A super-coarse tungsten carbide powder, super-coarse grained cemented carbide and a preparation method thereof

Abstract

The present 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, wherein cobalt oxyhydroxide powder is mixed with carbon black to prepare a carbon-cobalt composite powder; the carbon-cobalt composite powder is mixed with tungsten powder to prepare a carbon-cobalt-tungsten composite powder; the carbon-cobalt-tungsten composite powder is sintered to prepare a WC agglomerate; the WC agglomerate is ball-milled and graded to prepare an 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 an ultra-coarse tungsten carbide powder; 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, and 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.

Description

Technical Field

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

[0002] Ultra-coarse grain tungsten carbide cemented carbide has advantages such as good strength and toughness, and is widely used in fields such as oil drilling and production, geological and mining tools, stamping dies, hard-facing materials, etc. High-quality ultra-coarse tungsten carbide powder is the key raw material for preparing 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 the as-produced ultra-coarse tungsten carbide prepared by methods such as wet hydrogen reduction-high temperature carbonization, high temperature low hydrogen slow pusher reduction-high temperature carbonization, doping with alkali metal elements such as Na / Li to promote growth, etc. can reach more than 30 μm. However, the tungsten carbide powder prepared by these traditional methods has problems such as too many pseudo-particles, incomplete development of ultra-coarse single crystal tungsten carbide resulting in a 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 from the ultra-coarse tungsten carbide powder prepared by the traditional method has problems such as a relatively small WC grain size and local decarburization of the alloy. Summary of the Invention

[0003] To solve the problems existing in the prior art, the main object 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 following technical solution is provided:

[0005] A preparation method of an ultra-coarse tungsten carbide powder, comprising the following steps:

[0006] S1. Mix cobalt oxyhydroxide powder and carbon black to obtain a carbon-cobalt composite powder;

[0007] S2. Mix the carbon-cobalt composite powder and tungsten powder to obtain a carbon-cobalt-tungsten composite powder;

[0008] S3. Sinter the carbon-cobalt-tungsten composite powder to obtain a WC agglomerate;

[0009] S4. Ball mill and classify the WC agglomerate to obtain an ultra-coarse tungsten carbide powder.

[0010] As a preferred scheme of the preparation method of the ultra-coarse tungsten carbide powder according to the present invention, wherein: in the step S1, the mass ratio of cobalt oxyhydroxide powder to carbon black is 1:(95-110), the BET of cobalt oxyhydroxide is 42-55 m 2 / g, and the BET of carbon black is 12.5-17.0 m 2 / g.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] According to another aspect of the present invention, the present invention provides the following technical solution:

[0015] 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.

[0016] According to another aspect of the present invention, the present invention provides the following technical solution:

[0017] 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.

[0018] According to another aspect of the present invention, the present invention provides the following technical solution:

[0019] 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.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention provides a method for preparing ultra-coarse tungsten carbide powder, ultra-coarse grain cemented carbide and the same. Cobalt hydroxide oxide powder and carbon black are mixed to prepare a carbon-cobalt composite powder; the carbon-cobalt composite powder and tungsten powder are mixed to prepare a carbon-cobalt-tungsten composite powder; the carbon-cobalt-tungsten composite powder is sintered to prepare WC agglomerates; the WC agglomerates are ball-milled, crushed and classified to prepare ultra-coarse tungsten carbide powder. The present invention promotes the development and carbonization of ultra-coarse single-crystal tungsten carbide by doping cobalt-based powder to prepare ultra-coarse tungsten carbide powder; the FSSS particle size of the as-produced ultra-coarse tungsten carbide powder is > 31.5 μm, its carbonization is complete, the crystal grains are fully developed, and there are few agglomerated pseudo-particles. Moreover, the WC crystal grain size of the ultra-coarse grain cemented carbide prepared by using it is > 7.5 μm, and the microstructure is uniform, without the phenomenon of local decarburization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0023] Figure 1 It is the metallographic diagram of the ultra-coarse tungsten carbide powder prepared in Example 1 of the present invention;

[0024] Figure 2 It is the metallographic diagram of the ultra-coarse grain cemented carbide prepared in Example 1 of the present invention;

[0025] Figure 3 It is the metallographic diagram of the cemented carbide prepared in Comparative Example 6;

[0026] Figure 4 It is the metallographic diagram of the tungsten carbide powder prepared in Comparative Example 9;

[0027] Figure 5 It is the metallographic diagram of the cemented carbide prepared in Comparative Example 9.

[0028] The realization, functional features and advantages of the objectives of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] The present invention provides a super-coarse tungsten carbide powder, a super-coarse grain cemented carbide and a preparation method thereof, which have the following advantages:

[0031] (1) The present invention makes full use of the high specific surface area performance of cobalt hydroxyoxide. By highly mixing with carbon black, cobalt elements are evenly distributed, avoiding agglomeration and segregation, providing a basis for the preparation of tungsten carbide.

[0032] (2) The present invention uses uniformly dispersed cobalt hydroxyoxide to generate cobalt by reduction at the front end of sintering, promoting the carbonization of tungsten powder, making the tungsten carbide fully developed, providing a basis for the coarsening of tungsten carbide.

[0033] (3) The present invention realizes the matching of the specific surface areas of cobalt hydroxyoxide powder and carbon black. The BET values of the two within the scope of the present invention have good miscibility. Being too large or too small will cause agglomeration and uneven dispersion problems. Mixing with each other at the corresponding specific surface areas can effectively avoid the electrostatic agglomeration of fine particles caused by too large specific surface area and the uneven distribution of small mass particles caused by too small specific surface area.

[0034] (4) The present invention adopts the characteristics that cobalt promotes the growth and complete development of tungsten carbide, and the prepared cemented carbide has coarse WC grains and better tissue uniformity.

[0035] According to one aspect of the present invention, the following technical solution is provided:

[0036] A preparation method of a super-coarse tungsten carbide powder, comprising the following steps:

[0037] S1. Placing cobalt hydroxyoxide powder and carbon black in a high-energy plow mixer to mix and prepare a carbon-cobalt composite powder;

[0038] S2. Placing the carbon-cobalt composite powder and tungsten powder in a high-energy plow mixer to mix and prepare a carbon-cobalt-tungsten composite powder;

[0039] S3. Placing the carbon-cobalt-tungsten composite powder in a graphite boat for medium-frequency sintering to prepare a WC agglomerate;

[0040] S4. Ball-milling, crushing and classifying the WC agglomerate to prepare a super-coarse tungsten carbide powder.

[0041] Preferably, in the step S1, the mass ratio of cobalt hydroxyoxide powder to carbon black is 1:(95-110), the BET of cobalt hydroxyoxide is 42-55 m 2 / g, and the BET of carbon black is 12.5-17.0 m 2 / g.

[0042] 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.

[0043] 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.

[0044] Preferably, in step S4, the crushing time is 5-15 min and the classification frequency is 25-35 Hz.

[0045] According to another aspect of the present invention, the present invention provides the following technical solution:

[0046] 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.

[0047] According to another aspect of the present invention, the present invention provides the following technical solution:

[0048] 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.

[0049] According to another aspect of the present invention, the present invention provides the following technical solution:

[0050] 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.

[0051] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0052] Example 1

[0053] A method for preparing ultra-coarse tungsten carbide powder comprises the following steps:

[0054] 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 value of cobalt oxyhydroxide is 48.5 m 2 / g, the BET of carbon black is 15.7 m 2 / g.

[0055] S2. Place the carbon-cobalt composite powder and tungsten powder in a high-energy plow blade mixer and mix them to prepare a carbon-cobalt-tungsten composite powder; the mass ratio of the carbon-cobalt composite powder to the 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.

[0056] S3. Place the carbon-cobalt-tungsten composite powder in a graphite boat and conduct medium-frequency sintering to prepare WC agglomerates; the sintering process is: hold at 1150 °C for 1.5 h, hold at 1365 °C for 4.5 h, and hold at 2200 °C for 8 h.

[0057] S4. Ball mill, crush and classify the WC agglomerates. The crushing time is 10 min and the classification frequency is 30 Hz to prepare super-coarse tungsten carbide powder (as Figure 1 shown), its as-produced FSSS particle size is 32.3 μm, its carbonization is complete, its crystal grains are fully developed, and there are few agglomerated pseudo-particles.

[0058] Use the traditional wet ball milling - spray granulation - pressing - sintering preparation method to prepare super-coarse grain cemented carbide (as Figure 2 shown) from the super-coarse tungsten carbide powder obtained in step S4 and cobalt powder; the cobalt content is 10 wt%, the ball milling time is 3 h, the ball-to-material ratio is 2:1, and the sintering temperature is 1470 °C. The WC crystal grain size of the prepared super-coarse cemented carbide is 8.2 μm and its microstructure is uniform, and there is no phenomenon of local decarburization.

[0059] Example 2

[0060] A preparation method of super-coarse tungsten carbide powder, comprising the following steps:

[0061] S1. Place the cobalt hydroxyoxide powder and carbon black in a high-energy plow blade mixer and mix them to prepare a carbon-cobalt composite powder; the mass ratio of cobalt hydroxyoxide to carbon black is 1:95, the BET of cobalt hydroxyoxide is 42.4 m 2 / g, the BET of carbon black is 16.7 m 2 / g.

[0062] S2. Place the carbon-cobalt composite powder and tungsten powder in a high-energy plow blade mixer and mix them to prepare a carbon-cobalt-tungsten composite powder; the mass ratio of the carbon-cobalt composite powder to the 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.

[0063] S3. Place the carbon-cobalt-tungsten composite powder in a graphite boat and carry out medium-frequency sintering to prepare WC agglomerates. The sintering process is as follows: keep the temperature at 1200 °C for 1 h, keep the temperature at 1350 °C for 5 h, and keep the temperature at 2250 °C for 6 h.

[0064] S4. Grind and crush the WC agglomerates and classify them. The crushing time is 15 min and the classification frequency is 35 Hz to prepare super-coarse tungsten carbide powder. Its as-produced FSSS particle size is 33.5 μm, and it is completely carbonized, with fully developed grains and few agglomerated pseudo-particles.

[0065] Use the traditional wet ball milling - spray granulation - pressing - sintering preparation method to prepare super-coarse grain cemented carbide from the super-coarse tungsten carbide powder obtained in step S4 and cobalt powder. Among them, the cobalt content is 20 wt%, the ball milling time is 4 h, the ball-to-material ratio is 1:1, and the sintering temperature is 1450 °C. The WC grain size of the prepared super-coarse cemented carbide is 8.4 μm and its microstructure is uniform, and there is no phenomenon of local decarburization.

[0066] Example 3

[0067] A preparation method of super-coarse tungsten carbide powder, comprising the following steps:

[0068] S1. Place cobalt oxyhydroxide powder and carbon black in a high-energy plow blade mixer and mix them to prepare a carbon-cobalt composite powder. Among them, the mass ratio of cobalt oxyhydroxide to carbon black is 1:110, the BET of cobalt oxyhydroxide is 54.6 m 2 / g, and the BET of carbon black is 12.7 m 2 / g.

[0069] S2. Place the carbon-cobalt composite powder and tungsten powder in a high-energy plow blade mixer and mix them to prepare a carbon-cobalt-tungsten composite powder. Among them, the mass ratio of the carbon-cobalt composite powder to tungsten powder is 6.18:93.82, and the as-milled FSSS particle size of the tungsten powder is 18.7 μm and the span is 0.93.

[0070] S3. Place the carbon-cobalt-tungsten composite powder in a graphite boat and carry out medium-frequency sintering to prepare WC agglomerates. The sintering process is as follows: keep the temperature at 1100 °C for 2 h, keep the temperature at 1380 °C for 4 h, and keep the temperature at 2230 °C for 8 h.

[0071] S4. Grind and crush the WC agglomerates and classify them. The crushing time is 15 min and the classification frequency is 25 Hz to prepare super-coarse tungsten carbide powder. Its as-produced FSSS particle size is 35.2 μm, and it is completely carbonized, with fully developed grains and few agglomerated pseudo-particles.

[0072] The ultra - coarse tungsten carbide powder obtained in step S4 and cobalt powder were used to prepare ultra - coarse - grained cemented carbide by adopting the traditional 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 the phenomenon of local decarburization.

[0073] Comparative Example 1

[0074] The difference from Example 1 was that the BET of cobalt oxyhydroxide was 28.6m 2 / g.

[0075] The as - produced FSSS particle size of the tungsten carbide powder obtained in this comparative example was 32.9μm. Partial incomplete carbonization of tungsten carbide grains occurred, and the W2C phase appeared. Local decarburization occurred in the prepared cemented carbide, which was local E04.

[0076] Comparative Example 2

[0077] The difference from Example 1 was that the BET of cobalt oxyhydroxide was 63.9m 2 / g.

[0078] The as - produced FSSS particle size of the tungsten carbide powder obtained in this comparative example was 33.5μm. The W2C phase appeared in the center of tungsten carbide grains. The η phase appeared in the prepared cemented carbide, and the judgment grade was E02.

[0079] Comparative Example 3

[0080] The difference from Example 1 was that the BET of carbon black was 20.4m 2 / g.

[0081] The as - produced FSSS particle size of the tungsten carbide powder obtained in this comparative example was 33.9μm. Partial incomplete carbonization of tungsten carbide grains occurred, and the W2C phase appeared. Local decarburization occurred in the prepared cemented carbide, which was local E02.

[0082] Comparative Example 4

[0083] The difference from Example 1 was that the BET of carbon black was 10.7m 2 / g.

[0084] The as - produced FSSS particle size of the tungsten carbide powder obtained in this comparative example was 32.8μm. Partial incomplete carbonization of tungsten carbide grains occurred, and the W2C phase appeared. Local decarburization occurred in the prepared cemented carbide, which was local E04.

[0085] Comparative Example 5

[0086] The difference from Example 1 is that the FSSS particle size of the ground tungsten powder is 13 μm.

[0087] The as-produced FSSS particle size of the tungsten carbide powder obtained in this comparative example is 28.5 μm, the WC grain size of the alloy is 5.6 μm, the microstructure is uniform, and there is no local decarburization phenomenon.

[0088] Comparative Example 6

[0089] The difference from Example 1 is that the span of the tungsten powder is 1.10.

[0090] The as-produced FSSS particle size of the tungsten carbide powder obtained in this comparative example is 30.8 μm, the WC grain size of the alloy is 6.5 μm, the microstructure is uniform, and there is no local decarburization phenomenon (as Figure 3 shown, the grain size is relatively small).

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the sintering process is: holding at 1365 °C for 4.5 h and holding at 2200 °C for 8 h.

[0093] The as-produced FSSS particle size of the tungsten carbide powder obtained in this comparative example is 30.5 μm. Some tungsten carbide grains are incompletely carbonized, the W2C phase appears, and local decarburization occurs in the prepared cemented carbide.

[0094] Comparative Example 8

[0095] The difference from Example 1 is that the sintering process is: holding at 1150 °C for 1.5 h and holding at 2200 °C for 8 h.

[0096] The as-produced FSSS particle size of the tungsten carbide powder obtained in this comparative example is 31.0 μm. Some tungsten carbide grains are incompletely carbonized, the W2C phase appears, and local decarburization occurs in the prepared cemented carbide.

[0097] Comparative Example 9

[0098] The difference from Example 1 is that commercially available tungsten carbide powder with the grade of ZWC300 is used (as Figure 4 shown, there are pseudo-particles), and the FSSS particle size is 32.5 μm.

[0099] The cemented carbide prepared in this comparative example (as Figure 5 shown, the black part is local decarburization) has a grain size of 6.4 μm, and local carburization occurs.

[0100] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for preparing ultra-coarse tungsten carbide powder, characterized in that, Including the following steps: S1. Prepare a carbon-cobalt composite powder by mixing cobalt oxyhydroxide powder and carbon black; the mass ratio of cobalt oxyhydroxide powder to carbon black is 1:(95 - 110), the BET of cobalt oxyhydroxide is 42 - 55 m 2 / g, and the BET of carbon black is 12.5 - 17.0 m 2 / g; S2. Mix carbon-cobalt composite powder and tungsten powder to prepare carbon-cobalt-tungsten composite powder; 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 tungsten powder > 15μm, span < 0.95; S3. Sinter the carbon-cobalt-tungsten composite powder to prepare WC agglomerates; the sintering process is: keep the temperature at 1100~1200°C for 1~2h, keep the temperature at 1350~1380°C for 4~5h, and keep the temperature at 2130~2250°C for 6~10h; S4. Ball mill and classify the WC agglomerates to prepare ultra-coarse tungsten carbide powder. The as-produced FSSS particle size of the ultra-coarse tungsten carbide powder > 31.5μm, and its carbonization is complete and the crystal grains are fully developed.

2. The preparation method of the ultra-coarse tungsten carbide powder according to claim 1, wherein, In the step S4, the crushing time is 5~15min, and the classification frequency is 25~35Hz.

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