Preparation method of high-homogeneity and large-specification TA18 titanium alloy bar

Abstract

The invention discloses a preparation method of a high-homogeneity and large-specification TA18 titanium alloy bar. The preparation method comprises the following steps: preparing a consumable electrode; the consumable electrode is subjected to vacuum consumable smelting for three times, and a cast ingot is obtained; the cast ingot is subjected to cogging forging, and a first forging stock is obtained; performing blank forging on the first forging stock to obtain a second forging stock; performing two-phase region forging on the second forging stock to obtain a third forging stock; performing single-phase region forging on the third forging stock to obtain a fourth forging stock; the fourth forging stock is subjected to two-phase region forging, and a fifth forging stock is obtained; and the fifth forging stock is subjected to forming forging and then subjected to annealing heat treatment, and the TA18 titanium alloy bar is obtained. By optimizing the smelting and forging process of the TA18 titanium alloy, the high-homogeneity and large-specification TA18 titanium alloy bar can be developed, the batch stability and the structure uniformity are good, the TA18 titanium alloy bar can be widely applied to the field of high-end equipment such as aerospace and chemical engineering, and the technology can achieve industrial application.

Description

Technical Field

[0001] The present invention relates to the technical fields of materials and metallurgy, and more specifically, to a method for preparing a high-homogeneity and large-size TA18 titanium alloy bar. Background Art

[0002] TA18 (Ti-3Al-2.5V) is a near-α type titanium alloy developed in the United States in the late 1960s. It has a variety of excellent physical and mechanical properties and is widely used in fields such as aerospace, chemical engineering, ocean engineering, and medical equipment. It exhibits high strength at both room temperature and high temperature. Its tensile strength can reach over 900 MPa, and the yield strength is about 800 MPa, which makes it suitable for various structural components that require high-strength support. TA18 titanium alloy shows excellent corrosion resistance in seawater and various chemical media and is suitable for use in harsh environments. Therefore, large-size TA18 titanium alloy tubes and bars have broad application prospects in aerospace, ocean engineering, chemical engineering, and other fields. Currently, the produced bars often have small sizes, which is not conducive to use in some special environments.

[0003] Therefore, it is necessary to provide a method for preparing a high-homogeneity and large-size TA18 titanium alloy bar. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for preparing a high-homogeneity and large-size TA18 titanium alloy bar, which has broad application prospects and can be applied to the preparation of large-size tubes, lightweight structural components, hydraulic pipelines of chemical equipment, and blanks for the preparation of aircraft fuel pipelines; this bar can also provide blanks for the preparation of TA18 titanium alloy seamless tubes, which is conducive to the preparation of large-size TA18 titanium alloy seamless tubes.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for preparing a high-homogeneity and large-size TA18 titanium alloy bar, comprising the following steps:

[0007] Mix sponge titanium, aluminum-vanadium alloy, aluminum granules, ferro-titanium alloy, and titanium dioxide to press multiple electrode blocks, and weld the multiple electrode blocks to obtain a consumable electrode;

[0008] Perform three times of vacuum consumable melting on the consumable electrode to obtain an ingot with a diameter of 250 - 1050 mm;

[0009] Perform cogging forging on the ingot. After peeling and flattening the primary ingot, heat it at 800 °C for 1 h and then raise the temperature to Tβ + 100 °C - Tβ + 200 °C, hold for 6 - 8 h, and then perform upsetting and drawing forging for 1 - 3 heats. After forging, air-cool and grind to obtain a first forged blank;

[0010] The first forging blank is subjected to blank forging modification. The first forging blank is held at 800 °C for 1 h and then heated to Tβ + 50 °C to Tβ + 100 °C, held for 6 - 8 h, and then subjected to repeated upsetting and drawing forging for 1 - 2 heats. After forging, it is air-cooled and ground to obtain the second forging blank;

[0011] The second forging blank is subjected to two-phase region forging. The second forging blank is held at 800 °C for 1 h and then heated to Tβ - 50 °C to Tβ - 30 °C, held for 4 - 6 h, and then subjected to repeated upsetting and drawing forging for 1 - 2 heats. After forging, it is air-cooled and ground to obtain the third forging blank;

[0012] The third forging blank is subjected to single-phase region forging. The third forging blank is held at 800 °C for 1 h and then heated to Tβ + 50 °C to Tβ + 100 °C, held for 4 - 6 h, and then subjected to repeated upsetting and drawing forging for 1 - 2 heats. After forging, it is air-cooled and ground to obtain the fourth forging blank;

[0013] The fourth forging blank is subjected to two-phase region forging. The fourth forging blank is held at 800 °C for 1 h and then heated to Tβ - 60 °C to Tβ - 30 °C, held for 2.5 - 4 h, and then subjected to repeated upsetting and drawing forging for 2 - 6 heats to obtain the fifth forging blank;

[0014] The fifth forging blank is subjected to shaping forging. The fifth forging blank is held at 800 °C for 1 h and then heated to Tβ - 60 °C to Tβ - 30 °C, held for 2.5 - 4 h and then taken out of the furnace, and subjected to drawing out and rolling round forging. The total forging ratio ≥ 3, and the final forging temperature ≥ 800 °C. After annealing heat treatment, the TA18 titanium alloy bar is obtained.

[0015] Optionally, the three times of vacuum consumable melting includes: the ingot element input values are: Al: 3.0 wt.%, V: 2.50 wt.%, Fe: 0.2 wt.%, O: 0.1 wt.%; using sponge titanium, AlV alloy, aluminum pellets, ferro-titanium alloy, titanium dioxide powder for mixing and pressing multiple electrode blocks. The TiO2 powder needs to be baked in an oven at above 150 °C in advance. After welding multiple electrode blocks, a consumable electrode is obtained, and vacuum plasma welding is used; after welding the consumable electrode and the auxiliary electrode, three times of vacuum consumable melting is carried out. The vacuum degree ≤ 1.0 Pa, the vacuum leakage rate ≤ 1.0 Pa / min, the melting current ≥ 45 kA, the melting voltage is 15 - 60 V; the feeding time ≥ 2.5 h.

[0016] Optionally, the cogging forging of the ingot further includes: the upsetting downward rate is 20 - 50 mm / s, the drawing is reverse drawing, the drawing is octagonal drawing, the length restores the height-diameter ratio to 1.75 - 2.2, the forging ratio per heat ≥ 2, the starting forging temperature ≥ 1000 °C, and the final forging temperature ≥ 950 °C.

[0017] Optionally, the forging reduction of the first forging blank further includes: diagonal drawing is used for both forging upsetting and drawing, the forging reduction per heat is ≥2.6, and the final forging temperature is ≥800°C.

[0018] Optionally, the two-phase region forging of the second forging blank further includes: the forging reduction per heat is ≥2.6, and the final forging temperature is ≥800°C.

[0019] Optionally, the single-phase region forging of the third forging blank further includes: the deformation per heat is 20-30%, and the final forging temperature is ≥850°C.

[0020] Optionally, the two-phase region forging of the fourth forging blank further includes: diagonal drawing and reverse drawing are alternately performed, the forging reduction per heat is ≥2.6, the total forging reduction is ≥10, and the final forging temperature is ≥800°C.

[0021] Optionally, the ingot consists of the following elements: Al: 2.5-3.5 wt.%, V: 1.50-3.00 wt.%.

[0022] Optionally, the size of the TA18 titanium alloy bar is Φ200-500 mm.

[0023] Optionally, the annealing heat treatment includes: holding at 650-800°C for 4-8 h, and then air cooling.

[0024] Implementing the embodiments of the present invention will have the following beneficial effects:

[0025] By optimizing the melting and forging processes of TA18 titanium alloy, a titanium alloy ingot with a diameter of 250-1050 mm is obtained through three times of VAR vacuum consumable melting. Then, a forging machine or a hydraulic press is used to repeatedly upset and draw the billet through multiple heats above and below the β phase transformation point. Finally, the billet is drawn to the required size at T β -50°C to T β -30°C. Through the implementation of this research, high-homogeneity and large-size TA18 titanium alloy bars can be developed, with good batch stability and tissue uniformity. They can be widely used in high-end equipment fields such as aerospace and chemical engineering. The technology can be industrially applied, greatly improving the product competitiveness, having high product added value, and being promoted to other fields such as large-size lightweight pipelines, with considerable economic benefits and technical visibility. Description of the Drawings

[0026] Figure 1 It is the macrostructure of the TA18 bars with Φ250 mm and Φ350 mm specifications in Embodiments 1-2 of the present invention.

[0027] Figure 2 It is the 200x metallographic structure of the Φ250 mm bar of the present invention after heat treatment in Embodiment 1.

[0028] Figure 3 The metallographic structure at the edge and at the 1 / 2 radius of the Φ350mm bar after heat treatment in Example 2 of the present invention. Detailed implementation manners

[0029] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0030] Example 1

[0031] Produce TA18 titanium alloy bars with a production specification of Φ250mm.

[0032] Step 1: Ingot melting: The ingot element input values are: Al: 3.0wt.%, V: 2.50wt.%, Fe: 0.2wt.%, O: 0.1wt.%; Use sponge titanium, AlV alloy, aluminum pellets, ferro-titanium alloy, and titanium dioxide powder to mix and press multiple electrode blocks. The TiO2 powder needs to be baked in a baking oven at a temperature above 150°C in advance. After welding multiple electrode blocks, an ingot electrode is obtained. Use vacuum plasma welding to longitudinally weld the electrode; Perform three times of vacuum consumable melting on the ingot electrode, with a vacuum degree ≤ 1.0Pa and a vacuum leakage rate ≤ 1.0Pa / min; The obtained ingot shape is Φ950mm×1800mm.

[0033] Step 2: Blooming forging: Place the Φ870mm×570mm ingot after peeling, planing, and trisecting cutting in an electric heating furnace preheated to 800°C and keep it warm for 1 hour, then raise the temperature to 1150°C and keep it warm for 450min. After taking out of the furnace, use a quick forging machine to perform four upsetting and four drawing operations in reverse (restore the original direction). The upsetting downward rate is 30mm / s, and the drawing is reverse drawing. Draw the ingot into eight sides, and restore the height-diameter ratio to 1.75. The forging reduction ratio for each heat treatment is 2.3. During the process, it can be reheated in the furnace for 1.5h as needed. Place heat insulation cotton below and above the billet during the upsetting and drawing process for heat insulation. The starting forging temperature is 1000°C, the final forging temperature is 950°C, and after forging, air cooling is carried out, and the forged billet 1 is obtained by grinding, with eight sides of 590mm×1175mm.

[0034] Step 3: Billet re-forging: Place the forged billet 1 in an electric heating furnace preheated to 800°C and keep it warm for 1h, then raise the temperature to 960°C and keep it warm for 350min. After taking out of the furnace, use a quick forging machine to perform one heat treatment of three upsetting and three drawing operations. Both forging upsetting and drawing use diagonal drawing to ensure greater fragmentation of the grains. The forging reduction ratio for each heat treatment is 2.6. The final forging temperature is 800°C, and after forging, air cooling is carried out, and the forged billet 2 is obtained by grinding, with eight sides of 580mm×1155mm.

[0035] Step 4: Two-phase zone forging: Place the forging blank 2 in an electric heating furnace preheated to 800 °C and hold for 1 h, then raise the temperature to 890 °C and hold for 350 min. After taking it out of the furnace, use a quick forging machine to repeatedly upset and draw for 2 heats, with diagonal drawing, and the forging ratio for each heat is 2.6. The final forging temperature is 800 °C, and after forging, it is air-cooled. Grind to obtain the forging blank 3, octagonal 560*L mm.

[0036] Step 5: Single-phase zone forging: Place the forging blank 3 in an electric heating furnace preheated to 800 °C and hold for 1 h, then raise the temperature to 1020 °C and hold for 350 min. After taking it out of the furnace, use a quick forging machine to draw and upset twice, and the deformation amount for each heat of forging is 25%. The final forging temperature is 850 °C, and after forging, it is air-cooled. Grind to obtain the forging blank 4, octagonal 530*L mm.

[0037] Step 6: Two-phase zone forging: Place the forging blank 4 in an electric heating furnace preheated to 800 °C and hold for 1 h, then raise the temperature to 890 °C and hold for 320 min. After taking it out of the furnace, use a quick forging machine or a hydraulic press to repeatedly upset and draw for 4 heats. Diagonal drawing is used for the 1st and 3rd heats, and reverse drawing is used for the 2nd and 4th heats. Upset and draw twice for each heat, and the total forging ratio is 85. The final forging temperature is 800 °C to obtain the forging blank 5, octagonal 420*L mm.

[0038] Step 7: Forming forging: Place the forging blank 5 in an electric heating furnace preheated to 800 °C and hold for 1 h, then raise the temperature to 880 °C and hold for 300 min. After taking it out of the furnace, use a quick forging machine to draw and roll to the required size, and the total forging ratio is not less than 3. The final forging temperature is 800 °C to obtain the TA18 bar.

[0039] Step 8: Heat treatment. Anneal the Φ250 TA18 bar obtained in Step 7 at 700 °C for 360 min and then air-cool.

[0040] Example 2

[0041] Produce TA18 titanium alloy bars with a production specification of Φ350 mm.

[0042] Step 1: Ingot melting: The ingot element input values are: Al: 3.0 wt.%, V: 2.50 wt.%, Fe: 0.2 wt.%, O: 0.1 wt.%. Use sponge titanium, AlV alloy, aluminum pellets, ferro-titanium alloy, and titanium dioxide powder for mixing and pressing multiple electrode blocks. The TiO2 powder needs to be baked in an oven at over 150 °C in advance. After welding multiple electrode blocks, obtain a consumable electrode, and use vacuum plasma welding to longitudinally weld the electrodes; perform three vacuum consumable melting operations on the consumable electrode, with the vacuum degree ≤ 1.0 Pa and the vacuum leakage rate ≤ 1.0 Pa / min; the obtained ingot shape is Φ750 mm × 1500 mm.

[0043] Step 2: Blooming Forging: Place the peeled and end-faced Φ720mm×1400mm ingot in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 1150°C and hold for 380min. After taking out of the furnace, forge with a quick forging machine for 2 heats, change direction twice for each heat (restore the original direction) with two upsetting and two drawing operations, the upsetting downward rate is 30mm / s, and the drawing is diagonal drawing. When drawing, draw into eight sides and restore the height-diameter ratio to 1.75. The forging ratio for each heat is 2.3, and it can be reheated for 1.5h as needed during the process. Place insulating cotton below and above the billet during the upsetting and drawing process for heat preservation. The starting forging temperature is 1000°C, the final forging temperature is 950°C, and air cool after forging. Grind to obtain forging blank 1, octagonal with 710mm×L.

[0044] Step 3: Forging Blank Remachining: Place forging blank 1 in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 960°C and hold for 370min. After taking out of the furnace, perform two upsetting and two drawing operations with a quick forging machine for 2 heats. Both upsetting and drawing adopt diagonal drawing to ensure greater grain fragmentation. The forging ratio for each heat is 2.6. The final forging temperature is 800°C, and air cool after forging. Grind to obtain forging blank 2, octagonal with 700mm×L.

[0045] Step 4: Two-Phase Region Forging: Place forging blank 2 in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 890°C and hold for 360min. After taking out of the furnace, repeatedly upset and draw with a quick forging machine for 1 heat, using diagonal drawing. The forging ratio is 2.6. The final forging temperature is 800°C, and air cool after forging. Grind to obtain forging blank 3, octagonal with 680*L mm.

[0046] Step 5: Single-Phase Region Forging: Place forging blank 3 in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 1020°C and hold for 360min. After taking out of the furnace, perform two drawing and two upsetting operations with a quick forging machine for 1 heat, and the deformation amount for each heat is 30%. The final forging temperature is 850°C, and air cool after forging. Grind to obtain forging blank 4, octagonal with 670*L mm.

[0047] Step 6: Two-Phase Region Forging: Place forging blank 4 in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 890°C and hold for 340min. After taking out of the furnace, repeatedly upset and draw with a quick forging machine or a hydraulic press for 6 heats. Diagonal drawing is used for the 1st, 3rd, and 5th heats, and reverse diagonal drawing is used for the 2nd, 4th, and 6th heats. Two upsetting and two drawing operations are performed for each heat, and the total forging ratio is greater than 80. The final forging temperature is 800°C to obtain forging blank 5, octagonal with 550*L mm.

[0048] Step 7: Shaping Forging: Place forging blank 5 in an electric heating furnace preheated to 800°C and hold for 1h, then raise the temperature to 880°C and hold for 300min. After taking out of the furnace, draw and roll the forging blank with a quick forging machine to the required size, and the total forging ratio is not less than 3. The final forging temperature is 800°C to obtain TA18 bars.

[0049] Step 8: Heat treatment. Anneal the Φ350 TA18 bars obtained in Step 7 at 800 °C for 240 min, and then air cool.

[0050] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of this invention patent shall be subject to the appended claims.

Claims

1. A method for preparing a highly homogeneous, large-size TA18 titanium alloy bar, characterized in that: The following steps are involved: Using sponge titanium, aluminum-vanadium alloy, aluminum particles, ferrotitanium alloy, and titanium dioxide to mix and press a plurality of electrode blocks, and then welding the plurality of electrode blocks to obtain a consumable electrode; The consumable electrode is subjected to vacuum consumable melting three times to obtain an ingot with a diameter of 250 to 1050 mm; The ingot is subjected to blank forging, the primary ingot is peeled and flattened, kept at 800°C for 1 hour, then heated to Tβ+100°C to Tβ+200°C, kept at this temperature for 6 to 8 hours, subjected to upsetting forging for 1 to 3 times, air-cooled after forging, and ground to obtain a first forging blank; The first forging blank is subjected to billet reforging, the first forging blank is kept at 800°C for 1 hour, then heated to Tβ+50°C to Tβ+100°C, kept at this temperature for 6 to 8 hours, and then repeatedly upsetting and drawing forged for 1 to 2 times, air-cooled after forging, and ground to obtain a second forging blank; The second forging blank is subjected to two-phase zone forging, the second forging blank is kept at 800°C for 1 hour, then heated to Tβ-50°C to Tβ-30°C, kept for 4 to 6 hours, and then repeatedly upsetting and drawing forging is performed for 1 to 2 times, air-cooled after forging, and ground to obtain a third forging blank; The third forging blank is subjected to single-phase forging, the third forging blank is kept at 800°C for 1 hour, then heated to Tβ+50°C to Tβ+100°C, kept for 4 to 6 hours, and then repeatedly upsetting and drawing forged for 1 to 2 times, air-cooled after forging, and ground to obtain a fourth forging blank; The fourth forging blank is subjected to two-phase zone forging, the fourth forging blank is kept at 800°C for 1 hour, then heated to Tβ-60°C to Tβ-30°C, kept for 2.5 to 4 hours, and then repeatedly upsetting and drawing forging is performed for 2 to 6 times to obtain a fifth forging blank; The fifth forging blank is subjected to forming forging, and the fifth forging blank is kept at 800°C for 1 hour and then heated to Tβ-60°C~Tβ-30°C, kept for 2.5~4 hours and then taken out of the furnace, and subjected to drawing and rounding forging, with a total forging ratio ≥3 and a final forging temperature ≥800°C, and annealing heat treatment to obtain the TA18 titanium alloy bar.

2. The method for preparing a highly homogeneous, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The three vacuum consumable melting processes include: ingot element addition values ​​of: Al: 3.0wt.%, V: 2.50wt.%, Fe: 0.2wt.%, O: 0.1wt.%; using sponge titanium, AlV alloy, aluminum particles, titanium-iron alloy, and titanium dioxide to mix and press multiple electrode blocks, TiO2 powder needs to be pre-baked in a baking oven at a temperature above 150°C, and multiple electrode blocks are welded to obtain consumable electrodes, using vacuum plasma welding; after welding the consumable electrode and the auxiliary electrode, three vacuum consumable melting processes are performed, the vacuum degree is ≤1.0Pa, the vacuum leakage rate is ≤1.0Pa / min, the melting current is ≥45kA, and the melting voltage is 15-60V; the shrinkage compensation time is ≥2.5h.

3. The method for preparing a highly homogeneous, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The ingot forging process also includes: an upsetting pressing rate of 20 to 50 mm / s, a reversing drawing process, a drawing process in all directions, a recovery height-to-diameter ratio of 1.75 to 2.2, a forging ratio of each forging fire of ≥2, a start forging temperature of ≥1000°C, and a final forging temperature of ≥950°C.

4. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The reforging of the first forging blank also includes: forging upsetting and drawing both adopt diagonal drawing, the forging ratio of each forging fire is ≥2.6, and the final forging temperature is ≥800°C.

5. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The two-phase zone forging of the second forging blank also includes: the forging ratio of each forging is ≥2.6, and the final forging temperature is ≥800°C.

6. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The single-phase zone forging of the third forging blank also includes: the deformation amount of each forging is 20-30%, and the final forging temperature is ≥850°C.

7. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The two-phase zone forging of the fourth forging blank also includes: diagonal drawing and reversing drawing are performed alternately, the forging ratio of each forging is ≥2.6, the total forging ratio is ≥10, and the final forging temperature is ≥800°C.

8. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The ingot consists of the following elements Composition: Al: 2.5~3.5wt.%, V: 1.50~3.00wt.%.

9. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The size of the TA18 titanium alloy bar is Φ200-500mm.

10. The method for preparing a high-homogeneity, large-size TA18 titanium alloy bar according to claim 1, characterized in that: The annealing heat treatment comprises: keeping the temperature at 650-800° C. for 4-8 hours, and then air cooling.

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