Preparation method of large-sized titanium alloy special-shaped forging

Abstract

The present invention discloses a preparation method for large-sized titanium alloy special-shaped forgings, comprising: performing vacuum induction melting by using a vacuum consumable arc furnace to obtain a titanium alloy ingot; after heating and holding the titanium alloy ingot, performing cogging forging on it above the phase transformation point to obtain a titanium alloy forging blank; after heating the titanium alloy forging blank, adopting a multi-pass plastic deformation process to obtain a titanium alloy intermediate bar blank; determining the bar blank cutting size according to the size of the die forging blank, and then forging the cut titanium alloy intermediate bar blank into a die forging blank by free forging; coating the surface of the die forging blank and the inner surface of the die forging mold, and then performing die forging on the die forging blank by using a large-tonnage free forging equipment to obtain a semi-finished titanium alloy special-shaped forging; performing heat treatment on the semi-finished titanium alloy special-shaped forging to obtain a large-sized titanium alloy special-shaped forging; this method improves the controllability of the forgings to meet the requirements of shape and size, performance, and uniform and reliable flaw detection.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of non-ferrous metal products, and particularly relates to a method for preparing large-sized titanium alloy special-shaped forgings. Background Art

[0002] With the rapid development of China's aerospace industry, new aerospace models have emerged continuously. Lightweight is an important development direction of new aerospace models. Reducing 1 kg in weight on aerospace equipment can bring huge economic and social benefits. "Replacing heavy materials with light ones" is one of the important ways to achieve weight reduction. Replacing high-strength steel with titanium alloy to manufacture load-bearing structural parts can achieve a weight reduction of more than 20% for aircraft, and titanium alloy has become an important material applied in the aerospace field. Moreover, some titanium alloys, due to their high strength, high toughness, good plasticity and welding performance, are widely used in the fields of aviation, aerospace, ordnance, petroleum, etc. And because they also have the advantage of high hardenability, they can be used to produce large-section structural parts with high load-bearing capacity. However, there is currently no perfect and reasonable preparation process to prepare large-sized and large-section high-strength and high-toughness titanium alloy forgings. Summary of the Invention

[0003] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing large-sized titanium alloy special-shaped forgings. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0004] A method for preparing large-sized titanium alloy special-shaped forgings, comprising:

[0005] Step 1: Using a vacuum consumable arc furnace for vacuum induction melting to obtain a titanium alloy ingot, and the diameter of the titanium alloy ingot ≥ 800 mm and the weight ≥ 6 tons;

[0006] Step 2: After heating and insulating the titanium alloy ingot, performing cogging forging on it above the phase transformation point to obtain a titanium alloy forging blank;

[0007] Step 3: After heating the titanium alloy forging blank, adopting a multi-pass plastic deformation process to obtain a titanium alloy intermediate bar blank, and the diameter of the titanium alloy intermediate bar blank ≥ 600 mm;

[0008] Step 4: Determining the bar blank cutting size according to the size of the die forging blank, and then forging the cut titanium alloy intermediate bar blank into a die forging blank by open die forging;

[0009] Step 5: Coating the surface of the die forging blank and the inner surface of the die forging mold, and then performing die forging on the die forging blank by using a large-tonnage open die forging equipment to obtain a semi-finished titanium alloy special-shaped forging;

[0010] Step 6: Heat-treat the semi-finished titanium alloy special-shaped forging to obtain the large-sized titanium alloy special-shaped forging, where the single weight of the titanium alloy special-shaped forging is ≥600 Kg, the projected area is ≥1.4 m², and the maximum width is ≥1350 mm; the titanium alloy special-shaped forging includes the following chemical components by weight percentage: Al: 4.5% - 5.7%, Mo: 4.0% - 5.5%, V: 4.0% - 5.5%, Cr: 0.5% - 1.5%, Fe: 0.5% - 1.5%, C ≤ 0.08%, Zr ≤ 0.30%, Si ≤ 0.15%, O ≤ 0.18%, N ≤ 0.05%, H ≤ 0.15%.

[0011] Further, in the said Step 1, the melting current of the vacuum induction melting is 22 - 28 kA, the melting voltage is 30 - 40 V, and the vacuum degree of the melting chamber is ≤5 Pa.

[0012] Further, in the said Step 2, the heating temperature is 1100 - 1200 °C, the heat preservation time is 300 - 500 min, the deformation amount is 40 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0013] Further, in the said Step 3, heat the titanium alloy forging blank to the temperature of (β - 100) - 1100 °C and keep it warm for 400 - 700 min, and then perform multi-pass intermediate forging to obtain the titanium alloy intermediate bar blank; wherein, the deformation amount is 20 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0014] Further, in the said Step 4, the heating temperature during open die forging is β - (0 - 100) °C, the heat preservation time is 400 - 700 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0015] Further, in the said Step 5, the heating temperature during impression die forging is β - (0 - 100) °C, the heat preservation time is 400 - 700 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0016] Further, in the said Step 5, the coating applied on the surface of the impression die forging blank is TB1200 - 16, and the coating applied on the inner surface of the impression die forging die is molybdenum disulfide coating.

[0017] Further, the heat treatment in step 6 refers to: heating the semi-finished titanium alloy special-shaped forging to 800-900 °C, holding for 2-3 h, then cooling in the furnace to 700-750 °C, holding for 2-3 h, and then air-cooling to room temperature; then heating the semi-finished titanium alloy special-shaped forging to 600-650 °C, holding for 6-8 h, and then air-cooling to room temperature.

[0018] Advantages of the present invention:

[0019] The preparation method adopted by the present invention reduces the processing and later maintenance difficulties of the mold, shortens the production cycle of the forging, improves the controllability of the forging's shape and size compliance with requirements, performance, and uniform and reliable flaw detection, and this forging is the largest cross-section high-strength and high-toughness titanium alloy forging applied in the domestic aerospace field so far, and its super-large specification forging meets the titanium demand for China's heavy rockets.

[0020] The following will further elaborate on the present invention in detail with reference to the drawings and embodiments. Description of the Drawings

[0021] Figure 1 Metallographic diagram of the titanium alloy special-shaped forging prepared in Example 1;

[0022] Figure 2 Metallographic diagram of the titanium alloy special-shaped forging prepared in Example 2;

[0023] Figure 3 Metallographic diagram of the titanium alloy special-shaped forging prepared in Example 3;

[0024] Figures 4 to 7 Mechanical property test results of the titanium alloy special-shaped forging prepared in Example 1;

[0025] Figures 8 to 12 Mechanical property test results of the titanium alloy special-shaped forging prepared in Example 2;

[0026] Figures 13 to 16 Mechanical property test results of the titanium alloy special-shaped forging prepared in Example 3. Specific Embodiments

[0027] The following further describes the present invention in detail with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0028] Example 1

[0029] The embodiment of the present invention provides a preparation method for a large-specification titanium alloy special-shaped forging, and this method includes the following steps:

[0030] Step 1: Vacuum induction melting is carried out using a vacuum consumable arc furnace to obtain a titanium alloy ingot with a diameter of 810 mm and a weight of 6.1 tons. Among them, the melting current of the vacuum induction melting is 22 - 28 kA, the melting voltage is 30 - 40 V, and the melting vacuum degree ≤ 5 Pa.

[0031] Step 2: Heat and hold the titanium alloy ingot, and perform cogging forging above the phase transformation point to obtain a titanium alloy forging blank. Specifically, the heating temperature is 1100 - 1150 °C, the holding time is 400 - 500 min, the deformation amount is 40 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0032] Step 3: Then, after heating the titanium alloy forging blank, a multi-pass plastic deformation process is adopted to obtain a titanium alloy intermediate bar blank with a diameter of 600 mm. Specifically, heat the titanium alloy forging blank to a temperature of (β - 100) - 1100 °C and hold for 400 - 700 min, and then perform multi-pass intermediate forging to obtain the titanium alloy intermediate bar blank. Among them, the deformation amount is 20 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0033] This process strictly controls the heating temperature and holding time, controls the forging deformation amount and the final forging temperature, ensures that the obtained structure is a two-phase zone processing structure, achieves an excellent match of strength - plasticity - toughness, and ensures that the ultrasonic flaw detection level and performance detection results of the bar blank meet the technical condition requirements.

[0034] Step 4: Machine process the titanium alloy intermediate bar blank produced in Step 3, and perform ultrasonic flaw detection and physical and chemical property detection. After the detection results meet the standards, determine the bar blank cutting size according to the size of the die forging blank, and then forge the cut titanium alloy intermediate bar blank into a die forging blank by open die forging. Specifically, the heating temperature during open die forging is β - (0 - 40) °C, the holding time is 400 - 500 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0035] Step 5: Coat the surface of the die forging blank and the inner surface of the die forging mold, and then perform die forging on the die forging blank using a large-tonnage open die forging equipment to obtain a semi-finished titanium alloy special-shaped forging. Specifically, the coating applied to the surface of the die forging blank is a lubricating and heat-insulating coating, the coating is TB1200 - 16, and the coating applied to the inner surface of the die forging mold is a molybdenum disulfide coating, so as to ensure the final forging temperature, reduce surface cracks of the forging, and at the same time reduce the surface friction during the deformation process of the forging blank in the mold, ensuring the smooth forming of the blank.

[0036] Specifically, the heating temperature during die forging is β - (0 to 40) °C, the holding time is 400 to 500 min; the deformation amount is 20% to 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0037] Step 6: Heat-treat the semi-finished titanium alloy special-shaped forging to obtain the large-sized titanium alloy special-shaped forging. Specifically, heat the semi-finished titanium alloy special-shaped forging to 800 to 850 °C and hold for 2.7 to 3 h, then cool it in the furnace to 700 to 730 °C and hold for 2.7 to 3 h, and then air-cool it to room temperature; then heat the semi-finished titanium alloy special-shaped forging to 600 to 620 °C and hold for 7.5 to 8 h, and then air-cool it to room temperature. Finally, a titanium alloy special-shaped forging with a single weight ≥ 600 Kg, a projected area ≥ 1.4 m², and a maximum width ≥ 1350 mm is obtained. The titanium alloy special-shaped forging includes the following chemical components by weight percentage: Al: 4.5% to 5.7%, Mo: 4.0% to 5.5%, V: 4.0% to 5.5%, Cr: 0.5% to 1.5%, Fe: 0.5% to 1.5%, C ≤ 0.08%, Zr ≤ 0.30%, Si ≤ 0.15%, O ≤ 0.18%, N ≤ 0.05%, H ≤ 0.15%.

[0038] Example 2

[0039] The embodiment of the present invention provides a method for preparing a large-sized titanium alloy special-shaped forging, and the method includes the following steps:

[0040] Step 1: Use a vacuum consumable arc furnace for vacuum induction melting to obtain a titanium alloy ingot with a diameter of 800 mm and a weight of 6.3 tons; wherein, the melting current for vacuum induction melting is 22 to 28 kA, the melting voltage is 30 to 40 V, and the melting vacuum degree ≤ 5 Pa.

[0041] Step 2: Heat and hold the titanium alloy ingot, and perform cogging forging on it above the phase transition point to obtain a titanium alloy forging blank; specifically, the heating temperature is 1120 to 1170 °C, the holding time is 350 to 450 min, the deformation amount is 40 to 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0042] Step 3: Then heat the titanium alloy forging blank and adopt a multi-pass plastic deformation process to obtain a titanium alloy intermediate bar blank with a diameter of 600 mm; specifically, heat the titanium alloy forging blank to a temperature of (β - 100) to 1100 °C and hold for 400 to 700 min, and then perform multi-pass intermediate forging to obtain the titanium alloy intermediate bar blank; wherein, the deformation amount is 20 to 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0043] Step 4: The titanium alloy intermediate billet produced in Step 3 is machined, and ultrasonic flaw detection and physical and chemical property tests are carried out. After the test results meet the standards, the billet cutting size is determined according to the size of the die forging blank, and then the titanium alloy intermediate billet after cutting is forged into a die forging blank by open die forging. Specifically, when performing open die forging, the heating temperature is β-(40-80)°C, the heat preservation time is 500-600 min, the deformation amount is 20%-80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600°C.

[0044] Step 5: Coatings are applied to the surface of the die forging blank and the inner surface of the die forging mold, and then the die forging blank is subjected to die forging using a large-tonnage open die forging equipment to obtain a semi-finished titanium alloy special-shaped forging; specifically, the coating applied to the surface of the die forging blank is a lubricating heat preservation coating, and the coating is TB1200-16. The coating applied to the inner surface of the die forging mold is a molybdenum disulfide coating, so as to ensure the final forging temperature, reduce surface cracks of the forging, and at the same time reduce the surface friction during the deformation process of the forging blank in the mold, ensuring the smooth forming of the blank.

[0045] Specifically, when performing die forging, the heating temperature is β-(40-80)°C, the heat preservation time is 500-600 min; the deformation amount is 20%-80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600°C.

[0046] Step 6: The semi-finished titanium alloy special-shaped forging is heat-treated to obtain the large-size titanium alloy special-shaped forging. Specifically, the semi-finished titanium alloy special-shaped forging is heated to 830-870°C and heat-preserved for 2.4-2.7 h, then cooled in the furnace to 720-740°C and heat-preserved for 2.4-2.7 h, and then air-cooled to room temperature; then the semi-finished titanium alloy special-shaped forging is heated to 620-640°C and heat-preserved for 6.5-7.5 h, and then air-cooled to room temperature. Finally, a titanium alloy special-shaped forging with a single weight ≥600 Kg, a projected area ≥1.4 m², and a maximum width ≥1350 mm is obtained. The titanium alloy special-shaped forging includes the following chemical components by weight percentage: Al: 4.5%-5.7%, Mo: 4.0%-5.5%, V: 4.0%-5.5%, Cr: 0.5%-1.5%, Fe: 0.5%-1.5%, C≤0.08%, Zr≤0.30%, Si≤0.15%, O≤0.18%, N≤0.05%, H≤0.15%.

[0047] Example 3

[0048] An embodiment of the present invention provides a method for preparing a large-size titanium alloy special-shaped forging, and the method includes the following steps:

[0049] Step 1: Use a vacuum consumable arc furnace for vacuum induction melting to obtain a titanium alloy ingot with a diameter of 800 mm and a weight of 6 tons. Among them, the melting current of the vacuum induction melting is 22 - 28 kA, the melting voltage is 30 - 40 V, and the melting vacuum degree ≤ 5 Pa.

[0050] Step 2: Heat and hold the titanium alloy ingot, then take it out of the furnace, and then perform cogging forging to obtain a titanium alloy forging blank. Specifically, the heating temperature for cogging forging is 1150 - 1200 °C, the holding time is 300 - 350 min, the deformation amount is 40 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0051] Step 3: Then, after heating the titanium alloy forging blank, adopt a multi-pass plastic deformation process to obtain a titanium alloy intermediate bar blank with a diameter of 600 mm. Specifically, heat the titanium alloy forging blank to a temperature of (β - 100) - 1100 °C and hold it for 400 - 700 min, and then perform multi-pass intermediate forging to obtain the titanium alloy intermediate bar blank. Among them, the deformation amount is 20 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0052] Step 4: Perform machining treatment on the titanium alloy intermediate bar blank produced in Step 3, and conduct ultrasonic flaw detection and physical and chemical property testing. After the test results meet the standards, determine the blanking size of the bar blank according to the size of the preform forging blank, and then forge the blanked titanium alloy intermediate bar blank into a preform forging blank by open die forging. Specifically, the heating temperature during open die forging is β - (80 - 100) °C, the holding time is 600 - 700 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0053] Step 5: Coat the surface of the preform forging blank and the inner surface of the preform forging die, and then perform preform forging on the preform forging blank using a large-tonnage open die forging equipment to obtain a semi-finished titanium alloy special-shaped forging. Specifically, the coating applied to the surface of the preform forging blank is a lubricating heat-insulating coating, and the coating is TB1200 - 16. The coating applied to the inner surface of the preform forging die is a molybdenum disulfide coating, so as to ensure the final forging temperature, reduce surface cracks of the forging, and at the same time reduce the surface friction during the deformation process of the forging blank in the die, ensuring the smooth forming of the blank.

[0054] Specifically, the heating temperature during preform forging is β - (80 - 100) °C, the holding time is 600 - 700 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

[0055] Step 6: Heat-treat the semi-finished titanium alloy special-shaped forging to obtain the large-size titanium alloy special-shaped forging. Specifically, heat the semi-finished titanium alloy special-shaped forging to 870 - 900 °C and hold for 2 - 2.4 h, then cool it in the furnace to 730 - 750 °C and hold for 2 - 2.4 h, and then air-cool it to room temperature; then heat the semi-finished titanium alloy special-shaped forging to 630 - 650 °C and hold for 6 - 7 h, and then air-cool it to room temperature. Finally, a titanium alloy special-shaped forging with a single weight ≥ 600 Kg, a projected area ≥ 1.4 m², and a maximum width ≥ 1350 mm is obtained. The titanium alloy special-shaped forging includes the following chemical components by weight percentage: Al: 4.5% - 5.7%, Mo: 4.0% - 5.5%, V: 4.0% - 5.5%, Cr: 0.5% - 1.5%, Fe: 0.5% - 1.5%, C ≤ 0.08%, Zr ≤ 0.30%, Si ≤ 0.15%, O ≤ 0.18%, N ≤ 0.05%, H ≤ 0.15%.

[0056] The microstructures of the titanium alloy special-shaped forgings prepared in Examples 1 to 3 are as Figures 1 to 3 shown. It can be seen from the figure that the microstructures of the forgings are all two-phase zone processing microstructures with good spheroidization, meeting the requirements of relevant technical conditions.

[0057] The mechanical property test results of the titanium alloy special-shaped forgings prepared in Examples 1 to 3 are shown in Figures 4 to 16 . The test results show that the mechanical properties of the titanium alloy special-shaped forgings prepared in the three examples all meet the technical standard requirements, and the large-size titanium alloy special-shaped forgings prepared by the present invention meet the titanium demand for heavy rockets in China.

[0058] 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 be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a large-sized titanium alloy special-shaped forging, characterized in that, Including: Step 1: Use a vacuum consumable arc furnace for vacuum induction melting to obtain a titanium alloy ingot, and the diameter of the titanium alloy ingot ≥ 800 mm and the weight ≥ 6 tons; Step 2: After heating and insulating the titanium alloy ingot, perform cogging forging on it above the phase transformation point to obtain a titanium alloy forging blank; Step 3: After heating the titanium alloy forging blank, adopt a multi-pass plastic deformation process to obtain a titanium alloy intermediate bar blank, and the diameter of the titanium alloy intermediate bar blank ≥ 600 mm; In Step 3, heat the titanium alloy forging blank to a temperature of (β - 100) - 1100 °C and hold for 400 - 700 min, then perform multi-pass intermediate forging to obtain the titanium alloy intermediate bar blank; where the deformation amount is 20 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C; Step 4: Determine the bar blank cutting size according to the size of the die forging blank, and then forge the cut titanium alloy intermediate bar blank into a die forging blank by open die forging; In Step 4, the heating temperature during open die forging is β - (0 - 100) °C, the holding time is 400 - 700 min, the deformation amount is 20% - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C; Step 5: Coat the surface of the die forging blank and the inner surface of the die forging mold, and then perform die forging on the die forging blank using a large-tonnage open die forging equipment to obtain a semi-finished titanium alloy special-shaped forging; Step 6: Perform heat treatment on the semi-finished titanium alloy special-shaped forging to obtain the large-size titanium alloy special-shaped forging, and the single weight of the large-size titanium alloy special-shaped forging ≥ 600 Kg, the projected area ≥ 1.4 m², and the maximum width ≥ 1350 mm; the large-size titanium alloy special-shaped forging includes the following chemical components by weight percentage: Al: 4.5% - 5.7%, Mo: 4.0% - 5.5%, V: 4.0% - 5.5%, Cr: 0.5% - 1.5%, Fe: 0.5% - 1.5%, C ≤ 0.08%, Zr ≤ 0.30%, Si ≤ 0.15%, O ≤ 0.18%, N ≤ 0.05%, H ≤ 0.15%; The heat treatment in Step 6 refers to: heating the semi-finished titanium alloy special-shaped forging to 800 - 900 °C and holding for 2 - 3 h, then furnace cooling to 700 - 750 °C and holding for 2 - 3 h, and then air cooling to room temperature; then heating the semi-finished titanium alloy special-shaped forging to 600 - 650 °C and holding for 6 - 8 h, and then air cooling to room temperature.

2. The method for preparing a large-sized titanium alloy special-shaped forging according to claim 1, characterized in that, In Step 1, the melting current for vacuum induction melting is 22 - 28 kA, the melting voltage is 30 - 40 V, and the vacuum degree of the melting chamber ≤ 5 Pa.

3. The method for preparing a large-sized titanium alloy special-shaped forging according to claim 1, characterized in that, In Step 2, the heating temperature is 1100 - 1200 °C, the holding time is 300 - 500 min, the deformation amount is 40 - 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600 °C.

4. The method for preparing a large-sized titanium alloy special-shaped forging according to claim 1, characterized in that, In the step 5, the heating temperature during the semi-closed die forging is β-(0 to 100)°C, the heat preservation time is 400 to 700 min, the deformation amount is 20% to 80%, the deformation speed is less than 40 mm / s, and the final forging temperature is not lower than 600°C.

5. The method for preparing a large-sized titanium alloy special-shaped forging according to claim 1, characterized in that, In the step 5, the coating applied on the surface of the semi-closed die forging blank is TB1200-16, and the coating applied on the inner surface of the semi-closed die forging die is molybdenum disulfide coating.

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