TiB2-reinforced ultra-coarse grain WC-Co-based hard alloy for spherical teeth of shield tunneling machine and preparation method of TiB2-reinforced ultra-coarse grain WC-Co-based hard alloy

Abstract

The TiB2-reinforced ultra-coarse grain WC-Co-based hard alloy for the spherical teeth of the shield tunneling machine comprises the following components in percentage by mass: 10 percent of Co, 1 percent of TiB2 and the balance of WC powder, and a preparation method of the TiB2-reinforced ultra-coarse grain WC-Co-based hard alloy comprises the following steps: 1, preparing WC-Co-TiB2 composite powder; 2, preparing a blank of the WC-Co-TiB2 composite powder; and thirdly, the WC-Co-TiB2 hard alloy material is sintered. TiB2 is added through a wet chemical method, the ball milling time, the rotating speed and the ball-to-material ratio are controlled in the ball milling process, the hardness and the fracture toughness of the hard alloy are effectively improved, the hardness of the WC-Co-TiB2 hard alloy prepared through the method can reach 1252.32 kg / mm < 2 >, the fracture toughness reaches 17.53 MPa.m < 1 / 2 >, the service life of the hard alloy in a severe environment is prolonged, and the WC-Co-TiB2 hard alloy is suitable for industrial production. And the risk and the cost caused by damage of hard alloy parts are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten-based cemented carbide, and relates to an ultra-coarse-grained WC-Co-based cemented carbide for shield machine ball teeth and a preparation method thereof, and more specifically, relates to an ultra-coarse-grained WC-Co-based cemented carbide for shield machine ball teeth reinforced with TiB2 and a preparation method thereof. Background Art

[0002] Tungsten-based cemented carbide for shield machine tooth top refers to a metal-based composite material prepared by a certain proportion of WC (carbide of refractory metal W) and metal binders such as Co, Ni, Fe, etc. into a composite powder and then sintering the powder. Tungsten-based cemented carbide has high hardness, high toughness, heat resistance and corrosion resistance. It can still maintain a high hardness when working at high temperatures. It is widely used in mechanical processing, drilling, mining, molds and other fields.

[0003] WC-Co cemented carbide is composed of refractory metal compound WC and bonding phase Co. It is a metal ceramic material prepared by adjusting the material formula, molding process, and high-temperature sintering under a protective atmosphere. Its excellent combination of hardness, toughness, ductility, strength, and wear resistance makes WC-Co the preferred material for manufacturing various wear-resistant parts. However, with the continuous changes in the production environment and the continuous improvement of performance requirements, the performance of traditional WC-Co cemented carbide is increasingly unable to meet today's actual production needs, which is mainly reflected in the following aspects: (1) When conducting geological exploration, the sand and stone of traditional WC-Co cemented carbide will wear the shield machine cutter head too quickly, which is prone to problems such as edge deformation, affecting the service life and efficiency; (2) In some heavy-load excavation or high-impact working environments, the strength of traditional WC-Co cemented carbide is difficult to withstand large cutting and impact forces, which can easily lead to cutter head fracture and damage, increasing production costs and processing cycles; (3) Although WC-Co cemented carbide has a certain toughness, in some complex working conditions, such as encountering hard soil and hard rocks, its insufficient toughness will become prominent, and cracks will easily occur, reducing the service life and work quality of the shield machine cutter head. Therefore, it is urgent to develop high-performance WC-Co cemented carbide. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a TiB2-reinforced ultra-coarse-grained WC-Co based cemented carbide for shield machine ball teeth and a preparation method thereof, which can make the second phase evenly distributed in the cemented carbide powder and make the grain size of the finished product after sintering be about 7μm, so that the hardness and fracture toughness of the WC-Co based cemented carbide material are significantly improved.

[0005] The technical solution of the present invention: A TiB2-reinforced ultra-coarse-grained WC-Co-based hard alloy for shield machine ball teeth, wherein the characteristic components are composed of Co: 10wt%, TiB2: 1wt%, and the balance is WC powder in terms of mass percentage.

[0006] A method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth comprises the following steps: 1. Preparation of WC-Co-TiB2 composite powder WC powder, Co powder, nano-TiB2 powder, PEG and grinding balls are placed in a ball mill, soaked with an appropriate amount of anhydrous ethanol, and after ensuring that the liquid level covers the powder and the grinding balls, the ball mill is placed in a glove box to evacuate, and then argon gas is introduced, the ball mill is sealed and taken out, and then the ball mill is wet-milled and mixed in a planetary ball mill for several hours, and then the ball-milled mixed powder slurry is placed in a blast drying oven to dry and sieve to obtain WC-Co-TiB2 composite powder; 2. Preparation of WC-Co-TiB2 composite powder The WC-Co-TiB2 composite powder obtained in step 1 is placed in a required mold for pre-compression to obtain block samples of different shapes; 3. Sintering of WC-Co-TiB2 cemented carbide materials The sample obtained in step 2 is placed in a low-pressure sintering furnace for sintering. The temperature is first raised to 600°C and kept for 30 minutes, and then raised to 1460°C and kept for 90 minutes. After keeping warm, the sample is cooled in the furnace to obtain a WC-Co-TiB2 cemented carbide material.

[0007] Preferably, in step 1, WC (Xiamen Tungsten Co., Ltd.) with a particle size of 20 μm, Co (Nanjing Hanrui Cobalt Co., Ltd.) with a particle size of 1-2 μm, and TiB2 (McLean) with a particle size of 3-5 μm.

[0008] Preferably, in step 1, the ball milling mixing is carried out for 17 to 22 hours, the ball-to-material ratio is 3:1, the grinding balls are a mixture of two small balls of φ7 mm and φ8 mm, the rotation speed is 110 to 130 r / min, and the ball milling is carried out using a carbide ball mill jar and grinding balls.

[0009] Preferably, in step 1, the product is dried in a blast drying oven at 75° C. to 85° C. for 4 to 6 hours, and the sieve mesh number is 80 mesh.

[0010] Preferably, the pre-pressing pressure in step 2 is 20 MPa.

[0011] Preferably, in step three, the sintering heating rate is 15° C. / min and the sintering pressure is 6 MPa.

[0012] Beneficial effects of the present invention: TiB2 is added by a wet chemical method, and is combined with WC and Co to generate WCoB and TiC during the sintering process, thereby realizing the second strengthening in the crystal and effectively improving the hardness of the cemented carbide; the additive TiB2 can also purify the interface, improve the wettability of the interface and the bonding phase, thereby promoting the filling of the voids by the liquid phase, reducing the porosity of the alloy, and effectively maintaining the fracture toughness of the cemented carbide in combination with the high toughness of the 10%Co ultra-coarse-grained cemented carbide itself; in addition, the ball milling time, rotation speed, and ball-to-material ratio are controlled in the ball milling process, so that the final sample composition is uniform, and the grain size is stabilized at about 7μm, thereby effectively improving the hardness and fracture toughness of the cemented carbide, and the hardness of the WC-Co-TiB2 cemented carbide prepared by the present invention can reach 1252.32kg / mm 2 , the fracture toughness reached 17.53MPa·m 1 / 2 Compared with traditional WC-Co cemented carbide (hardness 1097.12kg / mm 2 , fracture toughness 28.52MPa·m 1 / 2 ) has been significantly improved, thereby increasing the service life of cemented carbide in harsh environments and reducing the risks and costs caused by damage to cemented carbide parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the microscopic morphology of the WC-Co-TiB2 composite powder in Example 1.

[0014] Figure 2 The microscopic morphology of the cemented carbide composite materials in Examples 1 to 3, Comparative Example 1, and Comparative Example 2.

[0015] in: Figure 2 (a) is the morphology of the WC-Co cemented carbide composite material in Comparative Example 1; Figure 2 (b) is the morphology of the WC-Co-TiB2 cemented carbide composite material in Example 1; Figure 2 (c) is the morphology of the WC-Co-TiB2 cemented carbide composite material in Example 2; Figure 2 (d) is the morphology of the WC-Co-TiB2 cemented carbide composite material in Example 3; Figure 2 (e) is the morphology of the WC-Co-TiB2 cemented carbide composite material in Comparative Example 2.

[0016] Figure 3 The XRD diagrams of the cemented carbide composite materials prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 are shown.

[0017] Figure 4The particle size distribution diagram of the cemented carbide composite material prepared in Examples 1 to 3, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0018] Below, in conjunction with the accompanying drawings and specific embodiments, the present invention is further described. It should be noted that, under the premise of no conflict, the embodiments described below or the technical features can be arbitrarily combined to form new embodiments. The specific techniques or conditions not specified in the embodiments are carried out according to the techniques or conditions described in the literature in this field, and the reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased on the market.

[0019] The mass percentage compositions of the components in the following embodiments are respectively: Comparative Example 1: Co: 10wt%, TiB2: 0wt%, and the balance is WC; Example 1: Co: 10wt%, TiB2: 0.5wt%, and the balance is WC; Example 2: Co: 10wt%, TiB2: 1wt%, and the balance is WC; Example 3: Co: 10wt%, TiB2: 1.5wt%, and the balance is WC; Comparative Example 2: Co: 10wt%, TiB2: 2wt%, and the balance is WC.

[0020] Example 1 A method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth, which comprises taking WC powder, Co powder and TiB2 powder as raw materials, adding a molding agent, and sequentially performing batching, ball milling, drying, extrusion molding and pressure sintering to obtain the product, specifically comprising: According to the composition ratio of this embodiment, WC, Co and TiB2 are placed in a ball mill, and grinding balls are placed in the ball mill according to the ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 8:1, anhydrous ethanol is added to cover the materials in the ball mill, and the ball mill is placed in a glove box, argon gas is introduced and sealed; The ball mill was placed on a planetary ball mill for 20 h at a speed of 120 r / min. The ball-milled slurry was placed in a blast drying oven for drying and sieving, wherein the drying temperature was 75°C, the drying time was 5 hours, and the sieving mesh number was 80 meshes, thereby obtaining WC-Co-TiB2 composite powder; The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed by a hydraulic press at a pressing pressure of 20 MPa. The pressed sample was placed in a low-pressure sintering furnace for sintering at a heating rate of 15°C / min and a sintering pressure of 6MPa. The temperature was first raised to 600°C and kept for 30 minutes, then raised to 1460°C and kept for 90 minutes. After the insulation was completed, it was cooled with the furnace to obtain a WC-Co-TiB2 cemented carbide composite material.

[0021] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material are 1131.38 kg / mm 2 and 20.21MPa·m 1 / 2 .

[0022] Depend on Figure 1 It can be seen that the WC-Co-TiB2 composite powder prepared in this embodiment has uniform particle distribution. The WC particles are broken due to ball milling. By controlling the ball milling process, the average particle size is about 10 μm.

[0023] Depend on Figure 2 (b) It can be seen that the WC grains in the WC-Co-TiB2 composite powder prepared in this embodiment are evenly distributed, and there are no abnormally grown grains and pores.

[0024] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces trace amounts of two reinforcing phases, WCoB and TiC, in the cemented carbide, thereby increasing the hardness of the composite material.

[0025] Depend on Figure 4 It can be seen that the grain size of the WC-Co-TiB2 composite powder prepared in this embodiment is about 7 μm.

[0026] Example 2 A preparation method of TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for shield machine ball teeth, using WC powder, Co powder, and TiB2 powder as raw materials, adding a molding agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the product, specifically comprising: According to the composition ratio of this embodiment, WC, Co and TiB2 are placed in a ball mill, and grinding balls are placed in the ball mill according to the ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 9:1, anhydrous ethanol is added to cover the materials in the ball mill, and the ball mill is placed in a glove box, argon gas is introduced and sealed; The ball mill was placed on a planetary ball mill for 21 h at a speed of 120 r / min. The ball-milled slurry was placed in a blast drying oven for drying and sieving, wherein the drying temperature was 75°C, the drying time was 6 hours, and the sieving mesh number was 80 meshes, thereby obtaining WC-Co-TiB2 composite powder; The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold, and the composite powder was pre-pressed using a hydraulic press with a pressing pressure of 20 MPa.

[0027] The pressed sample was placed in a low-pressure sintering furnace for sintering at a heating rate of 15°C / min and a sintering pressure of 6MPa. The temperature was first raised to 600°C and kept for 30 minutes, then raised to 1460°C and kept for 90 minutes. After the insulation, it was cooled with the furnace to obtain a WC-Co-TiB2 cemented carbide composite material.

[0028] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material are 1252.32 kg / mm 2 and 17.53MPa·m 1 / 2 , the performance is greatly improved compared with that of Comparative Example 1.

[0029] Depend on Figure 2 (c) It can be seen that the WC grains in the WC-Co-TiB2 composite powder prepared in this embodiment are evenly distributed, and there are no abnormally grown grains and pores.

[0030] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces a small amount of two strengthening phases, WCoB and TiC, in the cemented carbide, thereby improving the hardness of the composite material.

[0031] Depend on Figure 4 It can be seen that the grain size of the WC-Co-TiB2 composite powder prepared in this embodiment is about 7 μm.

[0032] Example 3 A preparation method of TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for shield machine ball teeth, using WC powder, Co powder, and TiB2 powder as raw materials, adding a molding agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the product, specifically comprising: According to the composition ratio of this embodiment, WC, Co and TiB2 are placed in a ball mill, and grinding balls are placed in the ball mill according to the ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 7:1, anhydrous ethanol is added to cover the materials in the ball mill, and the ball mill is placed in a glove box, argon gas is introduced and sealed; The ball mill was placed on a planetary ball mill for 22 h at a speed of 120 r / min. The ball-milled slurry was placed in a blast drying oven for drying and sieving, wherein the drying temperature was 85°C, the drying time was 4 hours, and the sieving mesh number was 80 meshes, thereby obtaining WC-Co-TiB2 composite powder; The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed by a hydraulic press at a pressing pressure of 20 MPa. The pressed sample was placed in a low-pressure sintering furnace for sintering at a heating rate of 15°C / min and a sintering pressure of 6MPa. The temperature was first raised to 600°C and kept for 30 minutes, then raised to 1460°C and kept for 90 minutes. After the insulation, it was cooled with the furnace to obtain a WC-Co-TiB2 cemented carbide composite material.

[0033] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1304.34 kg / mm 2 and 11.07MPa·m 1 / 2 .

[0034] Depend on Figure 2 (d) It can be seen that the WC grains in the WC-Co-TiB2 composite powder prepared in this embodiment are evenly distributed, and there are no abnormally grown grains and pores.

[0035] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces two strengthening phases, WCoB and TiC, in the cemented carbide, thereby improving the hardness of the composite material.

[0036] Depend on Figure 4 It can be seen that the grain size of the WC-Co-TiB2 cemented carbide composite material in this embodiment is about 7 μm.

[0037] Comparative Example 1 A method for preparing ultra-coarse-grained WC-Co cemented carbide for shield machine ball teeth, using WC powder and Co powder as raw materials, adding a molding agent, and sequentially performing batching, ball milling, drying, extrusion molding and pressure sintering to obtain the product, specifically comprising: According to the composition ratio of this embodiment, WC and Co are placed in a ball mill, and grinding balls are placed in the ball mill according to the ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 8:1, anhydrous ethanol is added to cover the materials in the ball mill, and the ball mill is placed in a glove box, argon gas is introduced and sealed; The ball mill was placed on a planetary ball mill for 18 h at a speed of 120 r / min. The ball-milled slurry was placed in a blast drying oven for drying and sieving, wherein the drying temperature was 75°C, the drying time was 6 hours, and the sieving mesh number was 80 meshes, thereby obtaining WC-Co composite powder; The obtained WC-Co composite powder was loaded into a pressing mold and pre-pressed by a hydraulic press at a pressing pressure of 20 MPa. The pressed sample was placed in a low-pressure sintering furnace for sintering at a heating rate of 15°C / min and a sintering pressure of 6MPa. The temperature was first raised to 600°C and kept for 30 minutes, then raised to 1460°C and kept for 90 minutes. After the insulation was completed, it was cooled in the furnace to obtain a WC-Co cemented carbide composite material.

[0038] In this comparative example, the Vickers hardness and fracture toughness of the sintered WC-Co cemented carbide composite material reached 1097.12 kg / mm 2 and 28.52MPa·m 1 / 2 .

[0039] Depend on Figure 2 (a) It can be seen that in this comparative example, the WC grains in the WC-Co cemented carbide composite material are evenly distributed, and there are no abnormally grown grains and pores.

[0040] Depend on Figure 4 It can be seen that in this comparative example, the grain size of the WC-Co cemented carbide composite material is about 7 μm.

[0041] Comparative Example 2 A preparation method of TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for shield machine ball teeth, using WC powder, Co powder, and TiB2 powder as raw materials, adding a molding agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the product, specifically comprising: According to the composition ratio of this embodiment, WC, Co and TiB2 are placed in a ball mill, and grinding balls are placed in the ball mill according to the ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 9:1, anhydrous ethanol is added to cover the materials in the ball mill, and the ball mill is placed in a glove box, argon gas is introduced and sealed; The ball mill was placed on a planetary ball mill for 19 h at a speed of 120 r / min. The ball-milled slurry was placed in a blast drying oven for drying and sieving, wherein the drying temperature was 75°C, the drying time was 5 hours, and the sieving mesh number was 80 meshes, thereby obtaining WC-Co-TiB2 composite powder; The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed by a hydraulic press at a pressing pressure of 20 MPa. The pressed sample was placed in a low-pressure sintering furnace for sintering at a heating rate of 15°C / min and a sintering pressure of 6MPa. The temperature was first raised to 600°C and kept for 30 minutes, then raised to 1460°C and kept for 90 minutes. After the insulation, it was cooled with the furnace to obtain a WC-Co-TiB2 cemented carbide composite material.

[0042] In this comparative example, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1353.17 kg / mm 2 and 8.89MPa·m 1 / 2 .

[0043] Depend on Figure 2 (e) It can be seen that the WC grains in the WC-Co-TiB2 cemented carbide composite material prepared in this comparative example are evenly distributed, and there are no abnormally grown grains and pores.

[0044] Depend on Figure 3 It can be seen that the addition of TiB2 in this comparative example produces two strengthening phases, WCoB and TiC, in the cemented carbide, which increases the hardness of the composite material and significantly reduces the fracture toughness.

[0045] Depend on Figure 4 It can be seen that the grain size of the WC-Co-TiB2 cemented carbide composite material prepared in this comparative example is about 7 μm.

[0046] The performance tests were performed on the hard alloy composite materials obtained in Examples 1 to 3 and Comparative Examples 1 to 2. The test results are shown in Table 1: Table 1 Performance test results of Examples 1 to 3 and Comparative Examples 1 to 2 It can be seen from Table 1 that with the increase of TiB2 addition, the Vickers hardness of the prepared cemented carbide composite material increases, but the fracture toughness decreases. Due to the high wear resistance of the ultra-coarse-grained cemented carbide itself, it can still maintain a high fracture toughness after adding a small amount of TiB2. Considering the hardness and fracture toughness of the comprehensive material, when the TiB2 addition is 1%, the comprehensive performance of the cemented carbide is the best, and the Vickers hardness reaches 1252.32kg / mm 2 , the fracture toughness reached 17.53MPa·m 1 / 2 Compared with traditional WC-Co cemented carbide (hardness 1097.12kg / mm 2 , fracture toughness 28.52MPa·m 1 / 2 ), the cemented carbide of the present application is more suitable for shield machine ball teeth to work in harsh service environments. It maintains the long life of the components while ensuring the excavation efficiency, and is of great significance to the research on cemented carbide ball teeth for shield machines.

[0047] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for shield machine ball teeth, characterized in that: Its components are as follows according to mass percentage: Co: 10wt%, TiB2: 1wt%, and the balance is WC powder.

2. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth as claimed in claim 1, characterized in that: The steps include:

1. Preparation of WC-Co-TiB2 composite powder WC powder, Co powder, nano-TiB2 powder, PEG and grinding balls are placed in a ball mill, soaked with an appropriate amount of anhydrous ethanol, and after ensuring that the liquid level covers the powder and the grinding balls, the ball mill is placed in a glove box to evacuate, and then argon gas is introduced, the ball mill is sealed and taken out, and then the ball mill is wet-milled and mixed in a planetary ball mill for several hours, and then the ball-milled mixed powder slurry is placed in a blast drying oven to dry and sieve to obtain WC-Co-TiB2 composite powder; 2. Preparation of WC-Co-TiB2 composite powder The WC-Co-TiB2 composite powder obtained in step 1 is placed in a required mold for pre-compression to obtain block samples of different shapes; 3. Sintering of WC-Co-TiB2 cemented carbide materials The sample obtained in step 2 is placed in a low-pressure sintering furnace for sintering. The temperature is first raised to 600°C and kept for 30 minutes, and then raised to 1460°C and kept for 90 minutes. After keeping warm, the sample is cooled in the furnace to obtain a WC-Co-TiB2 cemented carbide material.

3. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co based cemented carbide for shield machine ball teeth as claimed in claim 1, characterized in that: In the step 1, the WC particle size is 20 μm, the Co particle size is 1-2 μm, and the TiB2 particle size is 3-5 μm.

4. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth as claimed in claim 1, characterized in that: In the step 1, the ball milling is performed for 17 to 22 hours, the ball-to-material ratio is 3:1, the grinding balls are a mixture of two small balls of φ7 mm and φ8 mm, the rotation speed is 110 to 130 r / min, and the ball milling is performed using a carbide ball mill jar and grinding balls.

5. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth as claimed in claim 1, characterized in that: In the step 1, the mixture is dried in a blast drying oven at 75° C. to 85° C. for 4 to 6 hours and the sieve mesh number is 80 meshes.

6. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for a shield machine ball tooth as claimed in claim 1, characterized in that: The pre-pressing pressure in step 2 is 20 MPa.

7. The method for preparing a TiB2-reinforced ultra-coarse-grained WC-Co based cemented carbide for a shield machine ball tooth as claimed in claim 1, characterized in that: In the step three, the sintering heating rate is 15°C / min and the sintering pressure is 6MPa.

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