Integral forming method of straight cone composite cylinder

Abstract

The invention relates to an integral forming method of a straight cone composite cylinder, belongs to the technical field of precision hot forming processing, and solves the problems of complex process, long period, high processing difficulty, poor product precision and high cost of the existing straight cone composite cylinder. The forming method comprises the following steps: establishing a right cone composite cylinder three-dimensional model; designing and manufacturing a mold, wherein the mold comprises a bulging tire core and a closing-in mold; blanking, circling and welding are conducted, and a whole cone barrel blank is obtained; preheating the blank, and sleeving the blank on a bulging tire core of the mold; the bulging tire core is sleeved with a closing-in die of the die; the assembled mold is heated, and pressure is applied to the closing-in mold and kept; and the mold is cooled and demolded, and the straight cone composite cylinder is obtained. By means of the method, the three-in-one integral forming procedure of closing-in, flaring and bulging of the straight cone composite cylinder can be achieved, the machining procedure is simplified, the machining period is shortened, the machining difficulty and cost are reduced, and the product size precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of precision hot forming processing, and in particular relates to an integral forming method of a straight-taper composite cylinder. Background Art

[0002] Aerospace components are becoming increasingly complex, and straight-cone composite titanium cylinders are widely used in aerospace vehicles as a typical component.

[0003] At present, the straight-cone composite titanium cylinder cannot be directly bulged due to its different diameter change law; the traditional process is to bulge the product through closing bulging, expanding bulging and overall bulging. However, the traditional process has several shortcomings: first, the process is complicated and the processing cycle is long; second, it requires more tooling and the tooling cost is high; third, the processing is difficult, and it takes three hot bulging steps to bulge a product. Each hot bulging step requires mold clamping and positioning, which puts forward high requirements for the reference transfer and operation process; finally, the product surface accuracy is poor. The traditional process products need to go through three processes of closing, expanding and overall bulging. There are bulging errors in each process. After the errors of the three processes are accumulated, the final product surface accuracy error is large.

[0004] In order to solve the deficiencies of the prior art, it is necessary to provide a new straight-cone composite tube forming method, which can not only simplify the forming process, shorten the processing cycle, reduce the cost and processing difficulty, but also improve the product surface accuracy. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide an integrated molding method of a straight-cone composite tube, so as to solve at least one of the problems of the existing traditional process of straight-cone composite tubes, namely, complex process steps, long cycle, great processing difficulty, poor product precision and high cost.

[0006] In a first aspect, an embodiment of the present invention provides an integral molding method of a straight-tapered composite cylinder, the method comprising:

[0007] (1) establishing a three-dimensional model of a straight-cone composite cylinder, and designing and manufacturing a mold, wherein the mold includes a bulging tire core and a closing mold, wherein the bulging tire core includes a conical section, and a large-diameter cylindrical section and a small-diameter cylindrical section respectively located at two ends;

[0008] (2) designing the size of the mold according to the linear expansion coefficient of the straight-tapered composite tube and its size at room temperature, the linear expansion coefficient of the mold component, and the difference between the hot forming temperature and room temperature;

[0009] (3) cutting, rounding and welding are performed according to the unfolded material size of the straight-cone composite cylinder three-dimensional model in the software to obtain a whole-cone cylinder blank;

[0010] (4) first fixing the large diameter end face of the bulging tire core, then preheating the whole cone blank, and sleeved the whole cone blank onto the bulging tire core from the large diameter end of the whole cone, wherein the preheating temperature is equal to the molding temperature;

[0011] (5) The closing die is mounted on the conical section of the bulging tire core to complete the assembly of the die;

[0012] (6) the mold is heated and maintained, and pressure is applied to the closing die through the heating device platform to move the closing die downward, and cooperate with the large-diameter cylindrical section of the bulging tire core to close the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube; in addition, at the molding temperature, the conical section and the small-diameter cylindrical section of the bulging tire core are bulged to form a conical tube section and a small-diameter straight tube section of the straight-cone composite tube, respectively;

[0013] (7) Cooling the mold and demoulding the mold to obtain the straight-cone composite tube.

[0014] Furthermore, in step (2), at the thermoforming temperature, the mold and the part are completely fitted, that is, L 零件 =L 模具 , the size of the mold at room temperature meets:

[0015] L 模具0 = L 零件0 *(1+α 零件 ·ΔT) / (1+α 模具 ·ΔT) (1)

[0016] Among them, L 模具0 —Mold dimensions at room temperature;

[0017] L 模具 —Mold dimensions at thermoforming temperature;

[0018] α 模具 —Coefficient of linear expansion of mold;

[0019] ΔT—the difference between thermoforming temperature and room temperature;

[0020] L 零件0 —Dimensions of parts at room temperature;

[0021] L 零件 —Part dimensions at thermoforming temperature

[0022] α 零件 —Linear expansion coefficient of parts.

[0023] Furthermore, the large-diameter cylindrical section, the conical section and the small-diameter cylindrical section of the bulging tire core are an integrated structure.

[0024] Furthermore, in step (4), before heating the blank, the step of calculating the plastic deformation of the expanded end of the blank is also included, wherein the plastic deformation satisfies the formula Where, η is the plastic deformation of the expanded end of the preform, γ 锥2 is the radius of the flared end of the preform, γ 直2 It is the theoretical radius of the straight cone composite cylinder after expansion.

[0025] Furthermore, when the amount of plastic deformation is ≥8%, the blank is pre-expanded.

[0026] Furthermore, the deviation between the inner diameter of the blank and the outer diameter of the bulging tire core is controlled within 8%, thereby completing the pre-expansion of the blank.

[0027] Furthermore, step (4) also includes installing a clamping plate on the small diameter end face of the bulging tire core to prevent the blank from moving upward relative to the bulging tire core during the forming process.

[0028] Furthermore, in step (7), the demoulding includes adding a lubricant between the closing die and the part, and demoulding the part by pressing down on the upper surface of the part.

[0029] Furthermore, when the material of the straight-cone composite tube is TA15, the pressure of the die for closing the blank through the closing die is 20-80 tons.

[0030] In a second aspect, an embodiment of the present invention provides a mold used in the above method, wherein the mold includes a base, a bulging tire core, a clamping plate, a closing mold and a cushion ring;

[0031] The base is used to bear the weight of the mold and the blank and to position the bulging tire core;

[0032] The clamping plate is used to position the bulging tire core and the connecting lugs;

[0033] The bulging tire core is used for integrated forming of closing, bulging and expanding of the straight-cone composite tube;

[0034] The closing mold has a cylindrical inner cavity, which is used to cooperate with the bulging tire core to complete the closing of the part;

[0035] The cushion block ring is used to transmit external pressure to the closing die to achieve the closing of the blank.

[0036] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0037] 1 The method of the present invention can realize the one-piece forming process of closing, expanding and bulging of a straight-tapered composite tube; compared with the traditional preparation method of the existing straight-tapered composite tube, the method of the present invention simplifies the processing process of the straight-tapered composite tube, reduces the number of process steps from 3 to 1, and shortens the processing cycle by two-thirds; the number of tooling is reduced from 3 sets to 1 set, and the tooling components are saved by more than half; the closing, expanding and bulging processes can be realized by clamping once, which reduces the difficulty of operation, processing difficulty and cost; at the same time, it avoids the error accumulation phenomenon of multiple processes and improves the product surface accuracy.

[0038] 2. The method of the present invention designs the size of the mold according to the material and size of the part to be processed and the material of the mold, so that the mold can fully fit the part at the hot forming temperature to improve the product molding quality and reduce the product surface accuracy error; preferably, the present invention calculates the size of the mold used in the method of the present invention to realize the one-piece molding process of closing, expanding and bulging of the straight cone composite tube according to the linear expansion coefficient of the part and its size at room temperature, the linear expansion coefficient of the mold and the difference between the hot forming temperature and room temperature.

[0039] 3. The thermal expansion coefficient of the material constituting the bulging core in the method of the present invention is equal to or greater than the thermal expansion coefficient of the material of the straight-cone composite tube to be processed. Preferably, when the whole cone tube blank is hot-formed using a mold with a larger thermal expansion coefficient, not only a better forming effect is achieved, but also demolding is easy after forming and cooling; the material constituting the bulging core of the present invention can be stainless steel.

[0040] 4. In the method of the present invention, before the blank is formed, the inner diameter of the closing die mounted on the bulging tire core is smaller than the outer diameter of the end to be closed of the whole cone tube blank, so that the closing die is located in the conical section of the bulging tire core; during the blank forming, the closing die moves downward under the action of external pressure, and cooperates with the large-diameter cylindrical section of the bulging tire core to achieve the closing of the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube.

[0041] 5. The method of the present invention determines whether it is necessary to pre-expand the expanded end of the straight tapered tube blank to be processed according to the plastic deformation amount of the expanded end of the blank to ensure successful molding of the blank; wherein, when the plastic deformation amount of the expanded end of the blank is ≥8%, the blank is pre-expanded.

[0042] 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

[0043] 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.

[0044] Figure 1 It is a schematic diagram of mold assembly of the straight-taper composite tube integral molding method of the present invention;

[0045] Figure 2 Schematic diagram of the blank (a) and product (b) of the straight-cone composite tube 1 of Example 1 of the present invention;

[0046] Figure 3 Schematic diagram of the blank (a), pre-expanded blank (b) and product (c) of the straight-cone composite tube 2 of Example 2 of the present invention.

[0047] Reference numerals:

[0048] 1-base; 2-pressing plate; 3-bulging tire core; 4-closing die; 5-pad ring; 6-blank. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention 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.

[0050] Aerospace parts are becoming increasingly complex. Straight-cone composite titanium cylinders are widely used in aerospace vehicles as a typical component. Straight-cone composite titanium cylinders cannot be directly bulged due to their different diameter change rules. The traditional process includes three processes: closing bulging, expanding bulging, and overall bulging. They have the following disadvantages: the complex process leads to a long processing cycle; more tooling is required, resulting in high costs; processing is difficult, and bulging a product requires three hot bulging processes. Each hot bulging process requires mold clamping and positioning, which puts forward high requirements for reference transfer and operation processes; the product surface accuracy is poor, and there is a bulging error in each process of the traditional process. The accumulated errors of the three processes lead to a large surface accuracy error of the final product.

[0051] Therefore, the present invention discloses an integral molding method of a straight-cone composite cylinder, the method comprising:

[0052] (1) establishing a three-dimensional model of a straight-cone composite cylinder, and designing and manufacturing a mold, wherein the mold includes a bulging tire core and a closing mold, wherein the bulging tire core includes a conical section, and a large-diameter cylindrical section and a small-diameter cylindrical section respectively located at two ends;

[0053] (2) designing the size of the mold according to the linear expansion coefficient of the straight-tapered composite tube and its size at room temperature, the linear expansion coefficient of the mold component, and the difference between the hot forming temperature and room temperature;

[0054] (3) cutting, rounding and welding are performed according to the unfolded material size of the straight-cone composite cylinder three-dimensional model in the software to obtain a whole-cone cylinder blank;

[0055] (4) first fixing the large diameter end face of the bulging tire core, then preheating the whole cone blank, and sleeved the whole cone blank onto the bulging tire core from the large diameter end of the whole cone, wherein the preheating temperature is equal to the molding temperature;

[0056] (5) The closing die is mounted on the conical section of the bulging tire core to complete the assembly of the die;

[0057] (6) the mold is heated and maintained, and pressure is applied to the closing die through the heating device platform to move the closing die downward, and cooperate with the large-diameter cylindrical section of the bulging tire core to close the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube; in addition, at the molding temperature, the conical section and the small-diameter cylindrical section of the bulging tire core are bulged to form a conical tube section and a small-diameter straight tube section of the straight-cone composite tube, respectively;

[0058] (7) Cooling the mold and demoulding the mold to obtain the straight-cone composite tube.

[0059] Specifically, in the step (1), the mold designed by the three-dimensional model of the straight cone composite tube has the same shape as the straight cone composite tube. The structure of the straight cone composite tube in the present invention includes a conical section, a large diameter cylindrical section located at the large diameter end of the conical section, and a small diameter cylindrical section located at the small diameter end of the conical section. Correspondingly, the bulging tire core includes a conical section, and a large diameter cylindrical section and a small diameter cylindrical section located at both ends, which are solid or hollow, so as to complete the process of closing, expanding and bulging the straight cone composite tube in one step. Compared with the traditional preparation method, the process steps are simplified and the processing cycle is shortened.

[0060] Furthermore, the large-diameter cylindrical section, the conical section and the small-diameter cylindrical section of the bulging tire core are an integrated structure.

[0061] The method of the present invention designs the size of the mold according to the material and size of the part to be processed and the material of the mold, so that the mold is completely fitted with the part at the hot forming temperature, so as to improve the product molding quality and reduce the product surface precision error.

[0062] Specifically, in step (2), the size of the mold is designed based on the linear expansion coefficient of the straight-tapered composite tube and its size at room temperature, the linear expansion coefficient of the mold component, and the difference between the hot forming temperature and room temperature.

[0063] Furthermore, at the thermoforming temperature, the mold and the part are completely fitted, that is, L 零件 =L 模具, the size of the mold at room temperature meets:

[0064] L 模具0 = L 零件0 *(1+α 零件 ·ΔT) / (1+α 模具 ·ΔT) (1)

[0065] Among them, L 模具0 —Mold dimensions at room temperature;

[0066] L 模具 — Mould dimensions at thermoforming temperature;

[0067] α 模具 —Coefficient of linear expansion of mold;

[0068] ΔT—the difference between thermoforming temperature and room temperature;

[0069] L 零件0 —Part dimensions at room temperature;

[0070] L 零件 —Part dimensions at thermoforming temperature

[0071] α 零件 —Linear expansion coefficient of parts.

[0072] The present invention designs the structure and size of the mold bulging core and the closing mold to ensure the stability and adaptability of the parts during hot processing. The design principle is:

[0073] Assume that the part is formed at a certain temperature T and the part fits the mold perfectly, that is, R 胎芯 =r 零件 , R 零件 =r 收口模 , where the following relationship exists:

[0074] R 零件 =R 零件0 (1+α 零件 ·ΔT) (2)

[0075] r 零件 =r 零件0 (1+α 零件 ·ΔT) (3)

[0076] R 胎芯 =R 胎芯0 (1+α 胎芯 ·ΔT) (4)

[0077] r 收口模 =r 收口模0 (1+α 收口模 ·ΔT) (5)

[0078] In the formula, R 零件0 —Outer diameter of the straight-cone composite cylinder at room temperature;

[0079] r 零件0 —Inner diameter of the straight-cone composite cylinder at room temperature;

[0080] R 零件 —Outer diameter of the straight-cone composite tube at the hot forming temperature;

[0081] r 零件 —Inner diameter of the straight-cone composite tube at the hot forming temperature;

[0082] R 胎芯0 —Outer diameter of the tire core at room temperature;

[0083] R 胎芯 —Outer diameter of the tire core at the hot forming temperature;

[0084] r 收口模0 —Inner diameter of the closing die at room temperature;

[0085] r 收口模 —Inner diameter of the closing die at the thermoforming temperature;

[0086] α 零件 —Part linear expansion coefficient;

[0087] α 胎芯 —Tire core linear expansion coefficient;

[0088] α 收口模 —Coefficient of linear expansion of the closing die;

[0089] ΔT—The difference between hot forming temperature and room temperature.

[0090] From formula (1)-(4), we can get:

[0091] R 胎芯0 = r 零件0 *(1+α 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (6)

[0092] r 收口模0 = R 零件0 *(1+α 零件 ·ΔT) / (1+α 收口模 ·ΔT) (7)

[0093] Therefore, the scaled size of the process parts is as shown in formulas (6) and (7), that is, when designing the mold, the size of the bulging tire core and the closing mold needs to be enlarged or reduced; by accurately controlling the mold size, the part molding quality is further improved and the precision error is reduced.

[0094] Specifically, in step (3), the three-dimensional model of the straight-cone composite cylinder is unfolded to accurately calculate the unfolded material size. The specific method is as follows: in the UG software, a new plane is created in the modeling module, the product model is divided into two parts, and then one of the cut edges is selected for offset, and the left and right sides of the cut edge are offset by 0.1mm, so that there is a 0.2mm gap on this edge; then the split models are summed to obtain a solid. The sheet metal unfolding operation is performed on the solid, and after unfolding, each side is offset by 0.1mm, and the theoretical model unfolding size can be obtained.

[0095] Furthermore, the material is cut according to the size of the unfolded material, and the cutting method can be laser cutting, wire cutting, CNC punching, shearing machine, water jet cutting, machining cutting and the like; according to a preferred embodiment of the present invention, laser cutting is used for cutting; the blank is circled to ensure that the end faces on both sides of the weld can be flush with each other; the circled product is pickled to clean the oil stains and excess materials on the surface of the blank; the blank is welded, and the welded part is a whole cone with an irregular surface.

[0096] Furthermore, the material of the straight-cone composite cylinder of the present invention is TA15, TC4 or aluminum alloy.

[0097] The thermal expansion coefficient of the bulging core material in the method of the present invention is equal to or greater than the thermal expansion coefficient of the straight-cone composite tube material to be processed. Preferably, when the whole cone tube blank is hot-formed using a mold with a larger thermal expansion coefficient, not only a better forming effect is achieved, but also the mold is easy to demold after cooling after forming; the material of the bulging core of the present invention can be selected from one of stainless steel, carbon steel, forging die steel, medium silicon-molybdenum ductile iron, heat-resistant alloy steel, and ceramic materials.

[0098] The material of the closing die of the present invention is one of stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, and ceramic material. When the thermal expansion coefficient of the closing die material is less than the thermal expansion coefficient of the prepared part, it is easy to demould after molding and cooling; when the thermal expansion coefficient of the closing die material is greater than or equal to the thermal expansion coefficient of the prepared part, it is not easy to demould after molding and cooling, and it is necessary to use lubricating oil and apply pressure for demoulding. The specific operation is discussed later.

[0099] The size and quality of the whole cone blank obtained by step (3), such as flatness, do not meet the requirements of practical application, and it is necessary to use a mold to perform expansion, closing and bulging heat treatment; the assembly diagram of the method of the present invention using a mold to perform part hot forming is as shown in Figure 1 As shown; the working principle is:

[0100] The first aspect: by selecting materials with different thermal expansion coefficients, the roundness of the product can be adjusted; a material with a larger thermal expansion coefficient than the blank material can be selected as the mold core material, and a blank whose room temperature diameter is larger than the room temperature core diameter, or a blank whose diameter after heating is larger than the room temperature core diameter, is installed on the core. After heating to a certain temperature T, the core diameter is larger than the product diameter, thereby achieving a bulging effect.

[0101] According to some preferred embodiments of the present invention, the material of the blank tapered tube is TA15 titanium alloy, and the thermal expansion coefficient at a temperature of (20-800)°C is: 9.7×10 -6 / ℃, the core material is 316 stainless steel, the thermal expansion coefficient at (20~800)℃ is about: 16.5×10 -6 / ℃, it is designed that the outer diameter of the tire core reaches the theoretical inner diameter of the straight-cone composite tube when heated to 700℃, and the diameter of the blank is larger than the diameter of the tire core at room temperature.

[0102] Second aspect: the blank is a conical tube, and the large diameter end of the conical tube needs to be closed to a straight tube. The working principle of closing is: after the blank is assembled on the tire core, the closing die is installed. The steps are as follows: Figure 1 As shown; when the inner diameter of the closing die is designed to be heated to the target temperature, it is the theoretical outer diameter of the product straight-cone composite tube. The blank is a whole cone, and the closing die cannot be directly installed to the bottom. It needs to be heated after the installation is completed as shown in the figure. After heating to the target temperature T, the upper platform of the equipment transmits pressure to the closing die through the holding ring, and the closing die moves downward until the closing die and the base are fully in contact; this process is the closing process.

[0103] The third aspect: the blank is a conical tube, and the small diameter end of the conical tube needs to be expanded into a straight tube. The maximum expansion range is determined by: the difference between the circumference of the neutral layer of the product and the circumference of the neutral layer of the blank and the ratio of the circumference of the neutral layer of the blank is within the range of the material elongation after fracture, that is: (circumference of the neutral layer of the product - circumference of the neutral layer of the blank) / circumference of the neutral layer of the blank ≤ elongation after fracture of the material. For example: the elongation after fracture of the material is 10%, then Where l2 is the circumference of the neutral layer of the product, and l1 is the circumference of the neutral layer of the blank.

[0104] Specifically, in step (4), the large diameter end face of the bulging tire core is first fixed, and then the whole cone blank is preheated and sleeved on the bulging tire core from the large diameter end of the whole cone, wherein the preheating temperature is equal to the molding temperature.

[0105] According to some preferred embodiments of the present invention, the present invention fixes the large diameter end face of the bulging tire core to the base through a threaded connection; the base has a disc-shaped or annular structure, wherein, for a hollow bulging tire core, the annular structure of the base is conducive to heat transfer, thereby improving the heat utilization rate and uniformity during the hot processing of the blank; the inner ring circumference of the upper surface of the annular base has an annular protrusion, the outer diameter of the annular protrusion is smaller than the inner diameter of the large diameter end of the hollow bulging tire core, and is used to position the large diameter end of the bulging tire core.

[0106] Furthermore, before heating the blank, the step of calculating the plastic deformation of the expanded end of the blank is included, wherein the plastic deformation satisfies the formula Where, η is the plastic deformation of the expanded end of the preform, γ 锥2 is the radius of the flared end of the preform, γ 直2 It is the theoretical radius of the straight cone composite cylinder after expansion.

[0107] According to some preferred embodiments of the present invention, when the plastic deformation is ≥8%, if the blank is directly mounted on the tire inflation mold, it is difficult to mount the mold due to the small diameter of the blank and the large diameter of the inflation tire core, and the flared end needs to be pre-flared.

[0108] The specific steps of the pre-expansion are: using a conventional expansion method to pre-expanse a small diameter section of a certain length of the full cone blank. The pre-expansion can be completed in three ways, namely:

[0109] The first method uses calculus to pre-expand a small-diameter conical segment into a cylinder. First, a cylindrical segment 1 is used for pre-expansion, wherein the diameter of the cylindrical segment 1 is half the sum of the outer diameter of the expanded end of the bulging tire core and the inner diameter of the small end of the billet cone, and the length of the cylindrical segment 1 is ≥ the length of the straight tube segment of the theoretical model. The cylindrical segment 1 is loaded into the billet at room temperature, and then the billet is heated to perform the first step of pre-expansion; if the deviation between the inner diameter of the billet after pre-expansion and the outer diameter of the bulging tire core is within 8%, the pre-expansion is completed; if the inner diameter of the billet after pre-expansion is within 8% of the outer diameter of the bulging tire core, the pre-expansion is completed; if the inner diameter of the billet after pre-expansion is within 8% of the outer diameter of the bulging tire core, the pre-expansion is completed. If the deviation of the outer diameter of the tire core is more than 8%, the cylindrical section 2 is continued to be pre-expanded, and the diameter of the cylindrical section 2 is half of the sum of the outer diameter of the expanded end of the expanded tire core and the inner diameter of the blank after the first step of pre-expanding, and the second pre-expanding is performed; and so on, until the deviation of the inner diameter of the blank and the outer diameter of the expanded tire core is within 8%, thereby completing the pre-expansion of the blank; then the preformed blank is heated or not heated, and the pre-expanded blank is installed on the expanded tire core, and it is ensured that the bottom of the blank contacts the base; then the clamping plate is installed at the small diameter end of the expanded tire core;

[0110] The second method is to process a stainless steel straight column with a diameter equal to the end diameter of the blank, place the pre-expanded cylinder into the blank at room temperature, and then heat and pre-expand it. After cooling, this step of expansion is repeated until the deviation between the blank diameter and the expansion core diameter is within 8%.

[0111] The third method is to process a conical column with a diameter equal to the inner diameter of the small end of the blank. The conical column is placed in the blank at room temperature, and then heated and pre-expanded. After cooling, this step is repeated for iterative pre-expansion until the deviation between the blank diameter and the bulging tire core diameter is within 8%.

[0112] When the plastic deformation is less than 8%, there is no need to pre-expand the whole cone blank, and it can be expanded directly, that is, the blank is directly heated or not heated, and installed on the bulging tire core, and ensure that the bottom of the blank contacts the base; then the clamping plate is installed at the small diameter end of the bulging tire core.

[0113] It should be noted that the present invention heats the straight cone cylinder preform to cause thermal expansion of the straight cone cylinder preform so that it can be sleeved and installed on the bulging tire core to achieve small active tire and large tire, thereby improving the bulging quality of the product.

[0114] It should be noted that the temperature at which the blank is heated before being installed should be lower than the melting point of the blank so as not to change the microstructure of the blank. The preferred heating temperature is the temperature at which the blank is subjected to heat treatment.

[0115] Furthermore, step (4) also includes installing a clamping plate on the small diameter end face of the bulging tire core to prevent the blank from moving upward relative to the bulging tire core during the forming process, wherein the diameter of the clamping plate is larger than the diameter of the small diameter end face of the bulging tire core.

[0116] Specifically, in step (5), the closing mold is mounted on the conical section of the bulging tire core to complete the assembly of the mold.

[0117] According to some preferred embodiments of the present invention, the mold in the method of the present invention also includes a cushion block ring, which is mounted on the bulging tire core and the closing mold, and is used to transmit external pressure to the closing mold to achieve the closing of the blank. The height after mounting is much greater than the height of the bulging tire core, which is convenient for external pressure.

[0118] It should be noted that according to some preferred embodiments of the present invention, when the material of the straight-cone composite tube is TA15, the total weight of the closing die and the holding ring is 150-200Kg, the pressure of closing the blank by the closing die is 20-80 tons, and when the inner diameter of the closing die at the hot processing temperature is equal to the theoretical outer diameter of the large-diameter tube of the straight-cone composite tube, when the closing die and the holding ring are successively put on the bulging tire core, the closing die will not reach the bottom of the bulging tire core and contact the base.

[0119] It should be noted that, in the method of the present invention, before the blank is formed, the inner diameter of the closing die mounted on the bulging tire core is smaller than the outer diameter of the end to be closed of the whole cone tube blank, so that the closing die is located in the conical section of the bulging tire core; during the forming of the blank, the closing die moves downward under the action of external pressure, and cooperates with the large-diameter cylindrical section of the bulging tire core to achieve the closing of the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube.

[0120] Specifically, in step (6), the mold is heated and maintained, and pressure is applied to the closing die through the heating device platform to move the closing die downward, cooperating with the large diameter cylindrical section of the bulging tire core to achieve the closing of the blank, thereby forming a large diameter straight tube section of the straight cone composite tube; in addition, at the molding temperature, the conical section and the small diameter cylindrical section of the bulging tire core are bulged to form a conical tube section and a small diameter straight tube section of the straight cone composite tube, respectively.

[0121] According to some specific embodiments of the present invention, the mold is heated to the heat treatment processing temperature of the straight cone composite tube, and then pressure is applied to the mold by controlling the upper and lower platforms, and the cushion ring and the closing mold part move downward until the closing mold and the base are in contact. After the closing mold and the base are in contact, they are kept warm for a period of time to ensure that the hot processing is in place.

[0122] According to a preferred embodiment of the present invention, a straight-cone composite cylinder preform made of TA15 titanium alloy is heated to 600-700°C; then the mold applies a pressure of 20-80 tons, and the ring and the closing mold part move downward until the closing mold contacts the base. After the closing mold contacts the base, the heat and pressure are maintained for 1-5 hours.

[0123] Specifically, in step (7), after the blank is subjected to heat treatment, the equipment is naturally cooled, and the mold is removed from the equipment and demoulded.

[0124] According to some preferred embodiments of the present invention, the cushion block ring, the clamping plate, the base, and the bulging tire core are first disassembled, and then the closing mold is disassembled.

[0125] It should be noted that when the thermal expansion coefficient of the material constituting the bulging tire core is greater than the thermal expansion coefficient of the straight-cone composite tube material, a gap is formed between the bulging tire core and the straight-cone composite tube after the straight-cone composite tube is cooled, so the bulging tire core is easily disassembled.

[0126] It should be noted that when the thermal expansion coefficient of the closing die is smaller than that of the straight-cone composite tube, it can be demolded directly after cooling; when the thermal expansion coefficient of the closing die is larger than that of the straight-cone composite tube, it cannot be demolded directly after cooling, and lubricant needs to be added between the closing die and the heat-treated parts, and left for a period of time, at least 20 minutes, and then the closing die and parts are placed on the press platform, the clamping plate is placed on the upper end face of the part, and the upper plane of the part is slowly pressed down by controlling the upper platform of the equipment (speed ≤5mm / s) to demold the part.

[0127] The present invention realizes zero-angle demolding of the straight-cone composite tube, thus broadening the boundaries of the product structure of the hot forming process.

[0128] The method disclosed in this invention can realize the one-piece forming process of closing, expanding and bulging of a straight-taper composite tube through one process. Compared with the traditional preparation method of the existing straight-taper composite tube, the number of process steps is reduced from 3 to 1, shortening the processing cycle by two-thirds; the number of tooling is reduced from 3 sets to 1 set, saving more than half of the tooling components; the closing, expanding and bulging processes can be realized by clamping once, reducing the difficulty of operation, reducing the difficulty and cost of processing; at the same time, it avoids the error accumulation phenomenon of multiple processes and improves the product surface accuracy.

[0129] The present invention also provides a mold for integrally forming a straight-tapered composite cylinder, such as Figure 1 As shown, the mold includes a base 1, a bulging tire core 3, a clamping plate 2, and a closing mold 4 and a cushion ring 5 which are rigidly connected from bottom to top, and are sleeved on the bulging tire core from bottom to top.

[0130] The bulging tire core includes a conical section located in the middle, and a large-diameter cylindrical section and a small-diameter cylindrical section located at both ends, respectively. The conical section is used for bulging the blank to form a conical section of the straight-cone composite tube; the small-diameter cylindrical section is used for expanding the blank to form a small-diameter straight section of the straight-cone composite tube; the large-diameter cylindrical section is used for closing the blank to form a large-diameter straight section of the straight-cone composite tube, wherein the blank is a full-cone blank;

[0131] The closing mold has a cylindrical inner cavity, which is sleeved on the bulging tire core and is used to cooperate with the large-diameter cylindrical section of the bulging tire core to achieve the closing of the blank and form a large-diameter straight tube section of the straight-cone composite tube;

[0132] The pad ring includes an upper bottom ring surface, a lower bottom ring surface and a support column located in the middle, which is used to transmit external pressure to the closing die to achieve the closing of the blank.

[0133] The bulging tire core of the present invention includes a conical section located in the middle, and a large-diameter cylindrical section and a small-diameter cylindrical section located at both ends respectively. In addition to supporting the blank and controlling the shape of the product, it is mainly used to realize the integrated forming process of closing, expanding and bulging of the straight-cone composite tube parts; the base is used to bear the weight of the mold and position the bulging tire core; the clamping plate and the base are used together to fix the bulging tire core; the closing mold is used to cooperate with the large-diameter cylindrical section of the bulging tire core to realize the closing of the blank; the cushion block ring is used to transmit the pressure applied by the outside to the closing mold.

[0134] Specifically, the size of the bulging tire core at room temperature of the present invention satisfies:

[0135] R 胎芯0 = r 零件0 *(1+α 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (6)

[0136] Among them, R 胎芯0 —Outer diameter of the bulging tire core at room temperature;

[0137] α 胎芯 —Bulging tire core linear expansion coefficient;

[0138] ΔT—the difference between thermoforming temperature and room temperature;

[0139] r 零件0 —Inner diameter of the straight-cone composite cylinder at room temperature;

[0140] α 零件 —Linear expansion coefficient of straight-cone composite tube.

[0141] Specifically, the structure and size of the bulging core are determined by the structure and size of the straight-cone composite tube part to be produced. In order to ensure the stability and adaptability of the part during hot working, the design principle of the bulging core is:

[0142] Assuming that the part is formed at a certain temperature T, the straight-cone composite tube part is completely fitted with the bulging tire core, and the inner diameter r of the part 零件 Equal to the outer diameter R of the bulging tire core 胎芯 , that is, R 胎芯 =r 零件 , among which, there are the following relations:

[0143] r 零件 =r 零件0 (1+α 零件 ·ΔT) (3)

[0144] R 胎芯 =R 胎芯0 (1+α 胎芯 ·ΔT) (4)

[0145] Among them, r 零件0 —Inner diameter of the straight-cone composite cylinder at room temperature, R 胎芯 —The outer diameter of the bulging tire core at the hot forming temperature; and the outer diameter of the bulging tire core at room temperature is derived from the above relationship.

[0146] Specifically, the lengths of the cylindrical section and the conical section of the bulging tire core and the diameters of each section are determined by the size of the straight-cone composite tube to be processed. The length of the conical section is equal to the length of the conical section in the straight-cone composite tube to be processed. The length of the cylindrical section is 20-50 mm longer than the length of the straight section in the straight-cone composite tube to be processed. It is used for finishing the excess removal of the rough product after the hot processing is completed and removing the uneven parts at both ends. The outer diameters of each section of the bulging tire core are calculated by formula (6).

[0147] In addition, the thickness of the bulging core of the present invention is based on the pressure and temperature during the thermal processing to ensure the strength and stability of the bulging tire. The appropriate thickness range of the bulging core is beneficial to the expansion performance of the bulging tire and the convenience of demoulding.

[0148] The bulging tire core is a solid or hollow structure, preferably a hollow structure, which is conducive to the conduction and heat dissipation of heat, avoids deformation or damage due to overheating, helps to maintain the processing accuracy and stability of parts, and is convenient to move and operate, improves efficiency, and reduces costs.

[0149] Specifically, the present invention connects the large diameter end of the bulging tire core to the base threadedly, and the small diameter end to the clamping plate threadedly; preferably, the large diameter end of the bulging tire core with a hollow structure can be sleeved on the periphery of the annular protrusion of the base, and the small diameter end can be sleeved on the periphery of the cylindrical protrusion of the clamping plate.

[0150] Furthermore, built-in threaded holes are symmetrically distributed along the circumference on the large diameter end face of the bulging tire core, and the number of the built-in threaded holes is the same as the corresponding threaded holes on the base, which is 4-6, and the large diameter end of the bulging tire core is fixed to the base by bolts; built-in threaded holes are symmetrically distributed along the circumference on the small diameter end of the bulging tire core, and the number of the built-in threaded holes is the same as the corresponding threaded holes on the clamping plate, which is 4-6, and the small diameter end of the bulging tire core is fixed to the clamping plate by bolts.

[0151] Furthermore, in order to ensure that the bulging core has sufficient strength and rigidity and facilitates heat conduction and heat dissipation, the material of the bulging core can be selected from one of stainless steel, carbon steel, forging steel, medium silicon-molybdenum ductile iron, heat-resistant alloy steel, and ceramic materials.

[0152] Specifically, the thermal expansion coefficient of the bulging core material of the present invention is greater than the thermal expansion coefficient of the blank to be processed. When the whole cone blank is hot-formed using a mold with a larger thermal expansion coefficient, not only a better forming effect is achieved, but also demolding is easy after forming and cooling.

[0153] According to some preferred embodiments of the present invention, when hot processing a TA15 titanium alloy straight-cone composite cylinder, 316 stainless steel having a thermal expansion coefficient greater than that of the TA15 titanium alloy can be selected to prepare the bulging tire core.

[0154] The material of other parts of the present invention is one of stainless steel, carbon steel, forging die steel, medium silicon-molybdenum ductile iron and heat-resistant alloy steel.

[0155] According to the shape of the straight-cone composite tube to be prepared, the inner cavity of the closing die is designed to be cylindrical, which is used for the closing molding of the straight-cone composite tube. The size of the closing die at room temperature of the present invention satisfies:

[0156] r 收口模0 = R 零件0 *(1+α 零件 ·ΔT) / (1+α 收口模 ·ΔT) (7)

[0157] Among them, r 收口模0 —Inner diameter of the closing die at room temperature;

[0158] α 收口模 —Coefficient of linear expansion of the closing die;

[0159] ΔT—the difference between thermoforming temperature and room temperature;

[0160] R 零件0 —Outer diameter of the straight-cone composite cylinder at room temperature;

[0161] α 零件 —Linear expansion coefficient of straight-cone composite tube.

[0162] Specifically, the structure and size of the closing die are determined by the structure and size of the straight-cone composite tube part to be produced. In order to ensure the stability and adaptability of the part during hot working, the design principle of the closing die is:

[0163] Assuming that the part is formed at a certain temperature T, the straight-cone composite tube part is completely fitted with the closing die, and the outer diameter L of the part 零件 Equal to the inner diameter R of the closing die 收口模 , that is, L 零件 =R 收口模 , among which, there are the following relations:

[0164] R 零件 =R 零件0 (1+α 零件·ΔT) (2)

[0165] r 收口模 =r 收口模0 (1+α 收口模 ·ΔT) (5)

[0166] Among them, R 收口模 —Inner diameter of the closing die at the hot forming temperature, r 收口模 —The inner diameter of the closing die at the thermoforming temperature; and the inner diameter of the closing die at room temperature is derived from the above relationship.

[0167] Specifically, the length of the closing die is greater than or equal to the length of the hollow cylindrical section at the large diameter end of the bulging tire core, and under the part molding temperature, it cooperates with the large diameter cylindrical section of the bulging tire core to achieve the closing of the blank.

[0168] According to the present invention, before the blank is formed, the inner diameter of the closing die mounted on the bulging tire core is smaller than the outer diameter of the end to be closed of the whole cone tube blank, so that the closing die does not contact the base; during the blank forming, the closing die moves downward under the action of external pressure, contacts the base, and cooperates with the large-diameter cylindrical section of the bulging tire core to achieve the closing of the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube.

[0169] According to some preferred embodiments of the present invention, the end of the closing die in contact with the block ring is designed to be a circular ring structure, the outer diameter of which is larger than the outer diameter of other parts of the closing die, and is used to withstand the external pressure transmitted by the block ring, and the other parts of the closing die are cylindrical; the structure of the straight cone composite cylinder in the present invention is convenient to move and operate, improves efficiency, and reduces material costs.

[0170] Furthermore, the straight cylindrical part of the closing mold is symmetrically provided with threaded through holes, which are used for installing lifting ears when the mold is assembled, and installing electric couples during hot processing; the circular ring part of the closing mold is symmetrically provided with threaded built-in holes, which are used for installing lifting ears when the mold is assembled, and fixing it with the pad ring through bolts during hot processing.

[0171] Furthermore, the closing die needs to have high strength to withstand an external pressure of 20-80 tons, improve durability, and ensure thermal processing accuracy; in addition, the selection of the closing die material should also be determined by considering the material characteristics of the parts to be processed and the working environment.

[0172] Specifically, the material of the closing die is one of stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, and ceramic material. When the thermal expansion coefficient of the closing die material is less than the thermal expansion coefficient of the prepared part, it is easy to demould after molding and cooling; when the thermal expansion coefficient of the closing die material is greater than or equal to the thermal expansion coefficient of the prepared part, it is not easy to demould after molding and cooling, and it is necessary to use lubricating oil and apply pressure for demoulding. The specific operation is discussed later.

[0173] The present invention utilizes the base as a positioning standard for the bulging tire core, and is used together with the clamping plate to fix the bulging tire core.

[0174] Specifically, the base is used to bear the weight of the mold and the blank and the external pressure, and needs to have a certain thickness and strength. The thickness range is determined by the material constituting the base, the material and size of the blank that needs heat treatment. For example, when 304 stainless steel is used to prepare the TA15 titanium alloy straight cone composite cylinder of the embodiment, the thickness of the base can be 10-30mm; the base has a disc-shaped or annular structure, wherein the annular structure is conducive to heat transfer, and improves the heat utilization rate and uniformity during the hot processing of the blank; the inner ring circumference of the upper surface of the annular base has an annular protrusion with a protrusion height of 5-30m, and the outer diameter of the annular protrusion is less than or equal to the inner diameter of the large diameter end of the hollow bulging tire core, which is used to position the large diameter end of the bulging tire core.

[0175] It should be noted that the thickness of a certain annular area on the outer edge of the base becomes thinner in order to fix it to the parts heat treatment equipment when installing the mold. It is preferably fixed with a pressing plate to control the thickness of the annular area to 10-30mm.

[0176] Furthermore, the base has threaded through holes I evenly distributed along a certain circumference, the diameter of the circumference matches the size of the large diameter end of the bulging tire core, and is used to threadedly fix the bulging tire core, and the number is 4-6; in addition, in order to facilitate the assembly of the mold and accurately control the heating temperature during the hot working process, threaded through holes II are provided on the periphery of the through holes I of the base, and the number is 4-6, which are used to install lifting ears during mold assembly and to install electric couples during hot working.

[0177] Specifically, the clamping plate has a disc-shaped structure, and is used together with the base to fix the bulging tire core. The clamping plate is connected to the tire core by bolts, which can prevent the blank from moving upward relative to the tire core during the forming process.

[0178] Preferably, the central area of ​​the lower surface of the clamping plate has a cylindrical protrusion with a protrusion height of 10-20 mm, and the diameter of the cylindrical protrusion is less than or equal to the inner diameter of the small diameter end of the hollow bulging tire core to position the small diameter end of the bulging tire core.

[0179] Furthermore, the clamping plate is threadedly connected to the bulging tire core. Specifically, the base is provided with threaded through holes A evenly distributed along a certain circumference, and the diameter of the circumference matches the size of the small diameter end of the bulging tire core, which are used to threadably fix the bulging tire core, and the number is 4-6; further, in order to facilitate the disassembly and assembly of the clamping plate, the hole through which the clamping plate and the bulging tire core are threadedly connected can be designed as a special-shaped hole; the special-shaped hole includes two connected circular holes, and the diameters of the two circular holes are different, namely a large diameter hole and a small diameter hole. During normal use, the bolts are not removed, the clamping plate is removed, and the nut passes through the large diameter hole when the clamping plate is installed. After installation, the nut is turned to the small diameter hole to play a positioning role.

[0180] In addition, a lifting lug is threadedly connected at the center of the upper surface of the clamping plate to facilitate the loading and unloading of the mold.

[0181] Specifically, the block ring includes an upper bottom ring surface, a lower bottom ring surface and a support column located in the middle, which is used to transmit external pressure to the closing die to achieve the closing of the blank; before the straight cone composite tube is formed, the closing die and the block ring are mounted on the bulging tire core from bottom to top, and the block ring is on the closing die, and the two are threadedly connected, wherein the closing die is not in contact with the base; at the blank forming temperature, pressure is applied to the upper surface ring surface of the block ring through the heating device platform, and the pressure is transmitted to the closing die through the block ring, and the closing die moves downward under the action of external pressure, contacts the base, and cooperates with the large diameter cylindrical section of the bulging tire core to achieve the closing of the blank, forming the large diameter straight tube section of the straight cone composite tube.

[0182] According to some preferred embodiments of the present invention, the upper and lower bottom surfaces of the cushion ring are circular ring structures of the same size, the diameter of the middle hollow circle is equal to the diameter of the cylindrical inner cavity of the closing die, and the outer diameter is greater than or equal to the outer diameter of the circular ring portion of the closing die. The closing die needs to have a high strength to withstand an external pressure of 20-80 tons, improve durability, and ensure thermal processing accuracy.

[0183] Furthermore, threaded through holes are provided on the upper and lower bottom surfaces of the cushion block ring, and the support column is a cylinder with threads at both ends. After being connected to the lower bottom surface, the support column can pass through the lower bottom surface and be fixed by a nut under the lower bottom surface; after being connected to the upper bottom surface, the support column cannot pass through the upper bottom surface and is fixed by a nut inside the upper bottom surface so as to apply pressure to the upper bottom surface of the cushion block ring.

[0184] Furthermore, in order to ensure the stability of the mold under the action of external forces during the hot working of the parts, the outer diameter of the base is greater than or equal to the diameter of the bottom surface of the cushion ring.

[0185] The magnification coefficient of the mold of the present invention is 3-6‰, which is conducive to the installation of the thermally expanded blank on the bulging tire core on the one hand, and can ensure the dimensional accuracy of the thermoformed product and avoid molding defects, thereby achieving small live tires and large tires, and improving product molding quality.

[0186] According to some preferred embodiments of the present invention, when preparing a TA15 titanium alloy straight-cone composite cylinder, the material of the bulging tire core is 316 stainless steel, and the material of other parts of the mold is 304 stainless steel.

[0187] The mold of the present invention is prepared by casting and machining methods.

[0188] Mold: The bulging core material is 316 stainless steel, and the thermal expansion coefficient at (20~800)℃ is about 16.5×10 -6 / ℃; the expansion coefficient is the other parts of the mold material is 304 stainless steel, the thermal expansion coefficient at (20~800)℃ is about 18.2×10 -6 / ℃.

[0189] Example 1

[0190] A method for preparing a TA15 titanium alloy straight-cone composite cylinder 1, wherein the dimensions of the TA15 titanium alloy straight-cone composite cylinder 1 are: a thickness of 2 mm, a total length of 1420 mm, a top end of a cylinder of 40 mm in length and 288 mm in outer diameter, a bottom end of a cylinder of 40 mm in length and 400 mm in outer diameter, and a cone in the middle, such as Figure 2 (b), the method comprises:

[0191] (1) A three-dimensional model of a TA15 titanium alloy straight-cone composite cylinder is established by UG, and a mold 1 is designed based on the three-dimensional model. The mold 1 is manufactured by conventional means. The mold 1 includes a base, a bulging tire core, a clamping plate, a closing mold, and a cushion ring. The structure is as follows Figure 1 As shown;

[0192] (2) After calculation, the outer diameter of the large diameter cylindrical section of the bulging tire core is 389.6 mm, the outer diameter of the small diameter cylindrical section of the bulging tire core is 278.3 mm; the inner diameter of the closing die is 398.2 mm;

[0193] (3) Expand the three-dimensional model in step (1) and calculate the size of the expanded material; cut the TA15 titanium alloy by laser cutting; flush the end faces on both sides of the weld and perform a rounding operation; pickle the rounded blank to clean the oil stains and excess materials on the surface of the blank; weld the blank to obtain a whole cone blank with an irregular profile, i.e., a TA15 titanium alloy straight cone composite cylinder 1 preform blank, such as Figure 2 (a)

[0194] (4) According to calculation, the plastic deformation of the expanded end of the blank is 1.6%. The large diameter end face of the bulging tire core is firstly threadedly connected with the base 1, and the preform obtained in step (3) is directly heated at 680° C. for 2 h. The blank is sleeved on the bulging tire core through the large diameter end of the full cone barrel blank, so that the bottom of the preform blank contacts the base of the mold, and a clamping plate is installed on the small diameter end of the bulging tire core;

[0195] (5) First, the closing die is mounted on the conical section of the bulging tire core, and then the cushion ring is mounted on the bulging tire core and on the closing die, and the two are threadedly connected to complete the assembly of the mold, wherein the distance between the closing die and the base is 40 mm;

[0196] (6) Install the assembled mold on the platform of the heat treatment equipment, ensure that the closing die and the holding ring are perpendicular to the base, raise the temperature to 700°C, apply a pressure of 40 tons to the mold through the upper and lower platforms of the equipment until the closing die contacts the base, and continue to keep the temperature and pressure for 2 hours;

[0197] (7) The equipment is cooled to 20°C by natural air cooling, the mold is taken out, and the cushion ring, clamping plate, base and bulging tire core are disassembled; lubricant is added to the middle of the closing die and the part, and left for 20 minutes, the closing die and the part are placed on the press platform, and the clamping plate is placed on the upper end surface of the part. The upper plane of the part is pressed down at a speed of 2 mm / s by controlling the upper platform of the equipment, and the mold is demolded to obtain a TA15 titanium alloy straight cone composite cylinder 1.

[0198] Example 2

[0199] The method for preparing a TA15 titanium alloy straight-cone composite cylinder 2, the dimensions of the TA15 titanium alloy straight-cone composite cylinder 2 are as follows: the thickness is 2 mm, the total length is 1200 mm, the top end is a cylinder with a length of 100 mm and an outer diameter of 102 mm, the bottom end is a cylinder with a length of 100 mm and an outer diameter of 202 mm, and the middle is a cone, such as Figure 3 (c), the method comprises:

[0200] (1) Same as step (1) in Example 2;

[0201] (2) After calculation, the outer diameter of the large diameter cylindrical section of the bulging tire core is 201.2 mm, the outer diameter of the small diameter cylindrical section of the bulging tire core is 101.6 mm; the inner diameter of the closing die is 211.1 mm;

[0202] (3) The same as step (3) in Example 2, the TA15 titanium alloy straight cone composite tube 2 preform blank is obtained as Figure 3 (a)

[0203] (4) According to calculation, the plastic deformation of the expanded end of the billet is 10.8%, and the expanded end of the billet needs to be pre-expanded. Figure 3 (b)

[0204] (5) Same as step (5) in Example 2;

[0205] (6) Same as step (6) in Example 2;

[0206] (7) Same as step (7) in Example 2;

[0207] A TA15 titanium alloy straight-cone composite cylinder 2 is obtained.

[0208] A three-dimensional scan was performed on the straight-cone composite tube product obtained by the embodiment of the present invention. The results showed that the straight-cone composite tube obtained by the scheme of the present invention matched the theoretical model by 98%, and the product surface dimensional accuracy was within ±0.2mm. The straight-cone composite product obtained by the traditional processing method was tested by the same three-dimensional scanning method. The results showed that the straight-cone composite product obtained by the traditional processing method matched the theoretical model by only 75%, and the product surface dimensional accuracy was within ±2mm. It can be seen from the mechanical property test results that the mechanical properties of the straight-cone composite tube integrally formed by the method of the present invention can reach more than 90% of the mechanical properties of the parent material, which is much higher than the mechanical properties of the straight-cone composite tube obtained by the traditional processing method.

[0209] In addition, compared with the traditional processing method, when producing a straight-cone composite tube, the present invention can save two hot forming processes, save 4 days of processing cycle, and save two sets of hot forming molds, saving more than 50% of the cost; in addition, the traditional processing scheme requires closing, expanding and bulging tooling, each set of tooling costs about 30,000 yuan, that is, a total of 90,000 yuan, a processing cycle of about 6 days, and a processing cost of about 3,600 yuan; while the processing scheme of the present invention only uses 1 set of tooling to achieve closing, expanding and bulging, the tooling cost is about 60,000 yuan, the processing cycle is shortened to 2 days, and the processing cost is about 1,200 yuan. That is, the processing cycle of the present invention is shortened by 67%, the mold cost is saved by more than 50%, and the processing cost is reduced by 67%.

[0210] 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 integrally forming a straight-cone composite cylinder, characterized in that: The method comprises: (1) establishing a three-dimensional model of a straight-cone composite cylinder, and designing and manufacturing a mold, wherein the mold includes a bulging tire core and a closing mold, wherein the bulging tire core includes a conical section, and a large-diameter cylindrical section and a small-diameter cylindrical section respectively located at two ends; (2) designing the size of the mold according to the linear expansion coefficient of the straight-tapered composite tube and its size at room temperature, the linear expansion coefficient of the mold component, and the difference between the hot forming temperature and room temperature; (3) cutting, rounding and welding are performed according to the unfolded material size of the straight-cone composite cylinder three-dimensional model in the software to obtain a whole-cone cylinder blank; (4) first fixing the large diameter end face of the bulging tire core, then preheating the whole cone blank, and sleeved the whole cone blank onto the bulging tire core from the large diameter end of the whole cone, wherein the preheating temperature is equal to the molding temperature; (5) The closing die is mounted on the conical section of the bulging tire core to complete the assembly of the die; (6) the mold is heated and maintained, and pressure is applied to the closing die through the heating device platform to move the closing die downward, and cooperate with the large-diameter cylindrical section of the bulging tire core to close the blank, thereby forming a large-diameter straight tube section of the straight-cone composite tube; in addition, at the molding temperature, the conical section and the small-diameter cylindrical section of the bulging tire core are bulged to form a conical tube section and a small-diameter straight tube section of the straight-cone composite tube, respectively; (7) Cooling the mold and demoulding the mold to obtain the straight-cone composite tube.

2. The method according to claim 1, characterized in that In step (2), at the thermoforming temperature, the mold and the part are completely fitted, i.e., L 零件 =L 模具 , the size of the mold at room temperature meets: L 模具0 =L 零件0 *(1+a 零件 ·ΔT) / (1+α 模具 ·ΔT) (1) Among them, L 模具0 —Mold dimensions at room temperature; L 模具 —Mold dimensions at thermoforming temperature; α 模具 —Coefficient of linear expansion of mold; ΔT—the difference between thermoforming temperature and room temperature; L 零件0 —Part dimensions at room temperature; L 零件 —Part dimensions at thermoforming temperature α 零件 —Linear expansion coefficient of parts.

3. According to the method of claim 1 or 2, the large-diameter cylindrical section, the conical section and the small-diameter cylindrical section of the bulging tire core are an integrated structure.

4. The method according to claim 1, characterized in that: In step (4), before heating the blank, the method further includes calculating the plastic deformation of the expanded end of the blank, wherein the plastic deformation satisfies the formula Where, η is the plastic deformation of the expanded end of the preform, γ 锥2 is the radius of the flared end of the preform, γ 直2 It is the theoretical radius of the straight cone composite cylinder after expansion.

5. The method according to claim 4, characterized in that When the plastic deformation amount is ≥8%, the blank is pre-expanded.

6. The method according to claim 5, characterized in that The deviation between the inner diameter of the blank and the outer diameter of the bulging tire core is controlled within 8%, thereby completing the pre-expansion of the blank.

7. The method according to claim 1, characterized in that Step (4) also includes installing a clamping plate on the small diameter end face of the bulging tire core to prevent the blank from moving upward relative to the bulging tire core during the forming process.

8. The method according to claim 1, characterized in that In step (7), the demoulding includes adding a lubricant between the closing die and the part, and demoulding the part by pressing down the upper surface of the part.

9. The method according to claim 1, characterized in that: When the material of the straight-cone composite tube is TA15, the pressure of the die for closing the blank through the closing die is 20-80 tons.

10. A mold used in the method according to any one of claims 1 to 9, characterized in that: The mold comprises a base, a bulging tire core, a pressing plate, a closing mold and a cushion ring; The base is used to bear the weight of the mold and the blank and to position the bulging tire core; The clamping plate is used to position the bulging tire core and the connecting lugs; The bulging tire core is used for integrated forming of closing, bulging and expanding of the straight-cone composite tube; The closing mold has a cylindrical inner cavity, which is used to cooperate with the bulging tire core to complete the closing of the part; The cushion block ring is used to transmit external pressure to the closing die to achieve the closing of the blank.

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