Method for forming thin-wall round-to-square structure guide pipe through high-precision selective laser melting

Abstract

The invention relates to the technical field of additive manufacturing, and provides a method for forming a thin-wall round-to-square structure guide pipe through high-precision selective laser melting, and a three-dimensional model of the thin-wall round-to-square structure guide pipe is established. Placing the catheter three-dimensional model according to the optimal forming direction; adding an entity and a grid support on the lower surface of which the angles between the upper and lower ends of the outer surface of the circular ring part of the guide pipe and the horizontal direction are less than 45 degrees; and selective laser melting forming is conducted according to the three-dimensional model obtained after the support is added under the protection of inert gas, and a guide pipe blank with the base plate and the support is obtained. Removing residual powder; and carrying out heat treatment on the base plate and the guide pipe blank with the support. And the substrate and the guide pipe are cut through a linear cutting method, solid supports and grid supports are removed, polishing and sand blasting are conducted, and a guide pipe blank is obtained and used for subsequent machining. The method has the advantages that the problems of large manufacturing difficulty and large welding deformation of the guide pipe with the special-shaped structure are solved, the size out-of-tolerance is eliminated, the assembly precision is guaranteed, and the assembly efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for forming a thin-walled round-to-square structure conduit by high-precision laser selective melting. Background Art

[0002] Laser selective melting additive manufacturing technology is the most mature technology in the field of metal additive manufacturing. This technology has great flexibility and is less restricted by the complexity of the catheter structure during the forming process. It is suitable for the manufacture of catheters with various complex structures, especially for catheters with complex special-shaped structures that cannot be manufactured by conventional traditional methods. This technology does not require any special tooling and molds during the manufacturing process. It can directly manufacture catheters with complex structures based on three-dimensional digital models. It can quickly respond to changes in design structures, efficiently iterate processes, significantly reduce research and development and production cycles, and has high process controllability and stable and reliable performance. Therefore, it has become a new technology to solve the manufacturing bottleneck problem in the aerospace field and has been widely used in the aerospace field.

[0003] With the continuous development and maturity of the new generation of aircraft engine technology, the demand for the development of high-performance, high thrust-to-weight ratio engines has become increasingly significant, and the duct structure has tended to be complex and lightweight. The special-shaped round-to-square structure duct of aircraft engines is a typical type of difficult-to-process thin-walled duct, and has strict assembly requirements. When using traditional welding technology, the number of single pieces is large and the size is small. The manual welding of the spatial special-shaped structure is difficult. The thin-walled structure causes large welding deformation, resulting in excessive duct size, making it difficult to assemble the duct. The clamp repair assembly has the risk of causing stress concentration. Therefore, it is urgently needed to provide a method for high-precision laser selective melting to form thin-walled round-to-square structure ducts to solve the problems of difficult manufacturing and large welding deformation of traditional processes and improve the duct qualification rate. Summary of the invention

[0004] The purpose of the present invention is to propose a method for forming a thin-walled round-to-square structure catheter by high-precision laser selective melting, so as to solve the problem that the existing single-piece welding forming of special-shaped structure catheters is difficult, and the welding deformation of spatial special-shaped structures is large, resulting in difficulty in assembly, thereby improving the manufacturing qualification rate of special-shaped structure catheters and reducing manufacturing costs.

[0005] The present invention provides a method for forming a thin-walled round-to-square structure conduit by high-precision laser selective melting, the steps comprising: a. Establish a three-dimensional model of a thin-walled round-to-square structure catheter; b. Place the three-dimensional model of the catheter in the forming direction, with the round end of the catheter on top and the square end on the bottom, so that the acute angle between the inner surface and the horizontal direction at the position where the cavity inside the catheter cannot be repaired by clamps is greater than 45°; the lowest point is raised 1-3mm from the substrate plane; c. Add solid and grid supports on the lower surface of the outer surface of the circular ring of the conduit at the upper and lower ends where the angle between the horizontal direction is less than 45°; in addition, add solid and grid supports between the conduit and the substrate, and use oblique supports for the supports added at the upper and lower ends of the large circular ring of the conduit so that the supports fall on the forming substrate; the solid supports use cylinders with a diameter of 1-1.5mm and an interval of 5-8mm; d. Under the protection of inert gas, laser selective melting is performed according to the three-dimensional model obtained after adding support. The laser selective melting forming parameters are: contour scanning spot diameter 50-70μm, internal scanning spot diameter 80-100μm, laser power 270-310W, scanning speed 1000-1300mm / s, powder layer thickness 20-40μm, and spot compensation is set to 0.75 times the spot diameter; catheter e. Remove residual powder; f. heat treating the substrate and the catheter blank with support; g. Use wire cutting method to cut the substrate and the catheter, remove the solid support and grid support, grind and sandblast, and obtain the catheter blank for subsequent machining.

[0006] In the step c, the grid support adopts a diamond-shaped hollow support with a toothed structure, and the support parameters are as follows: XY axis offset 0.1mm-0.2mm; Z axis lower offset 0.02-0.03mm; filling line: X axis filling 0.5-0.7mm, Y axis filling 0.5-0.7mm, rotation angle 45°; filling teeth: upper tooth height 1mm-2mm, top length 0.2-0.3mm, base length 0.4-0.6mm, base interval 0.1-0.2mm, upper and lower teeth synchronization; cutting: X direction interval 2.5-3.5mm, Y direction interval 2.5-3.5mm, separation width 0.5-0.7mm; boundary teeth: upper tooth height 0.8-1.2mm, top length 0.2-0.4mm, base length 0.5-0.7mm, width 0.1-0.2mm, upper and lower teeth synchronization; hollowing method: diamond, beam width 0.3-0.4mm, angle 60°, height 1.5-2. mm, solid height 0.4-0.6mm.

[0007] Compared with the prior art, the present invention has the following advantages: The method of forming a thin-walled round-to-square structure catheter by high-precision laser selective melting described in the present invention realizes the integrated design and high-precision manufacturing of the thin-walled round-to-square structure catheter, eliminates the weld, avoids the stress concentration problem and weld tissue defects caused by welding, and makes the internal tissue of the catheter uniform, thereby improving the overall performance and manufacturing qualification rate of the catheter. It solves the problems of difficulty in manufacturing special-shaped structure catheters and large welding deformation, eliminates dimensional deviation, ensures assembly accuracy, and improves assembly efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the effect of spot compensation size; Figure 2 This is a schematic diagram of the thin-walled round-to-square catheter structure; Figure 3 This is a schematic diagram of the placement direction of the thin-walled round-to-square catheter; Figure 4 This is a schematic diagram of a thin-walled round-to-square conduit support; Figure 5 It is a schematic diagram of a disk-shaped spot compensation test piece; Figure 6 This is a schematic diagram of the typical metallographic structure of the TA15 alloy catheter in XY direction; Figure 7 This is a schematic diagram of the typical metallographic structure of the TA15 alloy catheter in the Z direction; Figure 1 In the figure, 1 is the contour after the spot is adjusted, 2 is the theoretical contour of the catheter, and 3 is the contour of the spot influence area. DETAILED DESCRIPTION

[0009] The present invention will be further explained below in conjunction with specific implementation plans, but the present invention is not limited thereto. The structures, proportions, and sizes illustrated in the drawings of the specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which the present invention can be implemented, so they have no substantive technical significance. Any structural modification, change in proportional relationship, or adjustment of size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0010] A method for forming a thin-walled round-to-square structure conduit by high-precision laser selective melting is specifically implemented according to the following steps: a. Use UG to establish a catheter thin-walled round-to-square catheter model, such as Figure 2 As shown, the catheter is a thin-walled round-to-square structure, the catheter is 150 mm high, the large circular ring at the lower end has a diameter of 65 mm, the small circular ring at the upper end has a diameter of 35 mm, and the wall thickness is 1.5 mm. The large circular ring and the small circular ring are respectively connected to the two ends of the spatial special-shaped structure.

[0011] b. The thin-walled round-to-square catheter model is placed on the substrate in the following direction: Figure 3 Considering that the conduit is an irregular spatial structure, in order to reduce the amount of support added, it is necessary to make the angle between the lower surface of the conduit and the horizontal direction greater than 45°, so the conduit is placed in a direction where the angle between the lower end ring of the conduit and the horizontal plane is 68°.

[0012] c. Add solid and mesh supports to the lower surface of the large circular ring at the lower end of the catheter where the angle with the horizontal direction is less than 45°. In order to prevent the support from being difficult to remove later and reduce the risk of catheter damage, the solid support and mesh support to be added to the large circular ring at the lower end of the catheter adopt oblique support with an angle of 60° to the horizontal plane, so that the support can be formed not directly on the catheter. Add solid and mesh supports between the catheter and the substrate, such as Figure 4 shown.

[0013] In order to ensure the smooth formation of the catheter, a solid support of 30 cylindrical groups with a diameter of 1 mm at a certain interval is used to ensure that the support has sufficient strength.

[0014] The grid support adopts a diamond hollow support with a tooth structure to reduce the contact area between the support and the catheter, which is convenient for the removal of the support later. The grid support parameters are as follows: XY axis offset 0.100mm; Z axis lower offset 0.0300mm; filling line: X axis filling 0.700mm, Y axis filling 0.700mm, rotation angle 45°; filling teeth: upper tooth height 1.000mm, top length 0.300mm, base length 0.600mm, base interval 0.100mm, upper and lower teeth synchronization; cutting: X interval 3.500mm, Y interval 3.500mm, separation width 0.700mm; boundary teeth: upper tooth height 1.000mm, top length 0.350mm, base length 0.600mm, base interval 0.100mm, upper and lower teeth synchronization; hollowing method: diamond, beam width 0.400mm, angle 60°, height 2.000mm, solid height 0.500mm.

[0015] d. Optimize the spot compensation parameters. The spot compensation size affects Figure 1 As shown in the figure, the laser selective melting forming spot compensation test piece is designed, and the structure is as follows Figure 5 As shown. The spot compensation test piece was subjected to laser selective melting again, with a spot diameter of 100μm, a laser power of 270-310W, a scanning speed of 1000-1300mm / s, a powder layer thickness of 20-40μm, and spot compensation values ​​of 25μm, 50μm, 75μm, and 100μm, respectively. By measuring the size of the formed test piece, the spot compensation value of 75μm was selected to meet the forming size accuracy.

[0016] The raw material is TA15 alloy powder. The powder particle size is 15μm-53μm, of which D10 is 16.90μm, D50 is 30.54μm, and D90 is 49.81μm; the hollow powder content of the powder is 0.47%.

[0017] The laser selective melting forming of the catheter blank was performed, and the laser selective melting forming parameters were set as follows: spot diameter 100μm, laser power 270-310W, scanning speed 1000-1300mm / s, powder layer thickness 20-40μm, and spot compensation 75μm. Under argon gas protection, laser selective melting forming was performed according to the three-dimensional model obtained after adding support to obtain a catheter blank with a substrate and support.

[0018] e. Post-process the powder on the surface of the catheter blank with support and inside the grid support, and use compressed air and a vibration platform to remove the residual powder on the surface and inside of the catheter and support.

[0019] f. Heat treat the substrate and the catheter blank with support. The annealing method of the vacuum heat treatment furnace is: the temperature is controlled at 800-850℃, kept at this temperature for 2-4 hours, and then cooled to room temperature with argon gas.

[0020] g. Use wire cutting method to cut the substrate and the catheter, remove the solid support and grid support, grind and sandblast, and obtain the catheter blank for subsequent machining.

[0021] The catheter blank was dissected and the metallographic structure of the catheter blank was observed. The XY metallographic structure is as follows: Figure 6 As shown, the Z-direction metallographic structure is as follows Figure 7 As shown, it can be seen that there are no unfused or crack defects.

[0022] Matters not covered by the present invention are known technologies.

[0023] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for forming a thin-walled round-to-square structure conduit by high-precision laser selective melting, characterized in that: include: a. Establish a three-dimensional model of a thin-walled round-to-square structure catheter; b. Place the three-dimensional model of the catheter in the forming direction, with the round end of the catheter on top and the square end on the bottom, so that the acute angle between the inner surface and the horizontal direction at the position where the cavity inside the catheter cannot be repaired by clamps is greater than 45°; the lowest point is raised 1-3mm from the substrate plane; c. Add solid and grid supports on the lower surface of the outer surface of the circular ring of the conduit at the upper and lower ends where the angle between the horizontal direction is less than 45°; in addition, add solid and grid supports between the conduit and the substrate, and use oblique supports for the supports added at the upper and lower ends of the large circular ring of the conduit so that the supports fall on the forming substrate; the solid supports use cylinders with a diameter of 1-1.5mm and an interval of 5-8mm; d. Under the protection of inert gas, laser selective melting is performed on the three-dimensional model obtained after adding support. The laser selective melting forming parameters are: contour scanning spot diameter 50-70μm, internal scanning spot diameter 80-100μm, laser power 270-310W, scanning speed 1000-1300mm / s, powder layer thickness 20-40μm, and spot compensation is set to 0.75 times the spot diameter; e. Remove residual powder; f. heat treating the substrate and the catheter blank with support; g. Use wire cutting method to cut the substrate and the catheter, remove the solid support and grid support, grind and sandblast, and obtain the catheter blank for subsequent machining.

2. The method for forming a thin-walled round-to-square structure conduit by high-precision laser selective melting according to claim 1 is characterized in that: In the step c, the grid support adopts a diamond hollow support with a toothed structure, and the support parameters are as follows: XY axis offset 0.1mm-0.2mm; The lower part of the Z axis is offset by 0.02-0.03mm; filling line: X axis filling 0.5-0.7mm, Y axis filling 0.5-0.7mm, rotation angle 45°; filling teeth: upper tooth height 1mm-2mm, top length 0.2-0.3mm, base length 0.4-0.6mm, base interval 0.1-0.2mm, upper and lower teeth are synchronized; Cutting: X-direction spacing 2.5-3.5mm, Y-direction spacing 2.5-3.5mm, separation width 0.5-0.7mm; boundary teeth: upper tooth height 0.8-1.2mm, top length 0.2-0.4mm, base length 0.5-0.7mm, width 0.1-0.2mm, upper and lower teeth synchronization; hollowing method: diamond, beam width 0.3-0.4mm, angle 60°, height 1.5-2. mm, solid height 0.4-0.6mm.

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