Gas shielded welding method for welding seam of titanium alloy pressure vessel

Abstract

The invention belongs to the technical field of welding methods, and particularly discloses a gas shielded welding method for a welding seam of a titanium alloy pressure vessel, which comprises the following steps of: processing a groove at a joint of a barrel; cleaning the welding surface; all parts of the pressure vessel are combined, a lining ring is additionally arranged in the barrel, and the end of the lining ring abuts against the tube plate; a gap is reserved between the tube plate and the cylinder body; spot welding positioning is conducted on the groove of the barrel and the welding face of the tube plate, and the seam of the tube plate and the barrel and all the tube holes are sealed after spot welding; raising one side of the barrel, continuously filling the barrel with protective gas, and detecting the oxygen concentration in the barrel in real time until the oxygen content reaches a specified oxygen value; and the barrel and the tube plate are welded, protective gas is introduced in the whole welding process, and the protective gas needs to be continuously introduced after welding is completed. The protective gas can completely cover a welding area and a heat affected area, the oxidation risk of a welding joint in the welding process is reduced, and the welding seam quality of the titanium alloy pressure container welding joint is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding methods, and in particular relates to a gas shielded welding method for a weld of a titanium alloy pressure vessel. Background Art

[0002] Pressure vessels are closed containers that can withstand pressure. Welding is a key process in its manufacturing process, and the quality requirements for both sides of the welded joints are high. Compared with pressure vessels made of ordinary materials, if titanium alloys are used to weld pressure vessels, they will have the advantages of lighter weight, higher strength, better corrosion resistance, better biocompatibility, and good low-temperature performance. They have great application potential in high-end equipment fields such as aviation, aerospace, medical equipment, and marine engineering. In the welding process of titanium alloy materials, since titanium materials are very easy to react with oxygen, nitrogen, and hydrogen in the air at high temperatures, in order to ensure the quality of welding, it is necessary to strictly control the heat input during welding, and use inert gas to properly protect the molten pool, weld and heat-affected zone (including the back) with a temperature above 400°C. High-purity argon is usually used as a shielding gas, but in the process of pressure vessel welding, high-purity argon is difficult to completely cover the welding area and heat-affected zone, especially the back of the weld is prone to embrittlement, pores, cracks and other quality defects due to inadequate protection, resulting in unqualified performance of the welded joint. This problem has become an industry technical bottleneck restricting the application of titanium alloy pressure vessels. Summary of the invention

[0003] The object of the present invention is to provide a gas shielded welding method for a titanium alloy pressure vessel weld, which can reduce the oxidation risk of the weld joint during the welding process and improve the weld quality of the titanium alloy pressure vessel weld joint.

[0004] In order to achieve the above object, the technical solution of the present invention is: a gas shielded welding method for a weld of a titanium alloy pressure vessel, comprising the following steps:

[0005] Preparation before welding: Process the groove at the joint of the cylinder; clean the welding surface of the cylinder and the tube sheet;

[0006] Positioning treatment: Assemble the various components of the pressure vessel, add a liner inside the cylinder, and place the end of the liner against the tube sheet; leave a gap between the tube sheet and the cylinder; spot weld the groove of the cylinder and the welding surface of the tube sheet to position, and seal the joints between the tube sheet and the cylinder and each tube hole after spot welding;

[0007] Filling with protective gas: Raise the side of the cylinder away from the air pipe interface, connect the air pipe interface to the protective gas storage device, and continuously fill the cylinder with protective gas. Use a detector to detect the oxygen concentration in the cylinder in real time until the oxygen content reaches the specified value, then welding can be carried out;

[0008] Welding process: Weld the cylinder and tube sheet, and introduce protective gas throughout the welding process. After welding is completed, the protective gas should continue to be introduced until the weld cools to the specified temperature value.

[0009] Furthermore, it also includes weld inspection: judging whether the weld is oxidized based on the color of the weld surface; and inspecting the surface defects of the weld joint.

[0010] Furthermore, the pre-welding preparation also includes: when the titanium alloy plate used for cylinder forming is rolled and pressed, a layer of galvanized iron plate is placed on the surface of the titanium alloy plate.

[0011] Further, spot welding is performed on the groove of the cylinder and the welding surface of the tube sheet. The specific method is: intermittent spot welding is performed on the groove of the cylinder and the welding surface of the tube sheet, and the spacing between the welding points is 100-150mm.

[0012] Further, the cylinder and the tube sheet are welded. The specific method is: tungsten inert gas shielded arc welding is used to perform base welding, filling layer welding and cover welding on the cylinder and the tube sheet. The welding parameters used are: direct current positive connection, welding current 80-140A, welding voltage 10-14V, welding speed 7-15cm / min, and argon gas flow rate 6-15L / min.

[0013] Further, the cylinder and the tube sheet are welded, and the specific method is: the weld is symmetrically divided into N sections for welding, N ≥ 3, and each time a section is welded, it is necessary to wait for the weld to cool to a specified temperature value before welding.

[0014] Furthermore, the welding surfaces of the cylinder and the tube sheet are cleaned. The specific method is: using a physical method or a chemical method to clean the welding surface. The physical method is to use a tool to clean the welding surface; the chemical method is to use a chemical solution to clean the welding surface.

[0015] Furthermore, the tool is a fine file, an austenitic stainless steel wire brush or a milling cutter; and the chemical solution is a pickling solution.

[0016] Furthermore, the protective gas storage device is provided with a pressure detector for detecting the internal pressure of the protective gas storage device. When the pressure detector detects that the pressure drops to 0.5Mpa, the device is immediately stopped from use.

[0017] The beneficial effect of this technical solution is that the shielding gas completely covers the welding area and heat-affected zone by adding a liner to the back of the weld, continuously filling the inside with shielding gas, using a measuring instrument to detect the oxygen concentration in real time, and raising one side, thereby reducing the oxidation risk of the weld joint during the welding process and improving the weld quality of the titanium alloy pressure vessel weld joint. The problem of embrittlement, pores, cracks and other quality defects on the back of the titanium alloy pressure vessel weld due to inadequate protection during the welding process in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a gas shielded welding method for a weld of a titanium alloy pressure vessel of the present invention;

[0019] Figure 2 It is a schematic diagram of the welding interface between the cylinder and the tube sheet;

[0020] Figure 3 Schematic diagram of the pressure vessel welding structure. DETAILED DESCRIPTION

[0021] The following is further described in detail through specific implementation methods:

[0022] The reference numerals in the drawings of the specification include: cylinder 1, tube sheet 2, liner 3, air pipe interface 4, raising pier 5, and pipe hole 6.

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The embodiment is basically as shown in the attached Figure 1-3 As shown: A gas shielded welding method for the weld of a titanium alloy pressure vessel, such as Figure 1 As shown, the following steps are included:

[0025] S1: Preparation before welding, specifically:

[0026] S1.1: When the titanium alloy plate used for forming the cylinder 1 is rolled and pressed, a 0.mm thick galvanized iron plate is placed on the surface of the titanium alloy plate.

[0027] S1.2: Use a shaper to process a 45° groove at the joint of the cylinder 1. The groove can ensure the welding quality. In order to avoid heat oxidation and even combustion of the titanium alloy at the groove during machining, a larger feed amount and a lower cutting speed should be used during mechanical machining.

[0028] S1.3: Clean the welding surface of the cylinder 1 and the tube sheet 2 by physical method or chemical method. The physical method is to clean the welding surface by using tools, such as fine files, austenitic stainless steel wire brushes or milling cutters; the chemical method is to clean the welding surface by using chemical solutions, such as pickling solution.

[0029] S2: Positioning processing: Figure 2 , 3As shown, the components of the pressure vessel are assembled, and a 3mm thick titanium alloy liner 3 is added inside the cylinder 1, and the end of the liner 3 is against the tube sheet 2. A gap of 1-2mm is left between the tube sheet 2 and the cylinder 1, and 1.5mm in this embodiment. In order to reduce welding deformation, intermittent spot welding is performed on the groove of the cylinder 1 and the welding surface of the tube sheet 2 before welding, and the spacing between the welding points is 100-150mm; after spot welding, Teflon high-temperature tape is used to seal the joints between the tube sheet 2 and the cylinder 1 and each tube hole 6.

[0030] S3: Filling with shielding gas: Use a pier 5 to raise the side of the cylinder 1 away from the trachea interface 4, which can promote the rapid discharge of air in the cylinder 1; the trachea interface 4 is connected to the shielding gas storage device, and shielding gas (pure argon) is continuously filled into the cylinder 1. After filling with shielding gas for 3 hours, use a portable gas detector to detect the oxygen concentration in the cylinder 1 in real time until the oxygen content reaches the specified value of oxygen (oxygen content <0.1%), and then welding work can be carried out. The shielding gas storage device adopts a 3x4 bottle joint structure, and the shielding gas is pure argon (Ar), and the argon content is ≥99.99%. The shielding gas storage device is provided with a pressure detector for detecting the internal pressure of the shielding gas storage device. When the pressure detector detects that the pressure drops to 0.5Mpa, stop using it immediately to prevent affecting the quality of the welding joint.

[0031] S4: Welding process: The cylinder 1 and the tube sheet 2 are welded. In order to ensure the welding quality, the weld is symmetrically divided into N sections for welding, N≥3, and 6 sections in this embodiment. After each welding is completed, it is necessary to wait for the weld to cool to the specified temperature value (below 100°C) before welding to avoid excessive temperature and oxidation. Tungsten inert gas shielded arc welding (GTAW welding for short) is used to perform base welding, filling layer welding and cap welding on the cylinder 1 and the tube sheet 2. The welding parameters used are: direct current positive connection, welding current 80-140A, welding voltage 10-14V, welding speed 7-15cm / min, argon gas flow 6-15L / min. Shielding gas is introduced throughout the welding process. During the welding process, the shielding gas inside the cylinder 1 is maintained at a slightly positive pressure to the outside to ensure that the inside of the cylinder 1 is in a pure argon state. After welding is completed, the shielding gas should also be continuously introduced until the weld cools to the specified temperature value (below 100°C).

[0032] S5: Weld inspection: The staff visually inspects the color of the weld surface to determine whether the weld is oxidized; and uses the weld color flaw detection method to check the surface defects of the weld joint, and takes corresponding corrective measures for unqualified welds.

[0033] Color of weld surface Weld quality Treatment Silver qualified — Golden qualified — Light blue, blue, purple, gray Failure Clean the weld surface and adjacent oxidized metal and re-weld.

[0034] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0035] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A gas shielded welding method for a titanium alloy pressure vessel, characterized in that: The following steps are involved: Preparation before welding: processing grooves at the joints of the cylinder (1); cleaning the welding surfaces of the cylinder (1) and the tube sheet (2); Positioning treatment: assembling the various components of the pressure vessel, adding a liner (3) inside the cylinder (1), and the end of the liner (3) abutting against the tube sheet (2); leaving a gap between the tube sheet (2) and the cylinder (1); spot welding positioning is performed on the groove of the cylinder (1) and the welding surface of the tube sheet (2); after spot welding and fixing, the joint between the tube sheet (2) and the cylinder (1) and each tube hole (6) are sealed; Filling with protective gas: the side of the cylinder (1) away from the gas pipe interface (4) is raised, the gas pipe interface (4) is connected to the protective gas storage device, and the protective gas is continuously filled into the cylinder (1). The oxygen concentration in the cylinder (1) is detected in real time using a detector until the oxygen content reaches the specified oxygen value, and then welding can be carried out; Welding process: The cylinder (1) and the tube sheet (2) are welded, and a protective gas is introduced during the entire welding process. After the welding is completed, the protective gas is also continuously introduced until the weld is cooled to a specified temperature value.

2. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: It also includes weld inspection: judging whether the weld is oxidized based on the color of the weld surface; and checking for surface defects in the weld joint.

3. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: The pre-welding preparation also includes: when the titanium alloy plate used for forming the cylinder (1) is rolled and pressed, a layer of galvanized iron plate is placed on the surface of the titanium alloy plate.

4. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: Spot welding is performed on the groove of the cylinder (1) and the welding surface of the tube sheet (2). The specific method is: intermittent spot welding is performed on the groove of the cylinder (1) and the welding surface of the tube sheet (2), and the spacing between the welding points is 100-150mm.

5. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: The cylinder (1) and the tube sheet (2) are welded, and the specific method is: tungsten inert gas shielded arc welding is used to perform base welding, filling layer welding and cover welding on the cylinder (1) and the tube sheet (2), and the welding parameters used are: direct current positive connection, welding current 80-140A, welding voltage 10-14V, welding speed 7-15cm / min, and argon gas flow rate 6-15L / min.

6. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: The cylinder (1) and the tube sheet (2) are welded in the following specific method: the weld is symmetrically divided into N sections for welding, N≥3, and after each section is welded, the weld needs to be cooled to a specified temperature value before welding can be continued.

7. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: The welding surfaces of the cylinder (1) and the tube sheet (2) are cleaned. The specific method is: cleaning the welding surfaces by a physical method or a chemical method. The physical method is to clean the welding surfaces by using a tool; the chemical method is to clean the welding surfaces by using a chemical solution.

8. The gas shielded welding method for a titanium alloy pressure vessel according to claim 7, characterized in that: The tool is a fine file, an austenitic stainless steel wire brush or a milling cutter; the chemical solution is a pickling solution.

9. The gas shielded welding method for a titanium alloy pressure vessel according to claim 1, characterized in that: The protective gas storage device is provided with a pressure detector for detecting the internal pressure of the protective gas storage device. When the pressure detector detects that the pressure drops to 0.5Mpa, the device is immediately stopped from use.

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