Stainless steel heat treatment method and aero-engine steel part

Abstract

The invention discloses a stainless steel heat treatment method and an aero-engine steel part, and belongs to the technical field of metal material heat treatment, the stainless steel heat treatment method comprises the following steps: S100, carrying out solution treatment on a stainless steel material, heating the stainless steel material to a temperature above all austenitizing temperature, and carrying out heat preservation to form a metallographic structure of lath martensite; s200, the stainless steel material is adjusted, so that carbide and a copper-rich phase are separated out of a matrix, and inverted austenite is formed; and S300, the stainless steel material is subjected to aging treatment, and the plasticity and impact toughness of the stainless steel material are improved. According to the method, the specific adjusting treatment step is added between the solution treatment and the aging treatment, so that the problem that the hardness of a part treated according to a conventional heat treatment process exceeds the design requirement is effectively solved, meanwhile, the impact toughness of the material is remarkably improved by about 38%, and the comprehensive performance and the service reliability of the part made of the material are improved.

Description

Technical Field

[0001] This application relates to the field of heat treatment technology for metallic materials, and in particular, to a method for heat treating stainless steel and a steel component for aero-engines. Furthermore, this application also relates to a stainless steel aero-engine component manufactured using the aforementioned stainless steel heat treatment method. Background Technology

[0002] The information provided in this section is for the purpose of generally presenting the background of this application. To the extent described in this section, the work of the currently named inventors and aspects of the description that may not constitute prior art at the time of filing are neither explicitly nor implicitly considered to be prior art of this application.

[0003] Precipitation hardening stainless steel is a type of high-strength stainless steel that precipitates carbides, nitrides, carbonitrides, and intermetallic compounds through a precipitation hardening process, thereby improving the strength of the steel while maintaining sufficient toughness.

[0004] 0Cr17Ni4Cu4Nb steel is a typical precipitation-hardening stainless steel with excellent comprehensive properties. On the one hand, this alloy has a high Cu content, and after aging treatment, the martensitic matrix precipitates dispersed copper-rich phases, resulting in precipitation hardening and strengthening of the steel. On the other hand, different strength grades can be obtained through heat treatment to meet performance requirements. It is widely used in industries such as offshore platforms and papermaking machinery, and is also widely used in key components of aero-engines, such as fasteners like bolts and nuts.

[0005] A certain type of aerospace component requires a hardness of HRC27-30. After conventional heat treatment according to industry technical standards, the component's hardness reached HRC32-32.5, exceeding the hardness requirements in the design drawings. Furthermore, the impact toughness of the material under conventional heat treatment may be insufficient for some demanding applications (such as load-bearing aerospace fasteners). While the hardness can be reduced through rework, rework carries the risk of structural instability and poses significant quality risks. Summary of the Invention

[0006] In view of at least one of the above technical problems, this application provides a stainless steel heat treatment method that can effectively solve the problem of parts hardness exceeding design requirements after conventional heat treatment by adding a specific adjustment treatment step between solution treatment and aging treatment. At the same time, it significantly improves the impact toughness of the material (by about 38%), thereby improving the overall performance and service reliability of parts manufactured from the material.

[0007] This application also provides a steel component for an aircraft engine, wherein the stainless steel used is treated by the aforementioned stainless steel heat treatment method.

[0008] According to one aspect of this application, a method for heat treating stainless steel is provided, comprising the following steps: S100: Solution treatment of stainless steel materials involves heating the stainless steel material to above the full austenitization temperature and holding it at that temperature to form a lath martensite microstructure. S200: Adjusts stainless steel materials to induce the precipitation of carbides and copper-rich phases in the matrix, forming inverted austenite and achieving microstructural reconstruction; S300: An aging treatment for stainless steel materials to improve their plasticity and impact toughness.

[0009] In some embodiments of this application, the stainless steel material is 0Cr17Ni4Cu4Nb steel. In step S100, the 0Cr17Ni4Cu4Nb steel billet is subjected to solution treatment; in step S200, the 0Cr17Ni4Cu4Nb steel billet is subjected to adjustment treatment; and in step S300, the 0Cr17Ni4Cu4Nb steel billet is subjected to aging treatment.

[0010] In some embodiments of this application, in step S100, the 0Cr17Ni4Cu4Nb steel billet is heated to a first preset temperature, then kept at that temperature for a first preset duration, and then cooled after the heat preservation is completed.

[0011] In some embodiments of this application, in step S200, the 0Cr17Ni4Cu4Nb steel billet is heated to a second preset temperature, then kept at that temperature for a second preset duration, and then cooled after the heat preservation is completed.

[0012] In some embodiments of this application, in step S300, the 0Cr17Ni4Cu4Nb steel billet is heated to a third preset temperature, then kept at that temperature for a third preset duration, and then cooled after the heat preservation is completed.

[0013] In some embodiments of this application, the 0Cr17Ni4Cu4Nb steel after being treated by steps S100 to S300 has a hardness of HRC27 to 30, an impact toughness of 2534 KJ / m2, a tensile strength of 940 MPa, a 0.2% yield strength of 760 MPa, an elongation after fracture of 23%, and a reduction of area of ​​71%.

[0014] In some embodiments of this application, the first preset temperature is 1035℃~1045℃, the first preset duration is 2h~2.5h, and the cooling method is air cooling.

[0015] In some embodiments of this application, the second preset temperature is 811℃~821℃, the second preset duration is 0.5h~1h, and the cooling method is air cooling.

[0016] In some embodiments of this application, the third preset temperature is 615℃~625℃, the third preset duration is 4h~4.5h, and the cooling method is air cooling.

[0017] According to another aspect of this application, an aircraft engine steel component is also provided, wherein the stainless steel used is treated by the aforementioned stainless steel heat treatment method.

[0018] This application has the following beneficial effects: This application's stainless steel heat treatment method involves solution treatment of the stainless steel material, heating it to above the full austenitization temperature and holding it at that temperature. The resulting microstructure is lath martensite with no intergranular precipitates. Alloying elements are dissolved in the matrix and exist in a supersaturated state; a small amount of residual austenite exists between the laths. During the solution treatment holding temperature, δ-ferrite may coexist with austenite and can be retained to room temperature. The stainless steel material is then further treated to induce the precipitation of carbides and copper-rich phases in the matrix, forming inverted austenite. This step is crucial for inducing inverted austenite formation and improving impact toughness. During the treatment, Cr and Nb carbides precipitate in the matrix, accompanied by a large amount of granular copper-rich phase, providing a certain degree of dispersion strengthening. The treatment can adjust the martensitic transformation initiation point (M) of the material. S This is because the precipitated carbides and copper-rich phases consume austenite stabilizing elements in the matrix. Finally, the stainless steel material undergoes aging treatment, which significantly impacts its properties and directly determines its final performance. After aging treatment, martensite undergoes reverse austenite transformation in microregions where austenite stabilizing elements are relatively abundant, forming inverted austenite. This inverted austenite, while maintaining the material's strength and hardness, can significantly absorb energy, effectively improving the material's plasticity and impact toughness.

[0019] The steel components for aero-engines in this application also possess the aforementioned beneficial effects. Furthermore, it effectively solves the problem of unqualified part hardness, precisely controlling the hardness range of 0Cr17Ni4Cu4Nb parts to meet design requirements and avoid rework and the associated risks of structural instability. Significantly improved impact toughness: The most prominent advantage of this method is the improvement in the material's impact toughness from 1837 KJ / m under conventional processes. 2 Increased to 2534 KJ / m 2The improvement is as high as 38%, which greatly enhances the reliability and safety of parts under dynamic loads or impact environments. Excellent comprehensive mechanical properties: While ensuring that tensile strength (≥930MPa) and yield strength (≥725MPa) meet the requirements, elongation after fracture (≥16%) and reduction of area (≥50%) are also improved, achieving an ideal combination of high strength, good plasticity, and high impact toughness. Simultaneously, the process is stable and reliable: the three-step heat treatment process parameters provided by this invention are clear, highly operable, and have good repeatability, making it suitable for the industrial production of steel parts for aero-engines.

[0020] Of course, any product implementing this application does not necessarily need to achieve all the advantages described above simultaneously. In addition to the purposes, features, and advantages described above, this application also has other purposes, features, and advantages. The following will provide a more detailed description of this application with reference to figures. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the metallographic structure of stainless steel material after heat treatment according to a preferred embodiment of this application; Figure 2 This is a schematic diagram of the metallographic structure of stainless steel material after conventional heat treatment. Detailed Implementation

[0022] The following description provides specific application scenarios and requirements for this specification, intended to enable those skilled in the art to make and use the contents of this specification. Various partial modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of this specification. Therefore, this specification is not limited to the embodiments shown, but rather to the widest scope consistent with the claims.

[0023] A method for heat treating stainless steel, comprising the following steps: S100: Solution treatment of stainless steel materials involves heating the stainless steel material to above the full austenitization temperature and holding it at that temperature to form a lath martensite microstructure. S200: Adjusts stainless steel materials to induce the precipitation of carbides and copper-rich phases in the matrix, forming inverted austenite and achieving microstructural reconstruction; S300: An aging treatment for stainless steel materials to improve their plasticity and impact toughness.

[0024] This application's stainless steel heat treatment method involves solution treatment of the stainless steel material, heating it to above the full austenitization temperature and holding it at that temperature. The resulting microstructure is lath martensite with no intergranular precipitates. Alloying elements are dissolved in the matrix and exist in a supersaturated state; a small amount of residual austenite exists between the laths. During the solution treatment holding period, δ-ferrite may coexist with austenite and can be retained to room temperature. The stainless steel material is then subjected to a conditioning treatment to induce the precipitation of carbides and copper-rich phases in the matrix, forming inverted austenite. This step is crucial for inducing inverted austenite formation and improving impact toughness. During the conditioning treatment, Cr and Nb carbides precipitate in the matrix, accompanied by the precipitation of a large amount of granular copper-rich phase, which provides a certain degree of dispersion strengthening. The conditioning treatment can adjust the martensitic transformation initiation point (MS point) of the material because the precipitated carbides and copper-rich phases consume austenite stabilizing elements in the matrix. Finally, the stainless steel material undergoes aging treatment, which has a significant impact on the material's properties and directly determines its final performance. After aging treatment, martensite undergoes reverse transformation to austenite in microregions where austenite stabilizing elements are relatively enriched, forming inverted austenite. This inverted austenite, while ensuring the material's strength and hardness, can significantly absorb energy, effectively improving the material's plasticity and impact toughness.

[0025] It should be noted that while some existing technologies disclose a two-stage aging process following a single solution treatment, this approach essentially involves over-aging without altering the martensitic matrix. Instead, it reduces the material's strength by coarsening the strengthening phases. The purpose of solution treatment is to fully dissolve the alloying elements into the austenite, forming a supersaturated solid solution. During subsequent cooling, the supercooled austenite transforms into supersaturated martensite. Holding the material at a relatively high temperature of 640-660℃ for an extended period (two aging stages effectively prolong the total aging time) causes the copper-rich phases and carbides precipitated during aging to coarsen, reducing their quantity and increasing their spacing, according to the Ostwald ripening mechanism. This results in a significant decrease in strength.

[0026] To address the challenge of simultaneously improving material strength and hardness while enhancing its plasticity and impact toughness, this application proposes a novel approach centered on microstructure reconstruction. This involves introducing inverted austenite through solution treatment and conditioning to reconstruct the material's matrix structure. Combined with a lower aging temperature, this avoids excessive coarsening of the strengthening phases, achieving an ideal balance of high strength, good plasticity, and high impact toughness. The purpose of solution treatment is to fully dissolve the alloying elements into the austenite, forming a supersaturated solid solution. During subsequent cooling, the supercooled austenite transforms into supersaturated martensite. When the material is subjected to conditioning treatment at 811-821℃ (above Ac1 temperature), partial austenitization occurs, and the martensite formed by solid solution is partially transformed into austenite. At the same time, alloying elements are enriched in the austenite. During the subsequent air cooling process, some of the austenite enriched with austenite stabilizing elements is retained to room temperature, forming stable inverted austenite. Inverted austenite is a "soft phase," which reduces the hardness of the material to meet manufacturing requirements. At the same time, it can also significantly absorb energy through this inverted austenite, effectively improving the material's plasticity and impact toughness.

[0027] Preferably, the stainless steel material is 0Cr17Ni4Cu4Nb steel. In step S100, the 0Cr17Ni4Cu4Nb steel billet is subjected to solution treatment; in step S200, the 0Cr17Ni4Cu4Nb steel billet is subjected to adjustment treatment; and in step S300, the 0Cr17Ni4Cu4Nb steel billet is subjected to aging treatment.

[0028] In this preferred embodiment, in step S100, the 0Cr17Ni4Cu4Nb steel billet is heated to a first preset temperature, then held at that temperature for a first preset duration, and then cooled. In step S200, the 0Cr17Ni4Cu4Nb steel billet is heated to a second preset temperature, then held at that temperature for a second preset duration, and then cooled. In step S300, the 0Cr17Ni4Cu4Nb steel billet is heated to a third preset temperature, then held at that temperature for a third preset duration, and then cooled.

[0029] It should be noted that a certain type of aerospace component is made of 0Cr17Ni4Cu4Nb steel, with a required hardness of HRC27-30. After conventional heat treatment according to industry technical standards, the component's hardness reached HRC32-32.5, exceeding the hardness requirements in the design drawings. Furthermore, the impact toughness level of the material under conventional heat treatment may be insufficient for some high-requirement applications (such as load-bearing aerospace fasteners). Although the hardness can be reduced to HRC27-30 through rework by increasing the aging temperature, the Ac1 phase transformation temperature of 0Cr17Ni4Cu4Nb steel is 670℃. This poses a risk of microstructural instability during rework, resulting in significant quality issues. Moreover, simply increasing the aging temperature has limited and uncontrollable improvement on impact toughness.

[0030] Optionally, in steps S100 to S300, an air furnace is used for heating treatment. In order to improve the air cooling efficiency of the material, a fan can be used to increase the cooling speed in each step.

[0031] Among them, the 0Cr17Ni4Cu4Nb steel after processing in steps S100 to S300 has a hardness of HRC27 to 30 and an impact toughness of 2534 KJ / m. 2 The tensile strength is 940 MPa, the 0.2% yield strength is 760 MPa, the elongation after fracture is 23%, and the reduction of area is 71%.

[0032] Understandably, to address the issue of excessive hardness and insufficient impact toughness in 0Cr17Ni4Cu4Nb parts after conventional heat treatment to meet more demanding service conditions, this invention proposes an innovative heat treatment method. This method breaks with traditional steps by introducing a specific adjustment treatment after solution treatment, followed by aging treatment. Parts processed using this heat treatment method can have their hardness precisely controlled within HRC27–30. More importantly, their impact toughness is significantly improved compared to conventional solution aging processes (an improvement of approximately 38%, from 1837 KJ / m²). 2 Increased to 2534 KJ / m 2 This greatly improves the reliability and safety of parts under dynamic loads or impact environments; at the same time, it ensures that the strength and plasticity meet the design requirements, and the comprehensive mechanical properties are excellent. While ensuring that the tensile strength (≥930MPa) and yield strength (≥725MPa) meet the requirements, the elongation after fracture (≥16%) and reduction of area (≥50%) are also improved, achieving an ideal combination of high strength, good plasticity and high impact toughness.

[0033] In some embodiments, the first preset temperature is 1035℃~1045℃, the first preset duration is 2h~2.5h, and the cooling method is air cooling. The second preset temperature is 811℃~821℃, the second preset duration is 0.5h~1h, and the cooling method is air cooling. The third preset temperature is 615℃~625℃, the third preset duration is 4h~4.5h, and the cooling method is air cooling.

[0034] Because certain aero-engine parts made of 0Cr17Ni4Cu4Nb steel require a hardness of HRC27-30, after heat treatment using conventional process parameters, the hardness of the parts reached HRC32-32.5, exceeding the hardness requirements in the design drawings. Furthermore, the impact toughness of stainless steel under conventional heat treatment processes may be insufficient for certain demanding applications (such as load-bearing aerospace fasteners). Although the hardness can be reduced to HRC27-30 through rework, the Ac1 phase transformation temperature of 0Cr17Ni4Cu4Nb steel is 670℃, which poses a risk of microstructural instability and significant quality defects during rework. Moreover, simply increasing the aging temperature has limited and uncontrollable improvement on impact toughness.

[0035] This application introduces a specific conditioning treatment after solution treatment, followed by aging treatment. Parts processed using this heat treatment method can have their hardness precisely controlled within HRC27-30 to meet design requirements, avoiding rework and the associated risks of structural instability. More importantly, its impact toughness is significantly improved compared to conventional solution aging processes, increasing the material's impact toughness from 1837 KJ / m2 under conventional processes to 2534 KJ / m2, an increase of 38%. This greatly improves the reliability and safety of parts under dynamic loads or impact environments. At the same time, while ensuring that tensile strength (≥930MPa) and yield strength (≥725MPa) meet the requirements, elongation after fracture (≥16%) and reduction of area (≥50%) are also improved, achieving an ideal combination of high strength, good plasticity, and high impact toughness, effectively ensuring that strength and plasticity meet design requirements.

[0036] It should be noted that solution treatment refers to heating the material to above its full austenitization temperature and holding it at that temperature for a certain period of time, allowing the precipitated phases to dissolve back into the matrix, and then cooling it to room temperature at a rate exceeding the critical cooling rate to form supersaturated martensite. The solution treatment temperature for 0Cr17Ni4Cu4Nb steel is selected to be around 1040℃. The microstructure after solution treatment is typical lath martensite, with no precipitated phases between the lath grains. The alloying elements are dissolved in the matrix and exist in a supersaturated state. A small amount of retained austenite exists between the laths. During the solution treatment holding period, δ-ferrite may coexist with austenite and can be retained to room temperature.

[0037] The aging treatment temperature is selected between 615℃ and 625℃, as the final aging temperature has a significant impact on the material's properties and directly determines its final performance. During aging, martensite precipitates ε-Cu, carbides, and inverted austenite. ε-Cu is distributed randomly in the matrix as fine, spherical particles, interacting strongly with dislocations to achieve precipitation hardening. As the aging temperature increases, the size of ε-Cu increases, the precipitation hardening effect weakens, but the material's plasticity increases.

[0038] The temperature for step S200 adjustment treatment is selected to be between 811℃ and 821℃. During the adjustment treatment, Cr and Nb carbides precipitate in the matrix, accompanied by the precipitation of a large number of granular copper-rich phases, which plays a certain role in dispersion strengthening. The adjustment treatment can adjust the martensitic transformation initiation point (M) of the material. S This is because the precipitated carbides and copper-rich phases consume austenite stabilizing elements in the matrix. After aging treatment, please refer to... Figure 1 In microregions where austenite stabilizing elements are relatively abundant, martensite undergoes reverse transformation to austenite, forming inverted austenite. This inverted austenite, while ensuring the material's strength and hardness, can significantly absorb energy, becoming a key factor in improving the material's plasticity and impact toughness.

[0039] Example 1 Step 1: Solution treatment is performed on the 0Cr17Ni4Cu4Nb steel billet. The heating temperature is 1040℃, the holding time is 2h~2.5h, and the cooling method is air cooling. Step 2: Adjust the 0Cr17Ni4Cu4Nb steel billet. The heating temperature is 811℃~821℃, the holding time is 0.5h~1h, and the cooling method is air cooling (this step is the core of inducing the formation of inverted austenite and improving impact toughness). Step 3: Aging treatment is performed on the 0Cr17Ni4Cu4Nb steel billet. The heating temperature is 620℃, the holding time is 4h~4.5h, and the cooling method is air cooling.

[0040] Comparative Example 1 Step 1: Solution treatment is performed on the 0Cr17Ni4Cu4Nb steel billet. The heating temperature is 1040℃, the holding time is 2h~2.5h, and the cooling method is air cooling. Step 2: Aging treatment is performed on the 0Cr17Ni4Cu4Nb steel billet. The heating temperature is 811℃~821℃, the holding time is 4h~4.5h, and the cooling method is air cooling.

[0041] Please refer to the attached instruction manual. Figure 1 and 2Through experimental comparison, the properties of 0Cr17Ni4Cu4Nb materials treated with conventional heat treatment and those treated with the improved heat treatment of this invention are shown in Table 1 below. The data in the table show that the heat treatment method of this invention precisely controls the hardness within the HRC 27-30 range while achieving a significant improvement in impact toughness (an increase of approximately 38%, 1837 KJ / m). 2 Increased to 2534 KJ / m 2 The elongation after fracture and the reduction of area are also improved simultaneously, and the overall performance is significantly better than that of conventional processes.

[0042] Table 1 Comparison of experimental parameters between Example 1 and Comparative Example 1

[0043] Because a certain type of aerospace component requires a hardness of HRC27-30, after solution treatment and aging as shown in Comparative Example 1 using conventional process parameters, the component's hardness reached HRC32-32.5 (aging temperature 640℃), exceeding the hardness requirements of the design drawings. Simultaneously, the impact toughness level of the material under conventional solution treatment and aging processes (impact toughness at aging temperature 640℃ is 1837 KJ / m) is also higher. 2 For certain demanding applications (such as load-bearing aerospace fasteners), this may be insufficient. Although the hardness can be reduced to HRC27-30 through rework by increasing the aging temperature, the Ac1 phase transformation temperature of 0Cr17Ni4Cu4Nb steel is 670℃, which poses a risk of microstructural instability and significant quality issues during rework. Furthermore, simply increasing the aging temperature has limited and uncontrollable improvement on impact toughness. The stainless steel heat treatment method and its toughness control mechanism in this application, through a combination of "solution treatment + adjustment + aging," not only effectively solves the problem of parts exceeding design requirements after conventional heat treatment, but also significantly improves the material's impact toughness (by approximately 38%), thereby enhancing the overall performance and service reliability of parts manufactured from this material.

[0044] In summary, this application's stainless steel heat treatment method achieves a significant improvement in impact toughness through an innovative mechanism: it introduces a key conditioning step, differing from conventional single solution treatment, thus overcoming the bottlenecks of traditional processes. The conditioning process, by controlling the distribution of alloying elements, promotes the formation of inverted austenite in specific regions during subsequent aging. This soft and tough phase effectively hinders crack propagation and absorbs impact energy, which is the core mechanism for improving impact toughness.

[0045] At the same time, it also achieved comprehensive performance optimization and innovation: through the process combination of "solution + adjustment + aging", it not only accurately controlled the hardness of 0Cr17Ni4Cu4Nb steel to be stable at HRC27~30, solving the problem of unqualified hardness, but also significantly improved plasticity (by about 11%) and impact toughness (by about 38%), breaking through the bottleneck of traditional processes that are difficult to balance or significantly improve toughness when reducing hardness, and achieving the best balance of strength, plasticity and toughness.

[0046] According to another aspect of this application, an aircraft engine steel component is also provided, wherein the stainless steel used is treated by the aforementioned stainless steel heat treatment method.

[0047] In some embodiments, a certain type of nut material used in a certain type of aerospace component is 0Cr17Ni4Cu4Nb, with target mechanical properties as follows: hardness HRC27~30, tensile strength ≥930MPa, yield strength ≥725MPa, elongation after fracture ≥16%, reduction of area ≥50%, and impact toughness ≥2000KJ / m. 2 The stainless steel heat treatment method described in this application can achieve a hardness of HRC29, with a tensile strength of 940 MPa, a yield strength of 760 MPa, an elongation after fracture of 23%, a reduction of area of ​​73%, and an impact toughness of 2534 KJ / m. 2 This achieves an ideal combination of high strength, good plasticity, and high impact toughness while meeting design requirements for hardness. The specific steps are as follows: Solution treatment: Hold at 1040℃ for 2 hours and 15 minutes, then remove from the furnace and air cool.

[0048] Adjustment process: Hold at 816℃ for 45 minutes, then remove from the furnace and air cool.

[0049] Aging time: Hold at 620℃ for 4 hours and 15 minutes, then air cool after removal from the furnace.

[0050] The steel components for aero-engines in this application also possess the aforementioned beneficial effects. Furthermore, it effectively solves the problem of unqualified part hardness, precisely controlling the hardness range of 0Cr17Ni4Cu4Nb parts to meet design requirements and avoid rework and the associated risks of structural instability. Significantly improved impact toughness: The most prominent advantage of this method is the improvement in the material's impact toughness from 1837 KJ / m under conventional processes. 2 Increased to 2534 KJ / m 2The improvement is as high as 38%, which greatly enhances the reliability and safety of parts under dynamic loads or impact environments. Excellent comprehensive mechanical properties: While ensuring that tensile strength (≥930MPa) and yield strength (≥725MPa) meet the requirements, elongation after fracture (≥16%) and reduction of area (≥50%) are also improved, achieving an ideal combination of high strength, good plasticity, and high impact toughness. Simultaneously, the process is stable and reliable: the three-step heat treatment process parameters provided by this invention are clear, highly operable, and have good repeatability, making it suitable for the industrial production of steel parts for aero-engines.

[0051] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0052] It should be understood that in the foregoing description of the embodiments in this specification, various features are combined in a single embodiment, drawing, or description for the purpose of simplifying the description and aiding in the understanding of a feature. However, this does not mean that the combination of these features is necessary, and those skilled in the art may readily identify some of the devices as separate embodiments when reading this specification. That is, the embodiments in this specification can also be understood as an integration of multiple secondary embodiments. It is also valid when each secondary embodiment contains fewer than all the features of a single foregoing disclosed embodiment.

[0053] Each patent, patent application, publication of the patent application, and other materials such as articles, books, specifications, publications, documents, articles, etc., cited herein may be incorporated by reference. The entire contents used for all purposes, except for any history of prosecution documents associated with it, that may be inconsistent with or conflict with this document, or that may have a limiting effect on the widest extent of the claims, are now or hereafter associated with this document. For example, in the event of any inconsistency or conflict between the description, definition, and / or use of terms associated with any of the included materials and the terms, description, definition, and / or used in connection with this document, the terms used herein shall prevail.

[0054] Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments described in this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can implement the applications described in this specification by adopting alternative configurations based on the embodiments in this specification. Therefore, the embodiments in this specification are not limited to the embodiments precisely described in the application. For those skilled in the art, several improvements, modifications, or changes can be made without departing from the principles of this application, and the above technical features can also be combined in an appropriate manner; these improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other occasions without modification, should all be considered as protection of this application.

Claims

1. A method for heat treating stainless steel, characterized in that, It includes the following steps: S100: Solution treatment of stainless steel materials involves heating the stainless steel material to above the full austenitization temperature and holding it at that temperature to form a lath martensite microstructure. S200: Adjusts stainless steel materials to induce the precipitation of carbides and copper-rich phases in the matrix, forming inverted austenite and achieving microstructural reconstruction; S300: An aging treatment for stainless steel materials to improve their plasticity and impact toughness.

2. The stainless steel heat treatment method according to claim 1, characterized in that, The stainless steel material is 0Cr17Ni4Cu4Nb steel. In step S100, the 0Cr17Ni4Cu4Nb steel billet is subjected to solution treatment; in step S200, the 0Cr17Ni4Cu4Nb steel billet is subjected to adjustment treatment; in step S300, the 0Cr17Ni4Cu4Nb steel billet is subjected to aging treatment.

3. The stainless steel heat treatment method according to claim 2, characterized in that, In step S100, the 0Cr17Ni4Cu4Nb steel billet is heated to a first preset temperature, then held for a first preset time, and then cooled.

4. The stainless steel heat treatment method according to claim 2, characterized in that, In step S200, the 0Cr17Ni4Cu4Nb steel billet is heated to the second preset temperature, then held for the second preset time, and then cooled.

5. A method for heat treating stainless steel according to claim 2, characterized in that, In step S300, the 0Cr17Ni4Cu4Nb steel billet is heated to the third preset temperature, then held for the third preset time, and then cooled.

6. A method for heat treating stainless steel according to claim 2, characterized in that, After treatment steps S100 to S300, the 0Cr17Ni4Cu4Nb steel has a hardness of HRC27-30 and an impact toughness of 2534 KJ / m. 2 The tensile strength is 940 MPa, the 0.2% yield strength is 760 MPa, the elongation after fracture is 23%, and the reduction of area is 71%.

7. A method for heat treating stainless steel according to claim 3, characterized in that, The first preset temperature is 1035℃~1045℃, the first preset duration is 2h~2.5h, and the cooling method is air cooling.

8. A method for heat treating stainless steel according to claim 4, characterized in that, The second preset temperature is 811℃~821℃, the second preset duration is 0.5h~1h, and the cooling method is air cooling.

9. A method for heat treating stainless steel according to claim 5, characterized in that, The third preset temperature is 615℃~625℃, the third preset duration is 4h~4.5h, and the cooling method is air cooling.

10. A steel component for an aircraft engine, characterized in that, The stainless steel used in aero-engine steel components is treated using the stainless steel heat treatment method as described in any one of claims 1-9.

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