CN111763850A - A kind of processing method of fine-grained superplastic TA15 titanium alloy medium and thick plate - Google Patents

Abstract

The invention discloses a processing method for a fine-grained superplastic TA15 titanium alloy medium-thick plate. The method comprises: first, obtaining a TA15 titanium alloy ingot by vacuum consumable arc melting; The primary forging billet is obtained; 3. The secondary forging billet is obtained by upsetting and forging in the β phase region after heat preservation; 4. The fourth-level forging billet is obtained by upsetting and forging in the α+β two-phase region; ; 6. After heat preservation, the first-fire rolled slab is obtained by rolling with one fire; 7. After heat preservation, the second-fire rolled slab is obtained by rolling with the second fire; Eight, TA15 titanium alloy medium and heavy plate is obtained by annealing. The invention selects the corresponding deformation temperature, and adopts upsetting forging with multiple fires and large deformation, so that the TA15 titanium alloy ingot with coarse structure is broken under large deformation, and provides a driving force for recrystallization and improves the fineness of grains. To obtain a fine-grained superplastic TA15 titanium alloy medium and thick plate.

Description

A kind of processing method of fine-grained superplastic TA15 titanium alloy medium and thick plate

technical field

The invention relates to the technical field of titanium alloy material processing, in particular to a processing method for a fine-grained superplastic TA15 titanium alloy medium-thick plate.

Background technique

Because of its high superplasticity, fine-grained titanium alloys can be superplasticized to process thin-walled structural parts, which are widely used to replace various precision castings and forgings of aircraft, and are used to manufacture complex structural parts of aircraft such as missile tails and missile casings. To the obvious weight reduction effect, the payload is greatly increased. This type of component generally has the characteristics of high ribs and thin abdomen, complex shape, and large projected area, which requires high tissue performance.

TA15 titanium alloy has good comprehensive mechanical properties, and its strength, fracture toughness, fatigue limit, and stress corrosion resistance are slightly higher than TC4 titanium alloy. Important structural parts with high height and complex stress have been widely used in China. Among them, sheet metal is the most widely used, mainly used in key aviation components such as engine casings and welded load-bearing frames. However, due to the large deformation resistance of titanium alloy, narrow deformation temperature range and strong tissue sensitivity in TA15 titanium alloy, problems such as coarse grains and uneven structure are prone to occur in the process of sheet preparation, resulting in unstable quality and yield of medium and thick titanium alloy sheets. Low and superplastic properties are not high, which limits the application of titanium alloy medium and thick plates in high-end fields.

The traditional processing technology of TA15 titanium alloy medium and heavy plate usually adopts unidirectional rolling. The direction of the plate does not change during the rolling process, and the grains are deformed in one direction during the rolling process, resulting in a large difference in the transverse and longitudinal microstructures. , the plate processing streamline is obvious, and the surface of the plate will produce "fleece grooves" along the rolling direction.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a processing method of fine-grained superplastic TA15 titanium alloy medium-thick plate in view of the above-mentioned deficiencies of the prior art. The invention selects the corresponding deformation temperature according to the phase transition temperature, controls the temperature rise caused by the deformation below the phase transition temperature, and then adopts the upsetting forging with multiple fires and large deformation, so that the TA15 titanium alloy ingot with coarse structure can be deformed under large deformation. It is gradually crushed under the same amount, and provides a driving force for the recrystallization of the grains after crushing, so that the degree of grain refinement and homogenization is improved, so that the α phase is fully broken and the structure is refined, making the TA15 titanium alloy medium and thick. The microstructure inside and outside the plate is nearly the same, and finally a fine-grained superplastic TA15 titanium alloy medium-thick plate is obtained.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is: a processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate, characterized in that the method comprises the following steps:

Step 1. Smelting: According to the design composition of the target alloy, the 0-grade titanium sponge and the intermediate alloy are sequentially mixed, electrode pressed and welded, and then TA15 titanium alloy ingot is obtained by three vacuum consumable arc smelting. Clean up local defects on the surface of alloy ingots;

Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into an electric furnace for heating and heat preservation under the conditions of T _β +160 ° C ~ T _β + 180 ° C, and then use a rapid forging of more than 2000t The upsetting billet is forged by the machine, and the primary forging billet is obtained after air cooling; the T _β is the β phase transition temperature of the TA15 titanium alloy, the unit is °C, and the aspect ratio used in the upsetting billet forging is (2 ~ 2.5 ):1;

Step 3. Upsetting and forging in the β phase region: put the primary forging billet obtained in step 2 into an electric furnace for heating and heat preservation under the condition of T _β +60°C ~ T _β +80°C, and then use a fast forging machine with a capacity of more than 2000t Or a press is used for upsetting and forging in the beta phase region, and the secondary forging blank is obtained after air cooling; the height-diameter ratio used in the upsetting and forging in the beta phase region is (2-2.5): 1;

Step 4. Upsetting and forging in the α+β two-phase region: put the secondary forging billet obtained in step 3 into an electric furnace for heating and heat preservation under the condition of T _β -25°C ~ T _β -30°C, and then use more than 2000t The first upsetting forging in the α+β two-phase region is carried out by the fast forging machine or press, and the third-stage forging blank is obtained after cooling, and the third-stage forging blank is continued to be under the condition of T _β -25℃～T _β -30℃ Heating and heat preservation are carried out, and then a fast forging machine or a press of more than 2000t is used for the second upsetting and forging of the α+β two-phase region, and the fourth-stage forging blank is obtained after air cooling; the first upsetting of the α+β two-phase region is performed. The height-diameter ratios used in forging and the second upsetting forging in the α+β two-phase region are both (2-2.5): 1;

Step 5. Final forging: put the four-stage forging billet obtained in step 4 into an electric furnace for heating and heat preservation under the condition of T _β -30 ℃～T _β -40 ℃, and then perform upsetting and final forging forging, and after air cooling A forging is obtained; the height-diameter ratio used in the upsetting and final forging is (2-2.5): 1, and the thickness of the forging is 200-220 mm;

Step 6. One-fire rolling: heat and keep the forging obtained in step 5, and then use a hot rolling mill to perform one-fire rolling for 6 to 8 passes to obtain a one-fire rolled slab; the one-fire rolling The thickness of the slab is 50mm to 80mm;

Step 7, second-fire rolling: the first-fire rolling slab obtained in step 6 is cut and blanked, heated and kept warm, and then 4-6 passes of second-fire rolling are carried out with a hot rolling mill to obtain second-fire rolling. Slab; the thickness of the second-fire rolled slab is 10mm to 25mm;

Step 8, slab treatment: annealing the second-fire rolled slab obtained in step 7, and then performing grinding and shearing treatment in turn to obtain a TA15 titanium alloy medium and heavy plate; the thickness of the TA15 titanium alloy medium and heavy plate It is 10mm to 25mm, the average grain size is not more than 20μm, and the transverse elongation of TA15 titanium alloy medium and thick plate at 850 ℃ ~ 930 ℃ temperature is more than 420%, and the longitudinal elongation is more than 340%.

The typical feature of superplastic sheet is that the structure is fine and uniform. The TA15 titanium alloy is a near-alpha titanium alloy, and it is difficult to adjust its properties by heat treatment. In order to improve the superplastic properties, the present invention performs grain refinement through thermal deformation to improve its superplastic properties.

In the present invention, the TA15 titanium alloy ingot obtained by vacuum consumable arc smelting is successively subjected to billet forging, β-phase region upsetting forging, α+β two-phase region upsetting forging and final forging, and then undergoes one-fire rolling and final forging. Two-fire rolling, and then processed to obtain TA15 titanium alloy medium and heavy plate. The invention selects the corresponding deformation temperature according to the phase transition temperature, controls the temperature rise caused by the deformation below the phase transition temperature, and then adopts the upsetting forging with multiple fires and large deformation, so that the TA15 titanium alloy ingot with coarse structure can be deformed under large deformation. The grains are broken down step by step, and the larger deformation provides a driving force for the recrystallization of the grains after crushing, so that the grain refinement and homogenization degree are improved, so that the α phase is fully broken and the structure is refined, so that the The microstructure inside and outside of the TA15 titanium alloy plate is close to the same and is a fine-grained structure, and a fine-grained superplastic TA15 titanium alloy medium-thick plate is obtained.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that, in the first and second vacuum consumable arc smelting processes of the three vacuum consumable arc smelting described in the step 1. , the vacuum degree in the vacuum consumable arc melting furnace is less than 1.0×10 ^-1 Pa, and in the third vacuum consumable arc melting process, the vacuum degree in the vacuum consumable arc melting furnace is less than 5.0×10 ^-2 Pa; In step 1, smooth transition grinding is performed on the cleaned TA15 titanium alloy ingot, and the aspect ratio of the smooth transition grinding is not greater than 1:10, and the depth is not greater than 10 mm. Through the control of the vacuum degree during the three vacuum consumable arc smelting process, the content of impurity elements in the TA15 titanium alloy ingot is significantly reduced, and the uniformity and stability of the TA15 titanium alloy ingot composition are ensured; this optimal grinding process avoids the subsequent During the forging process, folds and cracks are formed, which affects the quality of the product TA15 titanium alloy medium and thick plate.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that, the heating and heat preservation method described in step 2 is stepped heating, and the step heating process is: controlling the TA15 titanium alloy casting The charging temperature of the ingot is 790℃～810℃, and the ingot is kept at the charging temperature for t ₁ min, and then heated to T _β +160 ℃～T _β +180 ℃ and kept for ₂ min, wherein, t ₁ =(TA15 titanium Alloy ingot diameter/3-10)min～(TA15 titanium alloy ingot diameter/3+10)min, t ₂ =(TA15 titanium alloy ingot diameter/2+30)min～(TA15 titanium alloy ingot diameter/ 2+40) min, the unit of TA15 titanium alloy ingot diameter is mm; the single-pass deformation of the upsetting billet forging is 25% to 30%, and the single-fire cumulative deformation is not less than 80%. Due to the low thermal conductivity and slow thermal conductivity of TA15 titanium alloy at high temperature, it is preferable to use stepped heating to significantly improve the temperature uniformity in the TA15 titanium alloy ingot after heating and heat preservation, and provide a basis for subsequent forging; because the structure of the TA15 titanium alloy ingot is very Coarse, it is preferable to use the above-mentioned process parameters for upsetting and forging, so that the coarse grains of the TA15 titanium alloy ingot after the multi-fire upsetting are broken under a larger amount of deformation, and the larger amount of deformation is after the crushing. Grain recrystallization provides the driving force, and the degree of uniformity of the grains increases.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that the heating and heat preservation method described in the step 3 is stepped heating, and the process of the stepped heating is: first control the loading of the primary forging billet. The furnace temperature is 790℃～810℃, and the temperature is kept at the loading temperature for t ₁ min, and then the temperature is raised to T _β +60 ℃～T _β +80 ℃ and kept for t ₂ min, where t ₁ = (the maximum cross section of the primary forging billet) Size/3-10)min～(Maximum size of primary forging billet section/3+10)min, t ₂ =(Maximum size of primary forging billet section/2+30)min～(Maximum size of primary forging billet section/2+40 )min, the unit of the maximum size of the section of the primary forging billet is mm; the single-pass deformation of the upsetting and forging in the β-phase region is 25% to 40%, and the cumulative deformation in a single fire is not less than 85%; the β-phase The drawing and lengthening forging process of upsetting and drawing forging adopts the deformation method of diagonal chamfering, and the deformation amount is 35% to 40%. Preferably, stepped heating can significantly improve the temperature uniformity in the primary forging billet after heating and heat preservation, and provide a basis for subsequent forging. The degree of homogenization of grains; the preferred elongated forging process adopts the deformation method of diagonal chamfering, which significantly reduces the phenomenon of uneven deformation, eliminates the dead zone of deformation, and improves the uniformity of the structure and the consistency of performance.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that the process of heating and heat preservation of the first upsetting forging in the α+β two-phase region described in the step 4 is: controlling the secondary forging The charging temperature of the billet is 500℃～600℃, and then it is heated to T _β- 25℃～T _β- 30℃ at a rate of 3℃/min～5℃/min and kept for t ₁ min; the t ₁ =( The maximum size of the section of the secondary forging billet/2+30)min～(the maximum size of the section of the secondary forging billet/2+40)min, the unit of the maximum size of the section of the secondary forging billet is mm; The single-pass deformation of one upsetting and forging is 25% to 40%, and the cumulative deformation of a single fire is not less than 85%; the cooling method after the first upsetting and forging of the α+β two-phase region is water cooling. The preferred heating and heat preservation improves the temperature uniformity in the secondary forging billet after heating and heat preservation, and provides a basis for subsequent forging; the preferred first upsetting forging of the α+β two-phase region with large deformation is beneficial to the formation of grains. Fully broken and refined; under the fast cooling rate of water cooling, fine acicular martensite is precipitated in the obtained tertiary forging billet. During processing, it is broken, fractured and spheroidized to form a fine and uniform equiaxed structure.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that the process of heating and heat preservation of the second upsetting forging in the α+β two-phase region described in the step 4 is: controlling the third-level forging The charging temperature of the billet is 450°C to 600°C, and then the temperature is raised to T _β -30° C to T _β -40° C at a rate of 3° C/min to 5° C/min and maintained for t ₂ min; the t ₂ =( The maximum size of the section of the third-stage forging billet/2+30)min～(the maximum size of the section of the third-stage forging billet/2+40)min, the unit of the maximum section size of the third-stage forging billet is mm; The single-pass deformation of the secondary upsetting and drawing forging is 30% to 40%, and the cumulative deformation of a single fire is not less than 85%.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that, the specific process of heating and heat preservation described in step 5 is: controlling the furnace charging temperature of the fourth-stage forging billet to be 450 ℃～600 ℃, Then, at a rate of 3°C/min～5°C/min, the temperature is raised to T _β -30°C～T _β -40°C and kept for t ₀ min; the t ₀ =(fourth-stage forging billet section maximum size/2+30) min～(the maximum size of the section of the fourth-stage forging billet/2+40)min, the unit of the maximum size of the section of the fourth-stage forging billet is mm; The cumulative deformation of the fire is not less than 85%.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that, the heating temperature of the one-fire rolling described in the step 6 is T _β- 40 ℃～T _β- 50 ℃, and the holding time is t ₁ = (forging thickness/0.8-5)min～(forging thickness/0.8+5)min, the holding time is calculated from the time the fourth-grade forging enters the heating furnace and the furnace temperature of the heating furnace is stable; the one-fire rolling process The single-pass deformation of the first to third passes is 20% to 25%, and the remaining single-pass deformation is not less than 8%;

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that the heating temperature of the second-fire rolling described in the step 7 is T _β- 50 ℃～T _β -60 ℃, and the holding time t ₂ = (the thickness of the slab rolled once/0.5-5)min～(the thickness of the slab rolled once/0.5+5)min, the holding time is from the time the slab enters the heating furnace and the furnace temperature of the heating furnace is stable Start calculation; the initial single-pass deformation of the second-fire rolling is 20% to 26%, and the remaining single-pass deformation is 12% to 20%. The second-fire rolling adopts reversing rolling, so that the second-fire rolling The rolling direction is perpendicular to the one-fire rolling direction described in step six. The reversing rolling process is used to significantly reduce the difference between the lateral and longitudinal deformation of the first-fire rolled slab, so that the grains can be deformed more uniformly, and the rolling of the first-fire rolled slab due to the large deformation in one direction is improved. The texture and processing flow lines formed by the system are not conducive to the uniformity of the structure defects, the uniformity of the structure is high, and the difference between the transverse and longitudinal properties of the obtained two-fire rolled slab is small.

The above-mentioned preferred first-fire rolling and second-fire rolling with large deformation ensures that the rolling deformation penetrates deep into the core of the slab, so that the deformation of the rolling cross section is uniform.

The above-mentioned processing method of a fine-grained superplastic TA15 titanium alloy medium-thick plate is characterized in that the temperature of the annealing treatment in step 8 is 850°C to 900°C, and the time is 1h to 1.5h. Due to the large deformation energy accumulated in the process of large deformation, in the above-mentioned preferred heat treatment process, the deformation energy provides the driving force for the spheroidization and recrystallization of grains in the second-fire rolled slab. The effect is good, the recrystallization is sufficient, and the structure is uniform and fine, which solves the problems of uneven structure and inconsistent performance during the rolling process of TA15 alloy sheet.

Compared with the prior art, the present invention has the following advantages:

1. The present invention adopts upsetting forging with multiple fires and large deformation to achieve the purpose of fully breaking the α phase to achieve the purpose of refining the structure, and at the same time making the internal and external structures of the TA15 titanium alloy medium and thick plate close to the same and fine-grained structure, and finally obtain The thickness of the TA15 titanium alloy medium and thick plate is 10mm ~ 25mm, the average grain size is not more than 20μm, and the lateral elongation of the TA15 titanium alloy medium and thick plate at a temperature of 850 ℃ ~ 930 ℃ is more than 420%, and the longitudinal elongation is 340% or more.

2. The invention adopts the reversing rolling process, which significantly reduces the difference between the horizontal and vertical deformation during the rolling process, so that the grains can be deformed more uniformly, and the weave formed by rolling of the sheet due to the large deformation in one direction is improved. Structure, processing streamline and other organizational defects that are not conducive to uniformity, high organizational uniformity, narrowing the gap between the transverse and longitudinal properties of the plate, improving the quality of the plate surface, effectively controlling the difference between the same plate, refining the grains, and reducing the anisotropy of the structure , to improve the yield of the plate, and finally obtain a fine-grained TA15 titanium alloy medium and thick plate.

3. TA15 titanium alloy is more sensitive to deformation temperature, and due to the large deformation resistance and severe deformation temperature rise during the deformation process, it is easy to cause grain growth, which is not conducive to microstructure refinement and improvement of superplasticity. The heating temperature and holding time in the β phase region upsetting forging, the α+β two-phase region upsetting forging, the final forging, the first-fire rolling and the second-fire rolling are strictly limited, and the deformation temperature is optimized according to the transformation temperature. Using the high-temperature plasticity and recrystallization of TA15 titanium alloy, the temperature rise caused by deformation is controlled below the phase transition temperature, so as to prevent the slab from being over-burned and cause the coarsening of the structure, and improve the grain fineness in the structure of the TA15 titanium alloy medium and thick plate. A fine-grained structure with an average grain size of not more than 20 μm is obtained.

4. The present invention strictly limits the pass processing rate of the first-pass rolling and the second-pass rolling, maintains a large pass deformation rate during the initial pass rolling, and uses the high-temperature plasticity of the billet to carry out large deformation rolling. As the temperature of the billet decreases, the deformation rate of the pass decreases, which effectively prevents the billet from cracking due to excessive deformation, and improves the surface quality of the TA15 titanium alloy medium and thick plate while obtaining the fine-grained structure.

5. The TA15 titanium alloy medium-thick plate prepared by the present invention has a uniform structure, fine grains, and an average grain size of ≤20 μm. The mechanical properties and ultrasonic flaw detection level are significantly improved compared with conventional plates, and the process controllability and mass production stability are both good. higher.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

FIG. 1 is a microstructure diagram of a TA15 titanium alloy fine-grained medium-thick plate prepared in Example 1 of the present invention.

2 is a microstructure diagram of a fine-grained medium-thick plate of TA15 titanium alloy prepared in Example 2 of the present invention.

3 is a microstructure diagram of a TA15 titanium alloy fine-grained medium-thick plate prepared in Example 3 of the present invention.

Detailed ways

The aspect ratios in steps 2 to 5 of Examples 1 to 4 of the present invention are the ratio of the length to the diameter of the ingot, or the length and the side length of the square bar-shaped forging billets to be processed correspondingly. Compare.

Example 1

This embodiment includes the following steps:

Step 1. Smelting: According to the design composition of the target alloy, the 0-grade titanium sponge and the intermediate alloy are sequentially subjected to automatic mixing, electrode pressing and welding, and then three vacuum consumable arc smelting to obtain 560mm × 2000mm (diameter × length) The TA15 titanium alloy ingot, wherein the vacuum degree in the vacuum consumable arc melting furnace during the first vacuum consumable arc melting process is 0.07Pa, and the vacuum consumable power consumption during the second vacuum consumable arc melting process The vacuum degree in the arc smelting furnace is 0.05Pa, and the vacuum degree in the vacuum consumable arc smelting process is 0.01Pa during the third vacuum consumable arc smelting process. Clean, and then perform smooth transition grinding, and the aspect ratio of smooth transition grinding is 1:12, and the depth is 8mm;

Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into the electric furnace, control the charging temperature of the ingot to be 800 ° C and keep it at the charging temperature for 180 minutes, then heat up to 1150 ° C and Hold the temperature for 320min, and then use a 2000t fast forging machine for upsetting and forging. After air cooling, a square bar-shaped primary forging blank with a cross-sectional dimension of 460mm×460mm (width×height) is obtained; the T _β is the β phase transformation of the TA15 titanium alloy. The temperature is 980°C, and the height-diameter ratio used in the upsetting blank forging is (2.3-2.5): 1; The cumulative deformation is 84%;

Step 3. Upsetting and forging in the β-phase region: put the square bar-shaped primary forging billet obtained in step 2 into the electric furnace, control the charging temperature of the square bar-shaped primary forging billet to be 810 ° C and keep the temperature at the charging temperature for 150min, Then the temperature was raised to 1050°C and kept for 270min, and then 2000t fast forging machine was used for upsetting and forging in the β-phase region. The height-diameter ratio used in the zone upsetting forging is (2.2-2.5): 1; the single-pass deformation of the β-phase zone upsetting forging is 30%-37%, and the single-fire cumulative deformation is 87%; The drawing and forging process of upsetting and drawing forging in the β-phase region adopts the deformation mode of diagonal chamfering, and the deformation amount is 35% to 37%;

Step 4. Upsetting and forging in the α+β two-phase region: load the square bar-shaped secondary forging billet obtained in step 3 into the electric furnace, control the charging temperature of the square bar-shaped secondary forging billet to be 550 ° C, and then use 4 The temperature was raised to 950°C at a rate of ℃/min and kept for 260min, and then a 2000t fast forging machine was used for the first upsetting and forging in the α+β two-phase region. The third-stage forging billet is put into the electric furnace, and the charging temperature of the square-bar-shaped third-stage forging billet is controlled to be 480 °C, and then the temperature is raised to 940 °C at a rate of 5 °C/min and kept for 270 min. , and then use a 2000t fast forging machine to carry out the second upsetting forging in the α+β two-phase region. After air cooling, a square bar-shaped fourth-stage forging blank with a cross-sectional size of 460mm×460mm (width×height) is obtained; the α+β two The height-diameter ratio used in the first upsetting forging of the phase region is (2-2.2): 1, the single-pass deformation is 28%-35%, and the single-pass cumulative deformation is 88%; the α+β two The height-diameter ratio used in the second upsetting forging in the phase region is (2.3-2.5): 1, the single-pass deformation is 32%-35%, and the single-pass cumulative deformation is 87%;

Step 5. Final forging: Load the square bar-shaped fourth-stage forging billet obtained in step 4 into the electric furnace, control the charging temperature of the square-bar-shaped fourth-stage forging billet to be 600 °C, and then heat up at a rate of 3 °C/min To 940 ℃ and heat preservation for 270min, then final upsetting forging is performed, and after air cooling, a forging with a thickness of 200mm is obtained; the height-diameter ratio used in the final upsetting forging is (2-2.1): 1, and the deformation amount per pass is 30% to 34%, and the cumulative deformation of a single fire is 85%;

Step 6. One-fire rolling: The forging obtained in step 5 is heated and kept at 930°C for 250 minutes, and the holding time is calculated from the time the forging enters the heating furnace and the furnace temperature of the heating furnace is stable, and then the hot rolling mill is used for 7 passes. In the first four passes of the first pass rolling, the single pass deformation of the first pass rolling is 20% to 24%, and the single pass of the last three passes is 20% to 24%. The secondary deformation is 8% to 15%;

Step 7. Two-fire rolling: The first-fire rolling slab obtained in step 6 is cut and unloaded and heated at 920 ° C for 100 minutes. The holding time is from the first rolling slab into the heating furnace and the heating furnace When the furnace temperature is stable, the calculation is started, and then the hot rolling mill is used for 5 passes of second-fire rolling to obtain a second-fire rolled slab with a thickness of 10 mm; the deformation amount of the first three passes of the second-fire rolling is 20% ~24%, and the deformation amount of the last two passes is 14% to 18%; the second-fire rolling adopts reversing rolling, so that the direction of the second-fire rolling is perpendicular to the direction of the first-fire rolling described in step 6;

Step 8. Slab treatment: The second-fire rolled slab obtained in step 7 is annealed at a temperature of 850 ° C for 1 hour, and then subjected to grinding and shearing treatment in turn to obtain a 17 μm average grain size and a thickness of 10 mm. TA15 titanium alloy plate.

Fig. 1 is a microstructure diagram of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example. It can be seen from Fig. 1 that the average grain size of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example is 17 μm. And the organization is uniform.

The TA15 titanium alloy fine-grained medium-thick plate prepared in this example is subjected to a high-temperature tensile test at 880°C under the condition of a strain rate of 1×10 ^-4 /s. The results show that the longitudinal elongation of the TA15 titanium alloy fine-grained medium-thick plate is 440%, and the transverse elongation is 392%, indicating that the TA15 titanium alloy fine-grained medium-thick plate prepared in this example has excellent superplastic properties.

Example 2

This embodiment includes the following steps:

Step 1. Smelting: According to the design composition of the target alloy, the 0-grade sponge titanium and the intermediate alloy are sequentially subjected to automatic mixing, electrode pressing and group welding, and then three vacuum consumable arc smelting to obtain 630mm × 2200mm (diameter × length) The TA15 titanium alloy ingot, wherein the vacuum degree in the vacuum consumable arc melting furnace during the first vacuum consumable arc melting process is 0.08Pa, and the vacuum consumable power consumption during the second vacuum consumable arc melting process The vacuum degree in the arc melting furnace is 0.06Pa, and the vacuum degree in the vacuum consumable arc melting process is 0.02Pa during the third vacuum consumable arc melting process, and then the TA15 titanium alloy ingot is peeled, trimmed and ground. Clean, and then perform smooth transition grinding, and the aspect ratio of smooth transition grinding is 1:15, and the depth is 6mm;

Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into the electric furnace, control the charging temperature of the TA15 titanium alloy ingot to be 810 ° C and keep the temperature at the charging temperature for 210min, and then heat up to 1150 ℃ and hold the temperature for 350min, and then use a 3150t fast forging machine for upsetting and forging. After air cooling, a square bar-shaped primary forging bill with a cross-sectional dimension of 480mm×480mm (width×height) is obtained; the T _β is TA15 titanium alloy. The β phase transition temperature is 980°C, and the aspect ratio used in the upsetting blank forging is (2-2.3): 1; the single-pass deformation of the upsetting blank forging is 25% to 28%, The cumulative deformation of a single fire is 80%;

Step 3. Upsetting and forging in the β-phase region: put the square bar-shaped primary forging billet obtained in step 2 into the electric furnace, control the charging temperature of the square bar-shaped primary forging billet to be 800°C and keep the temperature at the charging temperature for 170min, Then the temperature was raised to 1050°C and kept for 280min, and then 3150t fast forging machine was used for upsetting and forging in the β-phase region. The height-diameter ratio used in the zone upsetting forging is (2.3-2.5): 1; the single-pass deformation of the β-phase zone upsetting forging is 25%-34%, and the single-fire cumulative deformation is 85%; so The above-mentioned β-phase region upsetting and drawing forging process adopts the deformation mode of diagonal chamfering, and the deformation amount is 37% to 40%;

Step 4. Upsetting and forging in the α+β two-phase region: the square bar-shaped secondary forging billet obtained in step 3 is loaded into the electric furnace, and the charging temperature of the square bar-shaped secondary forging billet is controlled to be 500 ° C, and then the temperature is 3 The temperature was raised to 965°C at a rate of ℃/min and kept for 280min, and then a 3150t fast forging machine was used for the first upsetting forging in the α+β two-phase region. The third-stage forging billet is put into the electric furnace, and the charging temperature of the square-bar-shaped third-stage forging billet is controlled to be 600 °C, and then the temperature is raised to 950 °C at a rate of 4 °C/min and kept for 280min. , and then use a 3150t fast forging machine to carry out the second upsetting forging in the α+β two-phase region. After air cooling, a square bar-shaped fourth-stage forging blank with a cross-sectional size of 460mm×460mm (width×height) is obtained; the α+β two The aspect ratio of the first upsetting and drawing forging in the phase region is (2-2.4): 1, the single-pass deformation is 25%-32%, and the single-pass cumulative deformation is 85%; the α+β two The height-diameter ratio used in the second upsetting forging of the phase zone is (2.1-2.4): 1, the single-pass deformation is 30%-35%, and the single-pass cumulative deformation is 85%;

Step 5. Final forging: Load the square bar-shaped fourth-stage forging billet obtained in step 4 into the electric furnace, control the charging temperature of the square-bar-shaped fourth-stage forging billet to be 450°C, and then heat up at a rate of 4°C/min To 950 ℃ and heat preservation for 280min, then final upsetting forging is performed, and after air cooling, a forging with a thickness of 220mm is obtained; the height-diameter ratio used in the final upsetting forging is (2.3-2.5): 1, and the amount of deformation per pass is 35% to 40%, and the cumulative deformation of a single fire is 87%;

Step 6. One-fire rolling: The forging obtained in step 5 is heated and kept at 940°C for 280 minutes, and the holding time is calculated from the time the forging enters the heating furnace and the furnace temperature of the heating furnace is stable, and then the hot rolling mill is used for 8 passes. In the first four passes of the first pass rolling, the single pass deformation amount is 22% to 25%, and the single pass of the last three passes is 22% to 25%. The secondary deformation is 12% to 18%;

Step 7. Two-fire rolling: The first-fire rolling slab obtained in step 6 is cut and unloaded and heated at 940 ° C for 155 minutes. The holding time is from the first rolling slab into the heating furnace and the heating furnace Start the calculation when the furnace temperature is stable, and then use the hot rolling mill to carry out 6 passes of second-fire rolling to obtain a second-fire rolled slab with a thickness of 25mm; the deformation of the first three passes of the second-fire rolling is 20% ～25%, and the deformation amount of the last two passes is 15% to 18%; the second-pass rolling adopts reversing rolling, so that the direction of the second-pass rolling is perpendicular to the direction of the first-pass rolling in step 6.

Step 8. Slab treatment: The second-fire rolled slab obtained in Step 7 is annealed at a temperature of 900° C. for 1.5 hours, and then polished and sheared in turn to obtain an average grain size of 20 μm and a thickness of 25 mm. TA15 titanium alloy plate.

Fig. 2 is a microstructure diagram of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example. It can be seen from Fig. 2 that the average grain size of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example is 20 μm. And the organization is uniform.

The TA15 titanium alloy fine-grained medium-thick plate prepared in this example was subjected to a high-temperature tensile test at 850°C under the condition of a strain rate of 1×10 ^-4 /s, and the results showed that the longitudinal elongation of the TA15 titanium alloy fine-grained medium-thick plate is 421%, and the transverse elongation is 348%, indicating that the TA15 titanium alloy fine-grained medium-thick plate prepared in this example has excellent superplastic properties.

Example 3

This embodiment includes the following steps:

Step 1. Smelting: According to the design composition of the target alloy, the 0-grade titanium sponge and the intermediate alloy are sequentially subjected to automatic mixing, electrode pressing and welding, and then three vacuum consumable arc smelting to obtain 560mm × 2000mm (diameter × length) The TA15 titanium alloy ingot, wherein the vacuum degree in the vacuum consumable arc melting furnace during the first vacuum consumable arc melting process is 0.09Pa, and the vacuum consumable power consumption during the second vacuum consumable arc melting process The vacuum degree in the arc smelting furnace is 0.07Pa, and the vacuum degree in the vacuum consumable arc smelting process is 0.03Pa during the third vacuum consumable arc smelting process. Clean, and then perform smooth transition grinding, and the aspect ratio of smooth transition grinding is 1:13, and the depth is 9mm;

Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into the electric furnace, control the charging temperature of the TA15 titanium alloy ingot to be 790 ° C and keep the temperature at the charging temperature for 196min, and then heat up to 100°C. 1160 ℃ and hold the temperature for 310min, and then use a 3150t fast forging machine for upsetting and forging. After air cooling, a square bar-shaped primary forging blank with a cross-sectional size of 460mm × 460mm (width × height) is obtained; the T _β is the TA15 titanium alloy. The β-phase transition temperature is 980°C, and the aspect ratio used in the upsetting blank forging is (2.2-2.4): 1; the single-pass deformation of the upsetting blank forging is 27%-30%, The cumulative deformation of a single fire is 82%;

Step 3. Upsetting and forging in the β-phase region: put the square bar-shaped primary forging billet obtained in step 2 into the electric furnace, control the charging temperature of the square bar-shaped primary forging billet to be 790 ° C and keep the temperature at the charging temperature for 143min, Then the temperature was raised to 1060°C and kept for 260min, and then 2000t fast forging machine was used for upsetting and forging in the β-phase region. The height-diameter ratio used in the zone upsetting forging is (2-2.3): 1; the single-pass deformation of the β-phase zone upsetting forging is 32%-40%, and the single-fire cumulative deformation is 87%; The drawing and forging process of upsetting forging in the β-phase region adopts the deformation mode of diagonal chamfering, and the deformation amount is 36% to 39%;

Step 4. Upsetting and forging in the α+β two-phase region: the square bar-shaped secondary forging billet obtained in step 3 is loaded into the electric furnace, and the charging temperature of the square bar-shaped secondary forging billet is controlled to be 600° C. The temperature was raised to 950°C at a rate of ℃/min and kept for 270min, and then a 2000t fast forging machine was used for the first upsetting and forging in the α+β two-phase region. The third-stage forging billet is placed in the electric furnace, and the charging temperature of the square-bar-shaped third-stage forging billet is controlled to be 450 °C, and then the temperature is raised to 950 °C at a rate of 3 °C/min and kept for 260min. , and then use a 2000t fast forging machine to carry out the second upsetting forging in the α+β two-phase region. After air cooling, a square bar-shaped fourth-stage forging blank with a cross-sectional size of 460mm×460mm (width×height) is obtained; the α+β two The height-diameter ratio used in the first upsetting forging in the phase region is (2.2-2.5): 1, the single-pass deformation is 32%-40%, and the single-pass cumulative deformation is 86%; the α+β two The height-diameter ratio used in the second upsetting forging in the phase zone is (2.2-2.4): 1, the single-pass deformation is 35%-40%, and the single-pass cumulative deformation is 88%;

Step 5. Final forging: load the square bar-shaped fourth-stage forging billet obtained in step 4 into the electric furnace, control the charging temperature of the square-bar-shaped fourth-stage forging billet to be 500°C, and then heat up at a rate of 5°C/min To 950 ℃ and hold the temperature for 260min, then final upsetting forging is performed. After air cooling, a forging with a thickness of 210mm is obtained; the height-diameter ratio used in the final upsetting forging is (2.2-2.4): 1, and the deformation amount of a single pass is 33% to 36%, and the cumulative deformation of a single fire is 85%;

Step 6. One-fire rolling: The forging obtained in step 5 is heated and kept at 940 ° C for 258 minutes, and the holding time is calculated from the time the forging enters the heating furnace and the furnace temperature of the heating furnace is stable, and then the hot rolling mill is used for 6 passes. In the first four passes, the single pass deformation of the first four passes is 20% to 25%, and the single pass of the last three passes is 20% to 25%. The secondary deformation is 10% to 16%;

Step 7. Two-fire rolling: The first-fire rolling slab obtained in step 6 is sheared and blanked and heated at 930 ° C for 125 minutes. The holding time is from the first rolling slab into the heating furnace and the heating furnace Start the calculation when the furnace temperature is stable, and then use the hot rolling mill to carry out 4 passes of second-fire rolling to obtain a second-fire rolled slab with a thickness of 18 mm; the deformation amount of the first three passes of the second-fire rolling is 22% ～26%, and the deformation amount of the last two passes is 12% to 18%; the second-pass rolling adopts reversing rolling, so that the direction of the second-pass rolling is perpendicular to the direction of the first-pass rolling described in step 6;

Step 8. Slab treatment: The second-fire rolled slab obtained in step 7 is annealed at a temperature of 850 ° C for 1 hour, and then subjected to grinding and shearing treatment in turn to obtain a 17 μm average grain size and a thickness of 18 mm. TA15 titanium alloy plate.

Fig. 3 is a microstructure diagram of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example. It can be seen from Fig. 3 that the average grain size of the TA15 titanium alloy fine-grained medium-thick plate prepared in this example is 17 μm. And the organization is uniform.

The TA15 titanium alloy fine-grained medium-thick plate prepared in this example is subjected to a high temperature tensile test at 930°C under the condition of a strain rate of 1×10 ^-4 /s, and the results show that the longitudinal elongation of the TA15 titanium alloy fine-grained medium-thick plate is 421%, and the transverse elongation is 379%, indicating that the TA15 titanium alloy fine-grained medium-thick plate prepared in this example has excellent superplastic properties.

Example 4

This embodiment includes the following steps:

Step 1. Smelting: According to the design composition of the target alloy, the 0-grade titanium sponge and the intermediate alloy are sequentially subjected to automatic mixing, electrode pressing and welding, and then three vacuum consumable arc smelting to obtain 560mm × 2000mm (diameter × length) The TA15 titanium alloy ingot, wherein the vacuum degree in the vacuum consumable arc melting furnace during the first vacuum consumable arc melting process is 0.07Pa, and the vacuum consumable power consumption during the second vacuum consumable arc melting process The vacuum degree in the arc smelting furnace is 0.05Pa, and the vacuum degree in the vacuum consumable arc smelting process is 0.01Pa during the third vacuum consumable arc smelting process. Clean, and then perform smooth transition grinding, and the aspect ratio of smooth transition grinding is 1:14, and the depth is 10mm;

Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into the electric furnace, control the charging temperature of the ingot to be 800 ° C and keep it at the charging temperature for 176 minutes, then heat up to 1040 ° C and Hold the temperature for 320min, and then use a 2000t fast forging machine for upsetting and forging. After air cooling, a square bar-shaped primary forging blank with a cross-sectional dimension of 460mm×460mm (width×height) is obtained; the T _β is the β phase transformation of the TA15 titanium alloy. The temperature is 980°C, and the height-diameter ratio used in the upsetting blank forging is (2.3-2.5): 1; The cumulative deformation is 84%;

Step 3. Upsetting and forging in the β-phase region: put the square bar-shaped primary forging billet obtained in step 2 into the electric furnace, control the charging temperature of the square bar-shaped primary forging billet to be 810 ° C and keep the temperature at the charging temperature for 150min, Then the temperature was raised to 1140°C and kept for 265min, and then 2000t fast forging machine was used for upsetting and forging in the β-phase region. The height-diameter ratio used in the zone upsetting forging is (2.2-2.5): 1; the single-pass deformation of the β-phase zone upsetting forging is 30%-37%, and the single-fire cumulative deformation is 87%; The drawing and forging process of upsetting and drawing forging in the β-phase region adopts the deformation mode of diagonal chamfering, and the deformation amount is 35% to 37%;

Step 4. Upsetting and forging in the α+β two-phase region: load the square bar-shaped secondary forging billet obtained in step 3 into the electric furnace, control the charging temperature of the square bar-shaped secondary forging billet to be 550 ° C, and then use 4 The temperature was raised to 952°C at a rate of ℃/min and kept for 265min, and then a 2000t fast forging machine was used for the first upsetting and forging in the α+β two-phase region. The third-stage forging billet is placed in the electric furnace, and the charging temperature of the square-bar-shaped third-stage forging billet is controlled to be 480 °C, and then the temperature is raised to 945 °C at a rate of 5 °C/min and kept for 265 minutes. , and then use a 2000t fast forging machine to carry out the second upsetting forging in the α+β two-phase region. After air cooling, a square bar-shaped fourth-stage forging blank with a cross-sectional size of 460mm×460mm (width×height) is obtained; the α+β two The height-diameter ratio used in the first upsetting forging of the phase region is (2-2.2): 1, the single-pass deformation is 28%-35%, and the single-pass cumulative deformation is 88%; the α+β two The height-diameter ratio used in the second upsetting forging in the phase zone is (2.3-2.5): 1, the single-pass deformation is 35%-40%, and the single-pass cumulative deformation is 87%;

Step 5. Final forging: Load the square bar-shaped fourth-stage forging billet obtained in step 4 into the electric furnace, control the charging temperature of the square-bar-shaped fourth-stage forging billet to be 600 °C, and then heat up at a rate of 3 °C/min To 945 ℃ and keep the temperature for 265min, then carry out final upsetting forging, after air cooling, a forging with a thickness of 200mm is obtained; the height-diameter ratio used in the final upsetting forging is (2-2.1): 1, and the amount of deformation per pass is 30% to 34%, and the cumulative deformation of a single fire is 85%;

Step 6. One-fire rolling: The forging obtained in step 5 is heated and kept at 935°C for 250 minutes, and the keeping time is calculated from the time the forging enters the heating furnace and the furnace temperature of the heating furnace is stable, and then the hot rolling mill is used for 7 passes. In the first four passes of the first pass rolling, the single pass deformation of the first pass rolling is 20% to 24%, and the single pass of the last three passes is 20% to 24%. The secondary deformation is 8% to 15%;

Step 7. Two-fire rolling: The first-fire rolling slab obtained in step 6 is cut and blanked and heated at 925 ° C for 100 minutes. The holding time is from the first rolling slab into the heating furnace and the heating furnace When the furnace temperature is stable, the calculation is started, and then the hot rolling mill is used for 5 passes of second-fire rolling to obtain a second-fire rolled slab with a thickness of 10 mm; the deformation amount of the first three passes of the second-fire rolling is 20% ~24%, and the deformation amount of the last two passes is 18% to 20%; the second-fire rolling adopts reversing rolling, so that the direction of the second-fire rolling is perpendicular to the direction of the first-fire rolling described in step 6;

Step 8. Slab treatment: The second-fire rolled slab obtained in Step 7 is annealed at a temperature of 860° C. for 1.2 hours, and then ground and sheared in turn to obtain an average grain size of 17 μm and a thickness of 10 mm. TA15 titanium alloy plate.

The TA15 titanium alloy fine-grained medium-thick plate prepared in this example is subjected to a high-temperature tensile test at 880°C under the condition of a strain rate of 1×10 ^-4 /s. The results show that the longitudinal elongation of the TA15 titanium alloy fine-grained medium-thick plate is 435%, and the transverse elongation is 385%, indicating that the TA15 titanium alloy fine-grained medium-thick plate prepared in this example has excellent superplastic properties.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any way. Any simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solutions of the present invention.

Claims (10)

1. a processing method of fine-grained superplastic TA15 titanium alloy medium and thick plate, is characterized in that, this method may further comprise the steps: Step 1. Smelting: According to the design composition of the target alloy, the 0-grade titanium sponge and the intermediate alloy are sequentially mixed, electrode pressed and welded, and then TA15 titanium alloy ingot is obtained by three vacuum consumable arc smelting. Clean up local defects on the surface of alloy ingots; Step 2, billet forging: put the TA15 titanium alloy ingot cleaned in step 1 into an electric furnace for heating and heat preservation under the conditions of T _β +160 ° C ~ T _β + 180 ° C, and then use a rapid forging of more than 2000t The upsetting billet is forged by the machine, and the primary forging billet is obtained after air cooling; the T _β is the β phase transition temperature of the TA15 titanium alloy, the unit is °C, and the aspect ratio used in the upsetting billet forging is (2 ~ 2.5 ):1; Step 3. Upsetting and forging in the β phase region: put the primary forging billet obtained in step 2 into an electric furnace for heating and heat preservation under the condition of T _β +60°C ~ T _β +80°C, and then use a fast forging machine with a capacity of more than 2000t Or a press is used for upsetting and forging in the beta phase region, and the secondary forging blank is obtained after air cooling; the height-diameter ratio used in the upsetting and forging in the beta phase region is (2-2.5): 1; Step 4. Upsetting and forging in the α+β two-phase region: put the secondary forging billet obtained in step 3 into an electric furnace for heating and heat preservation under the condition of T _β -25°C ~ T _β -30°C, and then use more than 2000t The first upsetting forging in the α+β two-phase region is carried out by the fast forging machine or press, and the third-stage forging blank is obtained after cooling, and the third-stage forging blank is continued to be under the condition of T _β -25℃～T _β -30℃ Heating and heat preservation are carried out, and then a fast forging machine or a press of more than 2000t is used for the second upsetting and forging of the α+β two-phase region, and the fourth-stage forging blank is obtained after air cooling; the first upsetting of the α+β two-phase region is performed. The height-diameter ratios used in forging and the second upsetting forging in the α+β two-phase region are both (2-2.5): 1; Step 5. Final forging: put the four-stage forging billet obtained in step 4 into an electric furnace for heating and heat preservation under the condition of T _β -30 ℃～T _β -40 ℃, and then perform upsetting and final forging forging, and after air cooling A forging is obtained; the height-diameter ratio used in the upsetting and final forging is (2-2.5): 1, and the thickness of the forging is 200-220 mm; Step 6. One-fire rolling: heat and keep the forging obtained in step 5, and then use a hot rolling mill to perform one-fire rolling for 6 to 8 passes to obtain a one-fire rolled slab; the one-fire rolling The thickness of the slab is 50mm to 80mm; Step 7, second-fire rolling: the first-fire rolling slab obtained in step 6 is cut and blanked, heated and kept warm, and then 4-6 passes of second-fire rolling are carried out with a hot rolling mill to obtain second-fire rolling. Slab; the thickness of the second-fire rolled slab is 10mm to 25mm; Step 8, slab treatment: annealing the second-fire rolled slab obtained in step 7, and then performing grinding and shearing treatment in turn to obtain a TA15 titanium alloy medium and heavy plate; the thickness of the TA15 titanium alloy medium and heavy plate It is 10mm to 25mm, the average grain size is not more than 20μm, and the transverse elongation of TA15 titanium alloy medium and thick plate at 850 ℃ ~ 930 ℃ temperature is more than 420%, and the longitudinal elongation is more than 340%. 2. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, described in step 1 for the first time and the second vacuum of three vacuum consumable arc smelting During the consumable arc melting process, the vacuum degree in the vacuum consumable arc melting furnace is less than 1.0×10 ^-1 Pa. During the third vacuum consumable arc melting process, the vacuum degree in the vacuum consumable arc melting furnace is less than 1.0×10 -1 Pa. 5.0×10 ⁻² Pa; in step 1, smooth transition grinding is performed on the cleaned TA15 titanium alloy ingot, and the aspect ratio of smooth transition grinding is not greater than 1:10, and the depth is not greater than 10 mm. 3. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, the mode of heating and heat preservation described in step 2 is stepped heating, and the process of described stepped heating It is as follows: control the charging temperature of the TA15 titanium alloy ingot to be 790℃～810℃ and keep it at the charging temperature for t ₁ min, then heat it up to T _β +160 ℃～T _β + 180 ℃ and keep it for t ₂ min, in which , t ₁ =(TA15 titanium alloy ingot diameter/3-10)min～(TA15 titanium alloy ingot diameter/3+10)min, t ₂ =(TA15 titanium alloy ingot diameter/2+30)min～( TA15 titanium alloy ingot diameter/2+40)min, the unit of TA15 titanium alloy ingot diameter is mm; the single-pass deformation of the upsetting billet forging is 25% to 30%, and the single-fire cumulative deformation amount not less than 80%. 4. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, the mode of heating and heat preservation described in step 3 is step heating, and the process of step heating is: First, control the charging temperature of the primary forging billet to be 790℃～810℃ and keep it at the charging temperature for t ₁ min, then heat it up to T _β +60 ℃～T _β +80 ℃ and keep it for t ₂ min, where t ₁ =(Maximum size of section of primary forging blank/3-10)min～(Maximum size of section of primary forging blank/3+10)min, t ₂ =(Maximum size of section of primary forging blank/2+30)min～(Maximum size of section of primary forging blank/2+30)min～(Maximum size of section of primary forging blank/2+30)min The maximum size of the section/2+40)min, the unit of the maximum size of the primary forging billet section is mm; the single-pass deformation of the upsetting and forging in the β-phase region is 25% to 40%, and the single-fire cumulative deformation is not less than 85%; the drawing and forging process of upsetting and drawing forging in the β-phase region adopts the deformation method of diagonal chamfering, and the deformation amount is 35% to 40%. 5. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, described in step 4, the heating and heat preservation of the first upsetting forging of the α+β two-phase region described in the step 4. The process is as follows: control the charging temperature of the secondary forging billet to be 500℃～600℃, and then raise the temperature to _Tβ- 25℃～ _Tβ- 30℃ at a rate of 3℃/min～5℃/min and keep the temperature for t ₁ min ; the t ₁ =(maximum dimension of the section of the secondary forging billet/2+30)min～(maximum dimension of the section of the secondary forging billet/2+40)min, the unit of the maximum dimension of the section of the secondary forging billet is mm; the The single-pass deformation of the first upsetting and forging of the α+β two-phase region is 25% to 40%, and the cumulative deformation amount of a single fire is not less than 85%; the first upsetting and forging of the α+β two-phase region The subsequent cooling method is water cooling. 6. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, described in step 4, the heating and heat preservation of the second upsetting forging of the α+β two-phase region described in the step 4. The process is: control the charging temperature of the third-stage forging billet to be 450℃～600℃, and then raise the temperature to _Tβ- 30℃～ _Tβ- 40℃ at a rate of 3℃/min～5℃/min and keep the temperature for t ₂ min ; the t ₂ =(maximum size of the section of the third-level forging billet/2+30)min～(maximum size of the section of the third-level forging billet/2+40)min, the unit of the maximum size of the section of the third-level forging billet is mm; the The single-pass deformation of the second upsetting and forging in the α+β two-phase region is 30% to 40%, and the single-fire cumulative deformation is not less than 85%. 7. the processing method of a kind of fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1, is characterized in that, the concrete process of heating and heat preservation described in the step 5 is: control the charging temperature of the four-stage forging billet temperature is 450℃～600℃, then the temperature is raised to _Tβ- 30℃～ _Tβ- 40℃ at a rate of 3℃/min～5℃/min and kept for t ₀ min; the t ₀ =(four-stage forging blank section Maximum size/2+30)min～(Maximum size of the section of the fourth-stage forging billet/2+40)min, the unit of the maximum size of the section of the fourth-stage forging billet is mm; the single-pass deformation of the upsetting final forging is: 30% to 40%, and the cumulative deformation of a single fire is not less than 85%. 8 . The method for processing a fine-grained superplastic TA15 titanium alloy medium and thick plate according to claim 1 , wherein the heating temperature of the one-fire rolling described in the step 6 is T _β -40° C.～T _β -50℃, holding time t ₁ =(forging thickness/0.8-5)min～(forging thickness/0.8+5)min, holding time is calculated from the time the fourth-grade forging enters the heating furnace and the furnace temperature of the heating furnace is stable; The single-pass deformation of the first to third passes in the one-fire rolling process is 20% to 25%, and the remaining single-pass deformation is not less than 8%. 9 . The method for processing a fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1 , wherein the heating temperature of the second-fire rolling described in step 7 is T _β -50° C.～T _β -60°C, holding time t ₂ =(the thickness of the slab rolled once/0.5-5)min～(the thickness of the slab rolled once/0.5+5)min, the holding time is from the time the slab enters the heating furnace and the The calculation starts when the furnace temperature of the heating furnace is stable; the initial single-pass deformation of the second-fire rolling is 20% to 26%, and the remaining single-pass deformation is 12% to 20%. The direction of the second fire rolling is perpendicular to the direction of the first fire rolling described in step 6. 10 . The method for processing a fine-grained superplastic TA15 titanium alloy medium-thick plate according to claim 1 , wherein the temperature of the annealing treatment in step 8 is 850° C. to 900° C. and the time is 1 h to 1.5° C. 11 . h.

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