Continuous recrystallization annealing treatment process for TC4 titanium alloy cold-rolled strip coil

Abstract

The invention discloses a continuous recrystallization annealing treatment process for a TC4 titanium alloy cold-rolled strip coil. The continuous recrystallization annealing treatment process comprises the following steps: S1, a pretreatment stage; the TC4 titanium alloy cold-rolled strip coil is subjected to surface cleaning treatment; s2, after the furnace temperature rises to the required temperature, the pretreated TC4 titanium alloy cold-rolled strip coil is fed into a continuous annealing furnace to pass through a heating section of the continuous furnace at a specified speed; s3, a cooling stage; the TC4 titanium alloy cold-rolled strip coil is rapidly and evenly cooled, and the tapping temperature is smaller than or equal to 70 DEG C; and S4, a post-processing stage: carrying out detection. Through the principle of segmented annealing, the segmented annealing and hot leveling processes are adopted in the annealing process, and the flatness, the mechanical property and the corrosion resistance of the product are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy strip coil annealing, and in particular relates to a TC4 titanium alloy cold-rolled strip coil continuous recrystallization annealing treatment process. Background Art

[0002] As a high-performance titanium alloy material, TC4 (Ti-6Al-4V) cold-rolled titanium strip has shown great potential in the application of foldable screen mobile phone display backplanes. However, for the specific application scenario of foldable screen mobile phones, extremely stringent requirements are placed on the mechanical properties, flatness and surface quality of the material.

[0003] The back panel of the foldable mobile phone display needs to withstand a complex mechanical environment, including frequent bending, twisting and extrusion, etc. Therefore, TC4 cold-rolled titanium strip must have excellent mechanical properties, high flatness and good surface corrosion resistance.

[0004] However, the existing TC4 cold-rolled titanium strip often has flatness problems such as surface waves and wrinkles during the cold rolling process, as well as a decrease in mechanical properties in local areas, which in turn affects the durability of the entire back panel. These problems not only affect the appearance, but more importantly, will have a serious impact on the performance of foldable screen mobile phones. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of flatness such as surface waves and wrinkles and the decline of mechanical properties in local areas of the existing TC4 cold-rolled titanium strip during the cold rolling process, which affects the durability of the entire back panel. These problems not only affect the appearance, but more importantly, have a serious impact on the performance of folding screen mobile phones. A continuous recrystallization annealing process for TC4 titanium alloy cold-rolled strip is proposed.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process,

[0007] The following steps are involved:

[0008] S1: pretreatment stage; performing surface cleaning treatment on the TC4 titanium alloy cold-rolled strip coil to remove oil stains, oxides and other impurities on the surface of the TC4 titanium alloy cold-rolled strip coil;

[0009] S2: After the furnace temperature rises to the required temperature, the pre-treated TC4 titanium alloy cold-rolled strip is sent into the continuous annealing furnace;

[0010] S3: Cooling stage; TC4 titanium alloy cold-rolled coil is cooled in the continuous furnace cooling section, and the furnace temperature is ≤70°C;

[0011] S4: Post-processing stage: Perform necessary surface treatment and testing on the TC4 titanium alloy cold-rolled coil after annealing to ensure that the final product meets the use requirements.

[0012] As a further description of the above technical solution:

[0013] The TC4 titanium alloy strip in S2 is continuously annealed in an argon-protected continuous annealing furnace, the temperature of the argon-protected continuous annealing furnace is 800° C. to 910° C., the residual oxygen in the furnace is less than 5 ppm, and the furnace maintains a positive pressure.

[0014] As a further description of the above technical solution:

[0015] S1 also includes degreasing the TA4 titanium alloy cold-hardened coil to remove impurities such as oil stains on the surface of the coil to obtain a clean surface.

[0016] As a further description of the above technical solution:

[0017] After the furnace temperature rises to the low temperature annealing temperature range in S2, the TC4 titanium alloy cold-rolled strip coil enters the furnace at a constant speed of 1-5 m / min and continues to move.

[0018] As a further description of the above technical solution:

[0019] During the tape running process, the tape is wound up by a winder at a tension of 5 to 15 N / mm.

[0020] As a further description of the above technical solution:

[0021] The control accuracy of the holding temperature in the furnace at any stage of the annealing process shall not be less than ±5℃.

[0022] As a further description of the above technical solution:

[0023] The holding time in the high temperature annealing stage is set to at least 5 to 10 minutes per millimeter of the thickness of the TC4 titanium alloy cold-rolled strip coil to ensure sufficient recrystallization.

[0024] As a further description of the above technical solution:

[0025] The method also includes preheating the TC4 titanium alloy cold-rolled coil before annealing, wherein the preheating temperature is 50% to 80% of the lower limit of the recrystallization annealing temperature to reduce the temperature gradient and thermal stress of the coil during the heating process.

[0026] As a further description of the above technical solution:

[0027] The cooling stage in S3 includes water quenching or gas quenching.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. In the present invention, through the principle of staged annealing, low-temperature annealing is used to improve plasticity and flatness, and high-temperature annealing is used to promote full recrystallization and optimize the grain structure, thereby significantly improving the key mechanical performance indicators such as tensile strength, yield strength and fatigue strength of the titanium strip coil. The low-temperature stabilization treatment stage further refines the microstructure of the titanium strip surface, reduces surface defects, improves smoothness and corrosion resistance, and ensures that the final product has excellent surface quality.

[0030] 2. In the present invention, the temperature in the furnace is strictly controlled at each stage to ensure uniform temperature distribution, avoid uneven performance caused by local overheating or overcooling, and improve the stability and consistency of product quality. In addition, the preheating treatment reduces the temperature gradient and thermal stress of the coil during the heating process, which helps to maintain the flatness of the coil and reduce deformation. The segmented annealing and thermal leveling process are used in the annealing process, which greatly improves the flatness, mechanical properties and corrosion resistance of the TC4 titanium alloy cold-rolled coil after annealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A flowchart of the steps of a continuous recrystallization annealing process for a TC4 titanium alloy cold-rolled strip.

[0033] Figure 2 A flowchart of the steps of segmented annealing in a continuous recrystallization annealing process for a TC4 titanium alloy cold-rolled coil. DETAILED DESCRIPTION

[0034] 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.

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0037] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0038] In the description of the embodiments of the present invention, it should be noted that the terms "upper", "inner", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the inventive product 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 direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0039] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] Embodiment 1

[0041] See also Figure 1-2 The present invention provides a technical solution: a TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process, comprising the following steps:

[0042] S1: pretreatment stage; performing surface cleaning treatment on the TC4 titanium alloy cold-rolled strip coil to remove oil stains, oxides and other impurities on the surface of the TC4 titanium alloy cold-rolled strip coil; ensuring that the surface of the strip coil is clean and flawless;

[0043] S2: After the furnace temperature rises to the required temperature, the pre-treated TC4 titanium alloy cold-rolled strip is sent into the continuous annealing furnace;

[0044] S3: Cooling stage; the TC4 titanium alloy cold-rolled coil is cooled in the continuous furnace cooling section, and the furnace temperature is ≤70°C; the TC4 titanium alloy cold-rolled coil is cooled quickly and evenly to prevent excessive grain growth and maintain the good structure and performance obtained after annealing;

[0045] S4: Post-processing stage: Perform necessary surface treatment and testing on the TC4 titanium alloy cold-rolled coil after annealing to ensure that the final product meets the use requirements.

[0046] The TC4 titanium alloy strip in S2 is continuously annealed in an argon-protected continuous annealing furnace, the temperature of the argon-protected continuous annealing furnace is 800° C. to 910° C., the residual oxygen in the furnace is less than 5 ppm, and the furnace maintains a positive pressure.

[0047] Embodiment 2

[0048] The annealing furnace in S2 needs to go through three stages of annealing, namely, a low-temperature annealing stage, a high-temperature annealing stage and a low-temperature stabilization treatment stage. In the low-temperature annealing stage, the pretreated TC4 titanium alloy cold-rolled strip is fed into a continuous annealing furnace, an inert gas is used as a protective atmosphere in the furnace, the furnace temperature is raised to a range of 300°C to 500°C, and maintained at this temperature for 30 minutes to 2 hours; in the high-temperature annealing stage, after the low-temperature annealing is completed, the temperature is continued to be raised to a range of 600°C to 800°C, and maintained at this temperature for 2 hours to 4 hours, so that a sufficient recrystallization process occurs inside the TC4 titanium alloy cold-rolled strip; in the low-temperature stabilization treatment stage, after the high-temperature annealing is completed, the furnace temperature is lowered to a range of 200°C to 400°C, and maintained at this temperature for 1 hour to 3 hours.

[0049] S1 also includes degreasing the TA4 titanium alloy cold-hardened coil to remove impurities such as oil stains on the surface of the coil to obtain a clean surface.

[0050] After the furnace temperature in S2 rises to the low temperature annealing temperature range, the TC4 titanium alloy cold-rolled strip coil enters the furnace at a constant speed of 3-20 m / min and continues to move.

[0051] During the tape running process, the tape is reeled at a tension of 5 to 15 N / mm by a reeling machine to ensure the flatness and quality of the tape.

[0052] The control accuracy of the holding temperature in the furnace at any stage of the annealing process is not less than ±5°C to ensure the uniformity of the coil temperature distribution.

[0053] The holding time in the high temperature annealing stage is set to at least 5 to 10 minutes per millimeter of the thickness of the TC4 titanium alloy cold-rolled strip coil to ensure sufficient recrystallization.

[0054] The method also includes preheating the TC4 titanium alloy cold-rolled coil before annealing, wherein the preheating temperature is 50% to 80% of the lower limit of the recrystallization annealing temperature to reduce the temperature gradient and thermal stress of the coil during the heating process.

[0055] The cooling stage in S4 includes water quenching or gas quenching to ensure that the cooling rate meets the requirements for maintaining material properties, and the TC4 titanium alloy cold-rolled coil is cooled quickly and evenly to prevent excessive grain growth and maintain the good structure and properties obtained after annealing;

[0056] Working principle: by removing impurities such as oil and oxides on the surface of the coil, a clean surface condition is provided for the subsequent annealing treatment. Annealing at a lower temperature can preliminarily improve the plasticity and flatness of the titanium strip, prepare for the subsequent high-temperature recrystallization, and then carry out high-temperature annealing and keep it warm at a higher temperature to allow a full recrystallization process to occur inside the titanium alloy, refine the grains, improve the mechanical properties, stabilize at low temperatures, further adjust the microstructure of the titanium strip surface, improve the surface quality, and finally cool it. Rapid and uniform cooling prevents excessive grain growth and maintains the good organization and performance obtained after annealing; post-treatment, remove possible oxide scales, check and adjust the dimensional accuracy and surface quality of the coil, and ensure that the final product meets the use requirements; this process is based on the organizational transformation law of titanium alloy at different temperatures; by precisely controlling the temperature, time and cooling rate during annealing, a series of physical and chemical changes are induced inside the titanium alloy, thereby optimizing its microstructure and performance.

[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A TC4 titanium alloy cold-rolled coil continuous recrystallization annealing process, characterized in that: The following steps are involved: S1: pretreatment stage; performing surface cleaning treatment on the TC4 titanium alloy cold-rolled strip coil to remove oil stains, oxides and other impurities on the surface of the TC4 titanium alloy cold-rolled strip coil; S2: After the furnace temperature rises to the required temperature, the pre-treated TC4 titanium alloy cold-rolled strip is sent into the continuous annealing furnace; S3: Cooling stage; TC4 titanium alloy cold-rolled coil is cooled in the continuous furnace cooling section, and the furnace temperature is ≤70°C; S4: Post-processing stage: Perform necessary surface treatment and testing on the TC4 titanium alloy cold-rolled coil after annealing to ensure that the final product meets the use requirements.

2. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 1, characterized in that: The TC4 titanium alloy strip in S2 is continuously annealed in an argon-protected continuous annealing furnace, the temperature of the argon-protected continuous annealing furnace is 800° C. to 910° C., the residual oxygen in the furnace is less than 5 ppm, and the furnace maintains a positive pressure.

3. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 1, characterized in that: The S1 also includes degreasing the TA4 titanium alloy cold-hardened coil to remove impurities such as oil stains on the surface of the coil to obtain a clean surface.

4. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 2, characterized in that: After the furnace temperature in S2 rises to the low temperature annealing temperature range, the TC4 titanium alloy cold-rolled strip coil enters the furnace at a constant speed of 1-5 m / min and continues to move.

5. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 4, characterized in that: During the tape running process, the tape is wound up by a winder at a tension of 5 to 15 N / mm.

6. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 2, characterized in that: The control accuracy of the holding temperature in the furnace at any stage of the annealing process shall not be less than ±5°C.

7. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 2, characterized in that: The holding time in the high temperature annealing stage is set to at least 5 to 10 minutes per millimeter of the thickness of the TC4 titanium alloy cold-rolled strip coil to ensure sufficient recrystallization.

8. The continuous recrystallization annealing process for TC4 titanium alloy cold-rolled strip according to claim 1, characterized in that: The method also includes preheating the TC4 titanium alloy cold-rolled coil before annealing, wherein the preheating temperature is 50% to 80% of the lower limit of the recrystallization annealing temperature to reduce the temperature gradient and thermal stress of the coil during the heating process.

9. A TC4 titanium alloy cold-rolled strip continuous recrystallization annealing process according to claim 7, characterized in that: The cooling stage in S3 includes water quenching or gas quenching.

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