Forging method for large-sized forging blank of TC4-DT titanium alloy

Abstract

The present invention discloses a forging method for large-sized forgings of TC4-DT titanium alloy, specifically as follows: First, the ingot is subjected to cogging forging for 1 to 2 heats, then intermediate forging is carried out for 6 to 12 heats by means of supplementary heating forging and repeated upsetting and drawing, and finally forming forging is carried out for 4 to 8 heats below the phase transformation point. In the present invention, the cogging forging increases the deformation amount in the β phase region and controls the forging ratio, so that the as-cast grains are fully broken; multiple supplementary heating recrystallizations enable the billet to be fully recrystallized in each part, and the billet structure is uniformly refined; the method of repeated upsetting and drawing with supplementary heating and variable cross-section in multiple forms is adopted to improve the uniformity of the temperature field and strain field of the billet; during forming forging, the two-way stretching deformation method with stepped deformation amount is adopted to improve the uniformity of the cross-sectional structure of the forging blank, and in the last heat, the small deformation and small feeding method is adopted to increase the final forging temperature of the forging blank, and finally a large-sized forging blank of TC4-DT titanium alloy with a low-magnification structure that is uniformly blurred, a high-magnification structure that is uniformly fine, and a high matching of strength and plasticity is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy processing, and particularly relates to a forging method for large-sized forgings of TC4-DT titanium alloy, which is particularly suitable for preparing TC4-DT titanium alloy forgings with a thickness of 90 mm to 250 mm, a width of 500 mm to 2000 mm, and a length of 2000 mm to 5000 mm and having uniform tissue properties. Background Art

[0002] TC4-DT titanium alloy is a damage-tolerant titanium alloy with independent intellectual property rights developed in China. It belongs to a medium-strength (860 MPa level) damage-tolerant titanium alloy. Since this alloy has a certain strength level while also having a low crack growth rate (da / dN) and a high fracture toughness (KIC), compared with other medium-strength alloys, under the condition of comparable strength and plasticity levels, this alloy also has excellent electron beam welding performance and is suitable for manufacturing key load-bearing components such as integral large frames, beams, and joints. Therefore, it can be used as an important structural material in the aerospace and aviation fields.

[0003] In recent years, with the completion of domestic large-scale forging equipment, the method of "segmented forging - segmented machining - welding combination" that was previously forced to be used to manufacture ultra-large titanium alloy main load-bearing frames has been optimized to integral forging of integral forgings, and the raw materials used have changed from bars to large-sized forgings. Due to the large size of the forgings, the required ingot size becomes larger, and the control difficulty of the composition uniformity of the ingot and the composition, structure, and properties of the forgings increases. Due to the limitations of equipment capabilities and forging techniques, the uniformity of the structure and properties of the forgings cannot meet the requirements by traditional forging methods of forgings.

[0004] In view of this, the inventor of the present invention proposes a forging method for large-sized forgings of TC4-DT titanium alloy to overcome the defects of the prior art. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a forging method for large-sized forgings of TC4-DT titanium alloy. By using this method to forge large-sized forgings of TC4-DT titanium alloy, the overall macro and microstructures are significantly improved, the air-burning structure is uniform, and the structure and properties of the forgings are better matched.

[0006] The purpose of the present invention is solved by the following technical solutions:

[0007] A forging method for large-sized forgings of TC4-DT titanium alloy, wherein the raw material of the large-sized forgings of TC4-DT titanium alloy is a 3 - 4 ton-level TC4-DT titanium alloy ingot produced by triple melting in a vacuum consumable arc furnace, and is characterized in that the forging method comprises the following steps;

[0008] Step 1. Blooming forging:

[0009] Perform blooming forging on the TC4-DT titanium alloy ingot for 1 to 2 heats. The starting forging temperature for each heat is 50°C to 150°C above the β phase transformation point, and the finishing forging temperature for each heat is 20°C to 80°C below the β phase transformation point. For each heat, 2 to 3 upsetting and drawing operations are performed, and the forging ratio for each heat is controlled between 3 and 8 to obtain the first forging blank.

[0010] Step 2. Intermediate forging:

[0011] First stage: Perform repeated upsetting and drawing on the first forging blank obtained in Step 1 from below the phase transformation point to above the phase transformation point for 2 to 4 heats. The reheating method is used for temperature compensation between heats. The forging ratio for each heat is controlled between 1.3 and 5.0 to obtain the second forging blank.

[0012] Second stage: Perform repeated upsetting and drawing on the obtained second forging blank below the phase transformation point for 4 to 8 heats. The reheating method is used for temperature compensation between heats. The forging ratio for each heat is controlled between 1.2 and 5.0 to obtain the third forging blank.

[0013] Step 3. Forming forging:

[0014] Perform forming forging on the third forging blank obtained in Step 2 for 4 to 8 heats to obtain the TC4-DT titanium alloy forging blank.

[0015] Furthermore, forging in Step 1 to Step 3 is all performed using a quick forging machine.

[0016] Furthermore, during the intermediate forging in Step 2, in the first stage, the starting forging temperature for each heat below the phase transformation point is 50°C to 100°C below the β phase transformation point, and the finishing forging temperature for each heat is 100°C to 200°C below the β phase transformation point; the starting forging temperature for each heat above the phase transformation point is 30°C to 80°C above the β phase transformation point, and the finishing forging temperature for each heat is 50°C to 100°C below the β phase transformation point.

[0017] Furthermore, during the intermediate forging in Step 2, in the second stage, the starting forging temperature for each heat is 50°C to 100°C below the β phase transformation point, and the finishing forging temperature for each heat is 100°C to 200°C below the β phase transformation point.

[0018] Furthermore, during the upsetting and drawing in the first stage and the second stage in Step 2, tools with different cross-sectional sizes of 500 mm to 2000 mm are alternately used to upset and draw the forging blank in different directions.

[0019] Furthermore, during the forming forging in Step 3, the starting forging temperature for each forming forging is 50°C to 100°C below the β phase transformation point, and the finishing forging temperature for each forming forging is 100°C to 200°C below the β phase transformation point. The cumulative forging ratio is controlled between 5.0 and 10.0.

[0020] Furthermore, during the forming forging in Step 3, a two-way stretching deformation method with a stepped deformation amount is adopted.

[0021] Furthermore, during the forming forging in Step 3, for the last heat of the forging blank, a forging method with small deformation and small feeding is adopted, where the reduction amount is less than or equal to 20 mm and the feeding amount is less than or equal to 200 mm.

[0022] Furthermore, the forging method can be used to produce TC4-DT titanium alloy forging blanks with a thickness of 90 mm to 250 mm, a width of 500 mm to 2000 mm, and a length of 2000 mm to 5000 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention first controls the starting forging temperature and the final forging temperature of the bloom forging, increases the forging deformation amount in the β-phase region, that is, controls the forging ratio of each heat to be 3 to 8, fully breaks the large-sized as-cast grains at the edge of the TC4-DT titanium alloy bloom material, reduces the grain size of the TC4-DT titanium alloy bloom material, and improves the tissue uniformity.

[0025] 2. The present invention adopts the method of reheating for temperature compensation forging for multi-pass recrystallization forging, enabling the material to recrystallize quickly and fully, ensuring the uniform refinement of the billet structure; at the same time, improving the uniformity of the forging temperature field of the intermediate billet and reducing the tissue difference between the edge and the core of the whole intermediate billet caused by the temperature difference of the billet.

[0026] 3. When upsetting and stretching in the present invention, a variable cross-section and multi-form upsetting and stretching method is used, that is, alternately using tooling with different cross-section sizes of 500 mm to 2000 mm to upset and stretch the material in different directions, so that different parts of the billet reach the same degree of deformation to ensure the uniformity of the tissue properties of the final finished forging blank.

[0027] 4. During the forming forging process of the forging blank, a two-way stretching deformation method with a stepped deformation amount is adopted. As the thickness of the forging blank decreases, the forging reduction amount gradually decreases from 80 mm to 150 mm to 5 mm to 30 mm, and axial and radial stretching are alternately performed during stretching to ensure that while the forging blank reaches the target size, the tissue properties at different positions of its cross-section are uniform and consistent; and for the last heat, a forging method with small deformation and small feeding with a reduction amount not exceeding 20 mm and a feeding amount not exceeding 200 mm is adopted to increase the final forging temperature of the forging blank and ensure the flatness of the finished forging blank. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is a flowchart of a forging method for a large-sized TC4-DT titanium alloy forging blank of the present invention;

[0031] Figure 2 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 1 of the present invention;

[0032] Figure 3 is a microstructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 1 of the present invention;

[0033] Figure 4 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 2 of the present invention;

[0034] Figure 5 is a microstructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 2 of the present invention;

[0035] Figure 6 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 3 of the present invention;

[0036] Figure 7 is a microstructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 3 of the present invention;

[0037] Figure 8 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 4 of the present invention;

[0038] Figure 9 is a microstructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Embodiment 4 of the present invention;

[0039] Figure 10 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Comparative Example 1;

[0040] Figure 11 is a microstructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Comparative Example 1;

[0041] Figure 12 is a macrostructure diagram of the large-sized TC4-DT titanium alloy forging blank forged in Comparative Example 2;

[0042] Figure 13It is the high-magnification microstructure diagram of the large-sized forged blank of TC4-DT titanium alloy forged in Comparative Example 2; Detailed implementation mode

[0043] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation modes described in the following exemplary embodiments do not represent all implementation modes consistent with the present invention. On the contrary, they are only examples of devices consistent with some aspects of the present invention detailed in the appended claims.

[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0045] Please refer to Figure 1 As shown, the present invention provides a forging method for a large-sized forged blank of TC4-DT titanium alloy. The raw material of the large-sized forged blank of TC4-DT titanium alloy is a 3-4 ton-level TC4-DT titanium alloy ingot produced by triple melting in a vacuum consumable arc furnace. It is characterized in that the forging method includes the following steps;

[0046] Step 1. Blooming forging:

[0047] Use a quick forging machine to perform 1-2 heat treatments of blooming forging on the TC4-DT titanium alloy ingot. The initial forging temperature for each heat treatment is 50°C to 150°C above the phase transformation point, and the final forging temperature is 20°C to 80°C below the phase transformation point. For each heat treatment, 2-3 upsetting and drawing operations are performed, and the forging ratio for each heat treatment is controlled between 3 and 8 to obtain a first forged blank;

[0048] Step 2. Intermediate forging (in two stages):

[0049] The first stage: Perform 2-4 heat treatments of repeated upsetting and drawing on the first forged blank obtained in Step 1 from below the phase transformation point to above the phase transformation point. The initial forging temperature for the heat treatments below the phase transformation point is 50°C to 100°C below the phase transformation point, and the final forging temperature is 100°C to 200°C below the phase transformation point; the initial forging temperature for the heat treatments above the phase transformation point is 30°C to 80°C above the phase transformation point, and the final forging temperature is 50°C to 100°C below the phase transformation point. The forging ratio for each heat treatment is controlled between 1.3 and 5.0 to obtain a second forged blank;

[0050] The second stage: Perform 4-8 heat treatments of repeated upsetting and drawing on the obtained second forged blank below the phase transformation point. When upsetting and drawing, use a variable cross-section and multi-form upsetting and drawing method. The initial forging temperature for each heat treatment is 50°C to 100°C below the phase transformation point, and the final forging temperature is 100°C to 200°C below the phase transformation point. The forging ratio for each heat treatment is controlled between 1.2 and 5.0 to obtain a third forged blank;

[0051] Step 3. Forming forging:

[0052] The third forging blank obtained in Step 2 is subjected to forming forging for 4 to 8 heats. The starting forging temperature for each forming forging is 50°C to 100°C below the phase transformation point, and the ending forging temperature for each is 100°C to 200°C below the phase transformation point. The cumulative forging ratio is controlled between 5.0 and 10.0, and a two-way stretching deformation method with a stepped deformation amount is adopted. In the last heat, a small deformation and small feeding forging method with a reduction amount not exceeding 20 mm and a feeding amount not exceeding 200 mm is used, thus obtaining a TC4-DT titanium alloy forging blank with a thickness of 90 mm to 250 mm, a width of 500 mm to 2000 mm, and a length of 2000 mm to 5000 mm.

[0053] To further verify the efficacy of the forging method of the present invention, the inventor carried out the following specific examples:

[0054] Example 1 (forging blank of 205×1400×2300 mm)

[0055] 1) A 4-ton TC4-DT titanium alloy ingot with a specification of Φ890 mm is subjected to cogging forging by a quick forging machine to obtain a first forging blank. The cogging forging adopts a forging method of repeated upsetting and stretching, and is completed in 2 heats, with 3 upsetting and stretching operations in each heat. The starting forging temperature of the cogging forging is 50°C above the β phase transformation point, and the ending forging temperature is 80°C below the β phase transformation point. The forging ratio of each heat of the cogging forging is 3.15. The first forging blank obtained by processing has a square cross-section with a side length of 870 mm.

[0056] 2) The first forging blank obtained in step 1) is subjected to intermediate forging by a quick forging machine to obtain a second forging blank. The intermediate forging adopts a forging method of low-high heating and repeated upsetting and stretching, and is completed in a total of 4 heats. Reheating for temperature compensation is carried out between heats. A 550-mm flat anvil and a 2000-mm flat anvil are used alternately. The starting forging temperature of each heat of the intermediate forging in the two-phase region is 50°C below the β phase transformation point, and the ending forging temperature is 110°C below the β phase transformation point. The forging ratio of each heat is 1.5. The starting forging temperature of each heat of the intermediate forging in the single-phase region is 80°C above the β phase transformation point, and the ending forging temperature is 50°C below the β phase transformation point. The forging ratio of each heat is 1.4. The second forging blank obtained by processing has a square cross-section with a side length of 690 mm.

[0057] 3) The second forging blank obtained in step 2) is subjected to intermediate forging by a quick forging machine to obtain a third forging blank. The intermediate forging adopts a forging method of repeated upsetting and stretching, and is completed in a total of 8 heats. Reheating for temperature compensation is carried out between heats. A 700-mm flat anvil and a 1200-mm flat anvil are used alternately. The starting forging temperature of the intermediate forging is 50°C below the β phase transformation point, and the ending forging temperature is 100°C below the β phase transformation point. The forging ratio of each heat of the intermediate forging is 1.3. The third forging blank obtained by processing has a cross-section of 650×1050.

[0058] 4) The third forging blank obtained in step 3) is subjected to forming forging by a fast forging machine to obtain a fourth forging blank. The forming forging adopts a forging method with stepped feed and stepped deformation, and is completed in a total of 4 heating passes. As the thickness of the forging blank decreases, the forging reduction amount gradually decreases from 140 mm to 25 mm. During drawing out, axial and radial drawing out are alternated. The starting forging temperature of the forming forging is 60 °C below the β phase transformation point, and the final forging temperature of the forming forging is 110 °C below the β phase transformation point. The cumulative forging ratio of the forming forging is 5.5. The processed fourth forging blank is a 3-ton forging blank with a cross-section of 205×1400. The microstructure of the large-sized TC4-DT titanium alloy forging blank processed by this embodiment is as Figure 2 and 3 shown, and the performance data is shown in Table 1 below.

[0059] Example 2 (forging blank of 145×1800×2800 mm)

[0060] 1) A 4-ton TC4-DT titanium alloy ingot with a specification of Φ890 mm is subjected to cogging forging by a fast forging machine to obtain a first forging blank. The cogging forging adopts a forging method of repeated upsetting and drawing out, and is completed in 1 heating pass, with a total of 2 upsetting and drawing out operations. The starting forging temperature of the cogging forging is 150 °C above the β phase transformation point, and the final forging temperature of the cogging forging is 20 °C below the β phase transformation point. The forging ratio per heating pass of the cogging forging is 7.47. The processed first forging blank has a square cross-section with a side length of 870 mm.

[0061] 2) The first forging blank obtained in step 1) is subjected to intermediate forging by a fast forging machine to obtain a second forging blank. The intermediate forging adopts a forging method of low-high heating and repeated upsetting and drawing out, and is completed in a total of 2 heating passes. Reheating for temperature compensation is carried out between heating passes. A 550-mm flat anvil and a 2000-mm flat anvil are alternately used. The starting forging temperature of each heating pass of the intermediate forging in the two-phase region is 95 °C below the β phase transformation point, and the final forging temperature is 200 °C below the β phase transformation point. The forging ratio per heating pass is 4.8. The starting forging temperature of each heating pass of the intermediate forging in the single-phase region is 30 °C above the β phase transformation point, and the final forging temperature is 90 °C below the β phase transformation point. The forging ratio per heating pass is 4.6. The processed second forging blank has a square cross-section with a side length of 690 mm.

[0062] 3) The second forging blank obtained in step 2) is subjected to intermediate forging by a fast forging machine to obtain a third forging blank. The intermediate forging adopts a forging method of repeated upsetting and drawing out, and is completed in a total of 4 heating passes. Reheating for temperature compensation is carried out between heating passes. A 700-mm flat anvil and a 1200-mm flat anvil are alternately used. The starting forging temperature of the intermediate forging is 90 °C below the β phase transformation point, and the final forging temperature of the intermediate forging is 200 °C below the β phase transformation point. The forging ratio per heating pass is 4.7. The processed third forging blank is a forging blank with a cross-section of 650×1250.

[0063] 4) Use a quick forging machine to perform forming forging on the third forging blank obtained in step 3) to obtain a fourth forging blank. The forming forging adopts a forging method with stepped feed and stepped deformation, and is completed in a total of 8 heating passes. As the thickness of the forging blank decreases, the forging reduction gradually decreases from 130 mm to 20 mm. During drawing out, axial and radial drawing out are alternated. The starting forging temperature of the forming forging is 90 °C below the β phase transformation point, and the final forging temperature of the forming forging is 200 °C below the β phase transformation point. The cumulative forging ratio of the forming forging is 9.7. The processed fourth forging blank is a 3-ton forging blank with a cross-section of 145×1800. The microstructure of the large-sized TC4-DT titanium alloy forging blank processed by this embodiment is as Figure 4 and 5 shown, and the performance data is as shown in Table 1 below.

[0064] Example 3 (240×600×4700 mm forging blank)

[0065] 1) Use a quick forging machine to perform cogging forging on a 4-ton TC4-DT titanium alloy ingot with a specification of Φ890 mm to obtain a first forging blank. The cogging forging adopts a forging method of repeated upsetting and drawing out, and is completed in 2 heating passes. 2 upsetting and drawing out operations are completed in each heating pass. The starting forging temperature of the cogging forging is 120 °C above the β phase transformation point, and the final forging temperature of the cogging forging is 50 °C below the β phase transformation point. The forging ratio of each heating pass of the cogging forging is 3.75. The processed first forging blank has a square cross-section with a side length of 870 mm.

[0066] 2) Use a quick forging machine to perform intermediate forging on the first forging blank obtained in step 1) to obtain a second forging blank. The intermediate forging adopts a forging method of low-high heating and repeated upsetting and drawing out, and is completed in a total of 2 heating passes. Reheating for temperature compensation is carried out between heating passes. A 550 mm flat anvil and a 2000 mm flat anvil are used alternately. The starting forging temperature of each heating pass of the intermediate forging in the two-phase region is 60 °C below the β phase transformation point, and the final forging temperature is 130 °C below the β phase transformation point. The forging ratio of each heating pass is 4.7. The starting forging temperature of each heating pass of the intermediate forging in the single-phase region is 50 °C above the β phase transformation point, and the final forging temperature is 80 °C below the β phase transformation point. The forging ratio of each heating pass is 4.5. The processed second forging blank is a flat square with a cross-section of 650 mm×870 mm.

[0067] 3) Use a quick forging machine to perform intermediate forging on the second forging blank obtained in step 2) to obtain a third forging blank. The intermediate forging adopts a forging method of repeated upsetting and drawing out, and is completed in a total of 6 heating passes. Reheating for temperature compensation is carried out between heating passes. A 700 mm flat anvil and a 1200 mm flat anvil are used alternately. The starting forging temperature of the intermediate forging is 80 °C below the β phase transformation point, and the final forging temperature of the intermediate forging is 150 °C below the β phase transformation point. The forging ratio of each heating pass is 3.75. The processed third forging blank has a square cross-section with a side length of 750 mm.

[0068] 4) The third forging billet obtained in step 3) is subjected to forming forging by a quick forging machine to obtain a fourth forging billet. The forming forging adopts a forging method with stepped feed and stepped deformation, and is completed in a total of 4 heating passes. As the thickness of the forging billet decreases, the forging reduction amount gradually decreases from 110 mm to 20 mm. The starting forging temperature of the forming forging is 80 °C below the β phase transformation point, and the final forging temperature of the forming forging is 150 °C below the β phase transformation point. The cumulative forging ratio of the forming forging is 5.9. The processed fourth forging billet is a 3-ton forging billet with a cross-section of 240×600. The microstructure of the large-sized TC4-DT titanium alloy forging billet processed by this embodiment is as Figure 6 and 7 shown, and the performance data is shown in Table 1 below.

[0069] Example 4 (100×1500×4200 mm forging billet)

[0070] 1) A 4-ton TC4-DT titanium alloy ingot with a specification of Φ690 mm is subjected to cogging forging by a quick forging machine to obtain a first forging billet. The cogging forging adopts a forging method of repeated upsetting and drawing, and is completed in 1 heating pass, with a total of 3 upsetting and drawing operations. The starting forging temperature of the cogging forging is 130 °C above the β phase transformation point, and the final forging temperature of the cogging forging is 30 °C below the β phase transformation point. The forging ratio per heating pass of the cogging forging is 7.1. The processed first forging billet has a square cross-section with a side length of 650 mm.

[0071] 2) The first forging billet obtained in step 1) is subjected to intermediate forging by a quick forging machine to obtain a second forging billet. The intermediate forging adopts a forging method of low-high heating and repeated upsetting and drawing, and is completed in a total of 2 heating passes. The furnace is used for re-heating between heating passes, and 550 mm flat anvils and 2000 mm flat anvils are used alternately. The starting forging temperature of each heating pass of the intermediate forging in the two-phase region is 50 °C below the β phase transformation point, and the final forging temperature is 190 °C below the β phase transformation point. The forging ratio per heating pass is 4.5. The starting forging temperature of each heating pass of the intermediate forging in the single-phase region is 70 °C above the β phase transformation point, and the final forging temperature is 60 °C below the β phase transformation point. The forging ratio per heating pass is 4.5. The processed second forging billet has a square cross-section with a side length of 650 mm.

[0072] 3) The second forging billet obtained in step 2) is subjected to intermediate forging by a quick forging machine to obtain a third forging billet. The intermediate forging adopts a forging method of repeated upsetting and drawing, and is completed in a total of 4 heating passes. The furnace is used for re-heating between heating passes, and 700 mm flat anvils and 1200 mm flat anvils are used alternately. The starting forging temperature of the intermediate forging is 50 °C below the β phase transformation point, and the final forging temperature of the intermediate forging is 100 °C below the β phase transformation point. The forging ratio per heating pass is 1.85. The processed third forging billet has a square cross-section with a side length of 850 mm.

[0073] 4) The third forging blank obtained in step 3) is subjected to forming forging by a quick forging machine to obtain a fourth forging blank. The forming forging adopts a forging method with stepped feed and stepped deformation, and is completed in a total of 5 heating passes. As the thickness of the forging blank decreases, the forging reduction amount gradually decreases from 100 mm to 5 mm. During drawing out, axial and radial drawing out are alternated. The starting forging temperature of the forming forging is 50 °C below the β phase transformation point, and the final forging temperature of the forming forging is 100 °C below the β phase transformation point. The cumulative forging ratio of the forming forging is 6. The processed fourth forging blank is a 3-ton forging blank with a cross-section of 100×1500. The microstructure of the large-sized TC4-DT titanium alloy forging blank processed by this embodiment is as shown in Figure 8 and 9 shown, and the performance data is as shown in Table 1 below.

[0074] Comparative Example 1

[0075] This comparative example adopts a traditional intermediate blank forging process below the β phase transformation point. The difference between the processing method of the large-sized TC4-DT titanium alloy forging blank in this comparative example and that of Example 1 lies in that in step one, the cogging forging has a total of 2 heating passes, 2 upsetting and drawing out operations for each heating pass, and the forging ratio for each heating pass is 2.7. In step three, the repeated upsetting and drawing out operations all adopt 500 mm flat anvil forging, and the method of alternating flat anvils with different cross-sections is not adopted. The microstructure of the large-sized TC4-DT titanium alloy forging blank processed by this comparative example is as shown in Figure 10 and 11 shown, and the performance data is as shown in Table 1 below.

[0076] Comparative Example 2

[0077] This comparative example adopts a traditional intermediate blank forging process above the β phase transformation point. The difference between the processing method of the large-sized TC4-DT titanium alloy forging blank in this comparative example and that of Example 4 lies in that in step one, the cogging forging has a total of 1 heating pass, 2 upsetting and drawing out operations, and the forging ratio for the heating pass is 2.5. In step two, the multi-heating passes do not adopt the method of reheating and temperature compensation for forging. The microstructure of the large-sized TC4-DT titanium alloy forging blank processed by this comparative example is as shown in Figure 12 and 13 shown, and the performance data is as shown in Table 1 below.

[0078] Table 1 shows the performance test data of the large-sized TC4-DT titanium alloy forging blank

[0079]

[0080]

[0081] In summary, as can be seen from the data in Table 1, compared with the traditional processes of Comparative Example 1 and Comparative Example 2, for the large-sized forging blanks of TC4-DT titanium alloy forged by the present invention in Examples 1 to 4 of the present invention, the overall mechanical properties are further improved. For example, the average tensile strength is increased by 14.5 MPa, the average yield strength is increased by 10.75 MPa, and the elongation and reduction of area are the same as those of the prior art.

[0082] As Figures 2 to 13 can be seen, compared with the traditional processes of Comparative Example 1 and Comparative Example 2, for the large-sized forging blanks of TC4-DT titanium alloy forged by the present invention, the macrostructure is uniform and blurred, the high-magnification primary α-phase is equiaxed or short rod-shaped, there is no long strip-shaped α-phase, the structure is uniform and fine, there is no streamline or cluster distribution, and the structural uniformity is significantly improved. The strength and yield of the forging blank are increased by refining the high-magnification structure, and the performance uniformity of the forging blank is improved by homogenizing the structure, reducing the risk of local failure of the material.

[0083] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0084] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A forging method for large-sized TC4-DT titanium alloy forgings. The raw material of the large-sized TC4-DT titanium alloy forgings is a 3-4 ton-level TC4-DT titanium alloy ingot produced by triple melting in a vacuum consumable arc furnace, characterized in that, The forging method includes the following steps; Step 1. Ingot cogging forging: The TC4-DT titanium alloy ingot is subjected to 1-2 cogging forging heats. The starting forging temperature for each heat is 50°C - 150°C above the β transformation point, and the finishing forging temperature for each heat is 20°C - 80°C below the β transformation point. 2-3 upsetting and drawing operations are performed for each heat, and the forging ratio for each heat is controlled between 3 and 8, obtaining the first forging blank; Step 2. Intermediate forging: First stage: The first forging blank obtained in Step 1 is subjected to repeated upsetting and drawing from below the transformation point to above the transformation point for 2-4 heats. The reheating method is used for temperature compensation between heats. The forging ratio for each heat is controlled between 1.3 and 5.0, obtaining the second forging blank; Second stage: The obtained second forging blank is subjected to repeated upsetting and drawing below the transformation point for 4-8 heats. The reheating method is used for temperature compensation between heats. The forging ratio for each heat is controlled between 1.2 and 5.0, obtaining the third forging blank; Step 3. Shaping forging: The third forging blank obtained in Step 2 is subjected to 4-8 heats of shaping forging, thus obtaining the TC4-DT titanium alloy forging blank; When performing intermediate forging in Step 2, for the heats below the transformation point in the first stage, the starting forging temperature is 50°C - 100°C below the β transformation point, and the finishing forging temperature is 100°C - 200°C below the β transformation point; for the heats above the transformation point, the starting forging temperature is 30°C - 80°C above the β transformation point, and the finishing forging temperature is 50°C - 100°C below the β transformation point; for each heat in the second stage, the starting forging temperature is 50°C - 100°C below the β transformation point, and the finishing forging temperature is 100°C - 200°C below the β transformation point; and when upsetting and drawing in the first stage and the second stage, tooling with different cross-sectional sizes of 500mm - 2000mm is alternately used to upset and draw the forging blank in different directions; When performing shaping forging in Step 3, the starting forging temperature for each shaping forging is 50°C - 100°C below the β transformation point, the finishing forging temperature is 100°C - 200°C below the β transformation point, the cumulative forging ratio is controlled between 5.0 and 10.0, and a two-way drawing deformation method with stepped deformation amounts is used. For the last heat of the forging blank, a forging method with a reduction amount less than or equal to 20mm and a feeding amount less than or equal to 200mm is adopted; 2. The forging method of a large-sized forged blank of TC4-DT titanium alloy according to claim 1, characterized in that, Steps 1 to 3 are all performed using a quick forging machine for forging.

3. The forging method of a large-sized TC4-DT titanium alloy forging blank according to claim 1 or 2, characterized in that, The forging method is used to produce TC4-DT titanium alloy forging blanks with a thickness of 90mm - 250mm, a width of 500mm - 2000mm, and a length of 2000mm - 5000mm.

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