A flame tube manufacturing method based on laser powder bed fusion additive manufacturing technology

Abstract

The present invention belongs to the technical field of aero-engine manufacturing, and relates to a flame tube manufacturing method based on laser powder bed melting additive manufacturing technology; the method first pre-processes the established three-dimensional digital model of the flame tube: when processing the three-dimensional digital model of the flame tube, support is added to the digital model of the flame tube, and the contact position between the support structure and the surface of the flame tube is the position of the outer surface of the cooling hole; and an allowance is added to the cooling hole position on the outer surface of the three-dimensional digital model of the flame tube that is not covered by the support structure, and the support and the allowance are both cylindrical structures with a height of 1 to 5 mm; then the digital model is sliced, and the flame tube is prepared by laser powder bed melting additive manufacturing; finally, the support is removed, and the cooling hole is processed based on the position of the support and the allowance to complete the flame tube manufacturing. The unique support and allowance addition scheme ensures the position accuracy of the small-sized cooling holes on the flame tube, and meets the high-quality, high-precision and high-efficiency manufacturing of complex thin-walled structures and small-sized cooling holes.

Description

Technical Field

[0001] The invention belongs to the technical field of aero-engine manufacturing, and relates to a flame tube manufacturing method based on laser powder bed melting additive manufacturing technology. Background Art

[0002] Flame tubes are usually made of high-temperature alloys and are mainly used to mix atomized fuel with air for combustion. The high-temperature and high-pressure gas generated drives the turbine to rotate. Flame tubes are one of the key components of the combustion chamber of aircraft engines. With the rapid improvement of aircraft engine performance, flame tubes are also developing in the direction of integration and complexity. It is extremely difficult to manufacture flame tubes using traditional processes.

[0003] Laser powder bed fusion additive manufacturing technology is a near-net-shape technology suitable for high-quality rapid manufacturing of complex structural parts. However, the surface roughness of the parts formed by this technology is relatively high, and the surface quality must be improved by surface treatment methods such as abrasive flow polishing, electrochemical polishing, sandblasting or chemical polishing before use. There are a large number of small-sized cooling holes with a diameter of about 1 mm distributed on the surface of the flame tube. It is difficult for existing surface treatment methods to effectively treat the inner surface of such small-sized cooling holes, such as:

[0004] Abrasive flow technology improves the roughness of the part surface by repeatedly rubbing the abrasive against the part surface. However, when performing internal surface treatment, abrasive that cannot be cleaned will remain in the hole. Electrochemical polishing technology improves the roughness by setting a cathode with the same shape as the surface to be treated on the part surface, using electrochemical reaction. However, the cooling hole has a small diameter and an irregular shape, so a cathode cannot be set in the hole. Sand blasting technology improves the roughness by using high-speed sand shots to impact the part surface. However, the cooling hole has a small diameter and an irregular shape, so the sand shots cannot fully reach the inner surface, resulting in poor treatment effect. Chemical polishing improves the roughness by chemically corroding the surface of the part with chemical polishing liquid. Chemical polishing liquid usually pollutes the environment and may have adverse effects on the health of operators. Therefore, the use of this technology is greatly restricted.

[0005] Various problems existing in existing surface treatment methods result in the inner surface roughness of the cooling holes of the laser powder bed fusion additive manufacturing flame tube being difficult to meet the requirements of use, which becomes a key obstacle restricting the application of laser powder bed fusion additive manufacturing flame tubes.

[0006] When using laser powder bed fusion additive manufacturing technology to prepare parts, support structures need to be set up for the suspended parts and thin-walled parts of the parts to prevent the parts from deformation and cracking. The support structure is formed together with the part and can be regarded as a part of the part. It is possible to consider giving the support structure more functions and playing a greater role in the additive manufacturing process. However, the existing support structure designs only focus on ensuring the stability of the parts during the manufacturing process and the forming quality of the parts after manufacturing. The potential role of the support structure has not yet been fully utilized. Summary of the invention

[0007] The purpose of the present invention is to provide a flame tube manufacturing method based on laser powder bed melting additive manufacturing technology. In order to solve the problem of high surface roughness of small-sized cooling holes on the surface of the flame tube manufactured by laser powder bed melting additive manufacturing, different ideas are proposed for the support loading of small holes on the surface of the flame tube.

[0008] To solve this technical problem, the technical solution of the present invention is:

[0009] A flame tube manufacturing method based on laser powder bed fusion additive manufacturing technology is provided. After establishing a three-dimensional model of the flame tube, the method first pre-processes the established three-dimensional digital model of the flame tube:

[0010] When processing the three-dimensional digital model of the flame tube, support is added to the digital model of the flame tube. The contact position between the support structure and the surface of the flame tube is the position of the outer surface of the cooling hole; and the margin is added to the position of the cooling hole on the outer surface of the three-dimensional digital model of the flame tube that is not covered by the support structure;

[0011] Then the digital mold is sliced ​​and the flame tube is prepared by laser powder bed fusion additive manufacturing;

[0012] Finally, the supports are removed, and cooling holes are processed based on the positions of the supports and allowances to complete the flame tube manufacturing.

[0013] The contact position between the support structure and the flame tube surface is the position for subsequent drilling. The support structure in contact with the flame tube surface is a cylinder, and the diameter of the cylinder is the same as the diameter of the cooling hole.

[0014] The margin added to the surface of the cooling hole is a cylinder with a height of 1 to 5 mm, and the diameter of the cylinder is the same as the diameter of the cooling hole.

[0015] The method steps are as follows:

[0016] 1) Use 3D graphics software to build the flame tube CAD model;

[0017] 2) Use 3D digital model processing software to add support to the flame tube digital model. The contact position between the support structure and the flame tube surface is the location of the outer surface of the cooling hole;

[0018] 3) For cooling holes whose outer surfaces are not covered by the supporting structure, add margins on the outer surfaces of the cooling holes through 3D digital model processing software;

[0019] 4) Slice and fill the flame tube digital model after adding support and margin;

[0020] 5) Preparation of flame tube by laser powder bed fusion additive manufacturing equipment;

[0021] 6) Clean the surface of the flame tube and the powder inside the support after forming;

[0022] 7) Perform stress relief annealing on the flame tube after forming;

[0023] 8) Separate the support from the substrate and the part from the support;

[0024] 9) Hot isostatic pressing and heat treatment of the flame tube;

[0025] 10) Process cooling holes on the surface of the flame tube;

[0026] 11) Perform sandblasting on the surface of the flame tube to complete the flame tube manufacturing.

[0027] Preferably, in step 8), the support structure is separated from the flame tube surface by using wire cutting technology.

[0028] Preferably, in step 8), when the part is separated from the support, a support structure with a height of 1 to 5 mm is retained on the surface of the flame tube.

[0029] Preferably, in step 10), the cooling holes are processed by electric spark machining technology or laser drilling technology.

[0030] In step 10), the processing position is the support structure retained on the surface of the flame tube or the pre-set margin, and the cooling hole processing process removes all the remaining support structure and the pre-set margin.

[0031] Preferably, the height of the margin added on the surface of the cooling hole in step 3) is 2 to 3 mm.

[0032] The beneficial effects of the present invention are:

[0033] There are a large number of small-sized cooling holes distributed on the surface of the flame tube. It is difficult to process the inner surface of the cooling holes using existing surface treatment methods, which limits the application of additively manufactured flame tubes. In response to this problem, the present invention uses a unique support and allowance addition scheme to set the support structure at the location of the outer surface of the flame tube cooling hole, and add allowances to the locations of the cooling holes on the outer surface of the flame tube that are not covered by the support structure, and then use electric spark machining technology or laser drilling technology to process the cooling holes according to the location of the support and allowance. Compared with the prior art, the support structure provided by the present invention not only prevents the parts from cracking and deforming, but also plays a positioning role for subsequent cooling hole processing. In addition, the support and allowance are added through three-dimensional digital model processing software to ensure that the cooling holes have good position accuracy. The method proposed in the present invention can achieve high-quality, high-precision, and high-efficiency manufacturing of thin-walled complex structure flame tubes and small-sized cooling holes, which greatly promotes the engineering application of additively manufactured flame tubes.

[0034] The present invention combines the advantages of laser powder bed fusion additive manufacturing technology, electrospark machining technology and laser drilling technology. The main structure of the flame tube is formed by laser powder bed fusion additive manufacturing technology, and small-sized cooling holes with high surface quality are manufactured by electrospark machining technology or laser drilling technology. The support and allowance adding scheme in the method of the present invention ensures the position accuracy of the small-sized cooling holes on the flame tube, which can meet the high-quality, high-precision and high-efficiency manufacturing of complex thin-walled structures and small-sized cooling holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions implemented in the present invention, the following is a brief explanation of the drawings required to be used in the examples of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A schematic diagram of a support and margin adding scheme in an embodiment of the method of the present invention;

[0037] Figure 2 for Figure 1 A partial enlarged view of the middle area A;

[0038] Figure 3 for Figure 1 A partial enlarged view of the middle area B;

[0039] Figure 4 A schematic diagram of the support structure and the remainder retained on the flame tube surface after the support is removed in an embodiment of the method of the present invention;

[0040] Figure 5 It is a partial cross-sectional view of the flame tube after the cooling hole processing is completed in the embodiment of the method of the present invention;

[0041] Figure 6 This is the rendering of the cooling hole directly formed by laser powder bed fusion additive manufacturing technology;

[0042] Figure 7 This is a rendering of a cooling hole formed by electrospark machining technology in an embodiment of the method of the present invention;

[0043] Figure numbers in the figure: 1 flame tube, 2 supporting structure, 3 cooling hole, 4 margin, 5 base plate. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] The features of various aspects of the embodiments of the present invention will be described in detail below, and the technical solutions of the present invention will be further described in detail in conjunction with the drawings and embodiments.

[0046] Step 1: Use the three-dimensional drawing software UG to create a CAD model of the flame tube 1.

[0047] Step 2: Use the 3D digital model processing software Magics to add support 2 to the digital model of the flame tube 1. The contact position between the support structure 2 and the surface of the flame tube 1 is the position of the outer surface of the cooling hole 3. The support structure 2 in contact with the surface of the flame tube 1 is a cylinder with a diameter of φ0.4mm.

[0048] Step 3: For the cooling holes 3 whose outer surfaces are not covered by the support structure 2, a cylindrical margin 4 with a diameter of φ0.4 mm and a height of 5 mm is added to the outer surface of the cooling holes 3 using the 3D digital model processing software Magics.

[0049] Step 4: Use the 3D digital model processing software Magics to slice and fill the digital model of the flame tube 1 with the support 2 and the margin 4 added.

[0050] Step 5: Using GH3536 alloy powder with a particle size of 15 to 53 μm as raw material, the flame tube is prepared by laser powder bed melting additive manufacturing equipment. The process parameters are: laser power 280 W, powder layer thickness 40 μm, scanning rate 1200 mm / s, and scanning spacing 0.1 mm.

[0051] Step 6: Clean the surface of the flame tube 1 and the powder inside the support 2 after forming.

[0052] Step seven: perform stress relief annealing on the formed flame tube 1, and the annealing system is: keep warm at 870°C for 1 hour and then air cool.

[0053] Step 8: Use wire cutting technology to separate the support 2 from the base plate 5, separate the flame tube 1 from the support 2, and do not completely remove the support structure 2 at the location of the cooling hole 3, and retain the support structure 2 with a height of 1 mm.

[0054] Step 9: Hot isostatic pressing and heat treatment are performed on the flame tube 1. The hot isostatic pressing system is: temperature 1170°C, pressure 120MPa, heat preservation and pressure holding time 4h. The heat treatment system is: temperature 1175°C, heat preservation time 2h, air cooling.

[0055] Step 10: Use electric spark machining technology to machine cooling holes 3 on the surface of the flame tube 1. The outer diameter of the cooling hole 3 is φ0.4mm. The machining position is the support structure 2 retained on the surface of the flame tube 1 and the added margin 4. During the machining process of the cooling hole 3, the remaining support structure 2 and the added margin 4 are completely removed.

[0056] Step 11: Perform sandblasting on the surface of the flame tube 1 to complete the manufacture of the flame tube 1.

[0057] from Figure 6 , Figure 7 The cooling holes formed by different processing technologies can be compared intuitively to find that Figure 7 The cooling hole formed by the method of the present invention has a better surface morphology, good quality and high precision. The cooling hole with a diameter of φ0.4 mm processed by the present invention is supported and positioned by the present invention, ensuring good position accuracy.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A method for manufacturing a flame tube based on laser powder bed fusion additive manufacturing technology, wherein the method establishes a three-dimensional model of the flame tube, and is characterized in that: First, the established flame tube three-dimensional digital model is preprocessed: when processing the flame tube three-dimensional digital model, support is added to the flame tube digital model, and the contact position between the support structure and the flame tube surface is the position of the outer surface of the cooling hole; In addition, an allowance is added to the position of the cooling holes on the outer surface of the three-dimensional digital model of the flame tube that are not covered by the support structure; then the digital model is sliced, and the flame tube is prepared by laser powder bed fusion additive manufacturing; finally, the support is removed, and the cooling holes are processed based on the position of the support and the allowance to complete the flame tube manufacturing; The contact position between the support structure and the surface of the flame tube is the position for subsequent drilling. The support structure in contact with the surface of the flame tube is a cylinder, and the diameter of the cylinder is the same as the diameter of the cooling hole. The margin added to the surface of the cooling hole is a cylinder with a height of 1 to 5 mm, and the diameter of the cylinder is the same as the diameter of the cooling hole.

2. The method according to claim 1, characterized in that: The specific steps of the method are as follows: 1) Use 3D graphics software to build the flame tube CAD model; 2) Use 3D digital model processing software to add support to the flame tube digital model. The contact position between the support structure and the flame tube surface is the location of the outer surface of the cooling hole; 3) For cooling holes whose outer surfaces are not covered by the supporting structure, add margins on the outer surfaces of the cooling holes through 3D digital model processing software; 4) Slice and fill the flame tube digital model after adding support and margin; 5) Preparation of flame tube by laser powder bed fusion additive manufacturing equipment; 6) Clean the surface of the flame tube and the powder inside the support after forming; 7) Perform stress relief annealing on the flame tube after forming; 8) Separate the support from the substrate and the part from the support; 9) Hot isostatic pressing and heat treatment of the flame tube; 10) Process cooling holes on the surface of the flame tube; 11) Perform sandblasting on the surface of the flame tube to complete the flame tube manufacturing.

3. The method according to claim 2, characterized in that: In step 8), the support structure is separated from the flame tube surface by using wire cutting technology.

4. The method according to claim 2, characterized in that: In step 8), when the part is separated from the support, a support structure with a height of 1 to 5 mm is retained on the surface of the flame tube.

5. The method according to claim 2, characterized in that: In step 10), the cooling holes are processed by using electric spark machining technology or laser drilling technology.

6. The method according to claim 2, characterized in that: In step 10), the processing position is the support structure retained on the surface of the flame tube or the pre-set margin, and the cooling hole processing process removes all the remaining support structure and the pre-set margin.

7. The method according to claim 1, characterized in that: The height of the margin added on the cooling hole surface is 2 to 3 mm.

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