CN114871700B - Aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming method and mold - Google Patents
Aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming method and mold Download PDFInfo
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- CN114871700B CN114871700B CN202210590851.0A CN202210590851A CN114871700B CN 114871700 B CN114871700 B CN 114871700B CN 202210590851 A CN202210590851 A CN 202210590851A CN 114871700 B CN114871700 B CN 114871700B
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- 229910001148 Al-Li alloy Inorganic materials 0.000 title claims abstract description 133
- 239000001989 lithium alloy Substances 0.000 title claims abstract description 133
- JFBZPFYRPYOZCQ-UHFFFAOYSA-N [Li].[Al] Chemical compound [Li].[Al] JFBZPFYRPYOZCQ-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 119
- 230000003014 reinforcing effect Effects 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 48
- 238000003466 welding Methods 0.000 claims abstract description 60
- 238000003756 stirring Methods 0.000 claims abstract description 42
- 230000008569 process Effects 0.000 claims description 20
- 239000007789 gas Substances 0.000 claims description 15
- 238000005452 bending Methods 0.000 claims description 11
- 238000004140 cleaning Methods 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 238000005520 cutting process Methods 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 14
- 238000012545 processing Methods 0.000 abstract description 12
- 238000012797 qualification Methods 0.000 abstract description 4
- 229910052751 metal Inorganic materials 0.000 abstract description 2
- 239000002184 metal Substances 0.000 abstract description 2
- 238000009792 diffusion process Methods 0.000 description 7
- 230000007547 defect Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000003754 machining Methods 0.000 description 5
- 239000003351 stiffener Substances 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000004927 fusion Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 235000015842 Hesperis Nutrition 0.000 description 1
- 235000012633 Iberis amara Nutrition 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000010407 anodic oxide Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 238000004260 weight control Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
- B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/10—Die sets; Pillar guides
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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
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
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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
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/22—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded
- B23K20/233—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer
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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
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/22—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded
- B23K20/233—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer
- B23K20/2336—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer both layers being aluminium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Shaping Metal By Deep-Drawing, Or The Like (AREA)
Abstract
The invention relates to a forming method and a die for an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, belongs to the technical field of metal plastic processing, and solves the problems that the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin manufactured in the prior art is heavy in weight, difficult to guarantee in quality and high in cost. The aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming method adopts friction stir welding to connect an aluminum alloy plate and an aluminum lithium alloy plate together to form a friction stir welding seam and leave a superplastic forming air inlet, superplastic forming is carried out on the aluminum alloy plate and the aluminum lithium alloy plate to finally prepare the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, the manufactured aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is lighter than the traditional aluminum alloy reinforcing rib structure, and the aluminum lithium alloy performance price ratio is high only at the reinforcing rib position, so that the cost control is facilitated, the material performance loss is low, the reliability is higher, the primary qualification rate is higher, the structural integrity is good, and the profile precision is high.
Description
Technical Field
The invention belongs to the technical field of metal plastic processing, and relates to a forming method and a die for an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, which are suitable for manufacturing the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin.
Background
The aluminum alloy has low density, high specific strength and specific rigidity, high plasticity, low cost and rich resources. The aluminum alloy is formed by adding lithium element, the density of the aluminum lithium alloy is lower than that of the aluminum alloy, and each 1% of lithium is added, the density is reduced by 3%, the elastic modulus is improved by 6%, the aluminum lithium alloy has high specific modulus and high specific strength, the aluminum lithium alloy replaces the conventional high-strength aluminum alloy, the structural mass is reduced by 10% -20%, the rigidity is improved by 15% -20%, the aluminum lithium alloy also has excellent corrosion resistance, good heat conduction and electrical conductivity, and good comprehensive performances such as casting, hot working, welding, processing forming and the like. Space vehicles such as rockets have very high weight control requirements, and the launch cost is saved by about $2 ten thousand per 1kg of vehicle reduction. Therefore, the aluminum-lithium alloy is widely applied in the aerospace field, has wide application prospect in rail traffic, automobile electronics, nuclear industry and the like, and the hollow reinforcing rib skin is a typical part.
The aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is difficult to manufacture by adopting a diffusion connection/superplastic forming process, because a layer of compact and stable oxide film is easy to form on the surfaces of the aluminum alloy and the aluminum lithium alloy at room temperature, and the oxide film is not decomposed or dissolved in a matrix in the diffusion connection process, so that mutual diffusion of aluminum atoms is seriously hindered, if the method is adopted, the process flow is very complex and the process must be carried out under a vacuum condition. The fusion welding/superplastic forming process is easy to bring more welding defects, and the quality of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is difficult to ensure. At present, thick plate machining is mostly adopted to prepare aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, but the hollow reinforcing rib skin prepared by the process is heavy in weight and high in cost when being used for space vehicles and the like.
Disclosure of Invention
Based on the analysis, the invention aims to provide a forming method and a die for an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, so as to solve the problems that the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin manufactured by the prior art is heavy in weight, difficult to guarantee in quality and high in cost.
The aim of the invention is mainly realized by the following technical scheme:
in one aspect, the invention provides a method for forming an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, which comprises the following steps:
step 1: stacking the aluminum alloy plate and the aluminum lithium alloy plate together, and connecting the aluminum alloy plate and the aluminum lithium alloy plate together by adopting friction stir welding to form a friction stir welding seam and leave a superplastic forming air inlet;
step 2: and performing superplastic forming on the aluminum alloy plate and the aluminum lithium alloy plate.
Further, in the step 1, the rotation speed of the stirring head of the friction stir welding is 400-1200 r/min, and the welding speed is 60-180 mm/min.
Further, in the step 1, the width of the superplastic forming air inlet is 2 mm-6 mm.
Further, superplastic forming is carried out on the aluminum alloy plate and the aluminum lithium alloy plate, and the method comprises the following steps:
step 21: heating the upper superplastic forming die and the lower superplastic forming die to a preset temperature;
step 22: placing an aluminum alloy plate and an aluminum lithium alloy plate between an upper superplastic forming die and a lower superplastic forming die, wherein the upper superplastic forming die and the lower superplastic forming die are close to each other, bending the aluminum alloy plate and the aluminum lithium alloy plate, and applying certain pressure to clamp;
step 23: introducing gas into the aluminum alloy plate and the aluminum lithium alloy plate through the superplastic forming air inlet, so that the hollow reinforcing ribs locally bulge on the aluminum lithium alloy plate and are tightly attached to the cavity of the superplastic forming lower die;
step 24: and taking out the aluminum alloy plate and the aluminum lithium alloy plate from the space between the upper superplastic forming die and the lower superplastic forming die, cutting off the process allowance and cleaning the surface to obtain the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin.
Further, in the step 21, the preset temperature is 300 ℃ to 550 ℃.
Further, in the step 22, the approaching speed of the upper superplastic forming die and the lower superplastic forming die is 1mm/s to 10mm/s.
Further, in the step 22, the pressure applied to bend-form the aluminum alloy sheet and the aluminum lithium alloy sheet is 10t to 100t.
Further, in the step 23, the gas is introduced into the aluminum alloy plate and the aluminum-lithium alloy plate through the superplastic forming gas inlet as nitrogen or argon.
Further, in the step 23, the pressure of the gas introduced into the aluminum alloy plate and the aluminum-lithium alloy plate through the superplastic forming gas inlet is 0.1MPa to 4MPa.
Further, in the step 24, the allowance of the cutting process is air-cooled milling.
Further, in the step 24, the surface is cleaned by laser cleaning.
The invention also provides an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming die which is used for realizing the forming method and comprises a superplastic forming upper die and a superplastic forming lower die. The upper superplastic forming die is concave, the lower superplastic forming die is convex, and the angles of the concave upper superplastic forming die and the convex lower superplastic forming die are the same. The top fillet R1 and the bottom fillet R2 of the lower die cavity have the relation that R1 is more than or equal to 2 xT, R2 is more than or equal to 3 xT, wherein T is the thickness of the aluminum lithium alloy plate. The groove width B and the groove depth H of the cavity of the lower die are equal to or larger than 2 XH. The lengths of the upper superplastic forming die and the lower superplastic forming die are larger than or equal to the lengths of the aluminum alloy/aluminum lithium alloy plates.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) The aluminum-lithium alloy has higher specific strength and specific rigidity, but has high cost to completely replace the traditional aluminum alloy, and the invention only adopts the aluminum-lithium alloy with high cost performance at the reinforcing rib position, thereby being beneficial to cost control.
(2) The aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin manufactured by adopting friction stir welding/superplastic forming can be lighter than the traditional aluminum alloy reinforcing rib structure, and can be lightened by more than 10%.
(3) Compared with 40% of material performance loss caused by fusion welding and diffusion welding, the aluminum-lithium alloy/aluminum alloy dissimilar material is connected by adopting friction stir welding, and the aluminum-lithium alloy/aluminum-lithium alloy hollow reinforcing rib skin material manufactured by adopting the friction stir welding has the advantages of less performance loss and higher reliability.
(4) Compared with the method, the invention does not need to be carried out under vacuum condition, does not need to splice and weld a plurality of parts, and has simple process, short process flow and simple and easy implementation.
(5) The invention can manufacture complex curved surface hollow reinforcing rib skin structures with non-circular arcs, planes and irregular curved surfaces, the minimum circular angle at the bottom is generally more than 3 times of the thickness of the plate, the one-time qualification rate is higher, the structural integrity is good, and the profile precision is high.
Drawings
FIG. 1 is a schematic diagram of an aluminum alloy/aluminum lithium alloy hollow stiffener skin forming die;
FIG. 2 is a schematic illustration of friction stir welding of an aluminum alloy/aluminum lithium alloy hollow stiffener skin blank;
FIG. 3 is a schematic diagram of bending and forming an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin blank;
FIG. 4 is a schematic diagram of superplastic forming of an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin;
FIG. 5 is an aluminum alloy/aluminum lithium alloy complex curved hollow stiffener skin structure;
FIG. 6 is a flow chart of the aluminum alloy/aluminum lithium alloy hollow stiffener skin formation.
Reference numerals: the aluminum alloy plate comprises a 1-aluminum alloy plate, a 2-aluminum lithium alloy plate, a 3-friction stir welding seam, a 4-superplastic forming air inlet, a 5-superplastic forming upper die, a 6-superplastic forming lower die, a 7-lower die cavity, a R1-lower die cavity top round corner, a R2-lower die cavity bottom round corner, a T-aluminum lithium alloy plate thickness, a B-lower die cavity groove width and an H-lower die cavity groove depth.
Detailed Description
The following detailed description of preferred embodiments of the invention is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the invention, are used to explain the principles of the invention and are not intended to limit the scope of the invention.
In the prior art, the aluminum-lithium alloy has the comprehensive properties of high specific modulus, high specific strength, excellent corrosion resistance, good heat conduction and electrical conductivity, good casting, hot working, welding, processing forming and the like, is widely applied in the aerospace field, has wide application prospect in rail transit, automobile electronics, nuclear industry and the like, and the hollow reinforcing rib skin is a typical part thereof. The aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is difficult to manufacture by adopting a diffusion connection/superplastic forming process, because the surfaces of the aluminum alloy and the aluminum lithium alloy are extremely easy to form a layer of compact and stable oxide film at room temperature, and the oxide film is not decomposed or dissolved in a matrix in the diffusion connection process, so that mutual diffusion of aluminum atoms is seriously hindered. The fusion welding/superplastic forming process is easy to bring more welding defects, and the quality of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is difficult to ensure. At present, thick plate machining is mostly adopted to prepare aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, but the hollow reinforcing rib skin prepared by the process is heavy in weight and high in cost when being used for space vehicles and the like.
The invention provides a forming method of an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, which comprises the steps of connecting an aluminum alloy plate and an aluminum lithium alloy plate together by adopting friction stir welding to form a friction stir welding seam, leaving a superplastic forming air inlet, and carrying out superplastic forming on the aluminum alloy plate and the aluminum lithium alloy plate to finally obtain the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin.
Specifically, the invention provides a method for forming an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, which comprises the following steps:
step 1: stacking the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 together, and connecting the aluminum alloy plate and the aluminum lithium alloy plate together by adopting friction stir welding to form a friction stir welding seam 3 and leave a superplastic forming air inlet 4;
step 2: and performing superplastic forming on the aluminum alloy plate and the aluminum lithium alloy plate.
Compared with the prior art, the aluminum alloy plate and the aluminum lithium alloy plate are connected together by adopting friction stir welding, then the aluminum alloy plate and the aluminum lithium alloy plate are subjected to superplastic forming, welding defects such as air holes and the like are basically avoided during friction stir welding, the metallurgical performance of a base metal can be kept, the performance loss is small, the pollution to the environment before and during welding is small, strict surface cleaning preparation is not required for a workpiece before welding, the cost is low, and the efficiency is high. Compared with the traditional aluminum alloy reinforcing rib structure, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin manufactured by the invention has lighter weight, and the aluminum lithium alloy has high cost performance only at the reinforcing rib position, thereby being beneficial to cost control, small material performance loss, higher reliability, higher primary qualification rate, good structural integrity and high profile precision.
Specifically, in the step 1, the aluminum alloy/aluminum lithium alloy has the advantages of low density, high strength ratio, high rigidity ratio and the like, but has a low melting point, a high heat conductivity coefficient, a high specific heat capacity and a high linear expansion coefficient, and when welding is performed by adopting a fusion welding mode and the like, welding defects such as cracks, air holes, deformation and the like are easy to generate, and the alloy performance is reduced due to a low welding temperature. During friction stir welding, welding defects such as air holes and the like are basically avoided, the metallurgical performance of a base metal can be kept, the performance loss is small, the pollution to the environment is small before and during welding, strict surface cleaning preparation is not needed for workpieces before welding, the cost is low, and the efficiency is high.
The superplastic forming air inlet 4 is equivalent to a notch of a closed curve formed by the friction stir welding seam, and the size range of the superplastic forming air inlet 4 is 4-8 mm, for example, 4mm, 5mm, 6mm and 7mm, so that the air inlet smoothness can be ensured, and the integrity of the closed curve formed by the friction stir welding seam can be ensured as much as possible.
The friction stir welding seams 3 are arranged along the edges of the hollow reinforcing ribs, the number of the friction stir welding seams 3 is the same as that of the hollow reinforcing ribs, a plurality of friction stir welding seams are arranged on a plurality of hollow reinforcing ribs, the distance between adjacent friction stir welding seams depends on the positions of the hollow reinforcing ribs, and therefore the forming of the hollow reinforcing ribs can be guaranteed, and the minimum number and length of the friction stir welding seams can be guaranteed.
The rotation speed of the stirring head of the friction stir welding is 400 r/min-1200 r/min, and is exemplified by 500r/min,600r/min,700r/min,800r/min,900r/min,1000r/min and 1100r/min; the welding speed is 60mm/min to 180mm/min, and is exemplified by 80mm/min,100mm/min,120mm/min,140mm/min,150mm/min,160mm/min,170mm/min.
Specifically, in the step 2, the superplastic forming process includes:
step 21: heating the upper superplastic forming die 5 and the lower superplastic forming die 6 to a preset temperature;
step 22: placing the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 between an upper superplastic forming die 5 and a lower superplastic forming die 6, wherein the upper superplastic forming die 5 and the lower superplastic forming die 6 are close to each other, bending the aluminum alloy plate 1 and the aluminum lithium alloy plate 2, and applying certain pressure to clamp;
step 23: introducing gas into the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 through the superplastic forming air inlet 4, so that the aluminum lithium alloy plate 2 locally bulges the hollow reinforcing ribs to be tightly attached to the superplastic forming lower die cavity 7;
step 24: and taking out the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 from the space between the upper superplastic forming die 5 and the lower superplastic forming die 6, cutting off the process allowance and cleaning the surface to obtain the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin.
Specifically, in the step 21, the preset temperature is determined by the forming characteristics of the aluminum alloy/aluminum lithium alloy sheet material, and the temperature corresponding to the high material elongation is selected as much as possible within the temperature range required for material forming. The preset temperature is 300-550 ℃, such as 320 ℃, 350 ℃, 380 ℃, 400 ℃, 450 ℃, 480 ℃ for example.
Specifically, in the step 22, a liquid pressing machine is used to apply a pressure of 10 t-100 t to the upper plane of the upper superplastic forming die, so that the upper superplastic forming die and the lower superplastic forming die approach each other at a speed of 1 mm/s-10 mm/s, for example, 2mm/s, 3mm/s, 4mm/s, 5mm/s, 6mm/s, 7mm/s, 8mm/s, and 9mm/s, so that the aluminum alloy plate and the aluminum lithium alloy plate are subjected to a bending moment under the action of the pressure through the mutual cooperation of the concave shape of the upper superplastic forming die 5 and the convex shape of the lower superplastic forming die 6, and the bending forming is completed and the upper superplastic forming die and the lower superplastic forming die are closely attached. The approaching speed of the upper superplastic forming die and the lower superplastic forming die influences the bending forming quality of the material, the bending speed is too high, the bending part is flattened easily in the bending process of the material, the roundness cannot meet the requirement, the material cannot be completely attached to the superplastic forming die, and the material is easily pulled apart and broken. Too slow a speed can easily cause wrinkling of the material and slippage of the pinched portion.
Specifically, in the step 23, the gas is generally selected from nitrogen or argon, and the pressure of the introduced gas is 0.1MPa to 4MPa, for example, 0.5MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa; the hollow reinforcing ribs are locally bulged on the aluminum lithium alloy plate to be tightly attached to the cavity grooves of the superplastic forming lower die, and the size of the manufactured part is ensured to be qualified. The greater the pressure, the better the die bonding effect and the higher the dimensional accuracy of the part.
Specifically, in the step 24, the allowance of the cutting process is machined by air-cooled milling, so as to avoid that various errors, surface defects and clamping errors remained in the machining process affect the machining precision and the machining surface quality of the part. The oxide, the anodic oxide layer and other pollutants on the surface of the aluminum alloy/aluminum lithium alloy are rapidly removed through laser cleaning, the substrate is not damaged, the cleaning quality is accurate and controllable, and the environmental pollution is small.
The invention also provides an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming die which is used for realizing the forming method and comprises a superplastic forming upper die and a superplastic forming lower die.
The structure of the upper superplastic forming die 5 and the lower superplastic forming die 6 is shown in figure 1. The lower die cavity 7 is reserved on the upper die 6, the upper die 5 is concave, the lower die 6 is convex, the concave angle of the upper die 5 is the same as that of the lower die 6, and the shapes are matched. The top fillet R1 and the bottom fillet R2 of the lower die cavity 7 have the relation that R1 is more than or equal to 2 xT, and R2 is more than or equal to 3 xT, wherein T is the thickness of the aluminum lithium alloy plate. The groove width B and the groove depth H of the lower die cavity 7 have the relation B being more than or equal to 2 XH. The length of the upper superplastic forming die 5 and the lower superplastic forming die 6 is more than or equal to the length of the aluminum alloy plate 1/aluminum lithium alloy plate 2. Satisfying such a relationship ensures that the part is successfully formed during the forming process without cracking during the process.
Compared with the traditional aluminum alloy reinforcing rib structure, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin manufactured by the invention has lighter weight, and the aluminum lithium alloy has high cost performance only at the reinforcing rib position, thereby being beneficial to cost control, small material performance loss, higher reliability, higher primary qualification rate, good structural integrity and high profile precision.
Example 1
The aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin forming method of the embodiment comprises the following process steps:
step 1: stacking the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 together, and connecting the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 together by adopting friction stir welding to form a friction stir welding seam 3 and leave a superplastic forming air inlet 4; the rotation speed of a stirring head of friction stir welding is 400r/min, and the welding speed is 180mm/min; the width of the superplastic forming air inlet 4 is 4mm, and the number of the friction stir welding seams 3 is the same as that of the hollow reinforcing ribs, as shown in fig. 2.
Step 2: and performing superplastic forming on the aluminum alloy plate and the aluminum lithium alloy plate.
Step 21: the upper and lower superplastic forming molds 5 and 6 are heated to a preset temperature of 450 ℃.
Step 22: placing the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 between an upper superplastic forming die 5 and a lower superplastic forming die 6, wherein the upper superplastic forming die 5 and the lower superplastic forming die 6 are close to each other, bending the aluminum alloy plate 1 and the aluminum lithium alloy plate 2, and applying certain pressure to clamp; the approaching speed of the upper superplastic forming die 5 and the lower superplastic forming die 6 is 2mm/s, and the pressure clamping is 20t, as shown in FIG. 2.
Step 23: introducing gas into the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 through the superplastic forming air inlet 4, so that the aluminum lithium alloy plate 2 locally bulges the hollow reinforcing ribs to be tightly attached to the lower die cavity 7; argon gas is introduced into the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 through the superplastic forming air inlet 4, and the pressure is 1MPa, as shown in FIG. 3.
Step 24: and taking out the aluminum alloy plate 1 and the aluminum lithium alloy plate 2 from the space between the upper superplastic forming die 5 and the lower superplastic forming die 6, cutting off the process allowance and cleaning the surface to obtain the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin. The cutting process allowance mode is air-cooled milling processing, and the surface cleaning mode is laser cleaning.
The mold used in the above-mentioned molding method comprises: upper superplastic forming die 5 and lower superplastic forming die 6.
The lower die cavity 7 is reserved on the upper die 6, the upper die 5 is concave, the lower die 6 is convex, and the angles of the concave of the upper die 5 and the convex of the lower die 6 are the same. The top fillet R1 and the bottom fillet R2 of the lower die cavity 7 have the relation that R1 is more than or equal to 2 xT, and R2 is more than or equal to 3 xT, wherein T is the thickness of the aluminum lithium alloy plate 2. The groove width B and the groove depth H of the lower die cavity 7 have the relation B being more than or equal to 2 XH. The length of the upper superplastic forming die 5 and the lower superplastic forming die 6 is more than or equal to the length of the aluminum alloy plate 1/aluminum lithium alloy plate 2. The aluminum alloy plate 1 and the aluminum lithium alloy plate 2 are clamped between the upper superplastic forming die 5 and the lower superplastic forming die 6 by pressing with a hydraulic press. The thickness of the aluminum-lithium alloy plate 2 is 1.8mm, the top round angle R1 of the superplastic forming lower die cavity 7 is 4mm, and the bottom round angle R2 is 6mm, so that the relation R1 is more than or equal to 2 xT, and R2 is more than or equal to 3 xT. The groove width B of the superplastic forming lower die cavity 7 is 30mm, the groove depth H is 10mm, and the relation B is more than or equal to 2 XH.
Compared with the part prepared by the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin molded surface prepared by the method has the precision of +/-0.3 mm, the surface roughness Ra3.2, the structural weight is reduced by more than 10 percent, and the processing period is shortened by 30 percent. Specific performance metrics for example 1 are detailed in the following table.
Example 2
In this example, in step 1, the stirring head rotation speed of friction stir welding was 800r/min, the welding speed was 120mm/min, and other processing conditions were the same as in example 1.
Compared with the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin prepared by the embodiment can further improve the strength of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin friction stir welding joint, and the greater the friction stir welding strength is, the lighter the weight of the prepared part structure is, and the embodiment can reduce the structure weight by more than 15 percent and is of great importance to aerospace products.
Example 3
In this embodiment, in step 21, the preset temperature is selected to be 500 ℃, and other processing conditions are the same as those in embodiment 1.
Compared with the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin prepared by the embodiment can further improve the superplastic forming wall thickness uniformity of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, and the more uniform the wall thickness is, the lighter the weight of the prepared part structure is, and the embodiment can reduce the structure weight by more than 10 percent and is of great importance to aerospace products.
Example 4
In this example, in step 23, argon gas was introduced into the aluminum alloy sheet 1 and the aluminum lithium alloy sheet 2 through the superplastic forming gas inlet 4 at a pressure of 2MPa under the same processing conditions as in example 1.
Compared with the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin prepared by the embodiment can further improve the profile precision of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, which can reach +/-0.2 mm, and is of great importance to aerospace products.
Example 5
In this example, in step 22, the aluminum alloy sheet 1 and the aluminum lithium alloy sheet 2 were bent and formed under the same working conditions as in example 1, except that the pressure applied was 50 t.
Compared with the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin prepared by the embodiment can further improve the profile precision of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin to +/-0.28 mm.
Example 6
In this example, the approach speed of the upper and lower superplastic forming dies 5 and 6 was 5mm/s in step 22, and the other processing conditions were the same as in example 1.
Compared with the prior art, the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin prepared by the embodiment can further improve the processing efficiency of the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin, and compared with the embodiment 1, the processing period is shortened by 35%.
Comparative example 1
The aluminum-lithium alloy sheet 2 of example 1 was replaced with an aluminum alloy sheet, and the other conditions were the same as in example 1.
The aluminum alloy hollow stiffener skin prepared by the comparative example is 3% overweight by weight compared with example 1.
Comparative example 2
The forming die is selected, the thickness of the aluminum-lithium alloy plate 2 is 1.8mm, the top round angle R1 of the superplastic forming lower die cavity 7 is 3mm, the bottom round angle R2 is 5mm, and the relation R1 is more than or equal to 2 xT, and R2 is more than or equal to 3 xT. The groove width B of the superplastic forming lower die cavity 7 is 20mm, the groove depth H is 12mm, and the relation B is not less than 2 XH.
The aluminum alloy hollow reinforcing rib skin prepared by the comparative example has wall thickness uniformity of +/-12% compared with the example 1.
Comparative and example aluminium alloy/aluminium lithium alloy hollow reinforcing rib skin performance list
While the invention has been described in terms of the preferred embodiment, it is not intended to limit the invention, but it will be apparent to those skilled in the art that variations and modifications can be made without departing from the spirit and scope of the invention, and therefore the scope of the invention is defined in the appended claims.
Claims (8)
1. A method for forming an aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin is characterized by comprising the following steps of: the forming method comprises the following steps:
step 1: stacking the aluminum alloy plate and the aluminum lithium alloy plate together, and connecting the aluminum alloy plate and the aluminum lithium alloy plate together by adopting friction stir welding to form a friction stir welding seam and leave a superplastic forming air inlet; a friction stir welding seam is arranged along the edge of the hollow reinforcing rib; the superplastic forming air inlet is equivalent to a notch of a closed curve formed by friction stir welding, and the width of the superplastic forming air inlet is 4-8 mm; step 2: performing superplastic forming on the aluminum alloy plate and the aluminum lithium alloy plate;
the rotation speed of the stirring head of the friction stir welding is 400-1200 r/min, and the welding speed is 60-180 mm/min;
the forming method is realized by a forming die, and the forming die comprises: superplastic forming upper die and superplastic forming lower die;
a lower die cavity is reserved on the superplastic forming lower die, the superplastic forming upper die is concave, the superplastic forming lower die is convex, and the concave outline of the superplastic forming upper die is matched with the convex outline of the superplastic forming lower die;
the top fillet R1 and the bottom fillet R2 of the lower die cavity have the relation that R1 is more than or equal to 2 xT, R2 is more than or equal to 3 xT, wherein T is the thickness of the aluminum lithium alloy plate;
the groove width B and the groove depth H of the lower die cavity have the relation B being more than or equal to 2 XH;
the length of the upper superplastic forming die and the lower superplastic forming die is greater than or equal to the length of the aluminum alloy/aluminum lithium alloy plate.
2. The forming method according to claim 1, characterized in that: the step 2 comprises the following steps:
step 21: heating the upper superplastic forming die and the lower superplastic forming die to a preset temperature;
step 22: placing an aluminum alloy plate and an aluminum lithium alloy plate between an upper superplastic forming die and a lower superplastic forming die, wherein the upper superplastic forming die and the lower superplastic forming die are close to each other, bending the aluminum alloy plate and the aluminum lithium alloy plate, and applying certain pressure to clamp;
step 23: introducing gas into the aluminum alloy plate and the aluminum lithium alloy plate through the superplastic forming air inlet, so that the hollow reinforcing ribs locally bulge on the aluminum lithium alloy plate and are tightly attached to the cavity of the superplastic forming lower die;
step 24: and taking out the aluminum alloy plate and the aluminum lithium alloy plate from the space between the upper superplastic forming die and the lower superplastic forming die, cutting off the process allowance and cleaning the surface to obtain the aluminum alloy/aluminum lithium alloy hollow reinforcing rib skin.
3. The forming method according to claim 2, characterized in that: in the step 21, the preset temperature is 300-550 ℃.
4. The forming method according to claim 2, characterized in that: in the step 22, the approaching speed of the upper superplastic forming die and the lower superplastic forming die is 1 mm/s-10 mm/s.
5. The forming method according to claim 2, characterized in that: in the step 22, the pressure clamping is 10 t-100 t.
6. The forming method according to claim 2, characterized in that: in the step 23, the gas is nitrogen or argon.
7. The forming method according to claim 2, characterized in that: in the step 23, the pressure of the gas is 0.1MPa to 4MPa.
8. An aluminum alloy/aluminum lithium alloy hollow rib skin forming die for realizing the forming method of any one of claims 1 to 7, characterized in that the forming die comprises: superplastic forming upper die and superplastic forming lower die;
a lower die cavity is reserved on the superplastic forming lower die, the superplastic forming upper die is concave, the superplastic forming lower die is convex, and the concave outline of the superplastic forming upper die is matched with the convex outline of the superplastic forming lower die;
the top fillet R1 and the bottom fillet R2 of the lower die cavity have the relation that R1 is more than or equal to 2 xT, R2 is more than or equal to 3 xT, wherein T is the thickness of the aluminum lithium alloy plate;
the groove width B and the groove depth H of the lower die cavity have the relation B being more than or equal to 2 XH;
the length of the upper superplastic forming die and the lower superplastic forming die is greater than or equal to the length of the aluminum alloy/aluminum lithium alloy plate.
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