A method of forging ultra-large in 718 alloy gas turbine vane ultra-fine grain

Abstract

The application provides a forging method for super-large IN718 alloy gas turbine blade ultra-fine grains, which can reach 8 or more, and can effectively ensure the surface quality of the blade, thereby improving the qualified rate of the forging. It comprises the following steps: blanking; chamfering; spraying; heating; upsetting; transferring the heated blank to a hydraulic machine to make a blank by upsetting, the deformation of the upsetting part being 50-70%; heating; drawing; transferring the heated upsetting piece to an air hammer to draw the blade body, the deformation of the drawing part being not less than 50%; heating; pre-forging; heating; final forging; transferring the heated pre-forging piece to a press to perform final forging, the temperature of the pre-forging piece being not less than 900 DEG C during the final forging, the number of hammering being one time during the final forging, and the deformation of each part during the final forging being 50-70%; edge cutting; heat treatment; final inspection.

Description

Technical Field

[0001] This invention relates to the field of blade forging technology, specifically to a forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains. Background Technology

[0002] IN718 alloy is the most important and typical high-temperature alloy material in aero engines and gas turbines. It is mainly used to manufacture high-temperature key components such as turbine disks, compressor disks and compressor blades. The quality stability of its forgings directly determines the working condition and life of aero engines and gas turbines.

[0003] IN718 alloy has a narrow forging processing window, and its microstructure and properties are sensitive to hot working parameters. Grain refinement can only be achieved through forging deformation and fragmentation; heat treatment only affects the strengthening phases. Ultra-large IN718 alloy gas turbine compressor blades require a grain size of grade 8 or finer. For example, [the following text appears to be unrelated and possibly a separate sentence fragment:] ... Figure 1 The image shows the largest IN718 alloy blade in China (projected size: 389.9mm). Figure 1 (Left end to right end of the middle blade) × 190.4 mm Figure 1 The forging of the middle blade (from the upper to the lower end) involves a large deformation to refine the grain size. Furthermore, due to the large blade chord width (190.4 mm) and the thinner blade on the exhaust side (8 mm), the temperature drops rapidly and material flow is intense on both sides of the blade chord width, frequently leading to forging cracking during hot working and inconsistent forging quality. This invention, through the study of hot working process parameters, yields a forging method for ultra-fine grain size in ultra-large IN718 alloy gas turbine blades. This method has significant engineering application value and importance for ensuring forging quality. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains. The forged ultra-large IN718 alloy gas turbine blades can achieve a grain size of grade 8 or higher, and can effectively ensure the surface quality of the blades, thereby improving the pass rate of forgings.

[0005] The technical solution is as follows: a forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains, characterized by the following steps: blanking: selecting IN718 alloy bar stock for blanking; Chamfering: Chamfering the ends of the blank; Spraying: applying glass lubricant to the surface of the blank. The billet is heated once, and the heating temperature is 990℃~1010℃. The holding time is the maximum effective thickness of the billet D×(1~2) minutes. Upsetting involves transferring the heated billet to a hydraulic press within 15 seconds to form the upsetting blank. The deformation of the upsetting part is 50% to 70%. After the upsetting is completed, the surface of the upsetting part is shot-blasted, polished, and then sprayed with glass lubricant. Secondary heating: The upsetting part is loaded into the furnace and heated to a temperature of 990℃~1010℃. The holding time is the maximum effective thickness D of the billet × (1~2) minutes. The heated upsetting part is transferred to an air hammer within 15 seconds for blade lengthening. The deformation of the lengthened part is not less than 50%. After that, the surface of the lengthened part is shot blasted, polished and then sprayed with glass lubricant again. The elongated part is heated three times. The heating temperature is 990℃~1010℃, and the holding time is the maximum effective thickness D of the billet × (1~2) minutes. Pre-forging involves transferring the heated, drawn part to a press within 15 seconds for pre-forging. A pre-forging die is used during pre-forging, which is lubricated with water-based graphite. The temperature of the pre-forging die is not lower than 400℃, and the number of hammer blows is once. The deformation of each part in the pre-forging process is 50% to 70%. After pre-forging, the surface of the pre-forged part is shot-blasted, polished, and then sprayed with glass lubricant. The pre-forged parts are heated four times. The heating temperature is 990℃~1010℃, and the holding time is the maximum effective thickness D of the billet × (1~2) minutes. Final forging involves transferring the heated pre-forged part to a press within 15 seconds for final forging. A final forging die is used, which is lubricated with water-based graphite. The die temperature is not lower than 400℃, and the final forging temperature is not lower than 900℃. The final forging is performed with one hammer blow, and the deformation of each part in the final forging process is 50% to 70%. Trim the edges, removing the flash around the final forging; Heat treatment involves heat treatment of the final forging through solution treatment and aging. Final inspection.

[0006] Its further features are: During the pre-forging and final forging processes, the temperature of the clamping tools used to hold the forgings shall not be lower than 200℃; The pre-forging die and the final forging die are made of H13 steel. The pre-forging die and the final forging die are nitrided and the surface quality of the die meets Ra3.2um. The thickness of the final forging is controlled within ±1.0mm, and the flash of the final forging satisfies: 1≤flash width to flash thickness ratio≤4; The solution treatment process is 980±10℃, held for 90 minutes; the aging treatment process is 718±6℃, held for 480 minutes; then the temperature is reduced to 621±6℃ at a furnace cooling rate of 55℃ / h, and held for 480 minutes. During the pre-forging and final forging steps, the press speed is 700 mm / s.

[0007] Beneficial effects: The ultra-large IN718 alloy gas turbine blades forged using the above method, by controlling the heating temperature of 990℃~1010℃ and the transfer time within 15 seconds during the forging process, ensure that the temperature of each part of the final forging is within the forgeable temperature range of the material. By controlling the shape and size of the pre-forging, the deformation of each part of the final forging is 50%~70%, resulting in recrystallized structures in each part of the forging. The final forging has a grain size of grade 8 or higher. Before upsetting, drawing, pre-forging, and final forging, the pre-forging billet with good surface quality is obtained by spraying lubricant, shot blasting, and grinding. At the same time, the surface hardness and roughness of the pre-forging and final forging dies, as well as the thickness and flash width-to-thickness ratio of the final forging, are controlled, thereby effectively avoiding the problem of forging cracking and improving the yield of forgings. Attached Figure Description

[0008] Figure 1 A schematic diagram of the structure of an ultra-large IN718 alloy gas turbine blade; Figure 2 Metallographic image (200X) of the root of the ultra-large IN718 alloy gas turbine rotor blade forging. Figure 3 Metallographic image (200X) of the blade body of the ultra-large IN718 alloy gas turbine rotor blade forging. Detailed Implementation

[0009] One such Figure 1The forging method for ultra-fine grains of ultra-large IN718 alloy gas turbine blades shown includes the following steps: Blanking: Selecting IN718 alloy bar stock for blanking; Chamfering: Chamfering the ends of the blank; Spraying: Spraying SA-35 high-temperature alloy forging special glass lubricant onto the surface of the blank; First heating: Loading the blank into the furnace and heating it to a temperature of 1000℃, holding it for a time equal to the maximum effective thickness D of the blank × (1~2) minutes; Upsetting: Transferring the heated blank to a hydraulic press within 15 seconds for upsetting, with a deformation of 50% at the upsetting part; After upsetting, shot blasting and grinding the surface of the upsetting part, and then spraying SA-35 high-temperature alloy forging special glass lubricant again; Second heating: Loading the upsetting part into the furnace and heating it to a temperature of 1000℃, holding it for a time equal to the maximum effective thickness D of the blank × (1~2) minutes; The heating time is D × (1~2) minutes, which is the maximum effective thickness of the billet. For the drawing, the heated upsetting part is transferred to an air hammer within 15 seconds for blade drawing, with a deformation of 50% in the drawn part. Afterwards, the surface of the drawn part is shot-blasted, polished, and then sprayed with SA-35 high-temperature alloy forging-specific glass lubricant. For the third heating, the drawn part is placed in a furnace and heated to 1000℃, with a holding time of D × (1~2) minutes, which is the maximum effective thickness of the billet. For pre-forging, the heated drawn part is transferred to a press within 15 seconds for pre-forging. A pre-forging die is used, made of H13 steel, and nitrided to ensure a surface quality of Ra3.2um. The pre-forging die uses water-based graphite lubricant, and the temperature of the pre-forging die is not lower than 4℃. 00℃, the clamping tool temperature for holding the forging is 200℃, the number of hammer blows is one, the press pressing speed is 700mm / s, the deformation of each part in the pre-forging process is 50%~70%, after the pre-forging is completed, the surface of the pre-forging is shot blasted and polished, and then sprayed with SA-35 high temperature alloy forging special glass lubricant; four heating, the pre-forging is loaded into the furnace and heated to a heating temperature of 1000℃, the holding time is the maximum effective thickness D of the billet × (1~2) minutes; final forging, the heated pre-forging is transferred to the press for final forging within 15s, the final forging temperature is not lower than 900℃, the final forging die is made of H13 steel, the final forging die is nitrided, the die surface quality meets Ra3.2um, the final forging die is made of water-based stone. Ink lubrication, final forging die temperature not lower than 400℃, clamping tool temperature for holding forgings 200℃, hammering frequency during final forging once, press speed 700mm / s, deformation of each part in the final forging process 50%~70%, thickness of final forging controlled within ±1.0mm; trimming, water jet method to remove flash around final forging, flash of final forging should meet: 1≤flash width to flash thickness ratio≤4; heat treatment, heat treatment of final forging through solution treatment and aging, solution treatment process is 980±10℃ for 90 minutes, aging treatment process is 718±6℃ for 480 minutes followed by furnace cooling (furnace cooling rate 55℃ / h) to 621±6℃ for 480 minutes; final inspection; warehousing.

[0010] Using the above method, 86 ultra-large IN718 alloy gas turbine blade forgings were forged in a single batch. These 86 forgings underwent fluorescent penetrant testing, and no defects such as cracks or folds were found. One forging was randomly selected for sampling and analysis of its low-magnification microstructure and grain size, yielding the following results: Figure 2 , Figure 3 The metallographic image shown has a qualified low-magnification structure with a grain size of 11G.

[0011] The above method requires controlling the number of forgings per batch to ≤100 pieces. If the number exceeds 100 pieces, for example, in the final forging process of ultra-large IN718 alloy gas turbine rotor blade forgings, after a batch production of 120 pieces in one batch, cracks appeared on the gas outlet edge of the final forgings. Upon inspection of the die surface quality, it was found that the cracked area had visible scratches at the die location, with a surface roughness of Ra12.5um, which did not meet the Ra3.2um requirement. After polishing with an 180-grit grinding wheel to Ra3.2um, no crack defects were found in the next 5 forgings produced.

[0012] Trial production revealed that when the final forging thickness of the ultra-large IN718 alloy gas turbine rotor blade forging reached the nominal thickness minus 1.5 mm, the flash width of the forging increased significantly. At this point, the flash width / flash thickness ratio was ≥4, and the cracking rate of the forging reached 90%. When the final forging thickness reached the nominal thickness plus 1.5 mm, the flash was too small, with the flash width / flash thickness ratio ≤1. Incomplete filling was observed in some areas of the forging, and dissection revealed mixed crystal formation up to 5G.

[0013] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains, characterized in that, It includes the following steps: Material cutting: Select IN718 alloy bar stock for cutting; Chamfering: Chamfering the ends of the blank; Spraying: applying glass lubricant to the surface of the blank. The billet is heated once, and the heating temperature is 990℃~1010℃. The holding time is the maximum effective thickness of the billet D×(1~2) minutes. Upsetting involves transferring the heated billet to a hydraulic press within 15 seconds to form the upsetting blank. The deformation of the upsetting part is 50% to 70%. After the upsetting is completed, the surface of the upsetting part is shot-blasted, polished, and then sprayed with glass lubricant. Secondary heating: The upsetting part is loaded into the furnace and heated to a temperature of 990℃~1010℃. The holding time is the maximum effective thickness D of the billet × (1~2) minutes. The heated upsetting part is transferred to an air hammer within 15 seconds for blade lengthening. The deformation of the lengthened part is not less than 50%. After that, the surface of the lengthened part is shot blasted, polished and then sprayed with glass lubricant again. The elongated part is heated three times. The heating temperature is 990℃~1010℃, and the holding time is the maximum effective thickness D of the billet × (1~2) minutes. Pre-forging involves transferring the heated, drawn part to a press within 15 seconds for pre-forging. A pre-forging die is used during pre-forging, which is lubricated with water-based graphite. The temperature of the pre-forging die is not lower than 400℃, and the number of hammer blows is once. The deformation of each part in the pre-forging process is 50% to 70%. After pre-forging, the surface of the pre-forged part is shot-blasted, polished, and then sprayed with glass lubricant. The pre-forged parts are heated four times. The heating temperature is 990℃~1010℃, and the holding time is the maximum effective thickness D of the billet × (1~2) minutes. Final forging involves transferring the heated pre-forged part to a press within 15 seconds for final forging. A final forging die is used, which is lubricated with water-based graphite. The die temperature is not lower than 400℃, and the final forging temperature is not lower than 900℃. The final forging is performed with one hammer blow, and the deformation of each part in the final forging process is 50% to 70%. Trim the edges, removing the flash around the final forging; Heat treatment involves heat treatment of the final forging through solution treatment and aging. Final inspection.

2. The forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains according to claim 1, characterized in that: The thickness of the final forging is controlled within ±1.0mm, and the flash of the final forging satisfies: 1≤flash width to flash thickness ratio≤4.

3. The forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains according to claim 1, characterized in that: During the pre-forging and final forging processes, the temperature of the clamping tools used to hold the forgings shall not be lower than 200℃.

4. The forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains according to claim 1, characterized in that: The pre-forging die and the final forging die are made of H13 steel. The die is nitrided and the surface quality of the die meets Ra3.2um.

5. A forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains according to any one of claims 1-4, characterized in that: During the pre-forging and final forging steps, the press speed is 700 mm / s.

6. A forging method for ultra-large IN718 alloy gas turbine blades with ultra-fine grains according to any one of claims 1-4, characterized in that: The solution treatment process is 980±10℃, held for 90 minutes, the aging treatment process is 718±6℃, held for 480 minutes, and then cooled to 621±6℃ at a furnace cooling rate of 55℃ / h, held for 480 minutes.

Images