Rolling method for superalloy

Abstract

A rolling method for a difficult-to-deform superalloy, comprising: holding a round billet of the superalloy at a temperature of 1100 to 1200°C for 1 to 3 hours; and then rolling the heat-soaked round billet of the superalloy, wherein the rolling deformation mode is: round-oval-round. An over-aging treatment is employed during the blooming of a superalloy rolling billet, and the heating temperature and heating time of the superalloy round billet are strictly controlled to prevent prolonged heat soaking, so as to alter the grain boundary strengthening phases, improve plasticity, and obtain a rolling billet with a uniform grain structure; the blooming specification of the superalloy is changed from a square billet as used in the prior art to a round billet, and by designing a reasonable reduction amount and deformation mode, a per-pass rolling reduction, and by controlling the rolling speed during the process and the finishing rolling temperature, the high-temperature thermoplastic range of the superalloy is fully utilized, thereby alleviating the problem of large temperature drop during the conversion of the billet from square to round and the problem of easy cracking of difficult-to-deform superalloys; this rolling method is particularly suitable for superalloys with high Al+Ti+Nb content.

Description

Rolling methods for high-temperature alloys Technical Field

[0001] This invention belongs to the field of hot working technology of metallic materials. Specifically, this invention relates to a rolling method for a difficult-to-deform high-temperature alloy. Background Technology

[0002] Aero engines are hailed as the "crown jewel" due to their high industrial technical requirements. Among these, aero engine fasteners, as the vital link within this "jewel," also possess unique performance and technical requirements compared to other fasteners due to the high-pressure, high-temperature, and high-strength operating environment, demanding higher safety and reliability. Therefore, the development of aero engine fasteners is currently being studied as a fundamental science, with substantial investment in research and development.

[0003] The main fasteners used in aero engines include various types of bolts, keyed studs, self-locking nuts, threaded inserts, pins, and pipe fittings. These fasteners are primarily made of high-temperature alloys (such as GH141, GH4698, GH738, GH99, and GH188).

[0004] High-temperature alloys are extremely sensitive to temperature, have a narrow hot working window, and experience rapid temperature drop, which is a major reason why it is difficult to obtain an ideal microstructure. Current rolling mills operate at high speeds, resulting in large deformations and significant core temperature rises, which easily lead to inconsistencies in the properties and microstructure of the rolled material. Simultaneously, the rapid temperature drop at both ends of the billet makes it prone to bite-in problems during rolling, leading to scrap.

[0005] Therefore, high-temperature alloy fasteners that are difficult to deform are particularly hard to obtain, and even when they are, their quality is often inconsistent. High-temperature alloys characterized by high Al+Ti+Nb content, for example, those containing a total Al, Ti, and Nb content of at least approximately 4.5% by weight, have a high content of strengthening phases and strong resistance to deformation, making them more difficult to deform.

[0006] Therefore, the successful rolling of difficult-to-deform high-temperature alloys is an urgent problem to be solved in this field. Summary of the Invention

[0007] Purpose of the invention

[0008] In view of the problems existing in the prior art described in the background section above, the object of the present invention is to provide a method for rolling high-temperature alloys.

[0009] Technical solution

[0010] To achieve the above-mentioned objectives, the present invention includes the following technical solutions:

[0011] Option 1: A rolling method for a high-temperature alloy, wherein the rolling method includes first holding a round billet of the high-temperature alloy at a temperature of about 1100 to about 1200°C for about 1 to about 3 hours; and then rolling the held-temperature round billet of the high-temperature alloy, wherein the rolling deformation is: circle-ellipse-circle, wherein...

[0012] The rolling start temperature T 开 To be no lower than approximately 1100℃,

[0013] The final rolling temperature T 终 Not lower than T 开 -100℃, preferably not lower than T 开 -80℃

[0014] During the rolling process, the deformation of the round billet's cross-section from a circle to an ellipse ranges from about 10% to about 30%; and

[0015] During the rolling process, the total deformation is in the range of about 40% to about 60%.

[0016] Option 2: According to the high-temperature alloy rolling method described in Option 1 above, the ratio of the major axis to the minor axis of the ellipse is in the range of about 1.2 to about 1.5.

[0017] Option 3: The high-temperature alloy rolling method according to Option 1 or 2 above, wherein the rolling speed is in the range of about 0.2 to about 0.6 m / s.

[0018] Option 4: The high-temperature alloy rolling method according to any one of Options 1 to 3 above, wherein the diameter of the circular cross-section of the high-temperature alloy billet is in the range of about 120 to about 150 mm.

[0019] Option 5: The high-temperature alloy rolling method according to any one of Options 1 to 4 above, wherein the longitudinal length of the high-temperature alloy round billet is in the range of about 2.85 to about 3.10 meters.

[0020] Option 6: The high-temperature alloy rolling method according to any one of Options 1 to 5 above, wherein the chemical composition of the high-temperature alloy by weight percentage is:

[0021] C (carbon): less than 0.3% by weight

[0022] Cr (chromium): about 13 to about 21% by weight

[0023] P (phosphorus): less than 0.015% by weight,

[0024] S (sulfur): less than 0.002% by weight

[0025] Al (aluminum): from about 0.2% to about 2.3% by weight

[0026] Ti (titanium): approximately 0.75% to approximately 3.2% by weight

[0027] Nb: approximately 1.9 to approximately 5.5% by weight

[0028] Mo (Mo): Approximately 3.3% by weight or less,

[0029] The balance is Fe (iron) and / or Ni (nickel) and unavoidable impurities.

[0030] Option 7: A high-temperature alloy rolling method according to any one of Options 1 to 6 above, wherein the total content of the elements Al, Ti and Nb contained in the high-temperature alloy is not less than about 4.5% by weight.

[0031] Option 8: A high-temperature alloy rolling method according to any one of Options 1 to 7 above, wherein the chemical composition of the high-temperature alloy by weight percentage is:

[0032] C: Approximately 0.3% by weight or less,

[0033] Cr: about 15 to about 17% by weight

[0034] P: Approximately 0.015% by weight or less,

[0035] S: Approximately 0.002% by weight or less,

[0036] Al: from about 1.65 to about 2.3% by weight

[0037] Ti: approx. 2.4% to approx. 3.2% by weight

[0038] Nb: approximately 2 to approximately 2.5% by weight

[0039] Ni: approximately 30 to approximately 35% by weight

[0040] The balance is Fe and unavoidable impurities.

[0041] Option 9: A high-temperature alloy rolling method according to any one of Options 1 to 7 above, wherein the chemical composition of the high-temperature alloy is as follows (weight percentage):

[0042] C: Approximately 0.08% by weight or less.

[0043] Cr: about 17 to about 21% by weight

[0044] P: Approximately 0.015% by weight or less,

[0045] S: Approximately 0.002% by weight or less,

[0046] Al: about 0.2% to about 0.8% by weight

[0047] Ti: about 0.75 to about 1.15% by weight

[0048] Nb: Approximately 5% to approximately 5.5% by weight

[0049] Mo: about 2.8 to about 3.3% by weight

[0050] Ni: approximately 50 to approximately 55% by weight

[0051] The balance is Fe and unavoidable impurities.

[0052] Option 10: A high-temperature alloy rolling method according to any one of Options 1 to 7 above, wherein the chemical composition of the high-temperature alloy by weight percentage is:

[0053] C: about 0.03 to about 0.07% by weight

[0054] Cr: about 13 to about 16% by weight

[0055] P: Approximately 0.015% by weight or less,

[0056] S: Approximately 0.002% by weight or less,

[0057] Al: about 1.45 to about 1.8% by weight

[0058] Ti: about 2.35 to about 2.75% by weight

[0059] Nb: approximately 1.9% to approximately 2.2% by weight

[0060] Mo: about 2.8 to about 3.2% by weight

[0061] The balance is Ni and unavoidable impurities.

[0062] Option 11: A high-temperature alloy rolling method according to any one of claims 1 to 10, wherein the rolling is performed using a conjugate rolling process.

[0063] Option 12: A method for rolling high-temperature alloys according to any one of claims 1 to 11, wherein the rolling method is a longitudinal rolling method.

[0064] Technical effect

[0065] The high-temperature alloy rolling method of the present invention has several advantages over existing rolling methods, including:

[0066] (1) When the high-temperature alloy billet is rolled, an over-aging treatment is adopted. The heating temperature and heating time of the high-temperature alloy round billet are strictly controlled to prevent long-term heat preservation, so as to change the grain boundary strengthening phase, improve plasticity, and obtain a billet with uniform grain structure.

[0067] (2) The billet specifications of the high-temperature alloy are changed from the square billet of the existing technology (e.g., 155 square) to the round billet of the present invention (e.g., 120-150 round), and the rolling is carried out in sequence using elliptical and circular die shapes. The deformation mode is changed from "square-flat-round" to "round-elliptical-round". By designing reasonable deformation amount and deformation mode, deformation amount of each rolling pass, controlling the rolling speed and final rolling temperature, the high-temperature thermoplastic range of the high-temperature alloy is fully utilized, and the problem of large temperature drop in the billet from square to round and easy cracking of difficult-to-deform high-temperature alloy is completely improved. The billet temperature is increased by about 10 to about 20°C.

[0068] (3) The rolling method of the present invention is particularly suitable for high-temperature alloys characterized by high Al+Ti+Nb. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely for the purpose of aiding understanding of this invention and should not be considered as specific limitations on this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Process parameters in the following embodiments that are not specifically specified are generally performed under conventional conditions.

[0070] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. The term "about" as used in this invention indicates that the number it modifies may fluctuate within ±20%, ±15%, ±10%, ±5%, or ±2% of that number. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0071] This invention provides a method for rolling high-temperature alloys. The preferred method for rolling high-temperature alloys is longitudinal rolling.

[0072] On one hand, the high-temperature alloy rolling method of the present invention includes holding the high-temperature alloy billet at a temperature of about 1100 to about 1200°C, for example, about 1120°C, about 1140°C, about 1150°C, about 1160°C or about 1180°C, for about 1 to about 3 hours, for example, about 1.5 hours, about 2 hours or about 2.5 hours.

[0073] Here, the holding temperature of the billet should not be too high, for example, it should not exceed about 1200°C, otherwise it is easy to cause the rolled high-temperature alloy to overheat and crack; nor should it be too low, for example, it should not be lower than about 1100°C, otherwise the initial temperature of the rolled high-temperature alloy will be too low, which will easily lead to a low final rolling temperature, rolling failure or cracking of the rolled piece.

[0074] In addition, the holding time of the round blank should not be too long, for example, not more than about 3 hours, otherwise the grains in the high-temperature alloy will grow severely; nor should it be too short, for example, not less than about 1 hour, otherwise the high-temperature alloy will not be fully burned and cannot be formed.

[0075] On the other hand, the high-temperature alloy rolling method of the present invention further includes rolling the heat-insulated high-temperature alloy round billet after the above-mentioned heat preservation process, and the rolling deformation mode is: circle-ellipse-circle.

[0076] Here, in the high-temperature alloy rolling method of the present invention, the rolling temperature should not be too low, for example, the initial rolling temperature T. 开 The temperature should not be lower than approximately 1100°C, for example, approximately 1120°C or approximately 1180°C, and the final rolling temperature T of the rolling process should be... 终 It should not be lower than T 开 -100℃, preferably not lower than T 开 The rolling temperature should be kept below -80℃; otherwise, rolling failure or cracking of the rolled piece may occur. To ensure that the rolling temperature is controlled within the above range, online compensation heating can be appropriately used for adjustment when necessary.

[0077] In a preferred embodiment of the high-temperature alloy rolling method of the present invention, during the rolling process, the deformation of the cross-section of the round billet from a circle to an ellipse is generally controlled within the range of about 10% to about 30%, for example, about 15%, about 20%, or about 25%. Here, the deformation should not be too large or too small, for example, it should not exceed about 30%, otherwise it is easy to cause rolling failure; nor should it be less than about 10%, otherwise the deformation will be insufficient, resulting in uneven grain structure in the high-temperature alloy.

[0078] In the aforementioned rolling process from round billet to elliptical billet, the ratio of the major axis to the minor axis of the elliptical cross-section of the elliptical billet is preferably in the range of about 1.2 to about 1.5, for example, about 1.25, about 1.35, or about 1.45. This ratio should not be too large or too small; for example, it should not be lower than about 1.2, otherwise the deformation will be insufficient, easily leading to the high-temperature alloy failing to meet performance requirements. It should also not be greater than about 1.5, otherwise the deformation will be too large, which may cause core cracking of the material. Furthermore, this is also limited by equipment capabilities; ordinary equipment cannot easily achieve such a large deformation resistance.

[0079] In another preferred embodiment of the high-temperature alloy rolling method of the present invention, during the rolling process, the total deformation is in the range of about 40% to about 60%, for example, about 45%, about 50%, or about 55%. Here, the total deformation should not be too large or too small, for example, it should not exceed about 60%, otherwise it is easy to cause excessive temperature rise in the core of the high-temperature alloy, abnormal grain growth, or cracking; nor should it be less than about 40%, otherwise it is easy to cause uneven grain structure in the high-temperature alloy.

[0080] The "deformation" described in the above paragraph refers to the change in the cross-sectional area of ​​the rolled piece during the rolling process. Specifically, it is the percentage obtained by dividing the difference in cross-sectional area of ​​the rolled piece before and after the rolling deformation by the original cross-sectional area of ​​the rolled piece.

[0081] In the high-temperature alloy rolling method of the present invention, the rolling speed is generally not limited and is usually determined by the capacity of the rolling equipment. However, in some preferred embodiments of the present invention, it is generally controlled within the range of about 0.2 to about 0.6 m / s, for example, about 0.3 m / s, about 0.4 m / s, or about 0.5 m / s. Here, the rolling speed should not be too fast or too slow, for example, it should not exceed about 0.6 m / s, otherwise it may cause cracking of the core of the bar; nor should it be lower than about 0.2 m / s, otherwise it may cause cracking of the surface of the bar.

[0082] In the high-temperature alloy rolling method of the present invention, there is no particular limitation on the diameter of the circular cross section of the high-temperature alloy billet. However, in some other preferred embodiments of the high-temperature alloy rolling method of the present invention, due to the requirements of the production equipment, the diameter of the circular cross section of the high-temperature alloy billet is usually set in the range of about 120 to about 150 mm, for example, about 125 mm, about 130 mm, about 135 mm, about 140 mm or about 145 mm.

[0083] On the other hand, there is no particular limitation on the longitudinal length of the high-temperature alloy billet. However, in some preferred embodiments of the high-temperature alloy rolling method of the present invention, the longitudinal length of the high-temperature alloy billet is set in the range of about 2.85 to about 3.10 meters, for example, about 2.90 meters, about 2.95 meters, about 3.00 meters or about 3.05 meters, due to the requirements of the production equipment.

[0084] In the high-temperature alloy rolling method of the present invention described above, the preferred chemical composition weight percentage of the high-temperature alloy is:

[0085] C: 0 to about 0.3% by weight, for example about 0.1% by weight or about 0.2% by weight.

[0086] Cr: from about 13 to about 21% by weight, for example about 15% by weight, about 17% by weight, or about 19% by weight.

[0087] P: 0 to about 0.015% by weight, for example about 0.005% by weight, about 0.008% by weight, or about 0.010% by weight.

[0088] S: 0 to about 0.002% by weight, for example about 0.0005% by weight, about 0.0006% by weight, about 0.0008% by weight, about 0.001% by weight, or about 0.0015% by weight.

[0089] Al: from about 0.2 to about 2.3% by weight, for example about 0.5% by weight, about 0.8% by weight, about 1.1% by weight, about 1.4% by weight, about 1.7% by weight, or about 2.0% by weight.

[0090] Ti: from about 0.75 to about 3.2% by weight, for example about 1.0% by weight, about 2.0% by weight, or about 3.0% by weight.

[0091] Nb: from about 1.9% to about 5.5% by weight, for example about 2% by weight, 3% by weight, 4% by weight or about 5% by weight.

[0092] Mo: 0 to about 3.3% by weight, for example about 1% by weight, 2% by weight or about 3% by weight.

[0093] The balance is Fe and / or Ni and unavoidable impurities.

[0094] In a particularly preferred embodiment of the high-temperature alloy rolling method of the present invention, the total content of the elements Al, Ti and Nb contained in the high-temperature alloy is not less than about 4.5% by weight. This is because the higher the content of Al, Ti and Nb, the higher the content of the strengthening phase, the greater the deformation resistance, and the more difficult the high-temperature alloy is to deform.

[0095] In a specific exemplary preferred embodiment of the high-temperature alloy rolling method of the present invention, the chemical composition weight percentage of the high-temperature alloy can be:

[0096] C: 0 to approximately 0.3% by weight

[0097] Cr: about 15 to about 17% by weight

[0098] P: 0 to approximately 0.015% by weight

[0099] S: 0 to about 0.002% by weight

[0100] Al: from about 1.65 to about 2.3% by weight

[0101] Ti: approx. 2.4% to approx. 3.2% by weight

[0102] Nb: approximately 2 to approximately 2.5% by weight

[0103] Ni: approximately 30 to approximately 35% by weight

[0104] The balance is Fe and unavoidable impurities.

[0105] In another specific exemplary preferred embodiment of the high-temperature alloy rolling method of the present invention, the chemical composition weight percentage of the high-temperature alloy can be:

[0106] C: 0 to approximately 0.08% by weight

[0107] Cr: about 17 to about 21% by weight

[0108] P: 0 to approximately 0.015% by weight

[0109] S: 0 to about 0.002% by weight

[0110] Al: 0.2 to about 0.8% by weight

[0111] Ti: 0.75 to about 1.15% by weight

[0112] Nb: Approximately 5% to approximately 5.5% by weight

[0113] Mo: about 2.8 to about 3.3% by weight

[0114] Ni: 50 to 55% by weight

[0115] The balance is Fe and unavoidable impurities.

[0116] In another exemplary preferred embodiment of the high-temperature alloy rolling method of the present invention, the chemical composition weight percentage of the high-temperature alloy can be:

[0117] C: about 0.03 to about 0.07% by weight

[0118] Cr: about 13 to about 16% by weight

[0119] P: 0 to approximately 0.015% by weight

[0120] S: 0 to about 0.002% by weight

[0121] Al: about 1.45 to about 1.8% by weight

[0122] Ti: about 2.35 to about 2.75% by weight

[0123] Nb: approximately 1.9% to approximately 2.2% by weight

[0124] Mo: about 2.8 to about 3.2% by weight

[0125] The balance is Ni and unavoidable impurities.

[0126] Finally, in the high-temperature alloy rolling method of the present invention, the rolling process employs a conjugate rolling process. The conjugate rolling process allows for more uniform die wear.

[0127] The present invention will now be described in further detail with reference to specific embodiments and comparative examples.

[0128] Examples 1 to 3:

[0129] High-temperature alloy steel ingots containing the elemental contents shown in Table 1 are used for radial forging to form round billets with a diameter of approximately 125 mm. Heating and holding are performed at the temperatures and times shown in Table 1. The billets are then cut and rolled, specifically longitudinal rolling. The rolling deformation is circular-elliptical-circular.

[0130] Comparative Examples 1 to 3:

[0131] High-temperature alloy steel ingots containing the elemental contents shown in Table 1 are used for radial forging to form square billets with a side length of approximately 155 mm. Heating and holding at the temperatures and times shown in Table 1 are then performed. The billets are then cut and rolled, specifically longitudinal rolling. The rolling deformation is square-flat-round.

[0132] Table 1

[0133] As can be seen from the rolling process results of Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention, the high-temperature alloy can be rolled smoothly using the rolling method of the present invention. However, when using the existing technology to start rolling a square billet, even if the process parameters are the same as those of the present invention, the final rolling result is severe surface cracking, or even scrapping.

[0134] In addition, the properties of the high-temperature alloys rolled by Examples 1 to 3 of the present invention, such as room temperature tensile, high temperature tensile and high temperature creep properties, all comply with the relevant provisions in national standards (e.g. GB / T14992, 14993 or 14994, etc.).

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions claimed by the present invention.

Claims

1. A rolling method for a high-temperature alloy, preferably a longitudinal rolling method, characterized in that, The rolling method includes first holding the high-temperature alloy billet at a temperature of 1100 to 1200°C for 1 to 3 hours; and then rolling the held high-temperature alloy billet, wherein the rolling deformation is: circle-ellipse-circle, where... The rolling start temperature T 开 The temperature should not be lower than 1100℃. The final rolling temperature T 终 Not lower than T 开 -100℃, preferably not lower than T 开 -80℃ During the rolling process, the deformation of the cross-section of the billet from a circle to an ellipse is in the range of 10% to 30%. and During the rolling process, the total deformation is in the range of 40% to 60%.

2. The high-temperature alloy rolling method according to claim 1, characterized in that, The ratio of the major axis to the minor axis of the ellipse is in the range of 1.2 to 1.5; and / or The rolling speed is in the range of 0.2 to 0.6 m / s.

3. The high-temperature alloy rolling method according to claim 1, characterized in that, The diameter of the circular cross-section of the high-temperature alloy billet is in the range of 120 to 150 mm.

4. The high-temperature alloy rolling method according to claim 1, characterized in that, The longitudinal length of the high-temperature alloy billet is in the range of 2.85 to 3.10 meters.

5. The high-temperature alloy rolling method according to claim 1, characterized in that, The chemical composition of the high-temperature alloy, by weight percentage, is as follows: C: 0 to 0.3% by weight Cr: 13 to 21% by weight P: 0 to 0.015% by weight S: 0 to 0.002% by weight Al: 0.2 to 2.3% by weight Ti: 0.75 to 3.2% by weight Nb: 1.9 to 5.5% by weight Mo: 0 to 3.3% by weight The balance is Fe and / or Ni and unavoidable impurities.

6. The high-temperature alloy rolling method according to claim 5, characterized in that, The total content of Al, Ti, and Nb in the high-temperature alloy is not less than 4.5% by weight.

7. The method for rolling high-temperature alloys according to any one of claims 1 to 6, characterized in that, The chemical composition of the high-temperature alloy, by weight percentage, is as follows: C: 0 to 0.3% by weight Cr: 15 to 17% by weight P: 0 to 0.015% by weight S: 0 to 0.002% by weight Al: 1.65 to 2.3% by weight Ti: 2.4 to 3.2% by weight Nb: 2 to 2.5% by weight Ni: 30 to 35% by weight The balance is Fe and unavoidable impurities.

8. The method for rolling high-temperature alloys according to any one of claims 1 to 6, characterized in that, The chemical composition of the high-temperature alloy, by weight percentage, is as follows: C: 0 to 0.08% by weight Cr: 17 to 21% by weight P: 0 to 0.015% by weight S: 0 to 0.002% by weight Al: 0.2 to 0.8% by weight Ti: 0.75 to 1.15% by weight Nb: 5 to 5.5% by weight Mo: 2.8 to 3.3% by weight Ni: 50 to 55% by weight The balance is Fe and unavoidable impurities.

9. The method for rolling high-temperature alloys according to any one of claims 1 to 6, characterized in that, The chemical composition of the high-temperature alloy, by weight percentage, is as follows: C: 0.03 to 0.07% by weight Cr: 13 to 16% by weight P: 0 to 0.015% by weight S: 0 to 0.002% by weight Al: 1.45 to 1.8% by weight Ti: 2.35 to 2.75% by weight Nb: 1.9 to 2.2% by weight Mo: 2.8 to 3.2% by weight The balance is Ni and unavoidable impurities.

10. The method for rolling high-temperature alloys according to any one of claims 1 to 6, characterized in that, The rolling process employs a conjugate rolling process.

Images