A method of machining an in 718 axial flow blade

Abstract

The application provides a processing method of an IN718 axial flow blade, uses incomplete recrystallization forging technology, makes the blade forgings without longitudinal low-magnification "bright strip", obtains more homogenized grain structure, improves the forging quality and production efficiency, the incomplete recrystallization forging technology is adopted, the blank temperature is controlled in a certain range through process parameters such as blank structure, equivalent strain and deformation rate in the die forging process, the blank temperature drop can be effectively reduced, meanwhile, the grain structure can be effectively refined under a small deformation amount, and the longitudinal low-magnification "bright strip" of the forged forgings after final forging is eliminated.

Description

Technical Field

[0001] This invention relates to the technical field of axial flow blade processing methods, specifically a processing method for IN718 axial flow blades. Background Technology

[0002] IN718 alloy is a precipitation-hardening nickel-chromium-iron alloy containing niobium and molybdenum. It is one of the most important high-temperature alloy materials in aero-engines and gas turbines, mainly used to manufacture high-temperature critical components such as turbine disks, compressor disks, and compressor blades. Therefore, the quality stability of forgings directly determines the operating condition and lifespan of aero-engines and gas turbines.

[0003] The microstructure and properties of IN718 alloy are highly sensitive to hot working processes. In the traditional die forging process, IN718 alloy is generally processed by full recrystallization. During the preparation of die forgings, due to the irregular geometric features of the blade shank and the influence of unavoidable friction and billet shape, a dead deformation zone with insufficient strain appears around the outer circumference of the blade shank, resulting in coarse grains of varying depths around the shank. At the same time, the strain gradient between the blade shank core and the outer circumference is large, and bright band abnormalities appear in the longitudinal low magnification of the shank in different batches, resulting in poor quality of the machined axial blades and low production efficiency. Summary of the Invention

[0004] To address the problem that existing axial flow blade processing often results in coarse grain anomalies of varying depths and bright band anomalies around the shank, leading to poor quality and low production efficiency, this invention provides a processing method for IN718 axial flow blades. This method utilizes incomplete recrystallization forging technology to eliminate longitudinal low-magnification bright band anomalies in the blade forgings, resulting in a more uniform grain structure, improved forging quality, and increased production efficiency.

[0005] The technical solution is as follows: A method for processing IN718 axial flow blades, characterized by the following steps:

[0006] S1. Preparing the blank

[0007] The billet of the required specifications is prepared by fast forging or radial forging process, and the grain size of the billet is grade 7 to 10.

[0008] S2, Blank Spraying

[0009] The blank is heated to 200°C and held at that temperature for more than 1 hour. The entire surface of the blank is then coated with glass lubricant with a thickness of 0.05 to 0.1 mm.

[0010] S3, Heating and heat preservation

[0011] Put the blank into the heating furnace with temperature ≤800℃, the heating furnace starts to heat up, the heating furnace temperature rises from 800℃ to 980±10℃ at least 5h; after the heating furnace temperature reaches 980±10℃, keep at least 2h;

[0012] S4, forging

[0013] Transfer the blank to the press, the press presses the blank into a blade forging, the deformation rate is controlled at 300-500mm / s, one fire forming, and the equivalent strain of the press die forging process is ≤1, the final forging temperature when the die forging is finished is ≥900℃, and the blank is air cooled after forging.

[0014] Further characterized in that: in S1, the blank is IN718 alloy; the size specification of the blank is φ40x(170-200)mm, and the total length of the blank processed into an axial flow blade is ≤200mm;

[0015] In S4, the mold surface quality is required to meet Ra3.2um during die forging, and the mold needs to be nitrided, the mold uses water-based graphite lubrication, and the mold preheating temperature is ≥300℃;

[0016] In S4, after die forging, the blank is first solid solution heat treated at 950℃ for 60min, air cooled; then aged heat treated at 720℃ for 480min, furnace cooled to 620℃, 620℃ for 600min, air cooled.

[0017] After adopting the above structure, the incomplete recrystallization forging technology is adopted, the blank temperature is controlled within a certain range through process parameters such as blank organization, equivalent strain and deformation rate of die forging process, the blank temperature drop can be effectively reduced, the grain organization can be effectively refined under a small deformation, and the longitudinal macroscopic no-bright band abnormality of the forged piece after final forging is effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is an IN718 alloy axial flow blade forging structure schematic diagram of the present application;

[0019] Figure 2 It is an IN718 alloy axial flow blade forging longitudinal macroscopic photo of the present application;

[0020] Figure 3 It is an IN718 alloy axial flow blade forging grain size photo of the present application. DETAILED DESCRIPTION

[0021] A processing method of IN718 axial flow blade, comprising the following steps:

[0022] S1, preparing a blank

[0023] The blank with the required specification is prepared by using the quick forging or radial forging process, and the grain size of the blank is 7-10;

[0024] S2, blank spraying

[0025] The blank is heated to 200℃ and kept for more than 1h, wherein the blank holding time is proportional to the thickness of the blank, the full surface of the blank is sprayed with a glass lubricant, the glass lubricant is selected as SA-35 high-temperature alloy forging special glass lubricant, and the thickness requirement is 0.05-0.1mm;

[0026] S3, heating and holding

[0027] The blank is placed in a heating furnace with a temperature of ≤800℃, the heating furnace starts to heat up, and it takes at least 5h for the temperature of the heating furnace to rise from 800℃ to 980±10℃; after the furnace temperature of the heating furnace reaches 980±10℃, it is kept for at least 2h;

[0028] S4, forging

[0029] The blank is transferred to the press, the blank is pressed into a blade forging by the press, the deformation rate is controlled at 300-500mm / s, one fire is formed (i.e. the number of blank die forging hammering is one hammer), and the equivalent strain of the die forging process is ≤1, the final forging temperature when the die forging is finished is ≥900℃, and the blank is air-cooled after forging.

[0030] Preferably, in S1, the blank is IN718 alloy; the size specification of the blank is φ40×(170-200)mm, and the total length of the blank processed into an axial flow blade is ≤200mm;

[0031] Preferably, in S4, the surface quality of the die meets Ra3.2um during the die forging process, and the die needs to be nitrided to improve the wear resistance of the die; and the die needs to be lubricated, and the die uses water-based graphite lubrication; the preheating temperature of the die is ≥300℃.

[0032] Preferably, the blank is heat treated after die forging, first solid solution heat treatment at 950℃×60min, air cooling; then aging heat treatment at 720℃×480min, furnace cooling to 620℃, 620℃×600min, air cooling.

[0033] The application adopts conventional fast forging or radial forging process to prepare blank of required specification when preparing blank, and the requirement for the structure of the blank is to ensure that the grain size reaches 7-10 levels, which is necessary for the grain size of the blank, and if the grain structure of the blank is uneven or coarse, it will lead to coarse grains or residual coarse grains in the subsequent forgings, and then affect the grain size of the forgings to not meet the requirements; at the same time, the surface of the blank is treated by spraying, which can effectively reduce the friction of metal flow in the die forging process, so as to effectively avoid the surface cracking problem in the die forging process; and the equivalent strain of the whole die forging process is ≤1, so as to ensure that incomplete recrystallization occurs in the whole die forging process, and the structure of the forgings is refined; when forging the IN718 alloy axial flow blade, the deformation rate is controlled at 300-500 mm / s, if the reduction is too fast, it is easy to cause high temperature rise in the blank, which is not conducive to obtaining fine grain structure, and if the reduction is too slow, the recrystallization of the structure is not easy to complete, which is not conducive to the refinement of the structure.

[0034] In summary, by optimizing and controlling the blank structure, the equivalent strain and the deformation rate of the die forging process, combined with the incomplete recrystallization forging technology, a stable, efficient and feasible IN718 alloy axial flow blade production process is formed. In the actual production process, through the incomplete recrystallization forging technology, the uniformity of the temperature from the center to the edge of the blank can be ensured; in addition, the deformation rate of the whole forging process is controllable, combined with the design of small deformation amount, the incomplete recrystallization of the internal structure of the forgings occurs, so as to achieve the purpose of refining the grains. The application comprehensively controls the blank structure, the equivalent strain and the deformation rate of the die forging process, so as to ensure that the IN718 alloy axial flow blade (such as Figure 1 ) has uniform and fine structure, the grain size reaches 10.5G-11.5G levels (such as Figure 3 ), and the longitudinal macroscopic bright band of the forgings is abnormal (such as Figure 2 ).

[0035] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited thereto, any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed by the application should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method of machining an IN718 axial flow blade characterised in that: It includes the following steps: S1, preparing a blank A blank of a required specification is prepared by using a quick forging or radial forging process, and the grain size of the blank is 7-10 levels; S2, blank spraying The blank is heated to 200 DEG C, and the full surface of the blank is sprayed with a glass lubricant with a thickness of 0.05-0.1 mm after being kept for more than 1 h; S3, heating and keeping The blank is put into a heating furnace with a temperature of less than 800 DEG C, the heating furnace starts to heat, and the temperature of the heating furnace is increased from 800 DEG C to 980 DEG C±10 DEG C for at least 5 h; after the temperature of the heating furnace reaches 980 DEG C±10 DEG C, it is kept for at least 2 h; S4, forging The blank is transferred to a press, the blank is pressed into a blade forging by the press, the deformation rate is controlled to be 300-500 mm / s, one fire is formed, and the equivalent strain of the press die forging process is less than or equal to 1, the final forging temperature when the die forging is completed is greater than or equal to 900 DEG C, and the blank is air-cooled after forging.

2. A method of machining an IN718 axial flow blade according to claim 1 characterised in that: In S1, the blank is IN718 alloy; the size specification of the blank is φ40x(170-200)mm, and the total length of the shaft flow blade processed from the blank is less than or equal to 200 mm.

3. The method of claim 1, wherein: In S4, during the die forging process, the surface quality of the die is required to meet Ra3.2um, and the die needs to be nitrided, the die uses water-based graphite lubrication, and the preheating temperature of the die is greater than or equal to 300 DEG C.

4. The method of claim 1, wherein: In S4, after the die forging, the blank is first solid solution heat treated at 950 DEG C for 60 min and air-cooled; then, the blank is aged heat treated at 720 DEG C for 480 min, furnace cooled to 620 DEG C, kept at 620 DEG C for 600 min, and air-cooled.

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