JP2006045601A - Hard powder and method for producing cemented carbide using the powder - Google Patents
Hard powder and method for producing cemented carbide using the powder Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 101
- 238000004519 manufacturing process Methods 0.000 title abstract description 5
- 239000002002 slurry Substances 0.000 claims abstract description 35
- 239000002245 particle Substances 0.000 claims abstract description 24
- 239000002904 solvent Substances 0.000 claims abstract description 22
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 9
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- 239000001301 oxygen Substances 0.000 claims description 9
- 239000003125 aqueous solvent Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 abstract description 14
- 238000004663 powder metallurgy Methods 0.000 abstract description 4
- 238000012856 packing Methods 0.000 abstract 1
- 238000001694 spray drying Methods 0.000 description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 239000000654 additive Substances 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
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- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 239000011195 cermet Substances 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000007908 dry granulation Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
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- 238000012360 testing method Methods 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
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- 150000001450 anions Chemical class 0.000 description 1
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- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
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- 239000000314 lubricant Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
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- 238000003825 pressing Methods 0.000 description 1
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- 239000002893 slag Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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Abstract
Description
本発明は、炭化タングステン基超硬合金等の硬質合金用の硬質粉末と、該硬質粉末を用いて作製した炭化タングステン基超硬合金に関するものである。 The present invention relates to a hard powder for a hard alloy such as a tungsten carbide-based cemented carbide and a tungsten carbide-based cemented carbide manufactured using the hard powder.
粉末冶金法に用いる超硬合金やサーメット等の硬質合金の硬質粉末に関する技術が以下の特許文献１〜３に開示されている。特許文献１〜３には、超硬合金、サーメット等の硬質合金粉末の製造方法として、所定配合の原料粉末をアルコール、水、四塩化炭素等の溶媒と共にボールミルにて湿式混合したスラリーを乾燥して造粒する方法が開示されている。特許文献４、５には、造型工程での硬質粉末の流動度、潤滑性を高め、圧力の均質化を図るため、潤滑剤を粉末に含ませて使用する技術が開示されている。 Techniques relating to hard powders of hard alloys such as cemented carbide and cermet used in powder metallurgy are disclosed in Patent Literatures 1 to 3 below. In Patent Documents 1 to 3, as a method for producing hard alloy powders such as cemented carbide and cermet, a slurry obtained by wet mixing a raw material powder of a predetermined composition with a solvent such as alcohol, water, carbon tetrachloride and the like in a ball mill is dried. And a granulating method is disclosed. Patent Documents 4 and 5 disclose a technique in which a lubricant is used in a powder in order to increase the fluidity and lubricity of the hard powder in the molding process and to homogenize the pressure.
本発明は、粉末冶金法により炭化タングステン基超硬合金を製造する時に用いる硬質粉末において、充填性、流動性に優れた特性を有する硬質粉末を提供し、更に、該硬質粉末を用いて焼結体を作製することにより、優れた強度、有孔度を得る炭化タングステン基超硬合金を提供することを目的とする。 The present invention provides a hard powder having characteristics excellent in filling property and fluidity in a hard powder used when producing a tungsten carbide base cemented carbide by a powder metallurgy method, and further sintering using the hard powder. An object of the present invention is to provide a tungsten carbide-based cemented carbide that obtains excellent strength and porosity by producing a body.
本願発明は、水溶媒と炭化タングステン、Ｃｏを含み、不可避不純物との組合せの原料粉末からなるスラリーを乾燥・造粒した硬質粉末において、該硬質粉末の平均粒径が３０から８０μｍ、嵩密度が３．０から３．７ｇ／ｃｍ３、平均球形度が０．７以上であることを特徴とする硬質粉末である。更に、炭化タングステン基超硬合金において、水溶媒と炭化タングステン、Ｃｏを含み、不可避不純物との組合せの原料粉末からなるスラリーを乾燥・造粒し、該硬質粉末の平均粒径が３０から８０μｍ、嵩密度が３．０から３．７ｇ／ｃｍ３、平均球形度が０．７以上に造粒した硬質粉末を用いて製造することを特徴とする炭化タングステン基超硬合金の製法である。本発明の硬質粉末の酸素濃度は、０．０５から１．０重量％であることが好ましい。本願発明の構成を採用することによって、充填性、流動性に優れた特性を有する硬質粉末を得ることができる。 The present invention relates to a hard powder obtained by drying and granulating a slurry made of a raw material powder containing a combination of an aqueous solvent, tungsten carbide, and Co, and inevitable impurities. The hard powder has an average particle size of 30 to 80 μm and a bulk density of It is a hard powder characterized by 3.0 to 3.7 g / cm 3 and an average sphericity of 0.7 or more. Furthermore, in the tungsten carbide base cemented carbide, a slurry made of a raw material powder containing a water solvent, tungsten carbide, Co, and a combination of inevitable impurities is dried and granulated, and the average particle size of the hard powder is 30 to 80 μm, It is a method for producing a tungsten carbide-based cemented carbide comprising a hard powder granulated to have a bulk density of 3.0 to 3.7 g / cm 3 and an average sphericity of 0.7 or more. The oxygen concentration of the hard powder of the present invention is preferably 0.05 to 1.0% by weight. By adopting the configuration of the present invention, a hard powder having characteristics excellent in filling property and fluidity can be obtained.
本発明によって、粉末冶金法により炭化タングステン基超硬合金を製造する時に用いる硬質粉末が、充填性、流動性に優れた特性を有する硬質粉末を提供することができた。従って、造型工程の硬質粉末の流れ性が良くなるため、プレス体へのプレス圧力が均一となり密度が均一なプレス体が得られ、複雑形状であっても焼結後の亀裂や巣等の欠陥のない焼結体が得られるといった、工業的な有効性を発揮する。 According to the present invention, the hard powder used when producing a tungsten carbide-based cemented carbide by the powder metallurgy method can provide a hard powder having characteristics excellent in filling property and fluidity. Therefore, since the flowability of the hard powder in the molding process is improved, the press pressure to the press body is uniform, and a press body with a uniform density is obtained. It exhibits industrial effectiveness, such as obtaining a sintered body with no slag.
本発明の硬質粉末（以下、完粉と記す。）の平均粒径は、３０から８０μｍである。平均粒径が３０μｍ未満の時は、球体をした粉末状態の比率が減少する傾向にあり、殻状の粒子が増大して流動性に悪影響を及ぼし、造型工程では複雑形状の部位に粉末が充填されないといった不都合がある。一方、８０μｍを超えて大きい場合も同様に、複雑形状部位に粉末が充填されないという不都合の他に、粉末が硬くなりプレス時の圧力では潰れずに焼結後も粒子形状が残存して、空孔部が残留するといった弊害を生じるため不都合である。
本発明の完粉は、嵩密度を３．０から３．７ｇ／ｃｍ３の範囲に規定する。この範囲に規定することにより、造型工程での粉末充填性が安定する。また、原料粉末であるＷＣ硬質粒子が０．７μｍ以下の微粒子からなる微粒超硬合金について、従来は形状が複雑であることから、完粉の均一な圧縮成形が困難であったものに対しても、本発明の完粉は極めて有効である。
本発明の完粉は、平均球形度を０．７以上の範囲に規定する。完粉の平均球形度を０．７以上の範囲とすること、即ち、粉末の表面状態を凹凸、ポア、孔、割れ、空隙の殆ど見られず、更に殻状粒子などの不完全粒子の付着物が少なく、窪み形状も見られない様な、滑らかな状態とすることにより、粉末同士間の摩擦及び粉末と金型との摩擦を減ずる効果が現れる。平均球形度が０．７未満であると、充填性、流動性が劣るため成形性が悪化する。ここで、本発明の完粉の球形度を０．７以上にするには、スラリー溶媒の表面張力と粘性のバランスを制御する必要がある。本発明はスラリーの溶媒に水を使用し、この水が空気を表面流体とした時の表面張力は、略７０〜７５×１０−５Ｎ／ｃｍの範囲である。
The average particle size of the hard powder of the present invention (hereinafter referred to as complete powder) is 30 to 80 μm. When the average particle size is less than 30 μm, the ratio of the sphere-shaped powder tends to decrease, and the shell-shaped particles increase and adversely affect the fluidity. There is inconvenience that it is not done. On the other hand, in the case of larger than 80 μm, similarly, in addition to the inconvenience that the powder is not filled in the complicated shape part, the powder becomes hard and the particle shape remains after sintering without being crushed by the pressure during pressing. This is inconvenient because it causes a problem that the hole remains.
The finished powder of the present invention has a bulk density in the range of 3.0 to 3.7 g / cm 3 . By defining within this range, the powder filling property in the molding process is stabilized. In addition, for fine cemented carbides consisting of fine particles of WC hard particles of 0.7 μm or less as raw material powder, since the shape has been complicated in the past, it was difficult to uniformly compress the finished powder. However, the finished powder of the present invention is extremely effective.
The finished powder of the present invention has an average sphericity of 0.7 or more. The average sphericity of the finished powder should be in the range of 0.7 or more, that is, the surface state of the powder is almost free of irregularities, pores, holes, cracks and voids, and incomplete particles such as shell particles are attached. By making a smooth state such that there is little kimono and no dent shape is seen, the effect of reducing the friction between the powders and the friction between the powder and the mold appears. When the average sphericity is less than 0.7, the formability deteriorates because the filling property and fluidity are poor. Here, in order to make the sphericity of the finished powder of the present invention 0.7 or more, it is necessary to control the balance between the surface tension and the viscosity of the slurry solvent. In the present invention, water is used as the solvent for the slurry, and the surface tension when the water uses air as a surface fluid is in the range of about 70 to 75 × 10 −5 N / cm.
本発明の原料粉末をスラリーとして均一に分散させ、しかも本発明の規定する平均粒径が３０から８０μｍの完粉を得るには、水溶媒は適切な表面張力値の範囲にある。使用する溶媒は、イオン交換処理を施し、電気伝導度を調節した水（以下、イオン交換水と記す。）を使用することが好ましい。これは、完粉に混入する不純物成分を抑制し、また必要に応じて用いる造粒用添加剤の溶解度を安定化させるのに好都合である。イオン交換水を使用する時は、電気伝導度を３μＳ／ｃｍ以下とすることが好ましい。更に、上記の電気伝導度値を満たせば、蒸留水であっても良い。溶質である原料粉末が溶媒中に均一に分散し、適切な表面張力に制御したスラリーを用いて、例えば噴霧乾燥装置によって製造した完粉は、適切な表面張力によって粒化性が向上する。従って、不完全粒子の存在比率が低下して、球形度が０．７以上の完粉を得ることができる。粒化性が向上するため付着物が少なく、窪み形状も見られない。更に、球形度はスラリー溶媒の粘性による影響を受ける。粘性を高く設定すると粒化性が良くなり、球形度も改善する傾向を示す。しかし、スラリーの分散性が犠牲とならない範囲で設定する必要があることから、ここで溶媒の表面張力と粘性のバランスを制御することが必要となってくる。粘性値は温度の影響を受け、本発明で採用する水溶媒は、温度制御が可能な範囲内に適正な粘性値を有する溶媒である。
しかし、原料粉末の形態等によっては、スラリー溶媒の表面張力と粘性のバランスを制御するために、各種の造粒用添加剤を用いる場合も有り得る。表面張力を制御するために、例えば陽イオン、陰イオン、両性を示す表面活性剤の適用が考えられる。表面張力を低下させることで、分散性を向上させる効果がある。また、粘度を制御するために、例えば天然高分子材料を変性させた合成高分子材料として、親水基及び疎水基を持った材料の適用が考えられる。粘度を高めることで、粒化性を向上させる効果があるが一方で、完粉表面が硬化するためプレス成形時に粉末が適正な状態で潰れない現象が発生するので、注意を要する。両者のバランスを保つため、造粒用添加剤を併用することも可能である。
In order to uniformly disperse the raw material powder of the present invention as a slurry and to obtain a finished powder having an average particle size of 30 to 80 μm defined by the present invention, the aqueous solvent is in the range of an appropriate surface tension value. As the solvent to be used, it is preferable to use water (hereinafter referred to as ion-exchanged water) that has been subjected to ion exchange treatment and whose electric conductivity has been adjusted. This is advantageous for suppressing impurity components mixed in the finished powder and stabilizing the solubility of the granulating additive used as necessary. When ion-exchanged water is used, the electrical conductivity is preferably 3 μS / cm or less. Further, distilled water may be used as long as the above electric conductivity value is satisfied. For a finished powder produced by, for example, a spray drying apparatus using a slurry in which a raw material powder as a solute is uniformly dispersed in a solvent and is controlled to have an appropriate surface tension, the graininess is improved by the appropriate surface tension. Therefore, the existence ratio of incomplete particles is reduced, and a finished powder having a sphericity of 0.7 or more can be obtained. Since the granulation property is improved, there are few deposits and no dent shape is seen. Furthermore, the sphericity is affected by the viscosity of the slurry solvent. When the viscosity is set high, the graininess is improved and the sphericity tends to be improved. However, since it is necessary to set within a range where the dispersibility of the slurry is not sacrificed, it is necessary to control the balance between the surface tension and the viscosity of the solvent. The viscosity value is affected by the temperature, and the aqueous solvent used in the present invention is a solvent having an appropriate viscosity value within a temperature controllable range.
However, depending on the form of the raw material powder, various granulating additives may be used to control the balance between the surface tension and the viscosity of the slurry solvent. In order to control the surface tension, for example, application of a surfactant exhibiting cation, anion, or amphotericity can be considered. By reducing the surface tension, there is an effect of improving dispersibility. In order to control the viscosity, for example, a synthetic polymer material obtained by modifying a natural polymer material may be applied with a material having a hydrophilic group and a hydrophobic group. Increasing the viscosity has the effect of improving the graining property, but on the other hand, the finished powder surface is hardened, so that a phenomenon that the powder does not collapse in an appropriate state during press molding occurs. In order to maintain a balance between the two, it is possible to use a granulating additive in combination.
本発明の完粉の平均球形度は、１０００個以上の粒子像に関して、粒子像解析装置を用いて測定し、この測定値から算出することができる。まず、個々の完粉の球形度は、完粉の投影面積をＭとし、完粉の周囲長Ｌを測定する。Ｌに対応する真円の半径をｒとすると、Ｌ＝２πｒであることから、ｒ＝Ｌ／２πとなる。先に仮定した真円の面積をＰとすると、Ｐ＝Ｌ２／４πとなる。従って、球形度＝Ｍ／Ｐ＝Ｍ×４π／Ｌ２、として算出することができる。平均球形度は、平均球形度＝（Σ球形度）／ｎ、ここでｎ≧１０００、として算出することができる。 The average sphericity of the finished powder of the present invention can be calculated from a measured value obtained by measuring a particle image of 1000 or more using a particle image analyzer. First, for the sphericity of each finished powder, the projected area of the finished powder is M, and the peripheral length L of the finished powder is measured. If the radius of the perfect circle corresponding to L is r, then L = 2πr, so r = L / 2π. Assuming that the area of the perfect circle assumed earlier is P, P = L2 / 4π. Therefore, it can be calculated as sphericity = M / P = M × 4π / L2. The average sphericity can be calculated as average sphericity = (Σ sphericity) / n, where n ≧ 1000.
本発明の完粉の酸素濃度は０．０５から１．０重量％の範囲であることが好ましい。完粉の酸素濃度が１．０重量％を超えて大きいと、焼結時に周囲の元素との酸化反応が顕著となり焼結体の有孔度が劣化する事、更にＣが酸素と反応してＣ含有量の変動が顕著となるため不都合である。また、０．０５重量％未満とした理由は、既に原料粉末に含有される酸素濃度レベルを下限値とするのが適当であると考えたからである。
本発明の完粉を用いて作製した焼結体の有孔度分類が、ＣＩＳ規格によるＡ０２レベルよりも良好であることから、密度が均一な焼結体が得られる。例えば切削工具等に応用した場合、高硬度と耐欠損性に優れた切削工具が得られ、好ましい。
The oxygen concentration of the finished powder of the present invention is preferably in the range of 0.05 to 1.0% by weight. If the oxygen concentration of the finished powder exceeds 1.0% by weight, the oxidation reaction with surrounding elements becomes remarkable during sintering, and the porosity of the sintered body deteriorates. Further, C reacts with oxygen. This is inconvenient because the C content varies significantly. Further, the reason for setting it to less than 0.05% by weight is that it is considered appropriate to set the oxygen concentration level already contained in the raw material powder to the lower limit.
Since the porosity classification of the sintered body produced using the finished powder of the present invention is better than the A02 level according to the CIS standard, a sintered body having a uniform density can be obtained. For example, when applied to a cutting tool or the like, a cutting tool having high hardness and excellent fracture resistance is obtained, which is preferable.
本発明の完粉を得るための１手段として、噴霧乾燥造粒装置を用いたスラリーの乾燥造粒法がある。本発明の完粉を得るためには第１に、水溶媒と炭化タングステン、Ｃｏを含み、不可避不純物との組合せの原料粉末からなるスラリー状態での密度等を測定し、これと造粒特性との相関関係を予め把握しておき、湿式混合後であって乾燥造粒直前のスラリー粘度やスラリー濃度、スラリー密度等を管理、調整することが必要である。例えば、スラリーの固形粒子濃度は５０〜８５重量％の範囲で制御することが好ましい。第２に、噴霧乾燥して造粒を行う時の、スラリー噴霧ノズルの形態、スラリー供給量、乾燥温度、気流の速度等も制御することが必要である。これらの条件を制御することによって、本発明に規定した完粉の平均粒子径、嵩密度等の特性を得ることができる。例えば、液噴霧ノズルの形態は、スラリー供給量、スラリー粘度等の条件に応じて、加圧ノズル、ディスク式ノズル、２流体ノズル等の公知のノズルから適宜選択して用いることができる。流入するガス流量と温度は、添加した水分量を完全に蒸発させるに十分なエネルギーとなるように設定する。
本発明の完粉を得るためには、スラリーに水溶媒を使用していることから、乾燥温度は装置入口、出口、及び装置の幾何学的中間点の各温度プロファイルを制御することが重要である。例えば装置入口温度は１２５〜１９５度の範囲、出口温度は７５〜１００度の範囲、重力方向に対する装置の幾何学的な中間点の温度は７５〜１２５度の範囲となるように調整することが好ましい。更に、完粉の酸素濃度を本発明の規定値範囲内に制御するためには、装置下部の完粉取り出し口における完粉の温度を７５度以下に強制冷却することが好ましい。この時の強制冷却には、含有水分が少なく乾燥した空気、或いは不活性気体を用いるここがより好ましい形態である。
上記の完粉製造する方法において、η相やフリーカーボン含まない完粉を確実に製造するため、化学分析に基づき炭素バランスを調整する必要がある。例えば使用原料粉末の酸素量確認すること、必要に応じて炭素を添加すること、乾燥中の酸素供給量等の制御することによって調整は可能である。また、完粉の表面形態を滑らかな状態にして、流動性の優れた完粉を得るためには、噴霧装置入口での温度制御が大きな影響を与える。即ち、噴霧乾燥による造粒工程において、スラリーが高温気流中に噴霧される時に、水分の蒸発速度が早過ぎると正常な球形状とならないからである。一方で水分の蒸発速度が遅くなりすぎると、乾燥が不十分となってしまうので注意が必要である。本発明では上記の様な項目を考慮して各条件を設定した。
One means for obtaining the finished powder of the present invention is a slurry dry granulation method using a spray drying granulator. In order to obtain the complete powder of the present invention, first, the density in a slurry state comprising a raw material powder in combination with an aqueous solvent, tungsten carbide, Co, and inevitable impurities is measured, and this and granulation characteristics It is necessary to grasp the correlation in advance and manage and adjust the slurry viscosity, slurry concentration, slurry density and the like immediately after wet mixing and immediately before dry granulation. For example, the solid particle concentration of the slurry is preferably controlled in the range of 50 to 85% by weight. Secondly, it is necessary to control the form of the slurry spray nozzle, the amount of slurry supplied, the drying temperature, the speed of the air flow, etc. when granulating by spray drying. By controlling these conditions, characteristics such as the average particle diameter and bulk density of the finished powder defined in the present invention can be obtained. For example, the form of the liquid spray nozzle can be appropriately selected from known nozzles such as a pressure nozzle, a disk-type nozzle, and a two-fluid nozzle according to conditions such as the slurry supply amount and slurry viscosity. The flow rate and temperature of the inflowing gas are set so as to have sufficient energy to completely evaporate the added water amount.
In order to obtain the finished powder of the present invention, since the aqueous solvent is used in the slurry, it is important that the drying temperature controls the temperature profile of the apparatus inlet, outlet, and the geometric intermediate point of the apparatus. is there. For example, the apparatus inlet temperature may be adjusted to be in the range of 125 to 195 degrees, the outlet temperature may be in the range of 75 to 100 degrees, and the temperature at the geometric intermediate point of the apparatus with respect to the direction of gravity may be in the range of 75 to 125 degrees. preferable. Furthermore, in order to control the oxygen concentration of the complete powder within the specified value range of the present invention, it is preferable to forcibly cool the temperature of the complete powder at the complete powder takeout port at the lower part of the apparatus to 75 degrees or less. The forced cooling at this time is a more preferable form using dry air with little water content or inert gas.
In the above method for producing a finished powder, it is necessary to adjust the carbon balance based on chemical analysis in order to reliably produce a finished powder that does not contain η phase or free carbon. For example, adjustment is possible by confirming the amount of oxygen in the raw material powder used, adding carbon as necessary, and controlling the amount of oxygen supplied during drying. In addition, temperature control at the inlet of the spraying device has a great influence in order to obtain a finished powder having a smooth state and a finished powder having excellent fluidity. That is, in the granulation process by spray drying, when the slurry is sprayed in a high temperature air stream, if the moisture evaporation rate is too fast, a normal spherical shape is not obtained. On the other hand, if the moisture evaporation rate is too slow, the drying will be insufficient. In the present invention, each condition is set in consideration of the above items.
本発明において、スラリーに水溶媒を採用した他の理由は、環境汚染物の排除に考慮したものでもある。アセトン、アルコール、ヘキサン又はヘプタン等の有機溶剤をスラリー溶媒として用いる大きな欠点は、溶剤の可燃性と揮発性の高い点にある。たとえリサイクル対策を施したとしても高い揮発性を有することから大気中に蒸散し、大幅な回収量減となる。更に、アトライターや噴霧乾燥装置は、防爆型の装置とする必要があることから安全工学的に高度な技術が要求され、窒素ガスなどの不活性ガスの雰囲気下で乾燥させなければならない。その結果としてコストが高くなり、工業的な不利益を免れない。本発明は、この点からも工業的に有効であり好ましい。上記の様に本発明の実施の形態について述べたが、本発明はこれらの実施の形態になんら限定されて解釈されるべきものではない。以下の実施例においても、本発明の範囲を逸脱しない限りにおいて、当業者の知識に基づいて種々の変更、修正、改良等を加え得るものである。 In the present invention, another reason for adopting a water solvent in the slurry is also in consideration of elimination of environmental pollutants. A major drawback of using an organic solvent such as acetone, alcohol, hexane or heptane as the slurry solvent is that the solvent is highly flammable and volatile. Even if recycle measures are taken, it has high volatility and will evaporate into the atmosphere, resulting in a significant reduction in the amount recovered. Furthermore, since it is necessary to make an attritor and a spray drying apparatus into an explosion-proof type apparatus, advanced technology is required in terms of safety engineering, and the apparatus must be dried in an atmosphere of an inert gas such as nitrogen gas. As a result, the cost becomes high and industrial disadvantages cannot be avoided. The present invention is also industrially effective and preferable from this point. Although the embodiments of the present invention have been described as described above, the present invention should not be construed as being limited to these embodiments. Also in the following examples, various changes, modifications, improvements and the like can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention.
原料粉末は、平均粒径が４．５μｍのＷＣ粉末と９ｗｔ％のＣｏ粉末、７ｗｔ％のＴａＣを配合比率に秤量し、該原料粉末に、電気伝導度を３μＳ／ｃｍ以下に調節したイオン交換水の溶媒と造粒用添加剤等を所定の比率で加えて湿式混合した後、該スラリーを噴霧乾燥法により造粒し、本発明例１から４の完粉を得た。この時のスラリーの固形粒子濃度は６５重量％とし、装置入口温度は１７０度、出口温度は９５度、中間点の温度は１１５度、完粉取り出し口における完粉の温度を６０度になるように設定した。一方、比較のため、スラリー溶媒をイオン交換水に代えてアルコールを使用したスラリーを準備し、スラリーの固形粒子濃度は同一条件に揃えた。出口温度は７０度〜９０度に設定して、比較例５、６の完粉を得た。得られた完粉の流動度は、形状がＪＩＳＺ−２５０４で規定される測定用漏斗を使用し、オリフィス直径が２．６ｍｍの条件で測定した。測定結果を表１に示す。 The raw material powder is an ion exchange in which an average particle size of 4.5 μm WC powder, 9 wt% Co powder, and 7 wt% TaC are weighed in a blending ratio, and the electric conductivity is adjusted to 3 μS / cm or less. A water solvent and a granulating additive were added at a predetermined ratio and wet-mixed, and the slurry was granulated by a spray drying method to obtain finished powders of Examples 1 to 4 of the present invention. At this time, the solid particle concentration of the slurry is 65% by weight, the apparatus inlet temperature is 170 degrees, the outlet temperature is 95 degrees, the midpoint temperature is 115 degrees, and the temperature of the finished powder at the finished powder outlet is 60 degrees. Set to. On the other hand, for comparison, a slurry using alcohol was prepared by replacing the slurry solvent with ion-exchanged water, and the solid particle concentration of the slurry was adjusted to the same condition. The exit temperature was set to 70 to 90 degrees to obtain finished powders of Comparative Examples 5 and 6. The fluidity of the obtained powder was measured under the condition that the orifice diameter was 2.6 mm using a measuring funnel whose shape was defined by JISZ-2504. The measurement results are shown in Table 1.
焼結体の評価のために、４×８×２５ｍｍ棒状材の合金試片を作製し、内部の有孔度分類及び抗折力を測定した。有孔度分類はＣＩＳ規格（超硬工具協会規格、ＣＩＳ−００６Ｂ）による。試験条件としては、超硬合金製ダイ及び同上下パンチで油圧式にて圧力１００ＭＰａでプレスして成形体とし、焼結条件は、真空雰囲気中、１３３０から１４７０度の温度で、３０分焼結した。表１の抗折強度は４×８×２５ｍｍ棒状材のスパン２０ｍｍ、３点曲げ強度試験の結果を示す。 For the evaluation of the sintered body, 4 × 8 × 25 mm rod-shaped alloy specimens were prepared, and the internal porosity classification and the bending strength were measured. The porosity classification is based on the CIS standard (Carbide Tool Association standard, CIS-006B). As test conditions, a cemented carbide die and upper and lower punches were pressed hydraulically at a pressure of 100 MPa to form a compact, and the sintering conditions were sintering in a vacuum atmosphere at a temperature of 1330 to 1470 degrees for 30 minutes. did. The bending strength in Table 1 shows the results of a 4 × 8 × 25 mm rod-like material with a span of 20 mm and a three-point bending strength test.
完粉の表面状態は、走査型電子顕微鏡（（株）日立製作所製Ｓ−４２００）を用いて、倍率３５０倍で観察した。観察結果を図１、２に示す。図１はイオン交換水を溶媒とする本発明例１の完粉であり、図２のアルコールを溶媒とした比較例５の完粉に比べ、平均球形度が０．７以上の平滑な表面状態となっている。これはイオン交換水の溶媒を用いたスラリー中の原料粒子の分散性が良く、噴霧乾燥工程において、中実性が高く緻密質な表面層を形成するのに対し、アルコール溶媒の場合には原料粒子同士が凝集粒子となり、噴霧乾燥工程において粒子移動が起こりにくくなり、中空性であって密度が低く、表面は微視的な凹凸が形成されたためである。一般的にイオン交換水の溶媒を用いた分散性の良いスラリーは完粉表面に窪みを有する傾向を示し、これが焼結体の製品欠陥を招く要因でもあることから注意を要するのであるが、本発明例は適切なスラリー性状に制御されたことにより、健全な形状をした完粉を得ることができた。本発明の完粉を用いた焼結体組織の観察においても、有孔度分類は改善され、空孔等は殆ど見られず、高密度な焼結体が得られた。 The surface state of the finished powder was observed at a magnification of 350 times using a scanning electron microscope (S-4200, manufactured by Hitachi, Ltd.). The observation results are shown in FIGS. FIG. 1 shows the finished powder of Invention Example 1 using ion-exchanged water as a solvent, and a smooth surface state having an average sphericity of 0.7 or more compared to the finished powder of Comparative Example 5 using the alcohol of FIG. 2 as a solvent. It has become. This has good dispersibility of the raw material particles in the slurry using ion-exchanged water solvent, and forms a dense and dense surface layer in the spray drying process, whereas in the case of an alcohol solvent, the raw material is formed. This is because the particles become agglomerated particles, particle movement is less likely to occur in the spray-drying process, it is hollow and has a low density, and microscopic irregularities are formed on the surface. In general, a slurry with good dispersibility using a solvent of ion-exchanged water tends to have dents on the surface of the finished powder, and this is a factor that causes product defects in the sintered body. The invention example was able to obtain a complete powder having a healthy shape by being controlled to an appropriate slurry property. Also in the observation of the sintered body structure using the finished powder of the present invention, the porosity classification was improved, almost no voids were observed, and a high-density sintered body was obtained.
Claims (3)
In a tungsten carbide-based cemented carbide, a slurry made of a raw material powder containing a water solvent, tungsten carbide, and Co, in combination with inevitable impurities, is dried and granulated, the average particle size of the hard powder is 30 to 80 μm, and the bulk density Of tungsten carbide based cemented carbide, characterized in that it is produced using a hard powder granulated with an average sphericity of 0.7 to 3.7 g / cm 3 .
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010096004A1 (en) * | 2009-02-19 | 2010-08-26 | Seco Tools Ab | Fine grained cemented carbide powder mixture with low sintering shrinkage and method of making the same |
| WO2016152364A1 (en) * | 2015-03-24 | 2016-09-29 | Ntn株式会社 | Magnetic core powder, dust core, and method for producing magnetic core powder |
| CN120864505A (en) * | 2025-09-10 | 2025-10-31 | 成都大光新材料有限公司 | Wear-resistant tungsten carbide powder and preparation method thereof |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010096004A1 (en) * | 2009-02-19 | 2010-08-26 | Seco Tools Ab | Fine grained cemented carbide powder mixture with low sintering shrinkage and method of making the same |
| WO2016152364A1 (en) * | 2015-03-24 | 2016-09-29 | Ntn株式会社 | Magnetic core powder, dust core, and method for producing magnetic core powder |
| JP2016180154A (en) * | 2015-03-24 | 2016-10-13 | Ntn株式会社 | Powder for magnetic core, dust core, and method for producing powder for magnetic core |
| CN107405686A (en) * | 2015-03-24 | 2017-11-28 | Ntn株式会社 | The manufacture method of magnetic core powder and compressed-core and magnetic core powder |
| CN107405686B (en) * | 2015-03-24 | 2019-09-17 | Ntn株式会社 | The manufacturing method of magnetic core powder and compressed-core and magnetic core powder |
| CN120864505A (en) * | 2025-09-10 | 2025-10-31 | 成都大光新材料有限公司 | Wear-resistant tungsten carbide powder and preparation method thereof |
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