Roll bending forming manufacturing method for thin-wall titanium alloy cylindrical part

Abstract

The invention discloses a roll bending forming manufacturing method for a thin-wall titanium alloy cylindrical part. The roll bending forming manufacturing method comprises the steps of material preparation, roll bending forming, shaping and pretreatment before welding, longitudinal seam welding and heat treatment shaping. The roll bending machine is improved in design, a plurality of wedge-shaped cushion blocks are designed on the lower side of the lower roll, the contact surface between the upper wedge-shaped block and the lower wedge-shaped block is a 5-degree conical surface, and the height change of the upper plane and the lower plane of the wedge-shaped blocks, fine adjustment (jacking or loosening) of the height of the lower roll and compensation of the center-to-center distance value of the upper roll and the lower roll are achieved by rubbing the relative positions of the pair of wedge-shaped cushion blocks front and back. Consistency of forming radiuses of a port area and a central area of the cylindrical part is guaranteed, and a standard cylindrical shape is obtained. The heat treatment shaping measure is different from a conventional process, the stainless steel core rod heat treatment tool penetrates into the titanium alloy cylindrical part, heat expansion shaping of the cylindrical part is achieved through the core rod by means of the heat expansion difference of different materials at the high temperature, and it is guaranteed that the outer diameter of the cylindrical part is + / -0.2 mm when the cylindrical part recovers to the room temperature state.

Description

Technical Field

[0001] The present application relates to the technical field of metal processing, and in particular to a method for rolling and forming a thin-walled titanium alloy cylindrical part. Background Art

[0002] With the continuous improvement of material performance requirements in aerospace, automobile manufacturing and other fields, thin-walled titanium alloy sheets have been widely used due to their light weight, high strength, corrosion resistance, high temperature resistance and other characteristics. However, due to the high hardness and poor ductility of titanium alloy materials, and the proneness to uneven deformation, cracking, large deformation rebound and other problems during the bending forming process of large-sized cylindrical parts, it is difficult to form them, resulting in low dimensional accuracy, poor consistency and low yield rate of workpieces.

[0003] In the deployment mechanism of a new energy spacecraft, a titanium alloy sleeve structure is required to deploy the space stack to a position far away from the spacecraft body, and the mechanism needs to achieve the connection and support between the spacecraft platform and the space stack. Therefore, the sleeve structure is the main support link of the deployment and locking mechanism, and its performance directly determines the success or failure of the space mission.

[0004] At present, the workpiece is made of TC4 titanium alloy, with a wall thickness of 2mm, an outer diameter accuracy requirement of Φ616±0.2mm, a roundness requirement of 2mm, a total length of 2700mm, and an overall straightness requirement of 2.7mm. The existing conventional processing methods cannot guarantee the dimensional accuracy and shape and position accuracy of the workpiece, which will ultimately lead to the inability to achieve precise assembly of the product. Therefore, for the mechanism parts with precise assembly requirements and precise matching requirements, it is difficult to meet the requirements by simply using the currently commonly used mechanical processing methods. Summary of the invention

[0005] The present application provides a method for rolling and forming a thin-walled titanium alloy cylindrical part, which achieves high-precision and high-efficiency forming and manufacturing of the titanium alloy cylindrical part by optimizing the rolling process parameters and process flow.

[0006] In a first aspect, a method for rolling and forming a thin-walled titanium alloy cylindrical part is provided, comprising:

[0007] Material preparation: Select thin-walled titanium alloy plates of appropriate thickness and heat treatment status as raw materials, and perform precise shape cutting on the unfolded cylindrical parts;

[0008] Rolling forming: Put the titanium alloy sheet into the rolling machine, and adjust the roller spacing, roller diameter, rolling speed, and rolling radius parameters of the rolling machine so that the titanium alloy sheet is gradually bent into a cylindrical shape under the action of the rollers;

[0009] Shaping and pre-welding treatment: Shaping of the titanium alloy cylindrical parts formed by roll bending, including straightening and trimming, to ensure that the longitudinal weld assembly gap meets the requirements;

[0010] Longitudinal seam welding: welding the longitudinal seams of the cylindrical parts after rolling and shaping;

[0011] Heat treatment shaping: insert the heat treatment tooling into the titanium alloy cylindrical part. The heat treatment tooling is a core rod. The outer circumference of the core rod fits the inner wall of the titanium alloy cylindrical part. The thermal expansion coefficient of the heat treatment tooling is greater than the thermal expansion coefficient of the titanium alloy. The cylindrical part and the heat treatment tooling are heat treated and shaped as a whole.

[0012] In conjunction with the first aspect, in certain implementations of the first aspect, the outer diameter of the heat treatment tooling satisfies:

[0013] D0=D1×(1+α1×ΔT) / (1+α0×ΔT)

[0014] D0—outer diameter of mandrel at room temperature;

[0015] D1—Inner diameter of cylindrical parts at room temperature;

[0016] α1—linear expansion coefficient of titanium alloy;

[0017] α0—Linear expansion coefficient of heat treatment tooling;

[0018] ΔT—the difference between heat setting temperature and room temperature.

[0019] In combination with the first aspect, in certain implementations of the first aspect, the material of the heat treatment tooling is stainless steel.

[0020] In combination with the first aspect, in certain implementations of the first aspect, the post-processing step includes surface treatment, longitudinal seam welding and heat treatment for shaping.

[0021] In combination with the first aspect, in certain implementations of the first aspect, during the heat treatment process, the vacuum heat setting temperature is 680±5° C., and the holding time is 180±10 min.

[0022] In combination with the first aspect, in certain implementations of the first aspect, the rolling bending machine used in the rolling bending forming application is designed with multiple groups of wedge-shaped pads on the lower side of the lower roller, and the multiple groups are arranged along the axial direction of the roller; each group of wedge-shaped pads includes two upper and lower wedge-shaped pads, the upper wedge-shaped pad is arranged on the mounting platform of the lower roller, and the lower wedge-shaped pad is arranged on the rolling bending machine platform; the contact surface between the upper and lower wedge-shaped pads is an inclined surface.

[0023] In combination with the first aspect, in certain implementations of the first aspect, the inclination angle of the inclined surface is 3° to 7°.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the rolling machine for the rolling forming application includes two lower rollers and one upper roller, the diameters of the two lower rollers are 45-55 mm, the center spacing is 70-90 mm, the diameter of the upper roller is 140-160 mm, and the outer circle of the upper roller has 8-12 1 mm × 1 mm grooves distributed circumferentially.

[0025] In combination with the first aspect, in certain implementations of the first aspect, during the rolling process, a three-pass rolling method is adopted, and the center distances between the upper roller and the lower roller are 100 mm for the first pass, 95 mm for the second pass, and 90 mm for the third pass, and the rolling speed of the main roller is 5 mm / s.

[0026] In combination with the first aspect, in certain implementations of the first aspect, during the welding process, the welding current is 165A, the voltage is 10V, and the welding speed is 280mm / min.

[0027] Compared with the prior art, the solution provided by this application includes at least the following beneficial technical effects:

[0028] 1. By optimizing the rolling process parameters and process flow, and adopting a multi-pass, small-deformation rolling method, high-efficiency and high-precision forming of thin-walled titanium alloy large-size cylindrical parts is achieved.

[0029] 2. Through the overall heat treatment shaping process, the dimensional accuracy and shape and position accuracy of the cylindrical parts are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure and process of rolling forming equipment for large-size thin-walled titanium alloy cylindrical parts. DETAILED DESCRIPTION

[0031] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] The present invention provides a method for rolling and forming a thin-walled titanium alloy cylindrical part. The specific steps are as follows.

[0033] Step 1: Material preparation: Select thin-walled titanium alloy plates of appropriate thickness and heat treatment status as raw materials, and perform precise shape cutting on the unfolded cylindrical parts to ensure the deformation plasticity and diameter dimensional accuracy of the material.

[0034] Step 2: Rolling and bending: Place the titanium alloy sheet into Figure 1 In the roll bending machine shown, the titanium alloy sheet is gradually bent into the desired cylindrical shape under the action of the rollers by adjusting the roller spacing, roller diameter, rolling speed, rolling radius and other parameters of the roll bending machine. In the rolling process, a multi-pass, small deformation rolling method is adopted to avoid excessive deformation and cracking of the material.

[0035] Since the springback of titanium alloy plates during cold forming at room temperature is very large, it is necessary to add springback control measures in advance during roll forming. Conventional rolling equipment cannot achieve compensation for the large springback of titanium alloys. The process measure adopted by the present invention is to use an upper roller with an outer diameter much smaller than the inner diameter of the cylindrical part for production. However, this measure will cause the structural aspect ratio of the upper roller to be very large and easy to become unstable. During the actual rolling process, the center area of ​​the upper roller is prone to large deflection (also known as bending concession), causing the distance between the upper and lower rollers to increase, and the cylindrical part presents a drum-shaped shape with a large radius in the middle and small diameters at both ends.

[0036] Therefore, combined with Figure 1 The present invention improves the design of the roll bending machine, designs multiple groups of wedge-shaped pads on the lower side of the lower roller, and the multiple groups are arranged along the axial direction of the roller. Each group of wedge-shaped pads includes two upper and lower wedge-shaped pads, the upper wedge-shaped pad is arranged on the mounting platform of the lower roller, and the lower wedge-shaped pad is arranged on the roll bending machine platform. The contact surface between the upper and lower wedge-shaped pads is a 5° cone surface, that is, the inclination angle of the contact surface relative to the horizontal plane is 5°. During the movement of the upper and lower rollers, the relative positions of a pair of wedge-shaped pads can be rubbed back and forth in a direction perpendicular to the axial direction to achieve the total height change of each group of wedge-shaped pads, fine-tune (lift or relax) the height of the lower roller, compensate for the center distance value of the upper and lower rollers, ensure the consistency of the forming radius of the port area and the center area of ​​the cylindrical part, and obtain a standard cylindrical shape.

[0037] Step 3: Shaping and pre-welding treatment: The titanium alloy cylindrical parts formed by roll bending are shaped, including straightening and trimming, to ensure that the longitudinal weld assembly gap meets the requirements. The cylindrical parts are surface treated before welding to ensure welding requirements.

[0038] Step 4, longitudinal seam welding: The longitudinal welds of the cylindrical parts after rolling and shaping are welded together, and the welding quality and thermal shrinkage consistency of the longitudinal welds are ensured by adjusting the welding parameters.

[0039] Step 5, heat treatment and shaping: Use the embedded bulging heat treatment tooling to heat treat and shape the cylindrical parts as a whole. By accurately designing the outer diameter size of the heat treatment tooling, the final outer diameter size accuracy, contour and straightness of the workpiece are guaranteed. The post-processing steps include surface treatment, longitudinal seam welding and heat treatment shaping.

[0040] The heat treatment shaping measures in the present invention are different from conventional tempering or stress relief heat treatment processes. Instead, a stainless steel mandrel (heat treatment tooling) is inserted into the titanium alloy cylindrical part at room temperature. The thermal expansion difference of different materials at high temperatures (stainless steel> titanium alloy) is used to achieve thermal expansion shaping of the cylindrical part by the mandrel, ensuring that the outer diameter of the cylindrical part is ±0.2mm accurate when it returns to room temperature. Therefore, the outer diameter of the mandrel at room temperature needs to be accurately designed, and the specific calculation process is as follows:

[0041] D0=D1×(1+α1×ΔT) / (1+α0×ΔT)

[0042] D0—outer diameter of mandrel at room temperature;

[0043] D1—Inner diameter of cylindrical parts at room temperature;

[0044] α1—linear expansion coefficient of titanium alloy;

[0045] α0—linear expansion coefficient of stainless steel;

[0046] ΔT—the difference between heat setting temperature and room temperature.

[0047] Example 1

[0048] Step 1: Select 2mm thick TC4M thin-walled titanium alloy plate as the raw material and cut it into 900mm×1931mm plates, a total of 3 pieces.

[0049] Step 2: Place the titanium alloy sheet into the rolling machine, equipped with two lower rollers with a diameter of 50mm and a center spacing of 80mm, and an upper roller with a diameter of 150mm. The outer circle of the upper roller is distributed with 10 1mm×1mm grooves along the circumference to increase the friction between the upper roller and the titanium plate. During the rolling process, three passes of rolling are adopted to achieve the gradual bending of the titanium alloy sheet. The center spacing values ​​of the upper roller and the lower roller are adjusted to 100mm for the first pass, 95mm for the second pass, and 90mm for the third pass, and the main roller rolling speed is 5mm / s.

[0050] Step 3: After rolling and forming, the cylindrical part is shaped to ensure that the longitudinal weld assembly gap is less than 0.5mm.

[0051] Step 4: Clean the surface of the cylindrical part to ensure welding requirements. Perform longitudinal seam welding on the cylindrical part with a welding current of 165A, a voltage of 10V, and a welding speed of 280mm / min to ensure weld quality and shrinkage uniformity.

[0052] Step 5: Finally, the cylindrical part is heat-set as a whole, the vacuum heat-setting temperature is 680±5℃, and the holding time is 180±10min. After the holding time is up, the furnace is cooled to room temperature and the furnace is opened.

[0053] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A method for rolling and forming a thin-walled titanium alloy cylindrical part, characterized in that: include: Material preparation: Select thin-walled titanium alloy plates of appropriate thickness and heat treatment status as raw materials, and perform precise shape cutting on the unfolded cylindrical parts; Rolling forming: Put the titanium alloy sheet into the rolling machine, and adjust the roller spacing, roller diameter, rolling speed, and rolling radius parameters of the rolling machine so that the titanium alloy sheet is gradually bent into a cylindrical shape under the action of the rollers; Shaping and pre-welding treatment: Shaping of the titanium alloy cylindrical parts after roll bending, including straightening and trimming, to ensure that the longitudinal weld assembly gap meets the requirements; Longitudinal seam welding: welding the longitudinal seams of the cylindrical parts after rolling and shaping; Heat treatment shaping: insert the heat treatment tooling into the titanium alloy cylindrical part. The heat treatment tooling is a core rod. The outer circumference of the core rod fits the inner wall of the titanium alloy cylindrical part. The thermal expansion coefficient of the heat treatment tooling is greater than the thermal expansion coefficient of the titanium alloy. The cylindrical part and the heat treatment tooling are heat treated and shaped as a whole.

2. The method according to claim 1, characterized in that The outer diameter of the heat treatment tooling meets the following requirements: D0=D1×(1+α1×ΔT) / (1+α0×ΔT) D0—outer diameter of mandrel at room temperature; D1—Inner diameter of cylindrical parts at room temperature; α1—linear expansion coefficient of titanium alloy; α0—Linear expansion coefficient of heat treatment tooling; ΔT—the difference between heat setting temperature and room temperature.

3. The method according to claim 1, characterized in that: The material of the heat treatment tooling is stainless steel.

4. The method according to claim 1, characterized in that: Post-processing steps include surface treatment, longitudinal seam welding and heat treatment.

5. The method according to claim 1, characterized in that During the heat treatment process, the vacuum heat setting temperature is 680±5℃ and the holding time is 180±10min.

6. The method according to any one of claims 1 to 5, characterized in that The rolling bending machine used in the rolling bending forming application is designed with multiple groups of wedge-shaped pads on the lower side of the lower roller, and the multiple groups are arranged along the axial direction of the roller; each group of wedge-shaped pads includes two upper and lower wedge-shaped pads, the upper wedge-shaped pad is arranged on the mounting platform of the lower roller, and the lower wedge-shaped pad is arranged on the rolling bending machine platform; the contact surface between the upper and lower wedge-shaped pads is an inclined surface.

7. The method according to claim 6, characterized in that The inclination angle of the slope is 3°~7°.

8. The method according to claim 1, characterized in that The rolling machine used for the rolling forming application includes two lower rollers and one upper roller. The diameters of the two lower rollers are both 45-55 mm and the center distance is 70-90 mm. The diameter of the upper roller is 140-160 mm. The outer circle of the upper roller has 8-12 1 mm×1 mm grooves distributed circumferentially.

9. The method according to claim 1, characterized in that: During the rolling process, a three-pass rolling method is adopted. The center distances between the upper roller and the lower roller are 100mm for the first pass, 95mm for the second pass, and 90mm for the third pass. The rolling speed of the main roller is 5mm / s.

10. The method according to claim 1, characterized in that During the welding process, the welding current was 165A, the voltage was 10V, and the welding speed was 280mm / min.

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