A method for producing small-size nickel-chromium-based precipitation hardening wrought high-temperature alloy rods

Abstract

This invention relates to the field of high-temperature alloy bar technology, specifically disclosing a method for preparing small-diameter nickel-chromium-based precipitation-hardening deformable high-temperature alloy bars. The method sequentially includes steps such as vacuum induction melting, directional solidification electroslag remelting, multi-pass forging, rough rolling and finish rolling, alternating multi-pass cold drawing and intermediate annealing, centerless grinding, and direct aging treatment. This method improves the uniformity of ingot composition from the source through directional solidification control, eliminating the need for the high-temperature diffusion annealing process in traditional processes. It utilizes a hot-rolling-cold-drawing combined forming route to break through the lower size limit of conventional hot rolling, replacing turning and peeling to reduce metal loss and improve overall yield. Simultaneously, it ensures that the finished product has excellent microstructure uniformity, dimensional accuracy, and stable high-temperature mechanical properties. The produced bars can be widely used in the manufacture of small high-temperature core components in aerospace, precision energy equipment, and other fields, possessing good engineering application value and market prospects.

Description

Technical Field

[0001] This invention relates to the field of high-temperature alloy bar technology, and in particular to a method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed high-temperature alloy bars. Background Technology

[0002] GH4033 (also known as GH33) is a nickel-chromium-based precipitation-hardening wrought superalloy independently developed in my country. It uses nickel as the matrix, with 20%–22% chromium added to ensure excellent oxidation and corrosion resistance. It also contains 0.7%–1.0% aluminum and 2.5%–2.8% titanium, achieving dispersion strengthening through the precipitation of the γ' phase (Ni3(Al,Ti)). Small amounts of niobium, boron, and cerium are added to refine the grain and improve machinability. This alloy exhibits excellent comprehensive mechanical properties in the 700–750℃ range, and good oxidation, creep, and fatigue resistance below 900℃. It is a key material for core components such as turbine disks, blades, combustion chamber parts of aero-engines, hot-end structural parts of gas turbines, as well as high-temperature fasteners and heat exchange components.

[0003] In recent years, as aerospace equipment has developed towards lightweight, miniaturized, and highly reliable directions, the demand for miniaturized high-temperature components in the fields of energy and power and precision manufacturing has been increasing. GH4033 small round rolled materials with a diameter of 4~8mm have become increasingly widely used in various scenarios, such as micro turbine blades, small high-temperature fasteners, high-temperature structural parts for precision instruments, and micro sensor elements. The requirements for the dimensional accuracy, surface quality, and mechanical property stability of these components are much higher than those for traditional large-size rolled materials.

[0004] Currently, the industrial production of GH4033 high-temperature alloy rolled products in China is mostly concentrated on specifications with diameters of 8mm and above. Among them, the mainstream specifications for hot-rolled bars are φ20~55mm, and the mainstream specifications for cold-drawn bars are φ8~45mm. For small round bars with diameters less than 8mm, existing manufacturing processes mostly simply scale down the hot rolling or cold drawing processes used for larger specifications, without fully considering the dimensional characteristics of small round bars, such as large specific surface area, fast heat conduction rate, and significant stress concentration effect. This results in several technical limitations in actual production.

[0005] 1. High difficulty in hot working and insufficient precision in temperature and deformation control: During the processing of small round bars, heat dissipates rapidly and unevenly, resulting in poor temperature field stability and a tendency for localized overheating or undercooling. Localized overheating can cause abnormal grain growth in the alloy, weakening the dispersion strengthening effect of the γ' phase and leading to a significant decrease in high-temperature mechanical properties. Localized undercooling reduces the metal's plasticity, induces processing cracks, and causes problems such as decreased internal microstructure uniformity, excessive grain size differences, and compositional segregation, resulting in insufficient consistency in the material's mechanical properties. In addition, the precision of deformation control per pass during the rolling process of small round bars is limited, easily causing fluctuations in the rolled material's dimensions and a low yield rate of hot-processed finished products.

[0006] 2. Poor surface quality and low yield: Due to the small size of small-diameter bars, the contact area between the rolled material and the rolls is extremely small during rolling. Stress at the contact points is highly concentrated and far exceeds the material's yield strength, easily inducing defects such as surface cracks, folds, scratches, and oxide scale adhesion. Fine longitudinal cracks are difficult to completely remove through subsequent processing, severely affecting the fatigue resistance and service life of components. Surface folds easily form internal stress concentration points, increasing the risk of fracture during high-temperature service. To eliminate these surface defects, extensive grinding is required, increasing production steps and manufacturing costs. Excessive grinding can also lead to product scrapping; under traditional processes, the overall yield of small round bars is generally below 70%.

[0007] 3. Unstable Performance: Existing heat treatment processes are mostly designed for large-diameter forged and rolled materials, neglecting the processing characteristics of small-diameter materials. This results in insufficient uniformity of γ' phase precipitation and large fluctuations in precipitation amount, leading to significant differences in strength and hardness in different parts of the rolled material. High-temperature creep and calorific value also fluctuate considerably, making it difficult to meet the service stability requirements of high-end applications. Furthermore, existing processes lack sufficient control over raw material impurities and grain refinement measures, with some products having grain sizes lower than ASTM Level 5, further exacerbating performance instability and restricting the application of small round materials in core components of high-end equipment.

[0008] 4. In terms of dimensional accuracy control, small round bars with a diameter of φ4~8mm are usually required to have a diameter deviation of ≤±0.03mm. However, the traditional rolling process follows the production method of large-size rolled materials, and the finished products are prone to problems such as excessive ovality, excessive diameter fluctuation and straightness deviation. An additional straightening process is required to correct these issues, which not only prolongs the production cycle, but the stress introduced during the straightening process may also have an adverse effect on the material properties, making it difficult to directly adapt to the precision assembly requirements of small parts.

[0009] Therefore, the existing GH4033 high-temperature alloy small round material preparation process has problems such as high difficulty in heat treatment control, many surface defects, low yield, insufficient performance stability and poor dimensional accuracy. It is difficult to meet the application requirements of high-end equipment field for high-quality small-size high-temperature alloy materials. There is an urgent need to develop a targeted preparation process to solve the above technical problems. Summary of the Invention

[0010] To address the problems of difficult heat treatment control, numerous surface defects, low yield, insufficient performance stability, and poor dimensional accuracy in the existing GH4033 high-temperature alloy small round bar preparation process, this invention provides a method for preparing small-size nickel-chromium-based precipitation hardening deformed high-temperature alloy bars.

[0011] To solve the above-mentioned technical problems, the technical solution provided by the embodiments of the present invention is as follows: A method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars includes the following steps: S1, the raw materials are melted under vacuum and then cast to obtain an ingot; S2, using the ingot as a consumable electrode, and employing a CaF2-Al2O3-CaO-electrolytic MgO slag system, directional solidification electroslag remelting is carried out under an inert atmosphere, with the melting rate controlled at 1.5~3.0 kg / min, to obtain an electroslag ingot. S3, the electroslag ingot is heated and held at a certain temperature, and then subjected to multiple forging processes to obtain a round bar billet; S4, after heating and holding the round bar billet at a certain temperature, rough rolling and finish rolling are performed sequentially to obtain a hot-rolled bar billet; S5, the hot-rolled bar billet is processed into a small round billet of the target diameter by a multi-pass cold drawing process that alternates between intermediate annealing and cold drawing. S6, the small round billet is centerlessly ground, and then the ground billet is aged at 690~710℃ and air-cooled to obtain small-sized nickel-chromium-based precipitation hardening deformed high-temperature alloy bars.

[0012] Compared to existing technologies, the small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars provided by this invention combine vacuum induction melting with directional solidification electroslag remelting under a protective atmosphere in a specific slag system. By precisely controlling the melting rate, inclusions and gases in the alloy are thoroughly removed, while the orderly solidification of the ingot is achieved. This improves the uniformity of element distribution and refines the as-cast grains, effectively alleviating the problem of compositional segregation. Consequently, a homogeneous billet can be provided for subsequent plastic processing without the need for an additional high-temperature diffusion annealing process. Subsequent multi-stage forging and gradual plastic deformation through rough rolling and finish rolling can fully break down the coarse as-cast structure, control the grain morphology and distribution of the billet, and obtain a cold-drawn material with dimensions and microstructure suitable for the desired shape. The hot-rolled billets are processed using a multi-pass cold drawing process that alternates between intermediate annealing and cold drawing. This process can eliminate work hardening and control deformation stress in a timely manner during the diameter reduction process, breaking through the lower limit of the finished product size of the hot rolling process and stably producing small-diameter bars. Compared with the traditional turning and peeling processing method, this process can significantly reduce metal loss, improve the overall yield, and obtain higher dimensional accuracy and better surface forming quality. Finally, after centerless grinding and surface finishing, aging treatment is performed. This process can control the uniform dispersion precipitation of the γ' strengthening phase while ensuring that the surface roughness meets the requirements of precision machining. This gives the finished bars stable and excellent room temperature and high temperature mechanical properties, which can meet the service requirements of small high-temperature components in the field of high-end equipment.

[0013] In some specific embodiments of the present invention, the nickel-chromium based precipitation hardening deformation superalloy is GH4033.

[0014] In some specific embodiments of the present invention, step S1 is as follows: high-purity nickel plate, electrolytic chromium sheet, metallic titanium block, aluminum granules, ferroboron, metallic cerium, nickel-magnesium alloy, graphite carburizing agent and recycled material are added to a vacuum induction furnace for smelting. The smelting temperature is 1450~1500℃, and electromagnetic stirring is carried out for 15~20 minutes to control the impurity elements in the molten steel to S≤0.003%, P≤0.015%, and O≤0.0015%.

[0015] Furthermore, the pressure of the vacuum induction furnace is ≤5Pa.

[0016] In some specific embodiments of the present invention, in S2, the mass ratio of CaF2, Al2O3, CaO, and electrolytic MgO in the slag system is 65:20:10:5.

[0017] In some specific embodiments of the present invention, S2 includes an arc-initiation and slag-forming stage, a steady-state smelting stage, and a feeding stage: During the arc initiation and slag formation stage, the current is controlled at 1000~3000A and the voltage at 50~63V after energization; slag is added in 2~3 batches, and the current is increased to 5400A~5600A during the slag addition process. The steady-state melting current is 6500~9500A and the voltage is 60~90V. An axial temperature gradient is formed in the crystallizer through the bottom of the water-cooled crystallizer, so that the molten metal solidifies layer by layer from bottom to top along the axial direction. The feeding stage includes: when the remaining mass of the electrode is 6% to 9%, the current is reduced to 3000 to 4500A and the voltage is reduced to 30 to 50V, and feeding is carried out for 30 to 50 minutes; after power is cut off, the furnace is cooled for 30 to 60 minutes, and the ingot temperature is reduced to below 600℃ for demolding and air cooling.

[0018] Specifically, before arc initiation and slag formation, the process includes: welding and fixing the crystallizer to a steel base; then vertically inserting the consumable electrode into the center of the crystallizer; sealing the circumferential seam between the electrode and the crystallizer with ceramic fiber material to prevent the protective atmosphere from escaping during smelting. After sealing, gas replacement is initiated before power supply, by introducing high-purity argon gas into the crystallizer at a flow rate controlled at 1.0~2.0 m³ / s. 3 The argon gas flow rate is maintained at a constant rate of 1 h for at least 10 minutes to ensure that the air inside the crystallizer is fully expelled, creating an inert protective atmosphere. After the arc is ignited by power, the same flow rate of argon gas is continuously introduced to ensure that the entire melting process is under argon protection, preventing oxidation of the molten steel and loss of alloying elements.

[0019] Furthermore, during the arc initiation and slag formation stage, slag is added in two batches. First, 2 / 3 of the total slag is added. After the slag temperature stabilizes at 1650~1750℃, the remaining slag is added. The slag addition time is controlled at 2~15 minutes, and the slag formation time is controlled at 30~35 minutes.

[0020] The above-mentioned feeding method allows the slag to fully complete the melting, mixing and deoxidation and desulfurization reactions, forming a liquid slag pool with uniform composition and stable metallurgical properties, which provides a reliable guarantee for the refining effect and ingot surface quality in the subsequent normal smelting stage.

[0021] Furthermore, the steady-state smelting process employs current-voltage closed-loop control to ensure that the melting rate fluctuation is ≤±5%.

[0022] Furthermore, the axial temperature gradient is 100~500℃ / cm.

[0023] The specific control methods include: during the normal smelting stage, a current-voltage closed-loop control system stabilizes the current at 6500~9500A and the voltage at 60~70V to ensure the stability of the heat input to the molten pool; simultaneously, forced circulating cooling water is supplied to the bottom of the crystallizer, causing the molten steel at the bottom to be cooled and solidify rapidly first, while the molten metal in the upper area near the molten pool remains in a molten or near-molten state, thus creating a significant temperature difference along the axial direction of the crystallizer. This sequential solidification method, solidifying layer by layer from bottom to top, effectively suppresses macroscopic segregation and central porosity, promotes the axial directional growth of columnar crystals, and significantly improves the axial density and compositional uniformity of the electroslag ingot. The specific value of the temperature gradient can be synergistically controlled by adjusting the melting rate and cooling water flow rate. When the melting rate is low and the cooling water flow rate is high, the axial temperature gradient increases accordingly, and vice versa. Within this process window, the required temperature gradient value within the range of 100~500℃ / cm can be flexibly obtained.

[0024] In some specific embodiments of the present invention, in S3, the heating and heat preservation temperature is 1110~1180℃, and the heat preservation time is 1~3h.

[0025] In some specific embodiments of the present invention, in S3, the total deformation is controlled to be 60%~85%.

[0026] In some specific embodiments of the present invention, in S3, the final forging temperature is not lower than 920°C.

[0027] In some specific embodiments of the present invention, S3 specifically includes: The first heating is carried out at 1160~1180℃ and held for 1.5~2.5 hours, then forged into a square billet with a cross-sectional side length of 240~260mm; The second heating is carried out at 1140~1160℃ and held for 1.5~2 hours, forging into a square billet with a cross-sectional side length of 180~200mm; The third heating is carried out at 1120~1140℃ and held for 1~1.5 hours, forging into a round billet with a diameter of 140~170mm.

[0028] The above-mentioned three-stage forging process adopts a step-by-step reduction of heating temperature, combined with the corresponding deformation amount distribution for each stage. Under the premise of ensuring forging penetration and deformation uniformity, it can effectively control the final forging microstructure and avoid grain coarsening caused by excessively high final forging temperature, thereby obtaining a round bar billet with uniform microstructure and fine grains.

[0029] In some specific embodiments of the present invention, in S4, the heating and heat preservation temperature is 1100~1150℃, and the heat preservation time is 0.5~3h.

[0030] In some specific embodiments of the present invention, in S4, the hot-rolled bar billet is first roughed twice and then finished once to a diameter of 10-15mm; the total number of finishing rolling passes is 5-7, the total deformation of finishing rolling is 70%-97%, the deformation per pass is 15%-20%, and the rolling speed is 0.8-1.2m / s.

[0031] Under this finishing rolling process window, the deformation amount in each pass is relatively uniform, which is conducive to obtaining a consistent degree of deformation along the entire length and cross-section of the rolled piece, thereby further refining the grain structure of the hot-rolled billet. The high total deformation amount of finishing rolling ensures sufficient dynamic recrystallization driving force, while the moderate deformation amount per pass and rolling speed take into account both the surface quality and dimensional accuracy of the rolled piece, providing a hot-rolled billet with good surface condition and microstructure for the subsequent cold drawing process.

[0032] Specifically, the roughing process employs a reversible 450 mill to roll the billet into 48mm diameter sheets. 48mm square billet. The finishing rolling is carried out using a 320 rolling mill to roll the 48mm square billet. 48mm square billets are rolled into hot-rolled bar billets with a diameter of 10~15mm.

[0033] In some specific embodiments of the present invention, in S5, the total number of cold drawing passes is 4 to 8, the total cold drawing deformation is 70% to 90%, the cold drawing deformation per pass is 8% to 25%, and the cold drawing speed is 0.5 to 1.0 m / s; before each cold drawing pass, an intermediate annealing stress relief is performed, the intermediate annealing temperature is 980 to 1130°C, and after holding at the temperature for 1 to 1.5 hours, it is air-cooled.

[0034] This alternating cold drawing and annealing process design can promptly eliminate work hardening effects after each diameter reduction pass, allowing the material to recover to a softened state suitable for continued deformation before the next cold drawing pass. This effectively prevents billet cracking or surface damage caused by the continuous accumulation of deformation resistance. Simultaneously, each annealing process provides a diffusion window for the dissolution and redistribution of carbides and strengthening phases in the alloy, which is beneficial for the synergistic control of microstructure during multi-pass cold drawing.

[0035] By properly matching the above process parameters, the billet can be stably processed to the target diameter while ensuring forming quality, and a uniform cross-sectional size and microstructure can be obtained along the length direction, laying a good foundation for subsequent surface finishing and heat treatment.

[0036] In some specific embodiments of the present invention, in S5, the target diameter is 4~8mm.

[0037] In some specific embodiments of the present invention, in S6, the grinding amount of the centerless grinding is 0.05~0.1mm, and the surface roughness Ra after grinding is ≤1.6μm.

[0038] The centerless grinding process described in S6 is as follows: The small round billets obtained from S5 are fed into a centerless grinder for surface finishing. The grinding depth is controlled at 0.05~0.1mm. This process removes minor defects and oxide layers from the billet surface while ensuring that the bar achieves a uniform diameter and a smooth surface quality along its entire length. After grinding, the surface roughness Ra of the bar is ≤1.6μm, meeting the surface quality requirements for precision machining.

[0039] The centerless grinding process mentioned above is set before the S6 aging heat treatment. After the surface defect layer is removed by grinding, the bar can enter the aging treatment stage with a clean and smooth surface. This avoids the risk of stress concentration or oxidation expansion caused by surface defects during the heat treatment process, and helps to ensure the uniformity of mechanical properties and the stability of surface quality of the finished bar.

[0040] In some specific embodiments of the present invention, in S6, the aging process takes 15.5 to 16.5 hours.

[0041] It should be noted that in the preparation method provided by this invention, the S6 heat treatment step only includes aging treatment (holding at 690~710℃ for 15.5~16.5h followed by air cooling), without the traditional solution treatment. This invention directly ages the cold-drawn bar stock, preserving the fine-grained structure and work hardening effect formed during cold deformation, allowing the γ' strengthening phase to precipitate uniformly and diffusely on the fine-grained matrix, thereby obtaining superior room temperature and high temperature strength. Furthermore, from a process economy perspective, omitting the solution treatment can reduce energy consumption and manufacturing costs, reduce the risk of oxidation burn-off and surface quality deterioration caused by high-temperature heat treatment, and facilitate the high-efficiency, low-cost, and high-quality industrial production of small-diameter bars.

[0042] In summary, this invention discloses a method for preparing small-diameter nickel-chromium-based precipitation-hardening deformable superalloy bars. The method sequentially includes vacuum induction melting, directional solidification electroslag remelting, multi-pass forging, rough rolling and finish rolling, alternating multi-pass cold drawing and intermediate annealing, centerless grinding, and direct aging treatment. This method improves the uniformity of ingot composition from the source through directional solidification control, eliminating the need for the high-temperature diffusion annealing process in traditional processes. It utilizes a hot-rolling-cold-drawing combined forming route to overcome the lower size limit of conventional hot rolling, replacing turning and peeling to reduce metal loss and improve overall yield. Simultaneously, it ensures that the finished product has excellent microstructure uniformity, dimensional accuracy, and stable high-temperature mechanical properties. The manufactured bars can be widely used in the manufacture of small high-temperature core components in aerospace, precision energy equipment, and other fields, possessing good engineering application value and market prospects. Attached Figure Description

[0043] Figure 1 Metallographic image of a 4.02 mm diameter bar prepared in the cold-drawn state according to Example 1 of the present invention; Figure 2 The images show the metallographic structures of heat-treated bars with a diameter of 4.02 mm prepared in Example 1 and Comparative Example 1 of the present invention, where (a) Comparative Example 1, Specification 1, (b) Comparative Example 1, Specification 2, and (c) Example 1. Figure 3 Metallographic image of a 5.03 mm diameter bar prepared in the cold-drawn state according to Example 2 of the present invention; Figure 4 The images show the metallographic structures of heat-treated bars with a diameter of 5.03 mm prepared in Example 2 and Comparative Example 2 of the present invention, where (a) Comparative Example 2, Specification 1, (b) Comparative Example 2, Specification 2, and (c) Example 2. Figure 5 Metallographic image of a cold-drawn bar with a diameter of 8.03 mm prepared in Example 3 of this invention; Figure 6 The images show the metallographic structures of 8.03 mm diameter bars prepared in the heat-treated state in Example 3 and Comparative Example 3 of the present invention, where (a) Comparative Example 3, Specification 1, (b) Comparative Example 3, Specification 2, and (c) Example 3. Figure 7 The image shows the cold-drawn metallographic structure of the 8.09 mm diameter bar prepared in Comparative Example 4 of this invention. Figure 8 The images show the metallographic structures of 8.09 mm diameter bars prepared in the heat-treated state according to Comparative Examples 4 and 5 of the present invention, wherein (a) Comparative Example 5, Formulation 1, (b) Comparative Example 5, Formulation 2, and (c) Comparative Example 4. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] To better illustrate the present invention, further examples are provided below.

[0046] Example 1 This embodiment provides a method for preparing a small round GH4033 high-temperature alloy bar with a diameter of 4mm. The specific steps are as follows: Step 1: Vacuum Induction Melting The alloy was fed into a vacuum induction furnace according to the following composition: GH4033 alloy (Cr 20.5%, Al 0.8%, Ti 2.6%, Nb 1.1%, B 0.008%, Ce 0.01%, Ni balance). The mixture was heated to 10... -3 Under a vacuum of Pa, the mixture was smelted at 1480℃ with electromagnetic stirring for 18 minutes. The impurity elements were controlled to be S≤0.003%, P≤0.015%, and O≤0.0015%. The mixture was then cast to obtain an ingot.

[0047] Step 2: Directional solidification electroslag remelting Using the ingot obtained from vacuum induction melting as a consumable electrode, electroslag remelting was performed using a slag system of CaF2-Al2O3-CaO-electrolytic MgO (mass ratio 65%:20%:10%:5%). The specific process is as follows: The crystallizer was welded and fixed to the steel base, and the electrode was placed into the crystallizer and sealed with ceramic fiber. Argon gas was introduced for 15 minutes before power supply, and the argon gas flow rate was maintained at 1.5 m³ / s after power supply. 3 / h; After powering on, control the current at 2000A and the voltage at 55V to initiate arc slag formation. Add preheated slag in two batches, first adding 2 / 3 of the total slag. After the slag temperature stabilizes at 1700℃, add the remaining slag. During the slag addition process, increase the current to 5500A. Control the slag addition time to 5 minutes and the slag formation time to 32 minutes. Once a stable slag pool has formed, control the current at 9000A and the voltage at 65V, and control the melting rate at 3.0 kg / min. Use current-voltage closed-loop control. (Control melting rate fluctuation ≤ ±5%), and pass forced circulating cooling water through the bottom of the crystallizer to form an axial temperature gradient of about 300℃ / cm in the crystallizer, which promotes the molten metal to solidify layer by layer from bottom to top along the axial direction; when the electrode has 90kg left, it enters the hot sealing stage, and the current is reduced to 3800A and the voltage is reduced to 40V. The furnace is stopped after feeding for 40 minutes until the electrode has 15kg left; after the furnace is stopped, it is cooled in the furnace for 45 minutes. When the ingot temperature drops below 600℃, it is demolded and air-cooled to obtain an electroslag ingot.

[0048] Step 3: Forging and billet preparation After heating and holding the electroslag ingot at a certain temperature, a multi-directional forging process is used, with a final forging temperature of 980℃, and the ingot is formed through three forging cycles. First heat treatment: Heat to 1170℃ and hold for 2 hours, then forge into a 250mm×250mm square billet; Second heating: Heat to 1150℃ and hold for 1.5 hours, then forge into a 190mm×190mm square billet; Third heating: Heat to 1130℃ and hold for 1 hour to forge into a round bar billet with a diameter of 160mm.

[0049] Step 4: Hot rolling pretreatment A 160mm diameter round bar billet is heated to 1120℃ and held for 2 hours, then rough-rolled to a 98mm×98mm square billet using a 450mm reversible rolling mill. The 98mm×98mm square billet is then loaded into a furnace and heated further, held at 1120℃ for 40 minutes, and then rough-rolled to a 48mm×48mm square billet. After cooling to room temperature, it is cold-cut into sections. Subsequently, the 48mm×48mm square billet is heated to 1120℃ and held for 1 hour, then finished in one pass using a 320mm rolling mill, with the deformation per pass controlled at 15%~20% and the rolling speed at 1.0m / s, to a 10mm diameter hot-rolled bar billet.

[0050] Step 5: Cold drawing and forming The hot-rolled billet was annealed online (held at 1100℃ for 1 hour, then air-cooled), followed by 7 passes of annealing and cold drawing at a speed of 0.8 m / s. The specifications changed sequentially as follows: 10 mm → 9.3 mm → 8.2 mm → 7.2 mm → 6.3 mm → 5.5 mm → 4.8 mm → 4.2 mm. Before each pass of cold drawing, intermediate annealing was performed to relieve stress. The annealing regime was 1100℃ for 1 hour and then air-cooled. The diameter was reduced in each pass using a die with the corresponding hole diameter.

[0051] Step 6: Surface treatment and heat treatment After rough straightening of the 4.2mm diameter bar, it was ground using a centerless grinder with a grinding amount of 0.08mm to obtain a finished bar with a surface roughness Ra=1.2μm.

[0052] Step 7: Heat treatment: Hold at 700℃ for 16 hours, then air cool. The actual measured diameter of the finished product is 4.02mm. The yield rate is 67%.

[0053] Example 2 This embodiment provides a method for preparing a small round GH4033 high-temperature alloy bar with a diameter of 5mm. The specific steps are as follows: Step 1: Vacuum Induction Melting The alloy was fed into a vacuum induction furnace according to the following composition: GH4033 alloy (Cr 21%, Al 0.9%, Ti 2.7%, Nb 1.2%, B 0.009%, Ce 0.012%, Ni balance). The alloy was melted at 1450℃ under a vacuum of 8 Pa, with electromagnetic stirring for 20 min. The impurity elements were controlled to be S≤0.003%, P≤0.015%, and O≤0.0015%. The alloy was then cast to obtain an ingot.

[0054] Step 2: Directional solidification electroslag remelting Using the ingot obtained from vacuum induction melting as a consumable electrode, electroslag remelting was performed using a slag system of CaF2-Al2O3-CaO-electrolytic MgO (mass ratio 65%:20%:10%:5%). The specific process is as follows: The crystallizer was welded and fixed to the steel base, and the electrode was placed into the crystallizer and sealed with ceramic fiber. Argon gas was introduced for 12 minutes before power supply, and the argon gas flow rate was maintained at 2.0 m³ / s after power supply. 3 / h; After powering on, control the current at 1000A and the voltage at 50V to initiate arc slag formation. Add preheated slag in two batches, first adding 2 / 3 of the total slag. After the slag temperature stabilizes at 1650℃, add the remaining slag. During the slag addition process, increase the current to 5500A. Control the slag addition time to 15min and the slag formation time to 35min. Once a stable slag pool has formed, control the current at 9000A and the voltage at 60V, and control the melting rate at 2.5kg / min. Use current-voltage closed-loop control. (Control melting rate fluctuation ≤ ±5%), forced circulating cooling water is passed through the bottom of the crystallizer to form an axial temperature gradient of about 200℃ / cm in the crystallizer, which promotes the molten metal to solidify layer by layer from bottom to top along the axial direction; when the electrode has 60kg left, it enters the hot sealing stage, the current is reduced to 3000A and the voltage is reduced to 30V, and the furnace is stopped after 50min when the electrode has 10kg left; after the furnace is stopped, it is cooled in the furnace for 30min, and the ingot temperature is reduced to below 600℃ before demolding and air cooling to obtain the electroslag ingot.

[0055] Step 3: Forging and billet preparation After heating and holding the electroslag ingot at a certain temperature, a multi-directional forging process is used to form it at a final forging temperature of 990℃, through three forging cycles. First heat treatment: Heat to 1160℃ and hold for 2.5 hours, then forge into a 260mm×260mm square billet; Second heating: Heat to 1140℃ and hold for 2 hours, then forge into a 200mm×200mm square billet; Third heating: Heat to 1130℃ and hold for 1.5 hours, then forge into a round billet with a diameter of 170mm.

[0056] Step 4: Hot rolling pretreatment A 170mm diameter round bar billet is heated to 1100℃ and held for 3 hours, then rough-rolled to a 108mm×108mm square billet using a 450mm reversible rolling mill. The 108mm×108mm square billet is then loaded into a furnace and heated further, held at 1100℃ for 40 minutes, and then rough-rolled to a 58mm×58mm square billet. After cooling to room temperature, it is cold-cut into sections. Subsequently, the 58mm×58mm square billet is heated to 1100℃ and held for 1 hour, then finished rolled in one pass using a 320mm rolling mill, with the deformation controlled at 15%~20% per pass and the rolling speed at 0.5m / s, to a 10mm diameter hot-rolled bar billet.

[0057] Step 5: Cold drawing and forming The hot-rolled billet was annealed online (held at 980℃ for 1.5h, then air-cooled), followed by 5 passes of annealing and cold drawing at a speed of 0.8m / s. The diameter changes were as follows: 10mm → 8.9mm → 7.9mm → 6.9mm → 6.0mm → 5.2mm. Before each pass of cold drawing, an intermediate annealing was performed to relieve stress. The annealing regime was 980℃ for 1.5h and then air-cooled. The diameter was reduced in each pass using a die with the corresponding hole diameter.

[0058] Step 6: Surface Treatment After rough straightening of the 5.2mm diameter bar stock, it was ground using a centerless grinder with a grinding amount of 0.09mm to obtain a semi-finished bar stock with a surface roughness Ra=1.3μm.

[0059] Step 7: Heat Treatment The material was kept at 690℃ for 16 hours and then air-cooled. The actual measured diameter of the finished product was 5.03 mm. The yield rate was 70%.

[0060] Example 3 This embodiment provides a method for preparing a small round GH4033 high-temperature alloy bar with a diameter of 8mm. The specific steps are as follows: Step 1: Vacuum Induction Melting The alloy was fed into a vacuum induction furnace according to the following composition: GH4033 alloy (Cr 20%, Al 0.7%, Ti 2.5%, Nb 1.0%, B 0.007%, Ce 0.008%, Ni balance). The alloy was smelted at 1500℃ under a vacuum of 5Pa, with electromagnetic stirring for 15min. The impurity elements were controlled to be S≤0.003%, P≤0.015%, and O≤0.0015%. The alloy was then cast to obtain an ingot.

[0061] Step 2: Directional solidification electroslag remelting Using the ingot obtained from vacuum induction melting as a consumable electrode, electroslag remelting was performed using a slag system of CaF2-Al2O3-CaO-electrolytic MgO (mass ratio 65%:20%:10%:5%). The specific process is as follows: The crystallizer was welded and fixed to the steel base. The electrode was placed into the crystallizer and sealed with ceramic fiber. Argon gas was introduced for 10 minutes before power supply, and the argon gas flow rate was maintained at 1.0 m³ / min after power supply. 3 / h; After powering on, control the current at 3000A and the voltage at 63V to initiate arc slag formation. Add preheated slag in two batches, first adding 2 / 3 of the total slag. After the slag temperature stabilizes at 1650℃, add the remaining slag. During the slag addition process, increase the current to 5500A, control the slag addition time to 2min, and the slag formation time to 30min. Once a stable slag pool has formed, control the current at 8500A and the voltage at 70V, and control the melting rate at 2.0kg / min. Use current-voltage closed-loop control ( (Control melting rate fluctuation ≤ ±5%), and pass forced circulating cooling water through the bottom of the crystallizer to form an axial temperature gradient of about 100℃ / cm in the crystallizer, which promotes the molten metal to solidify layer by layer from bottom to top along the axial direction; when the electrode has 75kg left, it enters the hot sealing stage, and the current is reduced to 4000A and the voltage is reduced to 50V. The furnace is stopped after feeding for 30 minutes until the electrode has 20kg left; after the furnace is stopped, it is cooled in the furnace for 60 minutes. When the ingot temperature drops below 600℃, it is demolded and air-cooled to obtain an electroslag ingot.

[0062] Step 3: Forging and billet preparation After heating and holding the electroslag ingot at a certain temperature, a multi-directional forging process is used to form it at a forging temperature of 970℃, through three forging cycles. First heat treatment: Heat to 1180℃ and hold for 1.5 hours, then forge into a 240mm×240mm square billet; Second heating: Heat to 1160℃ and hold for 1.5 hours, then forge into a 180mm×180mm square billet; Third heating: Heat to 1140℃ and hold for 1.5 hours, then forge into a round billet with a diameter of 150mm.

[0063] Step 4: Hot rolling pretreatment A 150mm diameter round bar billet is heated to 1150℃ and held for 0.5 hours, then rough-rolled to a 108mm×108mm square billet using a 450mm reversible rolling mill. The 108mm×108mm square billet is then loaded into a furnace and heated further, held at 1150℃ for 40 minutes, and then rough-rolled to a 58mm×58mm square billet. After cooling to room temperature, it is cold-cut into sections. Subsequently, the 58mm×58mm square billet is heated to 1150℃ and held for 1 hour, then finished rolled in one pass using a 320mm rolling mill, with the deformation per pass controlled at 15%~20% and the rolling speed at 1.2m / s, to a hot-rolled bar billet with a diameter of 11mm.

[0064] Step 5: Cold drawing and forming The hot-rolled billet was annealed online (held at 1130℃ for 1 hour, then air-cooled), followed by three passes of annealing and cold drawing at a speed of 1.0 m / s. The diameter changes were as follows: 11 mm → 10.5 mm → 9.3 mm → 8.1 mm. Before each pass of cold drawing, intermediate annealing was performed to relieve stress. The annealing regime was 1130℃ for 1 hour and then air-cooled. The diameter was reduced in each pass using a die with the corresponding hole diameter.

[0065] Step 6: Surface Treatment After rough straightening of the 8.1 mm diameter bar, it was ground using a centerless grinder with a grinding amount of 0.07 mm to obtain a semi-finished bar with a surface roughness Ra=1.2 μm.

[0066] Step 7: Heat Treatment The material was kept at 710℃ for 16 hours and then air-cooled. The actual measured diameter of the finished product was 8.03 mm. The yield rate was 68%.

[0067] Comparative Example 1 This comparative example provides a method for preparing a GH4033 high-temperature alloy small round bar with a diameter of 4mm. The only difference from Example 1 is that the heat treatment in step 7 uses solution treatment followed by aging treatment. Steps 1 to 6 are exactly the same as in Example 1. Rule 1: Hold at 1080℃ for 8 hours, then air cool; hold at 700℃ for 16 hours, then air cool. System 2: Keep at 980℃ for 8 hours and then air cool; keep at 700℃ for 16 hours and then air cool.

[0068] Comparative Example 2 This comparative example provides a method for preparing a GH4033 high-temperature alloy small round bar with a diameter of 5mm. The only difference from Example 2 is that the heat treatment in step 7 uses solution treatment followed by aging treatment. Steps 1 to 6 are exactly the same as in Example 2. Rule 1: Hold at 1080℃ for 8 hours, then air cool; hold at 700℃ for 16 hours, then air cool. System 2: Keep at 980℃ for 8 hours and then air cool; keep at 700℃ for 16 hours and then air cool.

[0069] Comparative Example 3 This comparative example provides a method for preparing a small round GH4033 high-temperature alloy bar with a diameter of 8mm. The only difference from Example 3 is that the heat treatment in step 7 uses solution treatment followed by aging treatment. Steps 1 to 6 are exactly the same as in Example 3. Rule 1: Hold at 1080℃ for 8 hours, then air cool; hold at 700℃ for 16 hours, then air cool. System 2: Keep at 980℃ for 8 hours and then air cool; keep at 700℃ for 16 hours and then air cool.

[0070] Comparative Example 4 This comparative example provides a method for preparing GH4033 high-temperature alloy small round bars with a diameter of 8mm. The only difference from Example 3 is that the cold drawing and annealing process is replaced by the traditional turning and peeling process. Specifically, it includes the following steps: Steps 1 to 4 are the same as in Example 3; Step 5: Surface Treatment After rough straightening of the 11mm diameter bar, the outer skin is removed to a diameter of 8.2mm, and then the bar is ground using a centerless grinder with a grinding amount of 0.07mm to obtain a semi-finished bar with a surface roughness Ra=1.6μm.

[0071] Step 6: Heat treatment The material was kept at 710℃ for 16 hours and then air-cooled. The actual measured diameter of the finished product was 8.03 mm. The yield rate was 58%.

[0072] Comparative Example 5 The only difference between this comparative example and comparative example 4 is that the heat treatment in step 6 uses a solution treatment followed by aging. Steps 1 to 5 are exactly the same as those in comparative example 4. Rule 1: Hold at 1080℃ for 8 hours, then air cool; hold at 700℃ for 16 hours, then air cool. System 2: Keep at 980℃ for 8 hours and then air cool; keep at 700℃ for 16 hours and then air cool.

[0073] Performance testing The GH4033 high-temperature alloy small round materials prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested for grain size according to ASTM E112, room temperature tensile properties according to YB / T5245-93 standard requirements, and high temperature tensile properties according to GJB 2611A-2020 standard requirements. The results are shown in Tables 1 to 3.

[0074] Table 1 Grain size Note: "Pristine state" refers to bars that have not undergone aging treatment, or bars that have undergone solution treatment followed by aging treatment; "Heat-treated state" refers to bars that have undergone aging treatment, or bars that have undergone solution treatment followed by aging treatment. The percentage of grain size in the heat-treated state refers to the proportion of that grain size in the mixed-grain structure.

[0075] Table 2 Tensile strength at room temperature Table 3 Tensile strength at high temperature (700℃) 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 or improvements 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 small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars, characterized in that, Includes the following steps: S1, the raw materials are melted under vacuum and then cast to obtain an ingot; S2, using the ingot as a consumable electrode, and employing a CaF2-Al2O3-CaO-electrolytic MgO slag system, directional solidification electroslag remelting is carried out under an inert atmosphere, with the melting rate controlled at 1.5~3.0 kg / min, to obtain an electroslag ingot. S3, the electroslag ingot is heated and held at a certain temperature, and then subjected to multiple forging processes to obtain a round bar billet; S4, after heating and holding the round bar billet at a certain temperature, rough rolling and finish rolling are performed sequentially to obtain a hot-rolled bar billet; S5, the hot-rolled bar billet is processed into a small round billet of the target diameter by a multi-pass cold drawing process that alternates between intermediate annealing and cold drawing. S6, the small round billet is centerlessly ground, and then the ground billet is aged at 690~710℃ and air-cooled to obtain small-sized nickel-chromium-based precipitation hardening deformed high-temperature alloy bars.

2. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S2, the directional solidification electroslag remelting includes an arc initiation and slag formation stage, a steady-state smelting stage, and a feeding stage: During the arc initiation and slag formation stage, the current is controlled at 1000~3000A and the voltage at 50~63V after energization; slag is added in 2~3 batches, and the current is increased to 5400A~5600A during the slag addition process. The steady-state melting current is 6500~9500A and the voltage is 60~90V. An axial temperature gradient is formed in the crystallizer through the bottom of the water-cooled crystallizer, so that the molten metal solidifies layer by layer from bottom to top along the axial direction. The feeding stage includes: when the remaining mass of the electrode is 6% to 9%, the current is reduced to 3000 to 4500A and the voltage is reduced to 30 to 50V, and feeding is carried out for 30 to 50 minutes; after power is cut off, the furnace is cooled for 30 to 60 minutes, and the ingot temperature is reduced to below 600℃ for demolding and air cooling.

3. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 2, characterized in that, The axial temperature gradient is 100~500℃ / cm.

4. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S3, the heating and heat preservation temperature is 1110~1180℃, and the heat preservation time is 1~3h; and / or In S3, the total deformation is controlled at 60%~85%; and / or In S3, the final forging temperature shall not be lower than 920℃.

5. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1 or 4, characterized in that, In S3, the multi-fire forging specifically includes: The first heating is carried out at 1160~1180℃ and held for 1.5~2.5 hours, then forged into a square billet with a cross-sectional side length of 240~260mm; The second heating is carried out at 1140~1160℃ and held for 1.5~2 hours, then forged into a square billet with a cross-sectional side length of 180~200mm; The third heating is carried out at 1120~1140℃ and held for 1~1.5 hours, forging into a round billet with a diameter of 140~170mm.

6. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S4, the heating and heat preservation temperature is 1100~1150℃, and the heat preservation time is 0.5~3h; and / or In S4, the billet is first roughed in two passes and then finished in one pass to form a hot-rolled bar billet with a diameter of 10-15 mm; the total number of finishing passes is 5-7, the total deformation is 70%-97%, the deformation per pass is 15%-20%, and the rolling speed is 0.8-1.2 m / s; and / or In S4, the diameter of the hot-rolled bar billet is 10~15mm.

7. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S5, the total number of cold drawing passes is 4 to 8, the total cold drawing deformation is 70% to 90%, the cold drawing deformation per pass is 8% to 25%, and the cold drawing speed is 0.5 to 1.0 m / s. Before each cold drawing pass, an intermediate annealing stress relief is performed at a temperature of 980 to 1130℃, and the temperature is maintained for 1 to 1.5 hours before air cooling.

8. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S5, the target diameter is 4~8mm.

9. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S6, the grinding amount of the centerless grinding is 0.05~0.1mm, and the surface roughness Ra after grinding is ≤1.6μm.

10. The method for preparing small-diameter nickel-chromium-based precipitation-hardening deformed superalloy bars as described in claim 1, characterized in that, In S6, the time for the aging process is 15.5~16.5h.

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