Integrated manufacturing tool and method for large heat dissipation structure

Abstract

The invention provides an integrated manufacturing tool and method for a large heat dissipation structure, and belongs to the field of laser machining and manufacturing. According to the size of selective laser melting forming equipment, on the premise that the integrity of the special structure of the part is guaranteed, an area with the low laser welding difficulty is selected for cutting, segmented selective laser melting forming manufacturing is conducted, then laser welding is conducted, and multi-laser-process composite manufacturing of the large-size part is achieved. In the selective laser melting forming process, allowance reserving and arc starting and stopping plate design are conducted on a welding area, allowance is removed after welding, and the consistency of the welding seam quality is guaranteed; in the welding process, the welding gun posture and welding parameters are optimized, pollution of splashing to a gun head is improved, and the stability of a welding pool is improved; a part is subjected to heat treatment after selective laser melting forming and laser welding, a special tool is adopted, welding thermal stress is eliminated, and deformation of the part in the heat treatment process is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of laser processing and manufacturing, and relates to an integrated manufacturing tool and method for a large heat dissipation structure, and specifically to a composite manufacturing method of an integrated structural design for heat dissipation and prevention of foreign matter entry, laser selective melting forming, and laser welding. Background Art

[0002] Laser selective melting forming technology is an advanced manufacturing process. Its basic principle is to design the 3D model of the part to be manufactured through CAD software, then convert the 3D model data into 2D slice data, generate the laser scanning path, and then evenly spread the metal powder on the printing table. The laser beam scans along the preset path to locally melt the metal powder, and after solidification, it accumulates layer by layer to form the part. It is mainly used for the processing and forming of high-precision, highly complex thin-walled metal parts. The parts formed by laser selective melting are formed in a processing chamber filled with high-purity argon protective gas, and the size of the parts is limited by the size of the processing chamber.

[0003] As one of the parts on the aircraft, grille parts are mainly small grids with slopes on the curved metal plate, which have the function of heat dissipation. The curvature and the angle of the small grids cannot be achieved by traditional mechanical processing. They are mainly manufactured by laser selective melting forming process. However, as aviation parts gradually develop towards lightweight structure and large-scale integration, the size of such parts is also increasing. For large grille parts, the size of laser selective melting forming equipment on the market is difficult to meet the forming processing of such parts. In addition, in order to improve the processing efficiency during the laser selective melting forming process of large parts, multiple laser beams are often used for simultaneous processing and forming. Therefore, there are a large number of overlap areas in the parts during the forming process, and the overlap area is prone to defects such as overburning or unfused, which becomes the weak point of the parts and seriously affects the overall quality of the parts.

[0004] Laser welding is an efficient and high-quality welding method with the advantages of shallow melting depth, small deformation and fast welding speed. It is mostly used for the connection of high-precision thin-walled parts. The use of the additive-laser welding composite manufacturing method can not only make up for the shortcomings of the limited size of laser selective melting forming, but also give full play to the advantages of high-quality connection of laser welding, thereby realizing the rapid forming of large grid-type parts. Since laser selective melting forming is a "net forming" process and most parts are complex and multi-curvature parts, in order to control the overall deformation of the parts, the additive-laser welding composite manufacturing method needs to involve issues such as additive part design, laser welding process exploration and connection tooling production. Summary of the invention

[0005] In response to the above-mentioned problems of excessive size of additive parts and difficulty in controlling deformation during laser welding, the present invention provides a large-scale integrated manufacturing tooling and method for heat dissipation structures. Through the integrated design of large parts, large titanium alloy parts are divided into several components, and laser selective melting is performed in sections, and then laser welding is performed to achieve multi-laser process composite manufacturing of large-sized parts, which can not only ensure the key complex features of the parts, but also achieve integrated metallurgical bonding of large parts. According to the size of the laser selective melting forming equipment, a specific segmentation principle is adopted, and on the premise of ensuring the integrity of the special structure of the parts, areas with lower laser welding difficulty are selected for cutting; during the laser selective melting forming process, the welding area is reserved for margins and the arc starting and closing plates are designed, and the margins are removed after welding to ensure the consistency of weld quality; during the welding process, the welding gun posture and welding parameters are optimized to improve the contamination of the gun tip by spatter and improve the stability of the welding molten pool; after laser selective melting forming and laser welding, the parts are heat treated, and special tooling is used to eliminate welding thermal stress and reduce the deformation of parts during heat treatment.

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

[0007] A large-scale heat dissipation structure integrated manufacturing tooling, the integrated manufacturing tooling comprising a welding tooling and a heat treatment tooling.

[0008] The welding tooling is a frame-shaped structure as a whole, the upper half is a front clamping structure, and the lower half is a back clamping structure. The front clamping structure and the back clamping structure are respectively provided with clamping beams on the 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 are a group, and the two are positioned relative to each other. The two groups of clamping beams are respectively used to clamp two adjacent sub-components, one group of clamping beams is fixed in position, and the other group of clamping beams can be moved up and down to adjust one of the sub-components to ensure that there is no step difference in height between adjacent sub-components. At the same time, the welding tooling applies a pressure parallel to the sub-component surface and perpendicular to the weld direction to the boss at the weld position to ensure that there is no gap between the sub-components.

[0009] The heat treatment tooling is of an interlocking structure design, including 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 surfaces of the two are set according to the surface of the parts after welding and without cutting excess. The heat treatment tooling lower die 12 is provided with a positioning pin for part positioning.

[0010] The present invention also provides an integrated manufacturing method for a large heat dissipation structure, which adopts a composite process of laser selective melting segmented forming and laser welding connection, reasonably designs the characteristics of segmented parts and welding areas, gives full play to the advantages of laser selective melting forming, reserves welding process margins with multiple degrees of freedom, controls the stress distribution during the welding process of parts, and reduces the deformation of parts; during the laser welding process, controls the angle of the laser welding gun, optimizes the laser welding process parameters of the additive parts, and improves the quality of the weld; uses special heat treatment tooling to correct the final formed parts and complete the integrated manufacturing of parts. The manufacturing method comprises the following steps:

[0011] Step 1: Part segmentation. Based on the principle of segmentation design, the entire part is segmented into several sub-parts along the physical separation surface using digital model processing software, and each is labeled separately. According to the priority, segmentation design has the following principles:

[0012] Priority 1: The sub-component size is not larger than the maximum forming size of the laser selective melting forming equipment;

[0013] Priority 2: The physical separation surface cannot be on a complex or special structure;

[0014] Priority 3: The maximum cross-sectional thickness of the area where the physical separation surface is located cannot exceed 3.5 mm;

[0015] Priority 4: For multi-curved surface structures, the bending angle of the physical separation surface is no greater than 45°.

[0016] Step 2: Add process allowance in welding area. Perform additive digital model pre-processing on the sub-components, add weld grooves, bosses and arc start and end ears at the weld position, and ensure that the deformation of each sub-component during laser selective melting forming is within a controllable range through simulation. A boss with a height direction higher than the part thickness of 1.5mm and a single-side width of 5mm is set at the weld groove of the sub-component; the main form of the weld groove is a "Y"-shaped weld groove, the height of the straight line fully butted part should be 1mm higher than the upper surface of the part, the lowest point of the "V"-shaped part is 1mm higher than the upper surface of the part, and the angle is not greater than 15°. The weld groove design can effectively avoid the occurrence of undercuts and collapse on net-size parts, reduce the risk of part out-of-tolerance caused by welding defects, and achieve high-quality connection of multiple laser selective melting forming sub-components; the arc start and end allowance is a process allowance of 5-10mm on both sides of the part parallel to the weld direction, and the thickness is consistent with the design thickness of the weld groove. The process margin of the arc starting and closing ends is mainly used as the arc starting plate and arc closing plate for laser welding. Its main function is to form surface quality defects such as arc closing pits generated during laser welding on the margin, which are subsequently removed by cutting and grinding to ensure the consistency of the overall parts. The arc starting and closing end margins can adopt the non-solid support structure in the additive manufacturing support design to facilitate the subsequent margin removal.

[0017] Step three: Use laser selective melting forming equipment to complete the forming of each sub-component on the substrate.

[0018] Step 4: subjecting the sub-component to stress relief heat treatment.

[0019] Step five: separate each sub-component from the substrate using a wire cutting process.

[0020] Step six: Grind each sub-component to remove the support and mechanically polish the weld position.

[0021] Step seven, fix each sub-component on the welding tooling, adjust the welding gun posture, and complete the welding between the sub-components.

[0022] Step eight, installing the assembly onto a heat treatment fixture and performing stress relief annealing.

[0023] Step nine, perform X-ray inspection on the assembly to confirm that there are no internal defects in the welds and other parts.

[0024] Step 10: Remove the process boss, welding allowance and lugs to complete the overall processing of the part.

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

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

[0027] (2) The integrated structural segmentation design principle can maximize the overall special and complex shape of the parts, while giving full play to the technical advantages of laser selective melting and laser welding to achieve integrated manufacturing of large heat dissipation structures;

[0028] (3) Integrating the welding allowance into the laser selective forming process is an advantage that other welding processes do not have. It not only reduces the risk of welding defects, but also ensures that the weld area is consistent with other surface quality through post-processing.

[0029] (4) The design of the adjustable welding tooling can ensure the precise docking of the welding areas of each sub-component, which is conducive to high-quality weld connection.

[0030] (5) The design and use of interlocking heat treatment tooling can properly correct the deformation during laser welding while ensuring that the deformation during the heat treatment process is controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a typical large grille part in the embodiment.

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

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

[0034] Figure 4 Schematic diagram of welding tooling

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

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

[0037] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments improved or adjusted by ordinary technicians in this field based on the embodiments of the present invention belong to the protection scope of the present invention.

[0038] The present invention is further described by taking a large TC4 titanium alloy grille part as an example. Figure 1 As shown, the overall size of the part is 600mm×900mm×2mm.

[0039] This embodiment provides an integrated manufacturing tool for a large heat dissipation structure, wherein the integrated manufacturing tool includes a welding tool and a heat treatment tool.

[0040] like Figure 4As shown, the welding fixture is a frame-shaped structure as a whole, the upper half is a front clamping structure, and the lower half is a back clamping structure. The front clamping structure and the back clamping structure are respectively provided with clamping beams on the left and right sides, and each clamping beam is threadedly connected with two normal fixing bolts. The upper and lower clamping beams on the same side are a group, and the two are positioned oppositely. The two groups of clamping beams are respectively used to clamp two adjacent sub-components, and one group of clamping beams is fixed in position. In the group of clamping beams, the clamping beam located at the top is threadedly connected with a top normal fixing screw A and The top normal fixing screw B7 is threadedly connected to the bottom normal fixing bolt 7 on the clamping beam at the bottom. Another set of clamping beams can move up and down. In this set of clamping beams, the top normal adjustment bolt A10 and the top normal adjustment bolt B11 are threadedly connected to the clamping beam at the top. This set of clamping beams is used to adjust one of the sub-components to ensure that there is no step difference in height between adjacent sub-components. At the same time, the welding tooling applies a pressure parallel to the sub-component surface and perpendicular to the weld direction to the boss at the weld position to ensure that there is no gap between the sub-components. Since the sub-components have a certain curvature, when designing the welding tooling, the non-weld area must ensure that the sub-component and the tooling are completely fitted. In the weld area, the height of the docking position of the two sub-components can be adjusted by the upper and lower sets of bolts.

[0041] like Figure 5 As shown, the heat treatment tooling is a bite-type structure design, including 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 profiles of the parts after welding and without cutting margins. The heat treatment tooling lower die 12 is provided with a positioning pin for positioning the parts. First, the parts are placed in the heat treatment tooling lower die 12, and the position of the parts is fixed by the positioning pin structure. Then, the heat treatment tooling upper die 13 is pressed on the parts, and the parts are sandwiched in the middle by the upper and lower profiles, and the parts are subjected to overall stress relief annealing and correction. This type of structure is mainly used because the parts are thin-walled structures as a whole, and the deformation resistance is poor. Especially after laser welding, the thermal stress at the weld position is large, and the assembly is prone to deformation. Therefore, it is necessary to make a special heat treatment tooling to correct the overall shape of the parts during the stress relief annealing of the welds to reduce the risk of out-of-tolerance caused by heat treatment and welding deformation of the parts.

[0042] This embodiment also provides an integrated manufacturing method for a large heat dissipation structure, which is implemented based on the above-mentioned integrated manufacturing tooling. The integrated manufacturing method includes the following steps:

[0043] Step 1: Based on the principle of segmented design, use digital model processing software to divide the entire part into several sub-parts along the physical separation surface and mark them separately. According to the priority, segmented design has the following principles:

[0044] Priority 1: The sub-component size is not larger than the maximum forming size of the laser selective melting forming equipment;

[0045] Priority 2: The physical separation surface cannot be on a complex or special structure;

[0046] Priority 3: The maximum cross-sectional thickness of the area where the physical separation surface is located cannot exceed 3.5 mm;

[0047] Priority 4: For multi-curved surface structures, the bending angle of the physical separation surface is no greater than 45°.

[0048] According to the size of the part in this embodiment, the segmented design principle is adopted to determine the dividing plane A1 and the dividing plane B2, and the part is divided into three sections along the two dividing planes, which are marked as sub-part A3, sub-part B4 and sub-part C5 respectively. Figure 1 As shown, the size of each section is 600mm×300mm×2mm.

[0049] Step 2: Add process allowance in welding area. Add weld boss and "Y" shaped weld groove at the split surface. The height of the single-side boss is 1.5mm, the width is 5mm, and the weld groove angle is 15°. Figure 2 As shown. Extend the two sides of the weld and add arc starter and arc end plates with a length of 8mm, a width of 10mm, and a height of 5mm. During the laser selective melting forming process, the parts are mainly placed vertically, as shown in the figure. Figure 3 As shown, the support design adopts a lattice structure, and the two sub-components are connected by a lattice structure. This method can effectively solve the deformation problem of a single sub-component, and the processed digital model is stored in the stl format.

[0050] Step 3: Selective laser melting of sub-components. The processed stl file is imported into the four-beam laser melting selective forming equipment, and the forming power is set to 325W, the scanning speed is 1100mm / s, the layer thickness is 0.06mm, the track spacing is 0.11mm, the scanning mode is strip type, and the strip width is 10mm. After completing the settings, start the laser selective melting forming equipment to form each sub-component on the substrate.

[0051] Step 4: Heat treatment of sub-components. Take out the parts formed by laser selective melting from the equipment, clean the powder, ensure that there is no powder residue in the lattice structure, and then perform stress relief annealing on the parts with substrates at 800±10℃ for 4h. Cool the furnace to 200℃ and then air cool.

[0052] Step 5: Separation of sub-components: Using wire cutting technology, separate the sub-components from the substrate and divide the lattice structure between the two sub-components into two.

[0053] Step 6: Grinding before laser welding. Each sub-component is mechanically polished to remove the remaining support, lattice structure and weld joint area. The weld joint area needs to completely remove the unmelted powder on the surface and expose the metallic luster.

[0054] Step seven, laser welding of sub-components. Use acetone to clean the weld area and wrap it with white cloth to ensure that the area is not contaminated before welding. Install the polished adjacent sub-components on the welding fixture, first clamp one of the sub-components with the top normal fixing screw A6, the top normal fixing screw B8 and the bottom normal fixing bolt 7; then clamp the two sub-components with the bottom normal adjustment bolt 9, the top normal adjustment bolt A10 and the top normal adjustment bolt B11, and adjust the height of the weld position of the sub-component by rotating the three adjustment bolts to ensure that there is no step difference between the two sub-components. Adjust the posture of the laser welding gun so that it forms an angle of 3-5° with the normal of the weld plane. After teaching the welding trajectory, set the laser welding process parameters, the welding power is 3200W, the defocus is -2mm, and the welding speed is 0.025m / s; repeat step seven to weld all sub-components into an assembly.

[0055] Step 8: Heat treatment of the assembly. Place the welded assembly on the lower die 12 of the heat treatment tooling, fix the position with the positioning pins, install the upper die 13 of the heat treatment tooling, put the assembly and the heat treatment tooling into 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 9: Nondestructive testing of the assembly. Perform X-ray testing on the assembly to ensure that there are no internal quality defects such as pores, cracks, lack of fusion, inclusions, etc.

[0057] Step 10: Removal of process allowances: For qualified assemblies, grinding is used to remove process allowances such as bosses, arc starting plates, and arc closing plates at the welds, and finally the preparation of the large grid parts is completed.

[0058] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A large-scale heat dissipation structure integrated manufacturing tool, characterized in that: The integrated manufacturing tooling includes welding tooling and heat treatment tooling; The welding tooling is a frame-shaped structure as a whole, the upper half is a front clamping structure, and the lower half is a back clamping structure. The front clamping structure and the back clamping structure are respectively provided with clamping beams on the left and right sides, and each clamping beam is threadedly connected with two normal fixing bolts. The upper and lower clamping beams on the same side form a group, and the two are positioned oppositely. The two groups of clamping beams are respectively used to clamp two adjacent sub-components, one group of clamping beams is fixed in position, and the other group of clamping beams can be moved up and down to adjust one of the sub-components to ensure that there is no step difference in height between adjacent sub-components. At the same time, the welding tooling applies a pressure parallel to the sub-component surface and perpendicular to the weld direction to the boss at the weld position to ensure that there is no gap between the sub-components. The heat treatment tooling is of interlocking structural design, comprising 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, and the profiles of the two are set according to the profiles of parts after welding and without cutting margins, and a positioning pin is set on the heat treatment tooling lower die (12) for positioning the parts.

2. A large-scale heat dissipation structure integrated manufacturing method, based on the integrated manufacturing tooling of claim 1, characterized in that: The manufacturing method comprises the following steps: Step 1: Part segmentation: Based on the principle of segmented design, digital model processing software is used to segment the entire part into several sub-parts along the physical separation surface; Step 2: Add process allowance in welding area; perform additive digital model pre-processing on sub-components, add weld grooves, bosses and arc start and end ears at the weld position, and ensure that the deformation of each sub-component during laser selective melting forming is within a controllable range through simulation; Step 3, using laser selective melting forming equipment to complete the forming of each sub-component on the substrate; Step 4, subjecting the sub-component to stress relief heat treatment; Step 5: Using wire cutting process to separate each sub-component from the substrate; Step 6: Grind each sub-component to remove the support and mechanically polish the weld position; Step 7: Fix each sub-component on the welding tool, adjust the welding gun posture, and complete the welding between the sub-components; Step eight, installing the assembly onto a heat treatment tooling and performing stress relief annealing; Step nine, perform X-ray inspection on the assembly to confirm that there are no internal defects in the welds and other parts; Step 10: Remove the process boss, welding allowance and lugs to complete the overall processing of the part.

3. A large-scale heat dissipation structure integrated manufacturing method according to claim 2, characterized in that: In step 1, the segmentation design has the following principles according to the priority: Priority 1: The sub-component size is not larger than the maximum forming size of the laser selective melting forming equipment; Priority 2: The physical separation surface cannot be on a complex or special structure; Priority 3: The maximum cross-sectional thickness of the area where the physical separation surface is located cannot exceed 3.5 mm; Priority 4: For multi-curved surface structures, the bending angle of the physical separation surface is no greater than 45°.

4. A large-scale heat dissipation structure integrated manufacturing method according to claim 2, characterized in that: In the step 2, the height of the boss is 1.5 mm higher than the thickness of the part, and the width of one side is 5 mm.

5. The method for manufacturing a large-scale heat dissipation structure in an integrated manner according to claim 2, characterized in that: In the step 2, the weld groove is a "Y"-shaped groove, the height of the straight line fully butted portion is 1 mm higher than the upper surface of the part, the lowest point of the "V"-shaped portion is 1 mm higher than the upper surface of the part, and the angle is not greater than 15°.

6. A large-scale heat dissipation structure integrated manufacturing method according to claim 2, characterized in that: In the step 2, the arc starting and ending margins are process margins extending 5-10 mm on both sides of the part parallel to the weld direction, and the thickness is consistent with the designed thickness of the weld groove.

7. A large-scale heat dissipation structure integrated manufacturing method according to claim 2, characterized in that: In the step 7, the welding power is 3200 W, the defocusing amount is -2 mm, and the welding speed is 0.025 m / s.

8. The method for manufacturing a large-scale heat dissipation structure in an integrated manner according to claim 2, characterized in that: In the step eight, the heat treatment temperature is 600° C. and the insulation time is 2 hours.

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