A method for manufacturing large-size Ti2AlNb rings with high fracture toughness and low anisotropy

Abstract

The present invention belongs to the field of titanium and titanium alloy processing, and specifically provides a method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy, which is characterized by comprising the following steps: 1) heating the blank: heating the Ti2AlNb ring blank prepared in the two-phase region or the three-phase region to T β 1) Forming: After being heated through to 40°C to 120°C above the transformation temperature, the ring blank is held for 1-4 hours before being removed from the furnace. 2) Forming: After being removed from the furnace, the ring blank is quickly transferred to a press for upsetting to the process height, then quickly transferred to a ring rolling mill for expansion to the process size. 3) Heat Treatment: The ring is held at 900-1030°C, then cooled, and then air-cooled at 760-850°C to obtain large-sized Ti2AlNb titanium alloy rings with a basketweave structure. This process produces products with a basketweave structure, with minimal variations in the tangential, radial, and axial directions, making it suitable for the production of large-sized rings for aerospace applications.

Description

Technical Field

[0001] The invention belongs to the field of titanium and titanium alloy processing, and in particular provides a method for manufacturing a large-size Ti2AlNb ring with high fracture toughness and low anisotropy. Background Art

[0002] Ti2AlNb alloy has significant advantages such as high specific strength, low thermal expansion coefficient, and high specific modulus. It is used in the aerospace field as an alternative material to replace some high-temperature alloys to achieve structural weight reduction. The material has outstanding performance advantages at 650-800°C, but the alloy has prominent problems such as low intrinsic plasticity and poor fracture toughness, which limit the application of the alloy.

[0003] At present, the forming of large-sized rings in the β phase region generally adopts the method of single-fire ring rolling in the β phase region. For example, the patent "A method for manufacturing large-sized rings of titanium alloy with basket structure" (application number: 202010194868.5) and "Large-sized Ti2AlNb alloy rings and their manufacturing method" (application number: 202011542728.9) both adopt the above-mentioned dominant process ideas. However, our research found that when preparing large-sized rings, the above-mentioned process has problems such as insufficient ring rolling deformation due to the small inner diameter of the ring, which in turn leads to insufficient shaping of the ring, or the ring is too large along a single flow direction, resulting in excessive differences in mechanical properties in different directions. In view of this, the present invention provides a new method for manufacturing large-sized Ti2AlNb rings. Summary of the Invention

[0004] The present invention discloses a method for manufacturing large-sized Ti2AlNb rings with high fracture toughness and low anisotropy. The high-temperature titanium alloy rings prepared by this method have a basketweave structure, and the differences in the chordal, radial and axial directions of the rings are small. The rings are suitable for preparing large-sized rings for aerospace use. Compared with traditional dual-structure rings, their high-temperature creep, endurance resistance and fracture toughness are greatly improved compared with traditional processes.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy, characterized by comprising the following steps:

[0007] 1) Billet heating: The Ti2AlNb ring billet prepared in the two-phase region or the three-phase region is heated to T β 40℃~120℃ above the transition temperature, heat thoroughly and keep warm for 1~4 hours before taking out of the furnace;

[0008] 2) Forming: After the ring blank is taken out of the furnace, it is quickly transferred to the press to be upset to the process height, and then quickly transferred to the ring rolling mill to expand the hole to the process size;

[0009] 3) Heat treatment: The ring is kept at a temperature of 900-1030° C. and then cooled. Then, it is subjected to air cooling heat treatment at 760-850° C. to obtain a large-sized Ti2AlNb titanium alloy ring with a basketweave structure.

[0010] As the preferred technical solution:

[0011] The blank selected in step 1) is obtained by ring rolling or horse rack expansion in the two-phase region or the three-phase region.

[0012] In step 1), an anti-cooling coating is applied to the surface of the blank before heating to reduce the temperature drop during the deformation process of the blank and ensure that T β The deformation above the phase transition point; or after heating is completed, the blank is taken out, the surface of the blank is coated with asbestos with glass adhesive, and then returned to the furnace for 30 to 60 minutes to reduce the temperature drop during the deformation process of the blank to ensure T β The deformation amount above the phase transition point is further preferably that after rolling, the ring is provided with asbestos on the surface, or asbestos with a thickness of 2 to 10 mm is slowly cooled.

[0013] In step 2), the upsetting deformation of the ring blank is 25-35%, and the upsetting rate is not greater than 0.1s -1 The deformation of the ring rolling expansion is 35% to 50%, and the total deformation of upsetting + ring rolling is not less than 60%; the final rolling temperature of the ring is not less than the alloy T β 15℃ below the phase transition point, the ring is at T β The deformation above the phase transition point is greater than 85% of the total deformation.

[0014] In step 2), after the ring blank is taken out of the furnace, it is transferred to a press within 20 seconds for upsetting to the process height, and then transferred to a ring rolling mill within 30 seconds for hole expansion.

[0015] In step 3), the heat treatment system of the ring is to keep it at 930-990°C for 1-4 hours and then cool it in oil, or cool it in a medium with a cooling rate between oil cooling and air cooling, and then keep it at 760-790°C for 10-25 hours and then air cool it.

[0016] The method of the present invention is used to prepare large-sized Ti2AlNb rings, wherein the outer diameter of the rings is greater than 530 mm and the inner diameter is greater than 450 mm.

[0017] The Ti2AlNb large-size ring prepared by the method of the present invention is characterized in that: the tangential, axial and radial tensile strengths of the ring at room temperature are not less than 1060 MPa, the yield strength is not less than 970 MPa, and the average difference between the tensile strength and yield strength in different directions is not more than 30 MPa; the tangential elongation is not less than 10%, and the area shrinkage is not less than 13%; the axial and radial elongations are not less than 8%, the area shrinkage is not less than 11%, and the difference between the average elongation and area shrinkage in different directions is not more than 3%; the fracture toughness of the alloy in the RC direction at room temperature is 40 to 50 MPa·m 1 / 2 .

[0018] The beneficial effects of the present invention are:

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The titanium alloy rings prepared by the present invention adopt a combination of compression and ring rolling processes to obtain a basket structure, which is suitable for preparing large-sized rings. By matching the deformation amounts of upsetting and ring rolling, the performance differences of the rings along different directions are minimized.

[0021] 2. Through the combination of heating temperature, deformation amount and deformation speed, the B2 phase grain boundary of the alloy becomes serrated, the "fluctuation amplitude" of the grain boundary is larger, and the alloy's plasticity and toughness are better than the basketweave structure prepared by traditional technology.

[0022] The formation of serrated grain boundaries can strengthen the material by increasing the constraints between adjacent grains and increasing the resistance to grain boundary sliding. Therefore, compared with forgings with traditional dual-state structures, the creep and endurance resistance of the material are greatly improved, and compared with the basket structure prepared by traditional processes, the anisotropy of the alloy prepared by the present invention is lower. For example, the tangential, axial and radial tensile strength of the ring prepared by the present invention are not less than 1060Mpa at room temperature, and the yield strength is not less than 970Mpa, and the average difference in tensile strength and yield strength in different directions is not more than 30Mpa; the tangential elongation is not less than 10%, and the area reduction is not less than 13%; the axial and radial elongation are not less than 8%, and the area reduction is not less than 11%, and the difference in average elongation and area reduction in different directions is not more than 3%; the fracture toughness of the alloy in the RC direction at room temperature is 40-50Mpa·m 1 / 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a high-magnification microstructure photograph of the Ti2AlNb ring prepared in Example 1 of the present invention.

[0024] Figure 2 This is a high-magnification microstructure photograph of the Ti2AlNb ring prepared in Example 2 of the present invention.

[0025] Figure 3This is a high-magnification microstructure photograph of the Ti2AlNb ring prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Example 1:

[0028] The raw material used in this embodiment is a Ti2AlNb titanium alloy ring blank with a size of 700×495×400 mm and a weight of 410 kg. The weight percentages of the alloy components are Al: 10.8%, Nb: 42%, Mo: 0.95%, and the balance is Ti and other unavoidable impurity elements. The T of the alloy ingot is detected by metallographic method. β The transformation temperature is 1050℃; the ring blank is obtained by thermal deformation in the two-phase or three-phase region, and the structure is a dual-state structure, and the macrostructure is a fuzzy crystal. The preparation process of the ring is as follows:

[0029] 1) Billet heating: The Ti2AlNb titanium alloy billet is heated to 1120°C in a resistance wire heating furnace. After being heated thoroughly, the billet is kept warm for 4 hours. After heating is completed, the billet is taken out, and the surface of the billet is coated with asbestos with a glass binder. The billet is then returned to the furnace and kept warm for 45 minutes before being forged.

[0030] 2) Forming: After the billet is taken out of the furnace, it is quickly transferred to the press for upsetting forging within 15 seconds. The upsetting operation is Ф700×Ф495×400mm→~Ф750×~Ф480×300mm, with a speed of 0.08s. -1 The billet was upset at a strain rate of 1000 mm and the upsetting deformation was 25%. After upsetting, the billet was quickly transferred to a Φ800 mm ring rolling mill for rolling within 25 seconds. After hole expansion and rolling, a Ti2AlNb titanium alloy ring forging with an outer diameter of 1150 mm, an inner diameter of 950 mm and a height of 300 mm was obtained. The rolling deformation was 44%. The ring forging was formed from the billet in one heat. The total deformation of upsetting and ring rolling was 69%. The total deformation time was 4 minutes and 25 seconds. The final rolling temperature was 1000°C. When the ring was rolled to an outer diameter of 1000 mm and an inner diameter of 930 mm, the surface temperature of the ring was about 1050°C, and 87% of the total deformation had been completed. After rolling, the asbestos on the surface of the ring was slowly cooled.

[0031] 3) Heat treatment: The obtained ring was subjected to double heat treatment, the first heat treatment was 960°C for 2 hours and then oil cooling, and the second heat treatment was 780°C for 24 hours and then air cooling to obtain a titanium alloy ring with basket structure.

[0032] The high magnification microstructure of the Ti2AlNb titanium alloy ring prepared in Example 1 is shown in FIG. Figure 1 The performance test results are shown in Table 1:

[0033] Table 1 Mechanical properties of Ti2AlNb ring in Example 1

[0034]

[0035]

[0036] Example 2:

[0037] The raw material used in this embodiment is a Ti2AlNb titanium alloy ring blank with a size of Ø470×Ø150×290 mm and a weight of 238 kg. The weight percentages of the alloy components are Al: 11%, Nb: 43%, Mo: 0.88%, and the balance is Ti and other inevitable impurity elements. The T of the alloy ingot is detected by metallographic method. β The transformation temperature is 1055℃; the ring blank is obtained by thermal deformation in the two-phase or three-phase region, and the structure is a dual-state structure, and the macrostructure is fuzzy crystal. The preparation process of the ring is as follows:

[0038] 1) Billet heating: The Ti2AlNb titanium alloy rod is heated to 1130°C in a resistance wire heating furnace. After being heated thoroughly, the billet is kept warm for 2 hours. After heating is completed, the billet is taken out, the surface is coated with asbestos with a glass binder, and then returned to the furnace for 30 minutes.

[0039] 2) Forming: After the billet is taken out of the furnace, it is quickly transferred to the press for upsetting forging within 15 seconds. The upsetting operation is Ф470×Ф150×290mm→~Ф530×~Ф150×220mm, with a speed of 0.06s. -1 The strain rate is used for upsetting, and the upsetting deformation is 25%. After upsetting, the billet is quickly transferred to a Φ800mm ring rolling mill within 15 seconds for rolling. After hole expansion and rolling, a Ti2AlNb titanium alloy ring forging with an outer diameter of 750mm, an inner diameter of 550mm and a height of 220mm is obtained. The rolling deformation is 48%. The ring forging is formed by the billet in one fire. The total deformation of upsetting and ring rolling is 73%. The total deformation time is 3 minutes and 43 seconds. The final rolling temperature is 1052℃, and the final forging temperature is only lower than T β Phase transition point 3℃, more than 95% of the deformation occurs at T β The phase change point is completed, and the ring with asbestos on the surface is slowly cooled after rolling.

[0040] 3) Heat treatment: The obtained ring was subjected to double heat treatment, the first heat treatment was 970°C for 2 hours and then oil cooling, and the second heat treatment was 780°C for 24 hours and then air cooling to obtain a titanium alloy ring with basket structure.

[0041] The high magnification microstructure photo of the Ti2AlNb titanium alloy ring prepared in Example 2 is as follows: Figure 2 The performance test results are shown in Table 2:

[0042] Table 2 Mechanical properties of Ti2AlNb ring in Example 2

[0043]

[0044] Example 3:

[0045] The raw material used in this embodiment is a Ti2AlNb titanium alloy ring blank with a size of 600×430×240 mm and a weight of 174 kg. The weight percentages of the alloy components are Al: 11.3%, Nb: 43%, Mo: 0.6%, and the balance is Ti and other unavoidable impurity elements. The T of the alloy ingot is detected by metallographic method. β The transformation temperature is 1060℃; the ring blank is obtained by thermal deformation in the two-phase or three-phase region, and the structure is a dual-state structure, and the macrostructure is a fuzzy crystal. The preparation process of the ring is as follows:

[0046] 1) Billet heating: The Ti2AlNb titanium alloy billet is heated to 1130°C in a resistance wire heating furnace. After being heated thoroughly, the billet is kept warm for 3 hours. After heating is completed, the billet is taken out, the surface is coated with asbestos with a glass binder, and then returned to the furnace for 60 minutes.

[0047] 2) Forming: After the billet is taken out of the furnace, it is quickly transferred to the press for upsetting forging within 15 seconds. The upsetting operation is Ф600×Ф430×240mm→~Ф648×~Ф411×178mm, with a speed of 0.08s. -1 The strain rate is used for upsetting, and the upsetting deformation is 30%. After upsetting, the billet is quickly transferred to the Φ800mm ring rolling mill within 15s for rolling. After hole expansion and rolling, a Ti2AlNb titanium alloy ring forging with an outer diameter of 900mm, an inner diameter of 770mm and a height of 180mm is obtained. The rolling deformation is 42%. The ring forging is formed by the billet in one fire. The total deformation of upsetting and ring rolling is 72%. The total deformation time is 4 minutes and 9 seconds. The final rolling temperature is 1048℃. Nearly 90% of the deformation occurs at T β The ring is rolled above the phase change point and then covered with asbestos with a thickness of 5 mm and slowly cooled.

[0048] 3) Heat treatment: The obtained ring was subjected to double heat treatment, the first heat treatment was 940°C for 2 hours and then oil cooling, and the second heat treatment was 760°C for 24 hours and then air cooling to obtain a titanium alloy ring with basket structure.

[0049] The high magnification microstructure of the Ti2AlNb titanium alloy ring prepared in Example 3 is shown in FIG. Figure 3 The performance test results are shown in Table 3:

[0050] Table 3 Mechanical properties of Ti2AlNb ring in Example 3

[0051]

[0052] Matters not covered by the present invention are known technologies.

[0053] 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 manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy, characterized in that: The steps include: 1) Billet heating: The Ti2AlNb ring billet prepared in the two-phase region or the three-phase region is heated to T β 40℃~120℃ above the transition temperature, heat thoroughly and keep warm for 1~4 hours before taking out of the furnace; 2) Forming: After the ring blank is taken out of the furnace, it is quickly transferred to the press and upsetting to the process height. The upsetting deformation of the ring blank is 25-35%, and the upsetting rate is not more than 0.1s -1 , and then quickly transferred to the ring rolling mill, the deformation of the ring rolling expansion is 35% to 50%, and the total deformation of upsetting + ring rolling is not less than 60%; the final rolling temperature of the ring is not lower than the alloy T β 15℃ below the phase transition point, the ring is at T β The deformation above the phase transition point is greater than 85% of the total deformation; 3) Heat treatment: The ring is kept at a temperature of 900-1030° C. and then cooled. Then, it is heat treated in air at 760-850° C. to obtain a large-sized Ti2AlNb titanium alloy ring with a basketweave structure.

2. The method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy according to claim 1, characterized in that: The blank selected in step 1) is obtained by ring rolling or horse rack expansion in two-phase or three-phase regions.

3. The method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy according to claim 1, characterized in that: In step 1), an anti-cooling coating is applied to the surface of the blank before heating, or the blank is taken out after heating is completed, and the surface of the blank is coated with asbestos with a glass binder and then returned to the furnace for insulation for 30 to 60 minutes.

4. The method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy according to claim 1, characterized in that: In step 2), after the ring blank is taken out of the furnace, it is transferred to a press within 20 seconds for upsetting to the process height, and then transferred to a ring rolling mill within 30 seconds for hole expansion.

5. The method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy according to claim 1, characterized in that: In step 3), the heat treatment system of the ring is to keep it at 930-990°C for 1-4 hours and then cool it in oil, or cool it in a medium with a cooling rate between oil cooling and air cooling, and then keep it at 760-790°C for 10-25 hours and then air cool it.

6. The method for manufacturing a large-sized Ti2AlNb ring with high fracture toughness and low anisotropy according to claim 1, characterized in that: The outer diameter of the ring is greater than 530 mm, and the inner diameter is greater than 450 mm.

7. A large-sized Ti2AlNb ring prepared by the method of claim 1, characterized in that: The room temperature tensile strength of the ring in the tangential, axial and radial directions is not less than 1060 MPa, the yield strength is not less than 970 MPa, and the average difference in tensile strength and yield strength in different directions is not more than 30 MPa; the tangential elongation is not less than 10%, and the area reduction is not less than 13%; the axial and radial elongation is not less than 8%, and the area reduction is not less than 11%, and the difference in average elongation and area reduction in different directions is not more than 3%; the fracture toughness of the alloy in the RC direction at room temperature is 40 to 50 MPa m 1 / 2 .

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