CN114985590A - Composite forming tool and forming method for large-curvature titanium alloy skin part - Google Patents

Abstract

The invention belongs to the field of metal large-size plate shaping and forming, and particularly relates to a composite forming tool and a forming method for a large-curvature titanium alloy skin part, which comprises a drawing die and a hot forming die; the drawing die comprises a tire body, a cast-in lifting hook and a positioning reference platform; the hot forming die comprises a hanging rod, an upper die, a lower die, a guide plate, a guide pillar, a positioning pin, a screw, a material taking groove and a pressure plate groove; the method can meet the high-quality processing requirement of the shape surface of the titanium alloy skin with large curvature, and the processing of the titanium alloy skin is realized through the mutual matching of the two tools and the redesigned process flow.

Description

Composite forming tool and forming method for large-curvature titanium alloy skin part

Technical Field

The invention belongs to the field of metal large-size plate shaping and forming, and particularly relates to a composite forming tool and a forming method for a large-curvature titanium alloy skin part.

Background

In the field of aeronautical manufacturing in China, titanium alloy skin parts are one of main part types on airplanes, have good fatigue strength and crack expansion resistance, strong corrosion resistance and good thermal stability, and are mainly used for parts with the use temperature below 400 ℃. The method is widely applied to key parts such as a fuselage, a tail section, wings, a pressure cabin, an engine cabin and the like. The TC1 titanium alloy skin part is an external skin of a tail cover of a rear fuselage of an airplane, and the TC1Ti-Al 2% -Mn1.5% titanium alloy belongs to Ti-Al-Mn titanium alloy and is medium-strength and high-plasticity alloy. The TC1 titanium alloy skin part is directly formed in one step by adopting an isothermal thermoforming method in the traditional mode, and due to the fact that the part curvature is large, the specific strength, the specific fracture toughness and the ultimate strength in material properties are high, the part is large in deformation resilience after one-step thermoforming, the tire sticking degree is poor, manual repairing is needed after general thermoforming, a large amount of time is needed for shape correction, and the production efficiency is low.

Disclosure of Invention

The invention aims to provide a tool structure for stretch forming and isothermal forming of a titanium alloy large-curvature skin part and a composite forming method thereof.

The technical scheme of the invention is as follows:

the composite forming tool for the large-curvature titanium alloy skin part comprises a drawing die and a hot forming die;

the drawing die comprises a tire body 1, a cast-in type lifting hook 2 and a positioning reference platform 3; the hot forming die comprises a hanging rod 4, an upper die 5, a lower die 6, a guide plate 7, a guide pillar 8, a positioning pin 9, a screw 10, a material taking groove 11 and a pressure plate groove 12;

the molded surface of the tire body 1 is consistent with the theoretical molded surface of a part; cast-in type lifting hooks 2 are arranged on two sides of the tire body 1 in the non-stretching direction and used for preventing the lifting rigging from unhooking; a positioning reference platform 3 is arranged at the top of the tire body 1 and is used for positioning basis for reference establishment and subsequent tool repair during numerical control machining of the tire body 1;

the non-contact surfaces of the upper die 5 and the lower die 6 and the part are of a grid type hollow structure; the molded surface is consistent with the theoretical surface of the part; when the lower die 6 is placed in a thermoforming machine, the lower die is connected with the thermoforming machine through a pressure plate groove 12; during processing, the part is placed on the lower die 6 along with the shape surface and is fixed by a positioning pin 9 arranged on the shape surface of the lower die 6; the two sides of the lower die 6 are provided with hanging rods 4 in the non-stretching direction for preventing the hanging rigging from unhooking; vertical grooves are formed in the stretching directions of the two sides of the lower die 6 and used for accommodating the guide plates 7; a guide post 8 arranged on the edge of the upper end of the lower die 6 is matched with a guide hole at the lower end of the upper die 5 during die assembly, a guide plate 7 is arranged on the edge of the butt joint between the upper die 5 and the lower die 6 after die assembly, the upper end of the upper die 5 and the upper end of the guide plate 7 are fixedly connected through a screw 10, and the lower end of the guide plate 7 is embedded into a vertical groove of the lower die 6; the side edge of the lower die 6 is provided with a material taking groove 11, and the material taking groove 11 is a concave platform processed along with the shape surface and used for taking out parts after the parts are subjected to thermal forming.

Further, the carcass 1 is made of resin material or metal material; the position of the positioning reference platform 3 forms 90 degrees with the stretching direction, the size is not less than 100X100mm, and a reference hole is drilled in the middle; the upper die 5 and the lower die 6 are made of medium silicon molybdenum nodular cast iron.

The composite forming tool of the large-curvature titanium alloy skin part carries out the skin forming method, which comprises the following steps:

the first step is as follows: pasting an aluminum strip on the titanium alloy part, and pasting a 45mm technical aluminum strip on the surface of the part contacted with the two ends of the jaw through an adhesive film before stretching; firstly, cleaning two ends of an aluminum plate by using acetone within a range of 50 millimeters, removing burrs of a technical aluminum strip, and cleaning a gluing surface by using acetone; the treated parts and the process aluminum strips are not allowed to be touched by naked hands, and are wrapped by plastic cloth or wrapping paper to be assembled; preheating an aluminum strip, pasting an adhesive film, assembling an aluminum sheet pasted with the adhesive film on an aluminum plate, and heating and fixing by using a blower; paving a ventilating felt on the part, covering a vacuum bag, packaging the periphery of the part by using a sealing rubber strip and then feeding the part into an autoclave; curing according to autoclave curing process; finally, cleaning work is carried out, the vacuum bag and the air felt are removed, and the residual glue is cleaned; if no problem exists, the next step is carried out;

the second step is that: placing a tool, namely sleeving a sling in the cast-in type lifting hooks 2 at two ends of the tire body 1 to ensure the lifting safety, firstly placing a drawing die at the central position of a drawing machine by using a crane, and secondly placing a drawing tool at the central position of a platform by using the crane; the tool and the platform are well fixed, then the position is well arranged according to the stretching direction and the direction of the jaw is consistent with the jaw direction, the die is cleaned, and the surface of the die is coated with oil;

the third step: cold process stretch forming, checking whether the thickness of the material and the surface state of the material are not allowed to have cracks, delaminations, non-metallic inclusions, bubbles, burning loss, corrosion spots and burrs on the edge of the material are removed or not; placing two ends of a part blank in a jaw of a stretcher, enabling an end head to be in contact with the bottom end of the jaw, ensuring that the jaw is closed by a clamping amount, controlling the stretching tonnage in the process of clamping the blank part to be stretched, ensuring that the stretching rate is not more than 6% according to elongation test paper, knocking the surface of the part by using a rubber beating plate, checking whether the part is adhered to a tire, processing qualified parts for the first time, and storing and recording a pressurizing track for subsequent part forming; opening the jaw, taking the part out of the jaw, paying attention to protect the surface of the part, preventing scratching, checking whether the surface of the part has serious slip lines or not, checking whether the surface of the part has serious bulges or pits or not due to coarse grains, checking whether the surface of the part has serious scratches, checking whether the part is attached to a tool or not and checking whether the part has obvious gaps or not, and performing a hot forming process after the part is checked to be qualified;

the fourth step: carrying out titanium alloy thermoforming, namely cleaning the molded surface of a thermoforming mold on the surface of the blank by using acetone; then, coating a lubricant, uniformly coating graphite on the surface of the blank and the working surface of the hot forming die, and increasing the coating amount of the reference die profile at the part with large curvature change and local stretching forming; then, mounting the hot forming die in the center of a platform of the hot forming machine by using a crane and a forklift; carrying out pressure test according to the complexity of the molded surface, firstly fixing an upper die 5, utilizing an equal-thickness aluminum material to carry out die assembly pressure test to adjust a die gap, and fixing a lower die 6 after the die assembly pressure test is finished; after fixation, the temperature is raised according to the requirement of the thermal forming temperature, and the temperature raising rate is less than or equal to 75 ℃/h; after the temperature of the preheating equipment is stable, placing the wool into an equipment platform or a mould, preheating the wool according to the requirement of preheating time for forming, positioning the wool according to a molded surface, placing the wool into a lower mould 6, closing the mould according to the requirement of forming pressure, arranging a guide plate 7 at the edge of the butt joint between an upper mould 5 and the lower mould 6 after closing the mould, fixedly connecting the upper mould 5 and the upper end of the guide plate 7 through a screw 10, embedding the lower end of the guide plate 7 into a vertical groove of the lower mould 6, maintaining the pressure according to the requirement of pressure maintaining time, and finally taking out the part;

the fifth step: inspecting the part, and inspecting the tyre fitting degree of the part according to an inspection die, wherein the fitting clearance with the tool is not more than 0.5 mm;

and a sixth step: and after the part is detected to be qualified, the screw 10 is pulled out, the part is taken down, and the subsequent paint spraying process is carried out.

The invention has the beneficial effects that:

the invention can realize the high-quality processing requirement of the shape surface of the titanium alloy skin with large curvature, and the processing of the titanium alloy skin is realized through the mutual matching of the two tools and the redesigned process flow.

Drawings

FIG. 1 is a drawing die block diagram;

FIG. 2 is a schematic view of a hot forming mold structure;

FIG. 3 is a lower die structure view of a thermoforming mold;

in the figure: 1. a carcass; 2. casting-in type lifting hooks; 3. positioning a reference platform; 4. a hanging rod; 5. an upper die; 6. a lower die; 7. a guide plate; 8. a guide post; 9. positioning pins; 10. a screw; 11. a material taking groove; 12. pressing plate groove

Detailed Description

A composite forming tool for a large-curvature titanium alloy skin part; the method comprises the steps that a tool required by cold process drawing forming is called a drawing die, and a tool required by titanium alloy skin hot forming is called a hot forming die;

the drawing die comprises a tire body 1, a cast-in type lifting hook 2 and a positioning reference platform 3; the hot forming die comprises a hanging rod 4, an upper die 5, a lower die 6, a guide plate 7, a guide pillar 8, a positioning pin 9, a screw 10, a material taking groove 11 and a pressure plate groove 12;

the molded surface of the tire body 1 is consistent with the theoretical molded surface of a part, and a five-axis numerical control machine tool is adopted for processing; cast-in type lifting hooks 2 are arranged on two sides of the tire body 1 in the non-stretching direction and used for preventing the lifting rigging from unhooking; a positioning reference platform 3 is arranged at the top of the tire body 1 and is used as a positioning basis for reference establishment and subsequent tool repair in the numerical control machining of the tire body 1;

the non-contact surfaces of the upper die 5 and the lower die 6 and the part are of a grid type hollow structure; keeping the molded surface consistent with the theoretical molded surface of the part, and processing the part through a hot forming machine; the lower dies 6 are connected with each other through the platen grooves 12 when being put into the thermoforming machine; during processing, the part is placed on the lower die 6 along with the shape surface and is fixed by a positioning pin 9 arranged on the shape surface of the lower die 6; the two sides of the lower die 6 are provided with hanging rods 4 in the non-stretching direction for preventing unhooking to a hanging rigging; vertical grooves are formed in the stretching directions of the two sides of the lower die 6 and used for accommodating the guide plates 7; a guide post 8 arranged on the edge of the upper end of the lower die 6 is matched with a guide hole at the lower end of the upper die 5 during die assembly, a guide plate 7 is arranged on the edge of the butt joint between the upper die 5 and the lower die 6 after die assembly, the upper ends of the upper die 5 and the guide plate 7 are fastened and connected through a screw 10, and the lower end of the guide plate 7 is embedded into a vertical groove of the lower die 6; the edge of the side face of the lower die 6 is provided with a material taking groove 11, and the material taking groove 11 is a concave platform processed along with the shape surface and used for taking out parts after the parts are subjected to thermal forming.

Further, the carcass 1 is made of resin material or metal material; if resin material is adopted, the height of the tire body 1 is controlled between 300 and 400 mm; if a metal material is adopted, the height of the matrix 1 is controlled to be between 200 and 300 mm; the cast-in type lifting hook 2 is a cylindrical rod with the diameter of phi 30-phi 50mm, and the diameter of the end of the rod body is 10-20mm larger than the diameter of the middle part; the position of the positioning reference platform 3 forms 90 degrees with the stretching direction, the size is not less than 100X100mm, and a reference hole with the diameter of phi 8mm or phi 10mm is drilled in the middle; the upper die 5 and the lower die 6 are made of medium silicon molybdenum nodular cast iron. The thickness of a single-side gap between the upper die 5 and the lower die 6 is 0.8mm, and the thickness of a single-side gap between the guide sliding and the sliding is 0.3 mm; the diameter of the hanging rod 4 is phi 50mm, the diameter of the end of the rod body is 10-20mm larger than the diameter of the middle of the rod body, the size of the guide plate 7 is 440X120mm, the size of the screw 10 is phi 12mmH70, and the size of the material taking groove 11 is not smaller than 100X100 mm.

The skin forming method of the composite forming tool based on the large-curvature titanium alloy skin part comprises the following steps of:

the first step is as follows: the titanium alloy part is adhered with the aluminum strips, and because the hardness and the strength of the titanium alloy material are higher than those of aluminum alloy, the titanium alloy part damages a clamping jaw of skin stretching equipment, so that the aluminum strips are adhered to two ends of a titanium alloy plate before the skin stretching; adhering 45mm process aluminum strips on the surfaces of the parts contacted with the two ends of the jaw through adhesive films before stretching; firstly, cleaning two ends of an aluminum plate by using acetone within a range of 50 millimeters, removing burrs of a technical aluminum strip, and cleaning a gluing surface by using acetone; the treated parts and the process aluminum strips are not allowed to be touched by naked hands, and are wrapped by plastic cloth or wrapping paper to be assembled; preheating an aluminum strip, pasting an adhesive film, assembling an aluminum sheet pasted with the adhesive film on an aluminum plate, and heating and fixing by using a blower; paving a ventilating felt on the part, covering a vacuum bag, packaging the periphery of the part by using a sealing rubber strip and then feeding the part into an autoclave; curing according to autoclave curing process; finally, cleaning work is carried out, the vacuum bag and the air felt are removed, and the residual glue is cleaned; if no problem exists, the next step is carried out;

the second step is that: placing a tool, namely sleeving a sling in the cast-in type lifting hooks 2 at two ends of the tire body 1 to ensure the lifting safety, firstly placing the drawing die at the central position of a drawing machine by using a crane, and secondly placing the drawing tool at the central position of a platform by using the crane; the tool and the platform are well fixed, then the position is well arranged according to the stretching direction and the direction of the jaw is consistent with the jaw direction, the die is cleaned, and the surface of the die is coated with oil;

the third step: cold process stretch forming, checking whether the material thickness and the surface state material surface are not allowed to have cracks, delaminations, non-metallic inclusions, bubbles, burning loss, corrosion spots and burrs at the material edge are removed or not; placing two ends of a part blank in a jaw of a stretcher, enabling an end head to be in contact with the bottom end of the jaw, ensuring that the jaw is closed by a clamping amount, controlling the stretching tonnage in the process of clamping the blank part to be stretched, ensuring that the stretching rate is not more than 6% according to elongation test paper, knocking the surface of the part by using a rubber beating plate, checking whether the part is adhered to a tire, processing qualified parts for the first time, and storing and recording a pressurizing track for subsequent part forming; opening the jaw, taking the part out of the jaw, paying attention to protect the surface of the part, preventing scratching, checking whether the surface of the part has serious slip lines or not, checking whether the surface of the part has serious bulges or pits or not due to coarse grains, checking whether the surface of the part has serious scratches, checking whether the part is attached to a tool or not and checking whether the part has obvious gaps or not, and performing a hot forming process after the part is checked to be qualified;

the fourth step: the titanium alloy is hot-formed, wash the mould profile of hot-forming on the surface of the woollen with propanone at first; then, coating a lubricant, uniformly coating graphite on the surface of the blank and the working surface of the hot forming die, and increasing the coating amount of the reference die profile at the part with large curvature change and local stretching forming; then, mounting the hot forming die in the center of a platform of the hot forming machine by using a crane and a forklift; carrying out pressure test according to the complexity of the molded surface, firstly fixing an upper die 5, utilizing an equal-thickness aluminum material to carry out die assembly pressure test to adjust a die gap, and fixing a lower die 6 after the die assembly pressure test is finished; after fixation, the temperature is raised according to the requirement of the thermal forming temperature, and the temperature raising rate is less than or equal to 75 ℃/h; after the temperature of the preheating equipment is stable, placing the wool into an equipment platform or a mould, preheating the wool according to the requirement of preheating time for forming, positioning the wool according to a molded surface, placing the wool into a lower mould 6, closing the mould according to the requirement of forming pressure, maintaining the pressure according to the requirement of pressure maintaining time, and finally taking out the part;

the fifth step: inspecting the part, inspecting the tire sticking degree of the part according to an inspection die, wherein the sticking gap between the part and the tool is not more than 0.5 mm;

and a sixth step: and after the part is detected to be qualified, the screw 10 is pulled out, the part is taken down, and the subsequent paint spraying process is carried out.

Claims (3)

1. The composite forming tool for the large-curvature titanium alloy skin part is characterized by comprising a drawing die and a hot forming die;

the drawing die comprises a tire body (1), a cast-in lifting hook (2) and a positioning reference platform (3); the hot forming die comprises a hanging rod (4), an upper die (5), a lower die (6), a guide plate (7), a guide post (8), a positioning pin (9), a screw (10), a material taking groove (11) and a pressure plate groove (12);

the molded surface of the tire body (1) is consistent with the theoretical molded surface of a part; cast-in hooks (2) are arranged on two sides of the tire body (1) in the non-stretching direction and used for preventing the lifting rigging from unhooking; a positioning reference platform (3) is arranged at the top of the tire body (1) and is used for reference establishment and positioning basis of subsequent tool repair during numerical control machining of the tire body (1);

the non-contact surfaces of the upper die (5) and the lower die (6) and the part are of a grid type hollow structure; the molded surface is consistent with the theoretical surface of the part; when the lower die (6) is placed into a thermoforming machine, the lower die is connected with the thermoforming machine through a pressure plate groove (12); during processing, the part is placed on the lower die (6) along with the shape surface and is fixed by a positioning pin (9) arranged on the shape surface of the lower die (6); the two sides of the lower die (6) are provided with hanging rods (4) in the non-stretching direction for preventing the hanging rigging from unhooking; vertical grooves are formed in the stretching directions of the two sides of the lower die (6) and used for accommodating the guide plates (7); a guide post (8) arranged on the edge of the upper end of the lower die (6) is matched with a guide hole at the lower end of the upper die (5) during die assembly, a guide plate (7) is arranged on the edge of the joint between the upper die (5) and the lower die (6) after die assembly, the upper die (5) is fixedly connected with the upper end of the guide plate (7) through a screw (10), and the lower end of the guide plate (7) is embedded into a vertical groove of the lower die (6); and a material taking groove (11) is arranged at the edge of the side surface of the lower die (6), and the material taking groove (11) is a concave platform processed along with the shape surface and used for taking out the part after the part is thermoformed.

2. The composite forming tool for the large-curvature titanium alloy skin part according to claim 1, wherein the tire body (1) is made of a resin material or a metal material; the position of the positioning reference platform (3) forms 90 degrees with the stretching direction, the size is not less than 100X100mm, and a reference hole is drilled in the middle; the upper die (5) and the lower die (6) are made of medium silicon molybdenum nodular cast iron.

3. The skin forming method by adopting the composite forming tool for the large-curvature titanium alloy skin part as claimed in claim 1 or 2, is characterized by comprising the following steps of:

the first step is as follows: pasting an aluminum strip on the titanium alloy part, and pasting a 45mm technical aluminum strip on the surface of the part contacted with the two ends of the jaw through an adhesive film before stretching; firstly, cleaning two ends of an aluminum plate by using acetone within a range of 50 millimeters, removing burrs of a technical aluminum strip, and cleaning a gluing surface by using acetone; the treated parts and the processed aluminum strips are not allowed to be touched by bare hands, and are wrapped by plastic cloth or wrapping paper to be assembled; preheating an aluminum strip, pasting an adhesive film, assembling an aluminum sheet pasted with the adhesive film on an aluminum plate, and heating and fixing by using a blower; paving a ventilating felt on the part, covering a vacuum bag, packaging the periphery of the part by using a sealing rubber strip and then feeding the part into an autoclave; curing according to autoclave curing process; finally, cleaning work is carried out, the vacuum bag and the air felt are removed, and the residual glue is cleaned; if no problem exists, the next step is carried out;

the second step: placing a tool, namely sleeving a sling in cast-in type lifting hooks (2) at two ends of a tire body (1) to ensure safe lifting, placing a drawing die at the central position of a drawing machine by using a crane, and placing a drawing tool at the central position of a platform by using the crane; the tool and the platform are well fixed, then the position is well arranged according to the stretching direction and the direction of the jaw is consistent with the jaw direction, the die is cleaned, and the surface of the die is coated with oil;

the third step: cold process stretch forming, checking whether the thickness of the material and the surface state of the material are not allowed to have cracks, delaminations, non-metallic inclusions, bubbles, burning loss, corrosion spots and burrs on the edge of the material are removed or not; placing two ends of a rough part into a jaw of a stretcher, enabling an end head to be in contact with the bottom end of the jaw, ensuring that the jaw is closed by a clamping amount, controlling the stretching tonnage in the process of clamping the rough part to be stretched, ensuring that the stretching rate does not exceed 6% according to elongation test paper, knocking the surface of the part by using a rubber striking plate, checking whether the part is adhered to a tire, and storing and recording a pressurizing track for forming a subsequent part after the qualified part is machined for the first time; opening the jaw, taking the part out of the jaw, paying attention to protect the surface of the part, preventing scratching, checking whether the surface of the part has serious slip lines or not, checking whether the surface of the part has serious bulges or pits or not due to coarse grains, checking whether the surface of the part has serious scratches, checking whether the part is attached to a tool or not and checking whether the part has obvious gaps or not, and performing a hot forming process after the part is checked to be qualified;

the fourth step: carrying out titanium alloy thermoforming, namely cleaning the molded surface of a thermoforming mold on the surface of the blank by using acetone; then, coating a lubricant, uniformly coating graphite on the surface of the blank and the working surface of the hot forming die, and increasing the coating amount of the reference die profile at the part with large curvature change and local stretching forming; then, mounting the hot forming die in the center of a platform of the hot forming machine by using a crane and a forklift; carrying out pressure test according to the complexity of the molded surface, firstly fixing an upper die (5), adjusting a die gap by using die assembly pressure test of an equal-thickness aluminum material, and fixing a lower die (6) after completing the pressure test; after fixation, the temperature is raised according to the requirement of the thermal forming temperature, and the temperature raising rate is less than or equal to 75 ℃/h; after the temperature of the preheating equipment is stable, placing the wool into an equipment platform or a mould, preheating the wool according to the requirement of preheating time for forming, positioning the wool according to a molded surface, placing the wool into a lower mould (6) for mould assembly according to the requirement of forming pressure, arranging a guide plate (7) at the edge of the butt joint between an upper mould (5) and the lower mould (6) after mould assembly, fastening and connecting the upper mould (5) and the upper end of the guide plate (7) through a screw (10), embedding the lower end of the guide plate (7) into a vertical groove of the lower mould (6), maintaining pressure according to the requirement of pressure maintaining time, and finally taking out a part;

the fifth step: inspecting the part, inspecting the tire sticking degree of the part according to an inspection die, wherein the sticking gap between the part and the tool is not more than 0.5 mm;

and a sixth step: and after the part is detected to be qualified, the screw (10) is pulled out, the part is taken down, and the subsequent paint spraying process is carried out.

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