Large-size titanium alloy high-cylinder ring piece equiaxial biphase structure precision control method

Abstract

The application discloses a large-size titanium alloy high-cylinder ring piece equiaxial bimodal microstructure precision control method, which comprises the following steps: S1, a jig expanding hole pre-microstructure control process; S2, a first pre-rolling process; S3, a second pre-rolling process; and S4, a final rolling microstructure homogenization and finishing process. After the ring piece is treated through the step S3, composite heat preservation treatment is carried out, and then three-stage variable-speed ring rolling is carried out below 30-50 DEG C of the beta phase transition point, and the single fire deformation amount is 15-25%. The three-stage variable-speed ring rolling is that the deformation rate of the first stage bite stable period is 1-3 mm / s, the deformation rate of the second stage rapid expansion period is 3-6 mm / s, and the deformation rate of the third stage finishing sizing period is 1-3 mm / s. The application provides a manufacturing method which can precisely control the microstructure of a large-size titanium alloy high-cylinder ring piece, obtain uniform and small equiaxial bimodal microstructure, and significantly reduce anisotropy.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing, specifically relating to a method for manufacturing large-size titanium alloy high-cylinder rings, and particularly to a hot working method that can precisely control its microstructure to obtain an equiaxed bimorphic structure and reduce anisotropy. Background Technology

[0002] Titanium alloys, due to their high specific strength, good corrosion resistance, and excellent high-temperature performance, have become key structural materials in national strategic fields such as aerospace, deep-sea engineering, and nuclear power equipment. Among them, large-size, high-cylinder titanium alloy rings are critical load-bearing components in core equipment such as aero-engine casings and rocket body connecting rings. As my country's high-end equipment develops towards larger size, lighter weight, and higher reliability, the performance requirements for ultra-large-size, high-cylinder, thin-walled rings with a single weight ≥10t and a height ≥1300mm are constantly increasing, demanding uniform mechanical properties, extremely low anisotropy, and excellent fatigue performance.

[0003] Currently, the microstructure control of titanium alloy rings is mainly achieved by controlling process parameters such as forging temperature, deformation amount, and deformation rate. The mainstream technical routes include the following:

[0004] ① β Single-phase region forging technology

[0005] The billet is heated to 20-50°C above the β-phase transformation point and then forged, utilizing the high plasticity of the β-phase to achieve large deformation. This technique has low deformation resistance and is easy to form, making it the main method for the early production of titanium alloy rings.

[0006] ② α+β two-phase region forging technology

[0007] The billet is heated to 30-100℃ below the β-phase transformation point and then forged. By controlling the deformation and cooling rate, a bimodal microstructure is obtained. This technique can improve the plasticity and toughness of the material to a certain extent and is currently the most widely used titanium alloy forging technique.

[0008] ③Isothermal forging technology

[0009] Forging involves simultaneously heating the die and the billet to the same temperature and maintaining this temperature constant, resulting in an extremely low deformation rate (typically ≤0.01 s⁻¹). This technique yields a very uniform microstructure and excellent mechanical properties, and is primarily used to manufacture small forgings with complex shapes and high performance requirements.

[0010] ④ Multi-fire rolling technology

[0011] The grain structure is refined by gradually accumulating deformation through multiple heating and rolling processes. This technology is the main forming method for the production of large-size ring parts, and the final microstructure is controlled by adjusting the deformation amount and temperature of each heating cycle.

[0012] The aforementioned existing technologies have achieved certain results in the production of small and medium-sized titanium alloy rings, but when applied to large-sized tall cylindrical thin-walled rings with a single weight ≥10t and a height ≥1300mm, they all have insurmountable defects:

[0013] ① β-single-phase forging: coarse microstructure, poor toughness

[0014] Disadvantages: If the forging temperature is too high, the β grains will grow rapidly, forming a coarse Widmanstätten structure after cooling. Although this structure has high strength, its plasticity and toughness will decrease by more than 30%, and it will also exhibit severe anisotropy and low fatigue life.

[0015] The root cause is that the β single-phase region lacks the pinning effect of the primary α phase, allowing β grain boundaries to migrate and grow freely. Once coarse grains are formed, they cannot be completely eliminated through subsequent heat treatment.

[0016] ② Traditional α+β two-phase forging: uneven microstructure and insufficient core deformation

[0017] Disadvantages: The surface deformation of the ring is sufficient to obtain a fine equiaxed structure; however, the core deformation is usually less than 10%, and it still retains the original cast structure or coarse lamellar structure, with the difference in structure across the entire cross section exceeding 50%. At the same time, due to the rapid temperature drop, the α phase lamellars cannot be fully spheroidized, and the proportion of equiaxed α phase is usually only 60-70%.

[0018] The root cause is that the walls of large-sized rings are thick, making it difficult for deformation to penetrate into the core; in addition, the deformation window of titanium alloys is narrow, and traditional processes lack effective heat preservation measures. The temperature drops too quickly after the billet leaves the furnace, the deformation time is short, and the dynamic recrystallization and α-phase spheroidization processes are insufficient.

[0019] ③Isothermal forging: High equipment cost, low efficiency, and unable to produce large-size products.

[0020] Disadvantages: It requires specialized isothermal forging equipment and high-temperature resistant molds, with equipment investment 5-10 times that of conventional equipment; moreover, the deformation rate is extremely low, the production cycle is as long as several days, and the efficiency is extremely low. Currently, the largest isothermal forging equipment can only produce forgings with a diameter ≤2m, which cannot meet the production needs of large-specification rings with a diameter ≥5m.

[0021] The root cause is that the principle of isothermal forging technology dictates that it must be carried out under low-speed and constant-temperature conditions, which is fundamentally contradictory to the demand for high-efficiency and low-cost production of large-size ring parts.

[0022] ④ Traditional multi-fire rolling: strong texture and severe anisotropy

[0023] Disadvantages: During the rolling process, the ring mainly undergoes circumferential deformation, forming a strong fibrous texture, resulting in a difference of more than 15% between radial and axial mechanical properties, with an anisotropy coefficient ≥1.15. This anisotropy can cause the ring to easily break along the axial direction during service, seriously affecting the safety of the equipment.

[0024] The root cause is that traditional rolling uses a single, constant deformation rate, during which grains are oriented along the deformation direction, forming a strong preferred orientation; and there is no effective texture weakening mechanism, so the anisotropy generated during rolling cannot be eliminated.

[0025] In summary, existing technologies cannot simultaneously solve the three core problems of "microstructure uniformity, α-phase spheroidization rate, and anisotropy" in the production of large-size titanium alloy high-cylinder rings, which have become key technological bottlenecks restricting the development of high-end equipment in my country. Summary of the Invention

[0026] The present invention aims to solve the problems existing in the prior art and provide a manufacturing method that can precisely control the microstructure of large-size titanium alloy high cylindrical ring parts, obtain a uniform and fine equiaxed bimodal structure, and significantly reduce anisotropy.

[0027] To achieve the above objectives, the present invention provides the following technical solution:

[0028] This invention is applicable to the preparation of large-size titanium alloy high-cylinder rings with a single weight ≥10000kg, a height ≥1300mm, and a height-to-thickness ratio ≥10:1. The following uses TC4 titanium alloy (β phase transformation point 970-990℃) as an example to explain the specific preparation steps and process conditions in detail. All parameters have been verified in production and can be directly used for industrial production.

[0029] A method for precise control of the equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings includes the following steps:

[0030] Raw material preparation:

[0031] Titanium alloy ingots were produced through a three-stage vacuum arc remelting process, with a chemical composition conforming to GB / T 3620.1-2016 standard. The ingots were then forged into ring billets. The cold-formed dimensions of the ring billets were: outer diameter 2500-3000 mm, inner diameter 2000-2500 mm, height 1350 mm, and a single weight of 10800 kg.

[0032] Step 1: Pre-structure control process for hole enlargement using a frame

[0033] Furnace loading and heating: After applying coating, the ring billet is loaded into the bogie-type electric furnace. The loading quantity is ≤1 piece. Spacers are evenly distributed along the circumference with equal spacing. The heating temperature is controlled at 30-50℃ below the β phase transformation point, the heating rate is ≤150℃ / h, and the holding time is calculated based on the effective wall thickness.

[0034] Forging with an anvil: The anvil is expanded using a high-speed forging press with a large flat anvil. The length of the anvil head is strictly parallel to the axial direction of the ring to ensure uniform axial deformation. A total of 4 forging passes are performed, with a total deformation of 25-35%, preferably 30%. The final forging temperature is ≥800℃.

[0035] Step 2: First pre-rolling

[0036] Surface pretreatment: The entire surface of the ring blank is ground and cleaned. The aspect ratio of all surface defects (cracks, folds, pits, etc.) after grinding and repair must be ≥8 to completely eliminate stress concentration at the tip of the defect.

[0037] Composite insulation treatment: Apply two layers of high-temperature resistant ceramic insulation coating evenly to the entire surface of the blank, with each layer being 0.5-1mm thick, and allow it to dry at room temperature for 3 hours. After the coating is completely dry, wrap the two ends and outer circumference of the ring with insulation cotton and secure it with stainless steel wire. Do not wrap the inner circumference.

[0038] Loading and heating: The processed billets are loaded into the bogie-type electric furnace, and the heating temperature is controlled at 30-50℃ below the β phase transformation point.

[0039] Rolling preparation: Before rolling, the φ10m CNC diameter axial ring rolling mill is calibrated with a standard measuring ring to ensure a calibration accuracy of ≤0.5mm. At the same time, the main roll, core roll, and guide roll are preheated to 250-300℃ and held at that temperature for more than 2 hours to prevent localized rapid cooling caused by contact between the high-temperature billet and the cold tooling.

[0040] Rolling process: A three-stage variable-rate rolling process is adopted: the first stage (biting-in stabilization period) is 1-3 mm / s, until the ring is fully engaged with the tooling and rotates stably; the second stage (rapid diameter expansion period) is 3-6 mm / s, until the outer diameter of the ring reaches 95% of the predetermined size; the third stage (finishing and sizing period) is 1-3 mm / s, until the final size is achieved. The deformation per rolling pass is 15-25%, preferably 20%, and the final rolling temperature is ≥800℃.

[0041] Post-processing: After rolling, air cool to room temperature to remove surface oxide scale and residual insulation material.

[0042] Step 3: Second pre-rolling

[0043] Surface pretreatment: Grinding and cleaning the ring after one pre-rolling.

[0044] Composite insulation treatment: Repeat the above steps for composite insulation treatment.

[0045] Furnace loading and heating: The heating temperature is controlled at 30-50℃ below the β phase transformation point, and the holding time is calculated based on the effective wall thickness.

[0046] Rolling preparation: Repeat step 3.4 for equipment calibration and tooling preheating.

[0047] Rolling process: The same three-stage variable rate rolling is adopted, the deformation per hot pass is 15-25%, preferably 20%, and the final rolling temperature is ≥800℃.

[0048] Post-processing: After rolling, air cool to room temperature to remove surface oxide scale and residual insulation material.

[0049] Step 4: Final rolling process for homogenization and finishing

[0050] Surface pretreatment: The rings after secondary pre-rolling are ground and cleaned, and the surface is inspected to confirm that there are no defects.

[0051] Composite insulation treatment: Repeat step 3.2 for composite insulation treatment.

[0052] Furnace loading and heating: A special 12-point support ring with equal-height pads is used. The surface of the pads is completely in contact with the rings to prevent permanent deformation due to its own weight during heating. The heating temperature is controlled at 30-50℃ below the β phase transition point.

[0053] Rolling preparation: Repeat step 3.4 for equipment calibration and tooling preheating.

[0054] Rolling process: Three-stage variable rate rolling is adopted, with a single-pass deformation of 15-25%, preferably 20%, and a final rolling temperature ≥800℃.

[0055] Post-processing: After rolling, air cool to room temperature to remove surface oxide scale and residual insulation material.

[0056] Step 5: Annealing heat treatment and inspection

[0057] Annealing heat treatment: The final rolled ring is placed in a bogie-type electric furnace for annealing heat treatment at 700-800℃ for 2 hours, followed by air cooling to room temperature. This annealing process effectively eliminates residual stress generated during rolling, stabilizes the bimodal structure of the equiaxed α phase, prevents deformation during subsequent machining and service, and further improves the plasticity and toughness of the material without altering the proportion and morphology of the equiaxed α phase.

[0058] The method of the present invention is particularly suitable for the preparation of large-size titanium alloy high cylindrical rings with a single weight ≥10000kg, a height ≥1300mm, and a height-to-thickness ratio ≥10:1.

[0059] The present invention also protects large-size titanium alloy high-cylinder rings prepared according to any of the above methods, wherein the microstructure of the rings is an equiaxed bimorphic structure, wherein the area ratio of the equiaxed α phase is 45-55%, the microstructure difference of the entire cross section of the rings is ≤10%, and the anisotropy coefficient is ≤1.05.

[0060] The beneficial effects of this invention are:

[0061] This invention proposes for the first time a precise control method for equiaxed dual-state microstructure based on "gradient deformation in the low-temperature two-phase region throughout the entire process + near-isothermal rolling + variable rate control", achieving the following significant technical effects:

[0062] ① Significantly improved tissue uniformity, with tissue variation across the entire cross-section ≤10%.

[0063] Advantages: Both the surface and core of the ring part have a uniform and fine equiaxed bimorphic structure, with an average grain size controlled at 10-20 μm, which optimizes the problem of "sufficient surface deformation and insufficient core deformation" in traditional processes.

[0064] Technical principle: The total deformation is distributed according to the method of expanding the hole using a frame (25-30%) + three ring rolling processes (40-50%), allowing the deformation to gradually penetrate from the surface to the core, ensuring sufficient dynamic recrystallization across the entire cross-section. Simultaneously, the entire process is carried out at 30-50℃ below the β phase transformation point, where the dispersed primary α phase particles always act as "pinning particles," strongly inhibiting the coarsening of β grains.

[0065] ② Anisotropy is significantly reduced, with the anisotropy coefficient ≤ 1.05

[0066] Advantages: The difference in room temperature tensile strength between the chordal and axial directions of the ring is ≤5%, and the difference in yield strength is ≤6%. The directionality of mechanical properties is basically eliminated, and the service safety and reliability of the product are greatly improved.

[0067] Technical principle: A three-stage variable-rate rolling process of "1~3mm / s→3~6mm / s→1~3mm / s" is adopted to avoid the formation of strong texture at a single rate. At the same time, the low-speed finishing stage promotes the uniform growth of recrystallized grains, further weakens the deformation texture, and significantly reduces anisotropy.

[0068] ③ High production efficiency and low cost, suitable for large-scale industrial production.

[0069] Advantages: No dedicated isothermal forging equipment is required; production can be achieved using existing conventional fast forging mills and ring rolling mills.

[0070] Technical principle: The composite heat preservation technology solves the problem of excessive temperature drop in titanium alloys, significantly increases the deformation amount per heat treatment, and reduces the number of reheating cycles; at the same time, the three-stage variable rate rolling maximizes production efficiency while ensuring product quality.

[0071] This invention achieves precise control over the microstructure of titanium alloys through the synergistic effect of multiple processes, resulting in technical effects that traditional processes cannot achieve. Its core advantages and underlying mechanisms are as follows:

[0072] 1. The equiaxed α phase ratio is precisely controllable, breaking through the bottleneck of polarization in traditional processes.

[0073] Beneficial effects: It completely solves the polarization problem of the equiaxed α phase ratio in traditional processes being either <30% or >70%, and achieves the optimal range of 45-55% for the equiaxed α phase ratio of titanium alloys used in marine engineering applications.

[0074] Deeper Mechanism:

[0075] This invention achieves precise control of the equiaxed α-phase ratio through mechanisms such as temperature control and deformation control.

[0076] Temperature control mechanism: Forging is controlled at 30-50℃ or below the β phase transformation point, avoiding the complete dissolution of the α phase caused by forging in the β single-phase region and the excessively high initial content of the α phase caused by forging at too low a temperature.

[0077] Deformation control mechanism: The total deformation is distributed in a gradient of "30%→20%→20%→20%". Each deformation is just enough to fully break the α phase layer, but will not cause excessive deformation and excessive spheroidization of the α phase.

[0078] 2. Significantly improved uniformity of microstructure across the entire cross-section, effectively addressing the challenge of microstructure stratification.

[0079] Beneficial effect: The difference in the equiaxed α phase ratio between the surface of the ring and the core is ≤10%, resulting in a uniform microstructure.

[0080] Deeper Mechanism:

[0081] The fundamental reasons for uneven microstructure distribution in traditional processes are "insufficient deformation penetration due to large single deformation" and "premature termination of core deformation due to excessively rapid temperature drop." This invention solves this problem through the following two mechanisms:

[0082] Gradient deformation penetration mechanism: Multiple small-increment deformations gradually transfer deformation from the surface to the core, reaching the critical strain requirements for dynamic recrystallization and α-phase spheroidization, allowing the core to undergo sufficient microstructural evolution.

[0083] Full-process temperature uniformity mechanism: The full-process low-temperature forging and composite heat preservation technology ensure the temperature uniformity of the entire cross section of the ring, avoids premature termination of deformation caused by excessively low core temperature, and allows the microstructure evolution process of the entire cross section to proceed synchronously.

[0084] 3. The deformation texture is effectively weakened, fundamentally reducing the anisotropy of mechanical properties.

[0085] Beneficial effects: The difference in room temperature tensile strength between the radial and axial sides of the ring is ≤5%, the difference in yield strength is ≤6%, and the anisotropy coefficient is reduced from the traditional ≥1.15 to ≤1.05, which basically eliminates the directionality of mechanical properties.

[0086] Deeper Mechanism:

[0087] Traditional single-rate rolling causes grains to align circumferentially, forming a strong fibrous texture, which is the root cause of anisotropy. This invention weakens the deformation texture in two ways through three-stage variable-rate rolling:

[0088] Breaking the continuous directional deformation: The variable rate mode of "low speed → medium speed → low speed" avoids continuous directional deformation at a single rate, allowing grains to undergo multiple dynamic recrystallizations at different deformation rates, disrupting the preferred orientation of the grains. Promoting random recrystallization: The low deformation rate in the low-speed biting and low-speed finishing stages allows for sufficient dynamic recrystallization, resulting in random nucleation and growth of recrystallized grains, further weakening the deformation texture and making the grain orientation more uniform.

[0089] 4. Optimal matching of comprehensive mechanical properties significantly improves product service reliability.

[0090] Beneficial effects: It achieves the best match of strength, plasticity, toughness and fatigue properties, with room temperature tensile strength ≥900MPa, yield strength ≥800MPa, reduction of area ≥20%, and impact toughness ≥30J.

[0091] Deeper Mechanism:

[0092] The comprehensive mechanical properties of TC4 titanium alloy are determined by its microstructure. The bimodal microstructure with 45-55% equiaxed α phase is the microstructure that achieves the optimal match of properties.

[0093] Equiaxed α phase has good plasticity and toughness, which can effectively hinder crack propagation and improve the impact resistance and fatigue performance of materials.

[0094] The transformed β matrix has high strength, which can ensure the load-bearing capacity of the material.

[0095] The uniform and fine microstructure avoids localized stress concentration, reduces the possibility of crack initiation, and significantly improves the service reliability of the material.

[0096] In contrast, Widmanstätten microstructure obtained by traditional β single-phase forging has high strength but poor plasticity and toughness; while equiaxed microstructure obtained by traditional two-phase large deformation forging has good plasticity but insufficient strength. The 45-55% equiaxed α-phase bimodal microstructure stably achieved by this invention perfectly balances the contradiction between strength, plasticity, and toughness, meeting the stringent performance requirements of high-end equipment for titanium alloy rings. Attached Figure Description

[0097] Figure 1 This is a microstructure observation diagram of a cross-section at half the height of a ring material;

[0098] Figure 2 This is a microstructure observation diagram of the end section of the ring material. Detailed Implementation

[0099] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0100] Example 1

[0101] This embodiment provides a method for preparing a high-cylinder ring made of TC4 titanium alloy (β phase transformation point 980℃). The target dimensions of the ring are: outer diameter 5000mm, inner diameter 4500mm, height 1500mm, and single weight approximately 11000kg.

[0102] The specific steps are as follows:

[0103] Pre-structure control of the hole enlargement method:

[0104] The ring billet (cold outer diameter 2800mm, inner diameter 2200mm, height 1350mm) was coated and then placed in an electric furnace and heated to 940℃ (40℃ below the β phase transformation point) at a heating rate of 120℃ / h.

[0105] The high-speed forging press unit is used for four-stage forging on a frame, with a large flat anvil, a total deformation of 30%, and a final forging temperature of ≥820℃.

[0106] First pre-rolling:

[0107] Grind and clean the ring blank.

[0108] Composite insulation treatment: Apply two layers of ceramic insulation coating, each layer 0.8mm thick. After drying, wrap the two ends and outer circumference of the ring with insulation cotton and bind with stainless steel wire.

[0109] Place it in an electric furnace and heat it to 940℃.

[0110] The φ10m CNC diameter axial ring rolling mill was calibrated by preheating the main roll, core roll, and guide roll to 280℃ and holding them at that temperature for 2.5 hours.

[0111] Three-stage variable-rate rolling is carried out: the first stage deformation rate is 2 mm / s, the second stage is 4 mm / s, the third stage is 2 mm / s, the single-pass deformation amount is 20%, and the final rolling temperature is ≥810℃.

[0112] After rolling, air cooling is performed to remove the oxide scale and insulation cotton.

[0113] Second pre-rolling: Repeat all operations in step 2.

[0114] Final rolling: Repeat all operations in step 2.

[0115] Annealing heat treatment: The final rolled ring is placed in an electric furnace, heated to 800°C, held for 2 hours, and then air-cooled to room temperature.

[0116] Performance testing

[0117] To systematically evaluate the uniformity of microstructure and mechanical properties of the ring material along its height, a anatomical analysis was performed on the target ring. Samples were taken from the half-height section and the end section of the ring material for room temperature mechanical property testing and microstructural observation. The mechanical property test results at different sampling locations are shown in Tables 1 and 2, and typical microstructure morphology is shown in the attached figures.

[0118] Table 1. Mechanical testing results at the end positions of the ring material.

[0119]

[0120] Table 2. Mechanical test results at the 1 / 2 height position of the ring material.

[0121]

[0122] The test results show that the anisotropy of the chordal and axial strength at different positions of the ring material is extremely weak, with a maximum difference of only 4 MPa. The titanium alloy high-cylinder ring prepared by the method of this invention has a uniform and fine equiaxed bimorphic structure. The equiaxed α phase is stable in the optimal range, with extremely low anisotropy and excellent comprehensive mechanical properties, which fully meet the requirements of high-end equipment.

[0123] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for precise control of the equiaxed dual-state microstructure of a large-size titanium alloy high-cylinder ring, characterized in that, Includes the following steps: S1: Pre-structure control process of reaming and hole expansion, in which the titanium alloy ring billet is heated to 30-50°C below the β phase transformation point and then subjected to reaming and hole expansion forging. The reaming and hole expansion forging is carried out 3-5 times, and the total deformation is 25-35%. S2: The first pre-rolling process involves composite heat preservation treatment on the ring billet after step S1, followed by three-stage variable-rate ring rolling at 30-50℃ below the β phase transformation point, with a single-pass deformation of 15-25%. S3: The second pre-rolling process involves composite heat preservation treatment on the ring after step S2, followed by three-stage variable-rate ring rolling at 30-50℃ below the β phase transformation point, with a single-pass deformation of 15-25%. S4: Final rolling microstructure homogenization and finishing process. The ring piece treated in step S3 is subjected to composite heat preservation treatment, and then three-stage variable rate ring rolling is carried out at 30-50℃ below the β phase transformation point, with a single-pass deformation of 15-25%. The three-stage variable-rate ring rolling process is as follows: the deformation rate during the first stage of the biting stabilization period is 1-3 mm / s, the deformation rate during the second stage of the rapid diameter expansion period is 3-6 mm / s, and the deformation rate during the third stage of the finishing and sizing period is 1-3 mm / s.

2. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1, characterized in that, The total deformation in step S1 is 30%; the deformation per firing in steps S2, S3, and S4 is 20%.

3. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1 or 2, characterized in that, The composite insulation treatment includes: uniformly coating the entire surface of the ring blank or ring part with a high-temperature resistant ceramic insulation coating; after the coating dries, wrapping the two end faces and outer circumference of the ring part with insulation cotton and securing it with metal wire.

4. The method for precise control of equiaxed dual-state microstructure in large-size titanium alloy high-cylinder rings according to claim 3, characterized in that, The high-temperature resistant ceramic insulation coating is applied in two layers, each layer being 0.5-1mm thick.

5. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1, characterized in that, Before the first pre-rolling, second pre-rolling and final rolling processes, the process also includes: preheating the main roll, core roll and guide roll of the ring mill to 250-300°C and holding it at that temperature for more than 2 hours.

6. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1, characterized in that, The final forging or final rolling temperature of the forging, first pre-rolling, second pre-rolling and final rolling processes is ≥800℃.

7. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1, characterized in that, After the final rolling process, an annealing heat treatment process is also included: the final rolled ring is heated to 700-800°C, held at that temperature for 1.5-2.5 hours, and then air-cooled to room temperature.

8. The method for precise control of equiaxed dual-state microstructure of large-size titanium alloy high-cylinder rings according to claim 1, characterized in that, The method is applicable to the preparation of large-size titanium alloy high-cylinder rings with a single weight ≥10000kg, a height ≥1300mm, and a height-to-thickness ratio ≥10:

1.

9. The large-size titanium alloy high-cylinder ring component prepared by the precise control method of equiaxed dual-state microstructure according to any one of claims 1-8, characterized in that, The microstructure of the ring is an equiaxed biphase microstructure, wherein the area ratio of the equiaxed α phase is 45-55%, the microstructure difference of the entire cross section of the ring is ≤10%, and the anisotropy coefficient is ≤1.05.

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