A process for brazing titanium alloy injectors

Abstract

The present invention discloses a process method for brazing titanium alloy injectors, which includes the design of a brazing fastener, the configuration of basic parameters of the brazing material, and the brazing process. The fastener includes a counterweight and a fixing seat, and the injector is located between the counterweight and the fixing seat. The basic parameters of the vacuum brazing furnace are required to be as follows: the maximum heating temperature is above 1100°C, the common working temperature is 960°C, and the time for the empty furnace to heat up to 1100°C is ≤ 2h; the furnace temperature uniformity meets ±5°C; the temperature control accuracy meets ±2; the vacuum furnace temperature uniformity zone should cover the location of the brazing part, and the vacuum degree during the brazing process is required to be better than 4×10 ‑2 Pa, titanium alloy brazing process requires vacuum better than 4 × 10 ‑2 Pa, and the cold-state pressure rise rate should be less than 0.67 Pa / h. The process steps include: brazing material configuration and placement, workpiece assembly and testing, workpiece fixation, vacuuming, secondary heating, brazing, post-weld strengthening, and cooling. The brazed titanium alloy injector meets design specifications and can adapt to the complex operating environment of engine products.

Description

Technical Field

[0001] The invention relates to the technical field of thrust chamber injector welding technology, and in particular to a process method for brazing titanium alloy injectors. Background Art

[0002] The thrust chamber is the component that converts the chemical energy of the liquid propellant into jet kinetic energy and generates thrust. It primarily consists of injectors and a body. The injectors atomize, mix, and burn the propellant entering the combustion chamber at a specific flow rate and mixture ratio, producing combustion gases. A key component of a liquid rocket engine, the injectors are the devices that achieve energy conversion and thrust generation. The injectors are direct-flow injectors with a complex structure, consisting of multiple and shaped internal channels. During operation, the fuel and oxidizer mix and spontaneously ignite, and the resulting combustion gases act on the thrust chamber to generate thrust. Depending on the thrust output, the injectors have 4 to 20 welds. The injector faceplates feature hundreds of small holes of varying sizes and angles, and the thin walls create high welding requirements.

[0003] Common welding methods for injectors include argon arc welding and brazing, but the welding processes vary significantly due to structural differences. Traditional fusion welding cannot meet production requirements due to space limitations and injector deformation. Therefore, brazing, which offers minimal structural limitations and uniform heat input, is used. After brazing, the injector surface must be free of oxidation and blackening, and the brazing filler metal must not clog the small holes. Summary of the Invention

[0004] The present invention provides a process method for brazing titanium alloy injectors. The brazed titanium alloy injectors meet design index requirements and can adapt to the complex working environment of engine products.

[0005] The technical solution adopted by the present invention is a process for brazing a titanium alloy injector, comprising the following steps:

[0006] a) Place the parts in the furnace and fix them with the brazing fasteners using an injector, ensuring the levelness is within 0.1mm;

[0007] b) Vacuuming: pre-vacuum degree is not less than 5×10 -3 Pa, the vacuum degree during heating, brazing and strengthening process shall not be less than 4×10 -2 Pa;

[0008] c) Heating: (300-500)°C, heating time (50-100) min, heating rate (3-8)°C / min, holding time (10-30) min;

[0009] d) Heating: (600-800)°C, heating time (60-120) min, heating rate (3-8)°C / min, holding time (10-30) min;

[0010] e) Brazing: Raise the furnace temperature to (920-980)°C, heating time (20-40) min, heating rate (3-8)°C / min, hold for (8-25) min;

[0011] f) Post-weld strengthening: furnace temperature drops to (800-900)°C ± 10°C, and keeps warm for (1-4) hours;

[0012] g) The cooling time should be no less than 4 hours. Vacuuming should be continued during cooling. After cooling to below 40°C, stop vacuuming and take out the parts.

[0013] Preferably, a fastener for brazing titanium alloy injectors is used to fix the injector, the fastener includes a counterweight and a fixing seat, the injector is located between the counterweight and the fixing seat, the counterweight has a transparent small hole, which is used for degassing of the brazing material and the adhesive during brazing, the counterweight is in contact with the small hole surface of the injector where there is no small hole, the injector includes an upper cover, a middle layer and a lower bottom connected by brazing, and adopts a plug-in structure brazing seam form, the width of the annular groove for arranging the brazing material is generally (1-2) mm, the height in the groove to be brazed is generally (1.4-1.9) mm, and the annular groove is narrow.

[0014] Preferably, the basic parameters of the vacuum brazing furnace are as follows: the maximum heating temperature is above 1100℃, the common working temperature is 960℃, the time for the empty furnace to heat up to 1100℃ is ≤2h; the furnace temperature uniformity meets ±5℃; the temperature control accuracy meets ±2; the vacuum furnace temperature uniformity area should cover the position of the brazing parts, and the vacuum degree during the brazing process is required to be better than 4×10 -2 Pa, titanium alloy brazing process requires vacuum better than 4 × 10 -2 Pa, the cold pressure rise rate should be less than 0.67Pa / h.

[0015] Preferably, the injector material is TC4 or TC10, the solder grade is Type 1510 (MBF-5002), the melting temperature is (820-860)°C, the solder is in powder form, and the particle size is 50-100 mesh.

[0016] Preferably, the brazing gap is set to (0.05-0.1) mm.

[0017] Preferably, the solder is in paste form, and the weight ratio of the paste solder to the binder is (1:3.5) to (1:4.5).

[0018] The present invention has the following beneficial effects: the injector fastener effectively facilitates the smooth progress of the brazing process, and the assembly of parts during high-temperature brazing processes. The brazed seam after brazing has high strength, high temperature resistance, and corrosion resistance, and can adapt to complex operating environments of the product. The process method can effectively complete the welding of injectors, and the welding process is reliable, repeatable, and highly applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the brazing fastener of the present invention.

[0020] Figure 2 This is a structural diagram of the counterweight of the present invention.

[0021] Figure 3 for Figure 2 AA direction view.

[0022] Figure 4 It is a schematic structural diagram of the fixing seat of the present invention.

[0023] Figure 5 for Figure 4 AA direction view.

[0024] Figure 6 It is the front view of the injector structure of the present invention.

[0025] Figure 7 It is a side view of the injector structure of the present invention.

[0026] Figure 8 for Figure 7 A partial enlarged view of the enlarged position 1.

[0027] Figure 9 for Figure 7 A partial enlarged view of the enlarged position 2.

[0028] Markings in the figure: 1-fixed seat, 2-counterweight, 3-injector, 4-ring groove, 31-upper cover, 32-middle layer, 33-lower bottom. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0030] A process for brazing titanium alloy injectors requires the following basic parameters for a vacuum brazing furnace: a maximum heating temperature of 1100°C or higher, a common operating temperature of 960°C, and a time of ≤2 hours for an empty furnace to reach 1100°C; a furnace temperature uniformity of ±5°C; a temperature control accuracy of ±2°C; a vacuum furnace temperature uniformity zone covering the location of the brazing parts; and a vacuum degree of better than 4×10 -2 Pa, titanium alloy brazing process requires vacuum better than 4 × 10 -2 Pa, the cold pressure rise rate should be less than 0.67Pa / h.

[0031] A brazing fastener structure used in a process for brazing a titanium alloy injector is shown in FIG. Figures 1 to 5 As shown, the main structure of the brazing fastener is composed of a counterweight 2 and a fixing seat 1. The counterweight 2 has transparent pores for volatile gas release of the brazing material and the adhesive during brazing. The counterweight 2 is in contact with the small hole surface of the injector 3 without a small hole, and cannot block the small hole of the injector 3. The counterweight 2 is processed with an annular groove 4 at the position of the small hole of the injector 3 and the annular groove 4 is connected to the small hole of the injector 3. The annular groove 4 is of different sizes and is determined according to the distribution of the small holes on the panel of the injector 3. Figures 6 to 9 , schematic diagrams of magnified positions 1 and 2. Magnified position 2 is an enlarged view of a non-step brazed seam. The brazing filler metal is arranged in the groove for assembly. After assembly, it is placed in a brazing furnace for brazing. The brazing seam is formed by the brazing filler metal pre-extruded into the fitting gap and capillary action.

[0032] The setting of the annular groove 4 facilitates the volatilization of the brazing filler metal and the adhesive to avoid clogging of the small holes and accumulation of other substances. At the same time, this type of structure increases the force-bearing area of the injector 3 panel, preventing deformation of the small holes caused by deformation of the small hole panel of the injector 3, which leads to changes in the flow resistance index. The brazing tooling needs to have a certain weight, generally (1 to 5) kg, and a symmetrical structure, so that the injector 3 is evenly stressed during brazing and can fall smoothly without tilting when the brazing filler metal melts. The uniform weight distribution of the injector 3 parts can enable the various components of the injector 3 to reach the optimal assembly state under the dynamic activities of high-temperature brazing, so that the injector 3 can be completed in a safe and reliable environment. The brazing fastener material generally uses materials with low outgassing, such as stainless steel. The brazing fastener has low cost, low processing difficulty, and is easy to operate.

[0033] A process for brazing titanium alloy injectors. The materials used for the injector 3 are generally TC4 or TC10. TC4 / TC10 refers to (α+β) titanium alloys. The brazing filler metal is Type 1510 (MBF-5002) with a melting temperature of (820-860)°C. The filler metal is in powder form with a particle size of 50-100 mesh. The injector 3 structure includes an upper cover 31, a middle layer 32, and a lower base 33. The structure is shown in the figure below. Figure 6 and Figure 7As shown, 91 in the figure represents vacuum brazing, 511 represents electron beam welding, and the parallelism in the figure is 0.3mm. The three parts are connected by brazing. The enlarged view of the brazing part is shown in the figure. Figure 8 and Figure 9 As shown, the brazing joint adopts a plug-in structure. The width of the annular groove 4 for placing the brazing material is generally (1-2) mm, and the height of the groove to be brazed is generally (1.4-1.9) mm. The annular groove 4 is relatively narrow. Due to the narrow annular groove 4, the brazing material is placed manually using a paste method. The paste is placed in the groove of the component. Excess brazing material is then cleaned with a tool. The height of the brazing material in the groove where the paste is placed is checked. Porosity and areas without paste after cleaning need to be filled. After the brazing material is placed, the component is inverted and assembled. After assembly, a pressure of (0.2-0.5) MPa is applied to evenly distribute the brazing material and penetrate the path of the molten brazing material during brazing. After assembly, the injector cavity is X-rayed to confirm that there is no brazing material accumulation or blockage in the bottom channel of the cavity. The component with brazing material is not allowed to be inverted or tilted during assembly. Ensure the assembly parallelism of the parts and the brazing area of the groove ribs. At the same time, the brazing material will fill part of the brazing gap through the extrusion force, which is helpful for the formation of the brazing seam during brazing.

[0034] A brazing gap used in a titanium alloy injector brazing process: An appropriate brazing gap ensures even distribution of the brazing filler metal throughout the joint, achieving optimal brazing results. A gap of 0.05-0.1 mm provides optimal results, but due to the complex structure of the part, maintaining this gap requirement is difficult. Extensive experience has proven that a gap of 0.05-0.15 mm provides a good balance between the two. The amount of brazing filler metal used depends on the product structure and is calculated by calculating the reserved brazing gap (which varies with different materials and structures). Due to the structural characteristics of this product, the prefabricated brazing filler metal must be added to fill the pre-set position, increasing its height within the groove to improve capillary action and the brazing pass rate. Upon completion of the brazing, the pre-set position will not be completely free of filler metal; therefore, the amount of filler metal must be maintained within the upper limit to ensure a satisfactory brazing pass rate. The influence of brazing gap on brazing is shown in the following table. When other conditions are the same, the larger the gap, the smaller the brazing strength. This includes both the lateral brazing gap and the brazing gap at the step.

[0035] Table 1. Brazing parameters and strength values of performance test pieces.

[0036]

[0037] A process for brazing titanium alloy injectors utilizes a paste brazing filler metal. The paste brazing filler metal is prepared using a weight ratio of powdered filler metal to binder of (1:3.5) to (1:4.5). A larger ratio results in a lower paste brazing filler metal concentration, which results in a smaller proportion of powdered filler metal. This can lead to insufficient filler metal during brazing, preventing partial brazing seams from forming, or failing to meet the required brazing rate. Based on the specific ratio and product structure, a recommended filler metal amount of (1.5-2) times the amount required to fully fill the seam has been developed. The amount of filler metal significantly impacts brazing quality. Excessive filler metal content can result in insufficient filler metal or incomplete fillet angles, reducing post-braze hydraulic and airtightness, and potentially causing leakage if pressure requirements are not met. Excessive filler metal content can cause filler metal to overflow, affecting product appearance.

[0038] The adhesive should completely evaporate during brazing heating, leaving no carbon deposits or residue, and preventing contamination of the vacuum furnace. After assembly, perform an X-ray inspection of the injector cavity to ensure there is no brazing material accumulation or blockage in the bottom channel. Do not invert or tilt parts containing brazing material during assembly.

[0039] A process method for brazing titanium alloy injectors includes pre-weld cleaning. Before brazing, the parts are cleaned with gasoline, then cleaned with anhydrous ethanol, or ultrasonic cleaning can be used; for chemical cleaning, when the oxide film is thin, pickling can be performed with a nitric acid-hydrofluoric acid aqueous solution. When the oxide film is thick, alkaline cleaning is performed with a sodium hydroxide-sodium bicarbonate aqueous solution, and then pickling is performed with a nitric acid-hydrofluoric acid aqueous solution. Pay attention to the protection of the nozzle hole.

[0040] A process for brazing a titanium alloy injector is characterized by comprising the following steps.

[0041] a) Place the parts into the furnace and secure them with the injector fastener to ensure the levelness is within 0.1mm;

[0042] b) Vacuuming: pre-vacuum degree is not less than 5×10 -3 Pa, the vacuum degree during heating, brazing and strengthening process shall not be less than 4×10 -2 Pa;

[0043] c) Heating: (300-500)°C, heating time (50-100) min, heating rate (3-8)°C / min, holding time (10-30) min;

[0044] d) Heating: (600-800)°C, heating time (60-120) min, heating rate (3-8)°C / min, holding time (10-30) min;

[0045] e) Brazing: Raise the furnace temperature to (920-980)°C, heating time (20-40) min, heating rate (3-8)°C / min, hold for (8-25) min;

[0046] f) Post-weld strengthening: furnace temperature drops to (800-900)°C ± 10°C, and keeps warm for (1-4) hours;

[0047] g) The cooling time should be no less than 4 hours. Vacuuming should be continued during cooling. After cooling to below 40°C, stop vacuuming and take out the parts.

[0048] The brazing parameters of this process method are more refined and more accurate. At the same time, a large number of brazing products have been found to increase the (300-500)℃, (600-800)℃, and insulation sections. The (300-500)℃ insulation section can stably volatilize the adhesive without splashing, while the (600-800)℃ insulation section can even out the internal and external temperatures of the parts, so that the parts and brazing material are heated evenly. It can be determined according to the size and data of the parts, so as to achieve consistent brazing effects inside and outside the parts.

[0049] Table 2, comparison table of insulation time.

[0050]

[0051] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for brazing titanium alloy injectors, characterized in that: The steps include: a) Place the part in the furnace and secure it with an injector brazing fastener, ensuring a levelness within 0.1 mm. A titanium alloy injector brazing fastener is used to secure the injector. The fastener includes a counterweight and a mounting base, with the injector positioned between the counterweight and the mounting base. The counterweight has a transparent aperture for degassing the brazing material and adhesive during brazing. The counterweight contacts the injector's apertured surface where no aperture is present. The injector includes an upper cover, a middle layer, and a lower base connected by brazing, employing a plug-in brazing seam. The width of the annular groove for arranging the brazing material is generally 1-2 mm, and the height of the groove to be brazed is generally 1.4-1.9 mm. The annular groove is narrow. b) Vacuuming: pre-vacuum degree is not less than 5×10 -3 Pa, the vacuum degree during heating, brazing and strengthening process shall not be less than 4×10 -2 Pa; c) Heating: (300-500)°C, heating time (50-100) min, heating rate (3-8)°C / min, holding time (10-30) min; d) Heating: (600-800)°C, heating time (60-120) min, heating rate (3-8)°C / min, holding time (10-30) min; e) Brazing: Raise the furnace temperature to (920-980)°C, heating time (20-40) min, heating rate (3-8)°C / min, hold temperature (8-25) min; f) Post-weld strengthening: furnace temperature drops to (800-900)°C ± 10°C, and keeps warm for (1-4) hours; g) The cooling time shall be no less than 4 hours. Vacuuming shall be continued during cooling. After cooling to below 40°C, stop vacuuming and remove the parts.

2. A process for brazing titanium alloy injectors according to claim 1, characterized in that: The basic parameters of the vacuum brazing furnace are as follows: the maximum heating temperature is above 1100℃, the normal working temperature is 960℃, the time for the empty furnace to heat up to 1100℃ is ≤ 2h; the furnace temperature uniformity meets ±5℃; the temperature control accuracy meets ±2; the vacuum furnace temperature uniformity zone should cover the position of the brazing parts, and the vacuum degree during the brazing process is required to be better than 4×10 -2 Pa, titanium alloy brazing process requires vacuum better than 4 × 10 -2 Pa, the cold pressure rise rate should be less than 0.67Pa / h.

3. The process for brazing titanium alloy injectors according to claim 1, characterized in that: The injector material is TC4 or TC10, the solder grade is Type 1510 (MBF-5002), the melting temperature is (820-860)°C, the solder is in powder form, and the particle size is 50-100 meshes.

4. The process for brazing titanium alloy injectors according to claim 1, characterized in that: Set the brazing gap to: (0.05-0.1) mm.

5. The process for brazing titanium alloy injectors according to claim 1, characterized in that: The solder is in paste form, and the weight ratio of the paste solder to the binder is (1:3.5) to (1:4.5).

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