Vacuum brazing connection method for double-layer structure combustion chamber casing

Abstract

The invention relates to the field of vacuum brazing, in particular to vacuum brazing connection of a high-temperature alloy combustion chamber casing with an inner and outer double-layer structure, and relates to a vacuum brazing connection method of a combustion chamber casing with a double-layer structure. The method is realized based on a welding tool, the welding tool is used for positioning, assembling and fixing an outer casing mounting surface through a seam allowance on a bottom plate, the coaxiality requirement of an inner casing and the outer casing is ensured by positioning a mandrel, the upper part of the mandrel is fixed through a pressing plate, and the height dimension requirement of the whole combustion chamber casing is ensured; the method is characterized in that the blade welding deformation is controlled and the brazing seam quality is improved through reasonable vacuum brazing process parameters, a welding sequence, thermocouple detection, welding tool control coaxiality and other process elements.

Description

Technical Field

[0001] The present invention relates to the field of vacuum brazing, and particularly to a vacuum brazing connection of a high-temperature alloy combustion chamber casing with an inner and outer double-layer structure, and a vacuum brazing connection method for a double-layer structure combustion chamber casing. Background Art

[0002] A certain model combustion chamber casing assembly is composed of an inner casing and an outer casing with a double-layer structure. After being connected by two rows of blades (72 blades in each row), it is welded by a vacuum brazing method. When the inner and outer casings are vacuum brazed integrally at one time, there is a temperature difference, resulting in large welding internal stresses. The following two problems occur: First, due to the temperature difference during the welding of the inner and outer casings, the brazing temperature is inconsistent, the welding temperature field is uneven, resulting in large internal stresses, and the assembly gap is too small, causing serious deformation of the blades and resulting in unqualified welding. Second, due to inappropriate welding sequence, welding temperature, and filler metal application method, the filler metal at the root of the weld of the leaf-shaped hole flows and accumulates, and the weld quality is unqualified. Summary of the Invention

[0003] Object of the Invention

[0004] The present invention provides a vacuum brazing connection method for a combustion chamber casing with an inner and outer double-layer structure and a double row of blades. By means of step-by-step welding of the inner and outer casings, optimizing the vacuum brazing process parameters, increasing thermocouple temperature monitoring, improving the welding fixture, etc., the problems such as poor brazing weld quality and serious blade deformation caused by uneven temperature field and unreasonable process are solved.

[0005] Technical Solution

[0006] In order to achieve the above object, a vacuum brazing connection method for a double-layer structure combustion chamber casing is provided. It is realized based on a welding fixture. The welding fixture is assembled by positioning with a rabbet on the bottom plate to fix the installation surface of the outer casing, and a mandrel is used for positioning to ensure the coaxiality requirement of the inner and outer casings. The upper part of the mandrel is fixed by a pressing plate to ensure the height dimension requirement of the entire combustion chamber casing; the key is to control the welding deformation of the blades and improve the brazing weld quality through process elements such as reasonable vacuum brazing process parameters, welding sequence, thermocouple detection, and welding fixture control of coaxiality.

[0007] A vacuum brazing connection method for a double-layer structure combustion chamber casing, characterized by comprising the following steps:

[0008] S1: The fitter uses 1000# - 1200# sandpaper to clean the welding parts of the inner casing, outer casing, and blades, and remove all oil stains, oxide films, and impurities near all the blades and leaf-shaped holes. Ensure that the filler metal has good wettability during the vacuum brazing process;

[0009] S2: Ultrasonically clean the inner casing, outer casing, and blades described in S1 in a clean alcohol medium. The leaf-shaped holes to be welded should be completely immersed in the alcohol liquid. After cleaning, wipe the parts clean with a clean white cloth. Prevent secondary contamination after cleaning;

[0010] S3: Assemble the inner casing, outer casing, and double-row blades. It is allowed to select matching blades or grind the leaf-shaped holes to ensure the clearance requirements between the blades and the leaf-shaped holes. The assembly is carried out using a welding fixture, and ensure the coaxiality error requirements for the assembly of the inner casing and the outer casing;

[0011] S4: In the step described in S3, evenly apply brazing filler metal at the leaf-shaped holes where the inner casing is connected to the blades. The brazing filler metal should surround the upper half of each leaf-shaped hole, specifically 2 / 3 to 4 / 5 of the perimeter of the leaf-shaped hole. Apply flux on the non-welding surfaces and the welding fixture;

[0012] S5: Send the combustion chamber casing described in S4 into a vacuum brazing furnace, and evenly place 2 to 3 thermocouples at the leaf-shaped holes of the inner casing to be welded to monitor the welding temperature accuracy and uniformity of the inner casing weld seam;

[0013] S6: Carry out vacuum brazing welding of the inner casing blades in the state of S5;

[0014] S7: After the vacuum brazing is completed, take out the parts. There shall be no cracks, penetrative defects, or weld beads on the brazed seams;

[0015] S8: In the state described in S7, remove the combustion chamber casing parts from the welding fixture, and evenly apply brazing filler metal at the leaf-shaped holes where the outer casing is connected to the blades. The application method is the same as described in step S4: The brazing filler metal should surround the upper half of each leaf-shaped hole, specifically 2 / 3 to 4 / 5 of the perimeter of the leaf-shaped hole. Apply flux on the non-welding surfaces and the welding fixture. After application, assemble the combustion chamber into the welding fixture again;

[0016] S9: Send the combustion chamber parts described in S8 into a vacuum brazing furnace, and evenly place 2 to 3 thermocouples on the outside of the outer casing to monitor the welding temperature accuracy and uniformity of the outer casing weld seam;

[0017] S10: Carry out vacuum brazing welding of the outer casing blades in the state described in S9; The vacuum brazing welding temperature of the outer casing should be lower than the vacuum brazing temperature in S6 on the premise of ensuring good welding quality;

[0018] S11: After the vacuum brazing is completed, take out the combustion chamber parts. There shall be no cracks, penetrative defects, or weld beads on the brazed seams;

[0019] Further, S12: Perform a kerosene test on the combustor parts taken out in S11. Apply a suspension of chalk powder on one side of the weld. After the chalk powder is completely dry, drop kerosene on the other side of the weld to check the tightness of the vacuum brazing weld, and observe for 5 minutes;

[0020] S13: Perform stress relief on the combustor casing after vacuum brazing.

[0021] In a possible embodiment, in the step S2, the cleaning time for ultrasonic cleaning is 10 min to 30 min, the ultrasonic frequency is 30 Hz to 60 Hz, and after ultrasonic cleaning, it should be put into the furnace for vacuum brazing within 24 hours;

[0022] In a possible embodiment, in the step S3, the clearance between the blade and the blade-shaped hole after assembly is between 0.02 mm and 0.08 mm;

[0023] In a possible embodiment, in the step S3, the coaxiality error after the inner and outer casings are assembled should not be greater than φ0.2 mm;

[0024] In a possible embodiment, in the step S4, the filler metal grade is BNi82CrSiB, in paste or powder form with 150 mesh to 200 mesh; the flux is a mixture of Al 2 O 3 powder with 300 mesh to 400 mesh and pure water;

[0025] In a possible embodiment, apply the filler metal at 72 blade-shaped holes where the inner casing is connected to the blade shape;

[0026] In a possible embodiment, in the step S8, the filler metal grade is BNi82CrSiB, in paste or powder form with 150 mesh to 200 mesh; the flux is a mixture of Al 2 O 3 powder with 300 mesh to 400 mesh and pure water;

[0027] In a possible embodiment, in the steps S6 and S10, the vacuum brazing process parameters are: evacuate the brazing furnace to 1×10 -3 Pa and heat. Heat at a heating rate of 15 °C / min to 920 °C to 950 °C, then hold for 10 min to 30 min; then heat at a heating rate of 10 °C / min to 1020 °C to 1100 °C for vacuum brazing, and the welding time is 3 min to 10 min; after welding, cool with the furnace to 400 °C ± 10 °C, and then cool to room temperature by filling with argon;

[0028] In a possible embodiment, in the step S13, the stress relief process is a vacuum furnace, heated to 400°C to 600°C and held for 2h to 4h;

[0029] In a possible embodiment, the welding tooling material for the combustion chamber casing is GH4169, which is the same as the material of the combustion chamber casing;

[0030] In a possible embodiment, the welding tooling for the combustion chamber casing is a mandrel type design, positioned by the outer casing stop, and the mandrel passes through the inner casing to ensure the coaxiality requirement and control the welding deformation at the same time.

[0031] In a possible embodiment, in the S7 step, if cracks or penetrative defects appear in the brazing seam, the assembly process needs to be improved to ensure that the blades are welded in a free and unconstrained state. If weld beads appear, the process parameters should be optimized. The beneficial effects of this application are as follows:

[0032] The technical key of the present invention is (1) step-by-step welding of the inner and outer casings: after the overall assembly of the combustion chamber casing is completed, the inner casing and the outer casing are subjected to step-by-step vacuum brazing. When the inner and outer casings are vacuum brazed simultaneously, due to the double-layer structure, the welding temperature field is uneven, and the inner and outer casings cannot reach the reasonable vacuum brazing temperature at the same time, resulting in problems such as blade deformation and unqualified brazing seam quality; (2) placing thermocouples locally to accurately monitor the temperature: when the inner and outer casings are welded step by step, due to the difference and lag between the welding temperature displayed by the brazing furnace and the actual temperature at the weld of the combustion chamber casing, it is necessary to place thermocouples near the welds of the inner and outer casings to monitor the actual welding temperature and temperature uniformity at the welds, ensuring the accuracy of the brazing temperature and the quality of the brazing seam; (3) the method of applying paste brazing filler metal to 2 / 3 to 4 / 5 of the circumference of the upper half of the blade-shaped hole: during the vacuum brazing process of the combustion chamber casing, the brazing filler metal melts and fills the blade-shaped hole by capillary action to form a brazing seam. When the brazing filler metal melts into a liquid, due to the action of gravity, it flows. If the paste brazing filler metal is applied to the entire circumference of each blade-shaped hole, it is easy to have problems of local flow and accumulation under the blade-shaped hole, forming weld beads and resulting in unqualified appearance quality. Therefore, the brazing filler metal only needs to be applied to 2 / 3 to 4 / 5 of the circumference of the upper half of the blade-shaped hole. When the temperature at the weld of the blade-shaped hole reaches the vacuum brazing temperature, a small amount of the brazing filler metal flows to the lower part of the blade-shaped hole and combines with the capillary action to form a complete, continuous and smooth brazing seam, thus avoiding the problems of brazing filler metal accumulation and weld beads affecting the appearance quality of the weld seam. Description of the Drawings

[0033] Figure 1 is a schematic diagram of the vacuum brazing of the combustion chamber casing;

[0034] Figure 2 is a schematic diagram of the structure of the vacuum brazing welding fixture for the combustion chamber casing;

[0035] Figure 3It is a schematic diagram of the application method of the paste solder at the leaf-shaped holes. Specific embodiments

[0036] The present invention will be further described below in conjunction with embodiments. The following only describes some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0037] In order to further illustrate the content of the present invention in detail, the content of the present invention will be further described below in conjunction with the drawings.

[0038] S1: The fitter uses 1000# - 1200# sandpaper to clean the parts to be welded of the inner casing, outer casing and blades, and remove all oil stains, oxide films and impurities near all blades and leaf-shaped holes. Ensure that the solder has good wettability during the vacuum brazing process;

[0039] S2: Ultrasonically clean the inner casing, outer casing and blades described in S1 in a clean alcohol medium, and the leaf-shaped holes to be welded should be completely immersed in the alcohol liquid. The ultrasonic cleaning time is 20 min and the frequency is 40 Hz. After cleaning, the parts are wiped clean with a clean white cloth. The cleaned parts should be picked up with clean special gloves to prevent secondary contamination; the parts should be put into the furnace for vacuum brazing within 8 h after ultrasonic cleaning;

[0040] S3: Assemble the inner casing, outer casing and 72 blades, allowing the selection of blades or grinding of the leaf-shaped holes to ensure that the gap between the blades and the leaf-shaped holes is within the range of 0.06 mm - 0.08 mm. The assembly needs to be carried out using a special welding fixture, and the coaxiality of the assembly of the inner casing and the outer casing should be ensured within φ0.08 mm by the fixture. Only in this way can the coaxiality of the inner and outer casings be controlled within φ0.2 mm after welding;

[0041] S4: In the step described in S3, only apply the solder evenly at the leaf-shaped holes where the inner casing is connected to the blades. The solder should surround the upper half of each leaf-shaped hole, about 2 / 3 - 4 / 5 of the circumference of the leaf-shaped hole. Apply Al 2 O 3 solder resist on the non-welding surface and the welding fixture;

[0042] S5: Send the combustion chamber casing described in S4 into the vacuum brazing furnace, and evenly place 2 - 3 thermocouples at the leaf-shaped holes to be welded on the inner casing to monitor the welding temperature accuracy and uniformity of the inner casing weld;

[0043] S6: Carry out vacuum brazing welding in the state described in S5; the process parameters are: the brazing furnace is evacuated to 1×10 -3Heat with Pa. Heat to 930°C at a heating rate of 15°C / min, hold for 10 min, then heat to 1080°C ± 10°C at a heating rate of 10°C / min for vacuum brazing, with a welding time of 4 min. After welding, cool in the furnace to 400°C ± 10°C, and then cool to room temperature by filling with argon.

[0044] S7: After the vacuum brazing is completed, take out the parts wearing clean white gloves. There shall be no cracks, penetrating defects, or welding beads on the brazing seam, etc.

[0045] S8: In the state described in S7, remove the combustion chamber casing parts from the welding fixture, and evenly apply brazing filler metal at the blade-shaped holes where the outer casing is connected to the blades. The application method is the same as described in step S4: The brazing filler metal should surround the upper half of each blade-shaped hole, approximately 2 / 3 to 4 / 5 of the perimeter of the blade-shaped hole. Apply Al 2 O 3 flux on the non-welding surface and the welding fixture. After application, assemble the combustion chamber into the welding fixture again.

[0046] S9: Send the combustion chamber parts described in S8 into the vacuum brazing furnace, and evenly place 2 - 3 thermocouples on the outside of the outer casing to monitor the welding temperature accuracy and uniformity of the outer casing weld seam.

[0047] S10: Perform vacuum brazing welding in the state described in S9; the vacuum brazing process parameters are: evacuate the brazing furnace to 1×10 -3 Pa and heat. Heat to 930°C at a heating rate of 15°C / min, hold for 12 min, then heat to 1040°C ± 10°C at a heating rate of 10°C / min for vacuum brazing, with a welding time of 4 min. After welding, cool in the furnace to 400°C ± 10°C, and then cool to room temperature by filling with argon.

[0048] The vacuum brazing temperature of the outer casing is 1040°C ± 10°C, which should be lower than the vacuum brazing temperature of the inner casing, 1080°C ± 10°C, in step S6. This is because the vacuum brazing temperature range of BNi2 brazing filler metal is within 1020°C to 1100°C, and welding operations can be carried out within this range. However, when brazing the outer casing, in order to reduce the welding internal stress and control the blade deformation to the maximum extent, the welding temperature is reduced on the premise of ensuring good formation of the outer casing brazing weld seam.

[0049] S11: After the vacuum brazing is completed, take out the combustion chamber parts wearing clean white gloves. There shall be no cracks, penetrating defects, or welding beads on the brazing seam, etc.

[0050] S12: Conduct a kerosene test in the state described in S11. Apply a suspension of chalk powder on one side of the weld seam. After the chalk powder is completely dry, drop kerosene on the other side of the weld seam to check the tightness of the vacuum brazed weld seam. Observe for 5 minutes. If there is no leakage of kerosene within 5 minutes, it proves that the weld seam tightness is qualified.

[0051] S13: Perform stress relief treatment on the combustor casing after vacuum brazing. The stress relief process is to use a vacuum furnace, heat it to 510°C ± 5°C and hold for 4 hours.

[0052] Those skilled in the art of this technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here. The specific embodiments described above have further elaborated on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A vacuum brazing connection method for a double-layer structure combustion chamber casing, characterized in that, it is realized based on a welding fixture. The welding fixture is positioned and assembled through a rabbet on the bottom plate to fix the installation surface of the outer casing. A mandrel is used for positioning to ensure the coaxiality requirement between the inner casing and the outer casing. The upper part of the mandrel is fixed by a pressing plate to ensure the height dimension requirement of the entire combustion chamber casing. It controls the welding deformation of the blades and improves the quality of the brazing seam through process elements such as vacuum brazing process parameters, welding sequence, thermocouple detection, and coaxiality control of the welding fixture, including the following steps: Step S1: The fitter uses sandpaper to clean the areas to be welded on the inner casing, outer casing, and blades, removing all oil stains, oxide films, and impurities near all blades and blade-shaped holes; ensuring that the filler metal has good wettability during the vacuum brazing process. Step S2: Ultrasonically clean the inner casing, outer casing, and blades described in Step S1 in a clean alcohol medium, and the blade-shaped holes to be welded should be completely immersed in the alcohol liquid; after cleaning, wipe the parts clean with a clean white cloth; prevent secondary contamination after cleaning. Step S3: Assemble the inner casing, outer casing, and double-row blades, allowing for the selection of blades or grinding of the blade-shaped holes to ensure the clearance requirement between the blades and the blade-shaped holes; the assembly is carried out using a welding fixture, and the coaxiality error requirement for the assembly of the inner casing and the outer casing is ensured. Step S4: In the step described in Step S3, evenly apply the filler metal at the blade-shaped holes where the inner casing is connected to the blades. The filler metal should surround the upper half of each blade-shaped hole, specifically 2 / 3 to 4 / 5 of the circumference of the blade-shaped hole; apply a flux inhibitor on the non-welding surfaces and the welding fixture. Step S5: Send the combustion chamber casing described in Step S4 into a vacuum brazing furnace, and evenly place 2 to 3 thermocouples at the blade-shaped holes of the inner casing to be welded to monitor the welding temperature accuracy and uniformity of the inner casing weld seam. Step S6: Carry out vacuum brazing welding of the inner casing blades in the state of Step S5. Step S7: After the vacuum brazing is completed, take out the parts. There shall be no cracks, penetrative defects, or weld beads on the brazing seam. Step S8: In the state described in Step S7, remove the combustion chamber casing parts from the welding fixture, and evenly apply the filler metal at the blade-shaped holes where the outer casing is connected to the blades; the application method is the same as in Step S4: the filler metal should surround the upper half of each blade-shaped hole, specifically 2 / 3 to 4 / 5 of the circumference of the blade-shaped hole; apply a flux inhibitor on the non-welding surfaces and the welding fixture; after application, reassemble the combustion chamber into the welding fixture. Step S9: Send the combustion chamber parts described in Step S8 into a vacuum brazing furnace, and evenly place 2 to 3 thermocouples on the outside of the outer casing to monitor the welding temperature accuracy and uniformity of the outer casing weld seam. Step S10: Carry out vacuum brazing welding of the outer casing blades in the state of Step S9; the vacuum brazing welding temperature of the outer casing should be lower than the vacuum brazing temperature in Step S6 on the premise of ensuring good welding quality. Step S11: After the vacuum brazing is completed, take out the combustion chamber parts. There shall be no cracks, penetrative defects, or weld beads on the brazing seam.

2. The method according to claim 1, characterized in that, It also includes step S12: subjecting the combustion chamber parts taken out in step S11 to a kerosene test; applying a chalk powder suspension on one side of the weld seam, and after the chalk powder is completely dry, dropping kerosene on the other side of the weld seam to check the tightness of the vacuum brazing weld seam, with an observation time of 5 minutes.

3. The method according to claim 2, characterized in that it also includes step S13: performing stress relief treatment on the combustion chamber casing after vacuum brazing is completed.

4. The method according to claim 3, characterized in that in the said step S2, the cleaning time for ultrasonic cleaning is 10 minutes to 30 minutes, the ultrasonic frequency is 30 Hz to 60 Hz, and the parts should be put into the furnace for vacuum brazing within 24 hours after the ultrasonic cleaning is completed.

5. The method according to claim 4, characterized in that in the said step S3, the clearance between the blade and the blade hole after assembly should be between 0.02 mm and 0.08 mm.

6. The method according to claim 5, characterized in that in the said step S3, the coaxiality error after the inner and outer casings are assembled should not be greater than φ0.2 mm.

7. The method according to claim 6, characterized in that In the step S4, the filler metal grade is BNi82CrSiB, in paste or powder form with a mesh size of 150 to 200; the solder resist is a mixture of Al 2 O 3 powder with a mesh size of 300 to 400 and pure water; the filler metal is applied at 72 blade-shaped holes where the inner casing is connected to the blade shape.

8. The method according to claim 7, characterized in that In the step S8, the filler metal grade is BNi82CrSiB, in paste or powder form with a mesh size of 150 to 200; the solder resist is a mixture of Al 2 O 3 powder with a mesh size of 300 to 400 and pure water; in the steps S6 and S10, the vacuum brazing process parameters are as follows: the brazing furnace is evacuated to 1×10 -3 Pa for heating; heated at a heating rate of 15°C / min to 920°C - 950°C, then held for 10 min - 30 min; then heated at a heating rate of 10°C / min to 1020°C - 1100°C for vacuum brazing, and the welding time is 3 min - 10 min; after welding, it is cooled in the furnace to 400°C ± 10°C, and then cooled to room temperature by filling with argon gas.

9. The method according to claim 8, characterized in that in the said step S13, the stress relief process is a vacuum furnace, heating to 400 °C to 600 °C and holding for 2 hours to 4 hours; the welding fixture material for the combustion chamber casing is GH4169, which is the same as the material of the combustion chamber casing; the welding fixture for the combustion chamber casing is of a mandrel type design, positioning with the outer casing stop, and the mandrel passes through the inner casing to ensure the coaxiality requirements and at the same time control the welding deformation.

10. The method according to claim 9, characterized in that in step S7, if cracks or penetrating defects appear on the brazing seam, the assembly process needs to be improved to ensure that the blades are welded in a free and unconstrained state; if there are weld beads, the process parameters should be optimized.

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