A brazing anti-adhesion method

Abstract

The present invention provides a method for preventing adhesion in brazing, which includes performing a water-repellent treatment on the fixture used in brazing and forming a water-repellent film on the surface of the fixture. Specifically, the water-repellent treatment of the fixture is divided into two steps. Step 1: First, the fixture is successively subjected to sandblasting, degreasing, water washing, and drying treatments. Step 2: Then, the fixture is successively subjected to preheating, spraying of a water-repellent agent, air drying, and film curing treatments. At the same time, the present invention gives specific treatment methods for vacuum brazing and non-vacuum brazing. By performing a water-repellent film treatment on the fixture, the present invention is used to prevent adhesion in high-temperature brazing. The water-repellent film layer can be used multiple times, and the anti-adhesion effect is good and the quality is stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding, and particularly relates to a method for preventing the adhesion of brazing filler metal to tooling fixtures or preventing the flow of brazing filler metal to parts or special positions where it should not reach during high-temperature brazing by using a water-repellent treatment film layer. Background Art

[0002] During high-temperature brazing (brazing temperature above 1300°C), in order to prevent the molten brazing filler metal from flowing between fixtures (such as pallets) and adhering to them, resulting in the adhesion of parts to the tooling, making it difficult to separate and simultaneously causing defects.

[0003] Currently, in order to prevent the adhesion problem, it is usually in the form of a flux inhibitor. For example, alumina powder, zirconia powder, yttria powder, titanium dioxide powder, etc. are used as anti-adhesion (flux inhibitor); when using, water is mixed with the powder and stirred, and it is coated on the tooling or the part to prevent adhesion in a viscous state. On the one hand, the dried anti-adhesion powder is easy to scatter in the brazing furnace. On the other hand, the anti-adhesion powder is prone to uneven coating and falling off. If the anti-adhesion powder is unevenly coated or the anti-adhesion powder falls off, it will lead to the failure to achieve the flux-blocking effect, resulting in the adhesion of parts to the tooling and the flow of brazing filler metal to non-brazing important areas, and seriously, the parts will be scrapped; in addition, the flux inhibitor needs to be cleaned frequently, and the anti-adhesion powder can only be used once, and it needs to be re-coated when brazing again. There are few anti-adhesion treatment methods for high-temperature brazing in the prior art, and the difficulty is great. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention aims to propose a brazing anti-adhesion method, which can overcome the problems of adhesion between parts and fixtures caused by the flow of brazing filler metal during high-temperature brazing of parts and the problem of the flow of brazing filler metal to non-brazing important areas, and is simple to operate. Further, after using the anti-adhesion method of the present invention, the brazing fixture can be reused and will not cause powder pollution to the brazing furnace.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A brazing anti-adhesion method includes:

[0007] Performing water-repellent treatment on the fixtures used for brazing and forming a water-repellent film on the surface of the fixtures.

[0008] As an option, the thickness of the water-repellent film is 2 - 3 μm.

[0009] As an option, the performing water-repellent treatment on the fixtures used for brazing includes:

[0010] Step 1, successively performing sandblasting, degreasing, water washing and drying treatments on the fixtures;

[0011] Step 2: The fixture is successively preheated, sprayed with a water repellent, air-dried, and cured to form a film.

[0012] As an option, the water repellent has the property of not failing at temperatures above 1300°C, that is, the high-temperature water repellent can withstand temperatures above 1300°C, and the water repellent is applicable to metal raw materials.

[0013] As an option, in the said Step 1,

[0014] Sandblasting: The sand used is white fused alumina with a particle size of 100 - 120 mesh. The sandblasting pressure is 0.2 - 0.3 Mpa. The angle between the sandblasting nozzle and the sandblasting surface of the fixture is 45° - 90°. The distance between the sandblasting nozzle and the sandblasting surface is maintained at 200 - 250 mm. After sandblasting, the surface sand grains are cleaned with a soft brush.

[0015] Degreasing: The surface of the fixture is wiped with a flannelette dipped in decontamination powder and cleaning agent to remove oil, ensuring that the surface can be completely covered by a water film.

[0016] Water washing: It includes rinsing with warm water at 40 - 60°C and then rinsing with running tap water.

[0017] Drying: It is dried with compressed air or air-dried.

[0018] As an option, in the said Step 2,

[0019] Preheating: The fixture is preheated in an oven at a temperature of 150 ± 20°C for more than 1 minute.

[0020] Spraying: After the fixture is taken out of the oven, it is immediately sprayed with a water repellent loaded in a spray gun. The distance between the nozzle and the surface of the fixture is maintained at 100 - 150 mm. The same position is sprayed up and down 3 - 5 times.

[0021] Air-drying: The sprayed fixture is air-dried for more than 30 minutes.

[0022] Curing to form a film: The sprayed and air-dried fixture is placed for more than 5 days until the water repellent coating is completely cured to form a film.

[0023] As an option, the water repellent is applied by spraying, dipping, or brushing. Generally, considering the saving of the amount of water repellent used, spraying is usually used.

[0024] As an option, the brazing anti-adhesion method further includes,

[0025] Before brazing, clean the oil stains and dirt on the parts to be brazed, the fixture rack, and the fixture with a water repellent film on the surface, and complete the assembly of the three within 48 hours.

[0026] As an option, when the parts to be brazed are non-pickled and non-nickel-plated, they are put into the furnace for brazing within 24 hours after assembly. During brazing, the parts to be brazed should be in a stress-free state as much as possible.

[0027] As an option, the brazing anti-adhesion method further includes,

[0028] After assembly, add sticky tape solder near the brazing gap of the parts to be brazed. The amount of solder used should be no less than 2 times the maximum volume of the joint gap.

[0029] As an option, the brazing anti-adhesion method further includes,

[0030] When vacuum brazing is used, place the parts to be brazed that have been assembled and filled with solder and the fixture with a hydrophobic film formed on its surface in a vacuum brazing furnace. Before heating the vacuum brazing furnace, pre-pump the vacuum. Start heating and raising the temperature after the pressure is lower than the preset pressure. Keep the temperature when it is higher than the preset pressure. Control the maximum temperature and the holding time at the maximum temperature of the vacuum brazing. After brazing, the brazed parts and the fixture are cooled with the furnace under argon protection, and finally air-cooled after leaving the furnace.

[0031] As an option, the brazing anti-adhesion method further includes,

[0032] When non-vacuum brazing is used, first heat the brazing furnace to a temperature higher than the maximum brazing temperature, then place the parts to be brazed that have been assembled and filled with solder and the fixture with a hydrophobic film formed on its surface in an argon envelope. Then perform brazing under argon protection. After brazing, the brazed parts and the fixture are cooled with the furnace under argon protection, and finally air-cooled after leaving the furnace. It should be noted that the argon envelope generally refers to a type of fixture with a cavity. Argon is introduced into the cavity through a metal tube, and there is an inlet pipe and an exhaust pipe. The argon envelope is an image name.

[0033] When the present invention is in use, it only needs to cover the working area of the fixture. Of course, it is also possible to completely cover the surface of the fixture, but the amount of the hydrophobic agent used will increase.

[0034] As an option, the hydrophobic film can be formed by directly spraying (or other methods) the hydrophobic agent on the surface of the non-brazing important area of the parts to be brazed, or the protection of the surface of the non-brazing important area of the parts to be brazed can be formed through the structural design of the fixture. It should be noted that a hydrophobic film needs to be formed on the surface of the fixture in the corresponding area, and its protection effect is the same as directly spraying the hydrophobic agent on the surface of the non-brazing important area of the parts.

[0035] Compared with the prior art, the present invention has the following characteristics:

[0036] The present invention realizes anti - adhesion during high - temperature brazing (of course, the method of the present invention is also applicable to anti - adhesion during low - temperature brazing) by performing a water - repellent film treatment on a fixture (such as a pallet). The water - repellent film layer can be used multiple times, with good anti - sticking effect and stable quality. The water - repellent treatment film layer has a good anti - sticking effect and stable quality. The film layer can withstand multiple brazing operations and still have an anti - sticking function. The method of removing and re - preparing the water - repellent treatment film layer is simple. Since a water - repellent film is formed on the fixture, the filler metal cannot adhere, forming a protection and avoiding the filler metal flowing into non - critical brazing areas. In the present invention, the thickness of the water - repellent treatment film layer is controllable, usually 2 - 3 μm, suitable for use in brazing fixtures with precise dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the state of the brazing fixture after the water - repellent treatment in the present invention. At this time, it can be seen that the water - repellent effect of the film layer is good;

[0038] Figure 2 is the state of the fixture after 2 times of brazing at 1230 °C in the present invention. No adhesion occurs between the filler metal and the fixture after the water - repellent treatment, and the water - repellent film layer remains intact. DETAILED DESCRIPTION OF THE INVENTION

[0039] The following further describes the present invention in conjunction with the drawings and specific embodiments. However, it should not be understood that the scope of the subject matter of the present invention is limited to the following embodiments. Without departing from the above - mentioned technical idea of the present invention, all modifications, substitutions, and changes made according to ordinary technical knowledge and common means in the art are included in the scope of the present invention.

[0040] Regarding the adhesion problem of parts during high - temperature brazing, the present invention adopts the following treatment method:

[0041] ① Perform pre - treatment for cleaning the fixture (such as sandblasting, degreasing, drying, etc.).

[0042] ② Perform water - repellent treatment on the fixture.

[0043] ③ Put the fixture with good water - repellent treatment into the brazing furnace for anti - adhesion during the brazing process.

[0044] ④ When the anti - sticking effect of the water - repellent film layer decreases due to scratching or other reasons, it can be removed by sandblasting and then re - treated with water - repellent.

[0045] Taking the fixture made of FGH4097 material as an example, the specific implementation method of the anti - adhesion method during high - temperature brazing is as follows:

[0046] 1. Pre - treatment for cleaning the fixture;

[0047] 1.1 Sandblasting;

[0048] The sand used is white corundum with a particle size of (100 - 120) mesh. The sandblasting pressure is (0.2 - 0.3) Mpa. The angle between the sandblasting nozzle and the sandblasted surface of the part should be between 45° and 90°. The distance between the sandblasting nozzle and the sandblasted surface is maintained at (200 - 250) mm. After sandblasting, use a soft brush to clean the sand grains on the surface.

[0049] 1.2 Degreasing;

[0050] Dip a flannelette in decontamination powder, cleaning agent, etc. and wipe the surface of the fixture to remove oil, ensuring that the surface can be completely covered by a water film.

[0051] 1.3 Hot water wash;

[0052] Rinse with warm water at (40 - 60) °C.

[0053] 1.4 Cold running water wash;

[0054] Rinse with flowing tap water.

[0055] 1.5 Drying;

[0056] Blow dry with compressed air or air dry.

[0057] 2. Hydrophobic treatment;

[0058] Use LD4380 hydrophobic agent to conduct hydrophobic treatment on the surface of the fixture.

[0059] 2.1 Preheating;

[0060] Use an oven to preheat the fixture at a temperature of 150 ± 20 °C for more than 1 minute.

[0061] 2.2 Spraying;

[0062] After loading the LD4380 hydrophobic agent into the spray gun, immediately spray the fixture taken out of the oven. The distance between the nozzle and the surface of the fixture is maintained at (100 - 150) mm, and spray up and down repeatedly at the same position for (3 - 5) times.

[0063] 2.3 Air drying;

[0064] Air dry the sprayed fixture for more than 30 minutes.

[0065] 2.4 Curing into a film;

[0066] Place the air-dried fixture after spraying for more than 5 days until the hydrophobic coating is completely cured into a film. The cured hydrophobic film layer has a hydrophobic effect as Figure 1 shown.

[0067] 3. Brazing;

[0068] 3.1 Preparation before brazing

[0069] Before brazing, clean the oil stains and dirt on the parts, brazing fixtures and racks. Aviation washing gasoline, solvent oil, acetone, alcohol or cleaning agents can be used for cleaning. After the parts are cleaned, they are not allowed to be touched with bare hands, and should be assembled within 48 hours (here refers to the assembly of the parts to be brazed, the fixtures forming the hydrophobic film and the racks). Parts that are not assembled within 48 hours should be cleaned again.

[0070] 3.2 Assembly and positioning;

[0071] After the non-pickled and non-nickel-plated parts are assembled and positioned, they should be put into the furnace for brazing within 240 hours (the 240 hours here means that the established operation steps can be completed within 10 days, because some parts are very complex and the time for filling the brazing material is very long). When assembling the parts, the operator should wear clean cotton gloves to prevent contamination of the parts. When assembling the parts, the brazing parts of the parts should be in a stress-free state as much as possible. The parts to be brazed are supported and positioned by fixtures.

[0072] 3.3 Brazing material addition;

[0073] Add the necessary amount of sticky tape brazing material B-Ni55NbCoWCrAlSiMoTi(C)-S near the brazing gap of the parts according to the parts specified in the drawing. The amount of brazing material should be no less than 2 times the maximum volume of the joint gap.

[0074] 3.4 Brazing;

[0075] 3.4.1 Vacuum brazing;

[0076] Place the parts with brazing material added and the fixtures (treated with hydrophobic treatment) in the vacuum brazing furnace. The vacuum should be pumped before the brazing furnace is heated. Start heating and raising the temperature after the vacuum pressure is lower than 4×10 -2 Pa. During the brazing heating process, the vacuum pressure should not be greater than 4×10 -2 Pa. When the vacuum pressure is greater than 4×10 -2 Pa, heat preservation can be carried out. Continue to raise the temperature after the vacuum pressure is lower than 4×10 -2 Pa. The maximum temperature during the brazing process is (1230±10)°C, and the holding time at the maximum temperature is (20 - 30) minutes.

[0077] 3.4.2 Non-vacuum brazing (high-temperature assessment of argon protection welding in a high-temperature pit furnace);

[0078] Heat the high-temperature pit furnace, and the maximum temperature in the furnace is (1350±10)°C; place the parts with brazing material added and the fixtures (treated with hydrophobic treatment) in the argon bag, and place the argon bag in the high-temperature pit furnace for brazing under argon protection. The maximum temperature during the brazing process is (1230±10)°C, and the holding time is (20 - 30) minutes.

[0079] 3.5 Cooling and taking out of the furnace;

[0080] After the brazing heat preservation is completed, the parts and fixtures are cooled in the furnace with argon protection until the temperature is ≤80°C, and then taken out of the furnace for air cooling.

[0081] 3.6 Inspection;

[0082] Inspect the brazing quality at the visible welds, and check the adhesion between the fixture coated with the hydrophobic film layer and the brazing filler metal. The hydrophobic film layer should have the anti-sticking effect as Figure 2 shown.

[0083] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. Although the illustrative specific embodiments of the present invention are described above for the understanding of those skilled in the art of the present technology, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A brazing anti-adhesion method, characterized in that: including, performing a water-repellent treatment on the fixture used for brazing and forming a water-repellent film on the surface of the fixture; the performing of the water-repellent treatment on the fixture used for brazing includes Step 1, sequentially performing sandblasting, degreasing, water washing, and drying on the fixture; Step 2, sequentially performing preheating, spraying a water-repellent agent, air drying, and curing into a film on the fixture; in the said Step 2, preheating, preheating the fixture in an oven at a temperature of 150 ± 20°C for more than 1 minute; spraying, immediately spraying the fixture taken out of the oven with a water-repellent agent loaded in a spray gun, keeping the distance between the nozzle and the surface of the fixture at 100 - 150 mm, and repeating spraying up and down at the same position 3 - 5 times; air drying, air drying the sprayed fixture for more than 30 minutes; curing into a film, placing the fixture that has been air dried after spraying for more than 5 days until the water-repellent coating is completely cured into a film.

2. The brazing anti-adhesion method according to claim 1, characterized in that: The thickness of the water-repellent film is 2 - 3 μm.

3. The brazing anti-adhesion method according to claim 1, characterized in that: In the said Step 1, for sandblasting, white corundum with a particle size of 100 - 120 mesh is used as the sand, the sandblasting pressure is 0.2 - 0.3 Mpa, the angle between the sandblasting nozzle and the sandblasting surface of the fixture is 45° - 90°, the distance between the sandblasting nozzle and the sandblasting surface is kept at 200 - 250 mm, and after sandblasting, the surface sand grains are cleaned with a soft brush; degreasing, wiping and degreasing the surface of the fixture with a flannelette dipped in cleansing powder and a cleaning agent to ensure that the surface can be completely covered by a water film; water washing, including rinsing with warm water at 40 - 60°C and then rinsing with running tap water; drying, drying with compressed air or air drying.

4. A brazing anti-sticking method according to claim 1, characterized in that: It also includes, before brazing, cleaning the oil stains and dirt on the parts to be brazed, the fixture rack, and the fixture with a water-repellent film formed on its surface, and completing the assembly of the three within 48 hours.

5. A brazing anti-adhesion method according to claim 4, characterized in that: When the parts to be brazed are non-pickled and non-nickel-plated parts, they are put into the furnace for brazing within 24 hours after the assembly is completed, and during brazing, the parts to be brazed should be kept in a stress-free state as much as possible.

6. A brazing anti-adhesion method according to claim 4, characterized in that: It also includes, after the assembly is completed, adding sticky tape solder near the brazing gap of the parts to be brazed, and the amount of solder used is not less than 2 times the maximum volume of the joint gap.

7. A brazing anti-adhesion method according to claim 4, characterized in that: It also includes, when using vacuum brazing, placing the parts to be brazed that have completed the assembly and added solder and the fixture with a water-repellent film formed on its surface into a vacuum brazing furnace. Before heating the vacuum brazing furnace, pre-pump the vacuum. Start heating and raising the temperature after the pressure is lower than the preset pressure, keep the temperature when it is higher than the preset pressure, control the maximum temperature and the holding time at the maximum temperature of the vacuum brazing. After brazing is completed, the brazed parts and the fixture are cooled with the furnace under argon protection, and finally taken out of the furnace and air-cooled.

8. A brazing anti-adhesion method according to claim 4, characterized in that: It also includes, when using non-vacuum brazing, first heat the brazing furnace to a temperature higher than the maximum brazing temperature, then place the parts to be brazed that have completed the assembly and added solder and the fixture with a water-repellent film formed on its surface into an argon package, and then perform brazing under argon protection. After brazing is completed, the brazed parts and the fixture are cooled with the furnace under argon protection, and finally taken out of the furnace and air-cooled.

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