TiB2 reinforced ultra-coarse grain WC-Co based hard alloy for use in a shield machine ball and its preparation method

Abstract

The application discloses a TiB2 reinforced super-coarse-grained WC-Co based hard alloy for a shield machine ball, which is composed of Co: 10wt%, TiB2: 1wt%, and the balance of WC powder, and a preparation method thereof, which comprises the following steps: one, preparation of WC-Co-TiB2 composite powder; two, preparation of WC-Co-TiB2 composite powder; three, sintering of WC-Co-TiB2 hard alloy material. The application adds TiB2 by a wet chemical method, controls the ball milling time, rotating speed and ball-to-material ratio in the ball milling process, effectively improves the hardness and fracture toughness of the hard alloy, and the hardness of the WC-Co-TiB2 hard alloy prepared by the application 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 harsh environments is improved, and the risk and cost caused by damage of the hard alloy parts are reduced.

Description

Technical Field

[0001] This invention belongs to the field of tungsten-based cemented carbide technology, and relates to an ultra-coarse-grained WC-Co-based cemented carbide for shield machine ball teeth and its preparation method. More specifically, it relates to a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for shield machine ball teeth and its preparation method. Background Technology

[0002] Tungsten-based cemented carbide for tunnel boring machine tooth tips is a metal-based composite material prepared by mixing WC (carbide of refractory metal W) with metal binders such as Co, Ni, and Fe in a certain proportion to form a composite powder, which is then sintered. Tungsten-based cemented carbide possesses high hardness, high toughness, heat resistance, and corrosion resistance, and can maintain high hardness even at high temperatures. It is widely used in machining, drilling, mining, mold making, and other fields.

[0003] WC-Co cemented carbide is a metal-ceramic material composed of refractory metal compound WC and binder phase Co. It is prepared by adjusting the material formulation and molding process, and sintering at high temperature 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 the actual production needs of today. This is mainly reflected in the following aspects: (1) When traditional WC-Co cemented carbide is used for geological exploration and mining, sand and gravel wear the shield machine cutter head too quickly, which can easily lead to problems such as cutting edge deformation, affecting service life and efficiency; (2) In some heavy-load tunneling or high-impact work situations, the strength of traditional WC-Co cemented carbide is difficult to withstand large cutting forces and impact forces, which can easily lead to cutter head breakage 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, which can easily cause cracks, reduce the service life and working quality of shield machine cutter heads. Therefore, it is urgent to develop high-performance WC-Co cemented carbide. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for tunnel boring machine ball teeth and its preparation method. This method enables the second phase to be uniformly distributed in the cemented carbide powder and achieves a grain size of approximately 7 μm in the sintered product, thereby significantly improving the hardness and fracture toughness of the WC-Co-based cemented carbide material.

[0005] The technical solution of this invention:

[0006] A TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for tunnel boring machine ball teeth, the characteristic components of which are composed of Co: 10wt%, TiB2: 1wt%, and the balance being WC powder by mass percentage.

[0007] A method for preparing TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for tunnel boring machine ball teeth includes the following steps:

[0008] I. Preparation of WC-Co-TiB2 composite powder

[0009] WC powder, Co powder, nano TiB2 powder, PEG, and grinding balls were placed in a ball mill jar and soaked in an appropriate amount of anhydrous ethanol. After ensuring that the liquid level covered the powder and grinding balls, the ball mill jar was placed in a glove box and vacuumed. Then, argon gas was introduced, the ball mill jar was sealed, and the jar was removed. The ball mill jar was then wet-milled in a planetary ball mill for several hours. The milled mixed powder slurry was then placed in a forced-air drying oven to dry and sieve to obtain WC-Co-TiB2 composite powder.

[0010] II. Preparation of WC-Co-TiB2 composite powder

[0011] The WC-Co-TiB2 composite powder obtained in step one is pre-pressed into the required mold to obtain block samples of different shapes.

[0012] III. Sintering of WC-Co-TiB2 cemented carbide materials

[0013] The sample obtained in step two was placed in a low-pressure sintering furnace for sintering. The temperature was first raised to 600℃ and held for 30 minutes, then raised to 1460℃ and held for 90 minutes. After holding, the sample was cooled with the furnace to obtain WC-Co-TiB2 cemented carbide material.

[0014] Preferably, in step one, WC (Xiamen Tungsten) is used with a particle size of 20 μm, Co (Nanjing Hanrui Cobalt) with a particle size of 1~2 μm, and TiB2 (Maclean) with a particle size of 3~5 μm.

[0015] Preferably, in step one, the ball milling and mixing takes 17-22 hours, the ball-to-material ratio is 3:1, the grinding balls are a mixture of φ7mm and φ8mm small balls, the rotation speed is 110-130r / min, and a carbide ball milling jar and grinding balls are used for ball milling.

[0016] Preferably, in step one, the product is dried in a forced-air drying oven at 75℃~85℃ for 4~6 hours, and then sieved through a mesh of 80.

[0017] Preferably, the pre-compression pressure in step two is 20 MPa.

[0018] Preferably, the sintering heating rate in step three is 15℃ / min, and the sintering pressure is 6MPa.

[0019] The beneficial effects of this invention are as follows: By adding TiB2 via a wet chemical method, it combines with WC and Co during sintering to form WCoB and TiC, achieving a second strengthening effect within the grains and effectively improving the hardness of the cemented carbide. The TiB2 additive also purifies the interface, improving the wettability of the interface and the binder phase, thereby promoting the filling of voids by the liquid phase and reducing the porosity of the alloy. Combined with the high toughness of the 10% Co ultra-coarse-grained cemented carbide itself, this effectively maintains the fracture toughness of the cemented carbide. Furthermore, controlling the ball milling time, speed, and ball-to-material ratio during the ball milling process ensures uniform composition of the final sample and a stable grain size of approximately 7 μm. Therefore, it effectively improves the hardness and fracture toughness of the cemented carbide, and the WC-Co-TiB2 cemented carbide prepared by this invention can achieve a hardness of 1252.32 kg / mm². 2 The fracture toughness reached 17.53 MPa·m. 1 / 2 Compared to traditional WC-Co cemented carbide (hardness 1097.12 kg / mm²), 2 Fracture toughness 28.52 MPa·m 1 / 2 The performance is significantly improved, thus increasing the service life of cemented carbide in harsh environments and reducing the risks and costs associated with damage to cemented carbide parts. Attached Figure Description

[0020] Figure 1 This is a microscopic morphology diagram of the WC-Co-TiB2 composite powder in Example 1.

[0021] Figure 2 The images show the microstructure of the cemented carbide composite materials in Examples 1-3, Comparative Example 1, and Comparative Example 2.

[0022] in: Figure 2 (a) is a morphology diagram of the WC-Co cemented carbide composite material in Comparative Example 1;

[0023] Figure 2 (b) is a morphology diagram of the WC-Co-TiB2 cemented carbide composite material in Example 1;

[0024] Figure 2 (c) is a morphology diagram of the WC-Co-TiB2 cemented carbide composite material in Example 2;

[0025] Figure 2 (d) is a morphology diagram of the WC-Co-TiB2 cemented carbide composite material in Example 3;

[0026] Figure 2 (e) is a morphology diagram of the WC-Co-TiB2 cemented carbide composite material in Comparative Example 2.

[0027] Figure 3The images show the XRD patterns of the cemented carbide composite materials prepared in Examples 1-3, Comparative Example 1, and Comparative Example 2.

[0028] Figure 4 The particle size distribution diagrams are for the cemented carbide composite materials prepared in Examples 1-3, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Where specific techniques or conditions are not specified in the embodiments, they are carried out according to the techniques or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased on the market.

[0030] The mass percentage composition of the components in the following examples is as follows: Comparative Example 1: Co: 10wt%, TiB2: 0wt%, balance WC; Example 1: Co: 10wt%, TiB2: 0.5wt%, balance WC; Example 2: Co: 10wt%, TiB2: 1wt%, balance WC; Example 3: Co: 10wt%, TiB2: 1.5wt%, balance WC; Comparative Example 2: Co: 10wt%, TiB2: 2wt%, balance WC.

[0031] Example 1

[0032] A method for preparing TiB2-reinforced ultra-coarse-grained WC-Co-based cemented carbide for tunnel boring machine ball teeth involves using WC powder, Co powder, and TiB2 powder as raw materials, adding a forming agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the desired product. Specifically:

[0033] According to the component ratio of this embodiment, WC, Co, and TiB2 are placed in a ball milling jar. Grinding balls are placed in the ball milling jar at a ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 8:1. Anhydrous ethanol is used to cover the material in the ball milling jar. The ball milling jar is placed in a glove box, argon gas is introduced, and the box is sealed.

[0034] The ball milling jar was placed on a planetary ball mill and ball milled for 20 hours at a speed of 120 r / min.

[0035] The ball-milled slurry was placed in a forced-air drying oven for drying and sieving. The drying temperature was 75℃, the drying time was 5 hours, and the sieve mesh size was 80 mesh, thereby obtaining WC-Co-TiB2 composite powder.

[0036] The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed using a hydraulic press at a pressing pressure of 20 MPa.

[0037] The pressed sample was placed in a low-pressure sintering furnace for sintering. The heating rate was 15℃ / min and the sintering pressure was 6MPa. The temperature was first raised to 600℃ and held for 30min, then raised to 1460℃ and held for 90min. After the holding period, the sample was cooled with the furnace to obtain the WC-Co-TiB2 cemented carbide composite material.

[0038] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1131.38 kg / mm², respectively. 2 and 20.21 MPa·m 1 / 2 .

[0039] Depend on Figure 1 It can be seen that the WC-Co-TiB2 composite powder prepared in this embodiment has a uniform particle distribution. Due to the ball milling, the WC particles are broken. By controlling the ball milling process, the average particle size is about 10μm.

[0040] 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 uniformly distributed, and there are no abnormally large grains or pores.

[0041] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces trace amounts of WCoB and TiC reinforcing phases in the cemented carbide, thereby increasing the hardness of the composite material.

[0042] 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.

[0043] Example 2

[0044] A method for preparing TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for tunnel boring machine ball teeth involves using WC powder, Co powder, and TiB2 powder as raw materials, adding a forming agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the desired product. Specifically:

[0045] According to the component ratio of this embodiment, WC, Co, and TiB2 are placed in a ball milling jar. Grinding balls are placed in the ball milling jar at a ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 9:1. Anhydrous ethanol is used to cover the material in the ball milling jar. The ball milling jar is placed in a glove box, argon gas is introduced, and the box is sealed.

[0046] The ball milling jar was placed on a planetary ball mill and ball milled for 21 hours at a speed of 120 r / min.

[0047] The ball-milled slurry was placed in a forced-air drying oven for drying and sieving. The drying temperature was 75℃, the drying time was 6 hours, and the sieve mesh size was 80 mesh, thereby obtaining WC-Co-TiB2 composite powder.

[0048] The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed using a hydraulic press at a pressure of 20 MPa.

[0049] The pressed sample was placed in a low-pressure sintering furnace for sintering. The heating rate was 15℃ / min and the sintering pressure was 6MPa. The temperature was first raised to 600℃ and held for 30 min, then raised to 1460℃ and held for 90 min. After the holding period, the sample was cooled with the furnace to obtain the WC-Co-TiB2 cemented carbide composite material.

[0050] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1252.32 kg / mm², respectively. 2 and 17.53 MPa·m 1 / 2 Compared to Comparative Example 1, the performance is significantly improved.

[0051] 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 uniformly distributed, and there are no abnormally large grains or pores.

[0052] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces a small amount of WCoB and TiC reinforcing phases in the cemented carbide, which improves the hardness of the composite material.

[0053] 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.

[0054] Example 3

[0055] A method for preparing TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for tunnel boring machine ball teeth involves using WC powder, Co powder, and TiB2 powder as raw materials, adding a forming agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the desired product. Specifically:

[0056] According to the component ratio of this embodiment, WC, Co, and TiB2 are placed in a ball milling jar. Grinding balls are placed in the ball milling jar at a ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 7:1. Anhydrous ethanol is used to cover the material in the ball milling jar. The ball milling jar is placed in a glove box, argon gas is introduced, and the box is sealed.

[0057] The ball milling jar was placed on a planetary ball mill and ball milled for 22 hours at a speed of 120 r / min.

[0058] The ball-milled slurry was placed in a forced-air drying oven for drying and sieving. The drying temperature was 85℃, the drying time was 4 hours, and the sieve mesh size was 80 mesh, thereby obtaining WC-Co-TiB2 composite powder.

[0059] The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed using a hydraulic press at a pressing pressure of 20 MPa.

[0060] The pressed sample was placed in a low-pressure sintering furnace for sintering. The heating rate was 15℃ / min and the sintering pressure was 6MPa. The temperature was first raised to 600℃ and held for 30 min, then raised to 1460℃ and held for 90 min. After the holding period, the sample was cooled with the furnace to obtain the WC-Co-TiB2 cemented carbide composite material.

[0061] In this embodiment, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1304.34 kg / mm², respectively. 2 and 11.07 MPa·m 1 / 2 .

[0062] 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 uniformly distributed, and there are no abnormally large grains or pores.

[0063] Depend on Figure 3 It can be seen that the addition of TiB2 in this embodiment produces two reinforcing phases, WCoB and TiC, in the cemented carbide, which improves the hardness of the composite material.

[0064] 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.

[0065] Comparative Example 1

[0066] A method for preparing ultra-coarse-grained WC-Co cemented carbide for tunnel boring machine ball teeth involves using WC powder and Co powder as raw materials, adding a forming agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the desired product. Specifically:

[0067] According to the component ratio of this embodiment, WC and Co are placed in a ball milling jar, and grinding balls are placed in the ball milling jar at a ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 8:1. Anhydrous ethanol is used to cover the material in the ball milling jar, and the ball milling jar is placed in a glove box, argon gas is introduced and sealed.

[0068] The ball milling jar was placed on a planetary ball mill and ball milled for 18 hours at a speed of 120 r / min.

[0069] The ball-milled slurry was placed in a forced-air drying oven for drying and sieving. The drying temperature was 75℃, the drying time was 6 hours, and the sieve mesh size was 80 mesh, thereby obtaining WC-Co composite powder.

[0070] The obtained WC-Co composite powder was loaded into a pressing mold and pre-pressed using a hydraulic press at a pressure of 20 MPa.

[0071] The pressed sample was placed in a low-pressure sintering furnace for sintering. The heating rate was 15℃ / min and the sintering pressure was 6MPa. The temperature was first raised to 600℃ and held for 30min, then raised to 1460℃ and held for 90min. After the holding period, the sample was cooled with the furnace to obtain the WC-Co cemented carbide composite material.

[0072] In this comparative example, the Vickers hardness and fracture toughness of the sintered WC-Co cemented carbide composite material reached 1097.12 kg / mm², respectively. 2 and 28.52 MPa·m 1 / 2 .

[0073] 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 uniformly distributed, and there are no abnormally large grains or pores.

[0074] 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.

[0075] Comparative Example 2

[0076] A method for preparing TiB2-reinforced ultra-coarse-grained WC-Co cemented carbide for tunnel boring machine ball teeth involves using WC powder, Co powder, and TiB2 powder as raw materials, adding a forming agent, and sequentially performing batching, ball milling, drying, extrusion molding, and pressure sintering to obtain the desired product. Specifically:

[0077] According to the component ratio of this embodiment, WC, Co, and TiB2 are placed in a ball milling jar. Grinding balls are placed in the ball milling jar at a ball-to-material ratio of 3:1, wherein the mixing ratio of φ7mm and φ8mm small balls is 9:1. Anhydrous ethanol is used to cover the material in the ball milling jar. The ball milling jar is placed in a glove box, argon gas is introduced, and the box is sealed.

[0078] The ball milling jar was placed on a planetary ball mill and ball milled for 19 hours at a speed of 120 r / min.

[0079] The ball-milled slurry was placed in a forced-air drying oven for drying and sieving. The drying temperature was 75℃, the drying time was 5 hours, and the sieve mesh size was 80 mesh, thereby obtaining WC-Co-TiB2 composite powder.

[0080] The obtained WC-Co-TiB2 composite powder was loaded into a pressing mold and pre-pressed using a hydraulic press at a pressing pressure of 20 MPa.

[0081] The pressed sample was placed in a low-pressure sintering furnace for sintering. The heating rate was 15℃ / min and the sintering pressure was 6MPa. The temperature was first raised to 600℃ and held for 30 min, then raised to 1460℃ and held for 90 min. After the holding period, the sample was cooled with the furnace to obtain the WC-Co-TiB2 cemented carbide composite material.

[0082] In this comparative example, the Vickers hardness and fracture toughness of the sintered WC-Co-TiB2 cemented carbide composite material reached 1353.17 kg / mm², respectively. 2 and 8.89 MPa·m 1 / 2 .

[0083] 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 uniformly distributed, and there are no abnormally large grains or pores.

[0084] Depend on Figure 3 It can be seen that the addition of TiB2 in this comparative example produces two reinforcing phases, WCoB and TiC, in the cemented carbide, which increases the hardness of the composite material but significantly reduces its fracture toughness.

[0085] 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.

[0086] The performance of the cemented carbide composite materials prepared in Examples 1-3 and Comparative Examples 1-2 was tested, and the test results are shown in Table 1:

[0087] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-2

[0088] Table 1 shows that with the increase of TiB2 addition, the Vickers hardness of the prepared cemented carbide composite increases, but the fracture toughness decreases. Due to the high wear resistance of the ultra-coarse-grained cemented carbide itself, it can still maintain high fracture toughness after adding a small amount of TiB2. Considering both the hardness and fracture toughness of the material, the cemented carbide with the best overall performance is achieved when the TiB2 addition is 1%, with a Vickers hardness reaching 1252.32 kg / mm². 2 The fracture toughness reached 17.53 MPa·m. 1 / 2 Compared to traditional WC-Co cemented carbide (hardness 1097.12 kg / mm²), 2 Fracture toughness 28.52 MPa·m 1 / 2 The cemented carbide of this application is more suitable for shield machine ball teeth to work in harsh service environments, and maintains the long service life of the components while ensuring tunneling efficiency. It is of great significance to the research of cemented carbide ball teeth for shield machines.

[0089] The above-described embodiments are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a TiB2 reinforced ultra-coarse grain WC-Co based hard metal for use in a shield machine ball, characterized in that: The components are composed of Co: 10wt%, TiB2: 1wt%, and the balance of WC powder, including the following preparation steps: I. Preparation of WC-Co-TiB2 composite powder The WC powder, Co powder, nano-TiB2 powder, PEG, and grinding balls are placed in a ball mill tank, soaked with an appropriate amount of anhydrous ethanol, and then placed in a glove box to vacuumize. Subsequently, argon is introduced, the ball mill tank is sealed, taken out, and then wet-mixed in a planetary ball mill for several hours. Then, the mixed powder slurry is dried in a blast drying oven and sieved to obtain WC-Co-TiB2 composite powder. II. Preparation of WC-Co-TiB2 composite powder The WC-Co-TiB2 composite powder obtained in step one is loaded into the required mold for pre-pressing to obtain different shaped bulk samples. III. Sintering of WC-Co-TiB2 hard alloy material The sample obtained in step two is placed in a low-pressure sintering furnace for sintering. First, the temperature is raised to 600℃ for 30min, and then raised to 1460℃ for 90min. After the heat preservation, the furnace is cooled down to obtain the WC-Co-TiB2 hard alloy material.

2. The method of producing TiB2 reinforced ultra-coarse grain WC-Co based hard metal for a shield machine ball bit according to claim 1, characterized in that: In step one, the WC particle size is 20μm, the Co particle size is 1~2μm, and the TiB2 particle size is 3~5μm.

3. The method of producing TiB2 reinforced ultra-coarse grain WC-Co based hard metal for a shield machine ball bit according to claim 1, characterized in that: In step one, the ball milling time is 17~22h, the ball-to-material ratio is 3:1, the grinding balls are a mixture of φ7mm and φ8mm, the rotation speed is 110~130r / min, and the hard alloy ball mill tank and grinding balls are used for ball milling.

4. The method of producing TiB2 reinforced ultra-coarse grain WC-Co based hard metal for a shield machine ball bit according to claim 1, characterized in that: In step one, the drying is performed in a blast drying oven at 75℃~85℃ for 4~6h, and the sieving mesh size is 80 mesh.

5. The method of producing TiB2 reinforced ultra-coarse grain WC-Co based hard metal for a shield machine ball bit according to claim 1, characterized in that: In step two, the pre-pressing pressure is 20MPa.

6. The method of producing TiB2 reinforced ultra-coarse grain WC-Co based hard metal for a shield machine ball bit according to claim 1, characterized in that: In step three, the sintering temperature rising rate is 15℃ / min, and the sintering pressure is 6MPa.

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