A cemented carbide material for heavy-duty cutting tools and a preparation method thereof

Abstract

The present invention relates to the technical field of alloy materials, and discloses a cemented carbide material for heavy-duty cutting tools and a preparation method thereof. The alloy material comprises the following raw materials by mass: 69-81.8 parts of WC, 8-12 parts of Co, 4-8 parts of TaC, 6-10 parts of TiC, and 0.2-1 parts of TiN; WC adopts mixed crystal. In the technical solution, WC adopts mixed crystal, and the difference of WC grains is utilized to increase the resistance of intercrystalline fracture, improve the fatigue strength of the matrix material, and through the optimization of the process and raw materials, the grains are not easily oxidized, and the prepared alloy material has high density.

Description

Technical Field

[0001] The invention relates to the technical field of alloy materials, and in particular to a cemented carbide material for heavy-duty cutting tools and a preparation method thereof. Background Art

[0002] In order to improve the wear resistance of heavy-duty cutting tools, it is usually necessary to pre-deposit one or more layers of wear-resistant coating on the surface of traditional cemented carbide substrates using chemical vapor deposition (CVD) technology. Since the deposition temperature of general CVD technology may be as high as 800-1000°C, and there is a difference in thermal expansion coefficient between the coating and the substrate, it will inevitably cause large thermal stress at the interface between the coating and the substrate during the cooling process; in addition, CVD coatings usually have aluminum oxide (a ceramic material), which is brittle and will bring the risk of cracks, making the coating have a greater tendency to crack. Therefore, during the use of the tool, cracks can easily accelerate and expand into the substrate, causing tool failure.

[0003] In view of the above problems, the prior art considers preparing a cemented carbide substrate with a surface layer that does not contain a brittle and hard cubic phase (β phase) and has high toughness, which is usually called a β-layered (Cemented Carbide free layer, CCFL) gradient cemented carbide. When this type of gradient cemented carbide is used as the substrate of the coated cemented carbide, the high-toughness surface layer can absorb the energy of crack propagation and slow down the tendency of the coating crack to propagate into the substrate, thereby ensuring the excellent performance of the coated tool. However, during the current research and development process, it was found that the preparation process of the existing β-layered gradient cemented carbide was prepared by adding ultrafine Ti (C, N) powder in a one-step sintering method, but this ultrafine grain TiCN is easily oxidized and difficult to preserve, and the density of the alloy is not ideal. Summary of the invention

[0004] The present invention aims to provide a cemented carbide material for heavy-duty cutting tools and a preparation method thereof, so as to solve the problems in the prior art of easy oxidation of grains and unsatisfactory alloy density when preparing de-β-layer gradient cemented carbide.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a cemented carbide material for heavy-duty cutting tools, comprising the following raw materials in parts by weight: 69-81.8 parts of WC, 8-12 parts of Co, 4-8 parts of TaC, 6-10 parts of TiC, and 0.2-1 part of TiN; WC is mixed crystal.

[0006] On the other hand, the present technical solution provides a method for preparing a cemented carbide material for a heavy-duty cutting tool, comprising the following steps:

[0007] Step 1: mixing, adding a molding agent and a wet grinding medium to the raw materials, and wet grinding to obtain a mixed material powder;

[0008] Step 2, pressing and forming to obtain a compact;

[0009] Step 3: Sintering: Under the protection of high-pressure argon, the alloy material is sintered by step-by-step heating.

[0010] Preferably, as an improvement, the mixed crystal mass ratio is (1-3 μm):(4-6 μm)=(12-35):(65-88).

[0011] In the technical solution, by mixing WC of different Fisher grain sizes in a certain proportion, the improvement of the wear resistance of the matrix by fine grains and the improvement of the toughness of the matrix by coarse grains can be combined, thereby ensuring the material performance.

[0012] Preferably, as an improvement, in step 1, the molding agent is paraffin, and the amount of paraffin added is 2-4%.

[0013] Preferably, as an improvement, in step 1, the wet grinding medium is hexane.

[0014] Preferably, as an improvement, in step 2, the molding pressure is greater than 0.8 t / cm 2 .

[0015] Preferably, as an improvement, in step three, the specific operation of staged heating is: first stage heating: heating from room temperature to 600°C; second stage heating: continuing to heat to 900-1250°C; third stage heating: heating to 1420-1460°C.

[0016] In this technical solution, the exploration of sintering conditions is a major technical difficulty. Through the synergistic effect of sintering condition optimization and component optimization, the prepared material has a gradient structural alloy with a β-phase layer removed. In the sintering stage, the first stage is mainly to remove the forming agent in the product. Too fast a heating rate will cause the product to burst or the forming agent will not be removed cleanly, causing product defects; the second stage is the key stage of the entire sintering. If it cannot be guaranteed, the required gradient alloy cannot be formed; the third stage is the final firing stage, which is the stage for the formation of the mechanical properties of the material. The final firing temperature needs to be determined according to the performance of the material.

[0017] Preferably, as an improvement, the heating rate in the first stage is less than 2°C / min; and the heating rate in the second stage is greater than or equal to 6°C / min.

[0018] Preferably, as an improvement, in step three, after the third stage of heating is maintained for 30 minutes, argon is filled in and the pressure is maintained for 0.5-1 hour to sinter the product.

[0019] Preferably, as an improvement, the pressure of argon gas is 3-5 MPa.

[0020] In this technical solution, high pressure filling is used in this stage, which can further eliminate the pores inside the matrix and improve the impact resistance of the matrix material.

[0021] The principles and advantages of this solution are: In this technical solution, based on the research and development background of our company's projects, when developing materials for heavy-duty (loaded) cutting tools, based on the particularity of its use conditions: heavy-duty cutting processing has a large back-cutting amount, low cutting speed, and slow feed speed, which can easily cause impact damage or bonding damage to the processing tool. The impact resistance of the material is enhanced and the material components are optimized. The addition of TaC and TiC can effectively improve the red hardness of the matrix. In addition, this technical solution creatively uses mixed crystal WC, which can combine the improvement of the wear resistance of the matrix by fine grains and the improvement of the toughness of the matrix by coarse grains. When optimizing the raw material formula, this technical solution also coordinates the directional optimization of the sintering process. The matrix is ​​prepared by these elements and the sintering process. The material has a gradient structure alloy with a β-phase layer. The surface of the material with this structure has better toughness than the inside of the matrix, and can more effectively prevent the coating cracks from spreading to the inside of the matrix and causing the matrix to fail. In this scheme, in addition to the matrix components, this structure is mainly formed by the corresponding "sintering process at different stages", which ultimately forms the material properties and finally forms a stable gradient (de-β phase layer). After testing, the gradient thickness layer of this process can be stabilized at 20-30μm.

[0022] 1. To avoid sintering oxidation, argon gas is usually required during sintering. This method can adopt the conventional sintering path.

[0023] 2. In this technical solution, high-pressure argon gas is filled at 1420℃-1460℃, which is more conducive to the densification of the product.

[0024] 3. In this technical solution, WC adopts mixed crystals, and the difference of WC grains is used to increase the resistance to intergranular fracture and improve the fatigue strength of the matrix material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a metallographic picture of the cemented carbide material according to Example 1 of the present invention.

[0026] Figure 2 This is a metallographic picture of the cemented carbide material according to Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The following is further described in detail through specific implementations, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following implementations are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained from commercial channels.

[0028] Program Overview:

[0029] A cemented carbide material for heavy-duty cutting tools comprises, by mass percentage, 69-81.8% WC, 8-12% Co, 4-8% TaC, 6-10% TiC and 0.2-1% TiN; wherein the WC is mixed crystal, and the mixed crystal mass ratio is (1-3 μm): (4-6 μm) = (12-35): (65-88).

[0030] A method for preparing a cemented carbide material for a heavy-duty cutting tool comprises the following steps:

[0031] Step 1: Mix the raw materials evenly according to the proportion, add the molding agent and the wet grinding medium, and mix by ball milling to obtain the mixed material powder; the molding agent in this embodiment is paraffin, and the addition amount of paraffin is 2-4wt%; the ball milling medium is hexane, and the appropriate addition amount of hexane can be determined according to actual needs.

[0032] Step 2: Press the mixed powder into a compact to obtain a compact, with a molding pressure of > 0.8 t / cm 2 .

[0033] Step 3: Place the compact in a sintering furnace for sintering. The sintering process is as follows:

[0034] ①Rise the room temperature to 600℃, remove the molding agent paraffin, and the heating rate is less than 2℃ / min;

[0035] ② Continue to heat up to 900℃ to 1250℃, with a heating rate of ≥6℃ / min;

[0036] ③Then raise the temperature to 1420℃-1460℃, keep the temperature at 1420℃-1460℃ for 30 minutes, then fill in 3-5MPa argon gas, maintain the pressure for 0.5-1h, and sinter the product.

[0037] Example 1

[0038] In this embodiment, a cemented carbide material for heavy-duty cutting tools is used, and the mass fractions of raw material powder are as follows: WC 77.8 parts, Co 11.2 parts, TaC 6 parts, TiC 4 parts, TiN 1 part, WC is mixed crystal, and the mass ratio of the mixed crystal is (1-3 μm): (4-6 μm) = 12:88. The parts in this embodiment are mass percentages (%).

[0039] The preparation method is the same as the general description of the scheme, and the prepared hard alloy material ZS1 is measured to have a bending strength of 3255MPa, a Rockwell hardness of 90.1HRA, and a gradient layer thickness of 21μm. The metallographic structure photo is shown in Figure 1As shown (the scale bar is 10μm). Among them, the bending strength refers to GB / T 3851-2015 Cemented Carbide Transverse Fracture Strength Determination Method; Rockwell hardness refers to GB / T 230.1-2018 Metallic Material Rockwell Hardness Test Method; metallographic structure refers to GB / T 3488.1-2014 Microstructure Metallographic Determination Method.

[0040] Example 2

[0041] In this embodiment, a cemented carbide material for heavy-duty cutting tools is used, and the mass fractions of raw material powder are as follows: WC 78.3 parts, Co 7 parts, TaC 8 parts, TiC 6 parts, TiN 0.7 parts, WC is mixed crystal, and the mass ratio of the mixed crystal is (1-3 μm): (4-6 μm) = 35:65. The parts in this embodiment are mass percentages (%).

[0042] The preparation method is the same as that in the general part of the scheme, and the prepared hard alloy material ZS2 is measured to have a bending strength of 27985MPa, a Rockwell hardness of 90.4HRA, and a gradient layer thickness of 23μm. The metallographic structure photo is shown in Figure 2 As shown (scale bar is 10 μm), the testing method is the same as that in Example 1.

[0043] Application Examples

[0044] The product ZS1 obtained in Example 1 was made into a turning blade CNMG190616, and the surface was coated with a CVD coating. A comparative test was conducted on site with a Sumitomo tool (brand 820P) at a certain manufacturer. The test results are shown in Table 1. The product ZS2 obtained in Example 2 was made into a turning blade SNMM250924, and the surface was coated with a CVD coating. A comparative test was conducted on site with a Sumitomo tool (brand 820P) at a certain manufacturer. The test results are shown in Table 2.

[0045] Table 1

[0046]

[0047]

[0048] Table 2

[0049]

[0050] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A cemented carbide material for heavy-duty cutting tools, characterized in that: The invention comprises the following raw materials in parts by weight: 69-81.8 parts of WC, 8-12 parts of Co, 4-8 parts of TaC, 6-10 parts of TiC, and 0.2-1 parts of TiN; WC is mixed crystal; A method for preparing a cemented carbide material for a heavy-duty cutting tool comprises the following steps: Step 1: mixing, adding a molding agent and a wet grinding medium to the raw materials, and wet grinding to obtain a mixed material powder; Step 2, pressing and forming to obtain a compact; Step 3: Sintering: Under the protection of high-pressure argon, sintering is performed in a stepwise heating manner to obtain an alloy material; The sintering process is as follows: ①Rise the room temperature to 600℃, remove the molding agent paraffin, and the heating rate is less than 2℃ / min; ② Continue to heat up to 900℃ to 1250℃, with a heating rate of ≥6℃ / min; ③Then the temperature is raised to 1420℃-1460℃, and after keeping the temperature at 1420℃-1460℃ for 30 minutes, 3-5MPa argon is filled in, and the pressure is maintained for 0.5-1h to sinter the product, which has a gradient structure alloy with a β-phase layer removed.

2. The cemented carbide material for heavy-duty cutting tools according to claim 1, characterized in that: The mixed crystal mass ratio is (1-3 μm):(4-6 μm)=(12-35):(65-88).

3. The method for preparing a cemented carbide material for a heavy-duty cutting tool according to claim 1 or 2, characterized in that: The steps include: Step 1: mixing, adding a molding agent and a wet grinding medium to the raw materials, and wet grinding to obtain a mixed material powder; Step 2, pressing and forming to obtain a compact; Step 3: Sintering: Under the protection of high-pressure argon, the alloy material is sintered by step-by-step heating.

4. The method for preparing a cemented carbide material for a heavy-duty cutting tool according to claim 3, characterized in that: In step 1, the molding agent is paraffin, and the addition amount of the paraffin is 2-4%.

5. The method for preparing a cemented carbide material for a heavy-duty cutting tool according to claim 4, characterized in that: In step 1, the wet grinding medium is hexane.

6. The method for preparing a cemented carbide material for a heavy-duty cutting tool according to claim 5, characterized in that: In step 2, the molding pressure is > 0.8t / cm 2 .

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