Ultra-coarse tungsten carbide powder, ultra-coarse grain hard alloy and preparation method thereof

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to ultra-coarse tungsten carbide powder, ultra-coarse grain hard alloy and a preparation method of the ultra-coarse tungsten carbide powder and the ultra-coarse grain hard alloy. The carbon-cobalt composite powder and tungsten powder are mixed to prepare carbon-cobalt-tungsten composite powder; sintering the carbon-cobalt-tungsten composite powder to prepare a WC agglomerated block; and the WC agglomerated blocks are subjected to ball-milling crushing and grading, and the ultra-coarse tungsten carbide powder is prepared. The cobalt-based powder is doped to promote the development and carbonization of the ultra-coarse single crystal tungsten carbide to prepare the ultra-coarse tungsten carbide powder; the FSSS particle size of the ultra-coarse tungsten carbide powder in the production state is larger than 31.5 microns, carbonization is complete, grain development is complete, agglomerated pseudo particles are few, the WC grain size of the ultra-coarse grain hard alloy prepared through the ultra-coarse grain hard alloy powder is larger than 7.5 microns, the organization structure is uniform, and the local decarburization phenomenon does not exist.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and specifically relates to an ultra-coarse tungsten carbide powder, an ultra-coarse grain cemented carbide and a preparation method thereof. Background Art

[0002] Ultra-coarse tungsten carbide grain cemented carbide has the advantages of good strength and toughness, and is widely used in oil drilling, mining tools, stamping dies, hard surface materials and other fields. High-quality ultra-coarse tungsten carbide powder is the key raw material for the preparation of ultra-coarse grain cemented carbide, and the grain size of tungsten carbide powder directly affects the performance of cemented carbide. The FSSS particle size of ultra-coarse tungsten carbide produced by wet hydrogen reduction-high temperature carburization, high temperature low hydrogen slow boat reduction-high temperature carburization, doping with alkali metal elements such as Na / Li to promote growth can reach more than 30μm, but the tungsten carbide powder prepared by these traditional methods has too many pseudo particles, incomplete development of ultra-coarse single crystal tungsten carbide, resulting in low FSSS particle size in the ground state of the product, and incomplete carbonization inside the grains. At the same time, the ultra-coarse cemented carbide prepared by ultra-coarse tungsten carbide powder prepared by traditional methods has the problems of small WC grain size and local decarburization of the alloy. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide an ultra-coarse tungsten carbide powder, an ultra-coarse grain cemented carbide and a preparation method thereof.

[0004] According to one aspect of the present invention, the present invention provides the following technical solution: A method for preparing ultra-coarse tungsten carbide powder comprises the following steps: S1, mixing cobalt oxyhydroxide powder and carbon black to prepare carbon-cobalt composite powder; S2, mixing carbon-cobalt composite powder and tungsten powder to prepare carbon-cobalt-tungsten composite powder; S3, sintering the carbon-cobalt-tungsten composite powder to obtain a WC agglomerate; S4. The WC agglomerates are crushed and classified by ball milling to prepare ultra-coarse tungsten carbide powder.

[0005] As a preferred embodiment of the method for preparing ultra-coarse tungsten carbide powder according to the present invention, wherein: in step S1, the mass ratio of cobalt oxyhydroxide powder to carbon black is 1: (95-110), and the BET of cobalt oxyhydroxide is 42-55m 2 / g, the BET of carbon black is 12.5~17.0m 2 / g.

[0006] As a preferred embodiment of the method for preparing ultra-coarse tungsten carbide powder described in the present invention, wherein: in the step S2, the mass ratio of carbon-cobalt composite powder to tungsten powder is (6.14~6.18): (93.82~93.86), and the ground FSSS particle size of the tungsten powder is greater than 15μm and span is less than 0.95.

[0007] As a preferred embodiment of the method for preparing ultra-coarse tungsten carbide powder described in the present invention, in step S3, the sintering process is: keeping warm at 1100-1200°C for 1-2 hours, keeping warm at 1350-1380°C for 4-5 hours, and keeping warm at 2130-2250°C for 6-10 hours.

[0008] As a preferred embodiment of the method for preparing ultra-coarse tungsten carbide powder described in the present invention, in step S4, the crushing time is 5-15 minutes, and the classification frequency is 25-35 Hz.

[0009] According to another aspect of the present invention, the present invention provides the following technical solution: An ultra-coarse tungsten carbide powder is prepared by the above-mentioned method for preparing the ultra-coarse tungsten carbide powder. The ultra-coarse tungsten carbide powder has a production state FSSS particle size of >31.5 μm, is completely carbonized, has completely developed grains, and has few agglomerated pseudo particles.

[0010] According to another aspect of the present invention, the present invention provides the following technical solution: A method for preparing an ultra-coarse-grained cemented carbide comprises: adopting a conventional wet ball milling-spray granulation-pressing-sintering preparation method, using the ultra-coarse tungsten carbide powder and cobalt powder as raw materials, to prepare an ultra-coarse-grained cemented carbide; wherein the cobalt content is 5-20wt%, the ball milling time is 1.5-4h, the ball-to-material ratio is (1-3):1, and the sintering temperature is 1450-1490°C.

[0011] According to another aspect of the present invention, the present invention provides the following technical solution: An ultra-coarse-grained cemented carbide is prepared by the above-mentioned method for preparing ultra-coarse-grained cemented carbide. The WC grain size of the ultra-coarse-grained cemented carbide is greater than 7.5 μm, and the microstructure is uniform without the phenomenon of local decarburization.

[0012] The beneficial effects of the present invention are as follows: The present invention proposes an ultra-coarse tungsten carbide powder, an ultra-coarse grain cemented carbide and a preparation method thereof, wherein cobalt oxyhydroxide powder is mixed with carbon black to prepare carbon-cobalt composite powder; carbon-cobalt composite powder is mixed with tungsten powder to prepare carbon-cobalt-tungsten composite powder; carbon-cobalt-tungsten composite powder is sintered to prepare WC agglomerates; WC agglomerates are ball-milled and graded to prepare ultra-coarse tungsten carbide powder. The present invention promotes the development and carburization of ultra-coarse single crystal tungsten carbide by doping with cobalt-based powder to prepare ultra-coarse tungsten carbide; the ultra-coarse tungsten carbide powder has a production state FSSS particle size of >31.5μm, and its carburization is complete, the grains are fully developed, and there are few agglomerated pseudo particles. The WC grain size of the ultra-coarse grain cemented carbide prepared by using the ultra-coarse tungsten carbide powder is >7.5μm, and the organizational structure is uniform, and there is no local decarburization phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0014] Figure 1 The metallographic image of the ultra-coarse tungsten carbide powder prepared in Example 1 of the present invention; Figure 2 The metallographic image of the ultra-coarse-grained cemented carbide prepared in Example 1 of the present invention; Figure 3 The metallographic image of the cemented carbide prepared in Comparative Example 6; Figure 4 The metallographic image of the tungsten carbide powder prepared in Comparative Example 9; Figure 5 This is the metallographic image of the cemented carbide prepared in Comparative Example 9.

[0015] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0016] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides an ultra-coarse tungsten carbide powder, an ultra-coarse grain cemented carbide and a preparation method thereof, which have the following advantages: (1) The present invention makes full use of the high specific surface area of ​​cobalt oxyhydroxide and makes the cobalt element evenly distributed by highly mixing it with carbon black, thus avoiding agglomeration and segregation, and providing a basis for the preparation of tungsten carbide; (2) The present invention utilizes uniformly dispersed cobalt hydroxide oxide to reduce and generate cobalt at the front end of sintering, thereby promoting the carburization of tungsten powder, allowing tungsten carbide to develop completely, and providing a basis for the coarsening of tungsten carbide; (3) The present invention achieves matching of the specific surface areas of cobalt oxyhydroxide powder and carbon black. The BET values ​​of the two within the scope of the present invention have good miscibility. Too large or too small a value will cause agglomeration and uneven dispersion. Mixing with the corresponding specific surface areas can effectively avoid electrostatic agglomeration of particles due to too large a specific surface area and avoid uneven distribution of small particles due to too small a specific surface area. (4) The present invention utilizes the characteristic of cobalt to promote the growth and complete development of tungsten carbide, and the prepared cemented carbide WC has coarse grains and better structural uniformity.

[0018] According to one aspect of the present invention, the present invention provides the following technical solution: A method for preparing ultra-coarse tungsten carbide powder comprises the following steps: S1, mixing cobalt oxyhydroxide powder and carbon black in a high-energy plowshare mixer to prepare a carbon-cobalt composite powder; S2, mixing carbon-cobalt composite powder and tungsten powder in a high-energy plowshare mixer to prepare carbon-cobalt-tungsten composite powder; S3, placing carbon-cobalt-tungsten composite powder in a graphite boat for medium frequency sintering to prepare WC agglomerates; S4. The WC agglomerates are crushed and classified by ball milling to prepare ultra-coarse tungsten carbide powder.

[0019] Preferably, in step S1, the mass ratio of cobalt oxyhydroxide powder to carbon black is 1:(95-110), and the BET of cobalt oxyhydroxide is 42-55 m 2 / g, the BET of carbon black is 12.5~17.0m 2 / g.

[0020] Preferably, in step S2, the mass ratio of carbon-cobalt composite powder to tungsten powder is (6.14-6.18): (93.82-93.86), and the ground FSSS particle size of the tungsten powder is >15 μm and span is <0.95.

[0021] Preferably, in step S3, the sintering process is: keeping warm at 1100-1200°C for 1-2 hours, keeping warm at 1350-1380°C for 4-5 hours, and keeping warm at 2130-2250°C for 6-10 hours.

[0022] Preferably, in step S4, the crushing time is 5-15 min and the classification frequency is 25-35 Hz.

[0023] According to another aspect of the present invention, the present invention provides the following technical solution: An ultra-coarse tungsten carbide powder is prepared by the above-mentioned method for preparing the ultra-coarse tungsten carbide powder. The ultra-coarse tungsten carbide powder has a production state FSSS particle size of >31.5 μm, is completely carbonized, has completely developed grains, and has few agglomerated pseudo particles.

[0024] According to another aspect of the present invention, the present invention provides the following technical solution: A method for preparing an ultra-coarse-grained cemented carbide comprises: adopting a conventional wet ball milling-spray granulation-pressing-sintering preparation method, using the ultra-coarse tungsten carbide powder and cobalt powder as raw materials, to prepare an ultra-coarse-grained cemented carbide; wherein the cobalt content is 5-20wt%, the ball milling time is 1.5-4h, the ball-to-material ratio is (1-3):1, and the sintering temperature is 1450-1490°C.

[0025] According to another aspect of the present invention, the present invention provides the following technical solution: An ultra-coarse-grained cemented carbide is prepared by the above-mentioned method for preparing ultra-coarse-grained cemented carbide. The WC grain size of the ultra-coarse-grained cemented carbide is greater than 7.5 μm, and the microstructure is uniform without the phenomenon of local decarburization.

[0026] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0027] Example 1 A method for preparing ultra-coarse tungsten carbide powder comprises the following steps: S1. Cobalt oxyhydroxide powder and carbon black are placed in a high-energy plowshare mixer and mixed to prepare carbon-cobalt composite powder; wherein the mass ratio of cobalt oxyhydroxide to carbon black is 1:103, and the BET of cobalt oxyhydroxide is 48.5m 2 / g, the BET of carbon black is 15.7m 2 / g.

[0028] S2. Place carbon-cobalt composite powder and tungsten powder in a high-energy plowshare mixer and mix them to prepare carbon-cobalt-tungsten composite powder; wherein the mass ratio of carbon-cobalt composite powder to tungsten powder is 6.16:93.84, and the ground FSSS particle size of the tungsten powder is 16.2 μm and the span is 0.91.

[0029] S3. Place carbon-cobalt-tungsten composite powder in a graphite boat for medium frequency sintering to prepare WC agglomerates; the sintering process is: keep warm at 1150°C for 1.5h, keep warm at 1365°C for 4.5h, and keep warm at 2200°C for 8h.

[0030] S4, the WC agglomerates were crushed and classified by ball milling, the crushing time was 10min, the classification frequency was 30Hz, and the ultra-coarse tungsten carbide powder (such as Figure 1 As shown in the figure, the particle size of the produced FSSS is 32.3μm, with complete carbonization, complete grain development, and few agglomerated pseudo particles.

[0031] The ultra-coarse tungsten carbide powder and cobalt powder obtained in step S4 are prepared by a conventional wet ball milling-spray granulation-pressing-sintering preparation method to obtain an ultra-coarse grain cemented carbide (such as Figure 2 The cobalt content is 10wt%, the ball milling time is 3h, the ball-to-material ratio is 2:1, and the sintering temperature is 1470℃. The WC grain size of the prepared ultra-coarse cemented carbide is 8.2μm and the microstructure is uniform, without local decarburization.

[0032] Example 2 A method for preparing ultra-coarse tungsten carbide powder comprises the following steps: S1. Cobalt oxyhydroxide powder and carbon black are placed in a high-energy plowshare mixer and mixed to prepare carbon-cobalt composite powder; wherein the mass ratio of cobalt oxyhydroxide to carbon black is 1:95, and the BET of cobalt oxyhydroxide is 42.4 m 2 / g, the BET of carbon black is 16.7m 2 / g.

[0033] S2. Place carbon-cobalt composite powder and tungsten powder in a high-energy plowshare mixer and mix them to prepare carbon-cobalt-tungsten composite powder; wherein the mass ratio of carbon-cobalt composite powder to tungsten powder is 6.14:93.86, and the ground FSSS particle size of the tungsten powder is 17.5 μm and the span is 0.94.

[0034] S3. Place the carbon-cobalt-tungsten composite powder in a graphite boat for medium-frequency sintering to prepare WC agglomerates; the sintering process is: keep warm at 1200°C for 1 hour, keep warm at 1350°C for 5 hours, and keep warm at 2250°C for 6 hours.

[0035] S4. The WC agglomerates are crushed and graded by ball milling. The crushing time is 15 minutes and the grading frequency is 35 Hz. Ultra-coarse tungsten carbide powder is prepared. The FSSS particle size of the production state is 33.5 μm. The powder is completely carbonized, the grains are fully developed, and there are few pseudo-agglomerated particles.

[0036] The ultra-coarse tungsten carbide powder and cobalt powder obtained in step S4 were prepared into ultra-coarse grained cemented carbide by conventional wet ball milling-spray granulation-pressing-sintering preparation method; wherein the cobalt content was 20wt%, the ball milling time was 4h, the ball-to-material ratio was 1:1, and the sintering temperature was 1450°C. The WC grain size of the prepared ultra-coarse cemented carbide was 8.4μm and the microstructure was uniform without local decarburization.

[0037] Example 3 A method for preparing ultra-coarse tungsten carbide powder comprises the following steps: S1. Cobalt oxyhydroxide powder and carbon black are placed in a high-energy plowshare mixer and mixed to prepare carbon-cobalt composite powder; wherein the mass ratio of cobalt oxyhydroxide to carbon black is 1:110, and the BET of cobalt oxyhydroxide is 54.6 m 2 / g, the BET of carbon black is 12.7m 2 / g.

[0038] S2. Place carbon-cobalt composite powder and tungsten powder in a high-energy plowshare mixer and mix them to prepare carbon-cobalt-tungsten composite powder; wherein the mass ratio of carbon-cobalt composite powder to tungsten powder is 6.18:93.82, and the ground FSSS particle size of the tungsten powder is 18.7 μm and the span is 0.93.

[0039] S3. Place carbon-cobalt-tungsten composite powder in a graphite boat for medium frequency sintering to prepare WC agglomerates; the sintering process is: keep warm at 1100°C for 2h, keep warm at 1380°C for 4h, and keep warm at 2230°C for 8h.

[0040] S4. The WC agglomerates are crushed and graded by ball milling. The crushing time is 15 minutes and the grading frequency is 25 Hz. Ultra-coarse tungsten carbide powder is prepared. The FSSS particle size of the production state is 35.2 μm. The powder is completely carbonized, the grains are fully developed, and there are few pseudo-agglomerated particles.

[0041] The ultra-coarse tungsten carbide powder and cobalt powder obtained in step S4 were prepared into ultra-coarse grain cemented carbide by conventional wet ball milling-spray granulation-pressing-sintering preparation method; wherein the cobalt content was 5wt%, the ball milling time was 1.5h, the ball-to-material ratio was 2:1, and the sintering temperature was 1490°C. The WC grain size of the prepared ultra-coarse cemented carbide was 8.2μm and the microstructure was uniform without local decarburization.

[0042] Comparative Example 1 The difference from Example 1 is that the BET of cobalt oxyhydroxide is 28.6 m 2 / g.

[0043] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 32.9 μm in the production state, and some tungsten carbide grains are not completely carburized, and W2C phase appears. The prepared cemented carbide shows the phenomenon of local decarburization, which is local E04.

[0044] Comparative Example 2 The difference from Example 1 is that the BET of cobalt oxyhydroxide is 63.9 m 2 / g.

[0045] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 33.5 μm, W2C phase appears in the center of the tungsten carbide grains, and η phase appears in the prepared cemented carbide, and the evaluation grade is E02.

[0046] Comparative Example 3 The difference from Example 1 is that the BET of carbon black is 20.4 m 2 / g.

[0047] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 33.9 μm in the production state, and some tungsten carbide grains are not completely carburized, and W2C phase appears. The prepared cemented carbide shows the phenomenon of local decarburization, which is local E02.

[0048] Comparative Example 4 The difference from Example 1 is that the BET of carbon black is 10.7 m 2 / g.

[0049] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 32.8 μm in the production state, and some tungsten carbide grains are not completely carburized, and W2C phase appears. The prepared cemented carbide shows the phenomenon of local decarburization, which is local E04.

[0050] Comparative Example 5 The difference from Example 1 is that the ground FSSS particle size of the tungsten powder is 13 μm.

[0051] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 28.5 μm, the grain size of the alloy WC is 5.6 μm, the organizational structure is uniform, and there is no local decarburization phenomenon.

[0052] Comparative Example 6 The difference from Example 1 is that the span of the tungsten powder is 1.10.

[0053] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 30.8μm, the grain size of the alloy WC is 6.5μm, the organizational structure is uniform, and there is no local decarburization phenomenon (such as Figure 3 As shown, the grains are small).

[0054] Comparative Example 7 The difference from Example 1 is that the sintering process is: keeping at 1365° C. for 4.5 hours and keeping at 2200° C. for 8 hours.

[0055] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 30.5 μm in the production state, and some tungsten carbide grains are not completely carburized, and W2C phase appears, and the prepared cemented carbide has a local decarburization phenomenon.

[0056] Comparative Example 8 The difference from Example 1 is that the sintering process is: keeping at 1150° C. for 1.5 hours and keeping at 2200° C. for 8 hours.

[0057] The FSSS particle size of the tungsten carbide powder obtained in this comparative example is 31.0 μm in the production state, and some tungsten carbide grains are not completely carburized, and W2C phase appears, and the prepared cemented carbide has a local decarburization phenomenon.

[0058] Comparative Example 9 The difference from Example 1 is that commercially available tungsten carbide powder with a grade of ZWC300 (such as Figure 4 As shown, there are false particles), the FSSS particle size is 32.5μm.

[0059] The hard alloy (such as Figure 5 As shown, the black part is local decarburization) the grain size is 6.4μm, and local carburization occurs.

[0060] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing ultra-coarse tungsten carbide powder, characterized in that: The steps include: S1, mixing cobalt oxyhydroxide powder and carbon black to prepare carbon-cobalt composite powder; S2, mixing carbon-cobalt composite powder and tungsten powder to prepare carbon-cobalt-tungsten composite powder; S3, sintering the carbon-cobalt-tungsten composite powder to obtain a WC agglomerate; S4. The WC agglomerates are crushed and classified by ball milling to prepare ultra-coarse tungsten carbide powder.

2. The method for preparing ultra-coarse tungsten carbide powder according to claim 1, characterized in that: In step S1, the mass ratio of cobalt oxyhydroxide powder to carbon black is 1:(95-110), and the BET of cobalt oxyhydroxide is 42-55 m 2 / g, the BET of carbon black is 12.5~17.0m 2 / g.

3. The method for preparing ultra-coarse tungsten carbide powder according to claim 1, characterized in that: In the step S2, the mass ratio of carbon-cobalt composite powder to tungsten powder is (6.14-6.18): (93.82-93.86), and the ground FSSS particle size of the tungsten powder is greater than 15 μm and span is less than 0.

95.

4. The method for preparing ultra-coarse tungsten carbide powder according to claim 1, characterized in that: In step S3, the sintering process is: keeping warm at 1100-1200° C. for 1-2 hours, keeping warm at 1350-1380° C. for 4-5 hours, and keeping warm at 2130-2250° C. for 6-10 hours.

5. The method for preparing ultra-coarse tungsten carbide powder according to claim 1, characterized in that: In step S4, the crushing time is 5-15 minutes, and the classification frequency is 25-35 Hz.

6. An ultra-coarse tungsten carbide powder, characterized in that: The ultra-coarse tungsten carbide powder is prepared by the preparation method of any one of claims 1 to 5, wherein the ultra-coarse tungsten carbide powder has a production state FSSS particle size of >31.5 μm, is completely carbonized, and has completely developed grains.

7. A method for preparing ultra-coarse-grained cemented carbide, characterized in that: include: The ultra-coarse grain cemented carbide is prepared by a wet ball milling-spray granulation-pressing-sintering preparation method, using the ultra-coarse tungsten carbide powder and cobalt powder described in claim 6 as raw materials.

8. An ultra-coarse-grained cemented carbide, characterized in that: The ultra-coarse-grained cemented carbide is prepared by the preparation method of the ultra-coarse-grained cemented carbide according to claim 7, wherein the WC grain size of the ultra-coarse-grained cemented carbide is greater than 7.5 μm, and the microstructure is uniform without the phenomenon of local decarburization.

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