CN109396676B - Method for controlling surface groove defects of three-layer hollow sandwich structure - Google Patents
Method for controlling surface groove defects of three-layer hollow sandwich structure Download PDFInfo
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- CN109396676B CN109396676B CN201811516053.3A CN201811516053A CN109396676B CN 109396676 B CN109396676 B CN 109396676B CN 201811516053 A CN201811516053 A CN 201811516053A CN 109396676 B CN109396676 B CN 109396676B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K28/00—Welding or cutting not covered by any of the preceding groups, e.g. electrolytic welding
- B23K28/02—Combined welding or cutting procedures or apparatus
Abstract
The invention relates to a method for controlling the surface groove defect of a three-layer hollow sandwich structure in the technical field of welding. The method comprises the following steps: high-energy beam modification treatment is carried out on two sides of the diffusion connection part of the upper panel and the lower panel of the titanium alloy, a gradient structure with high-temperature deformation resistance is obtained, and local deformation of the periphery of the connection part is inhibited during superplastic forming; cleaning the surfaces of the upper panel, the lower panel and the core plate with the gradient tissues; preparing an upper sheath and a lower sheath which are matched with the upper panel and the lower panel in size, wherein the deformation resistance of the upper sheath and the lower sheath is higher than the plastic deformation resistance of the titanium alloy panel; coating a solder stop agent on the lower sheath, the lower panel, the core plate, the upper panel and the upper sheath, laminating from bottom to top, welding and sealing the periphery of the laminated structure, and reserving vent holes; and heating and pressurizing the sealing structure body subjected to sealing welding of the laminated layers to realize diffusion connection and superplastic forming, and then removing the upper sheath and the lower sheath.
Description
Technical Field
The invention relates to the technical field of welding, in particular to a method for controlling the surface groove defect of a three-layer hollow sandwich structure.
Background
The superplastic forming/diffusion bonding technology has the advantages of near net forming, good integrity, high rigidity, large design freedom degree and the like in manufacturing hollow structural members, and has wide application in the fields of aviation, aerospace and the like. According to the number of layers of the plate required by the structural manufacturing, the process structure can be divided into a single-layer structure, a two-layer structure, a three-layer structure, a four-layer structure and the like, wherein one of the forming difficulties of the three-layer structure is that the surface groove defect is difficult to control, and the groove defect is generally reduced by increasing the thickness of the skin, so that the structural weight is increased, and the use range and the structural design margin are limited. Besides the increase of the skin thickness to reduce the grooves, the number of the skin layers can be increased, and the grooves can be covered by the outer skin, however, the performance of the part formed by the method can hardly meet the design requirement.
For a three-layer structure (comprising a middle core plate and two side skin panels), a part without a groove defect on the surface can be obtained only by the engineering experience that the thickness of the skin is more than 3 times of that of the middle core plate, the thickness of the skin is increased along with the increase of the height of a cavity, and then the excessive thickness of the skin is removed through surface thinning treatment to reach the design requirement. The second scheme is that a layer of skin is added outside the skins on two sides respectively, and the grooves generated in the forming process of the middle three-layer structure are covered by the two outermost skins to obtain parts with smooth surfaces.
Therefore, the inventor provides a method for controlling the surface groove defect of the three-layer hollow sandwich structure.
Disclosure of Invention
The embodiment of the invention provides a method for controlling the surface groove defects of a three-layer hollow sandwich structure, which can avoid the surface groove defects of a titanium alloy three-layer structure by a process blank design method of combining a skin with a gradient structure and a hard sheath.
The embodiment of the invention provides a method for controlling the surface groove defect of a three-layer hollow sandwich structure, which comprises the following steps:
obtaining a gradient structure, and performing high-energy beam modification treatment on both sides of the diffusion connection part of the upper panel and the lower panel of the titanium alloy to obtain the gradient structure with high-temperature deformation resistance and inhibit local deformation of the periphery of the connection part during superplastic forming;
surface treatment is carried out on the face plate and the core plate, the surfaces of the upper face plate and the lower face plate with gradient structures are cleaned, and the core plate of the titanium alloy is cleaned, so that the upper face plate, the lower face plate and the core plate all reach the surface state required by diffusion connection;
preparing a sheath, and preparing an upper sheath and a lower sheath which are matched with the upper panel and the lower panel in size, wherein the deformation resistance of the upper sheath and the lower sheath is higher than the plastic deformation resistance of the titanium alloy panel;
laminating and sealing, namely laminating a lower sheath, a lower panel, a core plate, an upper panel and an upper sheath from bottom to top, coating a solder stopping agent on non-diffusion connecting parts between the lower panel and the core plate and between the upper panel and the core plate, coating the solder stopping agent on the inner sides of the upper sheath and the lower sheath, welding and sealing the periphery of the laminated structure, and reserving vent holes in layer gaps on two sides of the core plate during welding;
and performing diffusion bonding and superplastic forming, heating and pressurizing the sealing structure body after the laminated sealing welding, performing diffusion bonding on the upper panel and the lower panel and the core plate respectively, performing superplastic forming on the core plate, and then removing the upper sheath and the lower sheath.
Further, the method for obtaining the gradient structure comprises the step of performing high-energy beam modification treatment on two sides of the diffusion connection part of the upper panel and the lower panel by adopting a laser welding method with the power of 3kW-3.5kW and the welding speed of 2.5m/min-3.5m/min to obtain the gradient structure.
Further, the method for obtaining the gradient tissue comprises the step of modifying both sides of the diffusion connection part of the upper panel and the lower panel by high-energy beams by adopting an electron beam welding method to obtain the gradient tissue.
Further, before the method for obtaining the gradient structure, the surfaces of the upper panel and the lower panel of the titanium alloy are degreased and cleaned, so that the surfaces are smooth and clean and have no pollution.
Further, the diffusion bonding method comprises the steps of heating the sealing structure body after the lamination sealing welding to 800-820 ℃, and applying 1.2-2.0 MPa of air pressure to the upper wrapping sleeve and the lower wrapping sleeve to enable the upper panel and the lower panel and the core plate to be in diffusion bonding at the diffusion bonding position.
Further, the superplastic forming method comprises the steps of placing the sealing structure body after diffusion connection is achieved into a mold, heating to 775-810 ℃, introducing high-purity argon through air holes reserved in two sides of the core plate, keeping the temperature and pressure for 2-4 hours, carrying out superplastic forming on the middle core plate, and completely attaching a film to a skin to obtain the hollow sandwich structure.
Further, after the superplastic forming method, the upper sheath and the lower sheath are removed by a high-pressure water cutting method, and a completely formed three-layer hollow structural part is obtained.
In conclusion, the invention adopts a process blank design method of combining the skin with the gradient structure and the hard sheath to eliminate the surface grooves of the three-layer superplastic forming/diffusion connecting structural part. The method utilizes the principle that the deformation resistance of the hard sheath is higher than the superplastic deformation resistance of a three-layer structural member to inhibit the generation of grooves caused by over-fast local deformation in the forming process, and ensures that a certain friction force exists between the skin and the sheath to prevent local deformation near the diffusion connection area of the outer skin; the use of a skin with a gradient structure increases the deformation resistance of the diffusion junction area at high temperatures, thereby further suppressing local deformations due to the tensile stress of the core plate on the skin. The process blank design method of combining the skin with the hard sheath of the gradient structure can eliminate the surface grooves of the three-layer structure, and the hollow structural member with the surface quality meeting the design requirement is obtained. In addition, the design range of a three-layer structure is increased, the initial thickness ratio of the skin to the core board can reach 1:1, chemical milling procedures are reduced, and the material utilization rate is improved.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic position diagram of gradient tissue obtained by performing high-energy beam modification treatment on an upper skin and a lower skin according to an embodiment of the present invention.
Figure 2 is a schematic view of a laminate assembly.
FIG. 3 is a schematic representation of a three-layer hollow sandwich structure obtained using the method of an embodiment of the present invention.
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the invention and are not intended to limit the scope of the invention, i.e., the invention is not limited to the embodiments described, but covers equivalent modifications, substitutions and improvements without departing from the spirit of the invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The embodiment of the invention provides a method for controlling the surface groove defect of a three-layer hollow sandwich structure. The method takes SP700 titanium alloy face plates and core plates as an example for explanation, and at least comprises the following steps S110 to S120:
step S110 is to obtain a gradient structure, high-energy beam modification treatment is carried out on two sides of the diffusion connection part of the SP700 titanium alloy upper panel and the diffusion connection part of the SP700 titanium alloy lower panel, the gradient structure with high-temperature deformation resistance is obtained, and local deformation of the periphery of the connection part during superplastic forming is inhibited.
Before the method of the step, the method also comprises the steps of removing oil and cleaning the surfaces of the upper panel and the lower panel of the titanium alloy, so that the surfaces are smooth and clean and have no pollution.
In this step, as shown in fig. 1, the method for obtaining the gradient structure includes performing high-energy beam modification treatment on both sides of the diffusion bonding portion of the upper panel and the lower panel by using a laser welding method with a power of 3kW to 3.5kW and a welding speed of 2.5m/min to 3.5m/min for the SP700 titanium alloy to obtain the gradient structure. Or, high-energy beam modification treatment is carried out on both sides of the diffusion connection part of the upper panel and the lower panel by adopting an electron beam welding method to obtain the gradient tissue. The high-temperature deformation resistance of the modified gradient structure is obviously greater than that of the unmodified part, so that the local deformation of the corresponding modified part can be inhibited, and the groove of the connecting part is prevented from appearing during superplastic forming.
Step S120 is to perform surface treatment on the face plate and the core plate, to clean the surfaces of the upper face plate and the lower face plate having the gradient structure, and to clean the core plate of the titanium alloy, so that the upper face plate, the lower face plate, and the core plate all reach the surface state required for the diffusion bonding.
Step S130 is to prepare a sheath, and prepare an upper sheath and a lower sheath which are matched with the sizes of the upper panel and the lower panel, wherein the deformation resistance of the upper sheath and the lower sheath is higher than the plastic deformation resistance of the titanium alloy panel.
Step S140 is laminate sealing, as shown in fig. 2, laminating the lower sheathing, the lower panel, the core board, the upper panel, and the upper sheathing from bottom to top, coating solder stop agents on non-diffusion connection portions between the lower panel and the core board and between the upper panel and the core board, coating solder stop agents on inner sides of the upper sheathing and the lower sheathing, welding and sealing the periphery of the laminated structure, and reserving vent holes in layer gaps at two sides of the core board during welding.
And S150, performing diffusion connection and superplastic forming, heating and pressurizing the sealing structure body after the sealing welding of the laminated layers, performing diffusion connection between the upper panel and the lower panel and the core plate respectively, and removing the upper sheath and the lower sheath after superplastic forming of the core plate.
In the step, the diffusion bonding method comprises the steps of heating the sealing structure body after the lamination sealing welding to 800-820 ℃, and applying 1.2-2.0 MPa of air pressure to the upper sheath and the lower sheath to enable the upper panel and the lower panel and the core plate to realize diffusion bonding at the diffusion bonding position.
The superplastic forming method comprises the steps of putting the sealed structure body after diffusion connection is achieved into a mold, heating to 775-810 ℃, introducing high-purity argon through air holes reserved on two sides of a core plate, keeping the temperature and pressure for 2-4 hours, carrying out superplastic forming on the middle core plate, and completely attaching a film to a skin to obtain the hollow sandwich structure.
After the superplastic forming method, the method further comprises the step of removing the upper sheath and the lower sheath along the periphery of the lamination of the sheath and the skin panel by adopting a high-pressure water cutting method to obtain a formed complete three-layer hollow structural member, as shown in fig. 3.
It should be noted that the selection of the sheath material in the invention needs to have certain superplasticity (meeting the requirement of the upper and lower skins of the part on the superplastic deformation), and the superplastic deformation resistance is higher than that of the three-layer structural member material. The invention obtains a coarse as-cast structure with higher high-temperature deformation resistance by performing surface treatment on the two sides of diffusion connection of the upper skin and the lower skin, and can obtain a gradient structure meeting the requirement by adopting a local high-energy beam modification treatment method such as laser welding or electron beam welding. Preparing a welding stopping agent pattern on the front side and the back side of the middle core plate according to a reinforcing rib form required by design, coating the welding stopping agent on the inner side surface of the sheath at least to prevent the connection between the three-layer structure blank and the sheath, then assembling the middle core plate, the outer skin and the sheath, carrying out seal welding on the sheath and the blank, and fixing the sheath and the blank by spot welding after the three-layer structure blank is sealed and welded, carrying out leak detection on the three-layer structure blank, heating the blank to a diffusion connection temperature, and applying air pressure to the two sides to carry out diffusion connection to complete the diffusion connection of the outer skin and the core. And introducing high-purity argon with certain air pressure into the inner layer gradually to enable the diffusion blank to generate superplastic deformation gradually, and maintaining the pressure after the part is pasted with the film. And after heat preservation and pressure maintaining for a certain time, completing the complete forming of the part, cutting the periphery of the part by adopting a high-pressure water cutting method, and removing the sheath to obtain the three-layer hollow structural member without the groove defect on the surface.
The foregoing is illustrative of the present application and is not limited to the specific steps and structures described above and shown in the accompanying drawings. Also, a detailed description of known process techniques is omitted herein for the sake of brevity. Various modifications and alterations to this application will become apparent to those skilled in the art without departing from the scope of this invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (5)
1. A method for controlling the surface groove defect of a three-layer hollow sandwich structure, which is characterized by comprising the following steps:
obtaining a gradient structure, and performing high-energy beam modification treatment on both sides of the diffusion connection part of the upper panel and the lower panel of the titanium alloy to obtain the gradient structure with high-temperature deformation resistance and inhibit local deformation of the periphery of the connection part during superplastic forming;
surface treatment is carried out on the face plate and the core plate, the surfaces of the upper face plate and the lower face plate with gradient structures are cleaned, and the core plate of the titanium alloy is cleaned, so that the upper face plate, the lower face plate and the core plate all reach the surface state required by diffusion connection;
preparing a sheath, and preparing an upper sheath and a lower sheath which are matched with the upper panel and the lower panel in size, wherein the deformation resistance of the upper sheath and the lower sheath is higher than the plastic deformation resistance of the titanium alloy panel;
laminating and sealing, namely laminating a lower sheath, a lower panel, a core plate, an upper panel and an upper sheath from bottom to top, coating a solder stopping agent on non-diffusion connecting parts between the lower panel and the core plate and between the upper panel and the core plate, coating the solder stopping agent on the inner sides of the upper sheath and the lower sheath, welding and sealing the periphery of the laminated structure, and reserving vent holes in layer gaps on two sides of the core plate during welding;
performing diffusion connection and superplastic forming, heating and pressurizing the sealing structure body after the laminated sealing welding, performing diffusion connection between the upper panel and the lower panel and the core plate respectively, performing superplastic forming on the core plate, and then removing the upper sheath and the lower sheath;
the method for obtaining the gradient structure comprises the step of performing high-energy beam modification treatment on two sides of the diffusion connection part of the upper panel and the lower panel by adopting a laser welding method with the power of 3.5kW and the welding speed of 3.5m/min to obtain the gradient structure.
2. The method for controlling the surface groove defects of the three-layer hollow sandwich structure according to claim 1, wherein before the method for obtaining the gradient structure, the surfaces of the upper panel and the lower panel of the titanium alloy are degreased and cleaned, so that the surfaces are smooth and pollution-free.
3. The method for controlling the surface groove defects of the three-layer hollow sandwich structure according to claim 1, wherein the method for diffusion bonding comprises the steps of heating the sealing structure after the lamination sealing welding to 800-820 ℃, and applying 1.2-2.0 MPa of air pressure to the upper wrapping sleeve and the lower wrapping sleeve to enable the upper panel and the lower panel and the core plate to be in diffusion bonding at the diffusion bonding positions.
4. The method for controlling the surface groove defects of the three-layer hollow sandwich structure according to claim 1, wherein the superplastic forming method comprises the steps of placing the sealing structure body after diffusion connection is achieved into a mold, heating to 775-810 ℃, introducing high-purity argon through vent holes reserved on two sides of a core plate, preserving heat and pressure for 2-4 hours, superplastic forming the middle core plate, and completely attaching a film to a skin to obtain the hollow sandwich structure.
5. The method for controlling the surface groove defects of the three-layer hollow sandwich structure according to claim 1, wherein after the superplastic forming method, the upper sheath and the lower sheath are removed by a high-pressure water cutting method to obtain a formed complete three-layer hollow structural member.
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| CN109955042B (en) * | 2019-03-28 | 2020-12-11 | 中国航空制造技术研究院 | Preparation method of titanium alloy hollow structure |
| CN110328495B (en) * | 2019-06-06 | 2021-07-30 | 南阳师范学院 | Ti2Method for producing AlNb-based alloy honeycomb structure, and Ti2AlNb-based alloy honeycomb structure |
| CN110860860B (en) * | 2019-12-03 | 2021-06-08 | 中国航空制造技术研究院 | Preparation method of metal ordered porous structure |
| CN112792153A (en) * | 2020-12-18 | 2021-05-14 | 北京航星机器制造有限公司 | Diffusion, stretching, chemical milling and composite forming method for aluminum alloy multilayer plate |
| CN115302210B (en) * | 2022-10-12 | 2023-01-13 | 北京智创联合科技股份有限公司 | Control and compensation method for hot creep deformation of rocket titanium alloy nozzle |
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