Method and device for forming high-temperature titanium alloy variable-curvature thin-wall conical cylinder component

Abstract

The invention relates to a forming method and device for a high-temperature titanium alloy variable-curvature thin-wall conical cylinder component, belongs to the field of precise forming of high-temperature titanium alloy complex molded surface components, and solves the problems of low precision, large material performance loss and low forming efficiency in the forming process of the high-temperature titanium alloy complex molded surface components in the prior art. The invention discloses a forming process method for a high-temperature titanium alloy variable-curvature thin-wall conical cylinder component. The forming process method comprises the following steps that S1, blanking and pretreatment are conducted; s2, mold preheating is conducted, specifically, a mold is preheated to 850-880 DEG C; s3, the blank is preheated for 10 min to 35 min till the forming temperature reaches 850 DEG C to 880 DEG C; s4, skin thermal forming is conducted, specifically, forming is started, and pressure maintaining is conducted for 30-50 min; s5, skin forming post-treatment is carried out; s6, the sectioning skin is welded; the barrel assembled in the thermal bulging tool is put into vacuum thermal bulging equipment to be heated to 850 DEG C, and after temperature equalization is conducted for 1 hour, segmented pressurization is conducted for thermal bulging; and S8, cylinder bulging aftertreatment is conducted. And low loss of forming performance and high profile precision of the high-temperature titanium alloy conical cylinder component are realized.

Description

Technical Field

[0001] The invention relates to the technical field of precision hot forming of high-temperature titanium alloy complex-profile components, and in particular to a forming method and a device for a high-temperature titanium alloy variable-curvature thin-walled conical cylinder component. Background Art

[0002] High-temperature titanium alloy (Ti60) is a newly developed titanium alloy material with excellent properties such as high specific strength and high temperature resistance. It has good strength and high-temperature creep performance at a high temperature of 600°C and is increasingly widely used in the aerospace field.

[0003] In high-speed aircraft, it is generally used in the nose cone of the air intake. As a central cone component, it generally has a large diameter change, a complex aerodynamic surface, requires high surface precision, and is difficult to form. Titanium alloys are generally formed using a hot forming process. The sheet is heated to a reasonable temperature and then pressurized. The upper and lower molds are closed, the sheet is deformed and molded to obtain the required part surface.

[0004] However, there are currently no reliable forming process parameters and process equipment for the hot forming process of complex-surface high-temperature titanium alloy conical cylinder components. Traditional hot forming and hot forming and hot expansion composite process solutions are difficult to meet the requirements of component surface accuracy and performance loss. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a method and device for forming a high-temperature titanium alloy variable-curvature thin-walled conical cylinder component, so as to solve at least one of the problems of low profile accuracy, large material performance loss, and low forming efficiency in the existing thin-walled conical cylinder component forming process.

[0006] On the one hand, an embodiment of the present invention provides a method for forming a high-temperature titanium alloy variable curvature thin-walled conical cylinder component, comprising the following steps:

[0007] S1. Cutting and pre-processing: According to the cylinder skin model, the size of the unfolded flat blank is obtained in the software, and the cutting and pre-processing are performed;

[0008] S2. Preheating the mold: Install the thermoforming mold on the thermoforming press and preheat it to 850-880°C; the convex model surface of the thermoforming mold matches the two half-tube skins arranged in mirror symmetry, and the mold as a whole is saddle-shaped;

[0009] S3. Preheating of the blank: Place the high-temperature titanium alloy blank on the convex die of the preheated hot forming mold, and preheat for 10-15 minutes after closing the mold to a forming temperature of 850-880°C; the high-temperature titanium alloy blank is symmetrically arranged in two semi-cylindrical shapes, with the small end of the cone close to the symmetry axis;

[0010] S4, skin hot forming: start forming, keep pressure for 10-20 minutes, and then take out the formed cylinder skin;

[0011] S5. Post-processing of the skin: After the formed barrel skin is subjected to alkali-disintegration pickling, laser cutting is performed to obtain the barrel split skin;

[0012] S6, welding the split skin: the split skin obtained in step S5 is cleaned and placed in a welding tool, and welded into a cylinder under argon protection;

[0013] S7. Vacuum expansion of cylinder: Assemble the welded cylinder on the expansion tooling according to the profile and put it into the vacuum expansion equipment to heat up to 850℃. After averaging the temperature for 1 hour, load the pressure in stages to make the cylinder reach the designed size, and then keep the temperature and pressure to finalize the size.

[0014] S8. Post-processing of cylinder bulging: After cooling, the cylinder is taken out from the hot bulging tooling, and the edges are trimmed to obtain the final conical cylinder component.

[0015] Exemplarily, in step S7, the hot expansion tooling includes a base, expansion petals mounted on the base, and an expansion core cooperating with the expansion petals; the base is provided with guide grooves for the expansion petals to slide.

[0016] Furthermore, in step S7, the segmented pressure loading includes two stages. The first stage of pressurization makes the hot expansion equipment platform fit tightly with the expansion core, and the second stage of pressurization makes the expansion petals slide outward along the base guide groove to reach the designed size of the cone cylinder component.

[0017] Specifically, in step S7, the pressurization tonnage of the first stage is 10 tons, and the pressurization tonnage of the second stage is 50 tons.

[0018] Furthermore, in step S7, after reaching the designed size of the cone cylinder component, pressure and temperature are maintained, with a pressure of 50 tons and a temperature maintenance time of 45 minutes.

[0019] On the other hand, an embodiment of the present invention provides a high-temperature titanium alloy variable-curvature thin-walled conical cylinder component forming device, which is used in the forming process method, including a hot forming mold, a welding tool and a hot expansion tool.

[0020] Specifically, the thermoforming mold includes a punch and a die, with the punch at the bottom and the die at the top; the mold shape is that the two half-cylinder skins after splitting are arranged in mirror symmetry, with the small end of the cone close to the axis of symmetry; the draft angle of the edge of the thermoforming mold is 3° to 5°.

[0021] Further, the welding tooling includes a support assembly, a positioning assembly, an inner support plate and a welding protective airflow channel groove plate;

[0022] The positioning assembly is arranged along the central axis of the support assembly and is connected to the support assembly through the inner support plate; the welding protection air flow channel groove plate is symmetrically installed on the outer edges of both sides of the inner support plate;

[0023] The support assembly includes two outer ring plates, one or more outer reference plates and tie rods. The outer ring plates and the outer reference plates are provided with holes matching the size of the tie rods at corresponding positions. The outer ring plates and the outer reference plates are fixedly connected with the tie rods.

[0024] The positioning assembly includes two end reference plates, one or more internal reference plates, a reference shaft, a gasket and a fastening nut. The reference shaft passes through the center of the reference plate and is fixedly connected to the reference plate through the gasket and the fastening nut.

[0025] Exemplarily, the thermal expansion tooling includes a base, expansion petals mounted on the base, and an expansion core matched with the expansion petals in shape;

[0026] The base is provided with a guide groove, an adjusting bolt and a nut, the bottom of the expansion petal is provided with a sliding block matching the guide groove of the base, and the sliding block is fixed at a specific position of the guide groove by means of the adjusting bolt and the nut.

[0027] It is worth noting that the profile size of the hot expansion tooling is L1=L×0.996, and the profile size of the hot forming mold is L2=L1×0.996=L×0.996×0.996=L×0.992, where L is the profile size of the target component.

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0029] 1. The present invention accurately controls and reduces the high-temperature hot forming time, avoids the formation of an oxygen-rich layer, and reduces material performance loss; and can reduce the generation of thermal stress, thereby preventing product deformation and improving product dimensional accuracy; shortening the high-temperature forming time can also reduce energy consumption and reduce production costs.

[0030] 2. In the hot forming process of the present invention, the two half-cylinder skins after separation are designed in a set of molds and arranged in sequence along the axial direction. The two half-cylinder skins are arranged in mirror symmetry, and the symmetry axis of the two mirror symmetries is perpendicular to the axial direction of the half-cylinder skins. The small end of the cone is close to the symmetry axis, so that the forces of various parts in the mold are balanced, effectively avoiding the generation of lateral forces during the forming process, as well as the resulting mold dislocation and skin deformation; and realizing the one-time forming of the cylinder component, thereby improving the hot forming efficiency.

[0031] 3. The present invention provides a welding protective gas flow channel on the welding tool to protect the inner weld. Compared with filling the entire cylinder with protective gas, it ensures welding quality while improving efficiency.

[0032] 4. The present invention accurately controls the temperature of the thermal expansion process and performs multi-stage pressure control. By controlling the pressure and node of each pressurization, the amount of pressure reduction of the core can be accurately adjusted to ensure the expansion amount of the cylinder and control the final surface accuracy of the cylinder within ±0.3mm.

[0033] 5. The present invention adopts a composite process of high-temperature hot forming and vacuum hot bulging to ensure low loss of material performance while improving surface accuracy; the process processing dimension chain is determined according to the processing sequence, and the scaling coefficient of the mold and tooling is determined according to the difference in thermal expansion coefficient between the mold and tooling materials and the high-temperature titanium alloy (Ti60) material, and the hot forming mold surface and the hot bulging tooling surface are scaled respectively. Through double scaling, the accurate surface size after forming is ensured.

[0034] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0036] Figure 1 It is a schematic diagram of a variable curvature thin-walled conical cylinder component of the present invention;

[0037] Figure 2 Schematic diagram of the thermoforming mold of the present invention Figure 1 ;

[0038] Figure 3 Schematic diagram of the thermoforming mold of the present invention Figure 2 ;

[0039] Figure 4 This is a schematic diagram of the welding tooling of the present invention;

[0040] Figure 5 It is a schematic diagram of the thermal expansion tooling of the present invention.

[0041] Reference numerals:

[0042] 1-die; 2-punch; 3-skin; 401-end reference plate; 402-inner reference plate; 403-outer reference plate; 5-outer ring plate; 6-inner support plate; 7-reference shaft; 8-washer ring; 9-fastening nut; 10-flow channel plate; 11-pull rod; 12-base; 1201-guide groove; 13-expansion core; 14-expansion petal. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0044] A specific embodiment of the present invention discloses a high-temperature titanium alloy variable curvature thin-walled conical cylinder component forming process method, comprising the following steps:

[0045] S1. Cutting and pre-processing: According to the cylinder skin model, the size of the unfolded flat blank is obtained in the software, and the cutting and pre-processing are performed;

[0046] S2. Preheating the mold: Install the thermoforming mold on the thermoforming press and preheat it to 850-880°C; the convex model surface of the thermoforming mold matches the two half-tube skins arranged in mirror symmetry, and the mold as a whole is saddle-shaped;

[0047] S3. Preheating of the blank: Place the high-temperature titanium alloy blank on the convex die of the preheated hot forming mold, and preheat for 10-15 minutes after closing the mold to a forming temperature of 850-880°C; the high-temperature titanium alloy blank is symmetrically arranged in two semi-cylindrical shapes, with the small end of the cone close to the symmetry axis;

[0048] S4, skin hot forming: start forming, keep pressure for 10-20 minutes, and then take out the formed cylinder skin;

[0049] S5. Post-processing of the skin: After the formed barrel skin is subjected to alkali-disintegration pickling, laser cutting is performed to obtain the barrel split skin;

[0050] S6, welding the split skin: the split skin obtained in step S5 is cleaned and placed in a welding tool, and welded into a cylinder under argon protection;

[0051] S7. Vacuum expansion of cylinder: Assemble the welded cylinder on the expansion tooling according to the profile and put it into the vacuum expansion equipment to heat up to 850℃. After averaging the temperature for 1 hour, load the pressure in stages to make the cylinder reach the designed size, and then keep the temperature and pressure to finalize the size.

[0052] S8. Post-processing of cylinder bulging: After cooling, the cylinder is taken out from the hot bulging tooling, and the edges are trimmed to obtain the final conical cylinder component.

[0053] Specifically, in step S1, the cylinder split skin model is divided into two symmetrical half cylinders along the circumference of the conical cylinder component; unfolding is performed in UG software to obtain unfolded material, and a peripheral margin of 30-50 mm is added as the skin blank size; laser cutting is used to obtain skin blanks, burrs on the edges of the blanks are polished, and pre-rolling is performed to form the flat blanks into conical cylinders, wherein the minimum radius of the cylinder is greater than the minimum radius of the target cylinder; aqueous graphite is coated on the upper and lower surfaces of the blanks to prevent oxidation and lubricate, and the graphite protrusions are polished with sandpaper after air drying to ensure a smooth coating.

[0054] Furthermore, in step S2, the manufactured thermoforming mold is cleaned, a high temperature lubricating coating is sprayed on the mold surface, and then the mold is installed on a thermoforming press, the process parameters are set, and the temperature is raised to 850-880°C.

[0055] During the hot forming process, the two half-cylinder skins after separation are designed in a set of molds and arranged in a mirror-symmetrical manner, with the small end of the cone close to the axis of symmetry. This balances the forces on each part of the mold and effectively avoids lateral forces during the forming process, as well as the resulting mold misalignment and skin deformation. It also enables the cylinder component to be formed in one go, improving the efficiency of hot forming.

[0056] Exemplarily, the high-temperature lubricating coating is graphite; the material of the hot forming mold is Ni7N high-temperature stainless steel, and the mold heating rate is 2°C / min. Too fast a heating rate will lead to poor thermal uniformity of the mold, affecting the forming quality of the skin; the skin material is high-temperature titanium alloy (Ti60). According to the heat treatment characteristics of Ti60, the preheating temperature of the mold is determined to be 850-880°C. Too low a preheating temperature will lead to insufficient forming, and too high a preheating temperature will cause damage to the mold, thereby affecting the forming quality and stability;

[0057] In one possible design, the preheat temperature of the hot forming mold is 850°C.

[0058] Further, in steps S3 and S4, when the mold temperature reaches 850-880°C, the high-temperature titanium alloy blank is placed on the convex mold of the preheated hot forming mold, and the high-temperature titanium alloy blank is symmetrically arranged in two semi-cylindrical shapes, wherein the small end of the conical cylinder is close to the symmetry axis. After the mold is closed, the preheating time is determined to be 10-15 minutes according to the thickness of the blank. After the blank reaches the forming temperature, the forming begins, the pressure is 20 tons, and the pressure is maintained for 10-20 minutes to achieve the part fitting the mold, and the high-temperature creep releases the internal stress; after the end, the formed cylinder skin is taken out;

[0059] In a possible design, after the mold temperature reaches 850°C, a high-temperature titanium alloy billet is placed in for preheating. The billet thickness is 2 mm and the preheating time is 10 minutes. Hot forming is then started with a forming pressure of 20 tons and a holding time of 20 minutes.

[0060] Accurately control and reduce the high-temperature hot forming time to less than 20 minutes, effectively avoid the formation of oxygen-rich layer and reduce material performance loss; shortening the high-temperature hot forming time can also reduce the generation of thermal stress, improve product dimensional accuracy and reduce energy consumption.

[0061] Preferably, in step S5, the skin is subjected to alkali-blanket pickling to remove the surface oxide scale, and then laser cutting is performed to complete the half-skinning of the cylinder. When cutting, no allowance is left in the curvature direction of the skin, and an allowance of 10-20 mm is left in the length direction.

[0062] Furthermore, in step S6, the surface of the longitudinal weld of the skin is cleaned before welding, polished to reveal the metallic luster, and wiped with acetone or alcohol to ensure the surface cleanliness and ensure the welding quality; argon gas protection is performed during the welding process, and X-ray inspection is performed after single-sided welding and double-sided forming welding to ensure the quality of the weld.

[0063] Exemplarily, in step S7, the hot expansion tooling includes a base, expansion petals mounted on the base, and an expansion core matched with the expansion petals; the base is provided with a guide groove for the expansion petals to slide;

[0064] During the hot expansion process, the expansion amount of the cylinder is adjusted by adjusting the amount of pressure on the expansion core. When the cylinder surface is too small, the expansion petals are made to slide toward the outer surface by increasing the amount of pressure on the expansion core to ensure the final cylinder surface accuracy.

[0065] Furthermore, in step S7, the segmented pressure loading includes two stages. The first stage of pressurization makes the hot expansion equipment platform fit tightly with the expansion core, and the second stage of pressurization makes the expansion petals slide outward along the base guide groove to reach the designed size of the cone cylinder component.

[0066] Specifically, in step S7, the pressurization tonnage of the first stage is 10 tons, and the pressurization tonnage of the second stage is 50 tons.

[0067] Furthermore, in step S7, after reaching the designed size of the cone cylinder component, pressure and temperature are maintained, with a pressure of 50 tons and a temperature maintenance time of 45 minutes.

[0068] During the hot bulging process, multi-level pressure control is performed to accurately adjust the amount of pressure on the core. In the first stage, a smaller tonnage of pressure is used to make the core fit tightly against the equipment platform, ensuring that the platform, core and petal mold are in close contact to ensure clamping accuracy. In the second stage, a larger tonnage of pressure is used to ensure sufficient forming. While the core moves downward to the bottom, each petal moves circumferentially to fully bulge the cylinder. According to the bulging result of the first piece, the diameter of the cylinder after bulging can be controlled by controlling the tonnage or the amount of pressure on the platform to achieve precise control.

[0069] On the other hand, a specific embodiment of the present invention discloses a high-temperature titanium alloy variable-curvature thin-walled conical cylinder component forming device, which is used in the forming process method, including a hot forming mold, a welding tool and a hot expansion tool.

[0070] Specifically, the thermoforming mold includes a male mold and a female mold, wherein the male mold is at the bottom and the female mold is at the top, and the male and female molds are positioned by the molding surface; the mold shape is that the two half-cylinder skins after the petals are arranged in mirror symmetry, wherein the small end of the cone is close to the symmetry axis; the draft angle of the edge of the thermoforming mold is 3°~5°.

[0071] It is worth noting that the two half-tube skins are designed in a set of molds and arranged in mirror symmetry. The small end of the cone is close to the symmetry axis, the profile is saddle-shaped, and the force point is at the center of the mold, so that the forces of various parts in the mold are balanced, effectively avoiding the lateral force generated during the forming process, as well as the resulting mold dislocation and skin deformation; and realizing the one-time forming of the cylinder components, improving the efficiency of hot forming;

[0072] According to the hot forming temperature of high-temperature titanium alloy materials and the shape characteristics of conical cylinder components, the draft angle is designed to be 3°~5°, which can effectively reduce the friction between the cylinder and the hot forming mold, improve the demoulding performance and the surface quality of the component; if the draft angle is too large, the dimensional accuracy of the component will be reduced, especially the accuracy of the edge area; if the draft angle is too small, it will lead to demoulding difficulties and increase mold loss.

[0073] In one possible design, the draft angle at the edge of the thermoforming mold is 5°.

[0074] Further, the welding tooling includes a support assembly, a positioning assembly, an inner support plate and a welding protective airflow channel groove plate;

[0075] The positioning assembly is arranged along the central axis of the support assembly and is connected to the support assembly through the inner support plate; the welding protection air flow channel groove plate is symmetrically installed on the outer edges of both sides of the inner support plate;

[0076] The support assembly includes two outer ring plates, one or more outer reference plates and tie rods. The outer ring plates and the outer reference plates are provided with holes matching the size of the tie rods at corresponding positions. The outer ring plates and the outer reference plates are fixedly connected with the tie rods.

[0077] The positioning assembly includes two end reference plates, one or more internal reference plates, a reference shaft, a gasket and a fastening nut. The reference shaft passes through the center of the reference plate and is fixedly connected to the reference plate through the gasket and the fastening nut.

[0078] Specifically, the half-cylinder skin is clamped between the inner support plate, the outer ring plate and the outer reference plate, and assembled according to the size of the inner support plate, in which the inner support plate plays a supporting and fixing role; and the axial length is positioned by the outer ring plates at both ends, and the two half-cylinder skins are clamped on the tooling by tightening the center axis.

[0079] Exemplarily, the thermal expansion tooling includes a base, expansion petals mounted on the base, and an expansion core matched with the expansion petals in shape;

[0080] The base is provided with a guide groove, an adjusting bolt and a nut, the bottom of the expansion petal is provided with a slider matching the guide groove of the base, and the slider is fixed at a specific position of the guide groove by adjusting bolts and nuts; the matching clearance between the slider and the guide groove is greater than 0.5mm;

[0081] In a possible design, the base guide groove is a dovetail groove, which has the characteristics of strong rigidity and good stability, and has a certain self-locking ability.

[0082] The outer shape of the expansion petals is a scaled part surface, the inner shape is a tapered cavity matched with an expansion core, and the number of the expansion petals is designed to be 8-12 according to the complexity and weight of the surface.

[0083] Specifically, the hot expansion tooling material is stainless steel 1Cr18Ni9Ti, and a gap of 5-10mm is left between the expansion petals compared to the scaled part surface. The expansion petals are symmetrically distributed according to the outer surface, and the minimum thickness is 30mm to ensure rigidity; each expansion petal is provided with a processing mark line to locate the position of the cylinder when assembling the cylinder before expansion.

[0084] Exemplarily, a lifting device is also designed on the base, and initial assembly position lines of the expansion flaps and the expansion core are engraved on the surface of the base.

[0085] Specifically, the expansion core is a hollow cylinder with a taper, which is designed according to the deformation of the cylinder after welding and the measurement of the surface accuracy before correction. During the hot expansion process, the expansion amount of the cylinder is adjusted by adjusting the amount of pressure on the expansion core. When the cylinder surface is too small, the expansion petals are made to slide toward the outer surface by increasing the amount of pressure on the expansion core to ensure the final cylinder surface accuracy.

[0086] Assembly process of cylinder and hot expansion tooling: Before assembly, ensure that the surface of cylinder and tooling is clean and undamaged. First, install the expansion petals on the base according to the profile and place them at the position with the smallest circumferential diameter. Then, sleeve the welded cylinder on the expansion petals and keep the bottom of the cylinder in contact with the base.

[0087] It is worth noting that the profile size of the hot expansion tooling is L1=L×0.996, and the profile size of the hot forming mold is L2=L1×0.996=L×0.996×0.996=L×0.992, where L is the profile size of the target component.

[0088] The dimension chain is determined according to the difference in thermal expansion coefficient between the mold and tooling materials and the high-temperature titanium alloy (Ti60) material, and the hot forming mold surface and the hot expansion tooling surface are scaled respectively. Through double scaling, the accurate size of the surface after forming is guaranteed.

[0089] Specifically, the hot forming mold is made of Ni7N high-temperature stainless steel, and the hot expansion tooling material is stainless steel 1Cr18Ni9Ti. The surface scaling coefficients of the tooling and the mold are determined based on the differences in thermal expansion coefficients of Ti60, Ni7N, and 1Cr18Ni9Ti and the tolerance requirements of the cylinder.

[0090] In summary, the present invention adopts a composite process of high-temperature thermoforming and vacuum hot bulging, and performs dual scaling of the mold and the bulging tooling to ensure low loss of material performance while improving the surface accuracy; through the symmetrical design of the hot forming mold, the generation of lateral force during the forming process and the resulting mold dislocation and skin deformation are avoided; the high-temperature hot forming time is accurately controlled and reduced to avoid the formation of an oxygen-rich layer, reduce the generation of thermal stress, reduce material performance loss and improve product dimensional accuracy; the hot bulging process performs multi-stage pressure control, and by controlling the pressure and node of each pressurization, the precise adjustment of the core expansion amount is achieved to ensure that the cylinder bulging amount and the accuracy of the final cylinder surface are ≤±0.3mm.

[0091] The process method and device of the present invention are further described below in conjunction with specific embodiments.

[0092] Example

[0093] In this embodiment, a high-temperature titanium alloy variable curvature thin-walled conical cylinder component is prepared. The material is Ti60. The dimensional characteristics of the component are as follows: the height of the conical cylinder is 650m, the wall thickness of the conical cylinder is 2mm, the diameter of the large end of the profile is 450mm, and the diameter of the small end is 310mm. It is a pneumatic profile with complex variable curvature characteristics, and the dimensional accuracy required to be achieved is ±0.3mm;

[0094] The number of expansion petals of the hot bulging tooling is 8; the hot forming mold is made of Ni7N high-temperature stainless steel, and the hot bulging tooling material is stainless steel 1Cr18Ni9Ti; the hot bulging tooling surface size is L1=L×0.992, and the hot forming mold surface size is L2=L×0.996.

[0095] The specific forming process is as follows:

[0096] S1. Cutting and pre-processing: The cylinder split skin model is divided into two symmetrical half cylinders along the circumference of the cone cylinder component; unfolding is performed in UG software to obtain unfolded material, and a peripheral margin of 30 mm is added as the skin blank size; laser cutting is used to cut the skin blank, the burrs on the edge of the blank are polished, and pre-rolling is performed to form the flat blank into a cone cylinder, in which the minimum radius of the cylinder is larger than the minimum radius of the target cylinder; water-based graphite is coated on the upper and lower surfaces of the blank to play an anti-oxidation and lubricating role, and the graphite convex points are polished with sandpaper after air drying to ensure smooth coating;

[0097] S2. Mold preheating: clean the manufactured hot forming mold, spray high temperature lubricating paint on the mold surface, install it on the hot forming press, and heat up to 850℃ at a heating rate of 2℃ / min;

[0098] S3, preheating the blank: put the high-temperature titanium alloy blank into the preheated hot forming mold and preheat it for 10 minutes to the forming temperature of 850°C;

[0099] S4, skin hot forming: start forming, pressure 20 tons, hold the pressure for 10 minutes, and then take out the formed cylinder skin;

[0100] S5. Post-processing of the skin: After the formed barrel skin is subjected to alkali-disintegration pickling, laser cutting is performed to obtain the barrel skin. When cutting, no allowance is left in the curvature direction of the skin, and an allowance of 15mm is left in the length direction;

[0101] S6. Welding of split skin: Before welding the longitudinal weld of the skin, clean the surface, grind it to reveal the metallic luster, wipe it with acetone or alcohol, ensure the surface cleanliness and welding quality, and put it into the welding tooling; during the welding process, fill argon gas through the protective gas flow channel for protection, perform X-ray inspection after single-sided welding and double-sided forming welding to ensure the quality of the weld and obtain the cylinder;

[0102] S7, vacuum expansion of cylinder: assemble the welded cylinder on the expansion tooling according to the profile and put it into the vacuum expansion equipment and heat it to 850°C. After averaging the temperature for 1 hour, load the pressure in stages. The first stage pressurization tonnage is 10 tons, so that the expansion equipment platform and the expansion core are closely fitted. The second stage pressurization tonnage is 50 tons. After the cylinder reaches the designed size, keep the temperature and pressure at 50 tons for 45 minutes to achieve size finalization.

[0103] S8. Post-processing of cylinder bulging: After cooling, the cylinder is taken out from the hot bulging tooling, and the edges are trimmed to obtain the final conical cylinder component.

[0104] After testing by contour detection equipment, the surface accuracy is 0.25mm, which meets the deformation requirements of variable curvature cylindrical components.

[0105] In summary, the present invention adopts a composite process of high-temperature thermoforming and vacuum hot bulging, and performs dual scaling of the mold and the bulging tooling to ensure low loss of material performance while improving the surface accuracy; through the symmetrical design of the hot forming mold, the generation of lateral force during the forming process and the resulting mold dislocation and skin deformation are avoided; the high-temperature hot forming time is accurately controlled and reduced to avoid the formation of an oxygen-rich layer, reduce the generation of thermal stress, reduce material performance loss and improve product dimensional accuracy; the hot bulging process performs multi-stage pressure control, and by controlling the pressure and node of each pressurization, the precise adjustment of the core expansion amount is achieved to ensure that the cylinder bulging amount and the accuracy of the final cylinder surface are ≤±0.3mm.

[0106] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for forming a high-temperature titanium alloy variable curvature thin-walled conical cylinder component, characterized in that: The steps include: S1. Cutting and pre-processing: According to the cylinder skin model, the size of the unfolded flat blank is obtained in the software, and the cutting and pre-processing are performed; S2. Preheating the mold: Install the thermoforming mold on the thermoforming press and preheat it to 850-880°C; the convex model surface of the thermoforming mold matches the two half-tube skins arranged in mirror symmetry along the axial direction, and the mold as a whole is saddle-shaped; S3. Preheating of the blank: Place the high-temperature titanium alloy blank on the convex die of the preheated hot forming mold, and preheat for 10-15 minutes after closing the mold to a forming temperature of 850-880°C; the high-temperature titanium alloy blank is two semi-conical cylindrical blanks, which are arranged in sequence along the axial direction and are mirror-symmetrical, with the small end of the cone close to the symmetry axis; S4, skin hot forming: start forming, keep pressure for 10-20 minutes, and then take out the formed cylinder skin; S5. Post-processing of the skin: After the formed barrel skin is subjected to alkali-disintegration pickling, laser cutting is performed to obtain the barrel split skin; S6, welding the split skin: the split skin obtained in step S5 is cleaned and placed in a welding tool, and welded into a cylinder under argon protection; S7. Vacuum expansion of cylinder: Assemble the welded cylinder on the expansion tooling according to the profile and put it into the vacuum expansion equipment to heat up to 850℃. After averaging the temperature for 1 hour, load the pressure in stages to make the cylinder reach the designed size, and then keep the temperature and pressure to finalize the size. S8. Post-processing of cylinder bulging: After cooling, the cylinder is taken out from the hot bulging tooling, and the edges are trimmed to obtain the final conical cylinder component.

2. The method according to claim 1, characterized in that In step S7, the thermal expansion tooling includes a base, expansion petals mounted on the base, and an expansion core cooperating with the expansion petals; the base is provided with guide grooves for the expansion petals to slide.

3. The method according to claim 2, characterized in that In step S7, the segmented pressure loading includes two stages. In the first stage, pressurization is performed to make the platform of the thermal expansion forming equipment fit tightly with the expansion core. In the second stage, pressurization is performed to make the expansion petals slide outward along the guide groove of the base to reach the designed size of the cone cylinder component.

4. The method according to claim 3, characterized in that In step S7, the pressurization tonnage of the first stage is 10 tons, and the pressurization tonnage of the second stage is 50 tons.

5. The method according to claim 3, characterized in that: In step S7, after reaching the designed size of the cone cylinder component, pressure and temperature are maintained, with a pressure of 50 tons and a temperature maintenance time of 45 minutes.

6. A high-temperature titanium alloy variable curvature thin-walled conical cylinder component forming device, used in the forming process method according to claims 1 to 6, characterized in that: Including hot forming molds, welding tooling and hot expansion tooling.

7. The forming device according to claim 6, characterized in that The thermoforming mold comprises a punch and a die, wherein the punch is at the bottom and the die is at the top; the mold shape is that the two half-cylinder skins after the petals are arranged in mirror symmetry, wherein the small end of the cone is close to the symmetry axis; the draft angle of the edge of the thermoforming mold is 3° to 5°.

8. The forming device according to claim 6, characterized in that: The welding tool comprises a support assembly, a positioning assembly, an inner support plate and a welding protective air flow channel groove plate; The positioning assembly is arranged along the central axis of the support assembly and is connected to the support assembly through the inner support plate; the welding protection air flow channel groove plate is symmetrically installed on the outer edges of both sides of the inner support plate; The support assembly includes two outer ring plates, one or more outer reference plates and tie rods. The outer ring plates and the outer reference plates are provided with holes matching the size of the tie rods at corresponding positions. The outer ring plates and the outer reference plates are fixedly connected with the tie rods. The positioning assembly includes two end reference plates, one or more internal reference plates, a reference shaft, a gasket and a fastening nut. The reference shaft passes through the center of the reference plate and is fixedly connected to the reference plate through the gasket and the fastening nut.

9. The forming device according to claim 6, characterized in that: The thermal expansion tooling comprises a base, expansion petals mounted on the base, and an expansion core matching the shape of the expansion petals; The base is provided with a guide groove, an adjusting bolt and a nut, the bottom of the expansion petal is provided with a sliding block matching the guide groove of the base, and the sliding block is fixed at a specific position of the guide groove by means of the adjusting bolt and the nut.

10. The forming device according to claim 6, characterized in that The profile size of the hot expansion tooling is L1=L×0.996, and the profile size of the hot forming mold is L2=L1×0.996=L×0.996×0.996=L×0.992, wherein L is the profile size of the target component.

Images