A straight-tapered composite cylinder integrated forming die and a forming method thereof

Abstract

The present application relates to a kind of straight cone composite cylinder integrated forming die and its forming method, belong to precision hot forming processing technical field, solve the problems such as existing straight cone composite cylinder process complex, long cycle, processing difficulty, poor product precision, high cost.The die includes sequentially connected from bottom to top base, bulging core, pressing plate, and by bottom to top sleeve set on the bulging core closing die and pad ring;The bulging core can simultaneously realize the closing, flaring and bulging process of part;The base is used as the positioning reference of bulging core, and the bulging core is fixed with the pressing plate;The closing die is used for the closing forming of composite cylinder;The pad ring is used for transmitting external pressure to closing die.The forming die of the present application can realize the overall forming process of straight cone composite cylinder closing, flaring and bulging, simplify the processing procedure of existing straight cone composite cylinder, shorten processing cycle, reduce processing difficulty and cost, improve product size precision.

Description

Technical Field

[0001] This invention relates to the field of precision thermoforming technology, and in particular to an integral molding die for a straight conical composite cylinder and its molding method. Background Technology

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

[0003] Currently, due to the different diameter variation patterns of conical composite titanium cylinders, direct bulging is not possible. Traditional processes involve bulging the product through three stages: narrowing, flaring, and overall bulging. However, these traditional methods have several drawbacks: First, the process is complex and has a long processing cycle; second, it requires numerous tooling fixtures, leading to high tooling costs; third, processing is difficult, requiring three stages of thermal bulging for each product, with each stage requiring mold clamping and positioning, placing high demands on datum transfer and operational procedures; finally, the product's surface accuracy is poor, as traditional processes involve three stages—narrowing, flaring, and overall bulging—each with its own bulging error. The cumulative error across these three stages results in a significant final product surface accuracy error.

[0004] To address the shortcomings of existing technologies, a new molding die and method for forming straight conical composite cylinders are needed. This method can not only simplify the forming process, shorten the processing cycle, reduce costs and processing difficulty, but also improve the surface accuracy of the product. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide an integral molding die for a straight conical composite cylinder and a molding method thereof, in order to solve at least one of the problems of complex processes, long cycles, high processing difficulty, poor product precision, and high costs in the existing traditional process of straight conical composite cylinders.

[0006] In a first aspect, embodiments of the present invention provide an integral molding mold for a straight cone composite cylinder, the mold comprising a base, an expanded core, a pressing plate, and a closing mold and a pad ring fitted on the expanded core from bottom to top, which are rigidly connected in sequence from bottom to top;

[0007] The bulging core includes a conical section in the middle, and a large-diameter cylindrical section and a small-diameter cylindrical section at both ends. The conical section is used for bulging the billet to form the conical section of the straight-conical composite cylinder; the small-diameter cylindrical section is used for flaring the billet to form the small-diameter straight section of the straight-conical composite cylinder; the large-diameter cylindrical section is used for closing the billet to form the large-diameter straight section of the straight-conical composite cylinder, wherein the billet is a whole conical billet;

[0008] The closing mold has a cylindrical inner cavity, which is fitted onto the bulging core and is used to cooperate with the large-diameter cylindrical section of the bulging core to close the blank and form a large-diameter straight cylindrical section of the straight conical composite cylinder.

[0009] The pad 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 mold to realize the closing of the blank.

[0010] Furthermore, the large-diameter end of the bulging tire core is threadedly connected to the base, and the small-diameter end is threadedly connected to the clamping plate.

[0011] Furthermore, before the blank is formed, the inner diameter of the closing mold fitted on the bulging core is smaller than the outer diameter of the end of the whole conical blank to be closed, so that the closing mold does not contact the base.

[0012] Furthermore, during the blank forming process, the closing mold moves downward under external pressure, contacts the base, and cooperates with the large-diameter cylindrical section of the bulging core to close the blank, forming a large-diameter straight cylindrical section of the straight conical composite cylinder.

[0013] Furthermore, the coefficient of thermal expansion of the bulging tire core is greater than that of the straight cone composite cylinder.

[0014] Furthermore, the material of the straight conical composite cylinder is TA15, TC4, or aluminum alloy;

[0015] Furthermore, the material of the bulging tire core is selected from stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, and ceramic materials;

[0016] Furthermore, the other parts of the mold are made of one of the following materials: stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, and heat-resistant alloy steel.

[0017] Furthermore, the dimensions of the expanded tire core satisfy the following:

[0018] L 胎芯 =L 胎芯0 (1+α 胎芯 ·ΔT) (1)

[0019] L 胎芯0 = R 零件0 *(1+α 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (2)

[0020] Among them, L 胎芯0 —Outer diameter of the inflated tire core at room temperature;

[0021] L 胎芯—Outer diameter of the bulging core at the thermoforming temperature;

[0022] α 胎芯 —Coefficient of expansion of the tire core wire;

[0023] ΔT—The difference between thermoforming temperature and room temperature;

[0024] R 零件0 —Inner diameter of the straight conical composite cylinder at room temperature;

[0025] α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

[0026] Furthermore, the dimensions of the closing mold satisfy the following:

[0027] R 收口模 =R 收口模0 (1+α 收口模 ·ΔT) (3)

[0028] R 收口模0 = L 零件0 *(1+α 零件 ·ΔT) / (1+α 收口模 ·ΔT) (4)

[0029] Among them, R 收口模0 —Inner diameter of the closing mold at room temperature;

[0030] R 收口模 —The inner diameter of the die at the thermoforming temperature;

[0031] α 收口模 —Coefficient of linear expansion of the seam trimmer;

[0032] ΔT—The difference between thermoforming temperature and room temperature;

[0033] L 零件0 —Outer diameter of the straight conical composite cylinder at room temperature;

[0034] α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

[0035] Secondly, embodiments of the present invention provide a method for integrally molding a straight conical composite cylinder, wherein the mold described above specifically includes:

[0036] (1) Establish a three-dimensional model of the straight cone composite cylinder, and cut, circle and weld it according to its unfolded material size in the software to obtain the whole cone cylinder blank;

[0037] (2) The whole conical blank is fitted onto the bulging core of the mold, and the mold is assembled;

[0038] (3) Heat the mold assembled in step (2), apply pressure to the pad ring, and maintain it;

[0039] (4) Cool the mold and demold it to obtain the straight cone composite cylinder.

[0040] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0041] 1. The mold of this invention includes a base, an expanding core, a clamping plate, and a closing mold and a pad ring, which are rigidly connected from bottom to top on the expanding core. Through the coordinated cooperation between the various components of the mold, the closing, expanding, and bulging of the straight conical composite cylinder can be achieved in one integrated molding process. Compared with the traditional manufacturing method of the existing straight conical composite cylinder, the mold of this invention simplifies the processing steps of the straight conical composite cylinder, reducing the number of process steps from 3 to 1, shortening the processing cycle by two-thirds; the number of tooling sets is reduced from 3 to 1, saving more than half of the tooling components; the closing, expanding, and bulging processes can be achieved in one clamping, reducing the difficulty of operation, processing difficulty, and cost; at the same time, it avoids the error accumulation phenomenon of multiple processes and improves the surface accuracy of the product.

[0042] 2. Before the blank is formed, the inner diameter of the closing mold fitted on the expanding core is smaller than the outer diameter of the end of the conical blank to be closed, so that the closing mold does not contact the base; during the blank forming, the closing mold moves downward under external pressure and contacts the base, and cooperates with the large-diameter cylindrical section of the expanding core to realize the closing of the blank, forming the large-diameter straight cylindrical section of the straight conical composite cylinder.

[0043] 3. The mold of the present invention achieves the closing of the straight conical composite cylinder part through the mutual cooperation between the closing mold and the large-diameter cylindrical section of the expanding core; the conical section of the expanding core achieves the expansion of the composite cylinder; the small diameter of the expanding core achieves the widening of the composite cylinder, and the part and the mold are completely fitted together at the forming temperature; therefore, the mold size is determined by the size of the straight conical composite cylinder part to be produced.

[0044] The dimensions of the bulging core can be designed based on the linear expansion coefficient of the conical composite cylinder and its inner diameter at room temperature, the linear expansion coefficient of the bulging core, and the difference between the thermoforming temperature and room temperature; the dimensions of the closing mold can be designed based on the linear expansion coefficient of the conical composite cylinder and its outer diameter at room temperature, the linear expansion coefficient of the closing mold, and the difference between the thermoforming temperature and room temperature, so as to ensure the forming accuracy of the conical composite cylinder.

[0045] 4. The thermal expansion coefficient of the bulging core material of the present invention is greater than that of the straight conical composite cylinder material to be processed. When the entire conical cylinder blank is thermoformed using a mold with a larger thermal expansion coefficient, not only is a better forming effect achieved, but it is also easy to demold after the forming and cooling process. The material constituting the bulging core of the present invention can be stainless steel.

[0046] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0048] Figure 1 This is a schematic diagram of the structure of the integral molding mold for the straight cone composite cylinder of the present invention;

[0049] Figure 2 This is an assembly diagram of the integral molding mold for the straight cone composite cylinder of the present invention;

[0050] Figure label:

[0051] 1-Base; 2-Pressure plate; 3-Expanded core; 4-Closing mold; 5-Padded ring; 6-Blank. Detailed Implementation

[0052] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which 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 intended to limit the scope of the present invention.

[0053] As aerospace components become increasingly complex, tapered composite titanium cylinders, as a typical component, are widely used in aerospace vehicles. Due to their varying diameter variations, tapered composite titanium cylinders cannot currently be directly integrally bulged. Traditional processes involve three steps: constriction bulging, flaring bulging, and integral bulging, which have the following drawbacks: complex processes leading to long processing cycles; the need for numerous tooling fixtures resulting in high costs; difficult processing, requiring three thermal bulging stages for each product, each requiring mold clamping and positioning, placing high demands on datum transfer and operational processes; and poor product surface accuracy, as each step in the traditional process introduces bulging errors, and the cumulative error across the three stages results in significant surface accuracy errors in the final product.

[0054] Therefore, this invention discloses a mold for integral molding of a straight conical composite cylinder, such as... Figure 1 As shown, the mold includes a base 1, an expanded tire core 3, a pressing plate 2, and a closing mold 4 and a pad ring 5, which are rigidly connected from bottom to top on the expanded tire core.

[0055] The bulging core includes a conical section in the middle, and a large-diameter cylindrical section and a small-diameter cylindrical section at both ends. The conical section is used for bulging the billet to form the conical section of the straight-conical composite cylinder; the small-diameter cylindrical section is used for flaring the billet to form the small-diameter straight section of the straight-conical composite cylinder; the large-diameter cylindrical section is used for closing the billet to form the large-diameter straight section of the straight-conical composite cylinder, wherein the billet is a whole conical billet;

[0056] The closing mold has a cylindrical inner cavity, which is fitted onto the bulging core and is used to cooperate with the large-diameter cylindrical section of the bulging core to close the blank and form a large-diameter straight cylindrical section of the straight conical composite cylinder.

[0057] The pad 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 mold to realize the closing of the blank.

[0058] The bulging core of this invention includes a conical section in the middle, and large-diameter cylindrical sections and small-diameter cylindrical sections at both ends. Besides supporting the blank and controlling the shape of the product, it is mainly used to achieve the integrated forming process of closing, flaring, and bulging of the straight-cone composite cylinder part. The base is used to support the weight of the mold and position the bulging core. The clamping plate, together with the base, is used to fix the bulging core. The closing mold is used to cooperate with the large-diameter cylindrical section of the bulging core to close the blank. The pad ring is used to transmit external pressure to the closing mold.

[0059] Specifically, the dimensions of the expanded tire core described in this invention satisfy the following requirements:

[0060] L 胎芯 =L 胎芯0 (1+α 胎芯 ·ΔT) (1)

[0061] L 胎芯0 = R 零件0 *(1+α 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (2)

[0062] Among them, L 胎芯0 —Outer diameter of the inflated tire core at room temperature;

[0063] L 胎芯 —Outer diameter of the bulging core at the thermoforming temperature;

[0064] α 胎芯 —Coefficient of expansion of the tire core wire;

[0065] ΔT—The difference between thermoforming temperature and room temperature;

[0066] R零件0 —Inner diameter of the straight conical composite cylinder at room temperature;

[0067] α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

[0068] Specifically, the structure and dimensions of the bulging core are determined by the structure and dimensions of the straight conical composite cylinder part to be produced. To ensure the stability and adaptability of the part during hot working, the design principle of the bulging core is as follows:

[0069] Assuming the part is formed at a certain temperature T, the straight tapered composite cylinder part is completely fitted with the bulging core, and the inner diameter R of the part... 零件 Equal to the outer diameter L of the bulging tire core 胎芯 L 胎芯 =R 零件 Among them, the following relationships also exist:

[0070] R 零件 =R 零件0 (1+α 零件 ·ΔT) (5)

[0071] Among them, R 零件 —The inner diameter of the straight conical composite cylinder at the forming temperature; and the outer diameter of the bulging core at room temperature is derived from the above relationship.

[0072] Specifically, the lengths and diameters of the cylindrical and conical sections of the expanded tire core are determined by the dimensions of the straight conical composite cylinder to be processed. The length of the conical section is equal to the length of the conical part in the straight conical composite cylinder to be processed. The length of the cylindrical section is 20-50mm longer than the length of the straight part in the straight conical composite cylinder to be processed. It is used for finishing the rough product after hot working to remove the excess material and remove the uneven parts at both ends. The outer diameter of each section of the expanded tire core is calculated by formula (2).

[0073] In addition, the thickness of the expansion core described in this invention is based on being able to withstand the pressure and temperature during the hot working process, ensuring the strength and stability of the expansion core. A suitable thickness range of the expansion core is beneficial to the expansion performance of the expansion core and the convenience of demolding.

[0074] The inflatable core is solid or hollow, preferably hollow, which helps with heat conduction and dissipation, preventing deformation or damage due to overheating, helping to maintain the machining accuracy and stability of the parts, and also facilitating movement and operation, improving efficiency and reducing costs.

[0075] Specifically, in this invention, the large-diameter end of the expanded tire core is threaded to the base, and the small-diameter end is threaded to the pressure plate; preferably, the large-diameter end of the expanded tire core with a hollow structure can also be sleeved around the annular protrusion of the base, and the small-diameter end can be sleeved around the cylindrical protrusion of the pressure plate.

[0076] Furthermore, the large-diameter end face of the expanded tire core has symmetrically distributed built-in threaded holes along the circumference. The number of built-in threaded holes is the same as the corresponding threaded holes on the base, which is 4-6. The large-diameter end of the expanded tire core is fixed to the base by bolts. The small-diameter end of the expanded tire core has symmetrically distributed built-in threaded holes along the circumference. The number of built-in threaded holes is the same as the corresponding threaded holes on the pressure plate, which is 4-6. The small-diameter end of the expanded tire core is fixed to the pressure plate by bolts.

[0077] Furthermore, in order to ensure that the bulging core has sufficient strength and rigidity, and to facilitate heat conduction and dissipation, the material of the bulging core can be selected from stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, and ceramic materials.

[0078] Specifically, the coefficient of thermal expansion of the bulging core material of the present invention is greater than that of the blank to be processed. When the entire conical blank is thermoformed using a mold with a larger coefficient of thermal expansion, not only is a better forming effect achieved, but it is also easy to demold after the forming and cooling process.

[0079] According to some preferred embodiments of the present invention, when hot-working the TA15 titanium alloy straight tapered composite cylinder, the bulging core can be prepared by selecting 316 stainless steel with a thermal expansion coefficient greater than that of TA15 titanium alloy.

[0080] The materials for other parts of this invention are one of stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, and heat-resistant alloy steel.

[0081] Based on the shape of the desired conical composite cylinder, the inner cavity of the closing mold is designed to be cylindrical for closing and forming the conical composite cylinder. The dimensions of the closing mold of this invention satisfy the following requirements:

[0082] R 收口模 =R 收口模0 (1+α 收口模 ·ΔT) (3)

[0083] R 收口模0 = L 零件0 *(1+α 零件 ·ΔT) / (1+α 收口模 ·ΔT) (4)

[0084] Among them, R 收口模0—Inner diameter of the closing mold at room temperature;

[0085] R 收口模 —The inner diameter of the die at the thermoforming temperature;

[0086] α 收口模 —Coefficient of linear expansion of the seam trimmer;

[0087] ΔT—The difference between thermoforming temperature and room temperature;

[0088] L 零件0 —Outer diameter of the straight conical composite cylinder at room temperature;

[0089] α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

[0090] Specifically, the structure and dimensions of the closing die are determined by the structure and dimensions of the straight tapered composite cylinder part to be produced. To ensure the stability and adaptability of the part during the hot working process, the design principle of the closing die is as follows:

[0091] Assuming the part is formed at a certain temperature T, the straight tapered composite cylinder part fits perfectly with the closing mold, and the outer diameter L of the part... 零件 Equal to the inner diameter R of the closing die 收口模 L 零件 =R 收口模 Among them, the following relationships also exist:

[0092] L 零件 =L 零件0 (1+α 零件 ·ΔT) (6)

[0093] Among them, 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.

[0094] Specifically, the length of the closing mold is greater than or equal to the length of the hollow cylindrical section at the large diameter end of the bulging core. At the part forming temperature, it cooperates with the large diameter cylindrical section of the bulging core to close the blank.

[0095] Before the blank is formed, the inner diameter of the closing mold fitted on the expanding core is smaller than the outer diameter of the end of the conical blank to be closed, so that the closing mold does not contact the base; during the blank forming, the closing mold moves downward under external pressure and contacts the base, and cooperates with the large-diameter cylindrical section of the expanding core to realize the closing of the blank, forming the large-diameter straight cylindrical section of the straight conical composite cylinder.

[0096] According to some preferred embodiments of the present invention, the end of the closing mold that contacts the pad ring is designed as a circular ring structure with an outer diameter larger than the outer diameter of other parts of the closing mold, which is used to withstand the external pressure transmitted by the pad ring. The other parts of the closing mold are cylindrical. The structure of the straight conical composite cylinder of the present invention facilitates movement and operation, improves efficiency, and reduces material costs.

[0097] Furthermore, the straight cylindrical portion of the closing mold is symmetrically provided with threaded through holes for installing lifting lugs during mold assembly and for installing thermocouples during hot working; the annular portion of the closing mold is symmetrically provided with threaded internal holes for installing lifting lugs during mold assembly and for fixing to the pad ring with bolts during hot working.

[0098] Furthermore, the closing die needs to have high strength to withstand external pressure of 20-80 tons, improve durability, and ensure hot working accuracy; in addition, the selection of the closing die material should also take into account the material characteristics of the parts to be processed and the working environment.

[0099] Specifically, the material of the closing mold is one of stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, or ceramic material. When the coefficient of thermal expansion of the closing mold material is less than that of the part being prepared, it is easy to demold after molding and cooling; when the coefficient of thermal expansion of the closing mold material is greater than or equal to that of the part being prepared, it is not easy to demold after molding and cooling, and demolding requires the use of lubricating oil and the application of pressure. The specific operation will be discussed later.

[0100] The present invention utilizes the base as a positioning standard for the expanded tire core, and together with the clamping plate, it is used to fix the expanded tire core.

[0101] Specifically, the base is used to support the weight of the mold and blank, as well as external pressure. It needs to have a certain thickness and strength. The thickness range is determined by the material of the base, the material and size of the blank that needs to be heat-treated. For example, when the TA15 titanium alloy straight tapered composite cylinder of the embodiment is made of 304 stainless steel, the thickness of the base can be 10-30mm. The base has a disc-shaped or ring-shaped structure. The ring-shaped structure is conducive to heat transfer and improves the heat utilization rate and uniformity during the hot working of the blank. The inner circumference of the upper surface of the ring-shaped base has an annular protrusion with a height of 5-30mm. 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 core, which is used to position the large diameter end of the bulging core.

[0102] It should be noted that the thickness of a certain annular area on the outer edge of the base is reduced in order to fix it to the heat treatment equipment of the parts when installing the mold. It is preferable to use a pressure plate for fixing, and the thickness of the annular area is controlled to be 10-30mm.

[0103] Furthermore, the base has threaded through holes I evenly distributed along a certain circumference, the diameter of which matches the size of the large diameter end of the bulging core, for threaded fixing of the bulging core, and the number of these through holes is 4-6. In addition, in order to facilitate mold assembly and precise control of the heating temperature during hot working, threaded through holes II are provided around the through holes I on the base, the number of which is 4-6, for installing lifting lugs during mold assembly and for installing thermocouples during hot working.

[0104] Specifically, the clamping plate has a disc-shaped structure and is used together with the base to fix the bulging core. The clamping plate is connected to the core by bolts, which can prevent the blank from moving upward relative to the core during the forming process.

[0105] Preferably, the central area of ​​the lower surface of the pressure plate has a cylindrical protrusion with a height of 10-20mm. The diameter of the cylindrical protrusion is less than or equal to the inner diameter of the small diameter end of the hollow inflatable tire core, so as to position the small diameter end of the inflatable tire core.

[0106] Furthermore, the clamping plate is threadedly connected to the expanded tire core. Specifically, the base has threaded through holes A evenly distributed along a certain circumference. The diameter of the circumference matches the size of the small diameter end of the expanded tire core, used to thread-fix the expanded tire core. The number of through holes is 4-6. Furthermore, to facilitate the disassembly and assembly of the clamping plate, the hole for the threaded connection between the clamping plate and the expanded tire core can be designed as an irregular hole. The irregular hole includes two connected circular holes with different diameters, namely a large-diameter hole and a small-diameter hole. During normal use, the bolts are not removed, the clamping plate is removed, and when installing the clamping plate, the nut passes through the large-diameter hole. After installation, the nut is turned to the small-diameter hole for positioning.

[0107] In addition, a lifting lug is threaded at the center of the upper surface of the clamping plate to facilitate mold loading and unloading.

[0108] Specifically, the padding ring includes an upper bottom ring surface, a lower bottom ring surface, and a support column located in the middle, used to transmit external pressure to the closing mold to achieve the closing of the blank; before the forming of the straight tapered composite cylinder, the closing mold and the padding ring are sleeved on the expanding core from bottom to top, with the padding ring on top of the closing mold and the two being threaded together, wherein the closing mold does not contact the base; at the blank forming temperature, pressure is applied to the upper ring surface of the padding ring through the heating device platform, and the pressure is transmitted to the closing mold through the padding ring. Under the action of external pressure, the closing mold moves downward and contacts the base, cooperating with the large-diameter cylindrical section of the expanding core to achieve the closing of the blank, forming the large-diameter straight cylindrical section of the straight tapered composite cylinder.

[0109] According to some preferred embodiments of the present invention, the upper and lower bottom surfaces of the pad ring are circular ring structures of the same size, the diameter of the hollow circle in the middle is equal to the diameter of the cylindrical inner cavity of the closing mold, and the outer diameter is greater than or equal to the outer diameter of the circular portion of the closing mold. The closing mold needs to have high strength to withstand external pressure of 20-80 tons, improve durability, and ensure the accuracy of heat treatment.

[0110] Furthermore, threaded through holes are provided on the upper and lower bottom surfaces of the pad ring. The support column is a cylinder with threads at both ends. After being connected to the lower bottom surface, the support column can penetrate the lower bottom surface and be fixed by a nut below the lower bottom surface. After being connected to the upper bottom surface, the support column cannot penetrate 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 pad ring.

[0111] Furthermore, in order to ensure the stability of the mold under external force during the hot processing of the parts, the outer diameter of the base is greater than or equal to the diameter of the bottom surface of the pad ring.

[0112] The magnification factor of the mold described in this invention is 3-6‰, which on the one hand facilitates the installation of the thermally expanded blank onto the bulging core, and on the other hand ensures the dimensional accuracy of the thermoformed product and avoids molding defects, achieving a small blank with a large core and improving the product molding quality.

[0113] According to some preferred embodiments of the present invention, when preparing the TA15 titanium alloy straight conical composite cylinder, the material of the bulging core is 316 stainless steel, and the material of other parts of the mold is 304 stainless steel.

[0114] The mold described above in this invention is prepared by casting and machining methods.

[0115] The present invention also discloses a method for integral molding of a straight conical composite cylinder, wherein the method uses the mold described in the first aspect of the present invention.

[0116] The method includes:

[0117] (1) Establish a three-dimensional model of the straight cone composite cylinder, and cut, circle and weld it according to its unfolded material size in the software to obtain the whole cone cylinder blank;

[0118] (2) The whole conical blank is fitted onto the bulging core of the mold, and the mold is assembled;

[0119] (3) Heat the mold assembled in step (2), apply pressure to the pad ring, and maintain it;

[0120] (4) Cool the mold and demold it to obtain the straight cone composite cylinder.

[0121] According to some preferred embodiments of the present invention, the method specifically includes:

[0122] (1) Establish a three-dimensional model of a straight cone composite cylinder, design and manufacture a mold, the mold including a base, an expansion core, a pressing plate, a closing mold and a pad ring;

[0123] (2) Based on the linear expansion coefficient of the conical composite cylinder and its inner diameter at room temperature, the linear expansion coefficient of the bulging core, and the difference between the thermoforming temperature and room temperature, design the dimensions of the bulging core; based on the linear expansion coefficient of the conical composite cylinder and its outer diameter at room temperature, the linear expansion coefficient of the closing die, and the difference between the thermoforming temperature and room temperature, design the dimensions of the closing die.

[0124] (3) Based on the unfolded material dimensions of the straight conical composite cylinder three-dimensional model in the software, the blank is cut, circled and welded to obtain the whole conical cylinder blank;

[0125] (4) First, connect the large diameter end face of the bulging core to the base, then preheat the whole conical blank, and put it on the bulging core from the large diameter end of the whole conical core so that the bottom of the blank is supported on the base. Then, install the clamping plate on the small diameter end face of the bulging core, wherein the preheating temperature is equal to the molding temperature.

[0126] (5) First, the closing mold is fitted onto the conical section of the expanding tire core, and then the pad ring is fitted onto the expanding tire core and the top of the closing mold to complete the assembly of the mold. The closing mold does not contact the base.

[0127] (6) Heat the mold and apply pressure to the upper surface of the pad ring through the heating device platform. The pressure is transmitted to the closing mold through the pad ring, so that the closing mold moves downward until it contacts the base and remains there for a period of time.

[0128] (7) Cool the mold and demold it to obtain the straight cone composite cylinder.

[0129] Specifically, in step (1), a three-in-one bulging mold for closing, flaring, and bulging is designed and manufactured based on the three-dimensional model of the straight conical composite cylinder. This invention can use casting and machining methods to manufacture the mold, resulting in a mold as shown in the image. Figure 1 As shown, the mold includes a base 1, an inflatable core 3, a pressing plate 2, a closing mold 4, and a pad ring 5.

[0130] Specifically, in step (2), the specific structure and dimensional parameters of each part of the mold of the present invention are determined by the structure and size of the produced straight conical composite cylinder: the size of the bulging core is designed according to the linear expansion coefficient of the straight conical composite cylinder and its inner diameter at room temperature, the linear expansion coefficient of the bulging core, and the difference between the thermoforming temperature and room temperature; the size of the closing mold is designed according to the linear expansion coefficient of the straight conical composite cylinder and its outer diameter at room temperature, the linear expansion coefficient of the closing mold, and the difference between the thermoforming temperature and room temperature.

[0131] Specifically, the dimensions of the expanded tire core described in this invention satisfy the following requirements:

[0132] L 胎芯 =L 胎芯0 (1+α 胎芯 ·ΔT) (1)

[0133] L 胎芯0 = R 零件0 *(1+α 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (2)

[0134] Among them, L 胎芯0 —Outer diameter of the inflated tire core at room temperature;

[0135] L 胎芯 —Outer diameter of the bulging core at the thermoforming temperature;

[0136] α 胎芯 —Coefficient of expansion of the tire core wire;

[0137] ΔT—The difference between thermoforming temperature and room temperature;

[0138] R 零件0 —Inner diameter of the straight conical composite cylinder at room temperature;

[0139] α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

[0140] Specifically, the dimensions of the closing mold described in this invention satisfy the following:

[0141] R 收口模 =R 收口模0 (1+α 收口模 ·ΔT) (3)

[0142] R 收口模0 = L 零件0 *(1+α 零件 ·ΔT) / (1+α 收口模 ·ΔT) (4)

[0143] Among them, R 收口模0 —Inner diameter of the closing mold at room temperature;

[0144] R 收口模 —The inner diameter of the die at the thermoforming temperature;

[0145] α 收口模 —Coefficient of linear expansion of the seam trimmer;

[0146] L 零件0 —Outer diameter of the straight conical composite cylinder at room temperature;

[0147] A schematic diagram of the mold assembly for the integral molding method of the straight conical composite cylinder of the present invention is shown below. Figure 2 As shown.

[0148] According to a preferred embodiment of the present invention, when preparing the TA15 titanium alloy straight conical composite cylinder, the material of the bulging core is 316 stainless steel, and the material of other parts of the mold is 304 stainless steel. The magnification factor of the mold is 3‰.

[0149] Specifically, in step (3), the three-dimensional model of the straight cone composite cylinder is unfolded, and the unfolded material size is accurately calculated. The method is as follows: In the UG software, a new plane is created in the modeling module, and the product model is divided into two parts. Then, one of the cutting edges is offset by 0.1mm on both sides, so that there is a gap of 0.2mm on this edge. Then, the split model is summed to obtain a solid. The solid is unfolded by sheet metal unfolding operation. After unfolding, the theoretical unfolded model size can be obtained by offsetting 0.1mm on each side.

[0150] Furthermore, the blank is cut according to the unfolded material size. The blanking method can be laser cutting, wire cutting, CNC punching, shearing machine, water jet cutting, machining, etc. According to the preferred embodiment of the present invention, laser cutting is used for blanking. The blank is rounded to ensure that the end faces on both sides of the weld can be flush and butt-jointed. The rounded product is pickled to clean the oil stains and excess material on the surface of the blank. The blank is welded, and the welded part is an irregularly shaped conical cylinder.

[0151] If the dimensions and quality of the conical section of the billet, such as flatness, do not meet the requirements of actual application, it needs to be subjected to bulging heat treatment. The working principle is as follows: by selecting materials with different coefficients of thermal expansion, the roundness of the product can be adjusted; a material with a coefficient of thermal expansion greater than that of the billet material can be selected as the mold core material. The billet with a room temperature diameter greater than the room temperature core diameter, or a billet with a diameter greater than the room temperature core diameter after heating, is installed on the core. After heating together to a certain temperature T, the core diameter is greater than the product diameter, thereby achieving the bulging effect.

[0152] According to some preferred embodiments of the present invention, the material of the billet conical cylinder is TA15 titanium alloy, and the coefficient of thermal expansion at a temperature of (20-800)℃ is 9.7×10⁻⁶. -6The tire core material is 316 stainless steel, and its coefficient of thermal expansion at temperatures ranging from 20 to 800°C is approximately 16.5 × 10⁻⁶. -6 / ℃, the outer diameter of the tire core reaches the theoretical inner diameter of the straight conical composite cylinder when heated to 700℃, then the diameter of the blank at room temperature is greater than the diameter of the tire core.

[0153] The blank is a conical cylinder, and the large-diameter end of the conical cylinder needs to be narrowed to a straight cylinder. The working principle of narrowing is as follows: after assembling the blank onto the core, the narrowing mold is installed, and the steps are as follows. Figure 2 As shown; when heated to the target temperature, the inner diameter of the closing mold is the theoretical outer diameter of the product's straight conical composite cylinder. The blank is a whole cone shape. The closing mold cannot be directly installed to the bottom. It needs to be installed as shown in the figure before heating. After heating to the target temperature T, the platform on the equipment transmits pressure to the closing mold through the clamping ring. The closing mold moves downward until the closing mold and the base are in complete contact. This process is the closing process.

[0154] The billet is a conical cylinder, and the smaller diameter end of the conical cylinder needs to be flared into a straight cylinder. The maximum flaring range is determined by the ratio of the difference between the product's neutral layer perimeter and the billet's neutral layer perimeter to the billet's neutral layer perimeter, which must be within the material's elongation after fracture range. That is: (Product neutral layer perimeter - Billet neutral layer perimeter) / Billet neutral layer perimeter ≤ Material elongation after fracture. For example: if the material's elongation after fracture is 10%, then... Where l2 is the perimeter of the neutral layer of the product, and l1 is the perimeter of the neutral layer of the billet.

[0155] Specifically, the straight conical composite cylinder preform obtained in step (2) is an irregular conical shape, and the bulging core is the shape of the theoretical model of the straight conical cylinder. The amount of plastic deformation at the flared end of the blank is calculated according to formula (7):

[0156]

[0157] Where η is the amount of plastic deformation at the flared end of the preform blank;

[0158] γ 锥2 The radius of the flared end of the preform blank;

[0159] γ 直2 This is the theoretical radius of the flared straight conical composite cylinder.

[0160] When the plastic deformation is ≥8%, the billet is directly placed on the expansion mold. Due to the small diameter of the billet and the large diameter of the expansion core, it is difficult to place it on the mold. Therefore, it is necessary to pre-expand the flared end. The specific steps of the pre-expansion are as follows: using conventional flaring methods, a certain length of the small-diameter section of the whole conical billet is pre-expanded. Pre-expansion can be completed in three ways:

[0161] The first method uses calculus to pre-expand the small-diameter conical section into a cylinder. First, a cylindrical section 1 is used for pre-expansion. The diameter of the cylindrical section 1 is half the sum of the outer diameter of the flared end of the bulging core and the inner diameter of the small end of the conical cylinder in the billet. The length of the cylindrical section 1 is greater than or equal to the length of the straight cylinder section in the theoretical model. The cylindrical section 1 is inserted 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 pre-expanded billet and the outer diameter of the bulging core is within 8%, the pre-expansion is complete. If the deviation of the tire core's outer diameter exceeds 8%, pre-expansion is performed using cylindrical segment 2. The diameter of cylindrical segment 2 is the sum of half the outer diameter of the expanded tire core's flared end and the inner diameter of the blank after the first pre-expansion. This is repeated until the deviation between the inner diameter of the blank and the outer diameter of the expanded tire core is within 8%, thus completing the pre-expansion of the blank. The pre-formed blank is then heated or not heated, and the pre-expansioned blank is installed on the expanded tire core, ensuring that the bottom of the blank contacts the base. Finally, the clamping plate is installed on the small-diameter end of the expanded tire core.

[0162] The second method involves machining a stainless steel straight column with a diameter equal to that of the blank end face. The pre-expanded cylinder is placed into the blank at room temperature, and then heated for pre-expansion. After cooling, this step of expansion is repeated until the deviation between the blank diameter and the expansion core diameter is within 8%.

[0163] The third method involves processing a conical column with a diameter equal to the inner diameter of the small end of the billet. The conical column is placed into the billet at room temperature, and then heated for pre-expansion. After cooling, this step is repeated to perform iterative pre-expansion until the deviation between the billet diameter and the diameter of the bulging core is within 8%.

[0164] When the amount of plastic deformation is less than 8%, it is not necessary to pre-expand the entire conical blank. It can be expanded directly, that is, the blank is heated or not heated and then installed on the expansion core, ensuring that the bottom of the blank contacts the base; then the clamping plate is installed at the small diameter end of the expansion core.

[0165] It should be noted that the present invention heats the straight conical preform to cause thermal expansion, so that it can be fitted onto the expanded core, thereby achieving a small live part and a large core, and improving the product expansion quality.

[0166] It should be noted that the temperature at which the billet is heated before installation should be lower than the melting point of the billet, so as not to change the microstructure of the billet. The preferred heating temperature is the temperature at which the billet is heat-processed.

[0167] After installing the blank, place the closing mold and retaining ring onto the bulging core in sequence, with their relative positions as follows: Figure 2As shown, the closing mold and the retaining ring are fixedly connected by bolts; the assembled mold is installed on the equipment platform to ensure that the closing mold and the pad retaining ring are perpendicular to the base and without any tilting.

[0168] It should be noted that, according to some preferred embodiments of the present invention, the total weight of the closing die and the retaining ring is 150-200 kg, the pressure of closing the blank by the closing die is 20-80 tons, when the inner diameter of the closing die at the hot working temperature is equal to the theoretical outer diameter of the large diameter cylinder of the straight tapered composite cylinder, when the closing die and the retaining ring are sequentially placed on the bulging core, the closing die will not reach the bottom of the bulging core and contact the base. When the coefficient of thermal expansion of the closing die material is greater than or equal to the coefficient of thermal expansion of the part, the distance between the closing die and the base is ≥ the length of the closing section.

[0169] The mold is heated to the heat treatment temperature of the straight cone composite cylinder. Then, pressure is applied to the mold by controlling the upper and lower platforms. The retaining ring and the closing mold part move downward until the closing mold contacts the base. After the closing mold contacts the base, the temperature is maintained for a period of time to ensure that the heat treatment is in place.

[0170] According to a preferred embodiment of the present invention, a straight conical composite cylinder preform made of TA15 titanium alloy is heated to 600-700°C; then a pressure of 20-50 tons is applied to the mold, and the retaining ring and closing mold part moves downward until the closing mold and the base are in contact. After the closing mold and the base are in contact, the heat and pressure are maintained for 1-5 hours.

[0171] It should be noted that, since the coefficient of thermal expansion of the material constituting the bulging core is greater than that of the material of the straight conical composite cylinder, the expansion amplitude of the bulging core after heating is greater than that of the straight conical composite cylinder preform, thus achieving the bulging of the part; by selecting the material of the bulging core, calculating the outer diameter of the large-diameter straight cylinder section at the heat treatment temperature, selecting the material of the closing die, and calculating its inner diameter at the heat treatment temperature, the closing of the large-diameter end of the blank is completed; in addition, by selecting the material of the bulging core and calculating the outer diameter of the small-diameter straight cylinder section at the heat treatment temperature, the flaring of the small-diameter end of the blank is completed.

[0172] After the billet has undergone heat treatment, the equipment is allowed to cool down naturally. The mold is then removed from the equipment, and the retaining ring, clamping plate, base, and bulging core are disassembled.

[0173] It should be noted that when the coefficient of thermal expansion of the closing mold is less than that of the straight tapered composite cylinder, it can be directly demolded after cooling; when the coefficient of thermal expansion of the closing mold is greater than that of the straight tapered composite cylinder, it cannot be directly demolded after cooling. Lubricant needs to be added between the closing mold and the heat-treated part, and left for a period of time, at least 20 minutes. Then, the closing mold and the part are placed on the press platform, the clamping plate is placed on the upper surface of the part, and the upper surface of the part is slowly pressed down (speed ≤ 5 mm / s) by controlling the platform of the equipment to demold the part.

[0174] It should be noted that, since the coefficient of thermal expansion of the material constituting the bulging core is greater than that of the material of the conical composite cylinder, a pore is formed between the bulging core and the conical composite cylinder after the conical composite cylinder is cooled, making it easy to disassemble the bulging core; in addition, the present invention achieves zero-angle demolding of the conical composite cylinder, thus broadening the boundaries of the thermoformed product structure.

[0175] The method for integral molding of a straight conical composite cylinder of the present invention utilizes the aforementioned mold to achieve the integral molding process of closing, flaring, and bulging, simplifying the processing steps of the straight conical composite cylinder, reducing the number of process steps from 3 to 1, and shortening the processing cycle by two-thirds; the number of tooling sets is reduced from 3 to 1, saving more than half of the tooling components; the closing, flaring, and bulging processes can be completed in one clamping, reducing the difficulty of operation, processing difficulty, and cost; at the same time, it avoids the accumulation of errors from multiple processes and improves the surface accuracy of the product.

[0176] Example 1

[0177] A mold 1 for integral hot forming of a straight conical composite cylinder, with a magnification factor of 3‰, has the following characteristics: Figure 1 The structure shown includes a base 1, a clamping plate 2, an expanded core 3, a closing mold 4, and a pad ring 5.

[0178] The base 1 has an annular structure for bearing the weight of the mold and blank, as well as external pressure, and for positioning the bulging core 3. It includes an annular protrusion, threaded through hole I, and threaded through hole II located on the inner circumference of the ring. The annular protrusion is used to position the bulging core 3. With the center of the base 1 as the center, the threaded through holes I are symmetrically distributed along one circumference, with a quantity of 4, for threaded connection of the bulging core 3. On the periphery of the threaded through holes, the threaded through holes II are symmetrically distributed along another circumference, with a quantity of 4, for installing lifting lugs during mold assembly and for installing thermocouples during hot working.

[0179] The clamping plate 2 has a disc structure for positioning the expanded core 3; it includes a cylindrical protrusion, a threaded through hole A, and a threaded through hole B located in the central area; the cylindrical protrusion is used to position the expanded core 3; with the center of the clamping plate 2 as the center, the threaded through holes A are symmetrically distributed along a circle, with a quantity of 4, for threaded connection of the expanded core 3; the threaded through hole B is located at the center of the back of the cylindrical protrusion, with a quantity of 1, and the threaded connection has a lifting lug for easy mold loading and unloading.

[0180] The bulging core 3 has a hollow structure, which is used to support the blank, control the shape of the product, and realize the integrated process of closing, widening and bulging of the part; it includes a hollow conical section and hollow cylindrical sections located at both ends of the conical section; wherein, the large-diameter cylindrical section is sleeved on the outer periphery of the annular protrusion, and the small-diameter cylindrical section is sleeved on the outer periphery of the cylindrical protrusion; there are 4 built-in threaded holes symmetrically distributed along the circumference on the top surface of the cylindrical section, and the large-diameter cylindrical section is connected to the base 1 and the small-diameter cylindrical section is connected to the pressure plate 2 by bolts.

[0181] The closing mold 4 has a hollow structure; the inner cavity is cylindrical and used for closing and forming the straight conical composite cylinder; the annular structure is used to withstand the external pressure transmitted by the pad ring; four threaded through holes are symmetrically distributed along the circumference on the cylindrical structure for installing lifting lugs during mold assembly and for installing thermocouples during hot working; four threaded internal holes are symmetrically arranged along the same circumference on the annular structure for installing lifting lugs during mold assembly and for fixing to the pad ring with bolts during hot working.

[0182] The pad block retainer 5 has a hollow structure for transmitting externally applied pressure to the closing mold; it includes an upper bottom surface, a lower bottom surface, and six support columns threadedly connected to the upper and lower bottom surfaces; wherein, the upper and lower bottom surfaces have annular structures of the same size: six threaded holes are symmetrically distributed on the same circumference of the two bottom surfaces for connecting with the support columns; the two ends of the support columns are threaded, the end face of the support column connected to the upper bottom surface does not protrude from the upper surface of the upper bottom surface, and the end face of the support column connected to the lower bottom surface can protrude from the lower surface of the lower bottom surface; on the lower bottom surface, four threaded holes are symmetrically distributed along the same circumference for connecting with the pad block retainer during the hot working of the part; on the upper bottom surface, four threaded holes are symmetrically distributed along the same circumference for installing lifting lugs during mold assembly.

[0183] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A one-piece molding die for a straight conical composite cylinder, characterized in that, The mold includes a base, an expanded tire core, a pressing plate, and a closing mold and a pad ring, which are rigidly connected from bottom to top on the expanded tire core. The bulging core includes a conical section in the middle, and a large-diameter cylindrical section and a small-diameter cylindrical section at both ends. The conical section is used for bulging the billet to form the conical section of the straight-conical composite cylinder; the small-diameter cylindrical section is used for flaring the billet to form the small-diameter straight section of the straight-conical composite cylinder; the large-diameter cylindrical section is used for closing the billet to form the large-diameter straight section of the straight-conical composite cylinder, wherein the billet is a whole conical billet; The closing mold has a cylindrical inner cavity, which is fitted onto the bulging core and is used to cooperate with the large-diameter cylindrical section of the bulging core to close the blank and form a large-diameter straight cylindrical section of the straight conical composite cylinder. The pad 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 mold to realize the closing of the blank. Before the blank is formed, the inner diameter of the closing mold fitted on the bulging core is smaller than the outer diameter of the end of the whole conical blank to be closed, so that the closing mold does not contact the base. The closing mold moves downward under external pressure and contacts the base, cooperating with the large-diameter cylindrical section of the bulging core to close the blank and form a large-diameter straight cylindrical section of the straight conical composite cylinder. The coefficient of thermal expansion of the bulging tire core is greater than that of the straight tapered composite cylinder.

2. The mold according to claim 1, characterized in that, The large-diameter end of the bulging tire core is threaded to the base, and the small-diameter end is threaded to the clamping plate.

3. The mold according to claim 1, characterized in that, The material of the straight conical composite cylinder is TA15, TC4, or aluminum alloy.

4. The mold according to claim 1, characterized in that, The material of the bulging core is selected from stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, heat-resistant alloy steel, and ceramic materials; And / or, the other parts of the mold are made of one of the following materials: stainless steel, carbon steel, forging die steel, medium silicon molybdenum ductile iron, and heat-resistant alloy steel.

5. The mold according to claim 1, characterized in that, The dimensions of the expanded tire core satisfy the following: L 胎芯 =L 胎芯0 (1+a 胎芯 ·ΔT) (1) L 胎芯0 =R 零件0 *(1+a 零件 ·ΔT) / (1+α 胎芯 ·ΔT) (2) Among them, L 胎芯0 —Outer diameter of the inflated tire core at room temperature; L 胎芯 —Outer diameter of the bulging core at the thermoforming temperature; α 胎芯 —Coefficient of expansion of the tire core wire; ΔT—The difference between thermoforming temperature and room temperature; R 零件0 —Inner diameter of the straight conical composite cylinder at room temperature; α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

6. The mold according to claim 1, characterized in that, The dimensions of the closing mold satisfy the following: R 收口模 =R 收口模0 (1+a 收口模 ·ΔT) (3) R 收口模0 =L 零件0 *(1+a 零件 ·ΔT) / (1+α 收口模 ·ΔT) (4) Among them, R 收口模0 —Inner diameter of the closing mold at room temperature; R 收口模 —The inner diameter of the die at the thermoforming temperature; α 收口模 —Coefficient of linear expansion of the seam trimmer; ΔT—The difference between thermoforming temperature and room temperature; L 零件0 —Outer diameter of the straight conical composite cylinder at room temperature; α 零件 —Coefficient of linear expansion of the straight cone composite cylinder.

7. A method for integrally molding a straight conical composite cylinder, characterized in that, The method employs the mold described in any one of claims 1-5, specifically including: (1) Establish a three-dimensional model of the straight cone composite cylinder, and cut, circle and weld it according to its unfolded material size in the software to obtain the whole cone cylinder blank; (2) The whole conical blank is fitted onto the bulging core of the mold, and the mold is assembled; (3) Heat the mold assembled in step (2), apply pressure to the pad ring, and maintain it; (4) Cool the mold and demold it to obtain the straight cone composite cylinder.

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