A method for preparing a large-size integral blisk forging made of Ti175 alloy

Abstract

A method for preparing a Ti175 alloy large-size integral blade forging belongs to the field of titanium and titanium alloy processing, and the specific steps are: 1) billet reforging: the bar is subjected to T β 45-60℃ below the phase transformation point for 2-5 times of upsetting and drawing deformation, requiring at least 2 times of deformation, the single upsetting deformation of the fire is not less than 50%, and the forging ratio is not less than 4, and the final forging temperature is not less than 850℃; 2) Die forging: at T β Die forging at 40℃~50℃ below the phase transformation point, air cooling after forging to obtain die forging blank; 3) triple heat treatment: solution treatment: keep warm at 10℃~30℃ below the β transformation temperature for 1~4h, air cooling or cooling at a faster rate; secondary solution treatment: keep warm at 65℃~85℃ below the β transformation temperature for 1~5h, air cooling or cooling at a faster rate; aging treatment: 530℃~650℃, 2~10h, air cooling. The present invention makes the original β grains in the forging structure have the characteristics of the original β grains in the forging structure by matching the reform forging and die forging. <100> The wire texture is parallel to the compression direction. The content and morphology of each phase of the alloy are adjusted through triple heat treatment, giving the forging excellent strength, plasticity and fracture toughness.

Description

Technical Field

[0001] The invention belongs to the field of titanium and titanium alloy processing, and particularly relates to a method for preparing a large-size integral blisk forging made of Ti175 alloy. Background Art

[0002] High-temperature titanium alloys, primarily composed of α phase (hexagonal close-packed) and a small amount of β phase (body-centered cubic), are widely used in aerospace applications due to their excellent high-temperature creep, fatigue, and corrosion resistance. Microstructure and texture are the two most important factors influencing the mechanical properties of alloys. The hexagonal close-packed α phase exhibits strong anisotropy, making its mechanical properties sensitive to texture. While much research has been conducted on the control of titanium alloy microstructure, research on how to improve forging performance by controlling forging texture is lacking.

[0003] The rapid development of fields such as aerospace has led to increasingly stringent requirements for material properties such as specific strength, specific stiffness and temperature resistance. Relying solely on the regulation of alloy structure has gradually failed to meet the higher demands of "enhancement" and "weight reduction" required by the design of new-generation aircraft engines. Based on the understanding of the role of thermal processing in the evolution of the structure and texture of high-temperature titanium alloys, improving the comprehensive mechanical properties of materials through the comprehensive matching of texture and organization is a possible way to further explore the performance of alloys. To this end, the present invention proposes a method for preparing large-size integral blade forgings of Ti175 alloy, which makes the original β grains of the alloy have <100> Texture, improve the alloy's plasticity and performance stability, and combined with a special heat treatment process to obtain a three-state structure to achieve a simultaneous improvement in the strength and plasticity of the forging. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a large-sized integral blisk forging of Ti175 alloy, wherein the original β grains of the forging prepared by the method have strong <100> The alloy structure is a mixed structure consisting of primary α phase, coarse lath bundles, secondary α fine laths and residual β phase. The forgings can be used for a long time at a temperature of 500-600°C and have excellent thermal strength and stability. This method is suitable for the preparation of high-temperature rotating parts for aviation and aerospace fields.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a Ti175 alloy large-size integral blisk forging includes the following steps:

[0007] 1) Billet forging: The bar is forged at T βThe steel is subjected to 2 to 5 upsetting and drawing deformations at 45 to 60°C below the phase transformation point. The upsetting deformation of at least 2 of the upsetting deformations is required to be not less than 50%, the forging ratio is not less than 4, and the final forging temperature is not less than 850°C.

[0008] 2) Die forging: Die forging the blank in T β The die forging is performed at 40°C to 50°C below the phase transformation point, and air-cooled after forging to obtain a die forging blank.

[0009] 3) Heat treatment: The die forging blank obtained in step 2) is subjected to triple heat treatment, specifically:

[0010] The first stage is solution treatment, specifically: keeping the temperature at 10℃~30℃ below the β-transus temperature for 1~4 hours, and cooling by air or faster cooling method;

[0011] The second stage is secondary solution treatment, specifically: keeping at 65℃~85℃ below the β-transus temperature for 1~5h, air cooling or faster cooling method;

[0012] The third stage is aging treatment, specifically: keeping warm at 530℃~650℃ for 2~10h, and air cooling.

[0013] Preferably, in step 1), the rod used for billet reforging is repeatedly deformed in the alloy two-phase region, and the structure of the rod is a uniform bimodal or equiaxed structure.

[0014] Preferably, in step 1), the deformation amount of the upsetting in a single fire of at least two fires is required to be not less than 50% and less than or equal to 70%.

[0015] Preferably, in step 2), the die forging is performed using an isothermal or near-isothermal die forging process, the die is heated and kept warm in the range of 50°C below the billet heating temperature to the billet heating temperature, and the deformation rate is 0.01s -1 ~0.015s -1 ; Or adopt hot die forging process, the die is heated to 400-600℃, and the deformation rate is 0.01s -1 ~0.02s -1 The surface of the blank is covered with asbestos to reduce heat loss during deformation.

[0016] Preferably, in the heat treatment process described in step 3), the first solution treatment system is: 15-25°C below the β-transus temperature, holding for 2 hours, and oil cooling; the second secondary solution treatment system is: 70-80°C below the β-transus temperature, holding for 3-5 hours, and air cooling; the third aging treatment system is: 540°C, 6-8 hours, and air cooling.

[0017] The Ti175 alloy of the present invention comprises (by weight percentage) 6.2% to 7.50% Al, 3.0% to 4.0% Zr, 1.50% to 3.0% Sn, 3.50% to 4.5% Mo, 0.15% to 0.35% Si, and 0.9% to 2.0% W, with the remainder being Ti and unavoidable impurity elements. The contents of W and Mo satisfy the following conditions: W ≥ Mo / 4 and 2.8% ≤ Mo / 2 + W ≤ 3.2%. The contents of the alloying elements Zr and Si satisfy an inverse relationship and the following conditions: -Zr / 20 + 0.35% ≤ Si ≤ -Zr / 20 + 0.4%.

[0018] The present invention takes into account the composition characteristics and organizational evolution law of the alloy and gives full play to the composite strengthening effect of texture and organization to ensure that the forging has excellent strength and toughness from room temperature to 600°C.

[0019] The beneficial effects of the present invention are:

[0020] 1) By matching the reforming and die forging processes, the original β grains in the forging structure have <100> Silk texture parallel to the compression direction.

[0021] 2) The forgings are finally subjected to a triple heat treatment process to adjust the content and morphology of each alloy phase, giving the forgings excellent strength, plasticity and fracture toughness.

[0022] 3) The diameter of the prepared forging is 600 to 1300 mm, the height is not less than 100 mm, and the maximum single weight can reach 400 kg.

[0023] 4) The room temperature tensile strength of the forging shall not be less than 1200Mpa, the yield strength shall not be less than 1050Mpa, the elongation shall not be less than 12%, and the area reduction shall not be less than 15%. The room temperature fracture toughness of the alloy shall not be less than 55Mpa·m 1 / 2 , 550℃ tensile strength is not less than 810Mpa, yield is not less than 650Mpa, elongation is not less than 12%, and area shrinkage is not less than 35%. 600℃ tensile strength is not less than 750Mpa, yield is not less than 580Mpa, elongation is not less than 20%, and area shrinkage is not less than 60%.

[0024] The present invention will be further described below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the high-magnification microstructure and original β grain inverse pole figure of the Ti175 alloy large-sized integral disk forging prepared in Example 1 of the present invention.

[0026] Figure 2 This is the high-magnification microstructure and original β grain inverse pole figure of the Ti175 alloy large-sized integral disk forging prepared in Example 2 of the present invention.

[0027] Figure 3 This is the high-magnification microstructure and original β grain inverse pole figure of the Ti175 alloy large-sized integral disk forging prepared in Example 3 of the present invention.

[0028] Figure 4 This is the high-magnification microstructure and original β grain inverse pole figure of the Ti175 alloy large-sized integral disk forging prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0029] Example 1:

[0030] The Ti175 alloy bar with a specification of Ф450×1000mm is used. The chemical composition of the bar is Al: 6.50%, Zr: 3.5%, Sn: 2.1%, Mo: 3.5%, Si: 0.175%, W: 1.3%, and the balance is Ti and unavoidable impurity elements, T β The phase transition point is 982°C, and the original structure of the bar is an equiaxed structure obtained by forging in the two-phase region. The preparation method of the Ti175 alloy large-size integral blisk forging is as follows:

[0031] 1) Billet forging:

[0032] First heat: The bar is heated to 930℃ and then subjected to a 4500-ton press to complete a first upsetting and a second drawing process. The upsetting deformation is 60%, and then drawn to a length with a total forging ratio of 4.8. After air cooling, it is ground.

[0033] Second fire: The bar is heated to 930℃ and then subjected to upsetting and drawing in a 4500-ton press. The upsetting deformation is 55%, and then drawn to a length with a total forging ratio of 4.4. After air cooling, it is ground.

[0034] The third heat: the bar is heated to 930℃, and then subjected to a 4500-ton press to complete a first upsetting and a second drawing process. The deformation of the upsetting process is 45%, and the final drawing process is lengthened. The total forging ratio is 3.6. After air cooling, the bar is ground.

[0035] Fourth fire: heat the bar to 930℃, perform upsetting deformation in a 4500-ton press, upset and shape the blank to Ф900×250mm, air-cool and then perform grinding.

[0036] 2) Die forging: The forging blank is heated to 935℃ for die forging. The die forging adopts a near isothermal die forging process. The holding temperature of the die after heating is 935℃, and the deformation rate of the die forging is 0.011s -1 After forging, it is air-cooled to obtain a die forging billet with an appearance size of Ф1150×150mm.

[0037] 3) Heat treatment: The die forging blank is subjected to triple heat treatment:

[0038] Primary solution treatment system: 965℃, hold for 2h, oil cooling;

[0039] Secondary solution treatment system: 907℃, hold for 4h, air cooling;

[0040] Aging treatment: 540℃, 8h, air cooling.

[0041] Example 2

[0042] The difference between Example 2 and Example 1 lies in the way the billet is forged. The amount of upsetting deformation per fire in Example 2 is lower than that in Example 1, in order to weaken the alloy. <100> The raw materials, die forging and heat treatment system used in Example 2 are the same as those in Example 1. The modified forging process of Example 2 is as follows:

[0043] First heat: The bar is heated to 930℃ and then subjected to a 4500-ton press to complete a first upsetting and a second drawing process, with the upsetting deformation being 40%. The bar is then slightly drawn with a total forging ratio of 2.5. The bar is then air-cooled and then ground.

[0044] Second fire: The bar is heated to 930℃ and then subjected to a 4500-ton press to complete a first upsetting and a second drawing process. The upsetting deformation is 40%, and then the bar is drawn to a length with a total forging ratio of 3.2. The bar is then air-cooled and then ground.

[0045] The third fire: the bar is heated to 930℃ and upsetting is completed in a 4500-ton press. The upsetting deformation is such that the height of the forging blank after shaping is 450mm and the total forging ratio is 3.8. After air cooling, it is ground.

[0046] Fourth fire: heat the bar to 930℃, perform upsetting deformation in a 4500-ton press, upset and shape the billet to Ф900×250mm, with a total forging ratio of 1.8, and then perform grinding after air cooling.

[0047] Example 3

[0048] The reforming and die forging processes of Example 3 are the same as those of Example 1. The difference is that the heat treatment system of Example 3 is a double heat treatment. The specific process is as follows:

[0049] Solution treatment system: 965℃, hold for 2h, air cooling;

[0050] Aging treatment: 540℃, 8h, air cooling.

[0051] Table 1 is a performance comparison of Examples 1 to 3. Combining the texture and microstructure of the three processes, it can be seen that Examples 1 and 2 are both tri-state structures, and Example 3 is a bi-state structure. Examples 1 and 3 have stronger <100> The texture of Example 1 is excellent, but the texture of Example 2 is weak. Example 1 has excellent comprehensive performance. The main difference between Example 2 and Example 1 is that the plasticity and fracture toughness of the alloy are lower than those of Example 1, which verifies that the β phase <100> The strength of the dual-state alloy in Example 3 is much lower than that in Examples 1 and 2. The comparison shows that the simultaneous improvement of the strength and plasticity of the alloy can be achieved through the coordinated control of the forging texture and structure.

[0052] Table 1 Tensile properties of Ti175 alloy large-size integral blisk forgings in the embodiment

[0053]

[0054] Example 4:

[0055] The alloy bar with the specification of Ф450×1000mm is used. The chemical composition of the bar is Al: 6.55%, Zr: 4.5%, Sn: 2.1%, Mo: 4.0%, Si: 0.25%, W: 0.9%, and the balance is Ti and unavoidable impurity elements, T β The phase transition point is 985°C, and the original microstructure of the bar is an equiaxed microstructure obtained by forging from a two-phase region. This alloy composition does not meet the composition requirements of W ≥ Mo / 4 and -Zr / 20+0.35% ≤ Si ≤ -Zr / 20+0.4%. The preparation process of the alloy is the same as that of Example 1, and the specific preparation method is as follows:

[0056] 1) Billet forging:

[0057] First heat: The bar is heated to 933℃ and then subjected to upsetting and drawing in a 4500-ton press. The upsetting deformation is 60%, and then drawn to length. The total forging ratio is 4.8. After air cooling, it is ground.

[0058] Second fire: The bar is heated to 933℃ and then subjected to upsetting and drawing in a 4500-ton press. The upsetting deformation is 55%, and then drawn to length. The total forging ratio is 4.4. After air cooling, it is ground.

[0059] The third heat: the bar is heated to 933℃, and then subjected to a 4500-ton press to complete a first upsetting and a second drawing process. The deformation of the upsetting process is 45%, and the final drawing process is lengthened. The total forging ratio is 3.6. After air cooling, the bar is ground.

[0060] Fourth fire: heat the bar to 933℃, perform upsetting deformation in a 4500-ton press, upset and shape the blank to Ф900×250mm, air-cool and then perform grinding.

[0061] 2) Die forging: The forging blank is heated to 938℃ for die forging. The die forging adopts a near isothermal die forging process. The holding temperature of the die after heating is 930℃, and the deformation rate of the die forging is 0.011s -1 After forging, it is air-cooled to obtain a die forging billet with an appearance size of Ф1150×150mm.

[0062] 3) Heat treatment: The die forging blank is subjected to triple heat treatment:

[0063] Primary solution treatment system: 968℃, hold for 2h, oil cooling;

[0064] Secondary solution treatment system: 910℃, hold for 4h, air cooling;

[0065] Aging treatment: 540℃, 8h, air cooling.

[0066] Table 2 shows the properties of the alloy of Example 4. The strength and ductility of the alloy of Example 4 at room temperature and 550°C are comparable to those of Example 1, but the high-temperature strength at 600°C is significantly lower than that of Example 1.

[0067] Table 2 Tensile properties of Ti175 alloy large-size integral blisk forgings in Example 4

[0068]

[0069] Matters not covered by the present invention are known technologies.

[0070] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a large-sized integral blisk forging made of Ti175 alloy, characterized in that: The specific steps are as follows: 1) Billet forging: The bar is forged at T β The temperature is 45-60℃ below the phase transformation point, and the upsetting and drawing deformation is carried out for 2-5 times. The upsetting deformation of at least 2 times is required to be not less than 50%, and the forging ratio is not less than 4. The final forging temperature is not less than 850℃. 2) Die forging: Die forging the blank in T β Die forging is performed at 40℃~50℃ below the phase transformation point, and air cooling is performed after forging to obtain the die forging blank; 3) Heat treatment: The die forging blank obtained in step 2) is subjected to triple heat treatment, specifically: Solution treatment: keep at 10℃~30℃ below the β transformation temperature for 1~4h, then cool with air or at a faster rate; Secondary solution treatment: keep at 65℃~85℃ below the β-transus temperature for 1~5h, then air cool or cool at a faster rate; Aging treatment: keep warm at 530℃~650℃ for 2~10h, air cool.

2. The method for preparing a large-sized Ti175 alloy blisk forging according to claim 1, characterized in that: In step 1), the rod used for billet reforging is repeatedly deformed in the alloy two-phase region, and the structure of the rod is a uniform bimodal or equiaxed structure.

3. The method for preparing a large-sized Ti175 alloy blisk forging according to claim 1, characterized in that: In step 1), the deformation of the single-fire upsetting of at least two fires is required to be no less than 50% and less than or equal to 70%.

4. The method for preparing a large-sized Ti175 alloy blisk forging according to claim 1, characterized in that: In step 2), the die forging is performed by an isothermal or near-isothermal die forging process, the die is heated and kept warm in the range of 50°C below the billet heating temperature to the billet heating temperature, and the deformation rate is 0.01s -1 ~0.015s -1 ; Or adopt hot die forging process, the die is heated to 400-600℃, and the deformation rate is 0.01s -1 ~0.02s -1 , the surface of the blank is covered with asbestos.

5. The method for preparing a Ti175 alloy large-size blisk forging according to claim 1, characterized in that: In step 3), the triple heat treatment is: Solution treatment: keep at 15-25℃ below the β transformation temperature for 2h, oil cooling; Secondary solution treatment: keep at 70-80℃ below the β transformation temperature for 3-5h, then air cool; Aging treatment: keep warm at 540℃ for 6-8h, then air cool.

6. The method for preparing a Ti175 alloy large-size integral blisk forging according to claim 1, characterized in that: The Ti175 alloy comprises the following components by weight: Al: 6.2% to 7.50%, Zr: 3.0% to 4.0%, Sn: 1.50% to 3.0%, Mo: 3.50% to 4.5%, Si: 0.15% to 0.35%, W: 0.9% to 2.0%, and the remainder being Ti and unavoidable impurity elements.

7. The method for preparing a Ti175 alloy large-size blisk forging according to claim 6, characterized in that: In the Ti175 alloy, the contents of the elements W and Mo satisfy: W≥Mo / 4 and 2.8%≤Mo / 2+W≤3.2%; the contents of the alloying elements Zr and Si satisfy an inverse relationship and satisfy: -Zr / 20+0.35%≤Si≤-Zr / 20+0.4%.

8. A Ti175 alloy large-size integral blisk forging produced by the method of claim 1, characterized in that: The diameter of the forging is 600-1300 mm, and the height is not less than 100 mm.

9. The Ti175 alloy large-size integral blisk forging according to claim 8, characterized in that: The forging is a mixed structure consisting of primary α phase, coarse lath bundles, secondary α fine laths and residual β phase; the original β grains in the forging structure have <100> Silk texture parallel to the compression direction.

10. The Ti175 alloy large-size integral blisk forging according to claim 8, characterized in that: The room temperature tensile strength of the forging is not less than 1200 MPa, the yield strength is not less than 1050 MPa, the elongation is not less than 12%, and the area reduction is not less than 15%; the room temperature fracture toughness of the alloy is not less than 55 MPa·m 1 / 2 , 550℃ tensile strength is not less than 810Mpa, yield strength is not less than 650Mpa, elongation is not less than 12%, and area shrinkage is not less than 35%; 600℃ tensile strength is not less than 750Mpa, yield strength is not less than 580Mpa, elongation is not less than 20%, and area shrinkage is not less than 60%.

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