An efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus

Abstract

The present invention provides an efficient preparation method for a large-size TC18 titanium alloy bar with high strength and high elastic modulus, which belongs to the technical field of titanium alloy bar processing, and comprises the following steps: heating a titanium alloy ingot in a single-phase region, performing multi-directional forging, and then water-cooling; then heating the blank in a two-phase region, and then drawing it with a wide V anvil to equalize the diameter; then returning the hot blank to the furnace and heating it to the single-phase region for recrystallization and homogenization, and then quenching and cooling after being taken out of the furnace; heating the blank in the two-phase region again, and then continuously drawing it to a finished bar with a narrow V anvil after being taken out of the furnace, thereby obtaining a large-size TC18 titanium alloy bar; finally, the bar is subjected to homogenization annealing treatment, thereby obtaining a microstructure with a mixed composition of different morphologies. The present invention can obtain a large-size TC18 titanium alloy bar with high strength and high elastic modulus, and effectively reduce the production cost and processing cycle of the material, and realize the efficient preparation of a large-size TC18 titanium alloy bar with high strength and high elastic modulus.

Description

Technical Field

[0001] The invention relates to the field of titanium alloy materials, and in particular to an efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus, which is particularly suitable for high-end fields such as aviation and aerospace. Background Art

[0002] Titanium alloys are widely used in aerospace, weapons, ocean and high-end industrial fields due to their high specific strength, corrosion resistance, non-magnetic properties, and excellent high and low temperature performance. However, compared with traditional metal materials, the elastic modulus of titanium alloy materials is relatively low (E≈110GPa), which is only about half of that of steel. Therefore, when used in the aviation field to manufacture long-axis structural parts such as aircraft landing gear, due to the low elastic modulus, structural design reinforcement is generally required, which is not conducive to the lightweight design requirements of aircraft structural parts. The improvement of the elastic modulus of titanium alloy materials usually adopts the optimization of alloy composition design, such as adding strengthening elements such as vanadium, molybdenum, niobium, and iron to change the crystal structure and chemical composition of titanium alloys, thereby improving their elastic modulus. However, this will cause unpredictable changes in other major mechanical properties of titanium alloys, and requires repeated trial and error, a long development cycle, and high production costs.

[0003] The present invention is mainly aimed at the TC18 titanium alloy material for aviation that is widely used at home and abroad. On the basis of not changing its main chemical composition, through the innovation of subsequent hot processing + heat treatment process, the original mechanical performance parameters of the TC18 titanium alloy material are maintained without decreasing, and the content of various phases between the primary equiaxed α phase, the secondary coarse lamellar α phase, the secondary fine lamellar nano α phase, the grain boundary α phase and the β matrix is ​​adjusted by changing the microstructure of the TC18 titanium alloy, and the stacking fault energy density of the blank is changed, so as to prepare a titanium alloy microstructure containing nanometer scale to improve its elastic modulus. In addition, the hot processing and heat treatment process adopted by the method can effectively shorten the preparation of traditional TC18 large-size bars by 3 to 5 times, improve the production efficiency of the material by more than 15%, and reduce the production cost of the material by more than 20%. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art (the prior art needs to change the alloy composition to adjust the elastic modulus of the titanium alloy), and provide an efficient preparation method for large-sized TC18 titanium alloy bars with high strength and high elastic modulus. The present invention focuses on an efficient preparation method for titanium alloy bars with high strength and high elastic modulus. On the basis of the original large-sized titanium alloy bar preparation process, the present invention adopts multi-directional forging in the ingot blanking process, recrystallization forging of the intermediate blank, and double V anvil drawing of the finished bar. The finished bar is homogenized and annealed to obtain a mixed structure including primary equiaxed α phase, secondary coarse lamellar α phase, secondary fine lamellar nano α phase, grain boundary α phase, and β matrix, which solves the problem that conventional titanium alloy forging cannot obtain uniform distribution of multiple organizational states, thereby obtaining large-sized TC18 titanium alloy bars with high strength and high elastic modulus, while avoiding the problems of long production process and low production efficiency of conventional large-sized TC18 titanium alloy bars.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is:

[0006] An efficient preparation method for high-strength and high-modulus TC18 titanium alloy large-size bars comprises the following steps:

[0007] Step 1, after peeling and sawing the riser of the TC18 titanium alloy ingot produced by vacuum consumable smelting; after heating the ingot in the single-phase region, the ingot is forged by a 100MN fast forging machine, and multi-directional forging is used for water cooling;

[0008] Step 2, the billet is heated in the two-phase region, and after being taken out of the furnace, a 100MN fast forging machine is used with a wide V anvil to draw the billet with equal diameters, and then the hot billet is immediately returned to the furnace and heated to the single-phase region with the furnace for recrystallization and homogenization, and then taken out of the furnace and transferred to quenching heavy oil for cooling;

[0009] Step 3: The blank is heated in the two-phase region, and after being taken out of the furnace, it is continuously drawn to the finished product size using a narrow double V anvil, thereby obtaining a uniform high and low magnification structure. Large-size titanium alloy bars;

[0010] Step 4, subjecting the large-size titanium alloy rod to homogenization annealing treatment, so as to obtain a microstructure with uniform distribution of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano α phase, grain boundary α phase, and β matrix.

[0011] Furthermore, when the ingot is heated in step 1, the heating temperature of the ingot is T β +(200~350)℃, holding time is (0.6~1.0)*D min, T β is the alloy phase transition temperature ℃, D is the ingot diameter mm.

[0012] Furthermore, when the ingot is forged in step 1, multi-directional forging is adopted, that is, one axial upsetting is performed in each of the three directions of X, Y and Z of the ingot, the upsetting deformation in each direction is controlled at 20-40%, the deformation in each direction is the same, and the total forging ratio of the ingot forging is 3.5-5.0.

[0013] Furthermore, when the two-phase region of the blank is heated in step 2, the heating temperature is T β -(30~50)℃, the holding time is (0.6~1.0)*T1 min, T1 is the billet thickness in mm; the wide V anvil for equal-diameter drawing after heating is an upper and lower double V anvil, and the effective width dimension of the V anvil is 400~500mm, and the forging ratio of equal-diameter drawing is 1.5~2.5.

[0014] Furthermore, in step 2, the hot material of the billet is returned to the furnace and heated with the furnace to a single-phase region for recrystallization homogenization, and the heating temperature is T β +(60~100)℃, holding time is (0.3~0.5)*T2 min, T2 is the billet thickness in mm; the billet is cooled by quenching heavy oil with an oil temperature of 80-150℃.

[0015] Furthermore, after the multi-directional forging of the ingot in step 1 and the recrystallization of the billet in step 2 are completed, the transfer time of the billet using water cooling and oil cooling is ≤60s.

[0016] Furthermore, when the two-phase region of the blank is heated in step 3, the heating temperature is T β -(30~50)℃, holding time is (0.6~1.0)*T3 min, T3 is the billet thickness mm; narrow double V anvil is used for continuous drawing, the effective width of narrow V anvil is 200~300mm, the drawing fire is 1~3 times according to the finished bar specifications, the total forging ratio of drawing is 1.2~4.0, the hot material is returned to the furnace after each drawing fire, and the heating temperature of the billet is T β -(30~50)℃, holding time is (0.3~0.5)*T4 min, T4 is the thickness of the hot material returned to the furnace in mm.

[0017] Furthermore, in step 4, the large-size titanium alloy bar is subjected to homogenization annealing treatment, and the homogenization annealing system is: T β +(10~20)℃ keep warm for 60~90min and cool to T β -(10~20)℃ keep warm for 120-180min, air cool; heat again to T β -(250~350)℃ insulation for 240-360min, air cooling; furnace cooling rate is 1~3℃ / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] From the perspective of uniform deformation of materials, multi-directional forging is adopted in the ingot forging stage to fully crush and refine the coarse ingot structure and obtain a basically uniform structure in three directions; secondly, wide V anvil is used for drawing in the two-phase region to further refine the structure while maintaining the uniformity of the structure, and then the temperature is raised to the single-phase region for recrystallization to obtain a more uniform single-phase region structure, and oil cooling is used to obtain a stable high dislocation density uniform single-phase region structure; finally, in the finished product drawing stage, narrow double V anvils are used for multi-fire drawing to the finished bar, further refining the billet structure and maintaining the uniformity of the low-magnification structure. This forging method simplifies the forging production process of traditional TC18 titanium alloy large-size bars, reduces the forging fire by 3 to 5 times, and can effectively ensure the uniformity of the finished bar structure and the consistency of performance; and after the finished bar is subjected to homogenization annealing, a mixed structure with uniform distribution of different α phase morphology and content can be obtained, and finally the high-strength and high-elastic modulus TC18 titanium alloy large-size bars can be prepared efficiently.

[0020] Other features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a schematic diagram of the multi-directional forging of the present invention.

[0023] Figure 2 It is a schematic structural diagram of the double V-anvil extension device of the present invention.

[0024] Figure 3 This is the low-magnification structure diagram of the Φ350mm rod prepared in Example 1.

[0025] Figure 4 This is the high-magnification microstructure diagram of the Φ350mm rod prepared in Example 1.

[0026] Figure 5 This is the low-magnification structure diagram of the Φ400mm rod prepared in Example 2.

[0027] Figure 6 This is the high-magnification microstructure diagram of the Φ400mm rod prepared in Example 2.

[0028] Figure 7 This is the low-magnification microstructure diagram of the Φ500mm rod prepared in Example 3.

[0029] Figure 8 This is the high-magnification microstructure diagram of the Φ500mm rod prepared in Example 3. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Example 1

[0032] An efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus, comprising the following steps:

[0033] Step 1, the raw materials (sponge titanium, Al-60Mo alloy, Al-65V alloy, metal Cr, Ti-32Fe alloy, etc.) are mixed evenly by a mixing machine, pressed into a full-circle electrode block, and then welded into an integral electrode in a vacuum welding box, and then three VAR smeltings are performed in a vacuum consumable melting furnace to obtain a 3-ton TC18 titanium alloy ingot with a specification of φ650mm, and the skinning and riser cutting are performed; the ingot is heated at 1100°C and kept warm for 420min, and then a 100MN fast forging machine is used for blank forging, multi-directional forging is used, and one upsetting is performed in each of the three directions. After forging, the specification is 600mm square, the upsetting deformation in each direction is 39.5%, the total forging ratio is 4.95, and water cooling is performed immediately after forging, and the transfer time is 40 seconds;

[0034] Step 2, reheat the titanium alloy billet after the billeting in step 1 to 820°C, and keep it at this temperature for 480 minutes, then use a 100MN fast forging machine with an effective size of 400mm wide double V anvil to draw it in equal diameters, and the drawing ratio is 1.5. After forging, the specification is 490mm square, and then the hot billet is returned to the furnace and heated to 970°C with the furnace for 200 minutes for recrystallization homogenization treatment, and then it is taken out of the furnace and transferred to the quenching oil for cooling, the transfer time is 40 seconds, and the oil temperature of the quenching oil is 150°C;

[0035] Step 3: The intermediate billet forged in step 2 is heated at 820°C for 380 minutes. After being taken out of the furnace, it is continuously drawn and rolled to a length of 3 times using a narrow double V anvil with an effective size of 200 mm. Finished blank, drawing length total forging ratio 2.4, thus obtaining a finished product with uniform high and low magnification structure TC18 titanium alloy large-size bars;

[0036] Step 4, the TC18 finished blank bar obtained by forging in step 3 is subjected to homogenization annealing treatment, and the heat treatment system is: 880°C for 60min furnace cooling (cooling rate 3°C / min) to 860°C for 180min, air cooling + 520°C for 360min, air cooling; thereby obtaining a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano α phase, grain boundary α phase and β matrix.

[0037] High-strength and high-elastic modulus TC18 titanium alloy in Example 1 The macrostructure of the rod is as follows Figure 3 As shown, the low-magnification structure of the rod shows fine, uniform fuzzy crystals, and the low-magnification structure is uniform; Figure 4 It is the high-magnification structure of different positions (edge, D / 4, and core) of the rod. It is a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano-α phase, grain boundary α phase and β matrix. The mechanical properties results are shown in Table 1.

[0038] Example 2

[0039] An efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus, comprising the following steps:

[0040] Step 1, the raw materials (sponge titanium, Al-60Mo alloy, Al-65V alloy, metal Cr, Ti-32Fe alloy, etc.) are mixed evenly by a mixing machine, pressed into a full-circle electrode block, and then welded into an integral electrode in a vacuum welding box, and then smelted in a vacuum consumable melting furnace by three times of VAR to obtain a 5-ton TC18 titanium alloy ingot with a specification of φ720mm, and the skinning and riser cutting are performed; the ingot is heated at 1150°C and kept warm for 700min, and then a 100MN fast forging machine is used for blank forging, multi-directional forging is used, and one upsetting is performed in each of the three directions. After forging, the specification is 680mm square, the upsetting deformation in each direction is 33.3%, the total forging ratio is 4.5, and water cooling is performed immediately after forging, and the transfer time is 45 seconds;

[0041] Step 2, reheat the titanium alloy billet after the billeting in step 1 to 840°C, and keep it at this temperature for 420 minutes, then use a 100MN fast forging machine with an effective size of 500mm wide double V anvil to draw it in equal diameters, and the drawing ratio is 2.1. After forging, the specification is 470mm square, and then immediately return the hot billet to the furnace and heat it to 950°C with the furnace for 210 minutes for recrystallization homogenization treatment, and then take it out of the furnace and transfer it to the quenching oil for cooling, the transfer time is 45 seconds, and the oil temperature of the quenching oil is 100°C;

[0042] Step 3: Heat the intermediate billet forged in step 2 at 840°C for 340 minutes. After it is taken out of the furnace, it is continuously drawn and rolled to a length of 200 mm using a narrow double V anvil. Finished blank, the total forging ratio of drawing is 1.7, so as to obtain a finished product with uniform high and low magnification structure TC18 titanium alloy large-size bars;

[0043] Step 4: Forge the The finished blank rods were subjected to homogenization annealing treatment, and the heat treatment system was as follows: heating to 890°C and holding for 90 min, furnace cooling (cooling rate 2°C / min) to 860°C and holding for 120 min, air cooling + heating again to 570°C and holding for 300 min, air cooling; thereby obtaining a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano-α phase, grain boundary α phase and β matrix.

[0044] High-strength and high-modulus TC18 titanium alloy in Example 2 The high and low magnification structures of the rods are as follows Figure 5 As shown, the low-magnification structure of the rod shows fine, uniform fuzzy crystals, and the low-magnification structure is uniform; Figure 6 It is the high-magnification structure of different positions (edge, D / 4, and core) of the rod. It is a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano-α phase, grain boundary α phase and β matrix. The mechanical properties results are shown in Table 1.

[0045] Example 3

[0046] An efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus, comprising the following steps:

[0047] Step 1, the raw materials (sponge titanium, Al-60Mo alloy, Al-65V alloy, metal Cr, Ti-32Fe alloy, etc.) are mixed evenly by a mixing machine, pressed into a full-circle electrode block, and then welded into an integral electrode in a vacuum welding box, and then 6 tons of TC18 titanium alloy ingots with a specification of φ780mm are obtained by three VAR smeltings in a vacuum consumable melting furnace, and the skinning and riser cutting are performed; the ingot is heated at 1180°C and kept warm for 780min, and then a 100MN fast forging machine is used for blank forging, multi-directional forging is used, and one upsetting is performed in each of the three directions. After forging, the specification is 740mm square, the upsetting deformation in each direction is 23%, the total forging ratio is 3.9, and water cooling is performed immediately after forging, and the transfer time is 50 seconds;

[0048] Step 2, reheat the titanium alloy billet after the billeting in step 1 to 840°C, and keep it at this temperature for 600 minutes, then use a 100MN fast forging machine with an effective size of 500mm wide double V anvil to draw it in equal diameters, and the drawing ratio is 2.0. After the forging is completed, the specification is 520mm square, and then immediately return the hot billet to the furnace and heat it to 930°C with the furnace for 260 minutes for recrystallization homogenization treatment, and then take it out of the furnace and transfer it to the quenching oil for cooling, the transfer time is 50 seconds, and the oil temperature of the quenching oil is 80°C;

[0049] Step 3: Heat the intermediate billet forged in step 2 at 840°C for 420 minutes. After it is taken out of the furnace, it is drawn and rolled once using a narrow double V anvil with an effective size of 200 mm. Finished blank, the total forging ratio of drawing is 1.3, so as to obtain a finished product with uniform high and low magnification structure TC18 titanium alloy large-size bars;

[0050] Step 4: Forge the The finished blank rods were subjected to homogenization annealing treatment, and the heat treatment system was as follows: heating to 890°C and holding for 90 min, furnace cooling (cooling rate 1°C / min) to 860°C and holding for 180 min, and air cooling; heating to 620°C and holding for 240 min, and air cooling; thereby obtaining a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano-α phase, grain boundary α phase and β matrix.

[0051] High-strength and high-modulus TC18 titanium alloy in Example 3 The high and low magnification structures of the rods are as follows Figure 7 As shown, the low-magnification structure of the rod shows fine, uniform fuzzy crystals, and the low-magnification structure is uniform; Figure 8 The high-magnification structure at different positions of the rod (edge, D / 4, and core) is a microstructure composed of different morphologies such as primary equiaxed α phase, large lamellar α phase, fine lamellar nano-α phase, grain boundary α phase, and β matrix. The mechanical properties results are shown in Table 1.

[0052] Table 1 TC18 large-size bar tangential D / 4 room temperature tensile properties

[0053]

[0054]

[0055] It can be seen from Table 1 that the room temperature tensile strength of TC18 large bars of different specifications obtained in Examples 1 to 3 is significantly better than that of the conventional production process, and the elastic modulus of the bars is about 10% higher than that of the conventional process. The production number of fires is reduced by 3 to 5 times compared with the traditional process, and the production efficiency is increased by more than 15%.

[0056] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An efficient preparation method for large-size TC18 titanium alloy bars with high strength and high elastic modulus, characterized in that: The following steps are involved: Step 1, after peeling and sawing the riser of the TC18 titanium alloy ingot produced by vacuum consumable smelting; after heating the ingot in the single-phase region, the ingot is forged by a 100MN fast forging machine, and then water-cooled after multi-directional forging; Step 2, the billet is heated in the two-phase region, and after being taken out of the furnace, a 100MN fast forging machine is used with a wide V anvil to draw the billet with equal diameters, and then the hot billet is immediately returned to the furnace and heated to the single-phase region with the furnace for recrystallization and homogenization, and then taken out of the furnace and transferred to quenching heavy oil for cooling; Step 3: The blank is heated in the two-phase region, and after being taken out of the furnace, it is continuously drawn to the finished product size using a narrow double V anvil, thereby obtaining a uniform high and low magnification structure. Large-size titanium alloy bars; Step 4, subjecting the large-size titanium alloy rod to homogenization annealing treatment, thereby obtaining a microstructure composed of a mixture of different morphologies such as primary equiaxed α phase, coarse lamellar α phase, fine lamellar nano α phase, grain boundary α phase and β matrix.

2. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: Step 1: When the ingot is heated, the heating temperature is T β +(200~350)℃, holding time is (0.6~1.0)*Dmin, T β is the alloy phase transition temperature ℃, D is the ingot diameter mm.

3. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: Step 1: When the ingot is forged, multi-directional forging is adopted, that is, one axial upsetting is performed in each of the three directions of X, Y and Z of the ingot, and the upsetting deformation in each direction is controlled at 20-40%. The deformation of upsetting in each direction is the same, and the total forging ratio of the ingot forging is 3.5-5.

0.

4. The efficient preparation method of the high-strength and high-elastic modulus TC18 titanium alloy large-size bar according to claim 1 is characterized in that: When the two-phase region of the billet is heated in step 2, the heating temperature is T β -(30~50)℃, the holding time is (0.6~1.0)*T1 min, T1 is the billet thickness in mm; the wide V anvil for equal-diameter drawing after heating is an upper and lower double V anvil, and the effective width dimension of the V anvil is 400~500mm, and the forging ratio of equal-diameter drawing is 1.5~2.

5.

5. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: In step 2, the hot material of the billet is returned to the furnace and heated with the furnace to the single-phase region for recrystallization and homogenization. The heating temperature is T β +(60~100)℃, holding time is (0.3~0.5)*T2 min, T2 is the thickness of the blank in mm.

6. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: The blank is cooled by quenching heavy oil at an oil temperature of 80-150℃.

7. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: After the multi-directional forging of the ingot in step 1 and the recrystallization of the billet in step 2 are completed, the transfer time of the billet using water cooling and oil cooling is ≤60s.

8. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: When the two-phase region of the billet is heated in step 3, the heating temperature is T β -(30~50)℃, holding time is (0.6~1.0)*T3 min, T3 is the billet thickness mm; narrow double V anvil is used for continuous drawing, the effective width of narrow V anvil is 200~300mm, the drawing fire is 1~3 times according to the finished bar specifications, the total forging ratio of drawing is 1.2~4.0, after each drawing fire, the hot material is returned to the furnace, and the heating temperature is T β -(30~50)℃, holding time is (0.3~0.5)*T4 min, T4 is the thickness of the hot material returned to the furnace in mm.

9. The efficient preparation method of large-size TC18 titanium alloy bars with high strength and high elastic modulus according to claim 1 is characterized in that: In step 4, the large-size titanium alloy bar is subjected to homogenization annealing treatment, and the homogenization annealing system is: T β +(10~20)℃, keep warm for 60~90min, cool to T β -(10~20)℃ keep warm for 120-180min, air cool; heat again to T β -(250~350)℃ insulation for 240-360min, air cooling; furnace cooling rate is 1~3℃ / min.

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