Large heat dissipation structure integrated manufacturing tool and method

Abstract

The application provides a large heat dissipation structure integrated manufacturing tool and method, and belongs to the field of laser processing manufacturing. According to the size of a laser selective melting forming device, under the premise of ensuring the integrity of a special structure of a part, a region with low laser welding difficulty is selected for cutting, and then segmented laser selective melting forming manufacturing is carried out, and then laser welding is carried out, so that the composite manufacturing of a large-size part is realized through multiple laser processes. In the laser selective melting forming process, the welding area is reserved with an excess amount and an arc starting and collecting plate is designed, the excess amount is removed after welding, and the consistency of the weld quality is ensured. In the welding process, the welding gun posture and welding parameters are optimized, the contamination of spatter on the gun head is improved, and the stability of the welding molten pool is improved. After the laser selective melting forming and the laser welding, heat treatment is carried out on the part, a special tool is used, welding thermal stress is eliminated, and the deformation of the part in the heat treatment process is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser processing manufacturing, and relates to a large heat dissipation structure integrated manufacturing tool and method, in particular to a heat dissipation, foreign matter prevention integrated structure design and a laser selective melting forming and laser welding composite manufacturing method. BACKGROUND

[0002] The laser selective melting forming technology is an advanced manufacturing process, and its basic principle is that a three-dimensional model of a part to be manufactured is designed through a CAD software, then the three-dimensional model data is converted into two-dimensional slice data, a laser scanning path is generated, metal powder is uniformly laid on a printing table, a laser beam is scanned according to the preset path, the metal powder is locally melted, and the part is formed by layer-by-layer accumulation after solidification. It is mainly used for processing and forming of high-precision, high-complexity and thin-walled metal parts. The laser selective melting forming part is completed in a processing chamber filled with high-purity argon protection gas, and the size of the part is limited by the size of the processing chamber.

[0003] As one of the parts on the airplane, the grid part is mainly filled with small grids with a slope on the curved metal plate, which has the function of heat dissipation. The curvature and the angle of the small grids cannot be realized by traditional mechanical processing, and are mainly manufactured by laser selective melting forming process. However, with the development of aviation parts towards structure lightweight and large-scale integration, the size of this kind of parts is also increasing. For large grid parts, the size of the laser selective melting forming equipment on the market is difficult to meet the forming processing of this kind of parts. In order to improve the processing efficiency, multiple laser beams are used for simultaneous processing and forming during the laser selective melting forming process of large parts, so there are a large number of overlapping areas in the forming process of the parts, and the overlapping area position is prone to overburning or incomplete fusion and other defects, which becomes the weak point of the part and seriously affects the overall quality of the part.

[0004] Laser welding is a high-efficiency and high-quality welding method, which has the advantages of shallow melting depth, small deformation and fast welding speed, and is mainly used for connecting high-precision thin-walled parts. The additive-laser welding composite manufacturing method can not only make up for the size limitation of laser selective melting forming, but also take advantage of the high-quality connection of laser welding, so as to realize the rapid forming of large grid parts. Since the laser selective melting forming is a "net forming" process, and the parts are mostly complex and multi-curvature parts, in order to control the overall deformation of the part, the additive-laser welding composite manufacturing method needs to involve additive part design, laser welding process exploration and connection tooling manufacturing and other problems. SUMMARY

[0005] In view of the problems of oversize of the additive parts and difficulty in laser welding deformation control, the application provides a large heat dissipation structure integrated manufacturing tool and method. Through integrated design of the large part, the large titanium alloy part is divided into several components, and is formed by segmental laser selective melting, and then is laser welded, so that the large size part is manufactured by multi-laser process composite manufacturing, the key complex features of the part are ensured, and the large part is integrated metallurgical combined. According to the size of the laser selective melting forming equipment, a specific segmentation principle is adopted, the area with low laser welding difficulty is selected for cutting under the premise of ensuring the integrity of the special structure of the part, the welding area is reserved in the laser selective melting forming process, and the start and stop arc plates are designed, the excess amount is removed after welding, and the welding quality consistency is ensured, the welding gun posture and welding parameters are optimized in the welding process, the contamination of spatter on the gun head is improved, and the welding pool stability is improved, and the part is heat treated after laser selective melting and laser welding, special tooling is adopted, welding thermal stress is eliminated, and the deformation of the part in the heat treatment process is reduced.

[0006] The technical means adopted by the application are as follows:

[0007] A large heat dissipation structure integrated manufacturing tool, the integrated manufacturing tool comprises a welding tool and a heat treatment tool.

[0008] The welding tool is a frame structure, the upper half is a front pressing structure, the lower half is a back pressing structure, the left and right sides of the front pressing structure and the back pressing structure are respectively provided with pressing beams, two normal fixing bolts are threadedly connected to each pressing beam, the upper and lower pressing beams on the same side form a group, the two pressing beams are opposite to each other, and the two groups of pressing beams are used for clamping two adjacent sub-pieces, one group of pressing beams is fixed, the other group of pressing beams can move up and down, is used for adjusting one of the sub-pieces, ensures that there is no step difference between the adjacent sub-pieces in height, and the welding tool applies a pressure parallel to the surface of the sub-pieces and perpendicular to the direction of the welding seam to the boss of the welding seam position, so that the butt joint between the sub-pieces has no gap.

[0009] The heat treatment tool is a clamping structure, comprising a heat treatment tool lower die 12 and a heat treatment tool upper die 13, the heat treatment tool lower die 12 is a concave die, the heat treatment tool upper die 13 is a convex die, the profiles of the two are set according to the profile of the part after welding and without cutting excess amount, and the heat treatment tool lower die 12 is provided with a positioning pin for part positioning.

[0010] The application also provides a large heat dissipation structure integrated manufacturing method, which adopts laser selective melting segmented forming, laser welding connection of phase composite process, reasonable design of segmented parts and welding area characteristics, laser selective melting forming advantage, multi-degree of freedom reserved welding process allowance, control of stress distribution in the part welding process, less part deformation; in the laser welding process, control the angle of the laser welding gun, optimize the additive part laser welding process parameters, improve the weld quality; use special heat treatment tooling to straighten the final formed parts, complete the integrated manufacturing of the parts. The manufacturing method comprises the following steps:

[0011] Step one, part segmentation. According to the segmentation design principle, the whole part is segmented into several subassemblies along the physical separation surface by using digital model processing software, and is marked respectively. According to the priority, the segmentation design has the following principles:

[0012] Priority one: the size of the subassembly is not greater than the maximum forming size of the laser selective melting forming equipment;

[0013] Priority two: the physical separation surface cannot be on the complex special structure;

[0014] Priority three: the maximum cross-sectional thickness of the region where the physical separation surface is located cannot exceed 3.5mm;

[0015] Priority four: for multi-curved surface structure, the bending angle of the physical separation surface is not greater than 45°.

[0016] Step two, welding area process allowance addition. Add a welding bevel, a boss and an arc ear piece at the welding position of the subassembly before additive digital model preprocessing, and ensure that the deformation of each subassembly in the laser selective melting forming process is within the controllable range through simulation. The boss at the welding bevel of the subassembly is set to have a height direction higher than the thickness of the part by 1.5mm and a single side width of 5mm; the main form of the welding bevel is a "Y" shaped welding bevel, the height of the complete butt joint part of the straight line should be higher than the upper surface of the part by 1mm, the lowest point of the "V" shaped part should be higher than the upper surface of the part by 1mm, and the angle should be not greater than 15°. The welding bevel design can effectively avoid the occurrence of edge biting and collapse on the net size part, reduce the risk of part out-of-tolerance due to welding defects, and realize high-quality connection of multiple laser selective melting forming subassemblies; the take-off arc end allowance is a process allowance of 5-10mm in extension on both sides of the part parallel to the welding direction, and the thickness is consistent with the welding bevel design thickness. The process allowance of the take-off arc end extension mainly serves as the arc striking plate and arc receiving plate in the laser welding process, and its main function is to form surface quality defects such as arc receiving pit in the allowance during the laser welding process, which can be removed through cutting and polishing later to ensure the consistency of the overall part. The take-off arc end allowance can adopt a non-solid support structure in the additive manufacturing support design to facilitate subsequent allowance removal.

[0017] Step three, using laser selective melting forming equipment, complete the forming of each sub-piece on the substrate.

[0018] Step four, the sub-piece is stress relief heat treatment.

[0019] Step five, using wire cutting process, each sub-piece is separated from the substrate.

[0020] Step six, each sub-piece is polished and the weld position is mechanically polished.

[0021] Step seven, each sub-piece is fixed on the welding tool, the welding gun posture is adjusted, and the welding between the sub-pieces is completed.

[0022] Step eight, the combined piece is installed on the heat treatment tool for stress relief annealing.

[0023] Step nine, the combined piece is subjected to X-ray detection to determine whether the weld and other parts have internal defects.

[0024] Step ten, remove the process boss, welding allowance and ear, and complete the overall machining of the part.

[0025] The beneficial effects of the present application are:

[0026] (1) using integrated design, segmented forming and laser connection process, large parts can be divided into several sub-pieces to complete the final forming, which not only reduces the size requirement of the laser selective melting forming equipment, but also improves the production efficiency of the parts;

[0027] (2) the principle of integrated structure segmented design can maximize the overall special complex shape of the part, and at the same time, the technical advantages of laser selective melting forming and laser welding are realized to achieve integrated manufacturing of large heat dissipation structure;

[0028] (3) the welding allowance is integrated into the laser selective forming process, which is an advantage that other welding processes do not have, not only reducing the risk of welding defects, but also ensuring that the weld area and other surface quality are consistent through post-processing.

[0029] (4) the design of adjustable welding tool can ensure the precise butt joint of the welding area of each sub-piece, which is beneficial to the high-quality connection of the weld.

[0030] (5) the design and use of the occlusion type heat treatment tool can control the deformation during heat treatment and correct the deformation during laser welding. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure is a schematic diagram of a large grid part in the embodiment.

[0032] Figure 2Schematic diagram of welding weld bevel.

[0033] Figure 3 Schematic diagram of laser selective melting support structure of sub-component.

[0034] Figure 4 Schematic diagram of welding tool

[0035] Figure 5 Schematic diagram of heat treatment tool, wherein (a) is a schematic diagram of a heat treatment tool lower die, and (b) is a schematic diagram of a heat treatment tool combination.

[0036] In the figure: 1 is a division surface A; 2 is a division surface B; 3 is a sub-component A; 4 is a sub-component B; 5 is a sub-component C; 6 is a top normal fixing bolt A; 7 is a bottom normal fixing bolt; 8 is a top normal fixing bolt B; 9 is a bottom normal adjusting bolt; 10 is a top normal adjusting bolt A; 11 is a top normal adjusting bolt B; 12 is a heat treatment tool lower die; 13 is a heat treatment tool upper die. DETAILED DESCRIPTION

[0037] The technical solutions of the present application will be described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all other embodiments improved or adjusted by those skilled in the art belong to the protection scope of the present application.

[0038] The present application will be further described taking a large TC4 titanium alloy grid part as an example, the structure of which is shown in Figure 1 The overall size of the part is 600mmx900mmx2mm.

[0039] The embodiment provides a large heat dissipation structure integrated manufacturing tool, which comprises a welding tool and a heat treatment tool.

[0040] As Figure 4As shown, the welding fixture is a frame structure, with the upper half being a front clamping structure and the lower half a back clamping structure. Both the front and back clamping structures have clamping beams on their left and right sides, and each clamping beam is threaded with two normal fixing bolts. The upper and lower clamping beams on the same side form a group, positioned opposite each other. The two groups of clamping beams are used to clamp two adjacent sub-components. One group of clamping beams is fixed in position. In this group, the upper clamping beam is threaded with a top normal fixing screw A. The top normal fixing screw B7 is connected to the bottom normal fixing bolt 7 threaded on the lower clamping beam. Another set of clamping beams can move up and down. In this set, the upper clamping beam is threaded with a top normal adjusting bolt A10 and a top normal adjusting bolt B11. This set of clamping beams is used to adjust one of the sub-components, ensuring no height difference between adjacent sub-components. Simultaneously, the welding fixture applies pressure parallel to the sub-component surface and perpendicular to the weld direction to the boss at the weld position, ensuring no gap between the sub-components. Because the sub-components have a certain curvature, the welding fixture design must ensure complete fit between the sub-components and the fixture in the non-weld area. In the weld area, the height of the two sub-components at the joint position can be adjusted using the upper and lower sets of bolts.

[0041] like Figure 5 As shown, the heat treatment fixture is a snap-fit ​​structure design, including a lower mold 12 and an upper mold 13. The lower mold 12 is a concave mold, and the upper mold 13 is a convex mold. Their surfaces are designed according to the shape of the part after welding and before any cutting allowance. The lower mold 12 is equipped with locating pins for part positioning. The part is first placed in the lower mold 12, and its position is fixed using the locating pins. Then, the upper mold 13 is pressed onto the part, clamping it between the upper and lower mold surfaces for overall stress-relieving annealing and shaping. This structure is used primarily because the part is a thin-walled structure with poor deformation resistance, especially after laser welding, when the thermal stress at the weld seam is high, making the assembly prone to deformation. Therefore, a dedicated heat treatment fixture is needed to correct the overall shape of the part during weld stress-relieving annealing, reducing the risk of deviations caused by heat treatment and welding deformation.

[0042] This embodiment also provides a method for integrated manufacturing of a large heat dissipation structure, based on the aforementioned integrated manufacturing tooling. The integrated manufacturing method includes the following steps:

[0043] Step one: Based on the principle of segmented design, use digital modeling software to divide the entire part into several sub-parts along the physical separation surface, and label each sub-part. Segmented design follows the following principles based on priority:

[0044] Priority 1: The size of the sub-parts should not exceed the maximum forming size of the laser selective melting forming equipment;

[0045] Priority two: the physical separation surface cannot be on a complex special structure;

[0046] Priority three: the maximum cross-sectional thickness of the region where the physical separation surface is located cannot exceed 3.5mm;

[0047] Priority four: for multi-curved surface structures, the bending angle of the physical separation surface is not greater than 45°.

[0048] According to the size of the part in this embodiment, the segmentation surface A 1 and the segmentation surface B 2 are determined by adopting the segmentation design principle, the part is divided into three segments along the two segmentation surfaces, and is marked as sub-piece A 3, sub-piece B 4 and sub-piece C 5, as shown in Figure 1 The size of each segment is 600mm×300mm×2mm.

[0049] Step two, adding the process allowance of the welding area. A welding boss and a “Y” shaped welding groove are added at the segmentation surface, the single-sided boss has a height of 1.5mm and a width of 5mm, and the welding groove has an angle of 15°, as shown in Figure 2 The arc starting plate and the arc receiving plate with a length of 8mm, a width of 10mm and a height of 5mm are added on both sides of the welding seam. In the process of laser selective melting forming of the sub-pieces, the part is mainly placed in a vertical posture, as shown in Figure 3 The support design adopts a dot matrix structure, and the dot matrix structure is used to connect the two sub-pieces. This method can effectively solve the deformation problem of single sub-piece forming, and the processed digital model is stored in stl format.

[0050] Step three, laser selective melting forming of the sub-pieces. The processed stl file is imported into a four-beam laser melting selective forming device, the forming power is set to 325W, the scanning speed is set to 1100mm / s, the layer thickness is set to 0.06mm, the track spacing is set to 0.11mm, the scanning mode is set to strip type, and the strip width is set to 10mm. After the completion of the settings, the laser selective melting forming device is started to form each sub-piece on the substrate.

[0051] Step four, heat treatment of the sub-pieces. After the laser selective melting forming of the part is completed, the part is taken out from the device, the powder is cleaned, and the dot matrix structure is ensured to have no powder residue. Then, the part with the substrate is subjected to stress relief annealing, the annealing temperature is 800±10℃, the holding time is 4h, the furnace is cooled to 200℃, and then air cooling is performed.

[0052] Step five, separation of the sub-pieces. The line cutting process is used to separate the sub-pieces from the substrate, and the dot matrix structure between the two sub-pieces is divided into two.

[0053] Step six, polishing before laser welding. The mechanical polishing is performed on each sub-piece, mainly to remove the residual support, dot matrix structure and welding seam butt joint area. The surface unmelted powder of the welding seam butt joint area is completely removed and the metal luster is exposed.

[0054] Step seven, laser welding of sub-components. The weld area is cleaned using acetone and wrapped with white cloth to ensure that the area is not contaminated before welding. The polished adjacent sub-components are installed on the welding fixture, one of which is clamped and fixed by the top normal fixing screw A6, the top normal fixing screw B8 and the bottom normal fixing bolt 7. The other one is clamped by the bottom normal adjusting bolt 9, the top normal adjusting bolt A10 and the top normal adjusting bolt B11. The height of the weld position of the sub-component is adjusted by rotating the three adjusting bolts to ensure that there is no step difference between the two sub-components. The laser welding gun is adjusted to form an angle of 3-5° with the normal of the weld plane. After teaching the welding trajectory, the laser welding process parameters are set, the welding power is 3200W, the defocusing amount is-2mm, and the welding speed is 0.025m / s. Step seven is repeated to weld all the sub-components into a combined component.

[0055] Step eight, heat treatment of the combined component. The combined component after welding is placed on the lower die 12 of the heat treatment tooling and fixed in position by the positioning pin. The upper die 13 of the heat treatment tooling is installed, and the combined component and the heat treatment tooling are placed in a vacuum furnace for stress relief annealing. The heat treatment temperature is 600°C, the holding time is 2 hours, and the furnace is cooled.

[0056] Step nine, non-destructive testing of the combined component. X-ray testing is performed on the combined component to ensure that there are no internal quality defects such as pores, cracks, incomplete fusion, and inclusions.

[0057] Step ten, removal of process allowance. The process allowance such as the boss, arc starting plate and arc collecting plate at the weld is removed by polishing for the combined component that has passed the detection, and the preparation of the large grid part is finally completed.

[0058] The above-described embodiments only express the implementation of the present application, but should not be interpreted as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application.

Claims

1. A large heat dissipation structure integrated manufacturing method, based on an integrated manufacturing tool, characterized in that, The integrated manufacturing tooling includes welding tooling and heat treatment tooling; The welding tooling is in the form of a frame structure, the upper half is a front pressing structure, the lower half is a back pressing structure, the front pressing structure and the back pressing structure are each provided with pressing beams on the left and right sides, and each pressing beam is threadedly connected with two normal fixing bolts, the upper and lower pressing beams on the same side are a group, the two pressing beams are opposite to each other in position, and the two groups of pressing beams are used for clamping two adjacent sub-pieces, one group of pressing beams is fixed in position, and the other group of pressing beams is movable up and down, used for adjusting one of the sub-pieces, ensuring that there is no step difference in height between the adjacent sub-pieces, and the welding tooling applies a pressure to the boss at the position of the weld, which is parallel to the surface of the sub-piece and perpendicular to the direction of the weld, to ensure that there is no gap between the butt joints of the sub-pieces; The heat treatment tooling is in the form of a clamping structure, and includes a heat treatment tooling lower die (12) and a heat treatment tooling upper die (13); the heat treatment tooling lower die (12) is a concave die, and the heat treatment tooling upper die (13) is a convex die, the profiles of the two are set according to the profile of the part after welding and without cutting allowance, and the heat treatment tooling lower die (12) is provided with a positioning pin for part positioning; The manufacturing method includes the following steps: Step one, part segmentation; according to the segmentation design principle, the entire part is segmented into a plurality of sub-pieces along the physical separation surface by using numerical model processing software; Step two, welding area process allowance addition; additive numerical model pre-processing is performed on the sub-pieces, a weld bevel, a boss and a start and recovery arc ear piece are added at the position of the weld, and simulation is performed to ensure that the deformation of each sub-piece in the laser selective melting forming process is within a controllable range; Step three, laser selective melting forming equipment is used to complete the forming of each sub-piece on the substrate; Step four, stress relief heat treatment is performed on the sub-pieces; Step five, linear cutting process is used to separate each sub-piece from the substrate; Step six, each sub-piece is polished and the support is removed, and the weld position is mechanically polished; Step seven, each sub-piece is fixed on the welding tooling, the welding gun posture is adjusted, and the welding between the sub-pieces is completed; Step eight, the combined part is installed on the heat treatment tooling for stress relief annealing; Step nine, X-ray detection is performed on the combined part to determine whether there are internal defects in the weld and other parts; Step ten, the process boss, welding allowance and ear piece are removed, and the overall machining of the part is completed. In step two, the height of the boss in the height direction is 1.5 mm higher than the thickness of the part, and the single-side width is 5 mm; The weld bevel is a "Y" shaped bevel, the height of the straight line complete butt joint part is 1 mm higher than the upper surface of the part, the lowest point of the "V" shaped part is 1 mm higher than the upper surface of the part, and the angle is not greater than 15°.

2. The method of claim 1, wherein In step one, the segmentation design has the following principles according to the priority: Priority one: the size of the sub-piece is not greater than the maximum forming size of the laser selective melting forming equipment; Priority two: the physical separation surface cannot be on a complex special structure; Priority three: the maximum cross-sectional thickness of the region where the physical separation surface is located cannot exceed 3.5 mm; Priority four: for a multi-curved surface structure, the bending angle of the physical separation surface is not greater than 45°.

3. The method of claim 1, wherein the large heat dissipation structure is integrated with the electronic device. The arc end allowance in the second step is a process allowance of 5-10 mm in extension on both sides of the part parallel to the direction of the weld, and the thickness is consistent with the design thickness of the weld bevel.

4. The method of claim 1, wherein The welding power in the seventh step is 3200 W, the defocusing amount is -2 mm, and the welding speed is 0.025 m / s.

5. The method of claim 1, wherein In the eighth step, the heat treatment temperature is 600 DEG C, and the holding time is 2 hours.

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