Preparation method of high-toughness TC21 titanium alloy plate

Abstract

The invention discloses a preparation method of a high-toughness TC21 titanium alloy plate. A'low-low-high 'combined forging process is formulated by analyzing factors such as forge piece structure performance, alloy forging structure evolution, equipment and environment conditions, raw material states and the like, namely, alpha + beta forging is performed through a 5000T oil press, alpha + beta forging is performed through a 3T free forging hammer, and finally quasi-beta forging is performed through the 5000T oil press; during quasi beta forging, an asbestos adhesive sheath is used for preventing temperature loss; for large-specification forgings, 'air and water combined cooling 'heat treatment is adopted, and air cooling is changed into air cooling and water cooling. And all process parameters are optimized according to actual conditions. The method has remarkable advantages, the internal structure can be refined, and the strength and toughness are improved; the process stability is ensured, and the production efficiency and the qualification rate are improved; the cost is low, and quality defects and delay are avoided; the defects of traditional heat treatment are overcome, the performance consistency and reliability of forgings are guaranteed, and the requirements of high-end fields are met.

Description

Technical Field

[0001] The present invention relates to a method for preparing high-strength and high-toughness TC21 titanium alloy plates. Background Art

[0002] With the rapid development of modern industry, especially in the fields of aerospace, shipbuilding, high-end equipment, etc., the demand for high-strength and high-toughness metal materials is increasing day by day. As a material with excellent comprehensive properties, TC21 titanium alloy has the advantages of low density, high strength, good corrosion resistance, etc., and has been widely used in these fields. However, there are many problems in the traditional preparation process of TC21 titanium alloy plates. In the forging process, it is difficult to simultaneously meet the requirements of equipment and process parameters in different forging stages, resulting in uneven microstructure and properties of forgings, and unable to meet the strict requirements of high-end applications for material properties. During the forging process, the billet is prone to quality defects due to too fast heat loss, affecting product performance and production efficiency. In the heat treatment process, for large-sized TC21 titanium alloy forgings, the typical heat treatment system recommended by the existing 003 standard cannot effectively guarantee the properties of the core of the forgings, restricting the application of the material in large structural parts. Therefore, it is of great practical significance and application value to develop a method for preparing high-strength and high-toughness TC21 titanium alloy plates that can overcome the above problems. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing high-strength and high-toughness TC21 titanium alloy plates to solve the problems mentioned in the above background art.

[0004] To solve the above technical problems, the technical solution provided by the present invention is: a method for preparing high-strength and high-toughness TC21 titanium alloy plates, including the following steps:

[0005] Forging process: fully analyze the requirements of the microstructure and properties of the forgings, the characteristics of the microstructure evolution of TC21 titanium alloy under different forging processes, equipment capabilities, on-site production environment conditions, and the specifications and states of raw materials, and formulate a "low-low-high" combined forging process; specifically, the first heat is subjected to α+β forging on a 5000T hydraulic press, the middle two and three heat treatments are subjected to α+β forging on a 3T open-die forging hammer, and the last heat is subjected to near-β forging on a 5000T hydraulic press; among them, forging below the β transformation point is "low" forging, and forging above the β transformation point is "high" forging;

[0006] Anti-heat-loss process: During the near-β forging process, in order to prevent the billet from losing heat too fast, the "asbestos sticky jacket" forging process method is adopted, and the billet is wrapped with asbestos sticky for forging to avoid the billet from coming into large-area contact with the air and the workbench surface and quickly cooling down;

[0007] Heat treatment process: For large-sized TC21 titanium alloy forgings, when the typical heat treatment system recommended by the 003 standard cannot meet the performance requirements of the forging core, the "air and water combined cooling" heat treatment process system is adopted; that is, the cooling method of the first-stage annealing (high-temperature annealing) is changed from air cooling to air cooling + water cooling, cooled in air to 710 - 680 °C, and then transferred to water for cooling, with the water temperature of 20 - 40 °C.

[0008] Preferably, the specific parameters of each forging pass in the "low-low-high" combined forging process are precisely adjusted according to the various factors analyzed above.

[0009] Preferably, the thickness and wrapping method of the asbestos paste in the "asbestos paste wrapped sleeve" are determined based on the standard of being able to effectively prevent the blank from losing temperature too quickly during the near-β forging process.

[0010] Preferably, in the "air and water combined cooling" heat treatment process, the cooling time in air and the cooling time in water are optimized according to the specifications and performance requirements of the forgings.

[0011] The advantages of the present invention are as follows: The performance is significantly improved: Through the "low-low-high" combined forging process, the advantages of different forging equipment are fully utilized, the forging process is precisely controlled, the internal structure of the TC21 titanium alloy plate is uniformly refined, the strength and toughness of the plate are greatly improved, and the strict requirements for high-performance materials in high-end fields are met.

[0012] The process stability is strong: During the forging process, the forging parameters of each pass are precisely adjusted according to various factors, ensuring the stability and repeatability of the process, effectively reducing the fluctuation of product quality, and improving production efficiency and product qualification rate.

[0013] The cost control is effective: The "asbestos paste wrapped sleeve" forging process method is simple and easy to implement, with low cost. It can not only effectively prevent the blank from losing temperature too quickly, but also avoid product quality defects and production delays caused by temperature problems, indirectly reducing the production cost.

[0014] The heat treatment is highly targeted: The "air and water combined cooling" heat treatment process is tailored to the problem that the core performance requirements of large-sized TC21 titanium alloy forgings cannot be met, effectively solving the deficiencies of the traditional heat treatment system, and ensuring the consistency and reliability of the overall performance of the forgings. Specific embodiments

[0015] For the purposes of the following detailed description, it should be understood that the present invention may take various alternative variations and step sequences, unless expressly specified to the contrary. In addition, except where otherwise indicated in any operating instance or otherwise, all numbers representing quantities of ingredients used in the specification and claims, for example, should be understood to be modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0016] While the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0017] In addition, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0018] Example 1

[0019] Raw materials: Select a billet of TC21 titanium alloy with a specific specification of a certain batch, and its initial microstructure state is uniform.

[0020] Forging process: The first heat is carried out on a 5000T hydraulic press, and the α+β forging temperature is set 20°C below the phase transformation point, with a strain rate of 0.01 / s; the middle two and three heat treatments are carried out on a 3T open-die forging hammer, and the forging temperature is maintained at 25°C below the phase transformation point, with a strain rate of 0.02 / s; the last heat is carried out on a 5000T hydraulic press for near-β forging, with a temperature of 15°C above the phase transformation point and a strain rate of 0.015 / s.

[0021] Heat loss prevention process: Use asbestos felt with a thickness of 5mm and wrap the billet in a spiral winding manner.

[0022] Heat treatment process: For forgings with a specification of 500×300×50mm, cool in air for 30 min to 700°C, and then transfer to water at 30°C and cool for 20 min.

[0023] Example 2

[0024] Raw materials: Replace with another batch of TC21 titanium alloy billets with slightly different specifications.

[0025] Forging process: The first heat is carried out on a 5000T hydraulic press. The α+β forging temperature is 15°C below the phase transformation point, and the strain rate is 0.012 / s. The intermediate heat treatment is carried out on a 3T open-die forging hammer. The temperature is 22°C below the phase transformation point, and the strain rate is 0.025 / s. The final heat treatment is carried out at a quasi-β forging temperature of 18°C above the phase transformation point, and the strain rate is 0.018 / s.

[0026] Heat loss prevention process: The thickness of the asbestos adhesive is 6mm, and the cross-wrapping method is adopted.

[0027] Heat treatment process: For forgings with a specification of 400×250×40mm, air-cool for 25min to 690°C, and then cool in water at 25°C for 15min.

[0028] Example 3

[0029] Raw materials: Select the same specification TC21 titanium alloy billets provided by different suppliers.

[0030] Forging process: The α+β forging temperature of the first heat is 25°C below the phase transformation point, and the strain rate is 0.008 / s. The temperature of the intermediate heat treatment is 30°C below the phase transformation point, and the strain rate is 0.03 / s. The final heat treatment is carried out at a quasi-β forging temperature of 20°C above the phase transformation point, and the strain rate is 0.02 / s.

[0031] Heat loss prevention process: The thickness of the asbestos adhesive is 4mm, and the double-layer wrapping method is adopted.

[0032] Heat treatment process: For forgings with a specification of 600×350×60mm, air-cool for 35min to 710°C, and then cool in water at 35°C for 25min.

[0033] Example 4

[0034] Raw materials: Use specific pre-treated TC21 titanium alloy billets.

[0035] Forging process: The α+β forging temperature of the first heat is 18°C below the phase transformation point, and the strain rate is 0.011 / s. The temperature of the intermediate heat treatment is 28°C below the phase transformation point, and the strain rate is 0.028 / s. The final heat treatment is carried out at a quasi-β forging temperature of 16°C above the phase transformation point, and the strain rate is 0.016 / s.

[0036] Heat loss prevention process: The thickness of the asbestos adhesive is 7mm, and the tightly fitting wrapping method is adopted.

[0037] Heat treatment process: For forgings with a specification of 350×200×30mm, air-cool for 20min to 680°C, and cool in water at 22°C for 12min.

[0038] Example 5

[0039] Raw materials: Select small-sized TC21 titanium alloy billets.

[0040] Forging process: For the first heating α+β forging, the temperature is 22°C below the phase transformation point, and the strain rate is 0.009 / s; for the intermediate heating, the temperature is 26°C below the phase transformation point, and the strain rate is 0.022 / s; for the last heating near-β forging, the temperature is 17°C above the phase transformation point, and the strain rate is 0.017 / s.

[0041] Heat loss prevention process: The thickness of the asbestos adhesive is 3 mm, and the simple wrapping method is adopted.

[0042] Heat treatment process: For forgings with a specification of 200×150×20 mm, air-cool for 15 min to 695°C, and then cool in water at 28°C for 10 min.

[0043] Example 6

[0044] Raw materials: Use specially processed TC21 titanium alloy billets.

[0045] Forging process: For the first heating α+β forging, the temperature is 16°C below the phase transformation point, and the strain rate is 0.013 / s; for the intermediate heating, the temperature is 24°C below the phase transformation point, and the strain rate is 0.026 / s; for the last heating near-β forging, the temperature is 19°C above the phase transformation point, and the strain rate is 0.019 / s.

[0046] Heat loss prevention process: The thickness of the asbestos adhesive is 8 mm, and the special reinforcement wrapping method is adopted.

[0047] Heat treatment process: For forgings with a specification of 450×300×45 mm, air-cool for 32 min to 705°C, and then cool in water at 32°C for 22 min.

[0048] Example 7

[0049] Raw materials: Select TC21 titanium alloy billets with slightly different trace element contents.

[0050] Forging process: For the first heating α+β forging, the temperature is 23°C below the phase transformation point, and the strain rate is 0.014 / s; for the intermediate heating, the temperature is 27°C below the phase transformation point, and the strain rate is 0.024 / s; for the last heating near-β forging, the temperature is 14°C above the phase transformation point, and the strain rate is 0.013 / s.

[0051] Heat loss prevention process: The thickness of the asbestos adhesive is 5.5 mm, and the semi-wrapping method is adopted.

[0052] Heat treatment process: For forgings with a specification of 550×320×55 mm, air-cool for 33 min to 708°C, and then cool in water at 38°C for 23 min.

[0053] Example 8

[0054] Raw materials: Recycled TC21 titanium alloy billets are used.

[0055] Forging process: For the first heat, the α+β forging temperature is 17°C below the phase transformation point, and the strain rate is 0.015 / s; for the intermediate heat, the temperature is 23°C below the phase transformation point, and the strain rate is 0.027 / s; for the last heat, the near-β forging temperature is 13°C above the phase transformation point, and the strain rate is 0.012 / s.

[0056] Anti-temperature-drop process: The thickness of the asbestos felt is 4.5 mm, and the overlapping wrapping method is adopted.

[0057] Heat treatment process: For forgings with a specification of 300×220×35 mm, air-cool for 28 min to 685°C, and then cool in water at 26°C for 18 min.

[0058] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a high-strength and tough TC21 titanium alloy sheet, characterized in that: The following steps are involved: Forging process: Fully analyze the requirements for forging structure and performance, the structural evolution characteristics of TC21 titanium alloy under different forging processes, equipment capabilities, on-site production environment conditions and raw material specification and status factors, and formulate a "low-low-high" combined forging process; specifically, the first fire is α+β forging on a 5000T hydraulic press, the second and third fires are α+β forging on a 3T free forging hammer, and the last fire is quasi-β forging on a 5000T hydraulic press; forging below the β phase transformation point is "low" forging, and forging above the β phase transformation point is "high" forging; Preventing temperature loss process: In the quasi-β forging process, in order to prevent the blank from losing temperature too quickly, the "asbestos sticky jacket" forging process method is adopted. The blank is wrapped with asbestos for forging to avoid large-area contact between the blank and the air and the work surface and rapid cooling; Heat treatment process: For large-sized TC21 titanium alloy forgings, when the typical heat treatment system recommended by the 003 standard cannot meet the performance requirements of the core of the forgings, the "air and water combined cooling" heat treatment process system is adopted; that is, the primary annealing (high temperature annealing) cooling method is changed from air cooling to air cooling + water cooling, cooling in air to 710-680℃, and then transferred to water for cooling, with a water temperature of 20-40℃.

2. The method for preparing a high-strength and tough TC21 titanium alloy sheet according to claim 1, characterized in that: The specific parameters of each forging fire in the "low-low-high" combined forging process are accurately adjusted based on the multiple factors analyzed.

3. The method for preparing a high-strength and tough TC21 titanium alloy sheet according to claim 1, characterized in that: The thickness and wrapping method of the asbestos adhesive in the "asbestos adhesive sheath" are determined based on the standard of being able to effectively prevent the blank from losing temperature too quickly during the quasi-β forging process.

4. The method for preparing a high-strength and tough TC21 titanium alloy sheet according to claim 1, characterized in that: In the "air and water combined cooling" heat treatment process, the cooling time in the air and the cooling time in the water are optimized according to the specifications and performance requirements of the forgings.