Method for producing fine-grained rod of difficult-to-deform superalloy

Abstract

The present application relates to the technical field of hot working, in particular to a preparation method of difficult-to-deform high-temperature alloy fine-grain rod material. The preparation method of the difficult-to-deform high-temperature alloy fine-grain rod material comprises the following steps: first warm package sleeve treatment and first plug welding are performed on a homogenization annealing ingot to obtain a first package sleeve blank; (b) the first package sleeve blank is heated to a first temperature and subjected to first heat treatment, and then upsetting and drawing treatment is performed on the heat-treated package sleeve blank to obtain an intermediate blank; (c) an antioxidant coating is coated on the surface of the intermediate blank, and then second warm package sleeve treatment and second plug welding are performed to obtain a second package sleeve blank; (d) the second package sleeve blank is heated to a second temperature and subjected to second heat treatment, and then hot extrusion and post-treatment are performed. The method can realize the preparation of homogeneous fine-grain rod materials in a full range of small, medium and large specifications, the grain size of the rod material reaches ASTM 10 level or above, and the method has the characteristics of low cost and high yield.

Description

Technical Field

[0001] This invention relates to the field of hot working technology, and more specifically, to a method for preparing fine-grained rods of difficult-to-deform high-temperature alloys. Background Technology

[0002] Due to their advantages such as a wide variety of alloy types, stable performance, and low manufacturing cost, wrought superalloys have been widely used in aerospace, ultra-supercritical units, industrial gas turbines, nuclear reactors and other fields, and are the most widely used type of superalloy.

[0003] Wrought superalloys refer to high-temperature alloys prepared by casting and forging (C&W) processes. Among these, ingot smelting and bar forging are two important processes in wrought superalloy manufacturing, while hot working is a key process step that transforms the as-cast structure into the forged structure through thermomechanical processes.

[0004] Currently, hot-working billet preparation mainly includes two types: forging and hot extrusion. Traditional forging is widely used in wrought high-temperature alloys with relatively low alloying levels. However, with increasing alloying levels, wrought high-temperature alloys face challenges such as high deformation resistance, narrow hot working windows, and susceptibility to cracking. This makes the forging process extremely difficult to control in terms of technology and microstructure, resulting in very low yields and serious problems such as uneven microstructure. Furthermore, traditional hot extrusion techniques mainly involve two methods: single hot extrusion and ingot upsetting + hot extrusion. In the ingot upsetting stage, the ingot deformation is severely uneven, exhibiting bulging, large deformation in the ingot core but small deformation at the edges. Complex alloys with narrow hot working temperature windows and significant heat exchange with the atmosphere during upsetting cause uneven ingot temperature fields, leading to cracking. It also easily causes microstructure inhomogeneity and deformation dead zones. This uneven microstructure cannot be eliminated in subsequent hot extrusion stages, resulting in uneven microstructure in the final bar stock.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One object of the present invention is to provide a method for preparing fine-grained rods of difficult-to-deform high-temperature alloys, so as to solve the above-mentioned technical problems.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] A method for preparing fine-grained rods of difficult-to-deform high-temperature alloys includes the following steps:

[0009] (a) The homogenized annealed ingot is subjected to a first temperature-encased treatment and a first plug welding to obtain a first-encased ingot blank;

[0010] (b) The first encased billet obtained in step (a) is heated to a first temperature and subjected to a first heat treatment, the first temperature being (T-50)℃ to T℃, where T is the γ′ phase complete dissolution temperature of the ingot; then the heat-treated encased billet is subjected to elongation and upsetting treatment to obtain an intermediate billet;

[0011] (c) The intermediate billet obtained in step (b) is subjected to a second temperature-encasing treatment and a second plug welding to obtain a second-encased billet;

[0012] (d) The second encapsulated billet obtained in step (c) is heated to a second temperature and subjected to a second heat treatment, followed by hot extrusion and post-treatment. The second temperature is (T-100)℃ to (T-20)℃.

[0013] In one embodiment, the method for preparing the homogenized annealed ingot specifically includes: subjecting the ingot to homogenization annealing treatment; the temperature of the homogenization annealing treatment is 1180-1200℃.

[0014] In one embodiment, the first heat-shrinking process specifically includes: placing the homogenized annealed ingot in a first heat-shrinking sleeve.

[0015] In one embodiment, during the first heat pack treatment, the preheating temperature of the first pack is 300-500°C.

[0016] In one embodiment, the ingot is machined to the outer diameter, flattened at the end, and rounded at the corners before undergoing the first temperature-shrinking process.

[0017] In one embodiment, the first heat treatment specifically includes: subjecting the first encased ingot blank to a first heat preservation treatment and a second heat preservation treatment at a first temperature.

[0018] In one embodiment, during the first heat treatment, the first heat treatment time is 5 to 10 hours.

[0019] In one embodiment, during the first heat treatment, the second heat treatment lasts for 2 to 5 hours.

[0020] In one embodiment, during the first heat treatment, the first encapsulated ingot is heated from room temperature to 480-550°C and held for 1.5-3 hours, then heated to 880-950°C and held for 3.5-5 hours, then heated to the first temperature and subjected to the first heat treatment and the second heat treatment.

[0021] In one embodiment, the elongation process specifically includes: elongating using a preheated elongation mold.

[0022] In one embodiment, the preheating temperature of the drawing die is 300–500°C.

[0023] In one embodiment, the elongation process is performed 1 to 3 times.

[0024] In one embodiment, the upsetting process specifically includes: after the elongation process, upsetting is performed using a preheated upsetting die.

[0025] In one embodiment, during the upsetting process, the preheating temperature of the upsetting mold is 300–500°C.

[0026] In one embodiment, during the upsetting process, the deformation amount of the intermediate billet in a single pass is 20% to 55%.

[0027] In one embodiment, during the upsetting process, the forging pressing rate is 1 to 100 mm / s.

[0028] In one embodiment, during the upsetting process, the final forging temperature of the alloy for each forging pass is not lower than T-50℃, where T is the γ′ phase complete dissolution temperature of the ingot.

[0029] In one embodiment, the preheating temperature of the second casing is 300–500°C.

[0030] In one embodiment, in step (c), an antioxidant coating is applied to the surface of the intermediate blank, followed by the second temperature sleeve treatment and the second plug welding.

[0031] In one embodiment, the intermediate blank further includes turning the outer diameter before applying the antioxidant coating.

[0032] In one embodiment, the intermediate blank after the second plug is welded is sandblasted and then coated with glass lubricant.

[0033] In one embodiment, the second heat treatment specifically includes: subjecting the second encased ingot to a third heat treatment and a fourth heat treatment in sequence at a second temperature.

[0034] In one embodiment, during the second heat treatment, the third heat treatment lasts for 5 to 10 hours.

[0035] In one embodiment, during the second heat treatment, the fourth heat treatment lasts for 2 to 5 hours.

[0036] In one embodiment, during the second heat treatment, the second encapsulated ingot is heated from room temperature to 480-550°C and held for 1.5-3 hours, then heated to 880-950°C and held for 3.5-5 hours, then heated to the second temperature and subjected to the third and fourth heat treatments.

[0037] In one embodiment, the extrusion rate during the hot extrusion process is 10 to 100 mm / s.

[0038] In one embodiment, during the hot extrusion process, the extrusion ratio is (3-6.5):1.

[0039] In one embodiment, the post-processing specifically includes: removing the casing and plug, followed by machining.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) This invention adopts a combined billet-making process of ingot-wrapped upsetting and hot extrusion to replace the traditional upsetting or direct extrusion billet-making process. This avoids the problems of deformation and cracking, uneven bar structure, long forging fire and low yield caused by the traditional billet-making process. It provides a practical, economical and efficient process method for the homogeneous fine grain control of difficult-to-deform high-temperature alloy bars with a strengthening phase of more than 40%.

[0042] (2) The present invention encases the homogenized annealed ingot in a stainless steel tube, which greatly reduces the heat loss due to heat exchange with the environment during the heat transfer and heat deformation process of the ingot, ensures the uniformity of the temperature field during the deformation process of the ingot, and avoids problems such as cracking, non-recrystallization and mixed crystals caused by temperature drop.

[0043] (3) In the elongation process of this invention, the as-cast structure of the outer circumference of the ingot is broken, ensuring the deformation of the outer circumference of the billet, which can improve the process plasticity of the billet, adjust the height-to-diameter ratio of the billet, and provide a primary intermediate billet for subsequent upsetting with large deformation. The primary intermediate billet is upset, which breaks the as-cast structure of the billet core, thereby realizing the transformation of the as-cast structure from the core to the outer circumference of the billet into a deformed structure, which can greatly improve the process plasticity of the billet, while expanding the billet size and providing a secondary intermediate billet for subsequent extrusion with large deformation.

[0044] (4) The method of the present invention, based on the secondary intermediate billet obtained by the previous upsetting and drawing process, performs large deformation extrusion billet at a lower temperature. Due to the triaxial compressive stress characteristics of the hot extrusion process, the intermediate billet can achieve large deformation without cracking. At the same time, it can achieve uniform control of the combined deformation of the billet upsetting and drawing process (core is larger than outer edge) and the extrusion process (core is smaller than outer edge), thereby obtaining homogeneous fine-grained rods with a grain size of ASTM grade 10 or higher. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a microstructure diagram of the homogeneous fine-grained rod of the difficult-to-deform high-temperature alloy prepared in Example 1 of the present invention;

[0047] Figure 2 This is a microstructure diagram of the homogeneous fine-grained rod of the difficult-to-deform high-temperature alloy prepared in Example 2 of the present invention;

[0048] Figure 3 The microstructure diagram is of the bar stock in Comparative Example 1;

[0049] Figure 4 This is a microstructure diagram of the bar stock from Comparative Example 2. Detailed Implementation

[0050] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0051] A method for preparing fine-grained rods of difficult-to-deform high-temperature alloys includes the following steps:

[0052] (a) The homogenization annealing is subjected to a first temperature encapsulation treatment and a first plug welding to obtain a first encapsulated ingot;

[0053] (b) The first encased billet obtained in step (a) is heated to a first temperature and subjected to a first heat treatment, the first temperature being (T-50)℃ to T℃, where T is the full melting temperature of the ingot; then the heat-treated encased billet is subjected to elongation and upsetting treatment to obtain an intermediate billet;

[0054] (c) The intermediate billet obtained in step (b) is subjected to a second temperature-encased treatment and a second plug welding to obtain a second-encased billet;

[0055] (d) The second encased billet obtained in step (c) is heated to a second temperature and subjected to a second heat treatment, followed by hot extrusion and post-treatment. The second temperature is (T-100)℃ to (T-20)℃, where T is the γ′ phase complete dissolution temperature of the ingot.

[0056] The method in this invention can significantly reduce heat loss due to heat exchange with the environment during the heat transfer and hot deformation process of the ingot, ensuring the uniformity of the temperature field during the ingot deformation process. Upsetting and drawing are performed near the γ′ complete melting temperature, and the re-dissolution of the γ′ phase reduces the deformation resistance of the alloy and improves the process plasticity, breaking down the coarse as-cast structure and the intermediate billet structure with significantly reduced deformation resistance. After the intermediate billet is encased twice, it is hot-extruded at a lower temperature. The process plasticity of the upset intermediate billet is improved. At the same time, the precipitation of the γ′ phase at a lower temperature can realize grain boundary pinning and provide nucleation sites for recrystallization, thereby refining the grains. Due to the triaxial compressive stress characteristics of the hot extrusion process, the intermediate billet can achieve a large deformation without cracking, thus realizing the preparation of homogeneous fine-grained rods from large-size, difficult-to-deform ingots, with the grain size of the rods reaching ASTM grade 10 or above.

[0057] The ingot-wrapping upsetting and drawing method of this invention can solve the problems of forging cracking caused by temperature drop during the billet-opening process of large-sized ingots of complex alloyed and difficult-to-deform alloys, uneven microstructure inheritance caused by uneven deformation during simple upsetting, and low yield due to large machining allowance of intermediate billets. The hot extrusion technology of intermediate billets during wrapped upsetting and drawing can solve the microstructure inhomogeneity caused by reduced radial deformation of large-sized difficult-to-deform alloy upsetting and drawing billets. Hot extrusion compensates for the deformation, ensuring sufficient deformation at the core, radius, and edges of large-sized ingots, enabling the preparation of large-sized billets; simultaneously, it achieves billet shaping, improving the yield of billets. This differs from the radial forging process in the "fast forging + radial forging" billet-opening process, where radial forging only achieves billet shaping and supplementary surface deformation. Complex alloys and difficult-to-deform large-size ingots have high deformation resistance. Direct extrusion requires high equipment capacity and causes severe die wear, making it unsuitable for large-scale application. The ingot encasing upsetting and drawing + hot extrusion process of this invention can realize the preparation of homogeneous fine-grained rods of small, medium and large sizes from large-size ingots of difficult-to-deform alloys, reducing the requirements for extrusion equipment capacity, reducing costs, and making it suitable for large-scale application.

[0058] In one embodiment, consumable ingots are prepared using vacuum induction melting + vacuum arc remelting (double melting process), vacuum induction melting + protective atmosphere electroslag melting (double melting process), or vacuum induction melting + protective atmosphere electroslag melting + vacuum arc remelting (triple melting process). In another embodiment, the homogenization annealing ingot preparation method specifically includes: subjecting the ingot to homogenization annealing treatment; the homogenization annealing treatment temperature is 1180–1200℃, for example, 1185℃, 1187℃, 1190℃, 1195℃, or 1200℃. During homogenization annealing, elements in the alloy undergo solid-state diffusion, which can eliminate or reduce intragranular segregation, thereby improving the performance of the ingot or casting.

[0059] In one embodiment, the consumable ingot alloy includes, but is not limited to, difficult-to-deform high-temperature alloys with a reinforcing phase exceeding 40%. For example, difficult-to-deform high-temperature nickel-based alloys, such as GH4151 alloy.

[0060] In one embodiment, after homogenization annealing and before the first warm-walling treatment, the ingot undergoes external turning, end face flattening, and corner rounding. In another embodiment, the first warm-walling treatment specifically includes placing the homogenized annealed ingot in a preheated first sleeve, the first sleeve comprising a seamless steel pipe. In one embodiment, the preheating temperature of the first sleeve is 300–500°C, for example, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 470°C, etc. Warm-walling the ingot at a suitable preheating temperature achieves a tight fit; after cooling to room temperature, the end caps are then welded.

[0061] In one embodiment, the first heat treatment specifically includes: sequentially performing a first heat treatment and a second heat treatment at a first temperature. That is: the first wrapped ingot is placed in the furnace at room temperature, heated to the first temperature, and then subjected to a first heat treatment for a duration of 5 to 10 hours, such as 6 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, etc.; after removing the aluminum silicate fiber cotton, it is placed back in the furnace for a second heat treatment for a duration of 2 to 5 hours, such as 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc.

[0062] In one embodiment, during the first heat treatment, the first encapsulated ingot is heated from room temperature to 480–550°C (e.g., 485°C, 490°C, 495°C, 500°C, 550°C, etc.) and held at that temperature for 1.5–3 hours (e.g., 1.5 hours, 2 hours, 3 hours, etc.), then heated to 880–950°C (e.g., 890°C, 900°C, 905°C, etc.) and held at that temperature for 3.5–5 hours (3.5 hours, 4 hours, 4.5 hours, 5 hours, etc.), then heated to the first temperature and subjected to the first heat treatment and the second heat treatment.

[0063] In one embodiment, the drawing process specifically includes: drawing the billet using a preheated drawing die to obtain a primary intermediate billet. The drawing die can be a U-die or a flat die for drawing. In one embodiment, the preheating temperature of the drawing die is 300–500°C, for example, 320°C, 350°C, 370°C, 400°C, 420°C, 450°C, 470°C, etc. In one embodiment, the drawing process is performed 1–3 times.

[0064] In one embodiment, the upsetting process specifically includes: after the elongation process, upsetting is performed using a preheated upsetting die. In one embodiment, the preheating temperature of the upsetting die during the upsetting process is 300–500°C, for example, 320°C, 350°C, 370°C, 400°C, 420°C, 450°C, 470°C, etc. In one embodiment, during the upsetting process, the single deformation amount of the intermediate billet is 20%–55%, for example, 25%, 30%, 35%, 40%, 45%, 50%, etc. In one embodiment, during the upsetting process, the forging pressing rate is 1–100 mm / s, for example, 5 mm / s, 10 mm / s, 20 mm / s, 40 mm / s, 50 mm / s, 70 mm / s, 80 mm / s, 90 mm / s, 100 mm / s, etc. In one embodiment, during the upsetting process, the final forging temperature of the alloy in each forging pass is not lower than T-50℃, and the final forging temperature of the alloy in each forging pass is T-40℃, T-30℃, T-200℃, or T-10℃, where T is the γ′ phase complete dissolution temperature of the ingot.

[0065] In one embodiment, the preheating temperature of the second sheath is 300–500°C, for example, 320°C, 350°C, 370°C, 400°C, 430°C, 450°C, 490°C, etc. In one embodiment, in step (c), an antioxidant coating is applied to the surface of the intermediate blank, followed by the second sheathing treatment and welding of the second plug. The antioxidant coating in this invention is a conventional antioxidant coating in the prior art. In one embodiment, the intermediate blank further includes turning its outer diameter before applying the antioxidant coating. In one embodiment, the intermediate blank after welding the second plug is sandblasted and then coated with glass lubricant. The front plug is machined to a certain taper to fit the extrusion die core in terms of dimensions, thus achieving the functions of positioning and guiding flow. In one embodiment, after cooling to room temperature, the two ends are welded with the second plug.

[0066] In one embodiment, the second heat treatment specifically includes: subjecting the second encased ingot to a third holding treatment and a fourth holding treatment sequentially at a second temperature. In one embodiment, during the second heat treatment, the duration of the third holding treatment is 5–10 hours, such as 5.5 hours, 6 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, or 10 hours. In one embodiment, during the second heat treatment, the duration of the fourth holding treatment is 2–5 hours, such as 2.5 hours, 3 hours, 3.5 hours, 4 hours, or 4.5 hours. In one embodiment, during the second heat treatment, the second encased ingot is heated from room temperature to 480–550°C (e.g., 485°C, 490°C, 495°C, 500°C, 550°C, etc.) and held at that temperature for 1.5–3 hours (e.g., 1.8 hours, 2 hours, 3 hours, etc.), then heated to 880–950°C (e.g., 890°C, 900°C, 905°C, etc.) and held at that temperature for 3.5–5 hours (3.8 hours, 4 hours, 4.5 hours, 5 hours, etc.), then heated to the second temperature and subjected to the third and fourth heat treatments.

[0067] In one embodiment, during the hot extrusion process, the extrusion rate is 10–100 mm / s, for example, 5 mm / s, 10 mm / s, 25 mm / s, 45 mm / s, 50 mm / s, 60 mm / s, 75 mm / s, 90 mm / s, 95 mm / s, etc. In one embodiment, during the hot extrusion process, the extrusion ratio is (3–6.5):1, for example, 4.5:1, 5:1, 5.5:1, etc. In one embodiment, during the hot extrusion process, a lubricant is placed between the extrusion die core and the second sheathed billet; the lubricant includes a glass pad.

[0068] In one embodiment, the post-processing includes: removing the casing and plug, followed by machining.

[0069] In a preferred embodiment, the method for preparing fine-grained rods of difficult-to-deform high-temperature alloys includes the following steps:

[0070] Step 1 (Ingot Processing): Ingots are prepared using vacuum induction melting + vacuum consumable remelting (double melting process), vacuum induction melting + protective atmosphere electroslag melting (double melting process), or vacuum induction melting + protective atmosphere electroslag melting + vacuum consumable remelting (triple melting process). The alloys involved include, but are not limited to, difficult-to-deform high-temperature alloys with strengthening phases exceeding 40%. The ingot specifications are consumable ingots with diameters of Φ320mm to 600mm (e.g., Φ508mm). The consumable ingots are subjected to high-temperature diffusion homogenization annealing to obtain homogenized annealed ingots.

[0071] Step 2 (Ingot Sheathing): The homogeneous annealed ingot is machined to a rounded outer diameter, flattened end face, and rounded corners to obtain a homogeneous annealed ingot blank. A seamless steel pipe is used as an intermediate sleeve, and the intermediate sleeve is preheated in a heating furnace at 300-500℃. After the intermediate sleeve is removed, the annealed ingot blank is placed into the preheated intermediate sleeve for warm sheathing to achieve a tight fit. After cooling to room temperature, the front and rear plugs are welded to obtain the sheathed ingot blank.

[0072] Step 3 (Ingot Upsetting and Drawing): Place the wrapped ingot into the furnace at room temperature and heat it to the γ′ melting temperature T. γ′-solve -(10~20)℃, hold for 5~10h, remove the aluminum silicate fiber cotton and put it back into the furnace for another 2~5h; use a dummy material to preheat the drawing with a U-die or flat die to 300~500℃, and draw the wrapped billet 1~3 times to obtain a primary intermediate billet; use a dummy material to preheat the upsetting with a flat die to 300~500℃, and upset the primary intermediate billet, with a single upsetting deformation of 20%~55%, a forging pressing rate of 1~100mm / s, and the final alloy forging temperature of each forging fire shall not be lower than T γ′-solve -(10~50)℃ to obtain a secondary intermediate billet, and then wrap the intermediate billet with aluminum silicate fiber cotton and slowly cool it to room temperature;

[0073] Step 4 (Intermediate Billet Wrapping): The outer diameter of the secondary intermediate billet is machined, and an anti-oxidation coating is evenly brushed onto the surface. The intermediate section sleeve is placed in a heating furnace for preheating at 300-500℃. After the intermediate sleeve is removed, the secondary intermediate billet is placed into the preheated intermediate sleeve for warm wrapping to achieve a tight fit. After cooling to room temperature, the front and rear plugs are welded. The front plug is machined into a certain taper to match the dimensions of the extrusion die core, so as to achieve the functions of positioning and guiding flow, thus obtaining the extruded billet.

[0074] Step 5 (Hot Extrusion): The extruded billet obtained in Step 4 is placed into the furnace at room temperature and heated to T. γ′-solve - (20~100℃), keep warm for 5~10h, take out the aluminum silicate fiber cotton and put it back into the furnace to keep warm for 2~5h, take it out of the furnace and perform hot extrusion. Prevent the glass pad between the extrusion die core and the extrusion billet as a lubricant. The extrusion rate is 10~100mm / s.

[0075] Step Six (Extrusion Bar Machining): Remove the steel sleeve, head plug and tail extrusion residue from the extruded bar obtained in Step Five, and machine the surface to obtain the finished bar.

[0076] The following explanation, in conjunction with specific embodiments, further clarifies the situation.

[0077] Example 1

[0078] The method for preparing Φ150mm GH4151 alloy homogeneous fine-grained rods includes the following steps:

[0079] (a) The GH4151 alloy Φ508mm consumable ingot prepared by vacuum induction melting + protective atmosphere electroslag melting + vacuum consumable remelting (three-stage melting process) was subjected to high-temperature diffusion homogenization annealing at 1190℃ to obtain a homogenized annealed ingot.

[0080] (b) The uniform annealed ingot obtained in step (a) is machined to a diameter, flattened to a flat end face, and chamfered with R10 fillets to obtain a uniform annealed ingot blank; a seamless steel pipe with a wall thickness of 10mm is used as an intermediate section sleeve, and the intermediate section sleeve is placed in a heating furnace and preheated to 500℃. After the intermediate sleeve is removed, the annealed ingot blank is placed into the preheated intermediate sleeve for warm encasement to achieve a tight fit; after cooling to room temperature, the front and rear plugs are welded to obtain the first encased ingot blank;

[0081] (c) The first encased billet is placed in the furnace at room temperature and heated according to the following procedure: heated to 500°C at room temperature, held for 2 hours, then heated to 900°C, held for 4 hours, then heated to 1155°C, held for 5 hours, then removed from the furnace, wrapped with cotton, and held at 1155°C for 5 hours; the dummy material is used to preheat the drawing die to 400°C, and the encased billet is drawn in two passes at a forging rate of 40 mm / s to obtain a Φ400 mm primary intermediate billet; the dummy material is used to preheat the upsetting die to 400°C, and the primary intermediate billet is upsetting with an upsetting deformation of 50% and a forging rate of 20 mm / s. The final alloy forging temperature for each forging pass shall not be lower than 1050°C to obtain a Φ400 mm secondary intermediate billet, which is then wrapped with aluminum silicate fiber cotton and slowly cooled to room temperature;

[0082] Step (d) involves turning the outer diameter of the secondary intermediate billet obtained in step (c), uniformly coating the surface with an anti-oxidation coating, preheating the intermediate sleeve in a heating furnace to 500°C, removing the intermediate sleeve, placing the secondary intermediate billet into the preheated intermediate sleeve for warm encapsulation to achieve a tight fit, and then welding the front and rear plugs after cooling to room temperature. The encapsulated extruded billet is then sandblasted and coated with glass lubricant. The front plug is machined to a certain taper to match the dimensions of the extrusion die core, thus achieving the functions of positioning and guiding flow, resulting in the second encapsulated billet.

[0083] (e) The extruded billet obtained in step (d) is placed into the furnace at room temperature and heated according to the following conditions: the temperature is raised to 500°C and held for 2 hours, then raised to 900°C and held for 4 hours, then raised to 1080°C and held for 5 hours. After that, it is taken out of the furnace, wrapped with cotton, and then held at 1080°C for 5 hours. It is then taken out of the furnace for hot extrusion. The time from the extruded billet to the extruder is 100 seconds. A glass pad is used as a lubricant between the extrusion die core and the extruded billet. The extrusion ratio is 5:1 and the extrusion rate is 60 mm / s to obtain Φ180 mm extruded bar. After being wrapped with aluminum silicate fiber cotton, it is slowly cooled to room temperature.

[0084] (f) Remove the steel sleeve, head plug and tail extrusion residue from the extruded bar obtained in step (e), and machine the surface to obtain a Φ150mm finished bar.

[0085] The microstructure of the homogeneous fine-grained rod prepared in this embodiment is shown in the figure below. Figure 1 As shown.

[0086] Example 2

[0087] A method for preparing Φ300mm homogeneous fine-grained GH4151 alloy rods includes the following steps:

[0088] (a) The GH4151 alloy Φ508mm consumable ingot prepared by vacuum induction melting + protective atmosphere electroslag melting + vacuum consumable remelting (three-stage melting process) is subjected to high-temperature diffusion homogenization annealing at 1200℃ to obtain a homogenized annealed ingot.

[0089] (b) The uniform annealed ingot is machined to make the outer circle, flatten the end face and chamfer R10 corners to obtain a uniform annealed ingot blank; a seamless steel pipe with a wall thickness of 10mm is used as the intermediate section sleeve, and the intermediate section sleeve is placed in a heating furnace to preheat at 500℃. After the intermediate sleeve is removed, the annealed ingot blank is placed into the preheated intermediate sleeve for warm encasement to achieve a tight fit; after cooling to room temperature, the front and rear plugs are welded to obtain the first encased ingot blank.

[0090] (c) Place the wrapped billet into the furnace at room temperature, heat it to 1155℃, hold it for 7 hours, remove the aluminum silicate fiber cotton, and place it back into the furnace to continue holding for 3 hours; use a dummy material to preheat the drawing die to 350℃, and draw the wrapped billet in 3 passes to obtain a Φ350mm primary intermediate billet; use a dummy material to preheat the upsetting die to 350℃, and upset the primary intermediate billet in 3 passes with an upsetting deformation of 50%, a forging pressing rate of 20mm / s, and an alloy final forging temperature of not less than 1050℃ for each forging pass to obtain a Φ650mm secondary intermediate billet, and wrap it with aluminum silicate fiber cotton before slowly cooling it to room temperature.

[0091] (d) The outer diameter of the secondary intermediate billet is turned, and an anti-oxidation coating is evenly applied to the surface. The intermediate sleeve is placed in a heating furnace and preheated to 350°C. After the intermediate sleeve is removed, the secondary intermediate billet is placed into the preheated intermediate sleeve for warm encapsulation to achieve a tight fit. After cooling to room temperature, the front and rear plugs are welded. The encapsulated extruded billet is sandblasted and coated with glass lubricant. The front plug is machined into a certain taper to match the dimensions of the extrusion die core, so as to achieve the functions of positioning and guiding, and thus the second encapsulated billet is obtained.

[0092] (e) The obtained second-encased billet is placed in a furnace under the following heating regime: the temperature is raised from room temperature to 500℃ and held for 2 hours, then raised to 900℃ and held for 4 hours, then raised to 1100℃ and held for 5 hours. After that, it is taken out of the furnace, wrapped with cotton, and then held at 1100℃ for 5 hours. It is then taken out of the furnace for hot extrusion. The time from the extruded billet to the extruder is 100 seconds. A glass pad is used as a lubricant between the extrusion die core and the extruded billet. The extrusion ratio is 5:1 and the extrusion rate is 70 mm / s to obtain a Φ320 mm extruded bar. After being wrapped with aluminum silicate fiber cotton, it is slowly cooled to room temperature.

[0093] (f) Remove the steel sleeve, head plug and tail extrusion residue from the extruded bar obtained in step (e), and machine the surface to obtain a Φ300mm finished bar.

[0094] The microstructure of the homogeneous fine-grained rod prepared in this embodiment is shown in the figure below. Figure 2 As shown.

[0095] Comparative Example 1

[0096] The traditional extrusion process for preparing bars includes the following steps:

[0097] (a) The consumable ingot prepared by the same triple melting process as in step (a) of Example 1 was subjected to high-temperature diffusion homogenization annealing at 1190°C to obtain a homogenized annealed ingot.

[0098] (b) Using the same method as step (b) in Example 1, the uniform annealed ingot obtained in step (a) is machined to a diameter, flattened to a flat end face and chamfered with R10 fillets to obtain a uniform annealed ingot blank; and the same encapsulation method is used to obtain an extruded ingot blank;

[0099] (c) Using the same method as step (e) in Example 1, the extruded billet is placed into the furnace at room temperature and heated using the same heat treatment regime; then it is taken out of the furnace for hot extrusion. The time from the extruded billet to the transfer to the extruder is ≤120s. A glass pad is used as a lubricant between the extrusion die core and the extruded billet. The extrusion ratio is 5:1 and the extrusion rate is 60mm / s to obtain Φ180mm extruded bar stock, which is then wrapped with aluminum silicate fiber cotton and slowly cooled to room temperature.

[0100] (d) Remove the steel sleeve, head plug and tail extrusion residue from the extruded bar obtained in step (c), and machine the surface to obtain a Φ150mm finished bar.

[0101] Φ150mm bars are produced using traditional extrusion processes. The ingots exhibit large deformation, with minimal deformation at the core but significant deformation at the edges. Furthermore, streamlines are prone to appearing along the bar's axis, as shown in the diagram below. Figure 3 As shown.

[0102] Comparative Example 2

[0103] The traditional forging process for preparing bars includes the following steps:

[0104] (a) The consumable ingot prepared by the same triple melting process as in step (a) of Example 2 was subjected to high-temperature diffusion homogenization annealing at 1200°C to obtain a homogenized annealed ingot.

[0105] (b) The uniform annealed ingot is machined to make the outer circle, flatten the end face and chamfer R10 corners to obtain a uniform annealed ingot blank with a height of L; the ingot blank is placed in the furnace at room temperature, heated to 1155℃, held for 7h, the aluminum silicate fiber cotton is removed to obtain the wrapped ingot blank, and then placed in the furnace to continue holding for 2h.

[0106] (c) Using a dummy material, the upsetting is preheated to 350°C with a flat die. The encased billet is then upset at 1155°C for ≤35s, upsetting to 0.7L. After upsetting, the residual encasing material on the surface is removed, and the billet is returned to the furnace for 3h. Then, the aluminum silicate fiber cotton is removed to obtain a primary intermediate billet, which is then placed back into the furnace for 2h of heat preservation.

[0107] (d) The wrapped billet is drawn twice at 1155℃ to L, resulting in three intermediate billets. After each drawing, the residual wrapping on the surface is removed and the billet is placed back into the furnace for 3 hours. Then, the aluminum silicate fiber cotton is removed and placed back into the furnace for 2 hours of heat preservation.

[0108] (e) Upset the cladding billet at 1145℃ for ≤40s until it reaches 0.6L, and obtain a four-stage intermediate billet. The post-upsetting treatment is the same as described in step (c).

[0109] (f) The four intermediate billets are drawn twice at 1145°C to L, to obtain the five intermediate billets. The post-drawing treatment is the same as described in step (d).

[0110] (g) Upset the five intermediate billets at 1135℃ for ≤45s until 0.5L is obtained, and the post-upset treatment is the same as described in step (c).

[0111] (h) The sixth intermediate billet is drawn twice at 1145℃ to L, to obtain the seventh intermediate billet. The post-drawing treatment is the same as described in step (d).

[0112] (i) The seven intermediate billets are drawn three times at 1135°C, with each drawing time ≤240s, to obtain ten intermediate billets. The post-drawing treatment is the same as described in step (d).

[0113] (j) The ten intermediate billets were rounded at 1135℃ to Φ330mm to obtain forged bars, which were then wrapped with aluminum silicate fiber cotton and slowly cooled to room temperature.

[0114] (k) The forged bar from step (j) is machined to obtain a finished bar with a diameter of 300 mm.

[0115] The traditional forging process for producing Φ300mm bars resulted in severely uneven ingot deformation, exhibiting characteristics such as bulging, significant deformation at the ingot core but minimal deformation at the edges, a narrow hot working temperature window for complex alloys that are difficult to deform, and severe heat exchange between the ingot and atmosphere during the upsetting process. These issues led to an uneven ingot temperature field and a tendency to crack. The resulting non-uniform microstructure is shown in the diagram below. Figure 4 As shown.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing fine-grained rods of difficult-to-deform high-temperature alloys, characterized in that, Includes the following steps: (a) The homogenized annealed ingot is subjected to a first temperature-encapsulated treatment and a first plug welding to obtain a first-encapsulated ingot blank; the preparation method of the homogenized annealed ingot specifically includes: homogenizing the ingot; the temperature of the homogenization annealing treatment is 1180~1200℃; the first temperature-encapsulated treatment includes: placing the homogenized annealed ingot in a first encapsulated container that has undergone preheating treatment, the preheating treatment temperature of the first encapsulated container is 300~500℃; and then cooling it to room temperature; (b) The first encased ingot obtained in step (a) is heated to a first temperature and subjected to a first heat treatment, the first temperature being (T-50)℃ to T℃, where T is the γ of the ingot. The phase complete melting temperature; then the heat-treated wrapped billet is drawn and upset to obtain an intermediate billet; the first heat treatment specifically includes: the first wrapped billet is subjected to a first heat preservation treatment and a second heat preservation treatment at a first temperature; after the first heat preservation treatment, the aluminum silicate fiber cotton is removed and the second heat preservation treatment is performed. During the first heat treatment, the first heat treatment lasts for 5 to 10 hours, and the second heat treatment lasts for 2 to 5 hours. Furthermore, the first encased ingot is heated from room temperature to 480 to 550°C and held for 1.5 to 3 hours, then heated to 880 to 950°C and held for 3.5 to 5 hours, and then heated to the first temperature and subjected to the first heat treatment and the second heat treatment. The drawing process specifically includes: drawing using a preheated drawing die; the preheating temperature of the drawing die is 300-500℃; and the drawing process is performed 1-3 times. The upsetting process specifically includes: after the elongation process, upsetting is performed using a preheated upsetting die; during the upsetting process, the preheating temperature of the upsetting die is 300-500℃; the single deformation amount of the intermediate billet is 20%-55%; the forging pressing rate is 1-100mm / s; the final forging temperature of the alloy in each forging pass is not lower than T-50℃, where T is the γ' phase complete dissolution temperature of the ingot; (c) The intermediate billet obtained in step (b) is subjected to a second temperature-encapsulated treatment and a second plug welding to obtain a second-encapsulated billet; the preheating temperature of the second encapsulated treatment is 300~500℃; after cooling to room temperature, the second plug welding is performed; (d) The second encased billet obtained in step (c) is heated to a second temperature and subjected to a second heat treatment, followed by hot extrusion and post-treatment. The second temperature is (T-100)℃ to (T-20)℃. The second heat treatment specifically includes: subjecting the second encased billet to a third heat preservation treatment and a fourth heat preservation treatment in sequence at the second temperature; after the third heat preservation treatment, the aluminum silicate fiber cotton is removed and then subjected to a fourth heat preservation treatment. During the second heat treatment, the third heat treatment lasts for 5 to 10 hours, and the fourth heat treatment lasts for 2 to 5 hours. Furthermore, the second encased ingot is heated from room temperature to 480 to 550°C and held for 1.5 to 3 hours, then heated to 880 to 950°C and held for 3.5 to 5 hours, and then heated to the second temperature to perform the third and fourth heat treatments. During the hot extrusion process, the extrusion rate is 10-100 mm / s and the extrusion ratio is (3-6.5):

1.

2. The method for preparing fine-grained high-temperature alloy rods that are difficult to deform according to claim 1, characterized in that, Before undergoing the first temperature-sealing process, the ingot is machined to a diameter, flattened at the end, and rounded at the corners.

3. The method for preparing fine-grained high-temperature alloy rods that are difficult to deform according to claim 1, characterized in that, In step (c), an antioxidant coating is applied to the surface of the intermediate blank, followed by the second temperature sleeve treatment and the second plug welding.

4. The method for preparing fine-grained high-temperature alloy rods that are difficult to deform according to claim 1, characterized in that, After welding the second plug, the intermediate blank is sandblasted and then coated with glass lubricant.

5. The method for preparing fine-grained high-temperature alloy rods that are difficult to deform according to claim 1, characterized in that, The post-processing specifically includes: removing the casing and plug, and then performing machining.

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