Forging method for refining grain size of GH4169 alloy direct aging disc forgings

Abstract

This invention belongs to the field of forging technology and relates to a forging method for refining the grain size of GH4169 alloy direct aging disc forgings. The method includes: blanking and chamfering the edges of the GH4169 alloy bar; using a die to form a blank, wherein the blank is a disc-shaped blank with a larger top and smaller bottom and a convex outer circle, with a positioning groove at the upper end and a deformation groove at the lower end; the convex outer circle is divided from top to bottom into an outwardly inclined outer section, a cylindrical section, an inwardly inclined inner section, and a positioning curved surface section; the die cavity wall corresponding to the positioning curved surface section is used to fix the lower end of the bar; forging the upside-down blank; locking the positioning groove in the lower forging die cavity to form the inner transition area of ​​the disc forging legs and disc; under the constraint of the forging die, the blank metal flows outward, the metal between the positioning groove and the outer inclined section fills the legs, the cylindrical section fills the center of the disc, part of the inner inclined section fills the center of the disc, part of the disc edge is filled, and the deformation groove and positioning curved surface section fill the disc edge.

Description

Technical Field

[0001] This invention belongs to the field of forging technology and relates to a forging method for refining the grain size of GH4169 alloy direct aging disc forgings. Background Technology

[0002] GH4169 alloy is an iron-nickel-chromium based wrought superalloy. Its microstructure consists of a γ matrix, δ phase, carbides, and γ''(Ni3Nb) and γ''(Ni3(Al,Ti)) as strengthening phases. It is mainly used in key components of aerospace engines. A certain GH4169 disc forging is an important load-bearing component of an aero-engine. The required process type is direct aging, with a grain size of grade 6 for the bar stock and a grain size ≥10 for the forging. Die forging requires at least grade 4 refinement. During early trial production, it was found that after the billet was prepared, a lubricant was sprayed onto the entire billet, followed by die forging. During die forging, a large temperature difference was created in the temperature field. In areas with small deformation, incomplete recrystallization occurred, resulting in a low-magnification, coarse-grained, and inhomogeneous microstructure in the forging, and the grain size did not meet the ≥10 grade requirement. Summary of the Invention

[0003] Purpose of the invention: This invention proposes a forging method for refining the grain size of GH4169 alloy direct aging disc forgings, ensuring the temperature field during forging, and obtaining GH4169 alloy direct aging disc forgings with qualified grain size (≥10 grade) and uniform microstructure.

[0004] Technical solution:

[0005] A forging method for refining the grain size of GH4169 alloy direct aging disc forgings is provided, comprising:

[0006] Cut the GH4169 alloy bar and chamfer its edges;

[0007] The blank is made using a mold. The blank is a disc blank that is larger at the top and smaller at the bottom and has a convex outer circle. The upper end of the disc blank is provided with a positioning groove and the lower end is provided with a deformation groove. The convex outer circle is divided into an outwardly inclined section, a cylindrical section, an inwardly inclined section and a positioning curved surface section from top to bottom. The mold cavity wall corresponding to the positioning curved surface section is used to fix the lower end of the bar stock.

[0008] The upside-down billet is die-forged; the positioning groove is clamped in the lower forging die cavity to form the inner transition area of ​​the leg and the disc of the disc forging. Under the constraint of the forging die, the billet metal flows outward. The metal between the positioning groove and the outer inclined section fills the leg, the cylindrical section fills the center of the disc, the inner inclined section partially fills the center of the disc, partially fills the edge of the disc, and the deformation groove and the positioning curved surface section fill the edge of the disc.

[0009] Furthermore, prior to die forging, the method further includes:

[0010] Thermal insulation coatings are applied to different sections of the billet. The outer inclined section, cylindrical section, and inner inclined section of the billet, which are prone to rapid temperature loss during the forming of the disc forging, are coated with a coating that has better thermal insulation properties to better suppress temperature drop and ensure that the temperature of the outer circle of the billet remains ≥930℃ during the deformation process. Other areas of the billet are coated with ordinary coatings, and the temperature of the center of the billet is only required to be ≥930℃ during the deformation process. This ensures that the temperature field at the outer edge of the disc forging remains close to that at the core during the forging process.

[0011] Furthermore, the upside-down billet is die-forged, including:

[0012] The billet is heated to 980℃~1000℃. During heating, it is wrapped with heat-insulating cotton. During die forging, the billet is flipped so that the positioning surface of the billet contacts the mold for positioning.

[0013] The 100MN hydraulic press is used for die forging. The preheating temperature of the forging die is 250℃~350℃. The pressing speed is fast at first and then slows down. The deformation is controlled at 30%~42%.

[0014] Furthermore, the initial speed is 8-10 mm / s, and the subsequent speed is adjusted to 3-5 mm / s, with the billet height ratio between the initial and subsequent stages being 4:1.

[0015] Furthermore, blank preparation is carried out using a mold, including:

[0016] The bar stock is heated to 975℃~995℃. Before heating, the billet is sprayed with heat-insulating coating. The bar stock is placed in the die and slowly upset using a 2500t high-speed forging machine to form the rough shape required for die forging.

[0017] Furthermore, the overturned billet is die-forged, and then the method further includes:

[0018] The forgings are then heat-treated.

[0019] Furthermore, the heat treatment process is direct aging;

[0020] The aging temperature is 720℃, held for 480 minutes, cooled in the furnace at a rate of 50±10℃ / h to 620℃, held for 480 minutes, and then air-cooled.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention first employs a die-casting method to create a suitable rough shape for die forging. A positioning platform is fabricated within the die; the protrusion in the die not only increases the deformation amount and reduces the dead zone, but also avoids the need for additional positioning platforms on the bar stock and subsequent die forging machine, saving raw materials and reducing processes. Subsequently, an insulating coating is sprayed onto the rough shape, using different coatings applied in sections and varying the forging speed to ensure a uniform temperature distribution during forging. Under appropriate deformation, the grain size is refined, resulting in a uniformly structured disc forging. Attached Figure Description

[0023] Figure 1 This is the final forging drawing.

[0024] Figure 2 Forging pattern of tire mold.

[0025] Figure 3 This is a diagram of a rough-surfaced area sprayed with paint.

[0026] Figure 4 This is a diagram of a die forging material. Detailed Implementation

[0027] This invention provides a forging method for refining the grain size of GH4169 alloy direct aging disc forgings, resulting in disc forgings with a grain size ≥10 and good performance margin, such as... Figure 1 As shown, the GH4169 alloy disc forging includes, in sequence, a disc portion and upper and lower mounting edges, as shown. Figure 3 As shown, the forging die is coated with two different coatings on its upper and lower surfaces and outer edge, respectively; the method includes the following steps:

[0028] Step 1: Cut the GH4169 alloy bar and chamfer the edges. During billet making, ensure that the billet is in a suitable position in the mold. The protrusion in the mold forms a positioning platform. The bar does not need to be machined to form a positioning platform, which saves material and increases the deformation amount. The deformation amount is controlled at 30% to 42%, which reduces the deformation dead zone and refines the grains.

[0029] Step 2: Heat the bar stock to 975℃~995℃. During heating, spray the billet with heat-insulating coating. Place the bar stock in the die and slowly upset it using a 2500t high-speed forging machine (see...). Figure 2 ), to make the rough shape required for die forging;

[0030] Step 3: Apply lubricant to the rough blank in sections, and apply two types of coatings to the upper and lower end faces and the outer edge (see...). Figure 3 );

[0031] Step 4: Heat the billet to 980℃~1000℃. During heating, use insulating cotton for a soft wrapping. During die forging, flip the billet so that its positioning surface contacts the die for positioning (see...). Figure 4The process involves forging using a 100MN hydraulic press with a die preheating temperature of 250℃~350℃. The pressing speed is initially fast and then slows down, starting at 8~10mm / s and then adjusting to 3~5mm / s. The ratio of billet height between the initial and subsequent stages is 4:1, and the deformation is controlled at 30%~42%. By spraying different types of coatings in different areas and adjusting the pressing speed, the uniformity of the temperature field during forging is ensured, providing conditions for complete recrystallization and resulting in a uniform and refined microstructure.

[0032] Based on simulation results, the temperature rises at the center during the initial forging process, while the temperature field at the outer edge of the rough die is relatively lower. Metal flow at the outer edge tends to move upwards and downwards towards the mounting edges, resulting in smaller deformation at these locations compared to other areas. The lower temperature leads to incomplete recrystallization, coarse grains, and uneven microstructure at low magnification. To address this, two types of coatings are applied to the upper and lower surfaces and the outer edge. A coating with better insulation is applied to the outer edge to ensure overall temperature field uniformity, match the deformation amount, and refine the grains.

[0033] Step 5: After forging, the forging is subjected to heat treatment. The heat treatment regime is direct aging, the aging temperature is 720℃, the holding temperature is 480min, the furnace is cooled to 620℃ at a cooling rate of (50±10)℃ / h, the holding temperature is 480min, and then air-cooled to obtain the final forging.

[0034] Example 1

[0035] The present invention discloses a GH4169 alloy direct aging disc forging. The outer diameter of the disc is Φ360mm, the upper mounting edge diameter is Φ280mm, the lower mounting edge diameter is Φ290mm, the forging height is 110mm, and the forging weight is 62.7Kg. The forging uses a reasonably designed die for blanking, which avoids the need for a positioning table on the bar stock and subsequent die forging machine. The positioning table is formed during the die blanking process, which increases the deformation amount, reduces the deformation dead zone, and saves costs. The zoned spraying of coating and variable speed pressing ensure the temperature field during the forging process, so that the microstructure of the forging is uniform and the grain size and performance indicators meet the forging standard requirements.

[0036] The manufacturing process is detailed below:

[0037] 1. Cutting: Sawing machine, cutting size φ200×260mm;

[0038] 2. Billet machining: Bar stock with a chamfer radius of R20;

[0039] 3. Billet Formation: The bar stock is heated to 985℃. When heating cold stock, an insulating coating is applied. The bar stock is then placed in a die and upset using a 2500t high-speed forging mill. A diagram showing the bar stock placement is attached. Figure 2 After the bar stock is placed and positioned, a punch is placed to upset it into the rough shape required for die forging. The positioning table is formed, and the protrusion in the die increases the amount of deformation. The amount of deformation is controlled at 30% to 42%, reducing the deformation dead zone and refining the grains.

[0040] 4. Die forging: A 100MN hydraulic press is used for die forging. The die preheating temperature is 300℃, and the preheating time is ≥20h. The billet is heated to 990℃. Before heating, the billet is sprayed with lubricant in sections. Two types of coatings are sprayed on the upper and lower end faces and the outer edge (see...). Figure 3 The outer edge is coated with a paint that provides better insulation. During die forging, the billet is flipped so that the positioning surface of the billet contacts the die for positioning. (See attached...) Figure 4 Place the billet and initially press it at a speed of 8 mm / s. When the under-pressing reaches 30 mm, adjust the forging speed to 5 mm / s and control the deformation at 30%–42%. By spraying different types of heat-insulating coatings in different areas and adjusting the pressing speed, ensure the uniformity of the temperature field during forging, provide conditions for complete recrystallization, and make the microstructure uniform and refined.

[0041] 5. After forging, the forging is subjected to heat treatment. The heat treatment regime is direct aging. The aging temperature is 720℃, the holding temperature is 480min, the furnace is cooled to 620℃ at a cooling rate of (50±10)℃ / h, the holding temperature is 480min, and the final forging is obtained by air cooling.

[0042] The GH4169 alloy direct aging disc forgings obtained by this forging method were tested and found to have the following characteristics: 1 / 2R forging, uniform grain size (grade 10) at the center, and room temperature tensile strength: σ b =1552MPa, σ 0.2 =1385MPa, δ5=15%, ψ=29%, the microstructure and performance indicators of the forging meet the requirements of direct aging disc forgings.

Claims

1. A forging method for refining the grain size of GH4169 alloy direct aging disc forgings, characterized in that, include: Cut the GH4169 alloy bar and chamfer its edges; The blank is made using a mold. The blank is a disc blank that is larger at the top and smaller at the bottom and has a convex outer circle. The upper end of the disc blank is provided with a positioning groove and the lower end is provided with a deformation groove. The convex outer circle is divided into an outwardly inclined section, a cylindrical section, an inwardly inclined section and a positioning curved surface section from top to bottom. The mold cavity wall corresponding to the positioning curved surface section is used to fix the lower end of the bar stock. The upside-down billet is die-forged; the positioning groove is clamped in the lower forging die cavity to form the inner transition area of ​​the leg and the disc of the disc forging. Under the constraint of the forging die, the billet metal flows outward. The metal between the positioning groove and the outer inclined section fills the leg, the cylindrical section fills the center of the disc, the inner inclined section partially fills the center of the disc, partially fills the edge of the disc, and the deformation groove and the positioning curved surface section fill the edge of the disc. Before die forging, the blank is sprayed with heat-insulating coating in different sections. The outer inclined section, cylindrical section and inner inclined section of the outer circle of the blank, which are used to form the disc forging, have better heat-insulating properties than other areas of the blank. This better suppresses the temperature drop and ensures that the temperature of the outer circle of the blank is always ≥930℃ during the deformation process. The temperature of the center of the blank is only required to be ≥930℃ during the deformation process. This makes the temperature field of the outer edge of the disc forging always close to that of the core during the forging process. After die forging, the forging is subjected to heat treatment; the heat treatment regime is direct aging. The aging temperature is 720℃, held for 480 minutes, cooled in the furnace at a rate of 50±10℃ / h to 620℃, held for 480 minutes, and then air-cooled.

2. The method according to claim 1, characterized in that, Die forging the upside-down billet includes: The billet is heated to 980℃~1000℃. During heating, it is wrapped with heat-insulating cotton. During die forging, the billet is flipped so that the positioning groove of the billet contacts the lower forging mold cavity for positioning. The 100MN hydraulic press is used for die forging. The preheating temperature of the forging die is 250℃~350℃. The pressing speed is fast at first and then slows down. The deformation is controlled at 30%~42%.

3. The method according to claim 2, characterized in that, The initial speed is 8-10 mm / s, and then adjusted to 3-5 mm / s. The ratio of billet height between the initial and subsequent stages is 4:

1.

4. The method according to claim 1, characterized in that, The blanking process using a mold includes: The bar stock is heated to 975℃~995℃. Before heating, the billet is sprayed with heat-insulating coating. The bar stock is placed in the die and slowly upset using a 2500t high-speed forging machine to produce the blank required for die forging.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-4.

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