A large turbine disc forging and preparation method thereof

Abstract

The present invention discloses a large turbine disk forging and a preparation method thereof, which belongs to the technical field of difficult-to-deform high-temperature alloys, and solves one of the problems in the prior art that the large turbine disk preparation process is prone to cracking, poor structural uniformity, and poor comprehensive mechanical properties. The preparation method comprises: smelting to obtain a steel ingot; blanking the steel ingot into a bar; using a die forging press to make a cake; using a die forging press to prepare a preform; using a die forging press to forge and prepare a final forging; critical solution treatment; low-temperature aging treatment to obtain a large turbine disk forging; the temperature T1 of the cake in step 2, the temperature T2 of the preform in step 3, and the temperature T3 of the final forging in step 4 meet the following relationship: T1>T2>T3. The turbine disk forging prepared by the method of the present invention has excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of difficult-to-deform high-temperature alloys, and in particular to a large turbine disk forging and a preparation method thereof. Background Art

[0002] Difficult-to-deform high-temperature alloys are widely used in aircraft engine and industrial gas turbine turbine disk components. The composition control range of existing difficult-to-deform high-temperature alloys is relatively wide, which can no longer meet the control requirements of the organizational properties of large difficult-to-deform turbine disks.

[0003] With the increase of gas turbine and engine thrust, the specifications of turbine discs are constantly expanding. When using traditional forging process to produce large-sized turbine discs, due to the difficulty in forming hard-to-deform high-temperature alloys, the blanks are prone to instability and scrap during the forging process. During the die forging process, due to the complex structure and shape of the turbine disc, it is easy to deform unevenly in various areas, resulting in poor consistency of its structure and performance. In the prior art, in order to facilitate the forming of large turbine discs made of hard-to-deform high-temperature alloys, the heating temperature used during the final forging is relatively high, resulting in coarse structure of the turbine disc and reduced comprehensive mechanical properties; therefore, the traditional forging process can no longer meet the control requirements for the uniformity of the structure and performance of large turbine discs made of hard-to-deform alloys. Summary of the invention

[0004] In view of the above situation, the present invention aims to provide a large turbine disk forging and a preparation method thereof, which is used to solve one of the problems of easy cracking, poor structural uniformity and poor comprehensive mechanical properties in the existing large turbine disk preparation process.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a large turbine disk forging, comprising the following steps:

[0007] Step 1: Smelting to obtain steel ingots; the steel ingots are cut into bars;

[0008] Step 2: Use a die forging press to upset the cake;

[0009] Step 3: Prepare the preform using a die forging press;

[0010] Step 4: Forging the final forging by using a die forging press;

[0011] Step 5: critical solution treatment;

[0012] Step 6: Low temperature aging treatment to obtain a large turbine disk forging;

[0013] Among them, the temperature T1 of the upsetting cake in step 2, the temperature T2 of preparing the preform in step 3, and the temperature T3 of preparing the final forging in step 4 meet the following relationship: T1>T2>T3.

[0014] Furthermore, the components of the large turbine disk forgings include, by mass percentage: C: 0.04% ~ 0.06%, Cr: 13.0% ~ 15.0%, Co: 9.0% ~ 11.0%, Mo: 4.5% ~ 5.50%, Al: 2.60% ~ 2.80%, Ti: 2.60% ~ 2.80%, Nb: 2.4% ~ 2.7%, 7.80% ≤ (Al + Ti + Nb) ≤ 7.95%, Nickel: balance.

[0015] Furthermore, the deformation amount a1 of the upset in step 2, the deformation amount a2 of the preform in step 3, and the deformation amount a3 of the final forging in step 4 meet the following relationship: a1>a3>a2.

[0016] Furthermore, the deformation rate v1 of the upsetting cake in step 2, the deformation rate v2 of the preform prepared in step 3, and the deformation rate v3 of the final forging prepared in step 4 meet the following relationship: v1>v3>v2.

[0017] Furthermore, in step 2, the specific steps of upsetting the cake include:

[0018] S201, use heat preservation cotton and stainless steel plate to hard cover the rod;

[0019] S202, after the rod is wrapped, it is placed in a heating furnace and heated to 1120-1145°C for 8-16 hours;

[0020] S203, pressing the cake on a press.

[0021] Furthermore, in S203, the deformation amount a1 of the upset cake is 50% to 60%, and the deformation rate v1 is 20 to 30 mm / s.

[0022] Furthermore, in step 3, the specific steps of using a die forging press to prepare the preform include:

[0023] S301, use heat preservation cotton and stainless steel plate to hard cover the rod;

[0024] S302, after the jacketing treatment, the tube is placed in a heating furnace, the temperature is raised to 1110-1120°C, and the temperature is kept for 8-16 hours;

[0025] S303, preparing a preform on a press.

[0026] Furthermore, in S303, the deformation amount a2 is 10% to 30%, and the deformation rate v2 is 6 to 10 mm / s.

[0027] Furthermore, in step 4, the final forging temperature T3 is 1060-1080°C.

[0028] The present invention also provides a large turbine disk forging, which is prepared by the above-mentioned preparation method.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0030] a) In the preparation method of large turbine disk forgings of the present invention, by adopting the steps of one-time upsetting + preparing preforms + preparing final forgings, and by accurately controlling the temperature relationship of each step, the uneven deformation and macro-rheological instability of the blank during multiple upsetting can be effectively avoided; in the preparation process of the present invention, the forgings are not easy to crack, the microstructure is uniform, and the yield rate reaches more than 95%.

[0031] b) The preparation method of the present invention can improve the uniformity of the structure of large turbine disk forgings. During low-temperature final forging, the deformation of each region of the turbine disk is relatively uniform, and the strain of each region is higher than the critical strain of dynamic recrystallization, so that each region of the disk can fully undergo dynamic recrystallization to the greatest extent, and the disk structure is uniform; and the structure is refined to the greatest extent. At the same time, during low-temperature forging, there is a large amount of undissolved primary γ′ phase in the matrix, and the grain size is of the same order of magnitude as the primary γ′ phase size, forming a dual-phase structure. The dual-phase structure has high plasticity, which is convenient for the forming of large-scale and complex-structured turbine disks of difficult-to-deform high-temperature alloys.

[0032] c) The preparation method of the present invention adopts critical solution heat treatment, the primary γ′ phase grows, and a small amount of the primary γ′ phase dissolves; the grain size of the matrix increases slightly, and it is still a fine-grained structure, and the coarse deformed grains remaining in the matrix can undergo static recrystallization, the uniformity of the structure is improved, the difference between the size of the γ′ phase and the grain size is further reduced, and the matrix is ​​still a two-phase structure. Using a lower aging temperature, the number of spherical and fine tertiary γ′ phases precipitated in the matrix increases, and the size is 5 to 50nm. The fine tertiary γ′ phase has no obvious coarsening under 650℃, and has high durability under 650℃ / 873MPa.

[0033] d) The large turbine disk forging of the present invention optimizes the content of Al, Ti, and Nb, and combines a precise preparation method to obtain a γ+γ′ dual-phase structure, and through precise control of the temperature, deformation parameters and other data of each step, the large turbine disk forging fully undergoes dynamic recrystallization in the low-temperature forging stage, refines the grains, reduces the tendency of organizational inheritance, and avoids the generation of mixed crystals; combined with critical solid solution + low-temperature aging heat treatment process; finally controls the grain size and the number and size of the γ′ phase in the matrix, and finally obtains a fine and uniform dual-phase structure, improves the hot working plasticity of the large turbine disk during low-temperature forging, and improves the uniformity of the organizational performance of the large difficult-to-deform high-temperature alloy turbine disk, so that it has good comprehensive mechanical properties. The large turbine disk forging of the present invention can be in long-term stable service at 650℃ / 873MPa, and is one of the important materials for high-temperature and high-strength structural parts in the current aerospace engine and ship gas turbine fields.

[0034] e) The microstructure of the large turbine disk forging of the present invention is 5-7 level homogeneous crystal, and the matrix is ​​a γ+γ′ dual-phase structure. The volume fraction of the γ′ phase is 35% to 40%, wherein the size of the primary γ′ phase is 300 to 3000 nm, and the volume fraction is 2% to 7% (for example, 2% to 5%); the size of the secondary γ′ phase is 80 to 300 nm, and the volume fraction is 10% to 16% (for example, 11% to 16%); the size of the tertiary γ′ phase is 5 to 50 nm, and the volume fraction is 18% to 20%.

[0035] f) The room temperature tensile strength of the large turbine disk forging of the present invention is ≥1480MPa (e.g. 1485-1500MPa), the yield strength is ≥1000MPa (e.g. 1005-1050MPa), the elongation after fracture is ≥18% (e.g. 18%-24%), the cross-sectional shrinkage is ≥18% (e.g. 19%-25%), the absorbed energy is ≥40J (e.g. 41-50J), and the room temperature U-type impact toughness is ≥50J / cm 2 (e.g. 51-58 J / cm 2 ), Brinell hardness is HBW 365 or above (for example, HBW369-390); high temperature performance at 650°C: creep rupture time ≥60h (for example, 60-85h), elongation after fracture ≥2% (for example, 2.6%-6%), and section shrinkage ≥3% (for example, 3.6%-10%).

[0036] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0038] Figure 1 The rod structure and γ′ phase morphology in Example 1 of the present invention;

[0039] Figure 2 The microstructure and γ′ phase morphology of the large turbine disk forging of Example 1 of the present invention;

[0040] Figure 3 The microstructure and γ′ phase morphology of the large turbine disk forging of Example 2 of the present invention;

[0041] Figure 4 The microstructure and γ′ phase morphology of the large turbine disk forging of Example 3 of the present invention;

[0042] Figure 5 The microstructure and γ′ phase morphology of Comparative Example 1;

[0043] Figure 6 The microstructure and γ′ phase morphology of Comparative Example 2;

[0044] Figure 7 This is the microstructure morphology and γ′ phase morphology of Comparative Example 3. DETAILED DESCRIPTION

[0045] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0046] The invention provides a large turbine disk forging, wherein the diameter of the large turbine disk forging is greater than 850 mm.

[0047] The inventors found in their in-depth research that the strengthening elements Al, Ti, and Nb in the hard-to-deform high-temperature alloys used in existing turbine disk forgings are too broadly controlled and cannot accurately meet the requirements of the microstructure and performance of large turbine disks. Therefore, based on the dynamic recrystallization law of hard-to-deform high-temperature alloys, the inventors systematically studied the relationship between key process parameters such as deformation temperature, deformation amount, strain rate, and microstructure and mechanical properties; accurately controlled the components and preparation methods of large turbine disk forgings, and prepared hard-to-deform large turbine disk forgings, which can serve for a long time at 700°C and meet the comprehensive performance requirements of long-term service of rotating parts at 700°C.

[0048] Specifically, the components of the above-mentioned large turbine disk forgings include, by mass percentage: C: 0.04%~0.06%, Cr: 13.0%~15.0%, Co: 9.0%~11.0%, Mo: 4.5%~5.50%, Al: 2.60%~2.80%, Ti: 2.60%~2.80%, Nb: 2.4%~2.7%, 7.80%≤(Al+Ti+Nb)≤7.95%, Nickel: balance.

[0049] Specifically, in the large turbine disk forging of the present invention, when the contents of Al and Ti are less than 2.60% respectively and the content of Al+Ti+Nb is less than 7.80%, the strength of the alloy decreases; when the contents of Al and Ti exceed 2.80% respectively and the content of Al+Ti+Nb exceeds 7.95%, the matrix hardness of the alloy increases significantly, and the machining difficulty of the turbine disk forging increases. Therefore, in the present invention, by optimizing the contents of Al, Ti, and Nb, controlling 7.80%≤(Al+Ti+Nb)≤7.95%, the content of γ′ phase in the matrix reaches 35% to 40%, and a dual-phase structure is prepared by a subsequent forging process. At the same time, the hardness of the matrix is ​​maintained at a low level, and good machining performance is obtained.

[0050] In order to further optimize the performance of the above-mentioned large turbine disk forgings, the components of the above-mentioned large turbine disk forgings include, by mass percentage: C: 0.041%~0.05%, Cr: 13.2%~14.0%, Co: 10.0%~11.0%, Mo: 4.7%~5.50%, Al: 2.60%~2.75%, Ti: 2.60%~2.70%, Nb: 2.5%~2.6%, 7.85%≤(Al+Ti+Nb)≤7.95%, Nickel: balance.

[0051] The present invention also provides a method for preparing the above-mentioned large turbine disk forging, comprising the following steps:

[0052] Step 1: sequentially perform vacuum induction melting and vacuum consumable melting to obtain a steel ingot; and perform bar blanking on the steel ingot;

[0053] Step 2: Use a die forging press to upset the cake;

[0054] Step 3: Prepare the preform using a die forging press;

[0055] Step 4: Forging the final forging by using a die forging press;

[0056] Step 5: critical solution treatment;

[0057] Step 6: Low temperature aging treatment to obtain a large turbine disk forging;

[0058] Among them, the temperature T1 of the upsetting cake in step 2, the temperature T2 of preparing the preform in step 3, and the temperature T3 of preparing the final forging in step 4 meet the following relationship: T1>T2>T3.

[0059] Specifically, in the above step 1, vacuum induction melting includes full melting, refining and tapping, the full melting temperature is 1480-1580°C, the vacuum degree of full melting is 0-50Pa; the refining temperature is 1500-1590°C, the refining vacuum degree is 0-30Pa, and the tapping temperature is 1400-1500°C.

[0060] Specifically, in the above step 1, the arc starting stage of vacuum consumable melting adopts current + droplet control, the melting rate control range is 2.7 to 4.5 kg / min, and the vacuum degree in the stable melting stage is ≤2 Pa.

[0061] Specifically, in the above step 1, the bar blanking includes: after the blank is homogenized, it is forged into a bar on a blanking machine with a capacity of more than 4000 tons, the blanking temperature is 1100-1150° C., the deformation amount is 20%-40%, and the deformation rate is 10-20 mm / s.

[0062] Specifically, the deformation amount a1 of the upset in step 2, the deformation amount a2 of the preform in step 3, and the deformation amount a3 of the final forging in step 4 meet the following relationship: a1>a3>a2.

[0063] Specifically, the deformation rate v1 of the upsetting cake in step 2, the deformation rate v2 of the preform in step 3, and the deformation rate v3 of the final forging in step 4 meet the following relationship: v1>v3>v2.

[0064] Specifically, in the above step 2, the specific steps of upsetting the cake include:

[0065] S201, use 5-8mm aluminum silicate insulation cotton and 0.5-1.5mm stainless steel plate to hard cover the bar material to reduce the surface temperature drop of the bar material during transfer and forging;

[0066] S202, after the rod is wrapped, it is placed in a heating furnace, heated to T1 (1120-1145°C), and kept warm for 8-16 hours;

[0067] S203, performing upsetting on a press, wherein the deformation amount a1 of the upsetting is 50% to 60%, and the deformation rate v1 is 20 to 30 mm / s;

[0068] S204. After forging the cake, lathe the two end faces of the cake blank and machine a circular hole of Φ60-80mm in the center of the cake blank.

[0069] It should be noted that in the above S202, since the alloy of the present invention is a difficult-to-deform high-temperature alloy, when the temperature is low during the upsetting process, the γ′ phase in the matrix is ​​not completely dissolved, the deformation resistance during the upsetting process is large, and the rod is prone to instability and surface cracks. However, when the heating temperature exceeds 1145°C, the grains in the matrix increase rapidly, the plasticity of the rod decreases, and the billet is prone to cracks during the upsetting process and is scrapped; therefore, the temperature is controlled to be 1120-1145°C.

[0070] Specifically, in the above S202, when the deformation exceeds 50%, a larger deformation is conducive to sufficient recrystallization of the bar structure; but when the deformation exceeds 60%, the deformation resistance during the upsetting process increases rapidly, and the bar is prone to instability and double bulging. Therefore, the deformation of the upsetting is controlled to be 50% to 60%.

[0071] Specifically, in the above S202, when the deformation rate is above 20 mm / s, the higher deformation rate avoids the temperature drop of the bar during the upsetting process, and reduces the cracks caused by the decrease in the surface temperature of the bar blank; when the deformation rate exceeds 30 mm / s, the bar structure does not have time to undergo dynamic recrystallization, resulting in uneven structure of the cake blank, which is difficult to completely eliminate in the subsequent forging process. Therefore, the deformation rate v1 is controlled to be 20-30 mm / s.

[0072] Specifically, in the above S203, the press is a 10,000-30,000 ton hydraulic press.

[0073] Specifically, in the above S203, due to the large size of the mold, the depth of the cold mold affected zone of the cake blank increases when the heating temperature is low, and machining fails to remove all the cold mold affected zones, resulting in a large amount of insufficiently recrystallized structure remaining on the cake blank, resulting in uneven microstructure and performance of subsequent turbine disk forgings, and due to the large amount of cold mold affected zones remaining on the surface, the surface hardness of the cake blank increases, which is not conducive to the processing of the cake blank; when the heating temperature is too high, the mold needs to be kept warm for a long time, which reduces the production efficiency of the turbine disk forgings, and therefore, the mold temperature is controlled to be 370-430°C.

[0074] Specifically, in the above step 3, the specific steps of using a die forging press to prepare the preform include:

[0075] S301, use 5-8mm aluminum silicate insulation cotton and 0.5-1.5mm stainless steel plate to cover the cake blank;

[0076] S302, after the jacketing treatment, place it in a heating furnace, raise the temperature to T2 (1110-1120°C), and keep it warm for 8-16 hours;

[0077] S303, preparing a preform on a press, with a deformation amount a2 of 10% to 30%, a deformation rate v2 of 6 to 10 mm / s, and then grinding the surface of the preform forging.

[0078] Specifically, in the above S302, when T2 is between 1110 and 1120°C, a small amount of coarse primary γ′ phase exists in the matrix, and the primary γ′ phase can prevent excessive grain growth and ultimately refine the grains of the cake blank through dynamic recrystallization during the forging process.

[0079] Specifically, in the above S303, the deformation amount a2 is 10% to 30%. The smaller deformation amount mainly adjusts the shape of the hub area to form a preform forging, so as to prepare for the hub area to be fully deformed and undergo dynamic recrystallization during final forging.

[0080] Specifically, in the above S303, the deformation rate v2 is 6-10 mm / s. A lower deformation rate can reduce the wear of the blank on the die, improve the surface quality of the forging, and provide high-quality preform forgings for final forging.

[0081] Specifically, in the above step 4, the specific steps of preparing the final forging include:

[0082] S401, use 5-8 mm aluminum silicate insulation cotton and 0.5-1.5 mm stainless steel plate to cover the preform;

[0083] S402, after the jacketing treatment, place it in a heating furnace, raise the temperature to T3 (1060-1080°C), and keep it warm for 8-16 hours;

[0084] S403, forging is performed on a press to prepare a final forging, the deformation amount a3 is 30% to 40%, the deformation rate v3 is 15 to 25 mm / s, and the surface of the forging is polished after the final forging.

[0085] Specifically, in the above S402, the final forging temperature T3 is 1060-1080°C, and the final forging temperature range is located in the γ+γ′ two-phase region. There are a large number of undissolved primary γ′ phases in the matrix, which can significantly prevent the growth of grains, and finally obtain fine grains. The grain size and the primary γ′ phase size reach the same order of magnitude, forming a two-phase structure.

[0086] Specifically, in the above S403, when the deformation a3 is less than 30%, the matrix structure of the preform forging cannot be fully recrystallized; when the deformation a3 exceeds 40%, the equipment load increases rapidly, and a large deformation heat is generated, causing the core of the forging to heat up, inducing the growth of the grains in the core of the forging, resulting in uneven forging structure. Therefore, the deformation a3 is controlled to be 30% to 40%.

[0087] Specifically, in the above S403, during low temperature forging, the deformation rate is increased, the dynamic recrystallization ratio of the matrix increases, and the large turbine disk forgings are easy to obtain uniform structure; when the deformation rate exceeds 25mm / s, the forgings are prone to instability and cracks. Therefore, the deformation rate v3 is controlled to be 15-25mm / s.

[0088] Specifically, during the forging process in the above steps 2, 3, and 4, two layers of thermal insulation cotton are respectively placed on the contact parts between the blank and the upper and lower dies, and the thickness of the thermal insulation cotton is 7 to 9 mm. Such a setting can increase the thermal insulation effect of the large turbine disk forgings, reduce the temperature drop when the forgings contact the dies, and minimize the cold die affected area of ​​the large turbine disk forgings.

[0089] Specifically, after forging is completed in the above steps 2, 3 and 4, the can is quickly removed to allow the forging to be quickly air-cooled, and the cooling rate of the forging is controlled at 10-35° C. / min.

[0090] Specifically, in the above S403, the surface of the forging is cleaned after final forging, and there should be no cracks, slag inclusions, scars, indentations and other damage that damages the density of the metal on the surface of the forging. When the above defects are found, they should be removed by inclined grinding, and the cleaning depth of the forging defects should not exceed the dimensional deviation calculated by the nominal size. The above final forging is rough-machined to obtain a difficult-to-deform high-temperature alloy die forging.

[0091] Specifically, in the above step 5, the critical solid solution temperature is in the critical temperature range where the γ′ phase is about to be completely dissolved, the heat preservation time is 8 to 10 hours, and the disc is quickly air-cooled after being taken out of the furnace.

[0092] Specifically, after in-depth research, in the above step 5, the critical solution treatment temperature is controlled to be Ts=1095+59(X Al -2.6)+13(X Ti -2.6)+18(X Mo -5)+6.5(X Nb -2.6)-12(X Cr -14), where: X Al , X Ti , X Mo , X Nb , X Cr - Mass percentage of the corresponding element * 100, for example, the mass percentage of Al is 2.60%, then, here X Al is 2.60.

[0093] Specifically, in the above step 5, the critical solution heat treatment temperature is 1090-1110°C.

[0094] Specifically, in the above step 6, the specific steps of low temperature aging treatment are: the temperature of low temperature aging treatment is 720-760° C., the insulation time is 16-18 hours, and air cooling is performed after the furnace is taken out.

[0095] Specifically, the present invention adopts critical solution treatment to prevent excessive grain growth, and at the same time, static recrystallization of coarse deformed grains in the matrix occurs, eliminating coarse grain structure and improving matrix structure uniformity; in addition, the size of the primary γ′ phase is increased by critical solution treatment, and the structure is still a two-phase structure. Finally, the proportion of fine tertiary γ′ phase in the matrix is ​​increased by low-temperature aging heat treatment process, ensuring that the turbine disk has high durability at 650℃ / 873MPa.

[0096] Specifically, the microstructure of the large turbine disk forging obtained in the above step 6 is 5-7 level homogeneous crystal, and the matrix is ​​a γ+γ′ two-phase structure.

[0097] Specifically, the volume fraction of the above-mentioned γ′ phase is 35% to 40%, wherein the size of the primary γ′ phase is 300 to 3000 nm, and the volume fraction is 2% to 7% (for example, 2% to 5%); the size of the secondary γ′ phase is 80 to 300 nm, and the volume fraction is 10% to 16% (for example, 11% to 16%); the size of the tertiary γ′ phase is 5 to 50 nm, and the volume fraction is 18% to 20%.

[0098] Specifically, the room temperature tensile strength of the large turbine disk forgings is ≥1480MPa (e.g. 1485-1500MPa), the yield strength is ≥1000MPa (e.g. 1005-1050MPa), the elongation after fracture is ≥18% (e.g. 18%-24%), the cross-sectional shrinkage is ≥18% (e.g. 19%-25%), the absorbed energy is ≥40J (e.g. 41-50J), and the room temperature U-type impact toughness is ≥50J / cm 2 (e.g. 51-58 J / cm 2 ), Brinell hardness is HBW 365 or above (for example, HBW369-390); high temperature performance at 650°C: creep rupture time ≥60h (for example, 60-85h), elongation after fracture ≥2% (for example, 2.6%-6%), and section shrinkage ≥3% (for example, 3.6%-10%).

[0099] Specifically, during the preparation process of the present invention, the forging is not easy to crack, has good structural uniformity, and the yield rate reaches more than 95%.

[0100] Compared with the prior art, in the preparation process of turbine disk forgings, multiple upsettings aggravate the uneven deformation of the blank. The serious uneven deformation of the blank not only directly affects the size of the round cake but also has a serious impact on the uniformity of the organizational properties of the blank. In certain circumstances, the blank is damaged and scrapped due to the severe localized plastic deformation. In the preparation method of large turbine disk forgings of the present invention, by adopting the steps of one upsetting + preparing preforms + preparing final forgings, and by accurately controlling the temperature relationship of each step, the uneven deformation and macro-rheological instability of the blank during multiple upsetting can be effectively avoided.

[0101] The preparation method of the present invention can improve the uniformity of the structure of large turbine disk forgings. During low-temperature final forging, the deformation of each region of the turbine disk is relatively uniform, and the strain of each region is higher than the critical strain of dynamic recrystallization, so that each region of the disk can fully undergo dynamic recrystallization to the greatest extent, and the disk structure is uniform; and the structure is refined to the greatest extent. At the same time, during low-temperature forging, a large amount of undissolved primary γ′ phase exists in the matrix, and the grain size is of the same order of magnitude as the primary γ′ phase size, forming a dual-phase structure. The dual-phase structure has high plasticity, which is convenient for forming large-scale and complex-structured turbine disks of difficult-to-deform high-temperature alloys.

[0102] The preparation method of the present invention adopts critical solution heat treatment, the primary γ′ phase grows, a small amount of the primary γ′ phase dissolves; the grain size of the matrix increases slightly, and it is still a fine-grained structure, and the coarse deformed grains remaining in the matrix can undergo static recrystallization, the uniformity of the structure is improved, the difference between the size of the γ′ phase and the grain size is further reduced, and the matrix is ​​still a two-phase structure. By adopting a lower aging temperature, the number of spherical fine tertiary γ′ phases precipitated in the matrix increases, the size is 5 to 50nm, the fine tertiary γ′ phase has no obvious coarsening under 650°C, and has high durability under 650°C / 873MPa.

[0103] The large turbine disk forging of the present invention optimizes the content of Al, Ti, and Nb, and combines a precise preparation method to obtain a γ+γ′ dual-phase structure, and through precise control of the temperature, deformation parameters and other data of each step, the large turbine disk forging fully undergoes dynamic recrystallization in the low-temperature forging stage, refines the grains, reduces the tendency of organizational inheritance, and avoids the generation of mixed crystals; combined with a critical solid solution + low-temperature aging heat treatment process; and finally controls the grain size and the number and size of the γ′ phase in the matrix, and finally obtains a fine and uniform dual-phase structure, improves the hot working plasticity of the large turbine disk during the low-temperature forging process, and improves the uniformity of the organizational properties of the large difficult-to-deform high-temperature alloy turbine disk, so that it has good comprehensive mechanical properties. The large turbine disk forging of the present invention can be in long-term stable service at 650°C / 873MPa, and is one of the important materials for high-temperature and high-strength structural parts in the current aerospace engine and ship gas turbine fields.

[0104] Examples 1-3

[0105] The advantages of precise control of the composition and process parameters of the large turbine disk forging of the present invention are demonstrated below with specific embodiments and comparative examples.

[0106] Embodiments 1-3 of the present invention provide a large turbine disk forging and a preparation method thereof. The chemical compositions of Embodiments 1-3 are shown in Table 1.

[0107] The preparation method of Example 1 comprises:

[0108] Step 1: vacuum induction melting to obtain a steel ingot; the full melting temperature is 1530°C, the full melting vacuum is 6Pa; the refining temperature is 1540°C, the refining vacuum is 6Pa, the tapping temperature is 1480°C, and it is cast into a Φ660mm ingot; the Φ660mm ingot is polished, then the riser is cut off, and the two end surfaces are processed to be parallel; then vacuum consumable melting is carried out, and the arc starting stage adopts current + droplet control, the current is 3.6kA, the voltage is 23.2V, and the arc starting stage time is 55min; the melting rate in the stable stage is 3.0kg / min, and the vacuum degree in the stable melting stage is 2Pa; the current in the shrinkage stage is 1.2kA, the cooling water temperature is 22°C, and the cooling time is 4h, and then the air is broken and demolded to obtain a Φ660mm steel ingot;

[0109] The Φ660mm steel ingot is blanked: first, the steel ingot is homogenized, the highest homogenization temperature is 1180℃, and the holding time is 80h. After homogenization, the blank is forged into a bar on a blanking machine with a capacity of more than 4000 tons, the blanking temperature is 1150℃, the final forging temperature is 1080℃, and after 8 fire deformations, the average deformation amount is 30%, the deformation rate is 15mm / s, and the bar size after turning is Φ360×760mm;

[0110] Step 2: Upsetting the cake using a die forging press:

[0111] S201, use 8mm aluminum silicate insulation cotton and 1mm stainless steel plate to hard pack the rod.

[0112] S202, after the rod is wrapped, it is placed in a heating furnace, heated to 1120°C, and kept warm for 10 hours;

[0113] S203, upsetting the cake on a 30,000-ton hydraulic press, with a die temperature of 400°C, a deformation amount a1 of 50%, and a deformation rate v1 of 20 mm / s;

[0114] S204, after upsetting the cake, lathe the two end surfaces of the cake blank, and machine a Φ60mm round hole in the center of the cake blank;

[0115] Step 3: Prepare the preform using a die forging press:

[0116] S301, use 8mm aluminum silicate insulation cotton and 1mm stainless steel plate to wrap the cake blank;

[0117] S302, after the jacketing treatment, the tube is placed in a heating furnace, the temperature is raised to 1110°C, and the temperature is kept for 10 hours;

[0118] S303, preparing a preform on a 30,000-ton hydraulic press, with a deformation amount a2 of 30%, a deformation rate v2 of 10 mm / s, and then grinding the surface of the preform forging;

[0119] Step 4: Forging the final forging using a die forging press:

[0120] S401, use 8mm aluminum silicate insulation cotton and 1mm stainless steel plate to cover the preform;

[0121] S402, after the jacketing treatment, place it in a heating furnace, heat it to 1080°C, and keep it warm for 10 hours;

[0122] S403, forging on a 30,000-ton hydraulic press to prepare final forgings, with a deformation amount a3 of 40% and a deformation rate v3 of 15 mm / s, and grinding the surface of the forgings after final forging;

[0123] Step 5: Critical solution treatment: The critical solution temperature is 1108℃, and the steel is quickly air-cooled after being kept at this temperature for 8 hours. Then, a low-temperature aging treatment is performed at 740℃, and the holding time is 16 hours. The steel is quickly air-cooled after being taken out of the furnace to obtain a large turbine disk forging. The diameter of the large turbine disk forging is Φ890mm.

[0124] The preparation method of Example 2 is substantially the same as that of Example 1, except that:

[0125] The bar size is Φ360×780mm;

[0126] In S202, the temperature is raised to 1128°C and kept warm for 10 hours;

[0127] In S203, the deformation amount a1 of the upset cake is 52%, and the deformation rate v1 is 24 mm / s;

[0128] In S303, the deformation amount a2 is 28% and the deformation rate v2 is 6 mm / s;

[0129] In S403, the deformation amount a3 is 37% and the deformation rate v3 is 20 mm / s;

[0130] The diameter of the large turbine disc forging is Φ890mm.

[0131] The preparation method of Example 3 is substantially the same as that of Example 1, except that:

[0132] The bar size is Φ360×785mm;

[0133] In S202, the temperature is raised to 1140°C and kept warm for 10 hours;

[0134] In S203, the deformation amount a1 of the upset cake is 55%, and the deformation rate v1 is 30 mm / s;

[0135] In S303, the deformation amount a2 is 25% and the deformation rate v2 is 8 mm / s;

[0136] In S403, the deformation amount a3 is 34% and the deformation rate v3 is 16 mm / s;

[0137] In step 5, the critical solution temperature is 1103°C;

[0138] The diameter of the large turbine disc forging is Φ890mm.

[0139] Standard tensile specimens, impact specimens and high-temperature endurance specimens were prepared at the rim of the turbine disk to test the room temperature mechanical properties and high-temperature endurance properties of the turbine disk under different process conditions.

[0140] The microstructure and γ′ phase morphology of the rod of Example 1 are as follows: Figure 1 As shown, Figures 2 to 4 The microstructures and γ′ phase morphologies of the large turbine disk forgings prepared in Examples 1, 2, and 3 are shown in Figure 1. Figures 2 to 4 It can be seen that the large turbine disk forging prepared in the embodiment is homogeneous, and there are a large number of coarse primary γ′ phases and fine tertiary γ′ phases in the matrix. The matrix is ​​a two-phase structure, and the mechanical properties are shown in Tables 3 to 5.

[0141] During the preparation process of the large turbine disk forging of the present invention, the forging is not easy to crack, has good structural uniformity, and the yield rate reaches more than 95%.

[0142] The composition of the embodiment is shown in Table 1 below. The microstructure of the embodiment is a γ+γ′ dual-phase structure, with fine and uniform grains, for example, the grain size is 6-7; the size and volume fraction of the γ′ phase are shown in Table 2 below. In the figure, the matrix structure is fine grains, the black phase is mainly a coarse primary γ′ phase, the matrix is ​​a dual-phase structure, and the scanning figure shows the tertiary γ′ phase morphology.

[0143] Table 1 Chemical composition, wt%

[0144]

[0145] Table 2 Microstructure of turbine disk forgings

[0146]

[0147] Table 3 Partial performance test results

[0148]

[0149] Table 4 Partial performance test results

[0150]

[0151] Table 5 High temperature endurance performance

[0152]

[0153] The inventor has conducted a large number of experimental studies during the research process, and now uses some solutions with poor performance as comparative examples.

[0154] Comparative Example 1

[0155] This comparative example provides a turbine disk forging and a preparation method thereof. The components are shown in Table 1 above. The preparation method is substantially the same as that of Example 1, except that the final forging temperature is 1060°C, and Al+Ti+Nb>7.95%.

[0156] like Figure 5 As shown, the structure of the turbine disk forging of this comparative example is uneven, the grain size is 3 to 7, there are a large number of grains that have not undergone dynamic crystallization in the matrix, the mechanical properties are poor, and the hardness is high, which is not conducive to the subsequent processing and manufacturing of the turbine disk.

[0157] Comparative Example 2

[0158] This comparative example provides a turbine disk forging and a preparation method thereof, the components of which are shown in Table 1 above, and the preparation method is substantially the same as that of Example 1, except that the heat treatment solution temperature is 1080°C and the aging temperature is 780°C.

[0159] like Figure 6 As shown, the structure of the turbine disk forging of this comparative example is uneven, the grain size is 5 to 7, there is no fine tertiary γ′ phase in the matrix after heat treatment, and the mechanical properties are poor.

[0160] Comparative Example 3

[0161] This comparative example provides a turbine disk forging and a preparation method thereof, the components of which are shown in Table 1 above, and the preparation method comprises:

[0162] The Φ360×760mm bar blank with a grain size of 8-level homogeneous crystal was subjected to the first upsetting at 1145℃ with a deformation of 40%; the hydraulic press pressing rate was 20mm / s;

[0163] Continue to perform the second upsetting at 1145°C with a deformation of 45%; the hydraulic press pressing rate is 20 mm / s;

[0164] After the upsetting cake is completed, it is machined and punched, with a hole diameter of Φ60mm;

[0165] Die forging was carried out at 1120°C, with a deformation of 30% and a hydraulic press speed of 15 mm / s;

[0166] Rough machining of die forgings;

[0167] Solution treatment: the forging is kept at 1080℃ for 8 hours and then quickly air-cooled; then aging treatment is carried out at 780℃ for 16 hours, and then quickly air-cooled after being taken out of the furnace to obtain turbine disk forgings;

[0168] The microstructure of the turbine disk forging of this comparative example is as follows: Figure 7 As shown in the figure, it can be seen that the grain size is level 5, there is no fine tertiary γ′ phase in the matrix, and the mechanical properties are poor.

[0169] It can be seen from the comparison of the embodiments and comparative examples that the strength and the sustained fracture time of the turbine disk forgings prepared by the method of the present invention are significantly improved, and the mechanical properties are excellent.

[0170] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a large turbine disk forging, characterized in that: The steps include: Step 1: Smelting to obtain steel ingots; the steel ingots are cut into bars; Step 2: Use a die forging press to upset the cake; Step 3: preparing a preform using a die forging press; Step 4: Forging the final forging by using a die forging press; Step 5: critical solution treatment; Step 6: Low temperature aging treatment to obtain a large turbine disk forging; The components of the large turbine disk forging include, by mass percentage: C: 0.04% to 0.06%, Cr: 13.0% to 15.0%, Co: 9.0% to 11.0%, Mo: 4.5% to 5.50%, Al: 2.60% to 2.80%, Ti: 2.60% to 2.80%, Nb: 2.4% to 2.7%, 7.80%≤(Al+Ti+Nb)≤7.95%, and nickel: balance; The temperature T1 of the upsetting cake in step 2, the temperature T2 of the preform in step 3, and the temperature T3 of the final forging in step 4 meet the following relationship: T1>T2>T3; In step 5, the critical solution treatment temperature is controlled to be Ts=1095+59(X Al -2.6)+13(X Ti -2.6)+18(X Mo -5)+6.5(X Nb -2.6)-12(X Cr -14), where: X Al , X Ti , X Mo , X Nb , X Cr -Mass percentage of the corresponding element*100.

2. The preparation method according to claim 1, characterized in that: The deformation amount a1 of the upset in step 2, the deformation amount a2 of the preform in step 3, and the deformation amount a3 of the final forging in step 4 meet the following relationship: a1>a3>a2.

3. The preparation method according to claim 1, characterized in that: The deformation rate v1 of the upset in step 2, the deformation rate v2 of the preform in step 3, and the deformation rate v3 of the final forging in step 4 meet the following relationship: v1>v3>v2.

4. The preparation method according to claim 1, characterized in that: In step 2, the specific steps of upsetting the cake include: S201, use heat preservation cotton and stainless steel plate to hard cover the rod; S202, after the rod is wrapped, it is placed in a heating furnace and heated to 1120-1145°C for 8-16 hours; S203, pressing the cake on a press.

5. The preparation method according to claim 4, characterized in that: In the step S203 , the deformation amount a1 of the upset cake is 50% to 60%, and the deformation rate v1 is 20 to 30 mm / s.

6. The preparation method according to claim 1, characterized in that: In step 3, the specific steps of using a die forging press to prepare the preform include: S301, use heat preservation cotton and stainless steel plate to hard cover the rod; S302, after the jacketing treatment, the tube is placed in a heating furnace, the temperature is raised to 1110-1120°C, and the temperature is kept for 8-16 hours; S303, preparing a preform on a press.

7. The preparation method according to claim 6, characterized in that: In the above-mentioned S303, the deformation amount a2 is 10% to 30%, and the deformation rate v2 is 6 to 10 mm / s.

8. The preparation method according to claim 1, characterized in that: In step 4, the final forging temperature T3 is 1060-1080°C.

9. A large turbine disk forging, characterized in that: The large turbine disk forging is prepared by the preparation method described in any one of claims 1 to 8.

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