Nickel-based alloy spring and method of making the same

Abstract

The present application relates to a nickel-based alloy spring and a preparation method thereof. The preparation method comprises: raw material smelting, multiple smelting of raw material powder and casting forming to obtain an alloy ingot. Forging treatment, the alloy ingot is heated to 1120-1180 DEG C and kept, and then forging processing is carried out to obtain a blank. Drawing processing, the blank after forging is drawn into a finished wire through multiple passes. Hydrogen removal treatment, the finished wire after drawing is heated to 300-350 DEG C in the furnace and kept, and then the finished wire is cooled to room temperature with the furnace. Heat treatment, the finished wire after hydrogen removal treatment is sequentially subjected to solid solution treatment and aging treatment. Spring making and secondary heat treatment, the finished wire after heat treatment is coiled into a spring, and the spring is subjected to secondary heat treatment. Through the reasonable setting of the process links such as smelting, forging, drawing, hydrogen removal, heat treatment, spring making and secondary heat treatment, the spring has stable mechanical properties, excellent resistance to seawater and H2S corrosion, and meets the toughness requirement in low temperature environment, and meets the use requirement in SUBSEA extreme environment.

Description

Technical Field

[0001] This invention relates to the field of spring manufacturing technology, and in particular to a nickel-based alloy spring and its preparation method. Background Technology

[0002] The Subsuasion environment is characterized by extreme conditions such as high pressure, low temperature, high seawater corrosivity, and the risk of H2S corrosion, placing stringent demands on the mechanical properties, corrosion resistance, and structural stability of equipment components. Springs, as key elastic elements in Subsuasion equipment, directly determine the operational reliability and service life of the equipment. Nickel-based alloy 718 (UNS N07718), as a precipitation-hardening alloy, possesses excellent corrosion resistance, low-temperature toughness, and comprehensive mechanical properties, and is widely used in aerospace, energy, and other extreme environment fields, theoretically making it suitable for the Subsuasion environment.

[0003] However, the existing technology for manufacturing SUBSEA springs using nickel-based alloy 718 presents the following key problems: First, conventional smelting and processing techniques make it difficult to precisely control the internal structure of the material, resulting in large fluctuations in the mechanical properties of the finished springs, which cannot stably match the load requirements of the SUBSEA environment; Second, key mechanical parameters such as the hardness, yield strength, and tensile strength of the finished wire are difficult to precisely control within a reasonable range, resulting in either insufficient strength leading to deformation or excessive brittleness leading to breakage; Third, hydrogen elements are easily retained inside the material, which can easily cause hydrogen-induced cracking under the combined effects of SUBSEA high pressure and low temperature, seawater corrosion, and H2S corrosion, seriously affecting the service life of the springs. Summary of the Invention

[0004] One objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a nickel-based alloy spring. To solve the above-mentioned technical problems, this invention adopts the following technical solution:

[0005] A method for preparing a nickel-based alloy spring includes the following steps: Raw material smelting involves smelting raw material powder multiple times and casting it into alloy ingots. The multiple smelting processes include at least one vacuum induction smelting and one vacuum arc remelting. Forging process involves heating the alloy ingot to 1120℃~1180℃ and holding it at that temperature before forging to obtain the billet. The final forging temperature is greater than or equal to 930℃, and the forging deformation is greater than or equal to 25%. Wire drawing process involves drawing the forged billet into finished wire through multiple drawing passes, and performing intermediate annealing between adjacent drawing processes, followed by cooling the finished wire to room temperature. Hydrogen removal treatment involves heating the finished wire material after drawing to 300℃~350℃ in a furnace and holding it at that temperature, then allowing the finished wire material to cool to room temperature with the furnace. Heat treatment involves sequentially performing solution treatment and aging treatment on the dehydrogenated finished filaments. Spring making and secondary heat treatment: The finished wire material after heat treatment is wound into springs using special equipment. The springs are then subjected to secondary heat treatment so that the Rockwell hardness of the springs after secondary heat treatment is less than or equal to 35HRC.

[0006] In one embodiment, during the dehydrogenation treatment step, the finished filament is kept at a temperature of 300°C to 350°C for a period of 4 to 6 hours.

[0007] In one embodiment, the process of solution treatment of the dehydrogenated finished filament in the heat treatment step is as follows: heat the finished filament to 927°C~1010°C, keep it at that temperature for at least 1 hour, and then air cool it to room temperature.

[0008] In one embodiment, the process of aging the solution-treated finished filament in the heat treatment step is as follows: First, heat the finished filaments in a furnace to 718℃~760℃ and keep them at that temperature for at least 8 hours. Then, cool them in the furnace to 621℃~649℃, keep them at that temperature for at least 8 hours, and then air cool them to room temperature.

[0009] In one embodiment, the process of performing secondary heat treatment on the manufactured spring in the spring-making and secondary heat treatment steps is as follows: heating the spring to 550°C~750°C and holding it at that temperature for 1h~3h, and then air-cooling it to room temperature.

[0010] In one embodiment, during the forging process, the alloy ingot is held at 1120°C to 1180°C for 2 hours to 4 hours. After forging, allow the billet to cool to room temperature.

[0011] In one embodiment, during the wire drawing process, the deformation amount per pass is controlled to not exceed 15%. The drawing process is protected by inert gas.

[0012] In one embodiment, the multiple melting steps in the raw material melting process also include a vacuum electroslag remelting.

[0013] In one embodiment, during the raw material smelting step, the vacuum level is controlled to be less than or equal to 1 × 10⁻⁶. -3 Pa.

[0014] In one embodiment, the method for preparing the nickel-based alloy spring further includes the following steps: Quality inspection includes at least -20℃ low temperature impact test, seawater corrosion resistance test and H2S corrosion resistance test. The -20℃ low temperature impact test is performed by taking a forged square sample from the forged billet. The forged square sample is subjected to the -20℃ low temperature impact test after solution treatment and aging treatment. Seawater corrosion resistance test and H2S corrosion resistance test were conducted on the springs after secondary heat treatment.

[0015] Another object of the present invention is to provide a nickel-based alloy spring, which is prepared by the method for preparing a nickel-based alloy spring as described in any of the preceding claims.

[0016] As can be seen from the above technical solution, the present invention has at least the following advantages and positive effects: In this invention, multiple vacuum melting, remelting, and precision forging processes, combined with segmented drawing and intermediate annealing, effectively refine the grain size of the nickel-based alloy 718, ensuring uniform chemical composition and dense microstructure. This lays the foundation for the spring's excellent performance and helps improve the material's toughness and fatigue resistance. A targeted dehydrogenation process helps completely remove residual hydrogen from the material, preventing hydrogen-induced cracking under the high pressure, low temperature, seawater corrosion, and H2S corrosion environment of Subsia. Combined with the inherent corrosion resistance of nickel-based alloy 718, this significantly extends the spring's service life in extreme environments. By rationally setting the process parameters for solution treatment and aging treatment, and clearly defining the upper limit of the hardness after secondary heat treatment following spring fabrication, the key mechanical properties of the finished wire are precisely controlled within a preset range. This ensures the spring's toughness in low-temperature environments and its performance stability after forming, perfectly matching the mechanical loads and low-temperature usage requirements of the Subsia environment. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for preparing a nickel-based alloy spring according to an embodiment of the present invention. Detailed Implementation

[0018] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0019] In the description of this application, it should be understood that, in the embodiments shown in the accompanying drawings, the indications of direction or positional relationships (such as up, down, left, right, front, and back, etc.) are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. These descriptions are appropriate when these elements are in the positions shown in the accompanying drawings. If the description of the positions of these elements changes, these directional indications also change accordingly.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] Please see Figure 1 As shown, the method for preparing a nickel-based alloy spring according to an embodiment of the present invention includes the following steps: S10, raw material smelting, involves repeatedly smelting raw material powder and casting it into alloy ingots.

[0022] The aforementioned multiple melting processes include at least one vacuum induction melting and one vacuum arc remelting. For example, in one embodiment, the melting of the raw material powder can employ a dual melting process of vacuum induction melting and vacuum arc remelting. Controlling this dual melting process helps ensure the uniform chemical composition of the alloy ingot and that the content of impurity elements meets standard requirements.

[0023] Alternatively, in other embodiments, the multiple melting processes may further include a vacuum electroslag remelting. That is, the melting of the raw material powder can employ a triple melting process of vacuum induction melting + vacuum arc remelting + vacuum electroslag remelting. Controlling this triple melting process helps ensure the uniform chemical composition of the alloy ingot and that the content of impurity elements meets standard requirements.

[0024] Optionally, in the raw material smelting step, the vacuum degree of each smelting process is controlled to be less than or equal to 1×10⁻⁶. -3 Pa helps ensure the purity and uniformity of raw materials.

[0025] like Figure 1 As shown, the preparation method further includes: S20, forging treatment, in which the alloy ingot is heated to 1120℃~1180℃ and held at that temperature, and then forged to obtain a billet. The final forging temperature is greater than or equal to 930℃, and the forging deformation is greater than or equal to 25%. This helps to refine the grains and eliminate defects in the as-cast structure.

[0026] Optionally, a segmented heat preservation method can be used during the forging process to ensure that the final forging temperature is not lower than 930°C, which can help ensure uniform material deformation.

[0027] In one embodiment, during the forging process, the alloy ingot is held at 1120°C to 1180°C for 2 to 4 hours. After forging, the billet is cooled to room temperature.

[0028] like Figure 1 As shown, the preparation method further includes: S30, wire drawing process, in which the forged billet is drawn into finished wire through multiple drawing passes, and intermediate annealing is performed between adjacent drawing processes, and then the finished wire is cooled to room temperature.

[0029] Optionally, during the wire drawing process, the deformation per pass should be controlled to not exceed 15%. Strict control of the wire diameter tolerance is required during drawing. For example, the diameter of all finished wires used for springs can be produced according to the above deviation to help ensure spring assembly accuracy and avoid assembly failures and performance fluctuations caused by dimensional deviations.

[0030] Optionally, the annealing process between adjacent drawing processes can be as follows: the annealing temperature is controlled at 980℃~1020℃, and the temperature is held for 1h~2h before air cooling to room temperature.

[0031] In the drawing process, inert gas protection is used, such as argon or nitrogen, which helps to prevent oxidation of the wire surface.

[0032] See Figure 1 As shown, the preparation method further includes: S40, dehydrogenation treatment, in which the finished wire after drawing is heated in a furnace to 300℃~350℃ and kept at that temperature, and then the finished wire is cooled to room temperature with the furnace.

[0033] Optionally, in the dehydrogenation treatment step, the finished filament can be kept at 300℃~350℃ for 4 h~6 h. This dehydrogenation treatment helps to completely remove residual hydrogen from the material, preventing hydrogen-induced cracking under the combined high pressure, low temperature, and H2S corrosion conditions of SUBSEA.

[0034] See Figure 1 The preparation method further includes: S50, heat treatment, in which the dehydrogenated finished filament is subjected to solution treatment and aging treatment in sequence.

[0035] The process for solution treatment of the dehydrogenated finished filament can be as follows: heat the finished filament to 927℃~1010℃, keep it at that temperature for at least 1 hour, and then air cool it to room temperature.

[0036] The process for aging the finished filaments after solution treatment can be as follows: first, heat the finished filaments in a furnace to 718℃~760℃ and keep them at that temperature for at least 8 hours, then cool them in the furnace to 621℃~649℃, keep them at that temperature for at least 8 hours, and then air cool them to room temperature.

[0037] In this embodiment, by controlling the process parameters of solution treatment and aging treatment, wherein the aging treatment adopts a two-stage process, it can help to accurately control the key mechanical properties of the finished wire within a preset range. At the same time, it is beneficial to ensure the toughness of the spring in a low-temperature environment and the performance stability after molding, which is conducive to perfectly matching the mechanical load and low-temperature use requirements of the SUBSEA environment.

[0038] See Figure 1 The preparation method further includes: S60, spring forming and secondary heat treatment, wherein the heat-treated finished wire is wound into a spring using specialized equipment. Optionally, the specialized equipment can be a CNC spring winding machine, which has a high degree of automation and high manufacturing precision.

[0039] Furthermore, the manufactured spring undergoes a secondary heat treatment, resulting in a Rockwell hardness of less than or equal to 35 HRC.

[0040] The secondary heat treatment process can be as follows: heat the spring to 550℃~750℃ and hold it for 1h~3h, then air cool it to room temperature.

[0041] In this embodiment, by precisely controlling the process parameters of solution treatment and aging treatment, and clarifying the upper limit of the hardness of the secondary heat treatment after spring making, it is helpful to accurately control the key mechanical properties of the finished wire within the preset range. At the same time, it is beneficial to ensure the toughness of the spring in low-temperature environment and the performance stability after molding, which is conducive to perfectly matching the mechanical load and low-temperature use requirements of the SUBSEA environment.

[0042] In some embodiments of the present invention, the preparation method of the nickel-based alloy spring further includes the following step: quality inspection. The quality inspection includes at least a -20°C low-temperature impact test, a seawater corrosion resistance test, and a H2S corrosion resistance test.

[0043] For example, the -20℃ low-temperature impact energy test is performed by cutting a forged square sample from the forged billet. The forged square sample is then subjected to solution treatment and aging treatment before being subjected to the -20℃ low-temperature impact energy test.

[0044] Seawater corrosion resistance testing and H2S corrosion resistance testing are conducted on springs after secondary heat treatment, respectively. For example, the testing must be performed according to relevant marine engineering standards. Seawater corrosion resistance testing can employ a salt spray test (neutral salt spray, test cycle 1000h). H2S corrosion resistance testing can employ a hydrogen sulfide corrosion test (simulating actual SUBSEA working conditions) to ensure the service life of the springs under the target corrosive environment.

[0045] Optionally, quality inspection may also include the following tests: 1. Appearance inspection: The surface of the finished wire and spring should be smooth and free from defects such as cracks, scratches, and oxide scale.

[0046] 2. Dimensional Inspection: High-precision measuring instruments are used to inspect the diameter of the finished wire and key dimensions of the spring to ensure compliance with tolerance requirements. 3. Mechanical property testing: Sampling locations shall be in accordance with the standards of each classification society and applicable standards. The sample condition shall be solution treated and aged. The yield strength of the finished wire shall be 680MPa~850MPa, the tensile strength shall be 1050MPa~1200MPa, and the Rockwell hardness shall be 26.5HRC~31.5HRC.

[0047] 4. Metallographic testing: Inspect the metallographic structure of the finished wire to ensure that the grain size grade is not lower than level 7. 5. Chemical composition analysis: The chemical composition of the finished filament is tested using methods such as spectral analysis to ensure that it meets the standard requirements.

[0048] 6. Third-party witnessed testing: The classification society witnesses the chemical composition and measured HRC of the finished filament in the solution-treated state; after the finished filament has undergone solution treatment and aging, the classification society witnesses the yield strength, tensile strength and HRC testing process and results.

[0049] 7. Non-destructive testing: We use non-destructive testing technologies such as ultrasonic and magnetic particle testing to detect internal and surface defects in materials to ensure product quality.

[0050] In this invention, by setting up quality tests that include specific performance verification for SUBSEA low temperature, high seawater corrosion and H2S corrosion, as well as a strict third-party witnessed testing process, it is beneficial to ensure the consistency and reliability of product quality and to ensure that the product meets the environmental requirements of SUBSEA.

[0051] In one embodiment of the present invention, a nickel-based alloy 718 spring suitable for the SUBSEA environment, manufactured using the above-described preparation method, is also provided. This spring, based on nickel-based alloy 718, is used in SUBSEA equipment at the FPSO H614 / H615 engineering center. The finished wire has a yield strength of 680MPa~850MPa, a tensile strength of 1050MPa~1200MPa, and a Rockwell hardness of 26.5HRC~31.5HRC. The wire diameter conforms to the above tolerance, and the surface is smooth and defect-free; the metallographic grain size grade is not lower than 7, and the hardness after secondary heat treatment after spring manufacturing is not higher than 35HRC. It passes the -20℃ low-temperature impact test, meets the standards for seawater corrosion resistance and H2S corrosion resistance, and all key performance indicators have been witnessed and tested by a classification society.

[0052] The present invention will be further described in detail below with reference to the specific spring manufacturing process. The following embodiments are based on the requirements of the FPSO H614 / H615 project and are carried out in accordance with the technical standards.

[0053] Example 1: S10, Raw material smelting: Nickel-based alloy 718 ingots are prepared using a multi-stage smelting process combining vacuum induction melting and vacuum arc remelting. The vacuum degree during vacuum induction melting is controlled at 5 × 10⁻⁶. -4 Pa, melting temperature approximately 1300℃, holding time approximately 2 hours. Vacuum degree of vacuum arc remelting is controlled at 8×10⁻⁶. -4 Pa. This helps ensure that the chemical composition of the ingot is uniform and that the content of impurity elements meets the standard requirements.

[0054] S20, forging treatment: The ingot is heated to 1150℃, held for 3 hours, and then forged. The final forging temperature is controlled at 950℃, and the forging deformation is 30%. After forging, it is air-cooled to room temperature. This helps to eliminate defects in the as-cast structure and refine the grains.

[0055] S30, Wire Drawing Process: The forged billet is drawn into a finished wire with a diameter of 7.3mm through 8 passes. The deformation in each pass is controlled within 12%, and an intermediate annealing treatment is performed between adjacent drawing processes (annealing temperature 1000℃, held for 1.5h and then air-cooled). Argon gas protection is used during the drawing process to avoid oxidation of the wire surface. The wire diameter tolerance is strictly controlled according to the above deviation, and the final measured wire diameter is 7.32mm (meeting the above deviation requirement).

[0056] S40, Dehydrogenation treatment: The drawn filament is placed in a heat treatment furnace and kept at 320°C for 5 hours, and then cooled to room temperature with the furnace to complete the dehydrogenation treatment.

[0057] S50, Heat Treatment: The finished filaments after hydrogen removal treatment undergo solution treatment and aging treatment sequentially. The solution treatment temperature is approximately 980℃, held for about 1 hour, and then air-cooled. The aging treatment employs a two-stage process: first, holding at 740℃ for about 8 hours, then furnace-cooling to 630℃ at a rate of 38℃ / h, holding for about 8 hours, and then air-cooling to room temperature. Heat treatment process documents and record reports are prepared simultaneously and submitted for review.

[0058] S60, Spring Forming and Secondary Heat Treatment: The finished wire is wound into compression springs using a CNC spring coiling machine. After spring forming, a secondary heat treatment is performed, which involves holding the spring at 580℃ for 2 hours and then air-cooling it to room temperature. The measured spring hardness after the secondary heat treatment is 33HRC (meeting the requirement of ≤35HRC).

[0059] Regarding quality inspection: a) Appearance inspection: Visual inspection combined with a magnifying glass is used to check the finished wire and spring surfaces. The surfaces are smooth and free of defects such as cracks, scratches, and oxide scale.

[0060] b) Dimensional inspection: The wire diameter was measured with a micrometer, and the average value of multiple measurements was 7.32 mm, which meets the upper deviation requirement; the spring mean diameter, free height and other key dimensions were measured with calipers, and all met the design requirements.

[0061] c) Mechanical property testing: Samples were taken from the ends of the wire according to the classification society standards, and the samples were in a solution-treated and aged state. The test results showed a yield strength of 760 MPa, a tensile strength of 1120 MPa, and a Rockwell hardness of 29.2 HRC, all within the preset range.

[0062] d) Low-temperature impact performance testing: Forged square samples were cut from the forged billet. After the above-mentioned solution treatment and aging treatment, the forged square samples were subjected to a -20℃ low-temperature impact energy test. The measured impact energy was 62J, and the data was recorded and archived.

[0063] e) Metallographic testing: Samples were taken for metallographic analysis. The grain size grade was 8 (≥7), and the structure was uniform and dense.

[0064] f) Chemical composition analysis: The chemical composition of the wire was detected by a spectrometer. The content of Ni was 52.3%, Cr was 19.1%, and Nb was 5.2%. The contents of other elements met the requirements of the classification society and the project technical agreement.

[0065] g) Third-party witnessed testing: The classification society witnesses the entire process of chemical composition testing (spectral analysis) and measured HRC (25.1 HRC) of the finished filament in solution-treated state. The classification society also witnesses the testing process for yield strength, tensile strength, and HRC of the filament after solution treatment and aging, confirming the authenticity and validity of the test data.

[0066] h) Non-destructive testing: Ultrasonic testing was used to detect internal defects in the wire, and magnetic particle testing was used to detect surface defects in the spring. No abnormalities were found.

[0067] i) Corrosion performance testing: A neutral salt spray test (720h) was conducted according to GB / T 10125-2021, and no obvious corrosion spots were found on the sample surface. An H2S corrosion test (simulating SUBSEA conditions) was conducted according to NACE TM0177-2016, and the corrosion rate was less than 0.01mm / a, meeting the corrosion resistance requirements.

[0068] The nickel-based alloy 718 springs prepared by the above process meet all the performance requirements of the SUBSEA environment and can be used in related underwater equipment of the FPSO H614 / H615 engineering center.

[0069] Example 2: S10, Raw material smelting: Nickel-based alloy 718 ingots are prepared using a three-stage smelting process: vacuum induction melting, vacuum arc remelting, and vacuum electroslag remelting. The vacuum level for each smelting process is controlled to be less than or equal to 1×10⁻⁶. - ³Pa, which helps ensure the purity and uniformity of raw materials.

[0070] S20, forging process: The ingot is heated to 1180℃, held for 2.5 hours, and then forged. The final forging temperature is controlled at 980℃, and the forging deformation is 35%. After forging, it is water-cooled to room temperature.

[0071] S30, Wire Drawing Process: The forged billet is drawn into 8mm diameter finished wire through 10 passes. The deformation in each pass is controlled within 10%, the intermediate annealing temperature is 1020℃, and it is held at that temperature for 1 hour before air cooling. Nitrogen protection is used during the drawing process, and the diameter is executed according to the above deviation.

[0072] S40, Dehydrogenation treatment: The drawn filament is placed in a heat treatment furnace and kept at 350°C for 4 hours, and then cooled to room temperature with the furnace to complete the dehydrogenation treatment.

[0073] S50, Heat Treatment: The finished filaments after hydrogen removal treatment are subjected to solution treatment and aging treatment in sequence. The solution treatment temperature is approximately 1010℃, held at this temperature for about 1 hour, and then air-cooled. The aging treatment involves first holding at 760℃ for about 8 hours, then furnace-cooling to 649℃ and holding at this temperature for 8 hours, followed by air-cooling to room temperature.

[0074] S60, Spring Forming and Secondary Heat Treatment: The finished wire is coiled into a torsion spring using a CNC spring coiling machine. After spring formation, a secondary heat treatment is performed. The process is as follows: heat treatment at 590℃ for 1.5 hours, followed by air cooling to room temperature. The measured hardness is 34HRC (meets the requirement of ≤35HRC).

[0075] Regarding quality inspection: The appearance is free of defects, and the dimensions meet requirements; yield strength is 820 MPa, tensile strength is 1180 MPa, hardness is 30.5 HRC; low-temperature impact energy at -20℃ is 58 J; grain size is grade 7; chemical composition meets standards; witnessed testing by the classification society is qualified; non-destructive testing shows no abnormalities; resistance to seawater corrosion (no significant corrosion after 720 hours of salt spray) and resistance to H2S corrosion (corrosion rate 0.008 mm / a) meet standards. The spring prepared in this embodiment also meets the requirements for use in the SUBSEA environment, and the wire diameter and spring structure can be adjusted according to specific equipment needs.

[0076] The nickel-based alloy spring and its preparation method of this invention, through multiple vacuum melting, remelting and precision forging processes, combined with segmented drawing and intermediate annealing, effectively refines the grain size of the nickel-based alloy 718 material, ensuring the uniformity of the material's chemical composition and the density of its microstructure, laying the foundation for the excellent performance of the spring; the grain size grade is not lower than level 7, significantly improving the material's toughness and fatigue resistance.

[0077] The nickel-based alloy spring and its preparation method in this invention have a targeted dehydrogenation treatment process to completely remove residual hydrogen from the material, effectively avoiding hydrogen-induced cracking in the SUBSEA high-pressure, low-temperature, seawater corrosion synergy and H2S corrosion environment. Combined with the corrosion resistance of the nickel-based alloy 718 itself, the service life of the spring in extreme environments is greatly improved.

[0078] The nickel-based alloy spring and its preparation method of this invention, by precisely controlling the process parameters of solution treatment and aging treatment, and clearly defining the upper limit of the hardness of the secondary heat treatment after spring making, ensures that the key mechanical properties of the finished wire are precisely controlled within the preset range (yield strength 680MPa~850MPa, tensile strength 1050MPa~1200MPa, hardness 26HRC~34HRC). This is beneficial to ensuring the toughness of the spring in low-temperature environments and the performance stability after forming, and is conducive to perfectly matching the mechanical load and low-temperature use requirements of the SUBSEA environment.

[0079] The nickel-based alloy spring and its preparation method in this invention strictly control the wire drawing diameter to the upper deviation, and combined with comprehensive appearance and size inspection, which helps to ensure the spring assembly accuracy and avoid assembly failures and performance fluctuations caused by size deviations.

[0080] The nickel-based alloy spring and its preparation method of this invention establish a quality inspection system that includes low-temperature impact energy testing at -20℃, seawater corrosion resistance testing, and H2S corrosion resistance testing. It also introduces third-party witness testing by classification societies and covers key indicators such as chemical composition, mechanical properties, corrosion resistance, and low-temperature performance. This helps ensure the reliability and traceability of product quality and is conducive to meeting the environmental use requirements of SUBSEA.

[0081] The nickel-based alloy spring and its preparation method of this invention ensure that the spring has stable mechanical properties, excellent resistance to seawater corrosion and H2S corrosion by precisely controlling the parameters and testing standards of each process step, while also meeting the toughness requirements in low-temperature environments and satisfying the usage requirements of the SUBSEA extreme environment.

[0082] The above embodiments are merely illustrative examples of structures. The structures in each embodiment are not fixed combinations. In the absence of structural conflicts, the structures in multiple embodiments can be arbitrarily combined and used.

[0083] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is illustrative and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for preparing a nickel-based alloy spring, characterized in that, Includes the following steps: Raw material smelting involves repeatedly smelting raw material powder and casting it into an alloy ingot. The multiple smelting processes include at least one vacuum induction smelting and one vacuum arc remelting. Forging process involves heating the alloy ingot to 1120℃~1180℃ and holding it at that temperature before forging to obtain the billet. The final forging temperature is greater than or equal to 930℃, and the forging deformation is greater than or equal to 25%. Wire drawing process involves drawing the forged billet into finished wire through multiple drawing passes, and performing intermediate annealing between adjacent drawing processes, followed by cooling the finished wire to room temperature. Hydrogen removal treatment involves heating the finished wire after drawing to 300℃~350℃ in a furnace and holding it at that temperature. After that, the finished wire is cooled to room temperature in the furnace. Heat treatment involves sequentially performing solution treatment and aging treatment on the dehydrogenated finished filaments. Spring making and secondary heat treatment: The finished wire material after heat treatment is wound into springs using special equipment. The springs are then subjected to secondary heat treatment so that the Rockwell hardness of the springs after secondary heat treatment is less than or equal to 35HRC.

2. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the dehydrogenation treatment step, the finished filament is kept at a temperature of 300℃~350℃ for a period of 4 h~6 h.

3. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the heat treatment step, the process of solution treatment of the dehydrogenated finished filament is as follows: heat the finished filament to 927℃~1010℃, keep it at that temperature for at least 1 hour, and then air cool it to room temperature.

4. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the heat treatment step, the process of aging the solution-treated finished filament is as follows: First, heat the finished filaments in a furnace to 718℃~760℃ and keep them at that temperature for at least 8 hours. Then, cool them in the furnace to 621℃~649℃, keep them at that temperature for at least 8 hours, and then air cool them to room temperature.

5. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the spring-making and secondary heat treatment steps, the process of performing secondary heat treatment on the manufactured spring is as follows: heating the spring to 550℃~750℃ and holding it at that temperature for 1h~3h, and then air-cooling it to room temperature.

6. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the forging process, the holding time of the alloy ingot at 1120℃~1180℃ is 2h~4h. After forging, allow the billet to cool to room temperature.

7. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the wire drawing process, the deformation amount in each pass is controlled to not exceed 15% during the drawing process; The drawing process is protected by inert gas.

8. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, In the raw material smelting step, the multiple smelting also includes a vacuum electroslag remelting.

9. The method for preparing a nickel-based alloy spring according to claim 1 or 8, characterized in that, In the raw material smelting step, the vacuum level is controlled to be less than or equal to 1×10⁻⁶. -3 Pa.

10. The method for preparing a nickel-based alloy spring according to claim 1, characterized in that, It also includes the following steps: Quality inspection, which includes at least -20℃ low temperature impact test, seawater corrosion resistance test and H2S corrosion resistance test. The -20℃ low temperature impact test is performed by taking a forged square sample from the forged billet. The forged square sample is subjected to the -20℃ low temperature impact test after solution treatment and aging treatment. Seawater corrosion resistance test and H2S corrosion resistance test were conducted on the springs after secondary heat treatment.

11. A nickel-based alloy spring, characterized in that, It is prepared using the method for preparing nickel-based alloy springs as described in any one of claims 1-10.

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