Method for Deep Cold Shape Correction of Thin-walled Cylinder

Abstract

The present invention provides a method for deep cold shaping of a thin-walled cylinder, comprising the steps of: S1, taking a thin-walled cylinder to be shaped; S2, performing a tooling positioning process on the thin-walled cylinder; the tooling positioning process comprises: sleeve the thin-walled cylinder on the cylinder part of the deep cold tooling, and make one end of the thin-walled cylinder abut against the shoulder part of the deep cold tooling; S3, performing at least one temperature control process on the thin-walled cylinder; the temperature control process comprises: performing deep cold operation and temperature return operation on the thin-walled cylinder in sequence; the deep cold operation comprises: placing the deep cold working device sleeved with the thin-walled cylinder in a deep cold environment; the temperature return operation comprises: placing the deep cold working device sleeved with the thin-walled cylinder in a temperature return environment. The present invention can improve material properties while ensuring the shaping accuracy, and has high efficiency and low cost.

Description

Technical Field

[0001] The invention relates to the field of metal profile processing, and in particular to a method for deep cold shaping of a thin-walled cylinder. Background Art

[0002] Due to its weak rigidity structural characteristics, thin-walled cylinders are prone to deformation during the manufacturing process such as welding, milling, and heat treatment, resulting in reduced cylinder roundness and generatrix straightness. Existing thin-walled cylinders are mainly shaped mechanically and thermally; however, mechanical shaping of the entire cylinder generally uses a bulging machine to expand the diameter of the block mold to cause the cylinder to undergo plastic deformation to achieve the purpose of shaping, which has high requirements on equipment, low overall accuracy, and a high risk of damage and failure.

[0003] The Chinese invention patent application with publication number CN117505596A discloses a heat treatment shaping method for thin-walled metal parts, which first prepares a shaping tool, then assembles the shaping tool with the thin-walled metal part and performs vacuum heat treatment to achieve shaping; therefore, the patent application mainly adopts a thermal shaping method, through the thermal expansion difference between the core mold and the barrel part, the material softens and relaxes stress at high temperature, thereby obtaining a higher shaping accuracy. However, high temperature conditions can easily weaken product performance, and the thermal shaping process often fails to achieve the best performance of the product material; in addition, the energy consumption required for heating is high, and the thermal expansion coefficient and thermal stability of the mold tooling material are required to be high; therefore, thermal shaping will cause performance loss and high cost.

[0004] In view of this, it is necessary to provide a method for deep cold shaping of thin-walled cylinders to solve or at least alleviate the technical defects of performance loss and high cost caused by thermal shaping. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for deep cold shaping of a thin-walled cylinder, aiming to solve the technical problems of performance loss and high cost caused by the above-mentioned thermal shaping.

[0006] To achieve the above object, the present invention provides a method for deep cold shaping of a thin-walled cylinder, comprising the steps of:

[0007] S1, taking a thin-walled cylinder to be calibrated, wherein the thin-walled cylinder is made of metal and has a deformed structure;

[0008] S2, performing a tooling positioning process on the thin-walled cylinder; the tooling positioning process includes: sleeve the thin-walled cylinder on the cylinder portion of the cryogenic tooling, and make one end of the thin-walled cylinder abut against the shoulder portion of the cryogenic tooling; the cylinder portion and the shoulder portion of the cryogenic tooling are vertically arranged;

[0009] S3, performing at least one temperature control treatment on the thin-walled cylinder; the temperature control treatment comprises: sequentially performing a deep cooling operation and a temperature return operation on the thin-walled cylinder;

[0010] The cryogenic operation includes: placing the cryogenic device provided with the thin-walled cylinder in a cryogenic environment, wherein the temperature of the cryogenic environment is not higher than -130°C;

[0011] The temperature recovery operation includes: placing the cryogenic device provided with the thin-walled cylinder in a temperature recovery environment, wherein the temperature of the temperature recovery environment is not lower than 0°C.

[0012] Furthermore, the thin-walled cylinder and the cylinder portion of the cryogenic tooling have clearance fit at room temperature; the cylinder portion of the cryogenic tooling and the thin-walled cylinder of standard size have a preset clearance at room temperature;

[0013] The calculated value of the preset gap is calculated according to formula 1;

[0014] Formula 1: g = (α 零件 -α 工装 )×R 零件 ×ΔT;

[0015] In the formula 1, g is the calculated value of the preset gap, in mm; α 零件 is the thermal expansion coefficient of the thin-walled cylinder, in 1 / °C; α 工装 is the thermal expansion coefficient of the barrel of the cryogenic tooling, in units of 1 / °C; R 零件 is the outer contour radius value of the thin-walled cylinder of standard size, in mm; ΔT is the temperature difference between room temperature and the cryogenic environment, in °C;

[0016] Among them, when the calculated value of the preset gap is less than 0.2 mm, 0.2 mm is taken as the design value of the preset gap; when the calculated value of the preset gap is not less than 0.2 mm, the calculated value of the preset gap is taken as the design value of the preset gap.

[0017] Furthermore, the thermal expansion coefficient of the cryogenic tooling is smaller than that of the thin-walled cylinder.

[0018] Furthermore, the cylinder portion of the cryogenic tooling and the thin-walled cylinder are matched in shape; and the tooling positioning process is performed at room temperature.

[0019] Furthermore, the shoulder portion of the cryogenic tooling is arranged around the bottom end of the cylinder portion.

[0020] Furthermore, during the cryogenic operation, the cryogenic environment is composed of liquid nitrogen, and the cryogenic tooling provided with the thin-walled cylinder is immersed in the liquid nitrogen.

[0021] Furthermore, the insulation time of the deep freezing operation is 0.8-3h.

[0022] Furthermore, the temperature of the temperature recovery environment is room temperature, and the insulation time of the temperature recovery operation is not less than 10 minutes.

[0023] Furthermore, the temperature of the temperature recovery environment is 80-300° C., and the insulation time of the temperature recovery operation is 10-60 minutes.

[0024] Furthermore, the step S3 also includes: unloading the thin-walled cylinder from the cryogenic tooling at room temperature.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] The present invention can improve material performance while ensuring the accuracy of shape correction; since cryogenic operation can improve material density and improve microstructure and macro-micro residual stress redistribution, the present invention also uses the creep / stress relaxation characteristics of metal for shape correction, which will not only not reduce material performance, but also significantly improve the performance of some materials. Specifically, the invention uses conventional steel with low thermal expansion coefficient as the cryogenic tooling, and the thin-walled cylinder to be shaped is sleeved on the outside of the cryogenic tooling, and placed in a cryogenic environment and kept for a certain period of time. The cylinder shrinkage and cryogenic treatment stress relaxation characteristics are used to achieve high-precision shape correction of the thin-walled cylinder; at the same time, the cryogenic operation and rewarming operation in the present invention can also improve the performance of the material, which is conducive to the high-performance and precise manufacturing of thin-walled cylinders. In addition, the present invention has high efficiency, short process flow, simple operation, fast heat transfer and high efficiency of cryogenic operation and rewarming operation; and the cost of the present invention is low. The present invention only needs to use cryogenic tooling as a mold for shape correction, which greatly reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the state of the thin-walled cylinder and the cryogenic tooling after the tooling positioning treatment in the present invention;

[0029] Figure 2 It is a schematic diagram of the state of the thin-walled cylinder and the cryogenic tooling after the cryogenic operation in the present invention;

[0030] Figure 3 It is a schematic diagram of the state of the thin-walled cylinder and the deep-cold tooling after the temperature recovery operation in the present invention.

[0031] Figure numerals: 1, thin-walled cylinder; 2, cylinder portion; 3, shoulder portion.

[0032] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention are familiar to those skilled in the art and the description of the present invention, and any methods, equipment and materials of the prior art similar or equivalent to the methods, equipment and materials described in the embodiments of the present invention can also be used to implement the present invention.

[0036] See also Figure 1-3 As shown, the present invention provides a method for deep cold shaping of a thin-walled cylinder, comprising the steps of:

[0037] S1, take a thin-walled cylinder 1 to be shaped, the thin-walled cylinder 1 is made of metal, specifically, the thin-walled cylinder 1 may include at least one of aluminum alloy, magnesium alloy and titanium alloy thin-walled cylinder 1; or include a light alloy cylinder structure obtained by extrusion, casting, spinning, etc.; or the thin-walled cylinder 1 may include an additive product, such as an additive aluminum alloy product. In addition, the thin-walled cylinder 1 to be shaped is deformed and has residual stress; as an illustration of the thin-walled cylinder 1, the diameter-to-thickness ratio (ratio of diameter to thickness) of the thin-walled cylinder 1 is generally ≥50, and the cylinder thickness is generally not more than 20 mm.

[0038] S2, performing a tooling positioning process on the thin-walled cylinder 1; the tooling positioning process includes: sleeve the thin-walled cylinder 1 on the cylinder portion 2 of the cryogenic tooling, and make one end of the thin-walled cylinder 1 abut against the shoulder portion 3 of the cryogenic tooling, at this time, the thin-walled cylinder 1 and the cryogenic tooling are collectively referred to as a part tooling.

[0039] The end of the thin-walled cylinder 1 that abuts against the shoulder 3 of the cryogenic tooling is the lower end, the outer side surface of the cylinder 2 is the supporting profile, and the end surface of the shoulder 3 that abuts against the thin-walled cylinder 1 is the shoulder surface. The cryogenic tooling can be understood as an internal support mold; the cylinder 2 and the shoulder 3 of the cryogenic tooling are vertically arranged, and the cylinder 2 and the shoulder 3 of the cryogenic tooling are arranged up and down, and are usually integrally formed; specifically, the cylinder 2 extends from top to bottom to the shoulder 3, and is fixedly connected to the shoulder 3, and the shoulder 3 is arranged around the bottom end of the cylinder 2.

[0040] In the present invention, the thin-walled cylinder 1 is inserted into the deep freezing tooling, and is positioned and pre-clamped by the shoulder surface at the bottom of the deep freezing tooling, so as to ensure that the cylinder will not be twisted, rotated, or detached from the tooling during subsequent deep freezing and warming operations; in a specific scenario, the positioning method of the deep freezing tooling can also be determined according to the characteristics of the thin-walled cylinder 1 and the benchmark requirements.

[0041] In the present invention, the thin-walled cylinder 1 and the cylinder part 2 of the cryogenic tooling have clearance fit at room temperature; the cylinder part 2 of the cryogenic tooling and the thin-walled cylinder 1 of standard size have a preset clearance at room temperature; that is, when manufacturing the cryogenic tooling, it is necessary to design it according to the preset clearance between the cylinder part 2 of the cryogenic tooling and the thin-walled cylinder 1 of standard size at room temperature. In the present invention, the thin-walled cylinder 1 of standard size refers to the size of the thin-walled cylinder 1 when it is designed; the calculated value of the preset clearance is calculated according to Formula 1.

[0042] Formula 1: g = (α 零件 -α 工装 )×R 零件 ×ΔT; in the formula 1, g is the calculated value of the preset gap, in mm; α 零件 is the thermal expansion coefficient of the thin-walled cylinder, in 1 / °C; α 工装 is the thermal expansion coefficient of the barrel of the cryogenic tooling, in units of 1 / °C; R 零件 is the outer contour radius value of the thin-walled cylinder of standard size (equivalent to the outer contour radius value of the thin-walled cylinder in the target state), in mm; ΔT is the temperature difference between room temperature and the deep cold environment, in °C.

[0043] When the calculated value of the preset gap is less than 0.2 mm, 0.2 mm is taken as the design value of the preset gap; when the calculated value of the preset gap is not less than 0.2 mm, the calculated value of the preset gap is taken as the design value of the preset gap. The present invention designs the cryogenic tooling according to the design value of the preset gap; that is, the gap between the cylinder part 2 of the cryogenic tooling and the thin-walled cylinder 1 of standard size at room temperature is not less than 0.2 mm.

[0044] In the present invention, the tool positioning treatment is carried out at room temperature; the thermal expansion coefficient of the cryogenic tool is smaller than that of the thin-walled cylinder 1, that is, the thermal expansion coefficient of the material used for the cryogenic tool (cylinder part 2 and shoulder part 3) is smaller than that of the material used for the thin-walled cylinder 1.

[0045] In the present invention, the cylinder part 2 of the cryogenic tool and the thin-walled cylinder 1 are matched in shape; both ends of the thin-walled cylinder 1 are open; the thin-walled cylinder 1 can include one of a cylindrical cylinder and a conical cylinder. That is, the thin-walled cylinder 1 includes a cylinder and a cone and has complex structural features; when it has complex structural features, the positioning and clamping method of the cryogenic tool can be designed according to the specific structural features and reference characteristics.

[0046] S3, performing at least one temperature control treatment on the thin-walled cylinder 1; then, unloading the thin-walled cylinder 1 from the deep-freezing tooling at room temperature.

[0047] The temperature control treatment may be performed once or multiple times. When the shape correction effect achieved by the temperature control treatment once is not good, the temperature control treatment may be performed multiple times. The temperature control treatment includes: performing deep cooling operation and temperature return operation on the thin-walled cylinder 1 in sequence.

[0048] In the present invention, the cryogenic operation includes: placing the cryogenic tooling with the thin-walled cylinder 1 in a cryogenic environment, so that the thin-walled cylinder 1 and the cryogenic tooling reach an interference fit state; the temperature of the cryogenic environment is not higher than -130°C, and can further be -130°C to -200°C; the insulation time of the cryogenic operation can be 0.8-3h.

[0049] In the cryogenic operation, the cryogenic tooling with the thin-walled cylinder 1 can be placed in a cryogenic environment by immersion or environmental box method, and the immersion method has higher production efficiency. In the present invention, the cryogenic environment can be composed of liquid nitrogen so that the temperature of the cryogenic environment is maintained at about -196°C; preferably, the cryogenic tooling with the thin-walled cylinder 1 is immersed in the liquid nitrogen.

[0050] When performing the cryogenic operation, the cryogenic tooling with the thin-walled cylinder 1 is placed in the cryogenic environment, so that the thin-walled cylinder 1 shrinks and fits tightly against the cryogenic tooling, generating a certain bulging force or plastic deformation; then it is kept in the cryogenic environment for a period of time. Due to the large number of vacancies / dislocations / stacking faults inside the cylinder material and the uneven distribution of the microstructure, the material will undergo stress relaxation and microstructural evolution, and the material will often become denser and some defects such as microvoids will be healed, thereby achieving the purpose of providing product performance.

[0051] In the present invention, the temperature recovery operation includes: placing the cryogenic device with the thin-walled cylinder 1 in a temperature recovery environment; the temperature of the temperature recovery environment is not lower than 0°C, specifically not lower than room temperature, and not higher than the recrystallization temperature of the material used for the thin-walled cylinder 1; that is, in the present invention, the temperature of the temperature recovery environment can be from room temperature to the recrystallization temperature of the material used for the thin-walled cylinder 1, generally less than 300°C, and can be 25-300°C. In addition, the insulation time of the temperature recovery operation is usually not less than 10 minutes, and can further be 10-60 minutes.

[0052] Specifically, the temperature recovery operation can be performed in any of the following ways: room temperature, atmosphere heating furnace, and high-temperature medium immersion. That is, the temperature recovery operation generally adopts room temperature and above; when a high-temperature environment is adopted, it can be controlled by the atmosphere temperature or by the high-temperature liquid medium temperature; in specific operations, the temperature recovery operation is preferably performed in a warm furnace; that is, when the ambient temperature reaches the target temperature recovery temperature, the deep cold working device with the thin-walled cylinder 1 is placed in the furnace. It should be noted that after the deep cold operation, the deep cold working device with the thin-walled cylinder 1 should be quickly transferred to the temperature recovery environment; the transfer time of the temperature recovery operation is less than 5s, that is, the thin-walled cylinder 1 is transferred from the deep cold environment to the temperature recovery environment within 5s.

[0053] As an illustration of multiple embodiments of the present invention, the temperature of the warming environment can be room temperature or other temperatures higher than room temperature; for example, the temperature of the warming environment is room temperature, and the duration of the warming operation is not less than 10 minutes or not less than 30 minutes; the temperature of the warming environment is 80-300°C, and the duration of the warming operation is 10-60 minutes. When the temperature of the warming environment is 80-300°C, after the warming operation is completed, the cryogenic tooling with the thin-walled cylinder 1 can be placed at room temperature, and when the entire cryogenic tooling with the thin-walled cylinder 1 is at room temperature or close to room temperature, the thin-walled cylinder 1 can be unloaded from the cryogenic tooling.

[0054] After the cryogenic operation is completed, the thin-walled cylinder 1 and the cryogenic tooling are quickly warmed up at room temperature or high temperature, and the "reverse quenching" effect can be further utilized to reduce the residual stress of the cylinder structure; since the thermal expansion coefficient of the cylinder material is greater than that of the tooling material, the cylinder rebounds evenly after warming up to obtain a high-precision cylinder and is easy to unload and remove.

[0055] As a supplementary explanation, in the present invention, the thin-walled cylinder 1 can be subjected to pre-treatment processes such as mechanical treatment, heat treatment, and vibration aging before cryogenic shaping to obtain better cryogenic shaping accuracy and performance. After cryogenic shaping, the thin-walled cylinder 1 can be subjected to post-treatment processes such as vibration aging, surface treatment, heat treatment, and mechanical processing to ensure product delivery quality requirements.

[0056] In the present invention, continue to refer to Figure 1-3 As shown, Figure 1 In the process, the thin-walled cylinder 1 is in an initial state during the tooling positioning process, and its structure is deformed and has residual stress; Figure 2 In the process, the thin-walled cylinder 1 is in a deep-cold state after the deep-cold operation, and its stress is relaxed and its structure is improved; Figure 3 In the embodiment, the thin-walled cylinder 1 is in the final state after the temperature recovery operation, and has high precision, high performance and low stress. In this way, the present invention realizes high-precision shape correction of the thin-walled cylinder 1 in view of the shortcomings of loss of thermal expansion shape correction performance, high cost and narrow application scope, and the strength and wear resistance of the processed material are significantly improved, the cost is further reduced, and the application scope is further expanded.

[0057] The following are specific examples of the present invention:

[0058] Example 1

[0059] A method for deep cooling and correcting the shape of a thin-walled cylinder, comprising the following steps:

[0060] S1, take the thin-walled cylinder to be shaped. The thin-walled cylinder used in this embodiment is an additive AlSi10Mg aluminum alloy deposited cabin structure. Due to the uneven temperature of the cylinder during the laser additive forming process, the structure is deformed into an elliptical shape; the design size (standard size) of the thin-walled cylinder contour is 200mm in diameter × 3mm in thickness × 200mm in height; the state of the thin-walled cylinder to be shaped is shown in Table 1.

[0061] Table 1 Status of thin-walled cylinder to be calibrated

[0062]

[0063] In this embodiment, the thin-walled cylinder to be shaped is subjected to a room temperature tensile performance test, and the tensile strength is 325 MPa, the yield strength is 229 MPa, and the elongation after break is 6%; the thin-walled cylinder to be shaped is subjected to a 200°C high temperature tensile performance test, and the tensile strength is 232 MPa, the yield strength is 201 MPa, and the elongation after break is 9%.

[0064] S2, use cryogenic tooling to perform tooling positioning processing on the thin-walled cylinder.

[0065] In this embodiment, the cryogenic tooling has a cylindrical portion and a shoulder portion; the cylindrical portion and the thin-walled cylinder are matched in shape, and the cylindrical portion is arranged vertically; the shoulder portion is arranged around the cylindrical portion in the horizontal direction, is perpendicular to the cylindrical portion, and is fixedly connected to the bottom end of the cylindrical portion, and the upper end surface of the shoulder portion is the shoulder surface.

[0066] In this embodiment, the implementation process of the tooling positioning treatment is: at room temperature, a thin-walled cylinder is sleeved on the cylinder portion of the cryogenic tooling, and the lower end of the thin-walled cylinder is abutted against the shoulder surface of the cryogenic tooling.

[0067] In this embodiment, the material of the thin-walled cylinder is AlSi10Mg, and the thermal expansion coefficient is 23×10 -6 / ℃, the material of the cryogenic tooling is Invar steel, and the thermal expansion coefficient is 1.5×10 -6 / ℃; the gap between the cylinder of the cryogenic tooling and the thin-walled cylinder of standard size at room temperature is controlled to be 0.475mm, and the cryogenic tooling is designed based on this.

[0068] S3, performing a temperature control treatment on the thin-walled cylinder (the number of cycles is 1); then, at room temperature, the thin-walled cylinder in the room temperature state is unloaded from the deep-cold tooling to obtain a calibrated thin-walled cylinder.

[0069] In this embodiment, the process of temperature control treatment is: performing deep cooling operation and temperature recovery operation on the thin-walled cylinder in sequence.

[0070] The process of cryogenic operation is: immerse the cryogenic tooling with a thin-walled cylinder in liquid nitrogen (the cryogenic temperature is about -196°C), the holding time of the cryogenic operation (cryogenic time) is 2 hours, and the thin-walled cylinder and the cryogenic tooling reach an interference fit state during the cryogenic operation.

[0071] The process of the temperature recovery operation is: keep the deep-cold tooling equipped with a thin-walled cylinder at the temperature of room temperature for 1 hour (temperature recovery time).

[0072] In this embodiment, the state of the thin-walled cylinder after shape correction is shown in Table 2.

[0073] Table 2 The state of thin-walled cylinder after correction

[0074]

[0075] In this embodiment, the thin-walled cylinder after shape correction is subjected to a room temperature tensile performance test, and the tensile strength is 343Mpa, the yield strength is 246Mpa, and the elongation after break is 10%; the thin-walled cylinder after shape correction is subjected to a 200°C high temperature tensile performance test, and the tensile strength is 268Mpa, the yield strength is 220Mpa, and the elongation after break is 15%.

[0076] Example 2

[0077] 1. Take the thin-walled cylinder to be shaped in Example 1 and anneal it at 280°C for 2 hours to obtain an annealed thin-walled cylinder, which is named annealed state.

[0078] 2. Compared with Example 1, the deep cooling temperature, deep cooling time, reheating temperature, reheating time, and number of cycles are adjusted according to the parameters in Table 3, and the other conditions are the same as those in Example 1. The calibrated thin-walled cylinders are obtained and are named deep cooling state 1, deep cooling state 2, deep cooling state 3, deep cooling state 4, deep cooling state 5, and deep cooling state 6, respectively.

[0079] In this embodiment, the thin-walled cylinder after shape correction is subjected to a high-temperature tensile property test at 200°C; the test results of the annealed and shape-corrected thin-walled cylinder are shown in Table 3.

[0080] Table 3 200℃ high temperature tensile test results after different treatments

[0081]

[0082] It can be seen from Table 3 that after deep cooling and temperature recovery cycle treatment under different parameters, the 200℃ high temperature tensile performance meets the technical indicators required for additive thin-walled cylinders, with tensile strength ≥250MPa, yield strength ≥200MPa, and elongation after fracture ≥10%, which fully meets the product requirements. Compared with the conventional 280℃ annealing process for 2h, the yield strength and tensile properties are significantly better than those of the conventional annealing treatment state.

[0083] Example 3

[0084] A method for deep cooling and correcting the shape of a thin-walled cylinder, comprising the following steps:

[0085] S1, take the thin-walled cylinder to be shaped. The thin-walled cylinder used in this embodiment is a T15 titanium alloy welded thin-walled cylinder with a deformed structure and an elliptical shape. The design dimensions (standard dimensions) of the thin-walled cylinder outline are 360 ​​mm in diameter × 1.2 mm in thickness × 300 mm in height. The state of the thin-walled cylinder to be shaped is shown in Table 4.

[0086] Table 4 Status of thin-walled cylinder to be calibrated

[0087]

[0088] In this embodiment, the room temperature tensile property test is carried out on the thin-walled cylinder to be shaped, and the tensile strength is 1015 MPa, the yield strength is 973 MPa, and the elongation after fracture is 11%.

[0089] S2, use cryogenic tooling to perform tooling positioning processing on the thin-walled cylinder.

[0090] In this embodiment, the cryogenic tooling has a cylindrical portion and a shoulder portion; the cylindrical portion and the thin-walled cylinder are matched in shape, and the cylindrical portion is arranged vertically; the shoulder portion is arranged around the cylindrical portion in the horizontal direction, is perpendicular to the cylindrical portion, and is fixedly connected to the bottom end of the cylindrical portion, and the upper end surface of the shoulder portion is the shoulder surface.

[0091] In this embodiment, the implementation process of the tooling positioning treatment is: at room temperature, a thin-walled cylinder is sleeved on the cylinder portion of the cryogenic tooling, and the lower end of the thin-walled cylinder is abutted against the shoulder surface of the cryogenic tooling.

[0092] In this embodiment, the material of the thin-walled cylinder is T15 titanium alloy, and the thermal expansion coefficient is 8.6×10 -6 / ℃, the material of the cryogenic tooling is Invar steel, and the thermal expansion coefficient is 1.5×10 -6 / ℃; the gap between the cylinder of the cryogenic tooling and the thin-walled cylinder of standard size at room temperature is controlled to be 0.28mm, and the cryogenic tooling is designed based on this.

[0093] S3, performing a temperature control treatment on the thin-walled cylinder; then, at room temperature, unloading the thin-walled cylinder from the deep-cold tooling to obtain a calibrated thin-walled cylinder.

[0094] In this embodiment, the process of temperature control treatment is: performing deep cooling operation and temperature recovery operation on the thin-walled cylinder in sequence.

[0095] The process of cryogenic operation is: immerse the cryogenic tooling with a thin-walled cylinder in liquid nitrogen (the cryogenic temperature is about -196°C), the insulation time of the cryogenic operation is 2 hours, and the thin-walled cylinder and the cryogenic tooling reach an interference fit state during the cryogenic operation.

[0096] The process of the temperature recovery operation is: keep the deep-cold tooling equipped with a thin-walled cylinder at the temperature of room temperature for 1 hour.

[0097] In this embodiment, the state of the thin-walled cylinder after shape correction is shown in Table 5.

[0098] Table 5 Status of thin-walled cylinder after correction

[0099]

[0100] In this embodiment, the room temperature tensile property test is performed on the thin-walled cylinder after shape correction, and the tensile strength is 1028 MPa, the yield strength is 975 MPa, and the elongation after fracture is 11%.

[0101] Comparative Example 1

[0102] Take the thin-walled cylinder to be shaped in Example 3, put the thin-walled cylinder on the lining tooling, and keep it at 750°C for 3 hours to obtain the shaped thin-walled cylinder; the thermal expansion coefficient of the lining tooling is greater than the thermal expansion coefficient of the thin-walled cylinder.

[0103] The room temperature tensile properties test of the thin-walled cylinder after shape correction showed that the tensile strength was 985MPa, the yield strength was 940MPa, and the elongation after break was 12%.

[0104] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for deep cold shaping of a thin-walled cylinder, characterized in that: Includes steps: S1, taking a thin-walled cylinder to be calibrated, wherein the thin-walled cylinder is made of metal, has a deformed structure, and has residual stress; the diameter-to-thickness ratio of the thin-walled cylinder is ≥50, and the thickness of the thin-walled cylinder is not more than 20 mm; The thin-walled cylinder is an additive product; S2, performing tooling positioning processing on the thin-walled cylinder; The tooling positioning process includes: sleeve the thin-walled cylinder on the cylinder part of the cryogenic tooling, and make one end of the thin-walled cylinder abut against the shoulder part of the cryogenic tooling; the cylinder part and the shoulder part of the cryogenic tooling are arranged vertically; the thermal expansion coefficient of the cryogenic tooling is smaller than that of the thin-walled cylinder; S3, performing at least one temperature control treatment on the thin-walled cylinder; the temperature control treatment comprises: sequentially performing a deep cooling operation and a temperature return operation on the thin-walled cylinder; The cryogenic operation comprises: placing the cryogenic device provided with the thin-walled cylinder in a cryogenic environment; the temperature of the cryogenic environment is not higher than -130°C, and the insulation time of the cryogenic operation is 0.8-3h; The reheating operation includes: placing the cryogenic device with the thin-walled cylinder in a reheating environment; the temperature of the reheating environment is room temperature or 80-300° C., and is not higher than the recrystallization temperature of the material used for the thin-walled cylinder; When the temperature of the temperature recovery environment is room temperature, the insulation time of the temperature recovery operation is not less than 30 minutes; when the temperature of the temperature recovery environment is 80-300°C, the insulation time of the temperature recovery operation is 10-60 minutes; The thin-walled cylinder and the cylinder part of the cryogenic tooling have clearance fit at room temperature; the cylinder part of the cryogenic tooling and the thin-walled cylinder of standard size have a preset clearance at room temperature; The calculated value of the preset gap is calculated according to formula 1; Formula 1: g = (α 零件 -α 工装 )×R 零件 ×ΔT; In the formula 1, g is the calculated value of the preset gap, in mm; α 零件 is the thermal expansion coefficient of the thin-walled cylinder, in 1 / °C; α 工装 is the thermal expansion coefficient of the barrel of the cryogenic tooling, in units of 1 / °C; R 零件 is the outer contour radius value of the thin-walled cylinder of standard size, in mm; ΔT is the temperature difference between room temperature and the cryogenic environment, in °C; Among them, when the calculated value of the preset gap is less than 0.2 mm, 0.2 mm is taken as the design value of the preset gap; when the calculated value of the preset gap is not less than 0.2 mm, the calculated value of the preset gap is taken as the design value of the preset gap.

2. The method for deep cold shaping of a thin-walled cylinder according to claim 1, characterized in that: The cylinder part of the deep-freezing tool and the thin-walled cylinder are matched in shape; and the tool positioning process is performed at room temperature.

3. The method for deep cold shaping of a thin-walled cylinder according to claim 1, characterized in that: The shoulder portion of the deep-cold tooling is arranged around the bottom end of the cylinder portion.

4. The method for deep cold shaping of a thin-walled cylinder according to claim 1, characterized in that: During the cryogenic operation, the cryogenic environment is composed of liquid nitrogen, and the cryogenic tooling provided with the thin-walled cylinder is immersed in the liquid nitrogen.

5. The method for deep cold shaping of a thin-walled cylinder according to any one of claims 1 to 4, characterized in that: The step S3 further includes: unloading the thin-walled cylinder from the cryogenic tooling at room temperature.

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