A seamless titanium alloy tube for aviation hydraulic system and its preparation method

Abstract

The present invention discloses a seamless titanium alloy tube for an aviation hydraulic system and a preparation method thereof. The preparation method of the seamless titanium alloy tube for an aviation hydraulic system comprises the following steps: S1, providing a seamless titanium alloy tube blank, the structure of the tube blank being an equiaxed structure; S2, cold rolling the tube blank to obtain a seamless titanium alloy tube; wherein the wall thickness reduction rate of the cold rolling treatment is controlled to be greater than 80%, and the total Q value is greater than 0.88, so that the shrinkage strain ratio of the seamless titanium alloy tube is controlled to be 1.3~3.5; the wall thickness reduction rate is the difference between the wall thickness of the seamless titanium alloy tube and the wall thickness of the tube blank, and Q is the ratio of the relative wall thickness reduction before and after the cold rolling of the tube to the relative reduction in the outer diameter. The present invention can control the CSR value of the titanium alloy tube to be between 1.3 and 3.5, avoid thinning of the tube after bending and cracking during flattening, and improve the safety and reliability of use.

Description

Technical Field

[0001] The invention relates to a method for preparing a seamless titanium alloy tube, in particular to a method for preparing a seamless titanium alloy tube for an aviation hydraulic system. Background Art

[0002] Seamless titanium alloy pipes have the characteristics of high specific strength, strong corrosion resistance, good heat resistance, good low temperature performance, low elastic modulus and thermal conductivity, high chemical activity, good biocompatibility, etc. They are widely used in nuclear power, marine engineering, aerospace and other fields. Seamless titanium alloy pipes used in aviation hydraulic systems have high requirements for dimensional accuracy and performance. Among them, the shrinkage strain ratio (CSR) is an important indicator. It characterizes the ability of aviation hydraulic pipes to resist wall thickness thinning during bending deformation and is a key performance indicator of aviation hydraulic pipes. The control of CSR value is the difficulty of the cold rolling process of titanium alloy pipes, and the CSR value directly affects the performance of the seamless titanium alloy pipes obtained by rolling, and also determines whether the titanium alloy pipes obtained meet the requirements of seamless titanium alloy pipes for aviation hydraulic systems. Summary of the invention

[0003] The present invention relates to a method for preparing a seamless titanium alloy tube for an aviation hydraulic system, which can control the CSR value of the titanium alloy tube to be between 1.3 and 3.5, avoid thinning of the tube after bending and cracking when flattening, and improve the safety and reliability of use. The present invention also relates to a seamless titanium alloy tube for an aviation hydraulic system obtained by the above preparation method.

[0004] A first aspect of the present invention provides a method for preparing a seamless titanium alloy tube for an aviation hydraulic system, comprising the following steps:

[0005] S1. providing a seamless titanium alloy tube blank, wherein the structure of the tube blank is an equiaxed structure;

[0006] S2, cold rolling the tube blank to obtain a seamless titanium alloy tube;

[0007] Among them, the wall thickness reduction rate of the cold rolling treatment is controlled to be greater than 80%, and the total Q value is greater than 0.88, so that the shrinkage strain ratio of the seamless titanium alloy tube is controlled to be 1.3~3.5; the wall thickness reduction rate is the difference between the wall thickness of the seamless titanium alloy tube and the wall thickness of the tube blank, and Q is the ratio of the relative wall thickness reduction before and after cold rolling of the tube to the relative reduction in outer diameter.

[0008] In a preferred embodiment, in step S1, the wall thickness of the tube blank is greater than 3 mm.

[0009] In a preferred embodiment, in step S1, the outer diameter of the tube blank is 50-80 mm. That is, the outer diameter of the selected initial tube blank can be selected from any value in the range of 50-80 mm, for example: 50 mm, 52 mm, 55 mm, 60 mm, 65 mm, 70 mm, 72 mm, 75 mm, 78 mm or 80 mm. In a more preferred embodiment, in step S1, the outer diameter of the tube blank is 55-70 mm.

[0010] In a preferred embodiment, in step S2, the shrinkage strain ratio is adjusted to 1.3-3.5 by controlling the structure of the tube blank to be an equiaxed structure and adjusting the wall thickness reduction rate.

[0011] In a preferred embodiment, in step S2, the Q value is made greater than 0.88, 0.90 or 0.97 by adjusting the wall thickness reduction rate.

[0012] In a preferred embodiment, the cold rolling treatment includes multiple cold rolling processes, and the wall thickness reduction rate of each cold rolling process is controlled to be 20%~60%, and the Q value is 0.5~2.00.

[0013] In a preferred embodiment, the specifications of the seamless titanium alloy tube are Φ6×0.6mm, Φ8×0.7mm, Φ10×0.9mm or Φ12×1mm.

[0014] In a preferred embodiment, the preparation method further comprises step S3:

[0015] The seamless titanium alloy tube is annealed, cleaned and subjected to flaw detection to obtain the seamless titanium alloy tube for the aviation hydraulic system.

[0016] The present invention also provides a seamless titanium alloy tube for an aviation hydraulic system, which is prepared by the preparation method described above.

[0017] The CSR value of the seamless titanium alloy tube is precisely controlled to satisfy the following condition: 1.3≤CSR≤3.5.

[0018] The present invention adopts the above scheme and has the following advantages:

[0019] The preparation method of the seamless titanium alloy tube for aviation hydraulic system of the present invention adopts cold rolling process to the selected seamless titanium alloy tube blank (using equiaxed structure), and in the cold rolling process, by controlling the wall thickness thinning rate of the tube to be greater than 80%, the total Q value is greater than 0.88, so that the shrinkage strain ratio of the seamless titanium alloy tube is controlled to be 1.3~3.5, and the CSR value can be controlled more accurately to meet the requirements of the seamless titanium alloy tube for aviation hydraulic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments 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 these drawings without paying creative work.

[0021] Figure 1 Microscope photograph of seamless titanium alloy tube with basketweave structure.

[0022] Figure 2 This is a microscope photograph of a seamless titanium alloy tube with equiaxed structure used in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] The CSR value is short for shrinkage strain ratio, which characterizes the ability of aviation hydraulic pipes to resist wall thickness thinning during bending deformation. It is a key performance indicator of aviation hydraulic pipes. The CSR value must meet the following requirements: 1.3≤CSR≤3.5. When the CSR value is less than 1.3, the wall thickness of the pipe is easy to thin during bending deformation, affecting the safety of use; when the CSR value is greater than 3.5, the pipe is easy to crack during the flattening test, affecting the reliability of the pipe and the pipe joint after connection. According to the experience of cold rolling of pipes, the Q value determines the size of the CSR value, so it is very important to design the Q value scientifically and reasonably. Definition of Q value: The ratio of the relative thinning of the wall thickness before and after cold rolling of the pipe to the relative reduction of the outer diameter. The calculation formula is as shown in Formula 1:

[0025] Q value = (t0-t1)D0 / [(D0-D1)t0] Formula 1

[0026] Where: t0 is the initial wall thickness of the pipe,

[0027] t1 is the wall thickness of the tube after cold rolling,

[0028] D0 is the initial outer diameter of the pipe,

[0029] D1 is the outer diameter of the tube after cold rolling.

[0030] From formula 1, it can be seen that when the outer diameter and wall thickness of the finished tube are determined, the initial outer diameter and wall thickness of the tube together affect the Q value, so the Q value is difficult to control accurately, resulting in the CSR value being difficult to control. This embodiment provides the following control method, which controls the CSR value to meet the requirements by controlling the Q value.

[0031] (1) First, the initial tube wall thickness t0 is kept constant and the initial tube outer diameter D0 is changed. When the initial tube structure is a basket structure (such as Figure 1 As shown in Table 1 below), taking the rolled finished tube Φ6×0.6mm as an example, it is found that as the initial outer diameter of the tube changes, the CSR value changes greatly, and the value is unstable and fluctuates greatly. Therefore, the initial organization of the tube should not be a basket organization. After research and exploration, the inventors found that when the initial organization of the tube is changed to an equiaxed organization (such as Figure 2 As shown in the figure, it is found that as the outer diameter of the tube changes, the CSR value fluctuates in a small range and the value is stable. Therefore, the initial organization of the tube is selected as equiaxed organization.

[0032] Table 1 The initial tube wall thickness remains unchanged, the tube is basketweave and equiaxed, and the CSR value of the finished product Φ6×0.6mm

[0033]

[0034] (2) The initial microstructure of the tube is determined to be equiaxed, the initial wall thickness t0 of the tube is kept constant, and the initial outer diameter of the tube is changed. As shown in Table 2 below, taking the rolled product Φ6×0.6mm as an example, the results show that when the outer diameter of the tube changes, the CSR of the finished product Φ6×0.6mm does not change much. It is speculated that the outer diameter of the tube has no effect on the CSR value. To further verify this hypothesis, the initial outer diameter and wall thickness of the tube are fixed and the finished product specifications are changed. When the finished product specifications are changed to: Φ8×0.7mm, Φ10×0.9mm, etc., their CSR values ​​are not much different from the CSR value of Φ6×0.6mm. Therefore, it is determined that the initial outer diameter of the tube has little effect on the CSR value.

[0035] Table 2 The CSR values ​​of different tubes with different outer diameters when the initial tube outer diameter and wall thickness remain unchanged

[0036]

[0037] (3) The initial tube blank structure is determined as equiaxed structure, and the initial outer diameter of the tube blank is determined as D0. Only the variable initial tube blank wall thickness t0 remains. The Q value is controlled by controlling the wall thickness, and finally the CSR value is controlled. As shown in Table 3 below, taking the finished tube Φ6×0.6mm as an example, the test found that: when the initial tube blank wall thickness is 3mm, the wall thickness thinning rate is 80%, at this time the total Q value is 0.88, and the CSR value is <1.3. When the initial tube blank wall thickness is ≥3mm, the wall thickness thinning rate is ≥80%, at this time the total Q value is ≥0.88, and the CSR value meets the requirements of 1.3~3.5. Therefore, controlling the initial tube blank wall thickness thinning rate ≥80% can ensure that the CSR value meets the requirements. At this time, the total Q value range is ≥0.88. In addition, when the initial tube blank wall thickness thinning rate is ≥80%, the CSR values ​​of Φ8, Φ12 and other tubes meet the requirements, and their Q value control range is shown in the table below.

[0038] Table 3 Initial tube outer diameter and outer diameter remain unchanged, and the CSR values ​​of different tubes with different wall thickness values ​​are changed

[0039]

[0040] Based on the above analysis, it is verified that the initial tube billet adopts equiaxed structure, which can improve the uniform deformation of the cold-rolled structure of the tube, enhance the strength and plasticity, and delay the crack nucleation, laying the foundation for the design of the total Q value. At the same time, the initial tube billet outer diameter has no effect on the CSR value, so the only variable affecting the Q value is the initial tube billet wall thickness. By designing different wall thickness values ​​to make the CSR value meet the requirements, the correlation between the initial tube billet wall thickness and the Q value is obtained. The results show that the initial tube billet wall thickness thinning rate is ≥80%, and the CSR value meets the requirements. This embodiment provides a theoretical basis for the control of the CSR value of the important performance indicator of the tube.

[0041] Based on this, this embodiment provides a method for preparing a seamless titanium alloy tube for an aviation hydraulic system, comprising the following steps:

[0042] S1. providing a seamless titanium alloy tube blank, wherein the structure of the tube blank is an equiaxed structure;

[0043] S2, cold rolling the tube blank to obtain a seamless titanium alloy tube;

[0044] S3, annealing, cleaning and flaw detection are performed on the seamless titanium alloy tube to obtain a finished seamless titanium alloy tube.

[0045] Wherein, in step S2, the wall thickness reduction rate of the cold rolling treatment is controlled to be greater than 80%, and the total Q value is greater than 0.88, so that the shrinkage strain ratio of the seamless titanium alloy tube is controlled to be 1.3-3.5. In the above parameters, the wall thickness reduction rate is the difference between the wall thickness of the seamless titanium alloy tube and the wall thickness of the tube blank, and Q is the ratio of the relative wall thickness reduction before and after the cold rolling of the tube to the relative reduction in the outer diameter.

[0046] Furthermore, in step S1, the wall thickness of the tube blank is greater than 3 mm.

[0047] Furthermore, in step S1, the outer diameter of the tube blank is 50-80 mm. In the following samples, the outer diameter of the tube blank is selected from 55-70 mm.

[0048] Furthermore, in step S2, the shrinkage strain ratio is adjusted to 1.3-3.5 by controlling the structure of the tube blank to be equiaxed and adjusting the wall thickness reduction rate. The Q value is adjusted to be greater than 0.88, 0.90 or 0.97 by adjusting the wall thickness reduction rate.

[0049] Furthermore, the cold rolling treatment includes multiple cold rolling processes, and the wall thickness reduction rate of each cold rolling process is controlled to be 20%~60%, and the Q value is controlled to be: 0.5~2.00.

[0050] In some embodiments, the specifications of the finished seamless titanium alloy tube are Φ6×0.6 mm, Φ8×0.7 mm, Φ10×0.9 mm or Φ12×1 mm.

[0051] The seamless titanium alloy tube for aviation hydraulic system is obtained by the above-mentioned preparation method, and the CSR value of the seamless titanium alloy tube is precisely controlled to meet the following conditions: 1.3≤CSR≤3.5.

[0052] Preparation Example 1

[0053] (1) Provide seamless titanium alloy TA18 tube blank with equiaxed structure and a specification of 80 mm;

[0054] (2) The seamless titanium alloy tube blank is subjected to cold rolling and stress relief annealing processes, as shown in Table 4 below.

[0055] Table 4 Multi-pass cold rolling and annealing process

[0056]

[0057] The tube blank undergoes multiple rolling, degreasing and pickling, flattening, annealing, finishing, straightening, water pressure, flaw detection, surface treatment, inspection and other processes to produce a finished seamless titanium alloy TA18 tube with a specification of Φ6×0.6mm.

[0058] Fifteen samples were selected for testing according to AS 4076. The test results are shown in Table 5.

[0059] Table 5

[0060]

[0061] Preparation Example 2

[0062] (1) Provide seamless titanium alloy TA18 tube blank with equiaxed structure and a specification of 80 mm;

[0063] (2) The seamless titanium alloy tube blank is subjected to cold rolling and stress relief annealing processes, as shown in Table 6 below.

[0064] Table 6 Multi-pass cold rolling and annealing process

[0065]

[0066] After multiple rolling, degreasing and pickling, flattening, annealing, finishing, straightening, water pressure, flaw detection, surface treatment, inspection and other processes, the finished seamless titanium alloy TA18 pipe with a specification of Φ8×0.7mm is obtained.

[0067] Fifteen samples were selected for testing according to AS 4076. The test results are shown in Table 7.

[0068] Table 7

[0069]

[0070] Preparation Example 3

[0071] (1) Provide seamless titanium alloy TA18 tube blank with equiaxed structure and a specification of 80 mm;

[0072] (2) The seamless titanium alloy tube blank is subjected to cold rolling and stress relief annealing processes, as shown in Table 8 below.

[0073] Table 8 Multi-pass cold rolling and annealing process

[0074]

[0075] After multiple rolling, degreasing and pickling, flattening, annealing, and finished product straightening, water pressure, flaw detection, surface treatment, inspection and other processes, the finished seamless titanium alloy TA18 pipe with a specification of Φ12×1.0mm is obtained.

[0076] Fifteen samples were selected for testing according to AS 4076. The test results are shown in Table 9.

[0077] Table 9

[0078]

[0079] The CSR of the seamless titanium alloy tubes of various specifications obtained by the method of this embodiment all meet the condition of 1.3≤CSR≤3.5, and can be used as the tube material for aviation hydraulic pipelines.

[0080] As shown in this specification and claims, the terms "comprises" and "includes" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0081] It is further understood that in the present disclosure, "plurality" refers to two or more than two, and other quantifiers are similar thereto.

[0082] It is further understood that the terms "first", "second", etc. are used to describe various information, but such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other, and do not indicate a specific order or degree of importance. In fact, the expressions "first", "second", etc. can be used interchangeably. For example, without departing from the scope of the present disclosure, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information.

[0083] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention.

Claims

1. A method for preparing a seamless titanium alloy tube for an aviation hydraulic system, characterized in that: The steps include: S1. providing a seamless titanium alloy TA18 tube blank, wherein the structure of the TA18 tube blank is an equiaxed structure; S2, cold rolling the TA18 tube blank to obtain a seamless titanium alloy TA18 tube; Wherein, in step S2, the wall reduction rate and the total Q value of the cold rolling treatment are controlled so that the shrinkage strain ratio of the seamless titanium alloy tube is controlled to be 1.3-3.5; the wall reduction rate is the difference between the wall thickness of the seamless titanium alloy tube and the wall thickness of the tube blank, and Q is the ratio of the relative wall thickness reduction before and after the cold rolling of the tube to the relative outer diameter reduction; The cold rolling process includes 5 cold rolling passes. Among them, the first pass rolls the Φ80×8mm tube into Φ65×6mm, the annealing temperature is 450℃, the wall reduction rate is 25%, and the Q value is 1.33; the second pass rolls the tube into Φ50×4mm, the annealing temperature is 700℃, the wall reduction rate is 33%, and the Q value is 1.44; the third pass rolls the tube into Φ30×2mm, the annealing temperature is 550℃, the wall reduction rate is 50%, and the Q value is 1.25; the fourth pass rolls the tube into Φ12×1mm, the annealing temperature is 680℃, the wall reduction rate is 50%, and the Q value is 0.83; the fifth pass rolls the tube into a Φ8×0.7mm finished seamless titanium alloy TA18 tube, the annealing temperature is 620℃, the wall reduction rate is 30%, and the Q value is 0.90; the total wall reduction rate of the controlled cold rolling treatment is 91%, and the total Q value is 1.01; Or, in the first pass, the Φ80×8mm tube billet is rolled into Φ65×6mm, the annealing temperature is 450℃, the wall reduction rate is 25%, and the Q value is 1.33; in the second pass, the tube billet is rolled into Φ50×4mm, the annealing temperature is 700℃, the wall reduction rate is 33%, and the Q value is 1.44; in the third pass, the tube billet is rolled into Φ30×2mm, the annealing temperature is 550℃, the wall reduction rate is 50%, and the Q value is 1.25; in the fourth pass, the tube billet is rolled into Φ16×1.4mm, the annealing temperature is 650℃, the wall reduction rate is 30%, and the Q value is 0.64; in the fifth pass, the tube billet is rolled into a finished seamless titanium alloy TA18 tube of Φ12×1mm, the annealing temperature is 540℃, the wall reduction rate is 29%, and the Q value is 1.14; the total wall reduction rate of the controlled cold rolling treatment is 88%, and the total Q value is 1.

03.

2. The preparation method according to claim 1, characterized in that: The preparation method further comprises step S3, annealing, cleaning and flaw detection of the seamless titanium alloy tube to obtain the seamless titanium alloy tube for the aviation hydraulic system.

3. A seamless titanium alloy tube for aviation hydraulic system, characterized in that: Prepared by the preparation method as claimed in claim 1 or 2.

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