A brazing process for stainless steel tube shell and Kovar alloy in medical CT tube

Abstract

The invention relates to the technical field of vacuum brazing, and in particular to a brazing process for a stainless steel tube shell and a Kovar alloy in a medical CT tube, comprising the following steps: S1, surface treatment of the Kovar alloy: nickel plating on the surface of the Kovar alloy; S2, assembling the stainless steel tube shell and the Kovar alloy; S3, vacuum brazing. The method of the invention comprehensively considers factors such as the surface treatment of the Kovar alloy, the selection of brazing material, the control of the assembly gap and the vacuum environment to ensure the quality and reliability of the welded joint, and solves the problem of poor welding between the stainless steel tube shell and the Kovar alloy in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum brazing, and in particular to a brazing process for a stainless steel tube shell and a Kovar alloy in a medical CT tube. Background Art

[0002] Medical CT tubes are the core components of CT equipment, responsible for generating X-rays. They are high-value consumables with high technical barriers, and their performance directly affects the quality of CT imaging and the service life of the equipment. Medical CT tubes have high technical content and are difficult to manufacture, and usually need to work in a high vacuum, high temperature, and high speed environment.

[0003] The stainless steel tube shell assembly is a key component that supports the cathode and cathode as well as the X-ray outlet. Its function is to maintain the ultra-high vacuum environment and keep it clean to maintain high vacuum and high pressure. It involves multi-level welding of stainless steel, copper alloy, beryllium sheet, nickel ring and Kovar alloy, which requires a high position relationship.

[0004] The linear expansion coefficients of stainless steel and Kovar alloy are quite different, which brings great technical challenges to brazing the two. The brazing process of stainless steel tube shell and Kovar alloy needs to comprehensively consider factors such as surface treatment, brazing material selection, assembly gap control and vacuum environment to ensure the quality and reliability of the welded joint. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a brazing process for a stainless steel tube shell and a Kovar alloy in a medical CT tube.

[0006] A brazing process for a stainless steel tube shell and a Kovar alloy in a medical CT tube comprises the following steps:

[0007] S1. Kovar alloy surface treatment:

[0008] Plating nickel on the surface of the Kovar alloy, wherein the thickness of the nickel layer is 5-10 μm, to obtain the surface-treated Kovar alloy;

[0009] S2, stainless steel shell and Kovar alloy assembly:

[0010] Assemble the stainless steel tube shell and the surface-treated Kovar alloy obtained in step S1, with a single-side gap of 0.35-0.45 mm, and ensure that the flatness of the welding plane of the stainless steel tube shell and the surface-treated Kovar alloy is ≤0.1 mm;

[0011] S3. Assembly solder:

[0012] Placing a ring-shaped solder between the stainless steel tube shell and the welding plane of the surface-treated Kovar alloy, wherein the material of the ring-shaped solder is AgCu28 and the thickness of the ring-shaped solder is 0.14-0.16 mm;

[0013] S4. Vacuum brazing:

[0014] The assembled stainless steel tube shell and the surface treated Kovar alloy are placed in a vacuum brazing device for vacuum brazing at a vacuum degree of ≤0.0005 Pa, a temperature of 820-840° C., and a heat preservation time of 2-4 minutes to obtain a welded part.

[0015] Furthermore, in step S1, the nickel plating method is: immersing the Kovar alloy in an electroplating solution for electroplating, and the current density of the electroplating is 2-3A / dm 2 , time is 60~90min, and the temperature of the plating solution is 15~30℃.

[0016] Description: The nickel layer plated on the surface of Kovar alloy can play a protective role, which can prevent problems such as oxidation and carbon deposition on the surface of Kovar alloy, thereby improving the quality of the joint; nickel plating can effectively improve the corrosion resistance of Kovar alloy, making it less prone to corrosion and oxidation, thereby extending the service life of Kovar alloy.

[0017] Furthermore, the solute of the electroplating solution includes: 180-200 g / L nickel sulfate, 30-40 g / L boric acid, 8-20 g / L sodium chloride, and the solvent is water.

[0018] Note: The above three components work together to give the plating solution good covering and dispersing capabilities, and can obtain a uniform and complete nickel plating layer, thereby improving the overall protection and performance of Kovar alloy.

[0019] Furthermore, in step S1, before nickel plating the surface of the Kovar alloy, the Kovar alloy is first pickled with a hydrochloric acid solution with a mass concentration of 10-15% for 10-20 minutes.

[0020] Note: Hydrochloric acid pickling can remove the oxide scale and adhering salts on the workpiece surface, making it easier for subsequent electroplating.

[0021] Furthermore, before step S3, the ring-shaped solder is subjected to a heat uniform treatment, and the heat uniform treatment method is:

[0022] Taking the center of the ring-shaped solder as the center of the circle, a circular dividing line is drawn on the ring-shaped solder to divide the ring-shaped solder into an inner ring area and an outer ring area, wherein the inner ring area accounts for 60-70% of the area of ​​the ring-shaped solder, and then both the front and back sides of the outer ring area are blackened;

[0023] A femtosecond laser beam is then used to form microporous structures on both sides of the annular sheet solder. The power of the femtosecond laser beam is 100-400w, the scanning interval is 50-120μm, the processing rate is 0.7-0.9mm / s, the central wavelength is 750-950nm, the pulse width is 80-100fs, the repetition frequency is 1-800KHz, and the scanning time of each microporous array is 70-250ms. Then, a silver-based solder is sprayed into the microporous structure on one side of the corresponding stainless steel tube shell, and a palladium-based solder is sprayed into the microporous structure on one side of the corresponding Kovar alloy. The spraying amounts of the silver-based solder and the palladium-based solder are the same and the microporous structure on the annular sheet solder is completely filled, and the flatness of the annular sheet solder is ensured to be ≤0.1mm.

[0024] Description: The ring-shaped flake solder is divided into an inner ring area and an outer ring area and treated differently, which enhances the stability of the connection from a structural perspective and reduces the risk of loosening and cracking of the welding parts during use; spraying different solders on the corresponding surfaces of the stainless steel tube shell and the Kovar alloy can better match the welding requirements of the two materials and improve the quality and reliability of the welded joints; using a femtosecond laser beam to form a microporous structure on both sides of the ring-shaped flake solder, the specific surface area of ​​the ring-shaped flake solder is increased, and the wettability of the ring-shaped flake solder to the stainless steel tube shell and the Kovar alloy is effectively improved, so that the ring-shaped flake solder can be better spread and filled during the brazing process, reducing defects such as pores and cold welds, thereby improving the density and strength of the welding; the outer ring area after blackening treatment can absorb more heat, which is helpful for the uniform distribution of heat during the brazing process, reducing the generation of thermal stress, reducing the risk of welding defects caused by differences in thermal expansion coefficients, improving welding quality and joint reliability, and enabling the welding parts to maintain stable performance under different temperature environments.

[0025] Furthermore, the blackening treatment method is: rotating the outer ring area of ​​the ring-shaped solder into a blackening liquid, the rotation speed is 150-200 r / min, the temperature of the blackening liquid is 35-40°C, and the time is 10-15 min.

[0026] Note: The outer ring area after blackening treatment can absorb more heat, which helps to evenly distribute heat during brazing, reduce the generation of thermal stress, reduce the risk of welding defects caused by differences in thermal expansion coefficients, improve welding quality and joint reliability, and enable the welding part to maintain stable performance under different temperature environments.

[0027] Furthermore, the blackening liquid comprises: 40~60L: 1g: 0.7g of palladium nitrate solution, polyamide polyamine, and dimethyl terephthalate, and the mass concentration of the palladium nitrate solution is 8~10%.

[0028] Description: The palladium nitrate solution in the blackening solution will form an oxide film or compound layer with a certain protective effect on the surface of the annular flake solder, thereby improving the corrosion resistance of the outer ring area of ​​the annular flake solder; polyamide polyamine and dimethyl terephthalate will improve the chemical activity of the surface of the annular flake solder, making the chemical reaction between the annular flake solder and the stainless steel tube shell and Kovar alloy more complete, further improving the bonding strength and stability of the welded joint.

[0029] Furthermore, the silver-based solder is Ag45CuZn or Ag72Cu.

[0030] Description: Silver-based solder has excellent electrical conductivity, thermal conductivity and wettability, and can spread well on the surface of Kovar alloy, stainless steel and AgCu28 to form a strong weld. Its strength and corrosion resistance can also meet general welding requirements, and its cost is relatively lower than that of gold-based and palladium-based solders, so it is widely used.

[0031] Furthermore, the palladium-based solder is Pd75Cu25.

[0032] Description: Palladium-based solder has good high temperature performance, corrosion resistance and oxidation resistance, and can form reliable connections between Kovar alloy, stainless steel and AgCu28. It has good wettability to a variety of metal materials, can effectively fill the welding gap, and improve the strength and sealing of the welded joint.

[0033] Compared with the existing welding method of stainless steel and Kovar alloy, the beneficial effects of the present invention are:

[0034] (1) The method of the present invention ensures that the assembly gap and flatness of the stainless steel tube shell and the Kovar alloy are qualified, and ensures the high cleanliness of the stainless steel tube shell, the Kovar alloy and the solder; comprehensively considers factors such as the surface treatment of the Kovar alloy, the selection of solder, the assembly gap control and the vacuum environment to ensure the quality and reliability of the welded joint, thereby solving the problem of poor welding between the stainless steel tube shell and the Kovar alloy in the prior art.

[0035] (2) The present invention divides the annular flake solder into an inner ring area and an outer ring area and performs different treatments on them, thereby enhancing the stability of the connection from a structural perspective and reducing the risk of loosening and cracking of the welding parts during use; spraying different solders on the corresponding surfaces of the stainless steel tube shell and the Kovar alloy can better match the welding requirements of the two materials and improve the quality and reliability of the welded joints; a femtosecond laser beam is used to form a microporous structure on both sides of the annular flake solder, thereby increasing the specific surface area of ​​the annular flake solder, and effectively improving the wettability of the annular flake solder to the stainless steel tube shell and the Kovar alloy, so that the annular flake solder can be better spread and filled during the brazing process, reducing defects such as pores and cold welds, thereby improving the density and strength of the welding; the outer ring area after blackening treatment can absorb more heat, which helps to evenly distribute heat during the brazing process, reduce the generation of thermal stress, reduce the risk of welding defects caused by differences in thermal expansion coefficients, improve the welding quality and reliability of the joint, and enable the welding parts to maintain stable performance under different temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a comparison chart of the results of the brazing process study 1 of the present invention;

[0037] Figure 2 This is a comparison chart of the results of the brazing process exploration 2 of the present invention;

[0038] Figure 3 It is a comparison chart of the results of brazing process exploration 3 of the present invention. DETAILED DESCRIPTION

[0039] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0040] Embodiment 1: A brazing process of a stainless steel tube shell and a Kovar alloy in a medical CT tube comprises the following steps:

[0041] S1. Kovar alloy surface treatment:

[0042] First, the 4J29 Kovar alloy was pickled with a hydrochloric acid solution with a mass concentration of 12% for 15 minutes, and then the surface of the Kovar alloy was nickel plated. The nickel plating method was as follows: the Kovar alloy was immersed in the plating solution for electroplating, and the electroplating current density was 2.5A / dm 2 , the time is 75min, the temperature of the electroplating solution is 22℃, the solutes of the electroplating solution include: 190g / L nickel sulfate, 35g / L boric acid, 14g / L sodium chloride, the solvent is water, the thickness of the nickel layer of the nickel plating is 8μm, and the surface treated Kovar alloy is obtained;

[0043] S2, stainless steel shell and Kovar alloy assembly:

[0044] Assemble the stainless steel tube shell and the surface-treated Kovar alloy obtained in step S1, with a single-side gap of 0.4 mm, ensuring that the flatness of the welding plane of the stainless steel tube shell and the surface-treated Kovar alloy is 0.05 mm;

[0045] S3. Assembly solder:

[0046] A ring-shaped solder is placed between the stainless steel tube shell and the welding plane of the surface-treated Kovar alloy. The material of the ring-shaped solder is AgCu28 and the thickness of the ring-shaped solder is 0.15 mm.

[0047] S4. Vacuum brazing:

[0048] The assembled stainless steel tube shell and the surface-treated Kovar alloy were placed in a vacuum brazing device for vacuum brazing at a vacuum degree of 0.0003 Pa, a temperature of 830° C., and a holding time of 3 min to obtain a welded part.

[0049] Example 2: The difference between this example and Example 1 is that, in step S1, before nickel plating the surface of the Kovar alloy, the Kovar alloy is first pickled with a hydrochloric acid solution with a mass concentration of 10% for 10 minutes.

[0050] Example 3: The difference between this example and Example 1 is that, in step S1, before nickel plating the surface of the Kovar alloy, the Kovar alloy is first pickled with a hydrochloric acid solution with a mass concentration of 15% for 20 minutes.

[0051] Example 4: This example is different from Example 1 in that, in step S1, the Kovar alloy is immersed in the electroplating solution for electroplating, and the electroplating current density is 2A / dm 2 , time is 60min, the temperature of the electroplating solution is 15℃, and the thickness of the nickel layer is 5μm.

[0052] Example 5: This example is different from Example 1 in that, in step S1, the Kovar alloy is immersed in the electroplating solution for electroplating, and the electroplating current density is 3A / dm 2 , time is 90min, the temperature of the electroplating solution is 30℃, and the thickness of the nickel layer is 10μm.

[0053] Example 6: This example is different from Example 1 in that, in step S1, the solute of the electroplating solution includes: 180 g / L nickel sulfate, 40 g / L boric acid, 20 g / L sodium chloride, and the solvent is water.

[0054] Example 7: This example is different from Example 1 in that, in step S1, the solute of the electroplating solution includes: 200 g / L nickel sulfate, 30 g / L boric acid, 8 g / L sodium chloride, and the solvent is water.

[0055] Example 8: This example is different from Example 1 in that, in step S2, the stainless steel tube shell is assembled with the surface-treated Kovar alloy obtained in step S1, the single-side gap of the assembly is 0.35 mm, and the thickness of the ring-shaped solder is 0.14 mm.

[0056] Example 9: This example is different from Example 1 in that, in step S2, the stainless steel tube shell is assembled with the surface-treated Kovar alloy obtained in step S1, the single-side gap of the assembly is 0.45 mm, and the thickness of the ring-shaped solder is 0.16 mm.

[0057] Example 10: This example is different from Example 1 in that, in step S4, the vacuum brazing temperature is 820°C and the holding time is 2 minutes.

[0058] Example 11: This example is different from Example 1 in that, in step S4, the vacuum brazing temperature is 840°C and the holding time is 4 minutes.

[0059] Embodiment 12: This embodiment is different from Embodiment 1 in that, before step S3, the ring-shaped solder is subjected to heat uniform treatment, and the method of heat uniform treatment is:

[0060] Taking the center of the ring-shaped solder as the center of the circle, a circular dividing line is drawn on the ring-shaped solder to divide the ring-shaped solder into an inner ring area and an outer ring area, wherein the inner ring area accounts for 65% of the area of ​​the ring-shaped solder, and then both the front and back sides of the outer ring area are blackened;

[0061] The blackening treatment method is: the outer ring area of ​​the ring-shaped solder is rotated and immersed in the blackening liquid, the speed is 175r / min, the temperature of the blackening liquid is 38°C, the time is 12min, and the composition of the blackening liquid is: 50L: 1g: 0.7g of palladium nitrate solution, polyamide polyamine, dimethyl terephthalate, and the mass concentration of palladium nitrate solution is 9%;

[0062] A femtosecond laser beam is then used to form a microporous structure on both sides of the annular flake solder. The power of the femtosecond laser beam is 250w, the scanning interval is 85μm, the processing rate is 0.8mm / s, the central wavelength is 800nm, the pulse width is 90fs, the repetition frequency is 400KHz, and the scanning time of each microporous array is 160ms. Then, a silver-based solder is sprayed into the microporous structure on one side of the corresponding stainless steel tube shell. The silver-based solder is Ag45CuZn, and a palladium-based solder is sprayed into the microporous structure on the corresponding side of the Kovar alloy. The palladium-based solder is Pd75Cu25. The spraying amounts of the silver-based solder and the palladium-based solder are the same and the microporous structure on the annular flake solder is completely filled, and the flatness of the annular flake solder is ensured to be 0.05mm.

[0063] Embodiment 13: This embodiment differs from Embodiment 12 in that the inner ring region accounts for 60% of the area of ​​the ring-shaped solder.

[0064] Embodiment 14: This embodiment differs from Embodiment 12 in that the inner ring region accounts for 70% of the area of ​​the ring-shaped solder.

[0065] Example 15: This example differs from Example 12 in that the outer ring area of ​​the ring-shaped solder is rotated and immersed in the blackening liquid at a rotation speed of 150 r / min, the temperature of the blackening liquid is 35° C., and the time is 10 min.

[0066] Example 16: This example differs from Example 12 in that the outer ring area of ​​the ring-shaped solder is rotated and immersed in the blackening liquid at a rotation speed of 200 r / min, the temperature of the blackening liquid is 40° C., and the time is 15 min.

[0067] Example 17: This example is different from Example 12 in that the ingredients of the blackening liquid are: 40L: 1g: 0.7g of palladium nitrate solution, polyamide polyamine, and dimethyl terephthalate, and the mass concentration of the palladium nitrate solution is 8%.

[0068] Example 18: This example is different from Example 12 in that the composition of the blackening liquid is: 60L: 1g: 0.7g of palladium nitrate solution, polyamide polyamine, and dimethyl terephthalate, and the mass concentration of the palladium nitrate solution is 10%.

[0069] Example 19: The difference between this example and Example 12 is that a femtosecond laser beam is used to form a micropore structure on both sides of the ring-shaped solder. The power of the femtosecond laser beam is 100w, the scanning interval is 50μm, the processing rate is 0.7mm / s, the central wavelength is 750nm, the pulse width is 80fs, the repetition frequency is 1KHz, and the scanning time of each micropore array is 70ms.

[0070] Example 20: The difference between this example and Example 12 is that a femtosecond laser beam is used to form a microporous structure on both sides of the ring-shaped sheet solder, the power of the femtosecond laser beam is 400w, the scanning interval is 120μm, the processing rate is 0.9mm / s, the central wavelength is 950nm, the pulse width is 100fs, the repetition frequency is 800KHz, and the scanning time of each microporous array is 250ms.

[0071] Experimental Example: The description of this experimental example is based on the recorded schemes in Example 1 to Example 20, and is intended to illustrate the practical application effect of the present invention.

[0072] The leakage rate of the welded parts obtained in each embodiment was tested, and the average value of the three test results of each embodiment was taken as the final airtightness experimental result.

[0073] 1. To explore the effect of surface treatment of Kovar alloy on the air tightness of welded parts.

[0074] Depend on Figure 1 From the comparison of the results, it can be seen that pickling parameters that are too small or too large, electroplating parameters that are too small or too large, and the proportion of nickel sulfate in the electroplating solution that is too small or too large will increase the leakage rate of the welded parts and reduce the air tightness of the welded parts. Therefore, in comprehensive comparison, the parameter effect of Example 1 is relatively better.

[0075] 2. Explore the influence of brazing parameters on the air tightness of welded parts.

[0076] Depend on Figure 2 From the comparison of the results, it can be seen that if the assembly parameters are too small or too large, or the vacuum brazing parameters are too small, the leakage rate of the welded parts will increase and the air tightness of the welded parts will decrease. The temperature of Example 11 is higher and the time is longer, and the leakage rate is lower than that of Example 1, but the decrease is smaller than the increase in the parameters. Therefore, from an economic point of view, the parameter effect of Example 1 is relatively better.

[0077] 3. Explore the effect of uniform heat treatment of solder on the air tightness of welded parts.

[0078] The difference between the comparative example 1 and the example 12 is that the areas of the inner ring region and the outer ring region are the same;

[0079] The difference between Control Example 2 and Example 12 is that the outer ring area is not subjected to blackening treatment;

[0080] Depend on Figure 3 The comparison of the results shows that the leakage rates of Examples 12 to 20 and Comparative Examples 1 to 2 all show a significant downward trend compared with Example 1, that is, the uniform heat treatment of the ring-shaped sheet solder has a beneficial effect on improving the airtightness of the welded parts; however, the area of ​​the inner ring region in Comparative Example 1 is too small, and the blackening treatment is not performed in Comparative Example 2, so the degree of heat absorption of the outer ring region is reduced, and the degree of thermal uniformity is reduced, so the reduction in the leakage rate is reduced compared with Examples 12 to 20;

[0081] By comparing Examples 12 to 20, it can be seen that if the area of ​​the inner ring is too small or too large, the blackening treatment parameters are too small, the proportion of dimethyl terephthalate in the blackening liquid is too small or too large, the femtosecond laser beam parameters are too small or too large, and the flatness of the ring-shaped solder is too large, the leakage rate of the welded parts will be reduced. The blackening treatment temperature of Example 16 is higher and the time is longer, and the leakage rate is reduced compared with Example 12, but the reduction is smaller than the increase in the parameters. Therefore, from an economic perspective, the parameter effect of Example 12 is relatively better.

Claims

1. A brazing process for the stainless steel tube shell and Kovar alloy in a medical CT tube, characterized in that: The following steps are involved: S1. Kovar alloy surface treatment: Plating nickel on the surface of the Kovar alloy, wherein the thickness of the nickel layer is 5-10 μm, to obtain the surface-treated Kovar alloy; S2, stainless steel shell and Kovar alloy assembly: Assemble the stainless steel tube shell and the surface-treated Kovar alloy obtained in step S1, with a single-side gap of 0.35-0.45 mm, and ensure that the flatness of the welding plane of the stainless steel tube shell and the surface-treated Kovar alloy is ≤0.1 mm; S3. Assembly solder: Placing a ring-shaped solder between the stainless steel tube shell and the welding plane of the surface-treated Kovar alloy, wherein the material of the ring-shaped solder is AgCu28 and the thickness of the ring-shaped solder is 0.14-0.16 mm; Before placement, the ring-shaped solder is subjected to a heat uniform treatment, wherein the heat uniform treatment is performed by: Taking the center of the ring-shaped solder as the center of the circle, a circular dividing line is drawn on the ring-shaped solder to divide the ring-shaped solder into an inner ring area and an outer ring area, wherein the inner ring area accounts for 60-70% of the area of ​​the ring-shaped solder, and then both the front and back sides of the outer ring area are blackened; The blackening treatment method is: rotating the outer ring area of ​​the ring-shaped solder into a blackening liquid, the rotation speed is 150-200 r / min, the temperature of the blackening liquid is 35-40° C., the time is 10-15 min, and the composition of the blackening liquid is: 40-60 L: 1 g: 0.7 g of palladium nitrate solution, polyamide polyamine, dimethyl terephthalate, and the mass concentration of the palladium nitrate solution is 8-10%; A femtosecond laser beam is then used to form microporous structures on both sides of the annular sheet solder. The power of the femtosecond laser beam is 100-400w, the scanning interval is 50-120μm, the processing rate is 0.7-0.9mm / s, the central wavelength is 750-950nm, the pulse width is 80-100fs, the repetition frequency is 1-800KHz, and the scanning time of each microporous array is 70-250ms. Then, a silver-based solder is sprayed into the microporous structure on one side of the corresponding stainless steel tube shell, and a palladium-based solder is sprayed into the microporous structure on one side of the corresponding Kovar alloy. The spraying amount of the silver-based solder and the palladium-based solder is the same and the microporous structure on the annular sheet solder is completely filled, and the flatness of the annular sheet solder is ensured to be ≤0.1mm. The silver-based solder is Ag45CuZn or Ag72Cu, and the palladium-based solder is Pd75Cu25. S4, vacuum brazing: The assembled stainless steel tube shell and the surface treated Kovar alloy are placed in a vacuum brazing device for vacuum brazing at a vacuum degree of ≤0.0005 Pa, a temperature of 820-840° C., and a heat preservation time of 2-4 minutes to obtain a welded part.

2. The brazing process of the stainless steel tube shell and the Kovar alloy in the medical CT tube according to claim 1, characterized in that: In step S1, the nickel plating method is: immersing the kovar alloy in an electroplating solution for electroplating, and the current density of the electroplating is 2-3A / dm 2 , time is 60~90min, and the temperature of the plating solution is 15~30℃.

3. The brazing process of the stainless steel tube shell and the Kovar alloy in the medical CT tube as claimed in claim 2, characterized in that: The solute of the electroplating solution includes: 180-200 g / L nickel sulfate, 30-40 g / L boric acid, 8-20 g / L sodium chloride, and the solvent is water.

4. The brazing process of the stainless steel tube shell and the Kovar alloy in the medical CT tube according to claim 1, characterized in that: In step S1, before nickel plating the surface of the Kovar alloy, the Kovar alloy is first pickled with a hydrochloric acid solution with a mass concentration of 10-15% for 10-20 minutes.

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