Cold rolling process for improving grain uniformity of ta4 alloy

Abstract

This invention discloses a cold rolling process for improving the grain uniformity of TA4 alloy, comprising the following steps: S1: First cold rolling; rolling a 0.5mm TA4 alloy strip to 0.33mm; S2: Intermediate annealing; fully annealing the TA4 alloy strip after S1 cold rolling; S3: Second cold rolling; rolling it from 0.33mm to a target thickness of 0.20mm, with a total deformation of 39.4% in the second rolling pass; S4: Finished product annealing; carried out in a continuous annealing furnace with zones 1 to 9, resulting in a TA4 alloy strip with uniform microstructure. This invention solves the problems of coarse and uneven grains, weakened texture, or insufficient local phase transformation in current TA4 titanium alloys, which affect the overall performance and service life of applied products. The grain intercept distribution of this invention is improved from the original 8-17μm to 10-16μm, with better microstructure uniformity in the 10-16μm range.

Description

Technical Field

[0001] This invention belongs to the technical field of cold rolling process of TA4 alloy, and particularly relates to a cold rolling process for improving the grain uniformity of TA4 alloy. Background Technology

[0002] In the field of 3C electronics, advanced titanium alloy materials, especially TA4, are increasingly widely used in high-precision structural components, such as folding screen hinges, high-end shells, and internal support components.

[0003] In practical applications, especially for precision components such as folding screen hinges that need to withstand hundreds of thousands of repeated bending movements, the uniformity and stability of their material structure are of paramount importance.

[0004] However, TA4 titanium alloy currently suffers from problems such as coarse and uneven grains, weakened texture, or insufficient local phase transformation. These issues directly lead to fluctuations or decreases in the material's mechanical properties, such as yield strength, elastic modulus, and fatigue limit, and may cause stress concentration at the microscopic level. During the repeated opening and closing of foldable screens, this performance inhomogeneity will be amplified, specifically manifesting as reduced smoothness of hinge mechanism movement, abnormal noise, and deeper creases. It may even lead to premature fatigue failure of the screen support structure, thereby seriously affecting the overall performance and service life of the product. Summary of the Invention

[0005] The purpose of this invention is to address the problems of coarse and uneven grains, weakened texture, or insufficient local phase transformation in TA4 titanium alloys, which directly lead to fluctuations or decreases in the mechanical properties of the material, such as yield strength, elastic modulus, and fatigue limit, and may cause stress concentration at the microscopic level, thereby affecting the overall performance and service life of the applied products. Therefore, this invention proposes a cold rolling process to improve the grain uniformity of TA4 alloys.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a cold rolling process for improving the grain uniformity of TA4 alloy, comprising the following steps:

[0007] S1: First cold rolling; The TA4 alloy coil with a thickness of 0.5mm is cold rolled in the first rolling pass to 0.33mm;

[0008] S2: Intermediate annealing; the TA4 alloy coil after cold rolling in S1 is fully annealed;

[0009] S3: Second cold rolling; The TA4 alloy strip annealed in S2 is subjected to a second cold rolling pass to roll it from 0.33mm to the target thickness of 0.20mm. The total deformation of the second rolling pass is 39.4%.

[0010] S4: Finished product annealing; The TA4 alloy coils after being cold rolled in S3 are subjected to finished product annealing; The finished product annealing is carried out in a continuous annealing furnace with zones 1 to 9 to obtain TA4 alloy coils with uniform material structure.

[0011] Furthermore, the annealing rate in S4 is 15-17 m / min.

[0012] Furthermore, the frequency of the cooling fan in S4 is 19-21 Hz.

[0013] Furthermore, the annealing atmosphere in S4 is argon gas with a flow rate of 34-36 m³ / h.

[0014] Furthermore, in S4, the temperature of zone 1 is 500℃, the temperature of zone 2 is 550℃, the temperature of zone 3 is 780℃, the temperature of zones 4-8 is 810℃, and the temperature of zone 9 is 800℃.

[0015] Furthermore, in S3, the second cold rolling process adopts multi-pass rolling, and the reduction rate of each pass decreases sequentially from the first pass to the last pass, wherein the maximum reduction rate does not exceed 9.1% and the minimum reduction rate is not less than 4.76%.

[0016] The present invention provides a cold rolling process for improving the grain uniformity of TA4 alloy. Through experimental comparison, it was found that by precisely controlling the deformation amount in a single rolling pass during the cold rolling stage to ≤40%, and combining this with a specific subsequent full annealing process, effective regulation of the recrystallization process and grain growth kinetics of TA4 material can be achieved. When the deformation amount in a single rolling pass is controlled at a low level (≤40%), the deformation energy stored inside the material, i.e., the dislocation density and deformation band density, is relatively moderate and more uniformly distributed. In the subsequent full annealing process, this relatively uniform distribution of deformation energy provides favorable conditions for a large number of near-synchronous recrystallization nuclei. The spatial distribution of nucleation points is more uniform, reducing the risk of individual nucleation points being affected by excessively high local energy storage. The difference in driving forces for abnormally rapid grain growth makes the growth process of new grains more synchronous and controllable. This ultimately leads to a narrowing of the grain size distribution range after recrystallization, and a significant improvement in the uniformity of the overall microstructure (including grain size and morphology). In contrast, when the deformation amount in a single rolling pass is too high (>40%), the internal deformation of the material is severe, the deformation energy storage is high but the distribution may be uneven, and strong deformation bands and textures are easily formed. During annealing, recrystallization nucleation occurs early and grows quickly in the high energy storage area, while the low energy storage area may recover or undergo incomplete recrystallization, resulting in asynchronous recrystallization processes. Ultimately, the grain size distribution range widens and the uniformity decreases. The cold rolling process of this application can effectively delay the initiation of fatigue cracks and improve the fatigue life and reliability of the product.

[0017] Therefore, this embodiment has the following advantages compared to the prior art:

[0018] A cold rolling process to improve the grain uniformity of TA4 alloy solves the problems of coarse and uneven grains, weakened texture, or insufficient local phase transformation in TA4 titanium alloy. These problems directly lead to fluctuations or decreases in the mechanical properties of the material, such as yield strength, elastic modulus, and fatigue limit, and may cause stress concentration at the microscopic level, thereby affecting the overall performance and service life of the applied products. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a chart showing the reduction rate of the second rolling pass in Example 1 of a cold rolling process for improving the grain uniformity of TA4 alloy.

[0021] Figure 2 Temperature table of the continuous annealing furnace zone in Example 1 of a cold rolling process for improving the grain uniformity of TA4 alloy.

[0022] Figure 3 This is a chart showing the reduction rate of the second rolling pass in a comparative example 1 of a cold rolling process for improving the grain uniformity of TA4 alloy.

[0023] Figure 4 Temperature table of the continuous annealing furnace area in Comparative Example 1 of a cold rolling process for improving the grain uniformity of TA4 alloy.

[0024] Figure 5 Metallographic images of the finished product from a comparative example of a cold rolling process for improving the grain uniformity of TA4 alloy.

[0025] Figure 6 This is a metallographic image of the finished product from Example 1 of a cold rolling process for improving the grain uniformity of TA4 alloy. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] In the description of the embodiments of the present invention, it should be noted that the terms "upper" and "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0031] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Example 1

[0033] Please see Figure 1-2 6. The present invention provides a technical solution: a cold rolling process for improving the grain uniformity of TA4 alloy, comprising the following steps:

[0034] S1: First cold rolling; The TA4 alloy coil with a thickness of 0.5mm is cold rolled in the first rolling pass to 0.33mm;

[0035] S2: Intermediate annealing; the TA4 alloy coil after cold rolling in S1 is fully annealed;

[0036] S3: Second cold rolling; The TA4 alloy strip annealed in S2 is subjected to a second cold rolling pass to roll it from 0.33mm to the target thickness of 0.20mm. The total deformation of the second rolling pass is 39.4%.

[0037] S4: Finished product annealing; The TA4 alloy coils after being cold rolled in S3 are subjected to finished product annealing; The finished product annealing is carried out in a continuous annealing furnace with zones 1 to 9 to obtain TA4 alloy coils with uniform material structure.

[0038] Specifically, see Figure 1-2 6. The annealing rate in S4 is 15-17 m / min.

[0039] Specifically, see Figure 1-2 6. The frequency of the cooling fan in S4 is 19-21 Hz.

[0040] Specifically, see Figure 1-2 6. In S4, the annealing atmosphere is argon gas with a flow rate of 34-36 m³ / h.

[0041] Specifically, see Figure 1-2 6. In S4, the temperature of zone 1 is 500℃, the temperature of zone 2 is 550℃, the temperature of zone 3 is 780℃, the temperature of zones 4-8 is 810℃, and the temperature of zone 9 is 800℃.

[0042] Specifically, see Figure 1-2 6. In S3, the second cold rolling process adopts multi-pass rolling, and the reduction rate of each pass decreases sequentially from the first pass to the last pass. The maximum reduction rate does not exceed 9.1%, and the minimum reduction rate is not less than 4.76%.

[0043] Comparative Example 1

[0044] Please see Figure 3-5 This invention provides a technical solution: a cold rolling process for improving the grain uniformity of TA4 alloy, comprising the following steps:

[0045] S1: First cold rolling; The TA4 alloy coil with a thickness of 0.5mm is cold rolled in the first rolling pass to 0.35mm;

[0046] S2: Intermediate annealing; the TA4 alloy coil after cold rolling in S1 is fully annealed;

[0047] S3: Second cold rolling; The TA4 alloy strip after S2 annealing is subjected to a second cold rolling pass to roll it from 0.35mm to the target thickness of 0.20mm, with a total deformation of 43% in the second rolling pass;

[0048] S4: Finished product annealing; The TA4 alloy coil after cold rolling in step S3 is subjected to finished product annealing; The finished product annealing is carried out in a continuous annealing furnace with zones 1 to 9 to obtain a TA4 alloy coil with uniform material structure.

[0049] Specifically, see Figure 3-5 The annealing rate in S4 is 18-19 m / min.

[0050] Specifically, see Figure 3-5 The frequency of the cooling fan in S4 is 34-36 Hz.

[0051] Specifically, see Figure 3-5 In step S4, the annealing atmosphere is argon gas with a flow rate of 24-26 m³ / h.

[0052] Specifically, see Figure 3-5 In S4, the temperature of zone 1 is 500℃, the temperature of zone 2 is 550℃, the temperature of zone 3 is 780℃, the temperature of zones 4-8 is 810℃, and the temperature of zone 9 is 800℃.

[0053] Specifically, see Figure 3-5 In S3, the second cold rolling process adopts multi-pass rolling, and the reduction rate of each pass decreases sequentially from the first pass to the last pass. The maximum reduction rate does not exceed 9.14%, and the minimum reduction rate is not less than 4.31%.

[0054] By performing full annealing on the cold-rolled and deformed material according to the above annealing process, its grain size can be controlled between 9 and 9.5. The intercept size of the grains is collected by using the intercept method.

[0055] In comparison with Example 1, when the deformation amount of a single cold rolling pass is >40%, the grain size after annealing is approximately 9.2 grade, the average grain intercept is 13.8 μm, and most grain intercepts are distributed between 8-17 μm.

[0056] In Example 1, when the deformation amount of a single cold rolling pass is ≤40%, the grain size after annealing is approximately grade 9, the average grain intercept is 14.2 μm, and most grain intercepts are distributed between 10-16 μm.

[0057] Conclusion: It can be seen that when the cold rolling deformation is reduced to less than 40%, the uniformity of the microstructure is significantly improved, from the original 8-17μm to 10-16μm.

[0058] Working Principle: The cold rolling process for improving the grain uniformity of TA4 alloy provided by this invention, through experimental comparison, reveals that by precisely controlling the deformation amount in a single rolling pass during the cold rolling stage to ≤40%, and combining this with a specific subsequent full annealing process, effective regulation of the recrystallization process and grain growth kinetics of TA4 material can be achieved. When the deformation amount in a single rolling pass is controlled at a low level (≤40%), the deformation energy stored inside the material, i.e., the dislocation density and deformation band density, is relatively moderate and more uniformly distributed. In the subsequent full annealing process, this relatively uniform distribution of deformation energy provides favorable conditions for a large number of near-synchronous recrystallization nuclei. The spatial distribution of nucleation points is more uniform, reducing the risk of excessive local energy storage. The difference in driving forces for the abnormally rapid growth of individual grains makes the growth process of new grains more synchronous and controllable. This ultimately leads to a narrowing of the grain size distribution range after recrystallization, and a significant improvement in the uniformity of the overall microstructure (including grain size and morphology). In contrast, when the deformation amount in a single rolling pass is too high (>40%), the internal deformation of the material is severe, the deformation energy is high but the distribution may be uneven, and strong deformation bands and textures are easily formed. During annealing, recrystallization nucleation occurs early and grows quickly in the high energy storage area, while recovery or incomplete recrystallization may occur in the low energy storage area, resulting in asynchronous recrystallization processes. Ultimately, the grain size distribution range widens and the uniformity decreases. The cold rolling process of this application can effectively delay the initiation of fatigue cracks and improve the fatigue life and reliability of the product.

[0059] Therefore, this embodiment has the following advantages compared to the prior art:

[0060] A cold rolling process to improve the grain uniformity of TA4 alloy solves the problems of coarse and uneven grains, weakened texture, or insufficient local phase transformation in TA4 titanium alloy. These problems directly lead to fluctuations or decreases in the mechanical properties of the material, such as yield strength, elastic modulus, and fatigue limit, and may cause stress concentration at the microscopic level, thereby affecting the overall performance and service life of the applied products.

[0061] 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 equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cold rolling process for improving the grain uniformity of TA4 alloy, characterized in that, Includes the following steps: S1: First cold rolling; The TA4 alloy coil with a thickness of 0.5mm is cold rolled in the first rolling pass to 0.33mm; S2: Intermediate annealing; the TA4 alloy coil after cold rolling in S1 is fully annealed; S3: Second cold rolling; The TA4 alloy strip annealed in S2 is subjected to a second cold rolling pass to roll it from 0.33mm to the target thickness of 0.20mm. The total deformation of the second rolling pass is 39.4%. S4: Finished product annealing; The TA4 alloy coils after being cold rolled in S3 are subjected to finished product annealing; The finished product annealing is carried out in a continuous annealing furnace with zones 1 to 9 to obtain TA4 alloy coils with uniform material structure.

2. The cold rolling process for improving the grain uniformity of TA4 alloy according to claim 1, characterized in that, The annealing rate in S4 is 15-17 m / min.

3. The cold rolling process for improving the grain uniformity of TA4 alloy according to claim 1, characterized in that, The frequency of the cooling fan in S4 is 19-21 Hz.

4. The cold rolling process for improving the grain uniformity of TA4 alloy according to claim 3, characterized in that, The annealing atmosphere in S4 is argon, with a flow rate of 34-36 m³ / h.

5. The cold rolling process for improving the grain uniformity of TA4 alloy according to claim 4, characterized in that, In S4, the temperature of zone 1 is 500℃, the temperature of zone 2 is 550℃, the temperature of zone 3 is 780℃, the temperature of zones 4-8 is 810℃, and the temperature of zone 9 is 800℃.

6. The cold rolling process for improving the grain uniformity of TA4 alloy according to claim 3, characterized in that, In S3, the second cold rolling process adopts multi-pass rolling, and the reduction rate of each pass decreases sequentially from the first pass to the last pass. The maximum reduction rate does not exceed 9.1%, and the minimum reduction rate is not less than 4.76%.

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