Quality evaluation method for vacuum brazed joint of multilayer material

Abstract

The invention relates to the technical field of brazed joint quality evaluation, in particular to a multilayer material vacuum brazed joint quality evaluation method, which can inspect all defects of a brazed joint through cooperative use of an appearance inspection method, a surface defect inspection method and an internal defect inspection method. According to the method, all defects existing on the surface of the brazed joint can be completely found out, the quality evaluation effect of the brazed joint is improved, the vacuum airtightness of the brazed joint is inspected through vacuum airtightness inspection, the situation of air leakage of the brazed joint in the using process is avoided, and the service life of the brazed joint is prolonged. Therefore, the using effect of the brazed joint is improved, and the technical problem that the using effect of the brazed joint is reduced due to the fact that the brazed joint is prone to air leakage in the using process due to the fact that an existing brazed joint quality evaluation method does not conduct vacuum airtightness inspection on the brazed joint is solved.

Description

Technical Field

[0001] The invention relates to the technical field of brazing joint quality assessment, and in particular to a method for assessing the quality of a multi-layer material vacuum brazing joint. Background Art

[0002] Vacuum brazing is a process in which the weldments that have been assembled with brazing filler metal are heated under vacuum conditions, and a series of physical and chemical reactions that are beneficial to brazing are used under vacuum conditions to achieve film removal and wetting to form brazing. Vacuum brazing has strong adaptability to materials and structures, and is commonly used for brazing of aluminum alloys, high-temperature alloys, ferroalloys, stainless steel refractory metals, structural steel and other structures, and is therefore widely used in aerospace and other fields.

[0003] After brazing, the workpiece obtained by brazing needs to be quality evaluated to determine whether the brazed joint meets the quality requirements. The existing brazed joint quality evaluation methods mostly use the naked eye or a low-power magnifying glass to detect the quality of the brazed joint surface when evaluating the quality of the brazed joint. Since the naked eye or a low-power magnifying glass cannot observe the tiny defects inside the brazed joint, the defects existing in the brazed joint cannot be completely found, thereby reducing the quality evaluation effect of the brazed joint. Therefore, through the coordinated use of appearance inspection, surface defect inspection and internal defect inspection, all defects existing in the brazed joint can be inspected, and then the defects existing on the surface of the brazed joint can be found, thereby improving the quality evaluation effect of the brazed joint.

[0004] After inspecting all defects of the brazed joint, the vacuum airtightness of the brazed joint needs to be tested. However, the existing brazed joint quality assessment method does not perform vacuum airtightness test on the brazed joint, which makes the brazed joint prone to air leakage during use, thereby reducing the use effect of the brazed joint. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the quality of vacuum brazed joints of multilayer materials, which solves the technical problem that the existing quality evaluation method for brazed joints does not perform vacuum airtightness inspection on the brazed joints, thereby making the brazed joints prone to air leakage during use, thereby reducing the use effect of the brazed joints.

[0006] To achieve the above object, the present invention provides a method for evaluating the quality of a multi-layer material vacuum brazing joint, comprising the following steps:

[0007] After the brazed joint is obtained through processing, the brazed joint is placed on a quality inspection table;

[0008] First, the quality of the surface of the brazed joint is checked with the naked eye or a low-power magnifying glass;

[0009] Afterwards, the surface defects of the brazed joint are inspected by using a surface defect inspection method;

[0010] Then, the internal defects of the brazed joint are inspected by an internal defect inspection method;

[0011] Finally, the air tightness of the brazed joint is checked by a vacuum air tightness test method, thereby completing the entire quality evaluation process of the brazed joint.

[0012] The specific method of inspecting the surface quality of the brazed joint with the naked eye or a low-power magnifying glass is as follows:

[0013] Pick up the brazed joint and observe the surface of the brazed joint with the naked eye or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times;

[0014] Observe whether the exposed end of the brazing seam of the brazed joint forms a rounded corner, whether the rounded corner is uniform, and whether there are cracks, pores and other external defects;

[0015] During the observation process, the brazed joint is continuously rotated to achieve an all-round inspection of the surface quality of the brazed joint.

[0016] Wherein, the specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0017] Sprinkle the fluorescent powder evenly on the surface of the solder joint, and place the solder joint on the quality inspection table in a dark room environment;

[0018] By utilizing the characteristic of the fluorescent powder emitting fluorescence under ultraviolet irradiation, the defects on the surface of the solder joint are exposed, thereby realizing the inspection of the surface defects of the solder joint.

[0019] Wherein, the specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0020] Clean the stains on the weld surface of the brazed joint, and then apply a layer of red colorant on the weld surface of the brazed joint;

[0021] The red stripes oozing out of the red colorant are used to display the position and shape of the defects on the surface of the solder joint, thereby realizing the inspection of the surface defects of the solder joint.

[0022] Wherein, the specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0023] Clean the stains on the surface of the brazed joint, and then evenly sprinkle magnetic powder on the surface of the brazed joint;

[0024] The magnetic field is used to generate magnetic marks on the surface of the ferromagnetic material to display the surface defects of the brazed joint, thereby realizing the inspection of the surface defects of the brazed joint.

[0025] The specific method of using the internal defect inspection method to inspect the internal defects of the brazed joint is as follows:

[0026] Move the X-ray inspection machine, Y-ray inspection machine or ultrasonic inspection machine to the quality inspection table and position it above the brazed joint;

[0027] Starting the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine, and allowing the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine to emit X-rays, Y-rays or ultrasonic waves to the brazed joint;

[0028] The internal defects of the brazed joint are inspected by using the X-ray, the Y-ray or the ultrasonic wave to inspect the pores, slag inclusions, incomplete penetration and cracks in the brazed joint and the base material of the brazed joint.

[0029] The specific method of using the vacuum airtightness test method to check the airtightness of the brazed joint is: using a water pressure test method, an airtightness test method, an air permeation test method, a kerosene permeation test method or a mass spectrometry test method to check the airtightness of the brazed joint.

[0030] The present invention provides a method for evaluating the quality of a multi-layer material vacuum brazing joint. By using a visual inspection method, a surface defect inspection method and an internal defect inspection method in combination, all defects existing in the brazing joint can be inspected, so that all defects existing on the surface of the brazing joint can be completely found, thereby improving the quality evaluation effect of the brazing joint. By using a vacuum airtightness inspection to inspect the vacuum airtightness of the brazing joint, air leakage of the brazing joint during use is avoided, thereby improving the use effect of the brazing joint. The existing brazing joint quality evaluation method solves the technical problem that the brazing joint is prone to air leakage during use due to the lack of vacuum airtightness inspection of the brazing joint, thereby reducing the use effect of the brazing joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0032] Figure 1 1 is a flowchart of a method for evaluating the quality of a multi-layer material vacuum brazing joint according to a first embodiment of the present invention.

[0033] Figure 2It is a specific flow chart of the first embodiment of the present invention for inspecting the quality of the surface of the brazed joint using the naked eye or a low-power magnifying glass.

[0034] Figure 3 It is a specific flow chart of inspecting the surface defects of the brazed joint using the surface defect inspection method according to the first embodiment of the present invention.

[0035] Figure 4 It is a specific flow chart of inspecting the internal defects of the brazed joint using the internal defect inspection method according to the first embodiment of the present invention.

[0036] Figure 5 It is a specific flow chart of inspecting the surface defects of the brazed joint using the surface defect inspection method according to the second embodiment of the present invention.

[0037] Figure 6 It is a specific flow chart of inspecting the surface defects of the brazed joint using the surface defect inspection method according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0038] Embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0039] First embodiment:

[0040] See also Figures 1 to 4 The present invention provides a method for evaluating the quality of a multi-layer material vacuum brazing joint, comprising the following steps:

[0041] S1. After the brazed joint is obtained by processing, the brazed joint is placed on a quality inspection table.

[0042] S2. First, the quality of the surface of the brazed joint is inspected with naked eyes or a low-power magnifying glass.

[0043] Specifically, the specific method of inspecting the quality of the surface of the brazed joint using the naked eye or a low-power magnifying glass is:

[0044] S21. Pick up the brazed joint and observe the surface of the brazed joint with naked eyes or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times.

[0045] S22, observing whether the exposed end of the brazing seam of the brazed joint forms a fillet, whether the fillet is uniform, and whether there are cracks, pores and other external defects;

[0046] S23. During the observation process, the brazed joint is continuously rotated to achieve an all-round inspection of the surface quality of the brazed joint.

[0047] S3. Afterwards, the surface defects of the brazed joint are inspected by using a surface defect inspection method.

[0048] Specifically, the surface defect inspection method includes fluorescence inspection, coloring inspection and magnetic particle inspection. The surface defect inspection method is used to inspect the surface defects of the braze seam that cannot be found in the brazed joint. The surface defects of the braze seam of the brazed joint include cracks and pores. Fluorescence inspection is used to inspect small brazed joints, and coloring inspection and magnetic particle inspection are used to inspect large brazed joints.

[0049] The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0050] S31, evenly sprinkle the fluorescent powder on the surface of the solder joint, and place the solder joint on the quality inspection table in a dark room environment;

[0051] S32, utilizing the property of the fluorescent powder to emit fluorescence under ultraviolet irradiation to expose the surface defects of the solder joint, thereby realizing the inspection of the surface defects of the solder joint.

[0052] S4. Then, an internal defect inspection method is used to inspect the internal defects of the brazed joint.

[0053] Specifically, the internal defect inspection method is used to inspect the pores, slag inclusions, incomplete penetration, and cracks in the brazing seam and the parent material of the brazing joint. The specific manner of inspecting the internal defects of the brazing joint using the internal defect inspection method is as follows:

[0054] S41, moving the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine onto the quality inspection table and positioning it above the brazed joint;

[0055] S42, starting the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine, and allowing the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine to emit X-rays, Y-rays or ultrasonic waves to the brazed joint;

[0056] S43, inspecting the internal defects of the brazed joint by using the X-ray, the Y-ray or the ultrasonic wave to detect pores, slag inclusions, incomplete penetration, and cracks in the brazed joint and the base material.

[0057] S5. Finally, the air tightness of the brazed joint is checked by a vacuum air tightness test method, thereby completing the entire quality evaluation process of the brazed joint.

[0058] Specifically, the specific manner of using the vacuum airtightness test method to check the airtightness of the brazed joint is: using a water pressure test method, an airtightness test method, a gas permeation test method, a kerosene permeation test method or a mass spectrometry test method to check the airtightness of the brazed joint, the water pressure test is used for high-pressure containers, the kerosene permeation test is used for non-pressure containers, and the mass spectrometry test is used for vacuum sealed joints.

[0059] Second embodiment:

[0060] Based on the first embodiment, please refer to Figure 5 The present invention provides a method for evaluating the quality of a multi-layer material vacuum brazing joint, comprising the following steps:

[0061] S1. After the brazed joint is obtained by processing, the brazed joint is placed on a quality inspection table.

[0062] S2. First, the quality of the surface of the brazed joint is inspected with naked eyes or a low-power magnifying glass.

[0063] Specifically, the specific method of inspecting the quality of the surface of the brazed joint using the naked eye or a low-power magnifying glass is:

[0064] S21. Pick up the brazed joint and observe the surface of the brazed joint with naked eyes or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times.

[0065] S22, observing whether the exposed end of the brazing seam of the brazed joint forms a fillet, whether the fillet is uniform, and whether there are cracks, pores and other external defects;

[0066] S23. During the observation process, the brazed joint is continuously rotated to achieve an all-round inspection of the surface quality of the brazed joint.

[0067] S3. Afterwards, the surface defects of the brazed joint are inspected by using a surface defect inspection method.

[0068] Specifically, the surface defect inspection method includes fluorescence inspection, coloring inspection and magnetic particle inspection. The surface defect inspection method is used to inspect the surface defects of the braze seam that cannot be found in the brazed joint. The surface defects of the braze seam of the brazed joint include cracks and pores. Fluorescence inspection is used to inspect small brazed joints, and coloring inspection and magnetic particle inspection are used to inspect large brazed joints.

[0069] The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0070] S33, cleaning the stains on the weld surface of the brazed joint, and then applying a layer of red colorant on the weld surface of the brazed joint;

[0071] S34, using the red stripes seeping out of the red colorant to display the position and shape of the defects on the surface of the brazed joint, thereby realizing the inspection of the surface defects of the brazed joint.

[0072] S4. Then, an internal defect inspection method is used to inspect the internal defects of the brazed joint.

[0073] Specifically, the internal defect inspection method is used to inspect the pores, slag inclusions, incomplete penetration, and cracks in the brazing seam and the parent material of the brazing joint. The specific manner of inspecting the internal defects of the brazing joint using the internal defect inspection method is as follows:

[0074] S41, moving the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine onto the quality inspection table and positioning it above the brazed joint;

[0075] S42, starting the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine, and allowing the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine to emit X-rays, Y-rays or ultrasonic waves to the brazed joint;

[0076] S43, inspecting the internal defects of the brazed joint by using the X-ray, the Y-ray or the ultrasonic wave to detect pores, slag inclusions, incomplete penetration, and cracks in the brazed joint and the base material.

[0077] S5. Finally, the air tightness of the brazed joint is checked by a vacuum air tightness test method, thereby completing the entire quality evaluation process of the brazed joint.

[0078] Specifically, the specific manner of using the vacuum airtightness test method to check the airtightness of the brazed joint is: using a water pressure test method, an airtightness test method, a gas permeation test method, a kerosene permeation test method or a mass spectrometry test method to check the airtightness of the brazed joint, the water pressure test is used for high-pressure containers, the kerosene permeation test is used for non-pressure containers, and the mass spectrometry test is used for vacuum sealed joints.

[0079] Third embodiment:

[0080] Based on the first embodiment, please refer to Figure 6 The present invention provides a method for evaluating the quality of a multi-layer material vacuum brazing joint, comprising the following steps:

[0081] S1. After the brazed joint is obtained by processing, the brazed joint is placed on a quality inspection table.

[0082] S2. First, the quality of the surface of the brazed joint is inspected with naked eyes or a low-power magnifying glass.

[0083] Specifically, the specific method of inspecting the quality of the surface of the brazed joint using the naked eye or a low-power magnifying glass is:

[0084] S21. Pick up the brazed joint and observe the surface of the brazed joint with naked eyes or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times.

[0085] S22, observing whether the exposed end of the brazing seam of the brazed joint forms a fillet, whether the fillet is uniform, and whether there are cracks, pores and other external defects;

[0086] S23. During the observation process, the brazed joint is continuously rotated to achieve an all-round inspection of the surface quality of the brazed joint.

[0087] S3. Afterwards, the surface defects of the brazed joint are inspected by using a surface defect inspection method.

[0088] Specifically, the surface defect inspection method includes fluorescence inspection, coloring inspection and magnetic particle inspection. The surface defect inspection method is used to inspect the surface defects of the braze seam that cannot be found in the brazed joint. The surface defects of the braze seam of the brazed joint include cracks and pores. Fluorescence inspection is used to inspect small brazed joints, and coloring inspection and magnetic particle inspection are used to inspect large brazed joints.

[0089] The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is:

[0090] S35, cleaning the stains on the surface of the brazed joint, and then evenly sprinkling magnetic powder on the surface of the brazed joint;

[0091] S36, using a magnetic field to generate magnetic marks on the surface of the ferromagnetic material to display surface defects of the brazed joint, thereby realizing inspection of surface defects of the brazed joint.

[0092] S4. Then, an internal defect inspection method is used to inspect the internal defects of the brazed joint.

[0093] Specifically, the internal defect inspection method is used to inspect the pores, slag inclusions, incomplete penetration, and cracks in the brazing seam and the parent material of the brazing joint. The specific manner of inspecting the internal defects of the brazing joint using the internal defect inspection method is as follows:

[0094] S41, moving the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine onto the quality inspection table and positioning it above the brazed joint;

[0095] S42, starting the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine, and allowing the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine to emit X-rays, Y-rays or ultrasonic waves to the brazed joint;

[0096] S43, inspecting the internal defects of the brazed joint by using the X-ray, the Y-ray or the ultrasonic wave to detect pores, slag inclusions, incomplete penetration, and cracks in the brazed joint and the base material.

[0097] S5. Finally, the air tightness of the brazed joint is checked by a vacuum air tightness test method, thereby completing the entire quality evaluation process of the brazed joint.

[0098] Specifically, the specific manner of using the vacuum airtightness test method to check the airtightness of the brazed joint is: using a water pressure test method, an airtightness test method, a gas permeation test method, a kerosene permeation test method or a mass spectrometry test method to check the airtightness of the brazed joint, the water pressure test is used for high-pressure containers, the kerosene permeation test is used for non-pressure containers, and the mass spectrometry test is used for vacuum sealed joints.

[0099] When using a multi-layer material vacuum brazing joint quality assessment method of the present embodiment, after the brazing joint is processed, the brazing joint is placed on a quality inspection table. First, the quality of the surface of the brazing joint is inspected with the naked eye or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times. Then, the surface defects of the brazing joint are inspected by a surface defect inspection method, wherein the surface defects of the brazing joint are defects on the surface of the brazing seam, and the defects on the surface of the brazing seam include defects such as cracks and pores. The surface defect inspection method includes fluorescence inspection, coloring inspection and magnetic particle inspection. Fluorescence inspection is used for the inspection of small brazing joints, and coloring inspection and magnetic particle inspection are used for the inspection of large brazing joints. Inspection, then, the internal defects of the brazed joint are inspected by an internal defect inspection method, wherein the internal defect inspection method includes X-ray inspection, Y-ray inspection and ultrasonic inspection, and the internal defects of the brazed joint include pores in the brazing seam of the brazed joint, slag inclusions, incomplete brazing, and cracking of the brazing seam and the base material, finally, the airtightness of the brazed joint is inspected by a vacuum airtightness inspection method, the vacuum airtightness inspection method includes a water pressure test, an airtightness test, an air permeation test, a kerosene permeation test and a mass spectrometry test, the water pressure test is used for high-pressure containers, the kerosene permeation test is used for non-pressure containers, and the mass spectrometry test is used for vacuum sealed joints, after the airtightness of the brazed joint is inspected, the entire quality evaluation process of the brazed joint can be completed.

[0100] In summary, the present invention can inspect all defects existing in the brazed joint through the coordinated use of the appearance inspection method, the surface defect inspection method and the internal defect inspection method, so as to completely find out all defects existing on the surface of the brazed joint, thereby improving the quality assessment effect of the brazed joint. By adopting the vacuum airtightness test to inspect the vacuum airtightness of the brazed joint, it is avoided that the brazed joint will leak during use, thereby improving the use effect of the brazed joint, and solves the technical problem that the existing brazed joint quality assessment method does not perform vacuum airtightness test on the brazed joint, which makes the brazed joint prone to air leakage during use, thereby reducing the use effect of the brazed joint.

[0101] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A method for evaluating the quality of a multi-layer material vacuum brazing joint, characterized in that: The following steps are involved: After the brazed joint is obtained through processing, the brazed joint is placed on a quality inspection table; First, the quality of the surface of the brazed joint is checked with the naked eye or a low-power magnifying glass; Afterwards, the surface defects of the brazed joint are inspected by using a surface defect inspection method; Then, the internal defects of the brazed joint are inspected by an internal defect inspection method; Finally, the air tightness of the brazed joint is checked by a vacuum air tightness test method, thereby completing the entire quality evaluation process of the brazed joint.

2. The method for evaluating the quality of a multi-layer material vacuum brazing joint according to claim 1, characterized in that: The specific method of inspecting the quality of the surface of the brazed joint using the naked eye or a low-power magnifying glass is: Pick up the brazed joint and observe the surface of the brazed joint with the naked eye or a low-power magnifying glass, wherein the magnification of the low-power magnifying glass is 5-10 times; Observe whether the exposed end of the brazing seam of the brazed joint forms a rounded corner, whether the rounded corner is uniform, and whether there are cracks, pores and other external defects; During the observation process, the brazed joint is continuously rotated to achieve an all-round inspection of the surface quality of the brazed joint.

3. The method for evaluating the quality of a multi-layer material vacuum brazing joint according to claim 1, characterized in that: The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is: Sprinkle the fluorescent powder evenly on the surface of the solder joint, and place the solder joint on the quality inspection table in a dark room environment; By utilizing the characteristic of the fluorescent powder emitting fluorescence under ultraviolet irradiation, the defects on the surface of the solder joint are exposed, thereby realizing the inspection of the surface defects of the solder joint.

4. The method for evaluating the quality of a multi-layer material vacuum brazing joint according to claim 1, wherein: The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is: Clean the stains on the weld surface of the brazed joint, and then apply a layer of red colorant on the weld surface of the brazed joint; The red stripes oozing out of the red colorant are used to display the position and shape of the defects on the surface of the solder joint, thereby realizing the inspection of the surface defects of the solder joint.

5. The method for evaluating the quality of multi-layer material vacuum brazing joints according to claim 1, characterized in that: The specific method of using the surface defect inspection method to inspect the surface defects of the brazed joint is: Clean the stains on the surface of the brazed joint, and then evenly sprinkle magnetic powder on the surface of the brazed joint; The magnetic field is used to generate magnetic marks on the surface of the ferromagnetic material to display the surface defects of the brazed joint, thereby realizing the inspection of the surface defects of the brazed joint.

6. The method for evaluating the quality of a multi-layer material vacuum brazing joint according to claim 1, characterized in that: The specific method of using the internal defect inspection method to inspect the internal defects of the brazed joint is: Move the X-ray inspection machine, Y-ray inspection machine or ultrasonic inspection machine to the quality inspection table and position it above the brazed joint; Starting the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine, and allowing the X-ray inspection machine, the Y-ray inspection machine or the ultrasonic inspection machine to emit X-rays, Y-rays or ultrasonic waves to the brazed joint; The internal defects of the brazed joint are inspected by using the X-ray, the Y-ray or the ultrasonic wave to inspect the pores, slag inclusions, incomplete penetration and cracks in the brazed joint and the base material of the brazed joint.

7. The method for evaluating the quality of a multi-layer material vacuum brazing joint according to claim 1, characterized in that: The specific method of using the vacuum airtightness test method to check the airtightness of the brazed joint is: using a water pressure test method, an airtightness test method, a gas permeation test method, a kerosene permeation test method or a mass spectrometry test method to check the airtightness of the brazed joint.

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