A method for manufacturing a large-diameter seamless thin-walled tubular member

Abstract

The present application relates to a kind of preparation methods of large-diameter seamless thin-walled tubular parts, comprising the following steps: (1) raw material preparation;(2) vacuum melting;(3) pouring;(4) homogenization heat treatment;(5) hot forging;(6) compound strengthening forming;(7) fine grinding polishing.The present application successfully prepares high strength and toughness large-diameter seamless thin-walled hastelloy tubular parts by optimizing tooling equipment, chemical composition and heat treatment process.The preparation method of the present application not only can prepare excellent performance hastelloy thin-walled tubular parts, but also has the industrialization advantages such as simple preparation process flow, high production efficiency, controllable cost, etc., which can fully meet the large-scale application demand of high-performance hastelloy thin-walled tubular parts in engineering field.

Description

Technical Field

[0001] This invention relates to the field of Hastelloy technology, specifically to a method for preparing a large-diameter seamless thin-walled tubular component. Background Technology

[0002] Hastelloy alloys are a class of nickel-based superalloys developed by Hastelloy International Inc. in the United States, renowned for their excellent corrosion resistance, high-temperature strength, and oxidation resistance. These alloys are primarily enhanced in extreme environments by adding elements such as molybdenum, chromium, cobalt, and tungsten, and are widely used in chemical, aerospace, energy, and marine engineering fields.

[0003] Currently, the domestic technology system for manufacturing large-diameter seamless Hastelloy tubular parts using "hot forging + spinning" and "centrifugal casting + spinning" processes is relatively mature. However, it still faces two key technical bottlenecks in actual production: Insufficient control over the uniformity of wall thickness in finished tubular parts leads to a low material yield, which directly affects production cost-effectiveness. Hastelloy tubular components prepared by traditional processes have limitations in terms of mechanical properties. Their strength and plasticity are difficult to improve in a coordinated manner, and they cannot fully meet the stringent requirements for material performance under extreme working conditions such as deep-sea equipment and nuclear power systems. Summary of the Invention

[0004] This invention addresses the existing technical problems by providing a method for preparing large-diameter seamless thin-walled tubular components.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a large-diameter seamless thin-walled tubular component, comprising the following steps: (1) Raw material preparation: Prepare the raw materials; (2) Vacuum melting: The raw materials are placed in a vacuum induction furnace to melt and form an alloy liquid; (3) Casting: The alloy liquid is cast into an ingot at a casting temperature of 1300℃-1400℃; (4) Homogenization heat treatment: The ingot in step (3) is subjected to homogenization heat treatment to form Hastelloy alloy ingot; (5) Hot forging: The Hastelloy ingot is forged into a Hastelloy tube blank; (6) Composite strengthening forming: The Hastelloy tube blank is subjected to multiple composite strengthening treatments: spinning-heat treatment-deep cryogenic treatment to obtain seamless thin-walled Hastelloy tube parts.

[0006] Based on the above technical solution, the present invention can be further improved as follows: Further, in step (1), the raw materials are prepared according to the following weight percentages of elements: Ni 52.0wt%-54.0wt%, Fe 2.0wt%-4.0wt%, W 2.0wt%-4.0wt%, Cr 22.0wt%-25.0wt%, Mo 12.0wt%-14.0wt%, Co 2.0wt%-3.0wt%, N 0.5wt%-1.0wt%.

[0007] Furthermore, in step (2), the CrN substrate is first placed at the bottom of the furnace chamber of the vacuum induction furnace, and then the metal compound and metal elemental raw materials are placed into the vacuum induction furnace for melting, wherein the melting temperature is 1500℃-1600℃.

[0008] Furthermore, in step (4), the temperature of the homogenization heat treatment is 1100℃-1200℃, and the time of the homogenization heat treatment is 8h-12h.

[0009] Furthermore, in step (5), the hot forging temperature is 950℃-1050℃, the final forging temperature is ≥900℃, and the holding time is 1h-3h. The total deformation of the Hastelloy tube blank after hot forging is 75%-85%. The large deformation combined with the high temperature diffusion effect helps to homogenize the distribution of alloy elements, reduce the degree of segregation, and thus improve the consistency and stability of the overall performance of the material.

[0010] Furthermore, step (6) includes step (61): the Hastelloy tube blank undergoes a first: spinning-heat treatment-deep cryogenic composite strengthening treatment; (611) Spinning: The Hastelloy tube blank obtained after hot forging is spun in three passes. The deformation of the Hastelloy tube blank in a single spin is 18%-23%, which is an optimized scheme that takes into account the forming quality, material properties and production efficiency, avoids material cracking and ensures forming stability. Compared with a single large deformation, three spins can reduce the accumulation of residual stress, avoid excessive distortion of local structure, and help to obtain a more uniform microstructure and dimensional accuracy. The total deformation is 45%-54%. Through three cumulative deformations, the work hardening effect of the material can be fully stimulated, significantly improving the strength, hardness and wear resistance of the final product, and meeting the needs of high-performance applications. (612) Heat treatment: The Hastelloy tube blank obtained after spinning in step (6) is subjected to heat treatment at a temperature of 700-760℃ for 2-4 hours. (613) Deep cryogenic treatment: The Hastelloy tube blank obtained in step (612) is subjected to deep cryogenic treatment through liquid nitrogen medium.

[0011] Furthermore, step (6) also includes step (62): subjecting the Hastelloy tube blank to a second spinning-heat treatment-cryogenic composite strengthening treatment. (621) Spinning: The Hastelloy tube blank obtained after deep cooling in step (61) is spun in three passes. The deformation of the Hastelloy tube blank in a single spin is 18%-23%, which is an optimized scheme that takes into account the forming quality, material properties and production efficiency, avoids material cracking and ensures forming stability. Compared with a single large deformation, three spins can reduce the accumulation of residual stress, avoid excessive distortion of local structure, and help to obtain a more uniform microstructure and dimensional accuracy. The total deformation is 45%-54%. Through three cumulative deformations, the work hardening effect of the material can be fully stimulated, significantly improving the strength, hardness and wear resistance of the final product, and meeting the needs of high-performance applications. (622) Heat treatment: The Hastelloy tube blank obtained after spinning in step (621) is subjected to heat treatment at a temperature of 700℃-760℃ for 2h-4h. (623) Deep cryogenic treatment: The Hastelloy tube blank obtained in step (622) is subjected to deep cryogenic treatment through liquid nitrogen medium.

[0012] Furthermore, the cryogenic temperature in steps (613) and (623) is -120°C to -76°C.

[0013] Furthermore, in steps (611) and (621), a spinning equipment is used to spin the Hastelloy tube blank. The spinning equipment includes a tail top, a tail die, and a core die. One end of the tail top is connected to a transmission device through an adapter plate, and the other end of the tail top is connected to the positioning groove of the tail die through a positioning boss. The angle A between the tail top and the tail die is 10°-20°.

[0014] Furthermore, after step (6), step (7) fine grinding and polishing is also included: grinding the seamless thin-walled Hastelloy tubular parts.

[0015] The beneficial effects of this invention are: (1) In the Hastelloy system, doping with interstitial atoms (N atoms) can not only regulate the phase structure composition, but also change its deformation mechanism to achieve high strength and toughness of the material. Tubes doped with N have higher HDI stress (heterogeneous deformation induced stress). High HDI stress can simultaneously improve the strength and ductility of the alloy and delay plastic instability.

[0016] (2) The addition of CrN to introduce N element has the advantages of simpler process and lower cost compared with traditional high temperature and high pressure process.

[0017] (3) Cryogenic treatment has a significant impact on the microstructure and properties of Hastelloy. During cryogenic treatment, the austenite microstructure in the alloy undergoes a partial martensitic transformation, leading to lattice distortion and an increase in dislocation density, thereby improving the strength and hardness of the material. At the same time, cryogenic treatment can promote the release of residual stress, reduce microscopic defects, and refine grains, thereby improving the dimensional stability and fatigue resistance of the alloy.

[0018] (4) By optimizing the design of the tail top and tail mold guiding mechanism, the present invention effectively solves the problem of uneven wall thickness of Hastelloy tubes caused by core mold eccentricity or bending during the processing.

[0019] (5) Hastelloy can be prepared by using a multi-pass cyclic process of "spinning-annealing-spinning-annealing", which can effectively refine the grain size and optimize the microstructure. The intermediate annealing treatment introduced in the spinning deformation process not only eliminates the residual stress generated by cold deformation, but also promotes the formation of fine grains through recrystallization. This alternating processing method avoids the work hardening defects caused by single cold deformation, and enables the material to obtain a uniform and fine grain structure while maintaining good plasticity, thereby significantly improving the comprehensive mechanical properties of Hastelloy. By adopting the above technical solution, uniform grain size in all directions of Hastelloy was achieved, with tensile strength ≥1000MPa, yield strength ≥700MPa, and elongation ≥35%. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the spinning equipment used in this invention; Figure 2 This is a perspective view of the spinning equipment used in this invention; Figure 3 This is a cross-sectional view of the tail section used in this invention; Figure 4 This is a three-dimensional schematic diagram of the tail section used in this invention. Figure 1 ; Figure 5 This is a three-dimensional schematic diagram of the tail section used in this invention. Figure 2 ; Figure 6 This is a cross-sectional view of the tail mold of the present invention; Figure 7 This is a three-dimensional schematic diagram of the tail mold of the present invention; Figure 8 The results of the LUR (load-unload-reload tensile) test for Example 1 and Comparative Example 1 are shown. Figure 9 The HDI stress calculated from the LUR curve for Example 1 and Comparative Example 1; Figure 10 This is a microstructure diagram of Hastelloy from Example 1 of the present invention; Figure 11 This is a microstructure of Hastelloy alloy from Comparative Example 1 of the present invention; Figure 12 This is a microstructure diagram of Hastelloy alloy from Comparative Example 2 of the present invention; Figure 13 This is a microstructure diagram of Hastelloy alloy from Comparative Example 3 of the present invention.

[0021] Reference numerals: 1. Tail top; 2. Tail mold; 3. Core mold; 4. Hastelloy tube blank; 5. Adapter plate; 6. Transmission device. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. The terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention.

[0024] Example 1 like Figures 1 to 13 As shown, this invention discloses a method for preparing a large-diameter seamless thin-walled tubular component, comprising the following steps: (1) Raw material preparation: Prepare the raw materials; Specifically, the raw materials are formulated according to the following weight percentages of elements: Ni 52.0wt%-54.0wt%, Fe 2.0wt%-4.0wt%, W 2.0wt%-4.0wt%, Cr 22.0wt%-25.0wt%, Mo 12.0wt%-14.0wt%, Co 2.0wt%-3.0wt%, and N 0.5wt%-1.0wt%.

[0025] (2) Vacuum melting: The raw materials are placed in a vacuum induction furnace to melt and form an alloy liquid. Specifically, the CrN substrate is first placed at the bottom of the furnace chamber of the vacuum induction furnace, and then the metal compound and metal element are placed in the vacuum furnace. The raw materials are melted in the vacuum induction furnace with a vacuum degree of -0.1MPa and a melting temperature of 1500℃. The mixture is stirred and melted by electromagnetic stirring. After slag removal, the liquid alloy is introduced into the intermediate ladle in the vacuum casting chamber. Charcoal is placed at the bottom of the intermediate ladle. The burning of charcoal can consume the oxygen in the alloy liquid, reduce the porosity defects in the subsequent castings, improve the internal structure of the castings, and improve the quality of the castings.

[0026] (3) Casting: The liquid alloy obtained by vacuum melting in step (2) is cast into an ingot, wherein the casting temperature is 1400℃.

[0027] (4) Homogenization heat treatment: The ingot in step (3) is subjected to homogenization heat treatment to form Hastelloy alloy ingot; the temperature of homogenization heat treatment is 1200℃ and the time of homogenization heat treatment is 12h.

[0028] (5) Hot forging: The Hastelloy ingot obtained in step (4) is subjected to upsetting, hole expansion and drawing forging. The hot forging temperature is 1050℃, the final forging temperature is ≥900℃, and the holding time is 3h. The forging is formed into Hastelloy tube blank 4, wherein the total deformation of the hot-forged Hastelloy tube blank 4 is 80%.

[0029] (6) Composite strengthening forming: The Hastelloy tube blank 4 is subjected to multiple composite strengthening treatments: spinning-heat treatment-deep cryogenic treatment to obtain seamless thin-walled Hastelloy tube parts.

[0030] Including step (61): the Hastelloy tube blank 4 undergoes a first: spinning-heat treatment-deep cryogenic composite strengthening treatment; (611) Spinning: The Hastelloy tube blank 4 obtained after hot forging in step (5) is spun three times, and the deformation of the Hastelloy tube blank 4 in each spinning is 20%.

[0031] The entire spinning process employs, for example Figure 1The spinning equipment shown includes a tail top 1, a tail die 2, and a core die 3. One end of the tail top 1 is connected to a transmission device 6 via an adapter plate 5 (the transmission device 6 uses existing technology and will not be described in detail). It presses against one end of the Hastelloy tube blank 4 to achieve axial positioning of the Hastelloy tube blank 4 and prevent the Hastelloy tube blank 4 from moving back and forth during high-speed rotation. The core die 3 forms a complete inner contour mold and contacts the inner wall of the Hastelloy tube blank 4, determining the final forming size and shape accuracy of the Hastelloy tube blank 4. The positioning boss of the tail top 1 is installed in the positioning groove of the tail die 2. The angle A between the tail top 1 and the tail die 2 is 10°-20°, that is, the angle between the positioning boss and the positioning groove is 10°-20°. The positioning boss extending from this angle plays a guiding role, which can effectively prevent the core die 3 from bending and eccentricity, and ensure that the wall thickness of the finished tube part is uniform. The tail mold 2 and the tail top 1 are in contact at both ends to ensure that the positioning boss of the tail top 1 is not subjected to excessive load during spinning, thus avoiding damage. The distance L1 between the positioning boss of the tail top 1 and the tail mold 2 is 15mm-25mm, which reduces the wear of the tail top 1 on the core mold 3. At the same time, the depth L2 of the positioning groove of the tail top 1 is 3mm-5mm, which reduces the wear of the bearing in the adapter plate 5 through the axial positioning function, thereby ensuring the stability and reliability of the overall structure.

[0032] In this embodiment, the angle A between the tail top 1 and the tail mold 2 is 10°, the distance L1 between the tail top 1 and the tail mold 2 is 20mm, and the depth L2 of the positioning groove of the tail top 1 is 3mm. (612) Heat treatment: The Hastelloy tube blank 4 obtained after spinning in step (611) is subjected to heat treatment at a temperature of 720°C for 3 hours. (613) Deep cryogenic treatment: The Hastelloy tube blank 4 obtained in step (612) is subjected to deep cryogenic treatment through liquid nitrogen medium at a temperature of -100℃.

[0033] It also includes step (62): subjecting the Hastelloy tube blank 4 to a second spinning-heat treatment-cryogenic composite strengthening treatment. (621) Spinning: The Hastelloy tube blank 4 obtained after deep cooling in step (61) is spun in three passes, and the deformation of the Hastelloy tube blank 4 in each pass is 20%. The angle A between the tail top 1 and the tail die 2 is 10°, the distance L1 between the tail top 1 and the tail die 2 is 20mm, and the depth L2 of the positioning groove of the tail top 1 is 3mm. (622) Heat treatment: The Hastelloy tube blank 4 obtained after spinning in step (621) is subjected to heat treatment at a temperature of 720°C for 3 hours. (623) Deep cryogenic treatment: The Hastelloy tube blank 4 obtained in step (622) is subjected to deep cryogenic treatment through liquid nitrogen medium at a temperature of -100℃ to obtain a seamless thin-walled Hastelloy tube.

[0034] (7) Fine grinding and polishing: Use a polishing machine to grind the seamless thin-walled Hastelloy tubular parts to improve the surface quality of the tubular parts. The seamless thin-walled Hastelloy tubular parts are large-diameter seamless thin-walled Hastelloy tubular parts with a wall thickness of 3mm-4mm and a maximum diameter of φ2200mm.

[0035] Comparative Example 1 Unlike Example 1, the raw materials in this comparative example do not contain nitrogen, but the other steps are the same as in Example 1.

[0036] The seamless thin-walled Hastelloy tubular parts obtained by the processing method in this comparative example have low tensile strength and yield strength, which cannot meet the stringent requirements for material performance under extreme working conditions such as deep-sea equipment and nuclear power systems.

[0037] Comparative Example 2 Unlike Example 1, the N content in the raw materials in this comparative example is 2wt%-3wt%, while the other steps are the same as in Example 1.

[0038] The seamless thin-walled Hastelloy tubular parts obtained by the processing method in this comparative example have low elongation, resulting in poor plasticity, high brittleness, and cracking defects.

[0039] Comparative Example 3 Unlike Example 1, in this comparative example, the Hastelloy tubular parts obtained by heat treatment in steps (612) and (622) are cooled by room temperature liquid water at a temperature of 20°C-25°C. The other steps are the same as in Example 1.

[0040] The seamless thin-walled Hastelloy tubular parts obtained by the processing method in this comparative example have low tensile strength and yield strength, which cannot meet the stringent requirements for material performance under extreme working conditions such as deep-sea equipment and nuclear power systems.

[0041] The performance comparison of the seamless thin-walled Hastelloy tubular parts obtained in the examples and comparative examples is shown in Table 1 below: Table 1 Performance data for examples and comparative examples

[0042] In Comparative Example 1, no nitrogen (N) was added to the raw materials. The Hastelloy tubular parts obtained in this comparative example had lower tensile strength, yield strength, and hardness. This indicates that adding N to the raw materials can not only control the phase structure composition but also change its deformation mechanism (TWIP effect, TRIP effect) to achieve high strength and toughness in the material. Compared to Comparative Example 1 without N doping, Example 1 with N doping exhibited higher HDI stress (heterogeneous deformation induced stress). High HDI stress strengthening can simultaneously improve the strength and ductility of the alloy and delay plastic instability.

[0043] The TWIP effect refers to the phenomenon where, during plastic deformation, mechanical twins are formed within a metal to coordinate deformation and significantly improve work hardening rate and ductility. The TRIP effect refers to the phenomenon where, during plastic deformation, metastable austenite transforms into martensite under stress or strain, thereby increasing the material's strength and ductility.

[0044] The nitrogen content in Comparative Example 2 was greater than that in Example 1, resulting in a lower elongation of the prepared seamless thin-walled Hastelloy tubular parts. This led to poor plasticity, high brittleness, and cracking defects in the seamless thin-walled Hastelloy tubular parts.

[0045] In Comparative Example 3, the seamless thin-walled Hastelloy tubular parts were not subjected to cryogenic treatment, resulting in poor tensile strength and yield strength, which in turn affected the fatigue resistance of the Hastelloy tubular parts.

[0046] This invention successfully fabricates high-strength, large-diameter seamless thin-walled Hastelloy tubular components by optimizing tooling, chemical composition, and heat treatment processes. The fabrication method of this invention not only produces high-performance seamless thin-walled Hastelloy tubular components but also boasts advantages such as a simple process flow, high production efficiency, and controllable costs, making it suitable for large-scale applications in engineering fields.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a large-diameter seamless thin-walled tubular component, characterized in that, Includes the following steps: (1) Raw material preparation: The raw materials are prepared according to the following weight percentages of elements: Ni 52.0wt%-54.0wt%, Fe 2.0wt%-4.0wt%, W 2.0wt%-4.0wt%, Cr 22.0wt%-25.0wt%, Mo 12.0wt%-14.0wt%, Co 2.0wt%-3.0wt%, N 0.5wt%-1.0wt%; (2) Vacuum melting: The raw materials are placed in a vacuum induction furnace to melt and form an alloy liquid; (3) Casting: The alloy liquid is cast into an ingot at a casting temperature of 1300℃-1400℃; (4) Homogenization heat treatment: The ingot in step (3) is subjected to homogenization heat treatment to form Hastelloy alloy ingot; (5) Hot forging: The Hastelloy ingot is forged into a Hastelloy tube blank. The hot forging temperature is 950℃-1050℃, the final forging temperature is ≥900℃, and the holding time is 1h-3h. The total deformation of the Hastelloy tube blank after hot forging is 75%-85%. (6) Composite strengthening forming: The Hastelloy tube blank is subjected to multiple composite strengthening treatments: spinning-heat treatment-deep cryogenic treatment to obtain seamless thin-walled Hastelloy tube parts; Specifically, the steps include (61): the Hastelloy tube blank undergoes a first: spinning-heat treatment-deep cryogenic composite strengthening treatment; (611) Spinning: The Hastelloy tube blank obtained after hot forging is spun in three passes. The deformation of the Hastelloy tube blank in a single pass is 18%-23%, and the total deformation is 45%-54%. The Hastelloy tube blank (4) is spun using a spinning equipment. The spinning equipment includes a tail top (1), a tail die (2), and a core die (3). One end of the tail top (1) is connected to the transmission device (6) through a transition plate (5), and the other end of the tail top (1) is connected to the positioning groove of the tail die (2) through a positioning boss. The angle A between the positioning boss of the tail top (1) and the positioning groove of the tail die (2) is 10°-20°. (612) Heat treatment: The Hastelloy tube blank obtained after spinning in step (611) is subjected to heat treatment at a temperature of 700℃-760℃ for 2-4 hours. (613) Deep cryogenic treatment: The Hastelloy tube blank obtained in step (612) is subjected to deep cryogenic treatment through liquid nitrogen medium.

2. The method for preparing a large-diameter seamless thin-walled tubular component according to claim 1, characterized in that, In step (2), the CrN substrate is first placed at the bottom of the furnace chamber of the vacuum induction furnace, and then the metal compound and metal element raw materials are placed in the vacuum induction furnace for melting. The melting temperature is 1500℃-1600℃.

3. The method for preparing a large-diameter seamless thin-walled tubular component according to claim 1, characterized in that, In step (4), the temperature of the homogenization heat treatment is 1100℃-1200℃, and the time of the homogenization heat treatment is 8h-12h.

4. The method for preparing a large-diameter seamless thin-walled tubular component according to claim 1, characterized in that, Step (6) also includes step (62): subjecting the Hastelloy tube blank to a second spinning-heat treatment-cryogenic composite strengthening treatment. (621) Spinning: The Hastelloy tube blank obtained after deep cooling in step (61) is spun in three passes. The deformation of the Hastelloy tube blank in a single pass is 18%-23%, and the total deformation is 45%-54%. (622) Heat treatment: The Hastelloy tube blank obtained after spinning in step (621) is subjected to heat treatment at a temperature of 700℃-760℃ for 2h-4h. (623) Deep cryogenic treatment: The Hastelloy tube blank obtained in step (622) is subjected to deep cryogenic treatment through liquid nitrogen medium.

5. The method for preparing a large-diameter seamless thin-walled tubular component according to claim 4, characterized in that, The cryogenic temperature in steps (613) and (623) is -120°C to -76°C.

6. The method for preparing a large-diameter seamless thin-walled tubular component according to claim 1, characterized in that, Step (6) is followed by step (7) fine grinding and polishing: the seamless thin-walled Hastelloy tubular parts are ground.

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