A high-efficiency end mill for cutting titanium alloys and its preparation method

Abstract

This invention relates to a milling cutter (IPC classification: B23P15 / 34), and more particularly to a high-efficiency milling cutter for cutting titanium alloys and its preparation method. The main raw materials include: cobalt and carbides. The carbides, by weight, comprise: 50-60 parts tungsten carbide, 5-10 parts vanadium carbide, 5-10 parts chromium carbide, 10-20 parts titanium carbide, and 2-3 parts tantalum carbide. The high-efficiency milling cutter for cutting titanium alloys prepared by this invention exhibits excellent transverse fracture strength, hardness, and toughness. Its low surface roughness improves the performance of machining titanium alloys, enhances vibration resistance, and increases the service life of the milling cutter.

Description

Technical Field

[0001] This invention relates to a milling cutter (IPC classification: B23P15 / 34), and more particularly to a high-efficiency milling cutter for cutting titanium alloys and its preparation method. Background Technology

[0002] Titanium alloys, as an emerging material, have been extensively developed and utilized in recent decades due to their excellent physical and chemical properties, such as high strength, strong corrosion resistance, and high heat resistance. They are widely used in the aerospace field and rocket components. However, the excellent properties of titanium alloys also bring great difficulties to their machining. During machining, the tool-chip contact area is small, the stress is high, and the temperature is high, resulting in severe tool adhesion wear and diffusion wear. Therefore, the selection of tool material is the primary issue in titanium alloy machining. In practice, the durability of the tool and the overall cutting effect are not good, and severe tool adhesion occurs, easily causing strong adhesive wear and seriously reducing the tool's service life.

[0003] Patent application CN201711059833.5 discloses a tungsten steel polished end mill. The end mill prepared by this patent has a diamond coating on the cutting edge, which improves the wear resistance. However, the diamond coating has high requirements for the substrate due to the need to consider the bonding ability with the substrate. In addition, the addition of a coating layer in this patent means that once the coating is damaged, it will also affect the use of the end mill and increase the cost.

[0004] Therefore, the high-efficiency milling cutter for cutting titanium alloys prepared by this invention has excellent transverse fracture strength, hardness and toughness, and its low surface roughness improves the performance of machining titanium alloys, enhances the shock resistance, and improves the service life of the milling cutter. Summary of the Invention

[0005] To address the aforementioned problems, a first aspect of the present invention provides a high-efficiency end mill for cutting titanium alloys, primarily comprising the following raw materials: cobalt and carbides. By mass percentage, the raw materials consist of 11-13% cobalt, with the balance being carbides.

[0006] As a preferred embodiment, the carbide is a mixture of tungsten carbide, vanadium carbide, chromium carbide, titanium carbide, niobium carbide, and tantalum carbide.

[0007] As a preferred embodiment, the carbide, by weight, comprises: 50-60 parts tungsten carbide, 5-10 parts vanadium carbide, 5-10 parts chromium carbide, 10-20 parts titanium carbide, and 2-3 parts tantalum carbide.

[0008] As a preferred embodiment, the weight ratio of chromium carbide, vanadium carbide, and tantalum carbide is (2-4):(2-4):1.

[0009] As a preferred embodiment, the average particle size of the cobalt is 0.9–1.3 μm.

[0010] As a preferred embodiment, the tungsten carbide has an average particle size of 0.7–1.0 μm.

[0011] As a preferred embodiment, the vanadium carbide has an average particle size of 1.0 to 2.0 μm.

[0012] As a preferred embodiment, the average particle size of the chromium carbide is 0.5–1.5 μm.

[0013] As a preferred embodiment, the titanium carbide has an average particle size of 1.5–2.5 μm.

[0014] As a preferred embodiment, the niobium carbide has an average particle size of 1.5–2.5 μm.

[0015] As a preferred embodiment, the tantalum carbide has an average particle size of 1.0 to 2.0 μm.

[0016] A second aspect of the present invention provides a method for preparing a high-efficiency milling cutter for cutting titanium alloys, the steps of which mainly include:

[0017] (1) Pretreatment: Cobalt and carbide are placed in a cemented carbide ball mill jar and ball milled to obtain composite powder.

[0018] (2) Sintering: The composite powder is pressed into a cylindrical blank, sintered, and then cooled in a furnace.

[0019] (3) Cutting: Cut the cylindrical blank obtained in step (2) to obtain a rough milling cutter.

[0020] (4) Quenching: Preheat the rough milling cutter, keep it at a certain temperature, and air cool it to room temperature.

[0021] (5) Tempering: Heat the rough milling cutter obtained in step (4) and temper it. Each tempering is cooled to room temperature with air.

[0022] (6) Post-processing: Sandblasting and polishing are performed on the rough milling cutter after tempering.

[0023] As a preferred embodiment, the ball milling time is 18 to 20 hours, the ball milling temperature is -10 to -3°C, and the ball milling speed is 300 to 400 r / min.

[0024] As a preferred option, the raw materials pretreated in step (1) also include anhydrous alcohol and liquid paraffin.

[0025] As a preferred embodiment, the anhydrous ethanol accounts for 30% of the total mass of the carbide.

[0026] As a preferred embodiment, the liquid paraffin comprises 3% of the total mass of the carbides.

[0027] As a preferred embodiment, the sintering process parameters in step (2) are as follows: Heat to 400–500°C at a heating rate of 10–20°C / min, purge with hydrogen, and hold for 20–40 minutes. Continue heating at a rate of 10–20°C / min to 1300–1400°C, purge with argon, and sinter for 20–40 minutes.

[0028] As a preferred embodiment, the preheating temperature in step (4) is 800-900℃; the heat preservation temperature is 1000-1200℃.

[0029] As a preferred option, the tempering process in step (5) is performed 3 to 5 times.

[0030] As a preferred embodiment, the surface roughness parameter Ra of the milling cutter after polishing in step (6) is 0.1a to 0.2a.

[0031] In this invention, the applicant discovered that when the mass percentage of cobalt is 11-13% and the average particle size of cobalt is 0.9-1.3 μm, its fracture resistance, hardness, and wear resistance can be balanced. When the mass percentage of cobalt is greater than 13% and the average particle size of cobalt is greater than 1.3 μm, the impact resistance and fracture toughness of the cemented carbide tend to increase, which also reduces its hardness and wear resistance. Simultaneously, the applicant also unexpectedly discovered that when the average particle size of tungsten carbide is 0.7-1.0 μm, tungsten carbide agglomeration is effectively avoided, thereby improving the mechanical properties of the carbide. This may be because tungsten carbide agglomeration is detrimental to the uniform distribution of WC grains in the matrix.

[0032] Beneficial effects:

[0033] 1. By limiting the mass percentage of cobalt to 11-13% and the average particle size of cobalt to 0.9-1.3 μm, the present invention can improve the compactness of the end mill, thus improving the fracture resistance, hardness and wear resistance of the end mill.

[0034] 2. By limiting the average particle size of tungsten carbide to 0.7-1.0 μm, this invention effectively avoids the agglomeration of tungsten carbide in cobalt and other carbide systems, thereby improving the wear resistance and toughness of carbides.

[0035] 3. By limiting the weight ratio of chromium carbide, vanadium carbide, and tantalum carbide to (2-4): (2-4):1, this invention can effectively suppress the abnormal growth of tungsten carbide grains, thereby improving compressive strength and toughness. Simultaneously, it reduces the wetting angle of cobalt on the solid solution during sintering, thus improving sintering performance. Furthermore, the addition of tantalum carbide can enhance the fatigue resistance of the milling cutter, thereby improving milling performance.

[0036] 4. By limiting the heating rate during sintering to 10-20℃ / min, the sintering temperature to 1300-1400℃, and the sintering time to 20-40min, this invention effectively avoids the phenomenon of tungsten carbide grain growth, reduces the tensile stress on the cobalt phase, and thus improves the bending strength and toughness of the milling cutter.

[0037] 5. This invention utilizes ultrafine-grained tungsten carbide and the synergistic effect of other tungsten carbide and cobalt to prepare a high-efficiency end mill for cutting titanium alloys. The end mill exhibits a transverse fracture strength of up to 4047.4 N / mm². 2 Its hardness can reach 92.7 HRa. Detailed Implementation

[0038] Example

[0039] Example 1

[0040] Embodiment 1 of the present invention provides a high-efficiency end mill for cutting titanium alloys, comprising the following raw materials: cobalt and carbides. The mass percentage content of the raw materials is: 12% cobalt, with the balance being carbides.

[0041] The carbides, by weight, consist of the following raw materials: 55 parts tungsten carbide, 7 parts vanadium carbide, 8 parts chromium carbide, 15 parts titanium carbide, and 2.5 parts tantalum carbide.

[0042] The average particle size of the cobalt is 1.2 μm. The average particle size of the tungsten carbide is 0.8 μm. The average particle size of the vanadium carbide is 1.5 μm. The average particle size of the chromium carbide is 1.0 μm. The average particle size of the titanium carbide is 2.0 μm. The average particle size of the niobium carbide is 2.0 μm. The average particle size of the tantalum carbide is 1.5 μm.

[0043] The cobalt was purchased from Qinghe County Zhongzhou Alloy Materials Co., Ltd. The tungsten carbide, vanadium carbide, chromium carbide, titanium carbide, niobium carbide, and tantalum carbide were all purchased from Shanghai Chaowei Nanotechnology Co., Ltd.

[0044] The second aspect of this embodiment provides a method for preparing a high-efficiency milling cutter for cutting titanium alloys, the steps of which include:

[0045] (1) Pretreatment: Cobalt and carbide are placed in a cemented carbide ball mill jar and ball milled to obtain composite powder.

[0046] (2) Sintering: The composite powder is pressed into a cylindrical blank, sintered, and then cooled in a furnace.

[0047] (3) Cutting: Cut the cylindrical blank obtained in step (2) to obtain a rough milling cutter.

[0048] (4) Quenching: Preheat the rough milling cutter, keep it at a certain temperature, and air cool it to room temperature.

[0049] (5) Tempering: Heat the rough milling cutter obtained in step (4) and temper it. Each tempering is cooled to room temperature with air.

[0050] (6) Post-processing: Sandblasting and polishing are performed on the rough milling cutter after tempering.

[0051] The ball milling time was 19 hours, the ball milling temperature was -5℃, and the ball milling speed was 350 r / min.

[0052] The pretreated raw materials in step (1) also include anhydrous ethanol and liquid paraffin. The anhydrous ethanol accounts for 30% of the total mass of the carbides. The liquid paraffin accounts for 3% of the total mass of the carbides.

[0053] The sintering process parameters in step (2) are as follows: heat to 450°C at a heating rate of 15°C / min, purge with hydrogen, and hold for 30 minutes. Continue heating at a heating rate of 15°C / min to 1350°C, purge with argon, and sinter for 30 minutes.

[0054] The preheating temperature in step (4) is 850℃; the heat preservation temperature is 1150℃.

[0055] The tempering process in step (5) is performed four times.

[0056] The surface roughness parameter Ra of the milling cutter after polishing in step (6) is 0.1a.

[0057] Example 2

[0058] Embodiment 2 of the present invention provides a high-efficiency end mill for cutting titanium alloys, comprising the following raw materials: cobalt and carbides. The mass percentage content of the raw materials is: 12% cobalt, with the balance being carbides.

[0059] The carbide, by weight, comprises the following raw materials: 60 parts tungsten carbide, 10 parts vanadium carbide, 10 parts chromium carbide, 20 parts titanium carbide, and 3 parts tantalum carbide.

[0060] The average particle size of the cobalt is 1.3 μm. The average particle size of the tungsten carbide is 1.0 μm. The average particle size of the vanadium carbide is 1.5 μm. The average particle size of the chromium carbide is 1.0 μm. The average particle size of the titanium carbide is 2.0 μm. The average particle size of the niobium carbide is 2.0 μm. The average particle size of the tantalum carbide is 1.5 μm.

[0061] The cobalt was purchased from Qinghe County Zhongzhou Alloy Materials Co., Ltd. The tungsten carbide, vanadium carbide, chromium carbide, titanium carbide, niobium carbide, and tantalum carbide were all purchased from Shanghai Chaowei Nanotechnology Co., Ltd.

[0062] The second aspect of this embodiment provides a method for preparing a high-efficiency milling cutter for cutting titanium alloys, the steps of which include:

[0063] (1) Pretreatment: Cobalt and carbide are placed in a cemented carbide ball mill jar and ball milled to obtain composite powder.

[0064] (2) Sintering: The composite powder is pressed into a cylindrical blank, sintered, and then cooled in a furnace.

[0065] (3) Cutting: Cut the cylindrical blank obtained in step (2) to obtain a rough milling cutter.

[0066] (4) Quenching: Preheat the rough milling cutter, keep it at a certain temperature, and air cool it to room temperature.

[0067] (5) Tempering: Heat the rough milling cutter obtained in step (4) and temper it. Each tempering is cooled to room temperature with air.

[0068] (6) Post-processing: Sandblasting and polishing are performed on the rough milling cutter after tempering.

[0069] The ball milling time was 19 hours, the ball milling temperature was -5℃, and the ball milling speed was 350 r / min.

[0070] The pretreated raw materials in step (1) also include anhydrous ethanol and liquid paraffin. The anhydrous ethanol accounts for 30% of the total mass of the carbides. The liquid paraffin accounts for 3% of the total mass of the carbides.

[0071] The sintering process parameters in step (2) are as follows: heat to 450°C at a heating rate of 15°C / min, purge with hydrogen, and hold for 30 minutes. Continue heating at a heating rate of 15°C / min to 1350°C, purge with argon, and sinter for 30 minutes.

[0072] The preheating temperature in step (4) is 850℃; the heat preservation temperature is 1150℃.

[0073] The tempering process in step (5) is performed four times.

[0074] The surface roughness parameter Ra of the milling cutter after polishing in step (6) is 0.1a.

[0075] Example 3

[0076] Embodiment 3 of the present invention provides a high-efficiency end mill for cutting titanium alloys, comprising the following raw materials: cobalt and carbides. The mass percentage content of the raw materials is: 12% cobalt, with the balance being carbides.

[0077] The carbide, by weight, comprises the following raw materials: 50 parts tungsten carbide, 5 parts vanadium carbide, 5 parts chromium carbide, 10 parts titanium carbide, and 2 parts tantalum carbide.

[0078] The average particle size of the cobalt is 1.3 μm. The average particle size of the tungsten carbide is 1.0 μm. The average particle size of the vanadium carbide is 1.5 μm. The average particle size of the chromium carbide is 1.0 μm. The average particle size of the titanium carbide is 2.0 μm. The average particle size of the niobium carbide is 2.0 μm. The average particle size of the tantalum carbide is 1.5 μm.

[0079] The cobalt was purchased from Qinghe County Zhongzhou Alloy Materials Co., Ltd. The tungsten carbide, vanadium carbide, chromium carbide, titanium carbide, niobium carbide, and tantalum carbide were all purchased from Shanghai Chaowei Nanotechnology Co., Ltd.

[0080] The second aspect of this embodiment provides a method for preparing a high-efficiency milling cutter for cutting titanium alloys, the steps of which include:

[0081] (1) Pretreatment: Cobalt and carbide are placed in a cemented carbide ball mill jar and ball milled to obtain composite powder.

[0082] (2) Sintering: The composite powder is pressed into a cylindrical blank, sintered, and then cooled in a furnace.

[0083] (3) Cutting: Cut the cylindrical blank obtained in step (2) to obtain a rough milling cutter.

[0084] (4) Quenching: Preheat the rough milling cutter, keep it at a certain temperature, and air cool it to room temperature.

[0085] (5) Tempering: Heat the rough milling cutter obtained in step (4) and temper it. Each tempering is cooled to room temperature with air.

[0086] (6) Post-processing: Sandblasting and polishing are performed on the rough milling cutter after tempering.

[0087] The ball milling time was 19 hours, the ball milling temperature was -5℃, and the ball milling speed was 350 r / min.

[0088] The pretreated raw materials in step (1) also include anhydrous ethanol and liquid paraffin. The anhydrous ethanol accounts for 30% of the total mass of the carbides. The liquid paraffin accounts for 3% of the total mass of the carbides.

[0089] The sintering process parameters in step (2) are as follows: heat to 450°C at a heating rate of 15°C / min, purge with hydrogen, and hold for 30 minutes. Continue heating at a heating rate of 15°C / min to 1350°C, purge with argon, and sinter for 30 minutes.

[0090] The preheating temperature in step (4) is 850℃; the heat preservation temperature is 1150℃.

[0091] The tempering process in step (5) is performed four times.

[0092] The surface roughness parameter Ra of the milling cutter after polishing in step (6) is 0.1a.

[0093] Comparative Example 1

[0094] The specific implementation method of Comparative Example 1 is the same as that of Example 1; the difference is that the mass percentage of cobalt in Comparative Example 1 is 16%.

[0095] Comparative Example 2

[0096] The specific implementation method of Comparative Example 2 is the same as that of Example 1; the difference is that the average particle size of tungsten carbide in Comparative Example 2 is 0.5 μm.

[0097] Performance testing:

[0098] (1) Rockwell hardness: The test was conducted using a 69-1 type Browell optical hardness tester in accordance with GB3849-1983.

[0099] (2) Transverse fracture strength: Tested in accordance with GB / T3851-1983.

[0100] Performance test results:

[0101] Table 1 shows the performance test results of the high-efficiency end mills for cutting titanium alloys prepared in Examples 1-3 and Comparative Examples 1-2.

[0102] Table 1

[0103]

[0104]

Claims

1. A high-efficiency end mill for cutting titanium alloys, characterized in that, By mass percentage, raw materials: 11-13% cobalt, with the balance being carbides; The carbide, by weight, comprises: 50-60 parts of tungsten carbide, 5-10 parts of vanadium carbide, 5-10 parts of chromium carbide, 10-20 parts of titanium carbide, and 2-3 parts of tantalum carbide. The weight ratio of chromium carbide, vanadium carbide, and tantalum carbide is (2~4):(2~4):1; The average particle size of the tungsten carbide is 0.8~1.0 μm.

2. The high-efficiency milling cutter for cutting titanium alloys according to claim 1, characterized in that, The average particle size of the cobalt is 0.9~1.3μm.

3. The method for preparing a high-efficiency end mill for cutting titanium alloys according to any one of claims 1-2, characterized in that, The steps include: (1) Pretreatment: Cobalt and carbide are placed in a cemented carbide ball mill jar and ball milled to obtain composite powder; (2) Sintering: The composite powder is pressed into cylindrical blanks, sintered, and then cooled in a furnace; (3) Cutting: Cut the cylindrical blank obtained in step (2) to obtain a rough milling cutter; (4) Quenching: Preheat the rough milling cutter, keep it at a certain temperature, and air cool it to room temperature; (5) Tempering: Heat the rough milling cutter obtained in step (4) and temper it. Each tempering is cooled to room temperature with air. (6) Post-processing: Sandblasting and polishing are performed on the rough milling cutter after tempering.

4. The method for preparing a high-efficiency end mill for cutting titanium alloys according to claim 3, characterized in that, The ball milling time is 18~20h, the ball milling temperature is -10~-3℃, and the ball milling speed is 300~400r / min.

5. The method for preparing a high-efficiency end mill for cutting titanium alloys according to claim 3, characterized in that, The sintering process parameters in step (2) are as follows: heat up to 400-500℃ at a heating rate of 10-20℃ / min, purge with hydrogen, and hold for 20-40 minutes; continue heating up to 1300-1400℃ at a heating rate of 10-20℃ / min, purge with argon, and sinter for 20-40 minutes.

6. The method for preparing a high-efficiency end mill for cutting titanium alloys according to claim 3, characterized in that, The preheating temperature in step (4) is 800~900℃; the heat preservation temperature is 1000~1200℃.

7. The method for preparing a high-efficiency end mill for cutting titanium alloys according to claim 3, characterized in that, The tempering process in step (5) is repeated 3 to 5 times.

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