JP4651565B2 - Manufacturing method of cemented carbide powder - Google Patents
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本発明は超硬合金粉末およびその製法に関し、特に、微細なＣｏ粉末を有する超硬合金粉末とその製法に関する。 The present invention relates to a cemented carbide powder and a method for producing the same, and more particularly to a cemented carbide powder having fine Co powder and a method for producing the same.
タングステンカーバイド（ＷＣ）−コバルト（Ｃｏ）系超硬合金は耐磨耗性、高温強度および高弾性率に優れているという理由から切削用工具や金型材料等の耐磨耗性部品の素材として広く利用されている。また、このＷＣ−Ｃｏ系超硬合金は、それを構成するＷＣ粒子が微細になるほど耐摩耗性が向上するといわれている。一方、ＣｏはＷＣ−Ｃｏ系超硬合金の中でＷＣの粒子間において結合相の役割を担うものであるが、ＷＣ−Ｃｏ系超硬合金ではＣｏがＷＣ−Ｃｏ粒子間に均一な厚みになるように分散していることが要求されている。しかし、通常、ＷＣ−Ｃｏ粒子の粒界にはＣｏプールと呼ばれるようなＣｏの大きな粒子が存在することがあり、このＣｏプールは破壊源になりやすく機械的強度の低下をもたらす原因となっている。 Tungsten Carbide (WC) -Cobalt (Co) cemented carbide is excellent in wear resistance, high temperature strength and high elastic modulus, and is used as a material for wear resistant parts such as cutting tools and mold materials. Widely used. In addition, it is said that the wear resistance of this WC-Co cemented carbide is improved as the WC particles constituting the WC-Co cemented carbide become finer. On the other hand, Co plays a role of a bonding phase among WC particles in the WC-Co cemented carbide, but in the WC-Co cemented carbide, Co has a uniform thickness between the WC-Co particles. It is required to be distributed as follows. However, there are usually large Co particles called Co pools at the grain boundaries of WC-Co particles, and these Co pools are likely to become a source of fracture and cause a decrease in mechanical strength. Yes.
そこで、近年、以下に記すような工法によって、ＷＣ−Ｃｏ系超硬合金に用いるＷＣ粉末およびＣｏ粉末の微粒化が図られている。 Therefore, in recent years, WC powder and Co powder used for WC-Co cemented carbide have been atomized by the following construction method.
第１の工法は、ＷおよびＣｏを含有する水溶液を噴霧乾燥し、次いで、得られたＷおよびＣｏを含有する前駆体粉末に炭素粉末を混合し加熱してＷを炭化させるものである。このような製法によって約１００ｎｍのＷＣ粉末が得られることが開示されている（例えば、特許文献１の００２０段落参照）。 In the first method, an aqueous solution containing W and Co is spray-dried, and then carbon powder is mixed with the obtained precursor powder containing W and Co and heated to carbonize W. It is disclosed that a WC powder of about 100 nm can be obtained by such a production method (see, for example, paragraph 0020 of Patent Document 1).
第２の工法は、ＷおよびＣｏを含有する水溶液を噴霧乾燥し、次いで、得られたＷおよびＣｏを含有する前駆体粉末に炭素粉末を添加して粉砕し、さらに、この炭素粉末とともに粉砕されたＷおよびＣｏを含む粉末をＣＯ／Ｈ２の混合ガスの雰囲気にて加熱するものである。この製法によって平均粒径が２００ｎｍの超硬合金粉末の前駆体が得られることが開示されている（例えば、特許文献２参照）。
しかしながら、上記第１および第２の工法を用いた場合、ＷＣ粉末については上述のように微粒の粉末を得ることができるものの、Ｃｏ粉末についてはＷＣ粉末に比べて粒径の大きいものが含まれることがあり、このため、上記のＷＣ粉末とＣｏ粉末とを用いて超硬合金を作製した場合、超硬合金を構成するＷＣ粒子間にＣｏプールほどの大きさの粗大粒子が形成されることがあり、このようなＣｏの粗大粒子を含む超硬合金は機械的強度および硬度低下の問題となっている。 However, when the first and second construction methods are used, a fine powder can be obtained as described above for the WC powder, but the Co powder includes a powder having a larger particle size than the WC powder. Therefore, when a cemented carbide is produced using the above WC powder and Co powder, coarse particles as large as a Co pool are formed between WC particles constituting the cemented carbide. The cemented carbide containing such coarse Co particles is a problem of mechanical strength and hardness reduction.
従って本発明は、ＷＣ粉末とともに、微粒のＣｏ粉末が均一に分布する超硬合金粉末およびその製法を提供することを目的とする。 Accordingly, an object of the present invention is to provide a cemented carbide powder in which fine Co powder is uniformly distributed together with WC powder and a method for producing the same.
また本発明の超硬合金粉末の製法は、メタタングステン酸アンモニウム塩と硝酸コバルトとを含み、ｐＨが４〜７のＷ−Ｃｏ含有水溶液を調製する工程と、該Ｗ−Ｃｏ含有水溶液を大気中、温度２００〜４００℃、供給流速１０〜８０ｌ／分で４流体ノズルを用いて噴霧乾燥してＷおよびＣｏを含む前駆体粉末を得る工程と、前記前駆体粉末をＣＯ／Ｈ２
混合ガス中で加熱する工程とを具備することを特徴とする。
The method for producing the cemented carbide powder of the present invention includes a step of preparing a W—Co-containing aqueous solution having an ammonium metatungstate salt and cobalt nitrate and having a pH of 4 to 7, and the W—Co-containing aqueous solution in the atmosphere. Spray drying using a four-fluid nozzle at a temperature of 200 to 400 ° C. and a supply flow rate of 10 to 80 l / min to obtain a precursor powder containing W and Co, and the precursor powder is converted into CO / H 2
And heating in a mixed gas.
本発明の超硬合金粉末は、上述のように、超硬合金粉末中に含まれるＣｏ粉末の平均粒径が微粒であり、特に、１００ｎｍ以上のサイズの個数の割合が４％以下と少なく微粒のＣｏ粉末が均一に分布するものである。このため本発明の超硬合金粉末を用いて超硬合金を作製した場合、超硬合金を構成するＷＣ粒子間にＣｏプールのような粗大なＣｏ粒子を少なくできることから超硬合金の機械的強度および硬度を高めることができる。 In the cemented carbide powder of the present invention, as described above, the average particle size of the Co powder contained in the cemented carbide powder is fine, and in particular, the proportion of the number of sizes of 100 nm or more is as small as 4% or less. Co powder is uniformly distributed. Therefore, when a cemented carbide is produced using the cemented carbide powder of the present invention, the mechanical strength of the cemented carbide can be reduced because coarse Co particles such as a Co pool can be reduced between the WC particles constituting the cemented carbide. And can increase the hardness.
また、本発明の超硬合金粉末の製法は、ＷとＣｏの成分を含有する水溶液のｐＨを所定の範囲に制御する工法であるために、Ｃｏの水酸化物などの生成が低減され噴霧時の凝集がないために小径化が容易となること、また、得られたＷの酸化物およびＣｏの酸化物を含む前駆体粉末をＣＯ／Ｈ２混合ガスで還元および炭化する工法であることから、Ｗ粉末の周囲に一様に炭素成分を分散でき、このため従来の炭素粉末を用いる場合のように炭素粉末の混合操作によるＣｏ粉末の変形や局部的な反応が抑制され、より均一なＷＣ粉末を容易に得ることができる。こうして上記した、ＷＣ粉末およびＣｏ粉末を含む超硬合金粉末であって、前記ＷＣ粉末は平均粒径が５０〜２００ｎｍであり、前記Ｃｏ粉末は粒径が１００ｎｍ以上のＣｏ粉末数が全Ｃｏ粉末数の４％以下の割合である超硬合金粉末を容易に得ることができる。 In addition, since the method of manufacturing the cemented carbide powder of the present invention is a method of controlling the pH of the aqueous solution containing the W and Co components to a predetermined range, the production of Co hydroxide and the like is reduced, and at the time of spraying. Because it does not agglomerate, it is easy to reduce the diameter, and the obtained precursor powder containing oxides of W and Co is reduced and carbonized with a CO / H 2 mixed gas. The carbon component can be uniformly dispersed around the W powder, so that the deformation and local reaction of the Co powder due to the mixing operation of the carbon powder is suppressed as in the case of using the conventional carbon powder, and the more uniform WC. A powder can be obtained easily. Thus, the above-mentioned cemented carbide powder containing WC powder and Co powder, wherein the WC powder has an average particle size of 50 to 200 nm, and the Co powder has a Co particle number of 100 nm or more and the total number of Co powders. A cemented carbide powder having a ratio of 4% or less of the number can be easily obtained.
図１は、本発明の超硬合金粉末の電子顕微鏡写真である。 FIG. 1 is an electron micrograph of the cemented carbide powder of the present invention.
本発明の超硬合金粉末は、それを構成するＷＣ粉末の平均粒径が５０〜２００ｎｍであることを特徴とするものであり、特に、５０〜１４０ｎｍであることが望ましい。ＷＣ粉末の平均粒径が上記の範囲のように微粒であると、このようなＷＣ粉末を用いて形成される焼結体の硬度（ビッカース硬度Ｈｖ１０ ＪＩＳＲ１６１０）および室温曲げ強度（ＪＩＳ１６０１）を高めることができるという利点がある。これに対して、ＷＣ粉末の平均粒径が５０ｎｍよりも小さい場合には室温曲げ強度および硬度の大きな低下が見られ、一方、ＷＣ粉末の平均粒径が２００ｎｍよりも大きい場合にも室温曲げ強度および硬度が低下する。また、本発明の超硬合金粉末は、前記Ｃｏ粉末は粒径が１００ｎｍ以上のＣｏ粉末数が全Ｃｏ粉末数の４％以下の割合であることを特徴とする。また、粒径が１００ｎｍ以上のＣｏ粉末数が全Ｃｏ粉末数の４％以下であることが重要である。Ｃｏ粉末が１００ｎｍ以上のサイズの個数の割合が４％以下であると、たとえ、超硬合金粉末中に１００ｎｍ以上のサイズのＣｏ粉末が含まれていたとしても、その数が少ないためにＣｏの分散性が高く、しかもＣｏ粉末同士が焼結中に凝集しにくくなり、このためＷＣ粉末を用いて形成される焼結体においてＷＣ粒子間にＣｏプールなどの粒径が１００ｎｍ以上もあるような粗大な粒子が形成されにくくなるという利点がある。その結果、室温曲げ強度や硬度を高めることができる。 The cemented carbide powder of the present invention is characterized in that the average particle size of the WC powder constituting the cemented carbide powder is 50 to 200 nm, and particularly preferably 50 to 140 nm. When the average particle diameter of the WC powder is fine as in the above range, the hardness (Vickers hardness Hv10 JISR1610) and room temperature bending strength (JIS1601) of the sintered body formed using such WC powder are increased. There is an advantage that can be. On the other hand, when the average particle diameter of the WC powder is smaller than 50 nm, the room temperature bending strength and the hardness are greatly reduced. On the other hand, when the average particle diameter of the WC powder is larger than 200 nm, the room temperature bending strength is also observed. And the hardness decreases. Further, the cemented carbide powder of the present invention is characterized in that the number of Co powders having a particle size of 100 nm or more is 4% or less of the total number of Co powders. In addition, it is important that the number of Co powders having a particle size of 100 nm or more is 4% or less of the total number of Co powders. If the ratio of the number of Co powders having a size of 100 nm or more is 4% or less, even if the cemented carbide powder contains Co powders of a size of 100 nm or more, the number of Co powders is small. The dispersibility is high and the Co powders are less likely to agglomerate during the sintering. For this reason, in the sintered body formed using the WC powder, the particle size of the Co pool or the like is 100 nm or more between the WC particles. There is an advantage that coarse particles are hardly formed. As a result, room temperature bending strength and hardness can be increased.
また本発明の超硬合金粉末はＣｏ粉末の平均粒径が４０ｎｍ〜６０ｎｍであることが望ましい。Ｃｏ粉末の平均粒径が４０ｎｍ〜６０ｎｍであると粒径が１００ｎｍ以上のＣｏ粉末数が全Ｃｏ粉末数を低減できるという理由がある。 The cemented carbide powder of the present invention preferably has an average particle diameter of Co powder of 40 nm to 60 nm. If the average particle size of the Co powder is 40 nm to 60 nm, the number of Co powders having a particle size of 100 nm or more can reduce the total number of Co powders.
この場合、本発明の超硬合金粉末においては、Ｃｏ粉末量が５〜１５質量％であることが望ましい。超硬合金粉末においてＣｏ粉末量が５〜１５質量％であると、後述の実施例の結果から明らかなように平均粒径が５０〜２００ｎｍであるＷＣ粉末と混合したとき高強度および高硬度となる。これはＷＣ粒子の周囲にＣｏの結合相を均一に形成できるためである。 In this case, in the cemented carbide powder of the present invention, the amount of Co powder is desirably 5 to 15% by mass. When the amount of Co powder in the cemented carbide alloy powder is 5 to 15% by mass, when mixed with WC powder having an average particle size of 50 to 200 nm, as is clear from the results of Examples described later, Become. This is because a Co binder phase can be uniformly formed around the WC particles.
また本発明の超硬合金粉末は、Ｖ、Ｃｒ、ＴａおよびＮｂから選ばれる少なくとも１種を炭化物換算で０．１〜２質量％含有することが望ましい。ＷＣ粉末およびＣｏ粉末に上記Ｖ、Ｃｒ、ＴａおよびＮｂの炭化物を添加すると、ＷＣ−Ｃｏ系の超硬合金においてＷＣ粒子およびＣｏ粒子の粒成長が抑えられるという利点がある。これは上記Ｖ、Ｃｒ、ＴａおよびＮｂなどの炭化物が高融点であるためにＷＣ粉末およびＣｏ粉末に対して粒成長抑制剤としてはたらくことに起因する。また、これらの粉末から形成された焼結体においてＶ、Ｃｒ、ＴａおよびＮｂなどの炭化物はＷＣ粒子とＣｏ粒子との界面における中間体としてはたらくため、ＷＣ粒子とＣｏ粒子との結合を強固にできるという作用を有する。そのためＷＣ−Ｃｏ系の超硬合金中のＶ、Ｃｒ、ＴａおよびＮｂの炭化物が少ないと室温曲げ強度や硬度が低下し、一方、Ｖ、Ｃｒ、ＴａおよびＮｂの炭化物が多い場合にはＣｏ粒子の粒成長が起こり低硬度となる。Ｖ、Ｃｒ、ＴａおよびＮｂの炭化物は粉末の調整時にＷＣ粉末やＣｏ粉末に付着し、または一部固溶しているものであり、その粒径はＷＣ粉末よりも細かく、１０〜１００ｎｍであることがＷＣ粉末同士の焼結性を高めるという点で望ましい。 Moreover, it is desirable that the cemented carbide powder of the present invention contains at least one selected from V, Cr, Ta and Nb in an amount of 0.1 to 2% by mass in terms of carbide. When the carbides of V, Cr, Ta, and Nb are added to WC powder and Co powder, there is an advantage that grain growth of WC particles and Co particles can be suppressed in a WC-Co based cemented carbide. This is due to the fact that carbides such as V, Cr, Ta, and Nb have a high melting point and thus act as grain growth inhibitors for WC powder and Co powder. In the sintered body formed from these powders, carbides such as V, Cr, Ta, and Nb act as intermediates at the interface between the WC particles and the Co particles, so that the bonding between the WC particles and the Co particles is strengthened. Has the effect of being able to. Therefore, if there are few carbides of V, Cr, Ta and Nb in the WC-Co based cemented carbide, the room temperature bending strength and hardness will be reduced. On the other hand, if there are many carbides of V, Cr, Ta and Nb, Co particles Grain growth occurs and the hardness becomes low. The carbides of V, Cr, Ta and Nb are attached to the WC powder or Co powder at the time of adjusting the powder, or are partly dissolved, and the particle size thereof is finer than that of the WC powder and is 10 to 100 nm. This is desirable in terms of enhancing the sinterability between WC powders.
次に、本発明の超硬合金粉末の製法について説明する。図２は、本発明の超硬合金粉末を製造するための工程図である。 Next, the manufacturing method of the cemented carbide powder of this invention is demonstrated. FIG. 2 is a process diagram for producing the cemented carbide powder of the present invention.
本発明の超硬合金粉末の製法は、Ｗ粉末およびＣｏ粉末を調製するのにＷを含む塩およびＣｏを含む塩を用いることを特徴とする。ここではＷを含む塩として好適なものはメタタングステン酸アンモニウム（（ＮＨ４）６（Ｈ２Ｗ１２Ｏ４０）であり、一方、Ｃｏを含む塩として硝酸コバルト（Ｃｏ（ＮＯ３）２を用いる。これらの出発原料を目的組成に合うように秤量してから水に溶かして水溶液を調製する。この場合、ＷやＣｏ以外のＶ、Ｃｒ、Ｎｂ、Ｔａなどの添加物についても硝酸塩などを用いて、水溶液として混合することができる。なお、上記したＷおよびＣｏの成分を水溶液とする方法ではＷおよびＣｏならびに他の添加剤の組成は任意に調整できることはいうまでもない。 The method for producing a cemented carbide powder according to the present invention is characterized in that a salt containing W and a salt containing Co are used to prepare W powder and Co powder. Here, ammonium metatungstate ((NH 4 ) 6 (H 2 W 12 O 40 ) is preferable as the salt containing W, while cobalt nitrate (Co (NO 3 ) 2 is used as the salt containing Co. These starting materials are weighed to suit the target composition and then dissolved in water to prepare an aqueous solution, in which case nitrates are used for additives such as V, Cr, Nb and Ta other than W and Co. It should be understood that the composition of W, Co, and other additives can be arbitrarily adjusted in the above-described method in which the components of W and Co are used as an aqueous solution.
また本発明では、ＷおよびＣｏを含有する水溶液のｐＨを４〜７に調整することが重要である。ＷおよびＣｏを含有する水溶液のｐＨが７以下であると、水溶液の段階や噴霧直前の加熱された段階においてＣｏの水酸化物が生成するのを抑制でき、後述の噴霧乾燥を行った際にＣｏ成分同士の凝集を抑制できるという利点がある。一方、ｐＨが４以上であると水溶液の酸性度が弱くなり、噴霧乾燥時における突発的な酸性ガスの発生を抑制できるために中空状の粉末になりにくく中実球を容易に形成できることから、より微粒のタングステン粉末やコバルト粉末が得られるという利点がある。また酸性度が弱いために装置や人体への影響を低減できるという利点もある。 In the present invention, it is important to adjust the pH of the aqueous solution containing W and Co to 4-7. When the pH of the aqueous solution containing W and Co is 7 or less, it is possible to suppress the formation of Co hydroxide in the aqueous solution stage or the heated stage immediately before spraying. There is an advantage that aggregation of Co components can be suppressed. On the other hand, if the pH is 4 or more, the acidity of the aqueous solution becomes weak, and since it is possible to suppress the sudden generation of acidic gas during spray drying, it is difficult to form a hollow powder, and a solid sphere can be easily formed. There is an advantage that finer tungsten powder and cobalt powder can be obtained. Further, since the acidity is weak, there is an advantage that the influence on the apparatus and the human body can be reduced.
次に、調製したＷ−Ｃｏ含有水溶液を、噴霧乾燥装置を用いて噴霧乾燥を行いＷ−Ｃｏの酸化物を含む前駆体を得る。本発明の製法では、この装置において４流体ノズル式の噴霧熱分解装置を用いることが望ましい。本発明の製法における噴霧乾燥の工程では、上記のように噴霧口に４流体ノズルを用いることを特徴とする。４流体ノズルは４つの噴霧口を有するものであるが、この場合、噴霧するＷおよびＣｏを含有する水溶液用のほかにキャリアガスや水溶液の濃度や速度および液滴のサイズを調整するための媒体供給用となる。 Next, the prepared W—Co-containing aqueous solution is subjected to spray drying using a spray drying apparatus to obtain a precursor containing an oxide of W—Co. In the production method of the present invention, it is desirable to use a four-fluid nozzle type spray pyrolysis apparatus in this apparatus. The spray drying step in the production method of the present invention is characterized in that a four-fluid nozzle is used for the spray port as described above. The four-fluid nozzle has four spray ports. In this case, in addition to the aqueous solution containing W and Co to be sprayed, a medium for adjusting the concentration and speed of the carrier gas and aqueous solution, and the droplet size For supply.
こうした構造を有する特殊なノズルを用いることにより噴霧される液滴のサイズを微小にでき、しかも噴霧乾燥に特有の得られる粉末の中空化を防止できる。この噴霧乾燥は後述の実施例によると、大気中、温度２００〜４００℃、供給流速は１０〜８０ｌ／分程度が好適である。なお、ＷおよびＣｏを含む前駆体粉末の平均粒径が１０００〜５０００ｎｍであることが望ましい。 By using a special nozzle having such a structure, the size of droplets to be sprayed can be reduced, and hollowing of the resulting powder, which is characteristic of spray drying, can be prevented. According to the examples described later, this spray drying is preferably performed in the atmosphere at a temperature of 200 to 400 ° C. and a supply flow rate of about 10 to 80 l / min. The average particle size of the precursor powder containing W and Co is desirably 1000 to 5000 nm.
次に、得られたＷ−Ｃｏの前駆体を一旦１００〜７５０℃の温度にＮ２などの不活性ガス中において加熱してＷ−Ｃｏの酸化物の前駆体中に残存している原料である水溶液の成分を除去することによりＷ−Ｃｏの複合酸化物を得る。 Next, the obtained W-Co precursor is once heated to a temperature of 100 to 750 ° C. in an inert gas such as N 2, and the raw material remaining in the W-Co oxide precursor is used. By removing the components of an aqueous solution, a W-Co composite oxide is obtained.
次に、このＷ−Ｃｏの複合酸化物をＣＯ／Ｈ２混合ガスにより還元および炭化して本発明の超硬合金を得る。このときの温度はＷおよびＣｏの還元を促進し、Ｗの炭化を速めるという点で７００〜９００℃が好ましい。なお、ＣＯ／Ｈ２の割合は０．５〜１．５／３〜５が好ましい。ＣＯガスの割合はＷの炭化と、炭化の前のＷおよびＣｏの酸化物を還元するという理由から上記の範囲が望ましい。 Next, this W—Co composite oxide is reduced and carbonized with a CO / H 2 mixed gas to obtain the cemented carbide of the present invention. The temperature at this time is preferably 700 to 900 ° C. in that the reduction of W and Co is promoted and the carbonization of W is accelerated. The ratio of CO / H 2 is preferably 0.5 to 1.5 / 3-5. The ratio of the CO gas is preferably in the above-mentioned range for the reason that the carbonization of W and the oxides of W and Co before carbonization are reduced.
この後、上記得られた超硬合金粉末を一旦解砕した後パラフィンワックスをイソプロピルアルコールを用いて添加して所定の形状に成形し、１２００〜１４００℃の温度で真空加圧焼成を行うことにより超硬合金の焼結体が得られる。 Thereafter, the cemented carbide powder obtained above is once crushed and then paraffin wax is added using isopropyl alcohol to form a predetermined shape, followed by vacuum pressure firing at a temperature of 1200 to 1400 ° C. A sintered body of cemented carbide is obtained.
このように本発明の超硬合金粉末の製法は、噴霧乾燥工程を取り入れた従来の製法に比較してＷおよびＣｏ成分を含む水溶液のｐＨを調整することにより、噴霧乾燥時の水溶液の温度上昇による水溶液に発生する水酸化物などの凝集を抑制できること、および噴霧乾燥後の前駆体粉末の中空化を抑制できるために微粒のＣｏやＷを含有する前駆体を形成できる。 As described above, the method for producing the cemented carbide powder of the present invention increases the temperature of the aqueous solution during spray drying by adjusting the pH of the aqueous solution containing the W and Co components as compared with the conventional method incorporating a spray drying process. It is possible to suppress aggregation of hydroxide and the like generated in the aqueous solution due to the above, and to suppress hollowing of the precursor powder after spray drying, so that a precursor containing fine Co and W can be formed.
Ｗ原料としてメタタングステン酸アンモニウム（純度９９．９％、新日本無機化学）、Ｃｏ原料として硝酸コバルト（純度９９％、関東化学）、添加物としてバナジン酸アンモニウム、酢酸クロム、酢酸ニオブ、酢酸タンタル（全て純度９９％、関東化学）を用意した。ここではＷ、Ｃｏおよび添加物の組成は表２に示す比率で変化させた。調合した塩などの粉末を、質量比で１０〜２０％になるようにイオン交換水に溶かし、マグネチックスターラーで１時間攪拌した。その際、ＷおよびＣｏを含む水溶液のｐＨをモニターし、アンモニア水もしくは塩酸を滴下してｐＨが２〜９になるように調整した。Ｗ−Ｃｏ含有水溶液のｐＨをアルカリ性にする場合は溶液調整時にアンモニア水を添加した。一方、ｐＨを低下させるために硝酸を添加した。 Ammonium metatungstate (purity 99.9%, Shin Nippon Inorganic Chemical) as a W raw material, cobalt nitrate (purity 99%, Kanto Chemical) as a Co raw material, ammonium vanadate, chromium acetate, niobium acetate, tantalum acetate (additives) All were 99% pure, Kanto Chemical). Here, the compositions of W, Co, and additives were changed at the ratios shown in Table 2. The prepared powder such as salt was dissolved in ion-exchanged water so as to have a mass ratio of 10 to 20%, and stirred for 1 hour with a magnetic stirrer. At that time, the pH of the aqueous solution containing W and Co was monitored, and ammonia water or hydrochloric acid was added dropwise to adjust the pH to 2-9. In order to make the pH of the aqueous solution containing W-Co alkaline, aqueous ammonia was added during the preparation of the solution. On the other hand, nitric acid was added to lower the pH.
次に、攪拌後のＷ、Ｃｏおよび添加物を含む水溶液をローラーポンプを用いて６０ｍｌ／分の流速で４流体ノズル式スプレードライ装置に送り、１０〜８０ｌ／分の速度で２５０℃の熱風を送って噴霧乾燥を行った。また、一部の試料については一般のスプレードライ装置を用いる回転型の遠心式ノズルを使用した。
Next, the aqueous solution containing W, Co and additives after stirring is sent to a four- fluid nozzle spray dryer at a flow rate of 60 ml / min using a roller pump, and hot air at 250 ° C. at a rate of 10 to 80 l / min. Spray drying was carried out. For some samples, a rotary centrifugal nozzle using a general spray drying apparatus was used.
噴霧乾燥処理後のＷ−Ｃｏの前駆体粉末はバグフィルターで回収した後、さらに１１０℃で１２時間乾燥させた。 The W-Co precursor powder after the spray-drying treatment was recovered with a bag filter and further dried at 110 ° C. for 12 hours.
次に、乾燥処理したＷ−Ｃｏの前駆体粉末を電気雰囲気炉に導入し、窒素雰囲気中７００℃で２時間加熱し、余分な水分やアンモニアなどを熱分解して除去して複合酸化物を得た。さらに炉を表１に示す温度に上昇させ、ＣＯ／Ｈ２ガスを１：４の比率で導入し、５時間熱処理することにより複合酸化物を還元・炭化して超硬合金粉末を得た。ＣＯ／Ｈ２ガスの代わりに炭素粉末による炭化処理も行った。 Next, the dried W—Co precursor powder is introduced into an electric atmosphere furnace and heated in a nitrogen atmosphere at 700 ° C. for 2 hours to thermally decompose and remove excess moisture and ammonia to remove the composite oxide. Obtained. Further, the furnace was raised to the temperature shown in Table 1, CO / H 2 gas was introduced at a ratio of 1: 4, and the composite oxide was reduced and carbonized by heat treatment for 5 hours to obtain cemented carbide powder. Carbonization with carbon powder was also performed instead of CO / H 2 gas.
得られた超硬合金粉末におけるＷＣ粉末およびＣｏ粉末それぞれの平均粒径、および超硬合金粉末中におけるＣｏ粉末の１００ｎｍ以上の粒子の個数の割合を求めた。この場合、得られた超硬合金粉末を電子顕微鏡を用いて粉末が１００個程度入るように１〜１０万倍にて写真を撮り、写真に映し出された粉末を画像処理により輪郭を描き、その輪郭を円とみたてて各々直径を計測し平均化した。ＷＣとＣｏは電子顕微鏡に付設の分析器（ＥＤＳ）により同定し確認して測定を進めた。測定箇所は３箇所とした。 The average particle diameter of each of the WC powder and Co powder in the obtained cemented carbide powder and the ratio of the number of particles of 100 nm or more of the Co powder in the cemented carbide powder were determined. In this case, the obtained cemented carbide powder is photographed at a magnification of 1 to 100,000 times so that about 100 powders are contained using an electron microscope, and the powder projected on the photograph is outlined by image processing. The contour was regarded as a circle, and the diameters were measured and averaged. WC and Co were identified and confirmed by an analyzer (EDS) attached to the electron microscope, and the measurement proceeded. Three measurement points were used.
前駆体粉末の平均粒径についても同じようにして求めた。この場合、写真内に３０個ほど入る写真から求めた。これも測定箇所は３箇所とした。 The average particle size of the precursor powder was determined in the same manner. In this case, it was obtained from a photograph that has about 30 pieces in the photograph. Again, there were three measurement locations.
得られた超硬合金粉末にパラフィンワックスとＩＰＡを混合して振動ミルで４８時間混合し、噴霧乾燥して造粒した後、成形し、加圧焼成炉にて１３００℃で焼成した。でき上がった焼結体は、表面を鏡面研磨し、３点曲げ強度（ＪＩＳ１６０１）およびビッカース硬度（ＪＩＳ１６１０）の測定を行った。以上の結果を表１、２に示した。 The obtained cemented carbide powder was mixed with paraffin wax and IPA, mixed with a vibration mill for 48 hours, spray-dried, granulated, molded, and fired at 1300 ° C. in a pressure firing furnace. The finished sintered body was mirror-polished on the surface and measured for three-point bending strength (JIS1601) and Vickers hardness (JIS1610). The above results are shown in Tables 1 and 2 .
表１、２の結果から、本発明の製法によって調製した試料では、ＷＣ粉末の平均粒径が５０〜２００ｎｍであり、Ｃｏの平均粒径が４０〜８０ｎｍであり、かつ全Ｃｏ粉末に対して０．１μｍ以上の平均粒径を有するＣｏ粉末の割合が４％以下であった。また、本発明の実施例に該当する試料では、ビッカース硬度で１６５０以上の値を有し、３点曲げ強度で３２００ＭＰａ以上であり、高強度でかつ高硬度な超硬材料が作製できることを確認できた。また、Ｃｏ粉末の含有量を５〜１５質量％の範囲とした試料ではビッカース硬度が２００１以上の値を有し、３点曲げ強度で３８４０ＭＰａ以上であった。特に、ＷおよびＣｏを含有する水溶液のｐＨを４〜７に調整し、Ｃｏ粉末の含有量をについて平均粒径が４０〜６０ｎｍであり、１００ｎｍ以上のサイズのＣｏ粉末のない試料では、ビッカース硬度が２０３５以上の値を有し、３点曲げ強度で４０００ＭＰａ以上であった。本発明の試料では最長径が１０００ｎｍ以上のＣｏプールのようなＣｏ粒子は観察されなかったがＣｏ粒子の平均粒径が１０５ｎｍおよび１２０ｎｍを有する試料では最長径が１１００ｎｍおよび１２００ｎｍのＣｏプールのようなＣｏ粒子が観察された。 From the results of Tables 1 and 2, in the sample prepared by the production method of the present invention, the average particle diameter of the WC powder is 50 to 200 nm, the average particle diameter of Co is 40 to 80 nm, and the total Co powder The proportion of Co powder having an average particle size of 0.1 μm or more was 4% or less. In addition, it can be confirmed that a sample corresponding to the example of the present invention has a Vickers hardness value of 1650 or more, a three-point bending strength of 3200 MPa or more, and can produce a high strength and high hardness cemented carbide material. It was. Moreover, the sample which made content of Co powder the range of 5-15 mass% had the value of Vickers hardness of 2001 or more, and was 3840 MPa or more in 3 point | piece bending strength. In particular, the pH of the aqueous solution containing W and Co is adjusted to 4 to 7, and the average particle size of the Co powder content is 40 to 60 nm, and the sample without Co powder having a size of 100 nm or more is Vickers hardness. Has a value of 2035 or more and a three-point bending strength of 4000 MPa or more. In the sample of the present invention, Co particles such as a Co pool having a longest diameter of 1000 nm or more were not observed, but in a sample having an average particle diameter of Co particles of 105 nm and 120 nm, such as a Co pool having a longest diameter of 1100 nm and 1200 nm. Co particles were observed.
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| JP2009167503A (en) * | 2008-01-21 | 2009-07-30 | Hitachi Tool Engineering Ltd | Fine-grained cemented carbide |
| JP5522712B2 (en) * | 2008-08-25 | 2014-06-18 | 公立大学法人兵庫県立大学 | Transition metal-encapsulated tungsten carbide, tungsten carbide-dispersed cemented carbide and method for producing the same |
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| JP6780697B2 (en) | 2016-03-01 | 2020-11-04 | 日立金属株式会社 | Method for manufacturing composite particles, composite powder, composite particles, and manufacturing method for composite members |
| JP2018035020A (en) * | 2016-08-30 | 2018-03-08 | 住友電気工業株式会社 | Aqueous solution composition and method for producing the same, oxide powder and method for producing the same, carbide powder and method for producing the same, and cemented carbide and method for producing the same |
| JP7151722B2 (en) * | 2017-12-18 | 2022-10-12 | 住友電気工業株式会社 | Tungsten carbide powder, tungsten carbide-cobalt metal composite powder, and cemented carbide |
| CN108411137B (en) * | 2018-04-10 | 2020-02-11 | 南京理工大学 | Preparation method of ultra-fine grain tungsten carbide-based hard alloy |
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