Preparation method of TA15 titanium alloy large forge piece

Abstract

The invention discloses a method for preparing a TA15 titanium alloy large forge piece, which comprises the following steps of: smelting to produce a TA15 titanium alloy cast ingot, heating the cast ingot to be above a phase transformation point, keeping the temperature for a certain time, performing cogging forging, heating a forging stock to be above the phase transformation point, keeping the temperature, and preparing a TA15 titanium alloy bar blank by adopting a multi-heating-number severe plastic deformation forging process; and finally, the bar blank is heated to the two-phase region temperature, heat preservation is conducted, then forging forming is conducted, the TA15 titanium alloy forging is obtained, and the boundary dimension, the comprehensive performance and the flaw detection level of the produced TA15 titanium alloy forging can meet the user requirements.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy preparation, and in particular to a method for preparing a TA15 titanium alloy large forging. Background Art

[0002] The nominal composition (mass fraction, %) of TA15 titanium alloy is Ti-6.5Al-2Zr-1Mo-1V, the Russian grade is BT20, and the phase transition point is 980~1010℃. Its main strengthening mechanism is to improve the process performance by solid solution strengthening of α-stabilizing element Al, adding neutral element Zr and β-stabilizing elements Mo and V. The Al equivalent of this alloy is 6.58%, and the Mo equivalent is 2.46%. It belongs to a near-α-type titanium alloy with high Al equivalent. It has both the good thermal strength and weldability of α-type titanium alloy and the good process plasticity of α+β-type titanium alloy. TA15 titanium alloy has good comprehensive mechanical properties and process performance. Its working life can reach 3000 hours at 500℃ and 6000 hours at 450℃. It is suitable for manufacturing structural parts, welded load-bearing structural parts and some important structural parts with high temperature and complex stress under the condition of 500℃ and below for long-term use. For example, it is used in various blades and casings of engines, various sheet metal parts, joints, large wall panels, welded load-bearing frames of aircraft, etc. It has wide applications in both military and civilian fields.

[0003] Since TA15 titanium alloy contains four alloying elements, namely Al, Zr, Mo, and V, the risk of uneven composition increases when large ingots are used for forgings. Therefore, when preparing large-sized ingots, high requirements are placed on the uniformity of the ingots. In addition, large-sized rectangular forgings are difficult to process in the later stage of forging due to their large width and small thickness. As the specifications of titanium alloy forgings increase, the attenuation of ultrasonic waves in the forgings increases. Therefore, the uniformity of flaw detection of TA15 titanium alloy forgings is also difficult to guarantee. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a TA15 titanium alloy large forging. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0005] A method for preparing a TA15 titanium alloy large forging, comprising:

[0006] Step 1: melt the master alloy package and sponge titanium in a vacuum consumable arc furnace by vacuum induction melting process to obtain a TA15 titanium alloy ingot; the diameter of the TA15 titanium alloy ingot is ≥900 mm and the weight is ≥6 tons;

[0007] Step 2: Heat the TA15 titanium alloy ingot to 1130 - 1200 °C, hold for 180 - 690 min, and then perform cogging forging above the phase transformation point to obtain a TA15 titanium alloy cylindrical forging blank with a diameter of 600 - 750 mm;

[0008] Step 3: Heat the TA15 alloy cylindrical forging blank to T β +(0 - 200) °C, hold for 200 - 550 min, and then use a multi - pass severe plastic deformation forging process to prepare a TA15 titanium alloy bar blank with a diameter of 600 - 750 mm;

[0009] Step 4: Heat the TA15 titanium alloy bar blank to T β -(0 - 100) °C, hold for 300 - 600 min, and then perform forging to form a TA15 titanium alloy forging; among them, the thickness of the TA15 titanium alloy forging is 105 - 360 mm, and the width is 500 - 1100 mm.

[0010] Furthermore, in Step 1, the melting current of the vacuum induction melting is 15 - 25 kA, the melting voltage is 25 - 45 V, and the melting vacuum degree ≤ 7 Pa.

[0011] Furthermore, the forging ratio of the cogging forging is 1.0 - 4.0, the deformation speed < 90 mm / s, and the final forging temperature ≥ 900 °C.

[0012] Furthermore, in Step 3, the multi - pass severe plastic deformation forging process is multi - pass upsetting → transverse drawing out → rolling round; among them, the forging ratio of each pass except the last pass is 1.5 - 4, the deformation speed ≤ 70 mm / s, the forging ratio of the last pass is 1.5 - 3.5, the deformation speed < 40 mm / s, and the final forging temperature ≥ 800 °C.

[0013] Furthermore, in Step 4, the forging ratio of each pass during the forging process is 1.0 - 2.5, the deformation speed ≤ 40 mm / s; the final forging temperature ≥ 800 °C.

[0014] Advantages of the present invention:

[0015] By designing a reasonable process route, the key technology for preparing large TA15 titanium alloy forgings is finally broken through, and the external dimensions, comprehensive performance, and flaw detection level of the prepared large TA15 titanium alloy forgings can all meet the user's requirements.

[0016] The following will further elaborate on the present invention in conjunction with the drawings and embodiments. Description of the Drawings

[0017] Figures 1 to 2Microstructure of the TA15 titanium alloy forging prepared in Example 1 of the present invention;

[0018] Figures 3 to 6 Mechanical property test report of the TA15 titanium alloy forging in Example 1 of the present invention;

[0019] Figure 7 Ultrasonic flaw detection result of the TA15 titanium alloy forging prepared in Example 1 of the present invention;

[0020] Figure 8 Microstructure of the TA15 titanium alloy forging prepared in Example 2 of the present invention;

[0021] Figure 9 Microstructure of the TA15 titanium alloy forging prepared in Example 3 of the present invention. Detailed implementation manners

[0022] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0023] Example 1

[0024] The present invention provides a method for preparing a TA15 titanium alloy large forging with a width of 1100 mm and a thickness of 120 mm. The method specifically includes the following steps:

[0025] Step 1: Use a special master alloy ladle, select sponge titanium with good grade and particle size matching the master alloy, and prepare a TA15 titanium alloy electrode with uniform composition by using a mixing and batching production line and an oil press. Then, perform vacuum induction melting using a vacuum consumable arc furnace, and melt twice in total to obtain a TA15 titanium alloy ingot with a diameter of 960 mm and a weight of 6.2 tons. The titanium alloy ingot is composed of the following components in mass percentage: Al 5.50% - 7.10%, Mo 0.50% - 2.00%, V 0.80% - 2.50%, Zr 1.50% - 2.50%, C ≤ 0.10%, Fe ≤ 0.25%, Si ≤ 0.05%, N ≤ 0.05%, O ≤ 0.15%, and the rest is Ti.

[0026] Specifically, the master alloy ladle is composed of Al-V alloy, Al-Mo alloy and sponge zirconium; the melting current of the vacuum induction melting is 20 kA, the melting voltage is 30 V, and the melting vacuum degree is 7 Pa.

[0027] Specifically, the scale on the surface of the TA15 titanium alloy ingot is machined off, and an antioxidant coating with a thickness of 0.5 mm is applied to the surface of the machined TA15 titanium alloy ingot. The antioxidant coating is TB1200-16.

[0028] Step 2: Heat the TA15 titanium alloy ingot in a natural gas furnace to 1150 - 1170 °C, hold for 540 min, then take it out of the furnace. Perform cogging forging on the TA15 titanium alloy ingot above its β-phase transformation point to obtain a TA15 titanium alloy cylindrical forging blank with a diameter of 730 mm. Specifically, the forging ratio of the cogging forging is 1.0 - 2.5, the deformation speed is 60 mm / s, and the final forging temperature is ≥900 °C.

[0029] Specifically, the specific heating process of the cogging forging is to first heat the TA15 titanium alloy ingot to 800 - 850 °C, hold for 210 min, then heat it up to 1150 - 1170 °C again, and hold for 540 min before performing cogging forging.

[0030] Step 3: Heat the TA15 titanium alloy cylindrical forging blank in an electric resistance furnace to 1050 - 1100 °C, hold for 240 min, and then use the multi-pass large plastic deformation forging process to perform the intermediate forging process to prepare a TA15 titanium alloy bar blank with a diameter of 730 mm.

[0031] Specifically, perform multi-pass upsetting → transverse drawing out → rolling round on the heated and held TA15 titanium alloy cylindrical forging blank on a free forging press. Among them, the forging ratio of each pass except the last pass is 1.5 - 4, the deformation speed is 20 - 50 mm / s. When performing the last pass of forging, the forging ratio is 1.5 - 3.5, the deformation speed is 10 - 30 mm / s, and the final forging temperature is ≥800 °C. Finally, a TA15 titanium alloy bar blank with a diameter of 730 mm is obtained.

[0032] Step 4: Heat the TA15 titanium alloy bar blank to 930 - 960 °C, hold for 400 min, and then perform forging to form the forging. Specifically, adopt the transverse width spreading + longitudinal forming method to ensure that the width of the forging reaches the required size, so as to obtain a TA15 titanium alloy forging with a thickness of 120 mm and a width of 1100 mm. The forging ratio of each pass in the entire forging process is 1.0 - 2.5, the deformation speed is 20 - 35 mm / s, and the final forging temperature is ≥800 °C.

[0033] By combining the plasticity and deformation resistance of the TA15 titanium alloy, reasonably design the finished forging deformation amount, and ensure that there is no abnormality in the surface quality of the blank while ensuring the forging penetration effect of the blank.

[0034] Since the TA15 titanium alloy has relatively high strength and deformation resistance during forging and will produce a certain degree of strain hardening, it is necessary to reasonably control the forging temperature and deformation amount, reasonably set the forging process, and adopt the upsetting + transverse drawing out process to fully ensure the sufficiency and uniformity of the overall deformation of the forging blank during blank making, so as to ensure the uniformity of the later entire forging blank structure and flaw detection performance.

[0035] In addition, due to the strong strain rate sensitivity of TA15 titanium alloy, with the increase of the strain rate, the plasticity of the titanium alloy decreases, and the deformation resistance increases. In the case of high strain rates, it is also necessary to consider the temperature rise of the billet caused by deformation heat to avoid overheating of the microstructure due to local temperature rise and form coarse Widmanstätten structure. Therefore, during the entire forging process, the pressing speed is strictly controlled, that is, the deformation speed during forging in the single-phase region is not greater than 70 mm / s; during forging in the two-phase region, the deformation speed is not greater than 40 mm / s.

[0036] The TA15 titanium alloy forgings obtained in Example 1 were subjected to microstructural analysis and mechanical property analysis. The results of the scanning electron microscope are as Figure 1 and Figure 2 shown. It can be seen that the microstructure of the forgings is a two-phase region processed structure with good spheroidization; the mechanical properties are as Figures 3 to 6 shown. The results show that the room temperature tensile, impact work, plane fracture toughness, high temperature tensile and creep properties of the TA15 titanium alloy forgings all meet the requirements of the technical standards; the flaw detection results of the forgings are as Figure 7 shown. The flaw detection results show that the microstructure of the forgings is relatively uniform and can meet the user's usage requirements.

[0037] Example 2

[0038] The embodiment of the present invention provides a method for preparing a TA15 titanium alloy large forging with a width of 500 mm and a thickness of 360 mm. The method specifically includes the following steps:

[0039] Step 1: Use a special master alloy ladle, select sponge titanium with better grade and particle size matching the master alloy, and prepare a TA15 titanium alloy electrode with uniform composition using a mixing and batching production line and an oil press. Then, use a vacuum consumable arc furnace for vacuum induction melting, and melt twice in total to obtain a TA15 titanium alloy ingot with a diameter of 920 mm and a weight of 6.35 tons. The titanium alloy ingot is composed of the following components by mass percentage: Al 5.50% - 7.10%, Mo 0.50% - 2.00%, V 0.80% - 2.50%, Zr 1.50% - 2.50%, C ≤ 0.10%, Fe ≤ 0.25%, Si ≤ 0.05%, N ≤ 0.05%, O ≤ 0.15%, and the rest is Ti.

[0040] Specifically, the master alloy ladle is composed of Al-V alloy, Al-Mo alloy and sponge zirconium; the melting current of the vacuum induction melting is 25 kA, the melting voltage is 45 V, and the melting vacuum degree is 7 Pa.

[0041] Specifically, the scale on the surface of the TA15 titanium alloy ingot is machined off, and an antioxidant coating with a thickness of 0.6 mm is applied to the surface of the machined TA15 titanium alloy ingot. The antioxidant coating is TB1200-16.

[0042] Step 2: Heat the TA15 titanium alloy ingot in a natural gas furnace to 1120-1160 °C, keep it warm for 480 min, and then perform cogging forging above the β phase transformation point to obtain a TA15 titanium alloy cylindrical forging blank with a diameter of 700 mm. Specifically, the forging ratio of the cogging forging is 1.3-4.0, the deformation speed is 80 mm / s, and the final forging temperature is ≥900 °C.

[0043] Specifically, the specific heating process of the cogging forging is to first heat the TA15 titanium alloy ingot to 800-850 °C, keep it warm for 180 min, then raise the temperature to 1120-1160 °C again, and keep it warm for 480 min for cogging forging.

[0044] Step 3: Heat the TA15 titanium alloy cylindrical forging blank in an electric resistance furnace to 1020-1080 °C, keep it warm for 315 min, and then adopt a multi-pass large plastic deformation forging process to carry out the intermediate forging process to prepare a TA15 titanium alloy bar blank with a diameter of 700 mm.

[0045] Specifically, the heated and insulated TA15 titanium alloy cylindrical forging blank is subjected to multi-pass upsetting → transverse drawing → rounding on a free forging press. Among them, the forging ratio of each pass except the last pass is 1.5-4, the deformation speed is 30-55 mm / s, and in the last pass of forging, the forging ratio is 1.5-2, the deformation speed is 20-35 mm / s, and the final forging temperature is ≥800 °C. Finally, a TA15 titanium alloy bar blank with a diameter of 700 mm is obtained.

[0046] Step 4: Heat the TA15 titanium alloy bar blank to 920-985 °C, keep it warm for 550 min, and then perform forging forming. Specifically, the transverse spreading + longitudinal forming method is adopted to ensure the spreading of the forging to the size, so as to obtain a TA15 titanium alloy forging with a thickness of 360 mm and a width of 500 mm; the forging ratio of each pass in the whole forging process is 1.0-2.5, the deformation speed is 30-40 mm / s, and the final forging temperature is ≥800 °C. Figure 8 The microstructural morphology shown in Fig. 5 is the microstructure of the forging obtained in Example 2, which is a two-phase region processing microstructure with good spheroidization and meets the requirements of relevant technical conditions.

[0047] Example 3

[0048] The embodiment of the present invention provides a method for preparing a large TA15 titanium alloy forging with a width of 780 mm and a thickness of 105 mm. The method specifically includes the following steps:

[0049] Step 1: Use a special master alloy ladle, select sponge titanium with better grade and particle size matching the master alloy, and prepare a TA15 titanium alloy electrode with uniform composition by using a mixing and feeding production line and a hydraulic press. Then, perform vacuum induction melting using a vacuum consumable arc furnace, with a total of two melts, to obtain a TA15 titanium alloy ingot with a diameter of 920 mm and a weight of 6.4 tons. The TA15 titanium alloy ingot is composed of the following components by mass percentage: Al 5.50% - 7.10%, Mo 0.50% - 2.00%, V 0.80% - 2.50%, Zr 1.50% - 2.50%, C ≤ 0.10%, Fe ≤ 0.25%, Si ≤ 0.05%, N ≤ 0.05%, O ≤ 0.15%, and the rest is Ti.

[0050] Specifically, the master alloy ladle is composed of Al-V alloy, Al-Mo alloy, and sponge zirconium; the melting current for vacuum induction melting is 15 kA, the melting voltage is 25 V, and the melting vacuum degree is 7 Pa.

[0051] Specifically, machine-process the oxide scale on the surface of the TA15 titanium alloy ingot, and apply an antioxidant coating with a thickness of 0.4 mm on the surface of the machined TA15 titanium alloy ingot. The antioxidant coating is TB1200-16.

[0052] Step 2: Heat the TA15 titanium alloy ingot in a natural gas furnace to 1130 - 1150 °C, and after holding for 195 min, perform cogging forging above the β phase transformation point to obtain a TA15 titanium alloy cylindrical forged blank with a diameter of 730 mm; specifically, the forging ratio of the cogging forging is 1.0 - 2.0, the deformation speed is 45 mm / s, and the final forging temperature ≥ 900 °C.

[0053] Specifically, the specific heating process of the cogging forging is to first heat the TA15 titanium alloy ingot to 800 - 850 °C, hold for 180 min, then raise the temperature to 1130 - 1150 °C again, and hold for 195 min for cogging forging.

[0054] Step 3: Heat the TA15 titanium alloy cylindrical forged blank in a resistance furnace to 1000 - 1080 °C, and after holding for 400 min, use a multi-pass large plastic deformation forging process to perform an intermediate forging process to prepare a TA15 titanium alloy bar blank with a diameter of 730 mm.

[0055] Specifically, the heated and heat-insulated TA15 titanium alloy cylindrical forging billet is subjected to multi-pass upsetting → transverse drawing out → rolling round on a free forging press. Among them, the forging ratio for each pass except the last pass is 1.5 - 3, and the deformation speed is 20 - 40 mm / s. When forging in the last pass, the forging ratio is 1.5 - 2, and the deformation speed is 10 - 20 mm / s. The finish forging temperature is ≥800 °C, and finally a TA15 titanium alloy bar billet with a diameter of 730 mm is obtained.

[0056] Step 4: Heat the TA15 titanium alloy bar billet to 900 - 970 °C, and after heat insulation for 320 min, perform forging forming. Specifically, adopt the transverse spreading + longitudinal forming method to ensure that the spreading of the forging reaches the dimensions, thereby obtaining a TA15 titanium alloy forging with a thickness of 105 mm and a width of 780 mm; the forging ratio for each pass in the entire forging process is 1.0 - 2.5, the deformation speed is 10 - 25 mm / s, and the finish forging temperature is ≥800 °C. Figure 9 It is the microstructure of the forging obtained in Example 3, which is a two-phase region processing microstructure with good spheroidization and meets the requirements of relevant technical conditions.

[0057] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a TA15 titanium alloy large forging, characterized in that: include: Step 1: melt the master alloy package and sponge titanium in a vacuum consumable arc furnace by vacuum induction melting process to obtain a TA15 titanium alloy ingot; the diameter of the TA15 titanium alloy ingot is ≥900 mm and the weight is ≥6 tons; Step 2: heating the TA15 titanium alloy ingot to 1130-1200° C. and keeping the temperature for 180-690 min, then forging the ingot above the phase transition point to obtain a TA15 titanium alloy cylindrical forging blank, wherein the diameter of the TA15 titanium alloy cylindrical forging blank is 600-750 mm; Step 3: Heat the TA15 alloy cylindrical forging billet to T β +(0-200)°C, and keep warm for 200-550min, and then adopt a multi-fire large plastic deformation forging process to prepare a TA15 titanium alloy billet, wherein the diameter of the TA15 titanium alloy billet is 600-750mm; Step 4: Heat the TA15 titanium alloy billet to T β -(0-100)°C and keep warm for 300-600min, then forging is performed to obtain TA15 titanium alloy forgings; wherein the TA15 titanium alloy forgings have a thickness of 105-360mm and a width of 500-1100mm.

2. The method for preparing a TA15 titanium alloy large forging according to claim 1, characterized in that: In the step 1, the melting current of the vacuum induction melting is 15-25 kA, the melting voltage is 25-45 V, and the melting vacuum is ≤7 Pa.

3. The method for preparing a TA15 titanium alloy large forging according to claim 1, characterized in that: The forging ratio of the blank forging is 1.0-4.0, the deformation speed is less than 90 mm / s, and the final forging temperature is greater than or equal to 900°C.

4. The method for preparing a TA15 titanium alloy large forging according to claim 1, characterized in that: In step 3, the multi-fire large plastic deformation forging process is multi-fire upsetting → transverse drawing → rounding; wherein, except for the last fire, the forging ratio of each fire is 1.5-4, the deformation speed is ≤70mm / s, the forging ratio of the last fire is 1.5-3.5, the deformation speed is <40mm / s, and the final forging temperature is ≥800°C.

5. The method for preparing a TA15 titanium alloy large forging according to claim 1, characterized in that: In the step 4, the forging ratio of each fire in the forging process is 1.0-2.5, the deformation speed is ≤40mm / s; and the final forging temperature is ≥800°C.

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