A WC-Co hard alloy for mining and its preparation method

Abstract

This application relates to the field of cemented carbides, and specifically discloses a WC-Co cemented carbide for mining and its preparation method. The WC-Co cemented carbide for mining includes Co with a mass ratio of 15-30%, NbScN with 0-1.5%, NbC with 0-1.5%, and the balance being the hard phase WC; the hard phase WC includes ultra-coarse grain WC with an average grain size of 6.0-9.0 μm and medium grain WC with an average grain size of 1.0-3.0 μm. The WC-Co cemented carbide for mining of this application has the advantages of good comprehensive performance, high hardness, and good toughness.

Description

Technical Field

[0001] This application relates to the field of cemented carbides, and more specifically, to a WC-Co cemented carbide for mining and its preparation method. Background Art

[0002] Cemented carbides are widely used in fields such as cutting, infrastructure construction, mining, molds, and wear-resistant parts due to their excellent comprehensive properties. Among them, the WC-Co cemented carbide for mining is a very important part. WC-Co cemented carbide products for mining should have high hardness required to resist wear and high toughness required to resist impact fracture. As the working environment of WC-Co cemented carbide for mining becomes more and more harsh and the working conditions become more and more complex, higher requirements are put forward for the comprehensive properties of WC-Co cemented carbide for mining. How to synchronously achieve high toughness and high wear resistance as much as possible to improve the service life of cemented carbide has always been the goal and direction of the research on cemented carbide.

[0003] Ultra-coarse grain tungsten carbide exhibits excellent properties such as wear resistance and thermal fatigue resistance. However, when the grain size of tungsten carbide particles in cemented carbide increases, the size of the binder phase also increases, and the hardness of the binder phase is much lower than that of tungsten carbide. During the service process of cemented carbide, the binder phase will be limitedly worn, so the performance of the binder phase will greatly affect the life of cemented carbide. How to enhance the binder phase to improve the wear resistance and toughness of ultra-coarse cemented carbide is an urgent problem to be solved at present. Summary of the Invention

[0004] In order to obtain a cemented carbide product with high hardness and high toughness, this application provides a WC-Co cemented carbide for mining and its preparation method.

[0005] In a first aspect, this application provides a WC-Co cemented carbide for mining, adopting the following technical solution:

[0006] A WC-Co cemented carbide for mining includes Co with a mass ratio of 15 - 30%, NbScN with 0 - 1.5%, NbC with 0 - 1.5%, and the balance is the hard phase WC.

[0007] The hard phase WC includes ultra-coarse grain WC with an average grain size of 6.0 - 9.0 μm and medium grain WC with an average grain size of 1.0 - 3.0 μm.

[0008] By adopting the above technical solution, by adding medium-grained tungsten carbide, the medium-grained tungsten carbide can fill into the larger pores of the ultra-coarse-grained tungsten carbide, greatly reducing the voids existing between the tungsten carbide particles and forming a better dense arrangement between the particles; the medium-grained WC can partially dissolve in the liquid Co, playing a role in strengthening the Co binder phase, improving the hardness, wear resistance and service life of the binder phase; at the same time, by optimizing the ratio of the ultra-coarse-grained WC to the medium-grained WC, the cemented carbide is more superior in terms of properties such as fracture toughness, wear resistance and fatigue resistance.

[0009] NbC, as an inhibitor, can dissolve in the binder phase to produce solid solution strengthening or dispersion strengthening effects, inhibit the excessive growth of WC grains, and when the cemented carbide is subjected to external forces, it can play a pinning role in the dislocation movement in the binder phase, thereby being beneficial to improving the overall strength of the cemented carbide and significantly improving the comprehensive performance of the cemented carbide; at the same time, NbC can promote the solid solution or dispersion of NbScN in the binder phase, and the Sc and N elements in NbScN can refine grains, reduce grain boundaries, increase lattice distortion, improve the toughness and flexural strength of the cemented carbide, and Sc can also further enhance the hardness and wear resistance of the cemented carbide. Therefore, when NbC and NbScN are added together, hardness, wear resistance, toughness and anti-bending properties can be obtained. Further, the inventors found that the addition of medium-grained and the addition of NbScN and NbC unexpectedly improved the alloy strength, which may be due to the medium-grained, NbScN and NbC enhancing the strengthening effect of the binder phase through the above different mechanisms, thereby improving the hardness of the alloy.

[0010] Preferably, the cemented carbide comprises 0.5-1.0% of NbScN and 0.5-1.0% of NbC by mass ratio.

[0011] Preferably, the cemented carbide comprises 0.6% of NbScN and 0.8% of NbC by mass ratio.

[0012] By adopting the above technical solution, NbC and NbScN cooperate with each other, having a better solid solution strengthening effect on the Co binder phase, significantly improving the mechanical properties of the cemented carbide, increasing both the flexural strength and the fracture toughness, and to a certain extent being able to improve the wettability between the WC grains and the binder phase, inhibit the excessive growth of grains, and at the same time improve the corrosion resistance and oxidation resistance of the binder phase to a certain extent; when the content is 0.6% of NbScN and 0.8% of NbC, the alloy has the best performance, which may be because at the above ratio, the solid solution or dispersion effect of the two in the binder phase is the best, and the improvement of the alloy performance is the greatest.

[0013] In a second aspect, the present application provides a method for preparing a mining WC-Co cemented carbide, adopting the following technical solution:

[0014] A preparation method of WC-Co hard alloy for mining, comprising the following steps:

[0015] According to the ratio, mix super-coarse-grained WC powder and Co powder for batching, then add a molding agent accounting for 1.5-2.5% of the total weight of the batching, mix and wet grind for 14-20h, and then granulate by spray drying to obtain a super-coarse-grained mixture; the Fess particle size of the super-coarse-grained WC powder is 13-20μm;

[0016] According to the ratio, mix medium-grained WC powder, Co powder, NbScN alloy powder and NbC alloy powder for batching, then add a molding agent accounting for 1.5-2.5% of the total weight of the batching, mix and wet grind for 20-30h, and then granulate by spray drying to obtain a medium-grained mixture; the Fess particle size of the medium-grained WC powder is 2-8μm;

[0017] Mix the super-coarse-grained mixture and the medium-grained mixture in a mass ratio of (85:15)-(95:5) for 40-80min for batch mixing, press into shape, remove the molding agent by vacuum sintering, and then perform low-pressure hot isostatic pressing sintering at 1420-1450°C to obtain WC-Co hard alloy for mining.

[0018] By adopting the above technical solution, the super-coarse-grained mixture and the medium-grained mixture are respectively batched, wet ground, dried and granulated and then mixed and sintered, which helps to ensure the stability of the alloy structure during the sintering process, and can ensure the stable ratio of super-coarse-grained WC and medium-grained WC, avoiding the occurrence of grain size homogenization;

[0019] Through batch mixing, the super-coarse-grained mixture and the medium-grained mixture are evenly mixed, and the medium-grained mixture is dispersed between the super-coarse-grained mixtures, reducing the possibility of polycrystal formation due to the adjacency of super-coarse grains during pressing, and making the particle arrangement more dense, reducing the voids existing between WC particles;

[0020] During sintering, the smaller particles in the medium-grained WC dissolve into the liquid binder phase to strengthen the binder phase. The interfacial segregation and solid solution strengthening of NbScN and NbC further play a role in strengthening the binder phase, improving the wear resistance and toughness of the hard alloy, inhibiting the excessive growth of grains, and improving the wettability between the binder phase and the hard phase. The binder phase is distributed around the super-coarse-grained WC, further promoting sintering densification and improving the hardness of the hard alloy; mixing the medium-grained WC powder with NbScN alloy powder and NbC alloy powder for batching is beneficial to jointly achieve the strengthening effect on the binder phase and improve the alloy strength under the surrounding distribution effect.

[0021] Preferably, the batch mixing mass ratio of the super-coarse-grained mixture and the medium-grained mixture is 9:1.

[0022] By adopting the above technical solutions, the ratio of ultrafine-grained WC to medium-grained WC is crucial for the properties of cemented carbide such as fracture toughness, wear resistance, and fatigue resistance. The inventor found through experiments that when the batch mixing mass ratio is 9:1, the cemented carbide can achieve the best comprehensive performance.

[0023] Preferably, the molding agent is polyethylene glycol.

[0024] Preferably, the NbScN alloy powder and NbC alloy powder need to be surface-modified with an alcoholamine compound. The surface modification method is: mixing NbScN powder and / or NbC powder, absolute ethanol, and diethanolamine according to a mass ratio of 1:(0.1 - 0.2):(0.001 - 0.005), ball-milling for 2 - 6 h, and drying under vacuum.

[0025] By adopting the above technical solutions, the addition amounts of NbScN alloy powder and NbC alloy powder in the cemented carbide are small, and it is easy to have uneven dispersion. By surface-modifying the NbScN alloy powder and NbC alloy powder, while refining the particle sizes of the NbScN alloy powder and NbC alloy powder, diethanolamine is coated on the surfaces of the NbScN alloy powder and NbC alloy powder, improving the compatibility, wettability, and dispersion effect of the NbScN alloy powder and NbC alloy powder with the polyethylene glycol molding agent, enhancing the dispersion uniformity of the NbScN alloy powder and NbC alloy powder, and contributing to further improving the comprehensive performance of the cemented carbide.

[0026] Preferably, in the preparation step of the ultrafine particle mixture, the wet-milling medium is absolute ethanol, the liquid-solid ratio is 180 - 230 ml / kg, and the ball-to-material ratio for wet-milling is 3:1 - 4:1.

[0027] Preferably, in the preparation step of the medium particle mixture, the wet-milling medium is absolute ethanol, the liquid-solid ratio is 200 - 300 ml / kg, and the ball-to-material ratio for wet-milling is 3.5:1 - 4.5:1.

[0028] By adopting the above technical solutions, by controlling the wet-milling parameters of each step, the ingredients are uniformly mixed, ensuring that the mixture has a better tap density.

[0029] Preferably, the batch mixing step is carried out in a double-cone mixer or a Y-type mixer.

[0030] Preferably, the pressing step is to press and form by a die pressing method.

[0031] In summary, the present application has the following beneficial effects:

[0032] 1. Since this application forms a better dense arrangement between particles by adding medium-grained tungsten carbide; medium-grained WC can partially dissolve in liquid Co, playing a role in strengthening the Co binder phase, improving the hardness, wear resistance and service life of the binder phase; at the same time, by optimizing the ratio of extra-coarse-grained WC to medium-grained WC, the cemented carbide is more superior in terms of fracture toughness, wear resistance and fatigue resistance.

[0033] 2. In this application, NbC and NbScN cooperate with each other, having a better solution strengthening effect on the Co binder phase, significantly improving the mechanical properties of the cemented carbide, increasing both the bending strength and fracture toughness, and to a certain extent improving the wettability between WC grains and the binder phase, inhibiting the excessive growth of grains, and improving the corrosion resistance and oxidation resistance of the binder phase to a certain extent; at the same time, combined with the grading of medium grains, the hardness of the alloy is improved together. Detailed implementation manners

[0034] To further help understand the technical solution of the present invention, the following provides several specific implementation examples to describe the technical solution of the present invention more specifically. All the described embodiments are only partial embodiments of the present invention, not all;

[0035] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments; and the reaction devices, monomer compounds, etc. involved in the following embodiments are all commercially available.

[0036] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments.

[0037] The following embodiments are further descriptions of the present invention, and the present invention is not limited thereto. Unless otherwise specified in the embodiments, the percentage content % is the mass percentage.

[0038] Embodiments

[0039] Embodiment 1

[0040] This embodiment discloses a mining WC-Co cemented carbide, and its preparation method is as follows:

[0041] Extra-coarse-grained WC powder and Co powder are mixed and proportioned according to a mass ratio of 0.8:0.2, and then 2 wt% of polyethylene glycol based on the total mass of the ingredients is added, and wet ball milling is carried out in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; after ball milling for 18 h, spray drying and granulation are carried out to obtain an extra-coarse-grained mixture;

[0042] Medium-grained WC powder and Co powder are mixed and proportioned according to a mass ratio of 0.72:0.28, and then 2 wt% of polyethylene glycol based on the total mass of the ingredients is added. Wet ball milling is carried out in a rolling ball mill, and the ball milling medium is anhydrous ethanol. The liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, and the ball-to-material ratio of ball milling is 4:1. After ball milling for 28 h, spray drying and granulation are carried out to obtain medium-grained mixed material;

[0043] The ultra-coarse-grained mixed material and the medium-grained mixed material are mixed in a double-cone mixer according to a mass ratio of 9:1 for 80 min, and then molded by die pressing under 120 MPa. The green compact is put into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sintered at 1400 °C, and then sintered in a low-pressure furnace. The sintering temperature is 1450 °C to obtain a WC-Co hard alloy for mining.

[0044] In this example, the Fess particle size of the ultra-coarse-grained WC powder is 15 μm, and the carbon content is 6.145 wt%; the Fess particle size of the medium-grained WC powder is 5.0 μm, and the carbon content is 6.15 wt%. The polyethylene glycol is PEG4000.

[0045] The WC-Co hard alloy for mining produced in this example is tested. The average grain size of medium-grained WC in the WC-Co hard alloy of this example is 1.8 μm, the average grain size of ultra-coarse-grained WC is 6.5 μm, the bending strength is 2600 MPa, and the Rockwell hardness HRA is 86.8.

[0046] Example 2

[0047] The difference between this example and Example 1 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0048] The ultra-coarse-grained WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder are mixed and proportioned according to a mass ratio of 0.8:0.2, and then 2 wt% of PEG4000 based on the total mass of the ingredients is added. Wet ball milling is carried out in a rolling ball mill, and the ball milling medium is anhydrous ethanol. The liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; after ball milling for 18 h, spray drying and granulation are carried out to obtain ultra-coarse-grained mixed material;

[0049] The medium-grained WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt% and Co powder are mixed and proportioned according to a mass ratio of 0.72:0.28, and then 2 wt% of PEG4000 based on the total mass of the ingredients is added. Wet ball milling is carried out in a rolling ball mill, and the ball milling medium is anhydrous ethanol. The liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, and the ball-to-material ratio of ball milling is 4:1. After ball milling for 28 h, spray drying and granulation are carried out to obtain medium-grained mixed material;

[0050] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 8.5:1.5 in a double-cone mixer for 80 min, then compact them at 120 MPa. Place the green compact in a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain the WC-Co hard alloy for mining.

[0051] Test the WC-Co hard alloy for mining produced in this example. The average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 2.0 μm, the average grain size of extra-coarse-grain WC is 6.9 μm, the flexural strength is 2520 MPa, and the Rockwell hardness HRA is 87.5.

[0052] Example 3

[0053] The difference between this example and Example 1 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0054] Mix and proportion the extra-coarse particle WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of PEG4000 based on the total mass of the mixture, and wet ball-mill in a rolling ball mill. The ball-milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid mixture is 200 ml / Kg, and the ball-to-material ratio for ball-milling is 3.5:1; ball-mill for 18 h, and granulate by spray drying to obtain the extra-coarse particle mixture;

[0055] Mix and proportion the medium particle WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt% and Co powder in a mass ratio of 0.72:0.28, then add 2 wt% of PEG4000 based on the total mass of the mixture, and wet ball-mill in a rolling ball mill. The ball-milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid mixture is 260 ml / Kg, and the ball-to-material ratio for ball-milling is 4:1. After ball-milling for 28 h, granulate by spray drying to obtain the medium particle mixture;

[0056] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 9.5:0.5 in a double-cone mixer for 80 min, then compact them at 120 MPa. Place the green compact in a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain the WC-Co hard alloy for mining.

[0057] Test the WC-Co hard alloy for mining produced in this example. The average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 1.6 μm, the average grain size of extra-coarse-grain WC is 6.4 μm, the flexural strength is 2740 MPa, and the Rockwell hardness HRA is 85.1.

[0058] Example 4

[0059] The difference between this example and Example 1 is only that the preparation method of the mining WC-Co cemented carbide is as follows:

[0060] Mix and proportion the ultra-coarse grain WC powder with a Fess particle size of 18.5 μm and a carbon content of 6.15 wt% and Co powder in a mass ratio of 0.7:0.3, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; ball mill for 14 h, spray drying and granulation to obtain an ultra-coarse grain mixture;

[0061] Mix and proportion the medium grain WC powder with a Fess particle size of 8.0 μm and a carbon content of 6.15 wt% and Co powder in a mass ratio of 0.7:0.3, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, the ball-to-material ratio of ball milling is 4:1, ball mill for 20 h, spray drying and granulation to obtain a medium grain mixture;

[0062] Mix and batch the ultra-coarse grain mixture and the medium grain mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then mold and press at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace. The sintering temperature is 1450 °C to obtain the mining WC-Co cemented carbide.

[0063] Detect the mining WC-Co cemented carbide produced in this example. The average grain size of medium grain WC in the mining WC-Co cemented carbide of this example is 3.0 μm, the average grain size of ultra-coarse grain WC is 8.6 μm, the flexural strength is 2550 MPa, and the Rockwell hardness HRA is 86.7.

[0064] Example 5

[0065] The difference between this example and Example 1 is only that the preparation method of the mining WC-Co cemented carbide is as follows:

[0066] Mix and proportion the ultra-coarse grain WC powder with a Fess particle size of 14 μm and a carbon content of 6.15 wt% and Co powder in a mass ratio of 0.85:0.15, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; ball mill for 20 h, spray drying and granulation to obtain an ultra-coarse grain mixture;

[0067] Medium-grained WC powder with a Fess particle size of 1.2 μm and a carbon content of 6.14 wt% was mixed with Co powder in a mass ratio of 0.85:0.15. Then, 2 wt% of polyethylene glycol based on the total mass of the ingredients was added, and wet ball milling was carried out in a rolling ball mill. The ball milling medium was absolute ethanol, the liquid-solid ratio of absolute ethanol to solid ingredients was 260 ml / Kg, the ball-to-material ratio of ball milling was 4:1, ball milling was carried out for 30 h, and then spray drying granulation was carried out to obtain medium-grained mixed materials;

[0068] The ultra-coarse-grained mixed materials and medium-grained mixed materials were mixed in a mass ratio of 9:1 in a double-cone mixer for 80 min, and then molded by die pressing at 120 MPa. The green compact was put into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sintered at 1400 °C, and then sintered in a low-pressure furnace at a sintering temperature of 1450 °C to obtain WC-Co hard alloy for mining.

[0069] The WC-Co hard alloy for mining produced in this example was tested, and the average grain size of medium-grained WC in the WC-Co hard alloy for mining in this example was 1.2 μm, the average grain size of ultra-coarse-grained WC was 6.2 μm, the flexural strength was 2580 MPa, and the Rockwell hardness HRA was 86.5.

[0070] Example 6

[0071] The difference between this example and Example 1 is only that the preparation method of WC-Co hard alloy for mining is as follows:

[0072] Ultra-coarse-grained WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% was mixed with Co powder in a mass ratio of 0.8:0.2. Then, 2 wt% of polyethylene glycol based on the total mass of the ingredients was added, and wet ball milling was carried out in a rolling ball mill. The ball milling medium was absolute ethanol, the liquid-solid ratio of absolute ethanol to solid ingredients was 200 ml / Kg, the ball-to-material ratio of ball milling was 3.5:1; ball milling was carried out for 18 h, and then spray drying granulation was carried out to obtain ultra-coarse-grained mixed materials;

[0073] Medium-grained WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, NbScN powder, and NbC powder were mixed in a mass ratio of 0.7:0.28:0.01:0.01. Then, 2 wt% of polyethylene glycol based on the total mass of the ingredients was added, and wet ball milling was carried out in a rolling ball mill. The ball milling medium was absolute ethanol, the liquid-solid ratio of absolute ethanol to solid ingredients was 260 ml / Kg, the ball-to-material ratio of ball milling was 4:1, ball milling was carried out for 28 h, and then spray drying granulation was carried out to obtain medium-grained mixed materials;

[0074] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 9:1 in a double-cone mixer for 80 minutes, then press and form at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain a WC-Co hard alloy for mining.

[0075] Test the WC-Co hard alloy for mining produced in this example. The average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 1.8 μm, the average grain size of extra-coarse-grain WC is 6.4 μm, the flexural strength is 2620 MPa, and the Rockwell hardness HRA is 86.8.

[0076] Example 7

[0077] The difference between this example and Example 1 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0078] Mix and proportion the extra-coarse particle WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of polyethylene glycol based on the total mass of the mixture, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid mixture is 200 ml / Kg, and the ball-to-material ratio for ball milling is 3.5:1; ball mill for 18 h, and spray dry and granulate to obtain an extra-coarse particle mixture;

[0079] Mix and proportion the medium particle WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, NbScN powder, and NbC powder in a mass ratio of 0.62:0.28:0.05:0.05, then add 2 wt% of polyethylene glycol based on the total mass of the mixture, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid mixture is 260 ml / Kg, and the ball-to-material ratio for ball milling is 4:1, ball mill for 28 h, and spray dry and granulate to obtain a medium particle mixture;

[0080] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 9:1 in a double-cone mixer for 80 minutes, then press and form at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain a WC-Co hard alloy for mining.

[0081] Test the WC-Co hard alloy for mining produced in this example. The average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 1.6 μm, the average grain size of extra-coarse-grain WC is 6.5 μm, the flexural strength is 2650 MPa, and the Rockwell hardness HRA is 87.0.

[0082] Example 8

[0083] The difference between this example and Example 1 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0084] Mix and proportion the ultra-coarse grain WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; ball mill for 18 h, and perform spray drying and granulation to obtain an ultra-coarse grain mixture;

[0085] Mix and proportion the medium grain WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, NbScN powder, and NbC powder in a mass ratio of 0.58:0.28:0.06:0.08, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, the ball-to-material ratio of ball milling is 4:1, ball mill for 28 h, and perform spray drying and granulation to obtain a medium grain mixture;

[0086] Mix and batch the ultra-coarse grain mixture and the medium grain mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then perform molding by die pressing at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace. The sintering temperature is 1450 °C to obtain the WC-Co hard alloy for mining.

[0087] Detect the WC-Co hard alloy for mining produced in this example. The average grain size of medium grain WC in the WC-Co hard alloy for mining in this example is 1.6 μm, the average grain size of ultra-coarse grain WC is 6.4 μm, the flexural strength is 2690 MPa, and the Rockwell hardness HRA is 87.2.

[0088] Example 9

[0089] The difference between this example and Example 1 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0090] Mix the ultra - coarse - grained WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients, and wet - ball - mill in a rolling ball - mill. The ball - milling medium is absolute ethanol, the liquid - to - solid ratio of absolute ethanol to solid ingredients is 200 ml / Kg, and the ball - to - material ratio for ball - milling is 3.5:1. Ball - mill for 18 h, and then spray - dry and granulate to obtain an ultra - coarse - grained mixture.

[0091] Mix the medium - grained WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, NbScN powder, and NbC powder in a mass ratio of 0.56:0.28:0.08:0.08. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients, and wet - ball - mill in a rolling ball - mill. The ball - milling medium is absolute ethanol, the liquid - to - solid ratio of absolute ethanol to solid ingredients is 260 ml / Kg, and the ball - to - material ratio for ball - milling is 4:1. Ball - mill for 28 h, and then spray - dry and granulate to obtain a medium - grained mixture.

[0092] Mix the ultra - coarse - grained mixture and the medium - grained mixture in a mass ratio of 9:1 in a double - cone mixer for 80 min, then press - mold at 120 MPa. Put the green compact into a dewaxing furnace for positive - pressure hydrogen to remove polyethylene glycol and pre - sinter at 1400 °C, and then sinter in a low - pressure furnace at a sintering temperature of 1450 °C to obtain a mining WC - Co cemented carbide.

[0093] Detect the mining WC - Co cemented carbide produced in this example. The average grain size of medium - grain WC in the mining WC - Co cemented carbide of this example is 1.6 μm, the average grain size of ultra - coarse - grain WC is 6.6 μm, the flexural strength is 2670 MPa, and the Rockwell hardness HRA is 86.8.

[0094] Example 10

[0095] The difference between this example and Example 1 is only that the preparation method of the mining WC - Co cemented carbide is as follows:

[0096] Mix the ultra - coarse - grained WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients, and wet - ball - mill in a rolling ball - mill. The ball - milling medium is absolute ethanol, the liquid - to - solid ratio of absolute ethanol to solid ingredients is 200 ml / Kg, and the ball - to - material ratio for ball - milling is 3.5:1. Ball - mill for 18 h, and then spray - dry and granulate to obtain an ultra - coarse - grained mixture.

[0097] Mix medium-grain WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, NbScN powder, and NbC powder according to a mass ratio of 0.52:0.28:0.1:0.1. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, the ball-to-material ratio for ball milling is 4:1, ball mill for 28 h, and then perform spray drying granulation to obtain a medium-grain mixture;

[0098] Mix the extra-coarse-grain mixture and the medium-grain mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then perform die pressing at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain a mining WC-Co cemented carbide.

[0099] Detect the mining WC-Co cemented carbide produced in this example. The average grain size of medium-grain WC in the mining WC-Co cemented carbide of this example is 1.6 μm, the average grain size of extra-coarse-grain WC is 6.6 μm, the transverse rupture strength is 2660 MPa, and the Rockwell hardness HRA is 86.4.

[0100] Example 11

[0101] The difference between this example and Example 8 is only that the preparation method of the mining WC-Co cemented carbide is as follows:

[0102] Mix extra-coarse-grain WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder according to a mass ratio of 0.8:0.2. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio for ball milling is 3.5:1; ball mill for 18 h, and then perform spray drying granulation to obtain an extra-coarse-grain mixture;

[0103] Mix medium-grain WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, and NbScN powder according to a mass ratio of 0.58:0.28:0.14. Then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, the ball-to-material ratio for ball milling is 4:1, ball mill for 28 h, and then perform spray drying granulation to obtain a medium-grain mixture;

[0104] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then press and form at 120 MPa. Place the green compact in a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain the WC-Co hard alloy for mining.

[0105] Test the WC-Co hard alloy for mining produced in this example, and it is obtained that the average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 1.8 μm, the average grain size of extra-coarse-grain WC is 6.5 μm, the flexural strength is 2610 MPa, and the Rockwell hardness HRA is 86.6.

[0106] Example 12

[0107] The difference between this example and Example 8 is only that the preparation method of the WC-Co hard alloy for mining is as follows:

[0108] Mix the extra-coarse particle WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio of ball milling is 3.5:1; ball mill for 18 h, and spray dry and granulate to obtain the extra-coarse particle mixture;

[0109] Mix the medium particle WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, and NbC powder in a mass ratio of 0.58:0.28:0.14, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and wet ball mill in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, and the ball-to-material ratio of ball milling is 4:1, ball mill for 28 h, and spray dry and granulate to obtain the medium particle mixture;

[0110] Mix the extra-coarse particle mixture and medium particle mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then press and form at 120 MPa. Place the green compact in a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain the WC-Co hard alloy for mining.

[0111] Test the WC-Co hard alloy for mining produced in this example, and it is obtained that the average grain size of medium-grain WC in the WC-Co hard alloy for mining in this example is 1.8 μm, the average grain size of extra-coarse-grain WC is 6.4 μm, the flexural strength is 2650 MPa, and the Rockwell hardness HRA is 87.0.

[0112] Example 13

[0113] The difference between this example and Example 8 is only that the preparation method of the mining WC-Co cemented carbide is as follows:

[0114] Mix and proportion the ultra-coarse WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio for ball milling is 3.5:1; ball mill for 18 h, and perform spray drying and granulation to obtain an ultra-coarse particle mixture;

[0115] Put NbScN powder, anhydrous ethanol, and diethanolamine into the ball mill in a mass ratio of 1:0.2:0.001, with a ball-to-material ratio of 1:1, ball mill for 3 h, and perform vacuum drying to obtain modified NbScN powder; put NbC powder, anhydrous ethanol, and diethanolamine into the ball mill in a mass ratio of 1:0.2:0.001, with a ball-to-material ratio of 1:1, ball mill for 4 h, and perform vacuum drying to obtain modified NbC powder;

[0116] Mix and proportion medium-grained WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, modified NbScN powder, and modified NbC powder in a mass ratio of 0.58:0.28:0.06:0.08, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, and the ball-to-material ratio for ball milling is 4:1, ball mill for 28 h, and perform spray drying and granulation to obtain a medium-grained particle mixture;

[0117] Mix and batch the ultra-coarse particle mixture and the medium-grained particle mixture in a mass ratio of 9:1 in a double-cone mixer for 80 min, then perform molding by die pressing at 120 MPa. Put the green compact into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sinter at 1400 °C, and then sinter in a low-pressure furnace at a sintering temperature of 1450 °C to obtain the mining WC-Co cemented carbide.

[0118] Detect the mining WC-Co cemented carbide produced in this example, and obtain that the average grain size of medium-grained WC in the mining WC-Co cemented carbide of this example is 1.6 μm, the average grain size of ultra-coarse-grained WC is 6.5 μm, the flexural strength is 2700 MPa, and the Rockwell hardness HRA is 87.3.

[0119] Example 14

[0120] The difference between this example and Example 11 is only that the preparation method of the mining WC-Co cemented carbide is as follows:

[0121] Mix the ultra - coarse - grained WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball - milling in a rolling ball - mill. The ball - milling medium is anhydrous ethanol, the liquid - to - solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball - to - material ratio for ball - milling is 3.5:1; ball - mill for 18 h, and then perform spray drying and granulation to obtain an ultra - coarse - grained mixture.

[0122] Put NbScN powder, anhydrous ethanol, and diethanolamine into a ball - mill in a mass ratio of 1:0.2:0.003, with a ball - to - material ratio of 1:1, ball - mill for 3 h, and then perform vacuum drying to obtain modified NbScN powder; put NbC powder, anhydrous ethanol, and diethanolamine into a ball - mill in a mass ratio of 1:0.2:0.005, with a ball - to - material ratio of 1:1, ball - mill for 4 h, and then perform vacuum drying to obtain modified NbC powder.

[0123] Mix medium - grained WC powder with a Fess particle size of 5.0 μm and a carbon content of 6.15 wt%, Co powder, modified NbScN powder, and modified NbC powder in a mass ratio of 0.58:0.28:0.06:0.08, then add 2 wt% of polyethylene glycol based on the total mass of the ingredients, and perform wet ball - milling in a rolling ball - mill. The ball - milling medium is anhydrous ethanol, the liquid - to - solid ratio of anhydrous ethanol to solid ingredients is 260 ml / Kg, and the ball - to - material ratio for ball - milling is 4:1, ball - mill for 28 h, and then perform spray drying and granulation to obtain a medium - grained mixture.

[0124] Mix the ultra - coarse - grained mixture and the medium - grained mixture in a mass ratio of 9:1 in a double - cone mixer for 80 min, then perform die - pressing at 120 MPa. Put the green compact into a dewaxing furnace for positive - pressure hydrogen to remove polyethylene glycol and pre - sinter at 1400 °C, and then sinter in a low - pressure furnace at a sintering temperature of 1450 °C to obtain a mining WC - Co cemented carbide.

[0125] Detect the mining WC - Co cemented carbide produced in this example. The average grain size of medium - grain WC in the mining WC - Co cemented carbide of this example is 1.5 μm, the average grain size of ultra - coarse - grain WC is 6.5 μm, the flexural strength is 2720 MPa, and the Rockwell hardness HRA is 87.4.

[0126] Comparative example

[0127] The difference between this comparative example and Example 1 is only that the mining WC - Co cemented carbide is prepared by the following method:

[0128] Mix super-coarse particle WC powder with a Fess particle size of 15 μm and a carbon content of 6.145 wt% and Co powder in a mass ratio of 0.8:0.2, then add polyethylene glycol accounting for 2 wt% of the total mass of the ingredients, and perform wet ball milling in a rolling ball mill. The ball milling medium is anhydrous ethanol, the liquid-solid ratio of anhydrous ethanol to solid ingredients is 200 ml / Kg, and the ball-to-material ratio for ball milling is 3.5:1; after ball milling for 18 h, spray drying and granulation are carried out, then molding is performed by die pressing at 120 MPa. The green compact is put into a dewaxing furnace for positive-pressure hydrogen to remove polyethylene glycol and pre-sintering at 1400 °C, and then sintering is carried out in a low-pressure furnace at a sintering temperature of 1450 °C to obtain a WC-Co hard alloy for mining.

[0129] The WC-Co hard alloy for mining produced in this comparative example was tested, and the average grain size of the coarse-grained WC in the WC-Co hard alloy for mining in this comparative example was 11.5 μm, the flexural strength was 2780 MPa, and the Rockwell hardness HRA was 80.6.

[0130] Combined with Examples 1-14, it can be seen that referring to the formula and method disclosed in this application, the comprehensive performance of the hard alloy has been greatly improved, with excellent hardness and flexural strength, good wear resistance, and high toughness, which can meet the application requirements of hard alloys for mining.

[0131] Combined with Examples 1-3 and the comparative example, it can be seen that by using a ratio of medium-particle WC to super-coarse particle WC, the hardness and toughness of the WC-Co hard alloy are improved, and the batch mixing ratio of the super-coarse particle mixture and the medium-particle mixture has a certain influence on the comprehensive performance of the hard alloy. When the batch mixing ratio is 9:1, the comprehensive performance of the hard alloy is the best.

[0132] Combined with Example 1 and Examples 6-12, it can be seen that by simultaneously adding NbScN and NbC, and their interaction promotes the further improvement of the hardness and toughness of the hard alloy, and the alloy performance reaches the optimum when 0.6 wt% NbScN and 0.8 wt% NbC are added.

[0133] Combined with Examples 8, 13, and 14, it can be seen that by surface modification of NbScN powder and NbC powder, the hardness and toughness of the hard alloy are further improved. This may be because the surface coating modification with diethanolamine improves the dispersion uniformity of NbScN powder and NbC powder, and further promotes the interfacial segregation and solid solution strengthening effects of NbScN powder and NbC powder.

[0134] This specific embodiment is only an interpretation of this application, and it does not limit this application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A WC-Co hard alloy for mining, characterized in that, It includes Co with a mass ratio of 15 - 30%, NbScN with 0.5 - 1.0%, NbC with 0.5 - 1.0%, and the balance is the hard phase WC; The hard phase WC includes extra - coarse - grained WC with an average grain size of 6.0 - 9.0 μm and medium - grained WC with an average grain size of 1.0 - 3.0 μm; The raw materials for preparing the WC - Co hard alloy for mining include a batch - mixed extra - coarse - grained mixture and medium - grained mixture with a mass ratio of (85:15)-(95:5). The raw materials of the extra - coarse - grained mixture include extra - coarse - grained WC powder and Co powder, and the raw materials of the medium - grained mixture include medium - grained WC powder, Co powder, NbScN alloy powder, and NbC alloy powder; The Fess particle size of the extra - coarse - grained WC powder is 13 - 20 μm; the Fess particle size of the medium - grained WC powder is 2 - 8 μm; The NbScN alloy powder and NbC alloy powder need to be surface - modified by an alcohol - amine compound. The surface - modification method is: mixing NbScN powder and / or NbC powder, absolute ethanol, and diethanolamine in a mass ratio of 1:(0.1 - 0.2):(0.001 - 0.005), ball - milling for 2 - 6 h, and then vacuum - drying to obtain.

2. A preparation method of the WC-Co hard alloy for mining as described in claim 1, characterized in that, It includes the following steps: According to the ratio, mix and proportion the extra - coarse - grained WC powder and Co powder, then add a molding agent accounting for 1.5 - 2.5% of the total weight of the mixture, mix and wet - mill for 14 - 20 h, and then granulate by spray - drying to obtain the extra - coarse - grained mixture; the Fess particle size of the extra - coarse - grained WC powder is 13 - 20 μm; According to the ratio, mix and proportion the medium - grained WC powder, Co powder, NbScN alloy powder, and NbC alloy powder, then add a molding agent accounting for 1.5 - 2.5% of the total weight of the mixture, mix and wet - mill for 20 - 30 h, and then granulate by spray - drying to obtain the medium - grained mixture; the Fess particle size of the medium - grained WC powder is 2 - 8 μm; Mix and batch the extra - coarse - grained mixture and medium - grained mixture in a mass ratio of (85:15)-(95:5) for 40 - 80 min, press into shape, vacuum - sinter to remove the molding agent, and then perform low - pressure hot isostatic pressing sintering at 1420 - 1450 °C to obtain the WC - Co hard alloy for mining.

3. The preparation method of the WC-Co hard alloy for mining according to claim 2, characterized in that, The mass ratio of the batch of the extra - coarse - grained mixture and medium - grained mixture is 9:

1.

4. The preparation method of the WC-Co hard alloy for mining according to claim 2, characterized in that, The molding agent is polyethylene glycol.

5. The preparation method of the WC-Co hard alloy for mining according to claim 2, characterized in that, In the preparation step of the extra - coarse - grained mixture, the wet - milling medium is absolute ethanol, the liquid - solid ratio is 180 - 230 ml / kg, and the ball - to - material ratio of wet - milling is 3:1 - 4:

1.

6. The preparation method of the WC-Co hard alloy for mining according to claim 2, characterized in that, In the preparation step of the medium - grained mixture, the wet - milling medium is absolute ethanol, the liquid - solid ratio is 200 - 300 ml / kg, and the ball - to - material ratio of wet - milling is 3.5:1 - 4.5:

1.

7. The preparation method of the WC-Co hard alloy for mine use according to claim 2, characterized in that, The batch - mixing step is carried out in a double - cone mixer or a Y - type mixer.

8. The preparation method of the WC-Co hard alloy for mining according to claim 2, characterized in that, The pressing step is to press into shape by a die - pressing method.