Flame stabilizer and preparation method

Abstract

The invention provides a flame stabilizer and a preparation method. The flame stabilizer comprises an evaporation tank frame, a wind scoop, an oil gas pipe, a rib plate, a lifting lug and a long lifting lug. The selective laser melting forming process is improved, the product quality is guaranteed, meanwhile, the product machining procedures, the tool number and the period are reduced, the manufacturing cost is reduced, and the method is suitable for batch industrial production.

Description

Technical Field

[0001] The present invention relates to a flame stabilizer and a preparation method thereof, belonging to the technical fields of aircraft engines and laser additive manufacturing. Background Art

[0002] With the progress of technology, the thrust-to-weight ratio of aero-engines has been continuously improved, and the temperature rise in the combustion chamber and the working temperature of the combustion chamber have also been continuously increased. The requirements for the high-temperature resistance, creep resistance, etc. of the materials of the combustion chamber, especially the flame tube, are becoming increasingly strict. At present, in the combustion chamber of aero-engines, especially in the flame tube of annular combustion chambers, technologies such as air-cooling and thermal barrier coatings are widely used to achieve the maximum temperature rise in the combustion chamber based on existing materials and improve the overall performance of the combustion chamber and the engine.

[0003] The stabilizer mainly functions to stabilize the flame in the high-speed airflow of the engine combustion chamber and ensure reliable combustion. It is necessary to ensure stable, sufficient and smooth airflow, especially the fluidity of the oil and gas pipelines of the stabilizer. In addition, the stabilizer needs to withstand the high-temperature and high-pressure oncoming flow impact during the operation of the engine. The overall structure of the stabilizer is a thin-walled special-shaped curved surface structure. The traditional sheet metal welding process plan cannot be formed in one step. It needs to be processed from multiple thin-walled parts such as an evaporation tank frame, a wind scoop, oil and gas pipelines, rib plates, an upper cover, a lower plate, and a hinge bracket through processes such as machining, sheet metal forming, heat treatment to remove stress, combined welding, post-weld shaping, post-weld stress relief, laser drilling, and finishing. The parts have many supporting levels, a long process flow, a long production cycle, many special toolings, a long manual argon arc weld, need to go through multiple heat treatments, and have a high cost.

[0004] Adopting the selective laser melting forming plan can realize the integral forming of the stabilizer, without the need for multiple parts to be matched, avoiding problems such as large forming difficulty, large welding deformation, and long processing cycle in the sheet metal welding processing plan, and can improve production efficiency.

[0005] The structure of the flame stabilizer is as Figure 2 、 3 shown, which is a thin-walled special-shaped curved surface structure. The selective laser melting forming process is multi-layer powder spreading. In the forming process, the area below 45 does not have the self-supporting forming condition. When using a support structure to assist in forming, the formed surface is prone to warping and deformation. Moreover, the flame stabilizer is a symmetrical structure as a whole, in which the oil and gas pipeline and the evaporation tank frame are in a cross-shaped structure, and stress shrinkage lines are likely to appear during the forming of the wind scoop. The evaporation tank frame is an open thin-walled structure, and the deformation is relatively large during laser printing and post-processing. The lug with a relatively large wall thickness is a sudden change structure relative to the evaporation tank frame, further aggravating the deformation degree during the forming process. As an engine part, the stabilizer has high requirements for the product appearance, mating dimensions and surface quality. Summary of the Invention

[0006] An object of the present invention is to overcome one of the deficiencies of the prior art and provide a flame stabilizer and a preparation method thereof.

[0007] Technical solution of the present invention: A method for preparing a flame stabilizer. The flame stabilizer includes an evaporation tank rack, a wind funnel, an oil and gas pipe, a rib plate, a lifting lug, and a long lifting lug, and is realized through the following steps:

[0008] First step, establish a three-dimensional model of the flame stabilizer, add an anti-deformation structure and add machining allowance;

[0009] Second step, optimize the placement angle,

[0010] The placement angle is that the oil and gas pipe and the evaporation tank rack form an angle of 45° with the printing platform, the long lifting lug structure is above, the angle between the axis of the wind funnel and the platform is α, and the opening of the wind funnel is obliquely upward;

[0011] Third step, add targeted support structures to the three-dimensional model in regions and perform model slicing and assignment processing;

[0012] Fourth step, selective laser melting forming to obtain a flame stabilizer blank;

[0013] Fifth step, separate the flame stabilizer blank from the substrate and the external support structure;

[0014] Sixth step, perform solution strengthening vacuum heat treatment;

[0015] Seventh step, remove the anti-deformation structure, the internal support structure and the reserved machining allowance to obtain the flame stabilizer.

[0016] A flame stabilizer obtained by using any of the above preparation methods.

[0017] Beneficial effects of the present invention compared with the prior art:

[0018] (1) By improving the selective laser melting forming process, the present invention not only reduces the product processing procedures, the number of toolings and the cycle, but also reduces the manufacturing cost while ensuring the product quality, and is suitable for batch industrial production;

[0019] (2) By a special method, the present invention determines a suitable forming placement angle. On the premise of ensuring that as many surfaces of the oil and gas pipe and the evaporation tank rack are self-supporting formed as possible, the wind funnel closes slowly during forming, thereby eliminating the stress shrinkage line of the wind funnel forming;

[0020] (3) The present invention adds a bottom plate structure to the evaporation tank rack to form a closed structure for the evaporation tank rack, and then removes it after subsequent heat treatment, thereby controlling the deformation problem of the evaporation tank rack;

[0021] (4) The present invention adds a strong support structure combining a block support and a cone support and connects it to the substrate, thereby achieving the control of deformation problems such as sudden change structures;

[0022] (5) The support structure of the present invention extends into the product surface to a certain depth. During the product forming process, the surface-to-point contact is changed to surface-to-surface contact at the contact surface to prevent point-to-surface contact. Due to stress contraction, there is not enough bonding strength between the support structure and the product on the contact end face, resulting in product detachment and warping deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flowchart of the present invention;

[0024] Figure 2 is a schematic three-dimensional structure diagram of a flame stabilizer;

[0025] Figure 3 is a view of the flame stabilizer of the present invention;

[0026] Figure 4 is a schematic diagram of the placement angle of the present invention, where a and b are views at different angles;

[0027] Figure 5 is a schematic diagram of the inclination angle of the present invention;

[0028] Figure 6 is a schematic diagram of the simplified tubular structure of the air scoop of the flame stabilizer of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be described in detail below with reference to specific examples and the accompanying drawings.

[0030] The present invention provides a method for manufacturing a flame stabilizer as Figure 1 shown, which is achieved through the following steps:

[0031] The first step is to establish a three-dimensional model of the flame stabilizer, add an anti-deformation structure, and add machining allowances.

[0032] Furthermore, in this step, a bottom plate is added to the bottom of the evaporation tank rack to make the evaporation tank rack a closed structure. In view of the problem that the evaporation tank rack of the stabilizer is prone to deformation during the laser forming process, the present invention adopts the addition of a bottom plate structure to design the evaporation tank rack as a closed structure to control deformation.

[0033] Furthermore, according to the characteristics of the additive manufacturing process of the flame stabilizer and the requirements of the post-processing technology, 0.1 mm to 0.5 mm of grinding and machining allowances are added to different regions. The specific process allowance design can refer to the existing technology.

[0034] Furthermore, the edge structures of the three-dimensional model of the flame stabilizer are all rounded to avoid stress concentration caused by sudden changes in the product structure.

[0035] The specific establishment of the three-dimensional model in this step can be processed using existing software, such as UG three-dimensional modeling software, etc.

[0036] The flame stabilizer prepared by the present invention is as follows Figure 2 , 3 shown, mainly including an evaporation tank rack, a wind scoop, an oil and gas pipe, a rib plate, a lifting lug, a long lifting lug (away from the axis of the wind scoop), etc. Among them, the evaporation tank rack, the wind scoop, the oil and gas pipe, the rib plate, etc. are thin-walled structures. The evaporation tank rack is an open-type special-shaped curved thin-walled structure. The evaporation tank rack and the oil and gas pipe are integrally in a cross structure. The wind scoop is a single-side open cylindrical structure.

[0037] Step 2: Optimize the placement angle.

[0038] In this step, the placement angle is that the oil and gas pipe and the evaporation tank rack form a 45° angle with the printing platform, and the long lifting lug structure is above; the angle between the axis of the wind scoop and the platform is α, and the opening of the wind scoop is obliquely upward.

[0039] As Figure 4 shown in a, based on the cross structure of the oil and gas pipe and the evaporation tank rack of the present invention, when placing, the oil and gas pipe and the evaporation tank rack form a 45° angle with the printing platform (substrate) to ensure that the long lifting lug structure is placed in the upper state. As Figure 4 shown in b, the stabilizer as a whole is tilted at a certain angle. The angle between the axis of the wind scoop and the printing platform is α, and the opening of the wind scoop is obliquely upward to avoid structural mutation of the wind scoop during the forming process, resulting in stress shrinkage lines.

[0040] The wind scoop of the flame stabilizer is similar to a circular tube. If it is placed horizontally, during the laser forming process, when the circular tube turns from an open state to a closed state, the cross-sectional area scanned by the scanning laser changes suddenly, which will form stress shrinkage lines, resulting in overall deformation of the structure of this transition layer. The change process is as Figure 5 shown. To avoid cross-sectional mutation during the forming process, the tube structure is tilted at a certain angle along the axis.

[0041] Furthermore, as Figure 6 described, the present invention provides a method for quickly determining the tilt angle α,

[0042]

[0043] where α is the tilt angle (the angle between the axis of the wind scoop and the printing platform), d is the wall thickness of the wind scoop, and h is the height of the wind scoop.

[0044] Further preferably, α is 5° - 7°.

[0045] Based on the forming characteristics of the oil and gas pipe, the evaporation tank rack and the wind scoop, the present invention optimizes the placement angle. On the premise of ensuring as many self-supporting forming of the oil and gas pipe and the evaporation tank rack as possible, the wind scoop closes slowly during forming, thereby eliminating the stress shrinkage lines in the forming of the wind scoop.

[0046] This step can set the placement angle in existing software, such as existing Magics software, etc.

[0047] In the third step, targeted support structures are added to the 3D model in regions and the model is sliced and assigned values for processing.

[0048] Based on the printing placement posture, for regions with an angle lower than 45° during the forming process, block supports or cone support structures are added to ensure the forming of the surface, achieve deformation stress control and heat conduction. Among them, block supports are added to the evaporation tank frame, and cone supports are added to the air scoop. The support structure at the stabilizer lug adopts a combined scheme of solid support and segmented block support. The section connected to the substrate is a hollow cylindrical solid support, and the section connected to the product adopts a block support structure.

[0049] For the specific support structure design, the principles of support structures in the prior art can be referred to.

[0050] In the fourth step, selective laser melting forming is carried out to obtain a flame stabilizer blank.

[0051] Furthermore, in this step, the contact surface between the support structure and the product penetrates a certain depth to ensure the connection strength between the support and the product body. During the selective laser melting forming process, on the scanning plane at this depth, the position of the support structure is scanned once first and then the product body is scanned as a whole.

[0052] Furthermore, the penetration depth of the contact surface between the support structure and the product is preferably 0.15 mm to 0.25 mm.

[0053] Furthermore, the selective laser melting forming is carried out in a protective atmosphere.

[0054] This step also includes cleaning the residual powder on the flame stabilizer blank.

[0055] This step adopts the selective laser melting forming process, which is determined according to the types of selective laser melting forming powders used and the equipment models.

[0056] In the fifth step, the flame stabilizer blank is separated from the substrate and the external support structure.

[0057] In this step, existing mechanical methods such as wire cutting can be used for processing, and the surface of the product is polished.

[0058] In the sixth step, solution strengthening vacuum heat treatment is carried out.

[0059] This step is a well-known technology in the art, and those skilled in the art can refer to the well-known technology to select appropriate process parameters.

[0060] In the seventh step, the anti-deformation structure, internal support structure and process reserves are removed to obtain the flame stabilizer.

[0061] In this step, existing mechanical methods such as wire cutting can be used for processing, and the surface of the product is polished and sandblasted and other processes are carried out to improve the surface quality. After completion, the reserved allowance is removed by machining.

[0062] Furthermore, the present invention also provides a flame stabilizer obtained by the above preparation method.

[0063] Embodiment

[0064] In this example, a flame stabilizer as shown in Figure 2 , 3 is prepared by selective laser melting forming method. The flame stabilizer mainly includes structures such as an evaporation tank frame, a wind scoop, an oil and gas pipe, a rib plate, and a lifting lug. Among them, the wall thicknesses of the evaporation tank frame, the wind scoop, the oil and gas pipe, the rib plate, etc. are thin-walled structures with a thickness of 1 mm to 2 mm. The evaporation tank frame is an open-type special-shaped curved surface thin-walled structure. The evaporation tank frame and the oil and gas pipe are integrally in a cross-shaped structure. The wind scoop is a single-side open cylindrical structure.

[0065] 1. Establish a three-dimensional model of the flame stabilizer, add anti-deformation structures and process allowances.

[0066] Use UG software to establish a three-dimensional model of the flame stabilizer, add process allowances, design a closed anti-deformation structure, and perform fillet processing. According to the characteristics of the additive manufacturing forming process of the stabilizer and the requirements of the post-processing technology, add 0.1 mm to 0.5 mm of grinding and machining allowances for different regions.

[0067] The combined edge of the evaporation tank frame and the wind scoop is rounded with a radius of R1, the joint between the evaporation tank frame and the oil and gas pipe is rounded with a radius of R0.5, the joints between the rib plate and the oil and gas pipe and the wind scoop are rounded with a radius of R0.5, the joint between the lifting lug and the evaporation tank frame is rounded with a radius of R2, and the other edge structures are rounded with a radius of R0.5.

[0068] After the three-dimensional processing of the stabilizer is completed, export the model in STL format. The chord tolerance for export is 0.0025, and the angular tolerance is 6.0.

[0069] 2. Optimize the placement angle.

[0070] Import the TSL model of the stabilizer into Magics software to optimize the placement angle. The oil and gas pipe and the evaporation tank frame form a 45° angle with the printing platform (substrate).

[0071] In this example, the wind scoop of the flame stabilizer involved has a height of 29 mm and a wall thickness of 2.5 mm. Substitute the data into the formula to calculate the inclination angle During the model processing, the inclination angle is rounded, and the inclination angle should not be too large, which is not conducive to the forming of other structures. Therefore, the inclination angle α is taken as 5°.

[0072] 3. Add targeted support structures to the three-dimensional model in different regions and perform model slicing and assignment processing.

[0073] Based on the placement posture of the product during printing, for areas below 45° during the forming process, block supports or cone support structures are added to ensure the forming of the surface, achieve deformation stress control and heat conduction. Among them, block supports are added to the evaporation tank frame, and cone supports are added to the air scoop. The support structure at the long lug of the stabilizer adopts a combined scheme of solid support and segmented block support. The section connected to the substrate is a hollow cylindrical solid support with a wall thickness of 1 mm, a cylinder diameter of 25 mm, and a cylinder height of 175 mm. The section connected to the product adopts a block support structure.

[0074] The set parameters of the added supports are as follows:

[0075] Set parameters of block support: small grid size 0.6×0.6 mm, segmentation size 6×6 mm, no outer contour, penetration depth into the product in contact 0.2 mm;

[0076] Large grid size 3×3 mm, with outer contour, penetration depth into the product in contact 0.2 mm;

[0077] Set parameters of cone support: small column diameter 0.5 mm, small column spacing 1 - 1.5 mm, penetration depth into the product in contact of the small column 0.2 mm.

[0078] 4. Selective laser melting forming is carried out to obtain the blank of the flame stabilizer.

[0079] The layer thickness of the stabilizer model with support structure and the in - furnace specimen is 0.04 mm. Filling process parameters: laser power 250 W, scanning speed 1000 mm / s, scanning spacing 0.1 mm.

[0080] GH3536 superalloy powder is used for the laser forming of the stabilizer. Chemical composition: Fe 18.16 wt.%; C 0.065 wt.%; Cr 21.24 wt.%; Co 2.10 wt.%; W 0.59 wt.%; Mo 9.34 wt.%; Al 0.021 wt.%; Ti < 0.01 wt.%; P < 0.01 wt.%; S < 0.005 wt.%; Si 0.074 wt.%; Mn < 0.01 wt.%; Cu < 0.01 wt.%; Ni balance.

[0081] Particle size distribution: 15 - 53 μm, D10: 20.04 μm, D50: 34.97 μm, D90: 56.26 μm;

[0082] Flowability: 14.5 s / 50 g.

[0083] A powder - spreading type selective laser melting forming equipment is adopted. Stainless steel substrate and soft squeegee are selected, with one - way powder spreading and layer - by - layer scanning and printing for forming. During the printing process, the argon gas atmosphere with positive pressure in the forming chamber is always controlled, and the oxidation content ≤ 200 ppm.

[0084] After printing and forming, it is cooled in an argon environment. After the substrate is cooled below 35°C, the chamber is opened, and a vacuum material machine and a wet explosion-proof vacuum cleaner are used to clean the powder, and the powder in the stabilizer oil and gas pipeline and the support is cleaned to obtain a flame stabilizer blank with a support structure grown on the substrate.

[0085] During the selective laser melting forming process, on the scanning plane at the penetration depth of the support structure, the position of the support structure is scanned once first, and then the product body is scanned as a whole.

[0086] 5. Separate the flame stabilizer blank from the substrate and the external support structure.

[0087] Use a fast wire electrical discharge wire cutting machine to separate the stabilizer blank with a support structure grown on the substrate from the substrate. The cutting wire is parallel to the substrate, and the distance from the substrate is less than 1 mm. The coolant is a water-soluble emulsion. Use a pneumatic tool to remove the block support outside the stabilizer evaporation tank frame, the entity and block support at the lifting lug, and the conical support in the air scoop, and use a pneumatic grinding pen to polish the support area and the entire outer surface, with the required surface roughness of the polished surface ≤ Ra6.3.

[0088] 6. Perform solution strengthening vacuum heat treatment.

[0089] The solution strengthening heat treatment of the flame stabilizer is carried out in a vacuum heat treatment furnace. The heat treatment system is: heating rate 5 - 10°C / min, temperature 1175 ± 10°C, holding for 1 h, rapid cooling with argon filling, and opening the furnace for cooling to room temperature after the furnace temperature drops below 100°C.

[0090] 7. Remove the anti-deformation structure, internal support structure and process reservation to obtain the flame stabilizer.

[0091] Use a medium wire electrical discharge wire cutting machine to cut and separate the anti-deformation bottom plate of the stabilizer. Subsequently, use a pneumatic tool to remove the block support and conical support in the stabilizer evaporation tank frame, use a pneumatic grinding pen to polish the support area and the inner surface of the tank frame, and control the wall thickness of the evaporation tank frame to be 1.5 ± 0.1 mm, with the required surface roughness of the polished surface ≤ Ra6.3.

[0092] Use a sandblasting machine to perform overall sandblasting treatment on the outer surface of the stabilizer to improve the surface quality. After sandblasting, use a lathe to machine and remove the remaining allowance reserved for the air scoop, use a milling machine to machine and remove the remaining allowance reserved for the lifting lug, and machine the lifting lug assembly hole, with the required surface roughness of the machined surface ≤ Ra3.2.

[0093] Perform quality and performance tests on the prepared flame temperature device.

[0094] The surface quality of the finished flame stabilizer is inspected by non-destructive penetrant fluorescence to check the surface quality of the product. The inspection is carried out according to HB / Z61, using Class I Method A for inspection, and the inspection sensitivity is at Level 2. It is required that there are no cracks, lack of fusion, pores and other defects visible to the naked eye on the surface. The internal quality of the product is inspected by X-ray, and the inspection is carried out according to the provisions of GJB1187A-2001. The internal quality meets the requirements of Q / SB 826-2019, and there are no cracks and lack of fusion defects allowed inside the product structure. Measure the external dimensions of the product. Detect the room temperature and high temperature mechanical properties of the test bars in the furnace. Among them, the room temperature mechanical property inspection is carried out according to GB / T228.1-2010, and the 650°C high temperature mechanical property inspection is carried out according to GB / T 228.2-2015 to ensure that the stabilizer product meets the use requirements. The mechanical property results are shown in Table 1, and all indicators meet the design requirements.

[0095] Table 1

[0096]

[0097] For the stabilizer manufactured by the selective laser melting forming method described in the present invention, the engine using this stabilizer has passed the long-term, large-load, high-temperature and high-pressure ground intensified assessment test. After the test, the stabilizer structure is intact, without obvious ablation and deformation. The test shows that the additive manufacturing stabilizer is basically consistent with the existing sheet metal welded stabilizer in terms of various performance indicators of the engine.

[0098] The parts not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A method for preparing a flame stabilizer, the flame stabilizer comprising an evaporator frame, a wind scoop, an oil and gas pipe, a rib plate, a lifting lug and a long lifting lug, characterized in that: This is accomplished by following these steps: The first step is to build a three-dimensional model of the flame stabilizer, add anti-deformation structure and add process margin; The second step is to optimize the placement angle. The placement angle is that the oil and gas pipes and the evaporation tank frame form a 45° angle with the printing platform, the long ear structure is on the top, the angle between the wind bucket axis and the platform is α, and the wind bucket opening is inclined upward; The third step is to add targeted support structures to the 3D model in different regions and perform model slice assignment processing; The fourth step is laser selective melting to obtain a flame stabilizer blank; Step 5, the flame stabilizer blank is separated from the base plate and the external support structure; Step 6: Perform solid solution strengthening vacuum heat treatment; In the seventh step, the anti-deformation structure, the internal support structure and the reserved process margin are removed to obtain the flame stabilizer.

2. A method for preparing a flame stabilizer according to claim 1, characterized in that: In the first step, the anti-deformation structure is added by adding a bottom plate at the bottom of the evaporation tank frame, so that the evaporation tank frame is a closed structure.

3. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the first step, according to the characteristics of the flame stabilizer additive manufacturing forming process and the requirements of the post-processing process, 0.1 mm to 0.5 mm of grinding and machining allowances are added to different areas.

4. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the first step, the edge structures of the three-dimensional model of the flame stabilizer are all rounded.

5. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the second step, the angle α between the wind bucket axis and the platform is determined according to the following formula: Among them, α is the inclination angle (the angle between the axis of the wind scoop mouth and the printing platform), d is the wall thickness of the wind scoop, and h is the height of the wind scoop.

6. A method for preparing a flame stabilizer according to claim 5, characterized in that: In the second step, α is 5° to 7°.

7. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the third step, solid support, block support or cone support structure is added to the area below 45° during the forming process.

8. A method for preparing a flame stabilizer according to claim 7, characterized in that: In the third step, the evaporation tank frame is added with block support, the wind scoop is added with cone support, the lifting ears and long lifting ears are added with a support structure combining solid support and block support in sections, the section connected to the base plate is a hollow cylindrical solid support, and the section connected to the product adopts a block support structure.

9. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the fourth step, the support structure and the contact surface of the product are penetrated to a certain depth. During the laser selective melting forming process, on the scanning surface located at the depth, the position of the support structure is scanned once and then the product body is scanned as a whole.

10. A method for preparing a flame stabilizer according to claim 9, characterized in that: In the fourth step, the penetration depth of the support structure into the contact surface of the product is in the range of 0.15 mm to 0.25 mm.

11. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the fourth step, the laser selective melting is performed in a protective atmosphere.

12. The method for preparing a flame stabilizer according to claim 1, characterized in that: In the fifth and seventh steps, wire cutting is used and the surface of the product is polished.

13. A flame stabilizer obtained by any of the above preparation methods.

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