A forming method for influencing the internal microstructure of TC17 forged bladed disks

Abstract

This invention belongs to the field of forging hot working and relates to a method for influencing the internal microstructure of a TC17 forged bladed disk during forming. The method includes: Step 1, determining the required microstructure and properties of the forging; Step 2, when the required microstructure is a basket web structure and the fracture toughness is greater than or equal to 60 MPa·M1 / 2, forging the forging using a β-type forging process, and then proceeding to Step 4; Step 3, when the required microstructure is an equiaxed α+striped α+β transformation tri-state microstructure and the fracture toughness is less than or equal to 40 MPa·M1 / 2, forging the forging using a near-β-type forging process, and then proceeding to Step 4; Step 4, performing forming heat treatment on the forging.

Description

Technical Field

[0001] This invention belongs to the field of forging hot working and relates to a forming method that affects the internal structure of TC17 forging bladed disks. Background Technology

[0002] TC17 titanium alloy is a near-β-type titanium alloy developed by General Electric (GE) in the 1970s for advanced GE engines. It possesses high strength, toughness, and hardenability, earning it the title of a "high-strength, high-toughness, high-performance titanium alloy." TC17 titanium alloy exhibits characteristics of both (α+β)-type and β-type titanium alloys. Its composition is Ti-5Ai-4Mo-2Sn-2Zr, with a total alloy element content of 17%. Currently, my country has selected TC17 alloy forged bladed disks for its XX-type aero-engines.

[0003] TC17 alloy is an α+β type two-phase titanium alloy rich in β-stabilizing elements, with a nominal chemical composition of Ti-5Ai-4Mo-2Sn-2Zr. This alloy possesses a series of characteristics including high strength, good toughness, and high hardenability, meeting the requirements of damage-tolerant design, high structural efficiency, high reliability, and low manufacturing costs. The main semi-finished products of this alloy are bars and forgings, primarily used in the manufacture of engine fans, compressor discs, and large-section forgings. The balance of strength, plasticity, and toughness can be adjusted through heat treatment. my country began developing TC17 titanium alloy, which, due to its superior performance, has gradually entered the aerospace manufacturing field and has been practically applied in high-thrust engines using forgings such as compressor discs.

[0004] Because TC17 alloy forgings have different requirements for internal structure, the forging process has a significant impact on the microstructure and properties of TC17 alloy forgings. In particular, different forging schemes have a significant impact on the strength, plasticity, fracture toughness and high cycle fatigue of forgings. Different production process schemes for forgings mean that changes in each parameter directly affect the internal structure of the forgings, making the products unable to meet the final requirements, resulting in product scrap and a great waste of resources.

[0005] TC17 titanium alloy is generally used in aerospace for disc-shaped forgings. Its application requires high mechanical properties of the forgings. However, during the forging process, the temperature and the number of heating cycles in the forging process have a significant impact on its values. Summary of the Invention

[0006] The purpose of this invention is to adopt different forging schemes to meet the requirements of strength, plasticity, fracture toughness and high cycle fatigue of forgings according to different requirements of the final internal structure of forgings, to set different production process schemes for forgings, to improve the internal structure of forgings by controlling the forging method, and to use the forging method to meet the design requirements of forgings by a reasonable forging forming scheme, so as to obtain the internal structure required for qualified forgings.

[0007] The technical solution of this invention is:

[0008] A forming method for influencing the internal microstructure of a TC17 forged bladed disk includes:

[0009] Step 1: Determine the final microstructure and property requirements for the forging;

[0010] Step 2: When the final microstructure of the forging is a basket web structure, and the fracture toughness is greater than or equal to 60 MPa·m¹ / When ², the forging is forged using the β-type forging process, and step 4 is executed;

[0011] Step 3: When the final microstructure of the forging is a tri-state microstructure of equiaxed α+ and stripe α+β transformation, and the fracture toughness is less than or equal to 40 MPa·m¹ / When ², the forging is forged using a near-β forging process, and step 4 is executed;

[0012] Step 4: Perform forming heat treatment on the forging.

[0013] Forgings produced using the β-type forging process include:

[0014] The billet is subjected to β-type forging within a temperature range of tβ+(15-20)℃;

[0015] The forged billet is then formed and forged.

[0016] The parameters for β-type forging and reforging include:

[0017] The holding time for forgings should be set according to the requirement of 0.8 min / mm to 1.0 min / mm;

[0018] The forging ratio of upsetting to drawing in each forging pass is 1.0 to 2.5; the deformation amount in each forging pass is 45% to 55%; and the cooling method is air cooling.

[0019] Forgings produced using a near-β forging process include:

[0020] The billet is subjected to near-β forging modification within a temperature range of tβ-(20-35)℃;

[0021] The forged billet is then formed and forged.

[0022] The parameters for near-β forging modification include:

[0023] The holding time for forgings should be set according to the requirement of 0.8 min / mm to 1.0 min / mm;

[0024] The forging ratio of upsetting to drawing is 1.0~2.5; the deformation is 30%~40%; and the cooling method is water cooling.

[0025] The parameters for forming and forging include:

[0026] The preformed parts are heated to 2tβ-30℃, with a heat preservation coefficient calculated at 0.8min / mm. While the preformed parts are being heated, the tooling mold is preheated to 250℃~350℃. After the preformed parts are held at the set temperature for the set time, they are immediately taken out of the furnace for forging, with a transfer time of no more than 20 seconds.

[0027] The forming heat treatment regime for forgings obtained by β-type forging is 800℃×4hWQ+630℃8hAC.

[0028] The forming heat treatment regime for forgings obtained by near-β forging is 850℃×3hAC+800℃×4h WQ+630℃8hAC.

[0029] The beneficial effects of this invention are:

[0030] Because TC17 alloy forgings have different requirements for internal structure, the forging process has a significant impact on the microstructure and properties of TC17 alloy forgings. In particular, different forging schemes have a significant impact on the strength, plasticity, fracture toughness, and high-cycle fatigue of the forgings. Different production process schemes for forgings mean that changes in each parameter directly affect the internal structure of the forgings. Based on the characteristics of the material and the required internal structure of the forgings, the forging method of the TC17 forging production process scheme is set to obtain a qualified and stable internal structure, improve the pass rate of the internal structure of the forgings in physical and chemical tests, reduce scrap loss, and greatly improve the pass rate of forgings. Detailed Implementation

[0031] The existing forging method is as follows: blanking - forming (phase change electric heating) - heat treatment - physical and chemical treatment. Forging of ordinary parts is completed within 1-3 heat treatments, and physical and chemical tests are performed on the forgings.

[0032] Conventional processing often fails to meet the required low-magnification and high-magnification grain size requirements for the internal microstructure of forgings. Therefore, selecting a suitable forging method based on the material properties of TC17 is crucial to its microstructure and performance. In particular, adding a billet preparation step to 3T free forgings is essential to ensure that the final forging deformation amount and rate meet the requirements for the final physical and chemical testing results. Otherwise, a large number of forgings will fail to meet physical and chemical standards, leading to scrapping.

[0033] This invention provides different TC17 forging processes based on the final required internal microstructure of the forging. TC17 production includes β-forging and near-β-forging, as detailed in Table 1.

[0034] Table 1

[0035]

[0036] By controlling the forging method, the internal structure of the forging is improved. The forging method is used to meet the design requirements of the forging and a reasonable forging forming scheme is obtained, resulting in a qualified and stable internal structure as shown in Table 2.

[0037] Table 2

[0038]

[0039] The method includes the following steps:

[0040] Step 1: Determine the forging method from Tables 1 and 2 based on the required microstructure and properties of the final forging.

[0041] Step 2: Classify forging methods; A and B type forging; Type A forging is β-type forging, and Type B forging is near-β-type forging.

[0042] Step 3: Forging the billet.

[0043] Type A forging uses β-type forging as the forging material. The forging temperature is tβ + (15-20)℃. The holding time is set according to the requirement of 0.8min / mm~1.0min / mm. After the set time, the forging is immediately removed from the furnace and forged on a 3T free forging hammer until it is formed. At the same time, the intermediate and final forging temperatures are controlled. The forging ratio of upsetting to drawing is 1.0~2.5. The deformation is 45%~55%. The cooling method is air cooling.

[0044] Type B forging is near-β type forging. The forging of the billet is carried out at a temperature of tβ-(20-35)℃. The holding time of the forging is set according to the requirement of 0.8min / mm~1.0 min / mm. After the set time, the forging is immediately taken out of the furnace and forged on a 3T free forging hammer until it is formed. At the same time, the intermediate and final forging temperatures are controlled. The forging ratio of upsetting and drawing is 1.0~2.5. The deformation is 30%~40%. The cooling method is water cooling.

[0045] Step 4: Forming and forging.

[0046] Forging parts of types A and B are heated to 2tβ-30℃, with a holding coefficient calculated at 0.8min / mm. While heating the preformed parts, the tooling mold is preheated to 250℃~350℃. After the formed parts are held at the set temperature, they are immediately taken out of the furnace for forging, and the transfer time is no more than or equal to 20 seconds.

[0047] Step 5: Heat treatment of the molded part

[0048] A: The heat treatment regime for β-type forging is 800℃×4hWQ+630℃8hAC.

[0049] B: The heat treatment regime for near-β forging is 850℃×3hAC+800℃×4h WQ+630℃8hAC.

[0050] Step 6: Conduct 100% mechanical property and internal structure inspections.

[0051] Example

[0052] The final internal organizational requirements are for the following netball organization example:

[0053] (1) Design process flow: Requirements for internal structure of forging → Set production process plan → Sawing to process requirement length → Determine forging plan → Modified forging → Forming forging → Heat treatment → Physical and chemical treatment.

[0054] (2) For production furnace number 20180538B; the final internal structure requirement is a basket structure; the forging method is determined to be β-type forging modified forging + forming;

[0055] (3) Blanking specifications: Φ230×125 (forging), weight: 23.4 kg

[0056] (4) Forging process

[0057] Step 1: Forging at Tβ+25℃ for 100 min (2 upsetting, 3 drawing, 1 tempering) to complete.

[0058] Φ230×125 Axial elongation ~ □145×250±5 Upsetting □140×260

[0059] II. Forging Step: Tβ + 20℃ × 115 min 2 upsetting steps, 1 drawing step to complete.

[0060] □140×260 Upsetting ~ □185×150±5 Chamfering and drawing □140×260±5

[0061] III. Forging Process: Tβ+20℃×115 min 2 upsetting 2 drawing 2 tempering completed

[0062] Upsetting ~ 175×170±5 Reversing and elongation ~ 140×260±5

[0063] IV. Forging Step: Tβ-20℃×115 min 3 upsetting, 3 drawing, 3 heat treatments to complete.

[0064] □140×260 Upsetting ~ □175×170±5 Chamfering and drawing ~ □140×260±5

[0065] Step V (Forging Modification): Repeat step IV once, performing one upsetting and one drawing per heat, completing in 3 heats.

[0066] Step VI Molding: Tβ-30℃×115 min (1 heat complete)

[0067] □140×260 Forged and drawn to 110±2×140±3×330+10 -5

[0068] (5) Machining inspection of both sides with low magnification and flaw detection, and dissection of physical and chemical parts to inspect the core with low magnification. All forging equipment is carried out on a 3T free forging hammer. The forging technology requirements are: 1) Transfer time ≤ 30 seconds; 2) Final forging temperature ≥ 780℃; 3) Control the hammering frequency and weight during the forging process to prevent coarse grains in the core of the forging.

[0069] After manufacturing a batch according to the above modified forging scheme, the following problems were found by inspecting the low magnification of the end face of the forging and the core of the dissected part:

[0070] (6) After the forging was subjected to final heat treatment, a sample was taken for physical and chemical analysis. The results showed that both the low-magnification microstructure and the high-magnification grain size were qualified.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A forming method for influencing the internal microstructure of a TC17 forged bladed disk, characterized in that, include: Step 1: Determine the final microstructure and property requirements for the forging; Step 2: When the final microstructure of the forging is a basket web structure, and the fracture toughness is greater than or equal to 60 MPa·m¹ / When ², the forging is forged using the β-type forging process, and step 4 is executed; Step 3: When the final microstructure of the forging is a tri-state microstructure of equiaxed α+ and stripe α+β transformation, and the fracture toughness is less than or equal to 40 MPa·m¹ / When ², the forging is forged using a near-β forging process, and step 4 is executed; Step 4: Perform forming heat treatment on the forging; Among them, the forging process using β-type forging includes: performing β-type forging modification on the billet in the temperature range of tβ+(15-20)℃; and performing forming forging on the modified billet. Forging is performed using a near-β forging process, including: near-β forging modification of the billet within a temperature range of tβ-(20-35)℃; and forming forging of the modified billet. The parameters for the near-β forging modification include: holding time of 0.8 min / mm to 1.0 min / mm; forging ratio of upsetting to drawing of 1.0 to 2.5; deformation of 30% to 40%; and water cooling. The parameters for forming and forging include: the billet is heated to tβ-30℃, the holding coefficient is calculated at 0.8min / mm, and the tooling mold is preheated to 250℃~350℃ while heating; after holding for the set time, it is immediately taken out of the furnace for forging, and the transfer time is no more than or equal to 20 seconds. The forming heat treatment regime for forgings obtained by near-β forging is 850℃×3hAC+800℃×4h WQ+630℃8hAC.

2. The method according to claim 1, characterized in that, The parameters for β-type forging and reforging include: The holding time for forgings should be set according to the requirement of 0.8 min / mm to 1.0 min / mm. The forging ratio of upsetting to drawing in each forging pass is 1.0 to 2.5; the deformation amount in each forging pass is 45% to 55%; and the cooling method is air cooling.

3. The method according to claim 1, characterized in that, The forming heat treatment regime for forgings obtained by β-type forging is 800℃×4hWQ+630℃8hAC.

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