11% and 0.007% respectively, with a strength of 437MPa, a yield strength of 315MPa and an elongation of 43%.

[0127] The titanium plate is made of TA2 material, with a thickness of 10mm and a side length of 40mm. A prism is processed in the center area of ​​the plate, with a bottom diameter of 21mm, an upper diameter of 30mm and a height of 3mm. A flange with a titanium tube is prepared by welding technology. The flange boss diameter is 50mm, the height is 20mm, and the inner diameter of the center hole is 15mm. The surface processing of the titanium flange uses the same method to produce a prism. The connected titanium tube has a diameter of 20mm, a wall thickness of 4mm, and a length of 100mm. The external thread of the open end of the titanium tube is M20×2mm. The titanium tube for water pressure test is connected to the flange by argon arc welding, and the flange is directly welded without processing.

[0128] Clean the surface of the titanium welded pipe and the titanium plate used for sealing with white silk cloth and acetone, put the titanium welded pipe into the center area of ​​the prism of the titanium plate, weld it with an argon arc welder, and use a TA2 welding wire with a diameter of 1mm for melting welding. When welding, first perform symmetrical spot welding, and finally use a small current and small input for full welding. The welding current is 12A, the arc voltage is 4V, and the argon gas flow rate of the welding gun is 3L / min. There are no cracks in the weld, and the titanium welded pipe is not burned through or broken. The color of the weld is silvery white and light yellow. After the titanium welded pipe is connected to the sealing plate and flange, it is vacuum annealed at 480℃ and kept warm for 40min.

[0129] During the water pressure test, the pressure was 10MPa and maintained for 3 minutes, and there was no leakage in the pipe; the water pressure was 35MPa and maintained for 3 minutes, and there was no crack in the titanium welded pipe; the water pump increased the pressure until the titanium welded pipe leaked and was damaged. When the water pressure exceeded 35MPa, bulging occurred in the middle area of ​​the titanium welded pipe. When the water pressure was 58MPa, a small crack appeared at the weld in the bulging area in the middle of the titanium welded pipe, and water burst out.

[0130] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tubes, characterized in that: The following steps are involved: S1: Processing and treatment of the sealing plate and flange to be connected; the sealing plate and flange are made of pure titanium, a groove is set on the end face of the sealing plate with the end face axis of the sealing plate as the center, and the bottom diameter of the groove is larger than the diameter of the titanium welded pipe; the axial section of the groove is conical, the angle between the side wall of the groove and the axis is an acute angle, and the opening angle θ of the two side walls of the groove is in the range of 40°-170°; S2: Preparation of flange, the flange includes a flange plate and a flange gasket, one end of the flange gasket is connected to the flange plate, the flange gasket is a hollow tube, and the outer diameter of the end of the flange gasket away from the flange plate is provided with an external thread for connecting a pressure device; S3: Weld the two ends of the thin-walled titanium welded pipe to the connection surfaces of the sealing plate and the flange respectively, and the wall thickness of the thin-walled titanium welded pipe is 0.3-1mm; S31: Check the surface of the titanium welded pipe to be welded, the sealing plate and the flange end surface. If there is oil or dirt, wipe it clean with a clean white silk cloth and acetone and dry it to keep the welding area dry and clean; S32: After cleaning, weld as soon as possible, place the titanium welded pipe in the center area of ​​the sealing plate groove, use TA1 welding wire with a diameter of φ0.5-1.5mm for tungsten inert gas arc welding, direct current positive polarity, melt-fill the titanium welded pipe and the sealing plate, nozzle diameter φ10-20mm, welding current 10-60A, arc voltage 2-8V, welding gun argon gas flow 1-8L / min; S33: Check the weld. If there is no crack in the weld, the titanium welded pipe is not burned through or has holes, and the color of the weld is silvery white, light yellow, golden yellow or partially light blue, it is qualified; S34: If the flange end is machined with a groove, use the S32 method for welding; if the flange end is not machined with a groove, weld directly; S4: Heat treatment of titanium welded pipe after welding; after the titanium welded pipe is welded with the sealing plate and / or flange, annealing is performed at a temperature of 300-700°C; S5: Connect the end of the flange away from the titanium welded pipe to the pressure device to test the pressure of the titanium welded pipe. The specific steps of the pressure performance test are: S51: Connect the threaded titanium tube on one side of the flange to the pressure device to perform a water pressure test; S52: During the water pressure test, the corresponding pressure when the titanium welded pipe ruptures or leaks is the maximum pressure; S53: If leakage or rupture occurs at the connection between the sealing plate or flange end face and the titanium welded pipe, the result will be invalid. It is allowed to re-test the pressure after re-welding.

2. The method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tube according to claim 1, characterized in that: In step S1, the cross section of the sealing plate is circular.

3. The method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tube according to claim 2, characterized in that: In step S1, the end face diameter of the sealing plate is 5-70 mm larger than the diameter of the titanium welded pipe; the end face thickness of the sealing plate is 3-30 mm, and the surface finish of the groove is not less than 12.5 μm.

4. The method for tube-sheet connection and pressure bearing performance testing of thin-walled titanium welded tube according to claim 1, characterized in that: The outer diameter D1 of the flange is 40-150mm, the thickness is 5-50mm, and the diameter D2 of the center hole is 5-40mm; the diameter of the flange gasket matches the size specifications of the pressure device, the flange gasket wall thickness is 2-15mm, the diameter is φ10-60mm, and the length is 30-260mm; the external thread of the flange gasket away from the flange has a size of M10-60mm×1-4mm and a length of 10-40mm.

Images