JP6765177B2 - Manufacturing method of porous metal parts - Google Patents
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本発明は、多孔質金属部品の製造方法に関する。 The present invention relates to a method for manufacturing a porous metal part.
周知のように、無数の内部空孔（連続気孔、連通孔）を有する多孔質の金属部品は、例えば、軸受（特にすべり軸受）、異物を捕捉しつつ流体を通過させるフィルタなどとして広く使用されている。多孔質金属部品は、主に、金属粉末を主成分とした原料粉末の圧粉体を得る成形工程と、圧粉体に高強度化処理を施す高強度化処理工程とを経ることで得られる。上記の高強度化処理としては、例えば、圧粉体を金属粉末の焼結温度以上で加熱することにより、金属粉末の粒子同士をネック結合させる焼結処理、あるいは、大気等の酸化性雰囲気中で圧粉体を加熱することによって金属粉末の粒子表面に酸化皮膜（酸化物皮膜）を形成し、この酸化皮膜を介して粒子同士を結合させる皮膜形成処理などが採用される。 As is well known, porous metal parts having innumerable internal pores (continuous pores, communication holes) are widely used as, for example, bearings (particularly plain bearings), filters that allow fluid to pass through while capturing foreign matter, and the like. ing. Porous metal parts are mainly obtained through a molding step of obtaining a green compact of a raw material powder containing a metal powder as a main component and a high-strength treatment step of applying a high-strength treatment to the green compact. .. The above-mentioned high-strength treatment includes, for example, a sintering treatment in which particles of the metal powder are neck-bonded by heating the green compact at a temperature equal to or higher than the sintering temperature of the metal powder, or in an oxidizing atmosphere such as the atmosphere. An oxide film (oxide film) is formed on the surface of the particles of the metal powder by heating the green compact, and a film forming process for bonding the particles to each other through the oxide film is adopted.
上記の原料粉末は、通常、主成分粉末としての金属粉末と、この金属粉末に添加・混合された粉末状の固体潤滑剤（潤滑剤粉末）とを含む。このように、原料粉末に潤滑剤粉末を含めておけば、金属粉末と成形金型の間、および金属粉末の粒子相互間における潤滑性を担保し、圧粉体の成形性を高めることができる。但し、使用する潤滑剤粉末の粒径が大きくなるほど、原料粉末中における潤滑剤粉末の分散性が低下するため、所望の潤滑性を担保できなくなる可能性がある。そのため、潤滑剤粉末としては、金属粉末に比べて微細なもの、具体的には平均粒径２０μｍ未満のものを使用するのが一般的である。 The above raw material powder usually includes a metal powder as a main component powder and a powdery solid lubricant (lubricant powder) added / mixed with the metal powder. In this way, if the raw material powder contains the lubricant powder, the lubricity between the metal powder and the molding die and between the particles of the metal powder can be ensured, and the moldability of the green compact can be improved. .. However, as the particle size of the lubricant powder used increases, the dispersibility of the lubricant powder in the raw material powder decreases, so that the desired lubricity may not be ensured. Therefore, as the lubricant powder, it is common to use a lubricant powder that is finer than the metal powder, specifically, a lubricant powder having an average particle size of less than 20 μm.
ところで、多孔質金属製のすべり軸受においては、内部空孔が潤滑油を保持するための保油部として機能し、また、多孔質金属製のフィルタにおいては、内部空孔が流体の流路として機能する。このため、多孔質金属部品は、高い空孔率（例えば、１０ｖｏｌ％を超える空孔率）を有することが必要とされる場合もある。多孔質金属部品の空孔率を高めるための技術手段として、圧粉体を低密度に成形することが考えられるが、この場合、圧粉体が欠損等し易くなり、圧粉体の取り扱いに格別の配慮を要する他、多孔質金属部品に必要とされる強度を確保できない可能性が高まる。 By the way, in the porous metal slide bearing, the internal pores function as an oil retaining part for holding the lubricating oil, and in the porous metal filter, the internal pores serve as a fluid flow path. Function. For this reason, the porous metal part may be required to have a high porosity (for example, a porosity of more than 10 vol%). As a technical means for increasing the porosity of porous metal parts, it is conceivable to mold the green compact at a low density, but in this case, the green compact is likely to be chipped, and the green compact can be handled easily. In addition to requiring special consideration, there is a high possibility that the strength required for porous metal parts cannot be secured.
そこで、高い空孔率および必要強度を兼ね備えた多孔質金属部品を得るため、例えば下記の特許文献１には、原料粉末の圧粉体を焼結することで焼結軸受を製造するにあたり、粒度３２５メッシュ以下の微細粉を３０〜６０％含有する銅粉末に対し、潤滑剤粉末としての金属石けんを３〜７％添加してなる原料粉末を用いることが開示されている。 Therefore, in order to obtain a porous metal part having both a high porosity and a required strength, for example, in Patent Document 1 below, when a sintered bearing is manufactured by sintering a green compact of raw material powder, the particle size is increased. It is disclosed that a raw material powder obtained by adding 3 to 7% of metal soap as a lubricant powder to a copper powder containing 30 to 60% of fine powder of 325 mesh or less is used.
しかしながら、特許文献１の技術手段は、使用可能な金属粉末の種類や組成が極めて限定的であるため、汎用性・実用性に欠けるという問題がある。 However, the technical means of Patent Document 1 has a problem that it lacks versatility and practicality because the types and compositions of metal powders that can be used are extremely limited.
このような実情に鑑み、本発明の課題は、使用する金属粉末の種類や組成に制限を加えずとも、高い空孔率と必要強度を兼ね備えた多孔質金属部品を作製可能とすることにある。 In view of such circumstances, an object of the present invention is to make it possible to produce a porous metal part having a high porosity and a required strength without limiting the type and composition of the metal powder to be used. ..
本発明者らは、高精度の圧粉体、ひいては多孔質金属部品を作製する上で必要不可欠な潤滑剤粉末を、圧粉体の成形性を高めるための潤滑剤としてのみならず、造孔材（空孔形成材）として活用することを着想し、この着想に基づいて鋭意検討を重ねた結果、本発明を完成するに至った。 The present inventors use the lubricant powder, which is indispensable for producing high-precision green compacts and, by extension, porous metal parts, not only as a lubricant for improving the moldability of the green compact, but also for forming holes. The idea of using it as a material (pore forming material) was conceived, and as a result of diligent studies based on this idea, the present invention was completed.
すなわち、上記の課題を解決するために創案された本発明は、１０ｖｏｌ％を超える空孔率を有する多孔質金属部品を製造するための方法であって、金属粉末に潤滑剤粉末を添加してなる原料粉末の圧粉体を成形する成形工程と、加熱を伴う高強度化処理を圧粉体に施す高強度化処理工程と、を有し、潤滑剤粉末として、分解温度が高強度化処理の処理温度以下であると共に、平均粒径が２０μｍ以上２００μｍ未満のものを使用することを特徴とする。なお、ここでいう「空孔率」とは、空孔体積の総和を多孔質金属部品の体積で除した値の百分率をいう。 That is, the present invention, which was devised to solve the above problems, is a method for producing a porous metal part having a pore ratio of more than 10 vol%, and is obtained by adding a lubricant powder to the metal powder. It has a molding step of molding a green compact of the raw material powder and a high-strength treatment step of applying a high-strength treatment accompanied by heating to the green compact, and the decomposition temperature is high-strength treatment as a lubricant powder. It is characterized in that the powder having an average particle size of 20 μm or more and less than 200 μm is used as well as the treatment temperature of The "vacancy ratio" here means a percentage of the value obtained by dividing the total volume of the pores by the volume of the porous metal part.
上記構成によれば、高強度化処理の実施に伴って、圧粉体中に点在していた潤滑剤粉末が分解・除去されるため、圧粉体中の潤滑剤粉末が点在していた箇所に新たに空孔が形成される。ここで、潤滑剤粉末の平均粒径が２０μｍ未満の場合には、高強度化処理の実施に伴う金属粉末の熱膨張等の影響により、多孔質金属部品の空孔率向上に有効に寄与し得るような径を有する空孔を確実に形成することができない。これに対し、平均粒径が２０μｍ以上の潤滑剤粉末を選択使用すれば、上記態様で形成される空孔が金属粉末の熱膨張等の影響によって収縮等しても、多孔質金属部品の空孔率向上に有効に寄与する。但し、平均粒径が過度に大きい潤滑剤粉末（具体的には、平均粒径が２００μｍ以上の潤滑剤粉末）を使用すると、潤滑剤粉末が本来的に発揮すべき潤滑機能を発揮できないばかりか、新たに形成される空孔も過度に大きい粗大空孔となり易いため多孔質金属部品の強度低下を招来する可能性がある。従って、分解温度が高強度化処理の処理温度以下であると共に、平均粒径が２０μｍ以上２００μｍ未満の潤滑剤粉末を選択的に使用すれば、使用する金属粉末の種類や組成に制限を加えずとも、高い空孔率と必要強度を兼ね備えた多孔質金属部品を得ることができる。 According to the above configuration, the lubricant powder scattered in the green compact is decomposed and removed with the implementation of the high-strength treatment, so that the lubricant powder in the green compact is scattered. A new hole is formed at the location. Here, when the average particle size of the lubricant powder is less than 20 μm, it effectively contributes to the improvement of the porosity of the porous metal part due to the influence of the thermal expansion of the metal powder accompanying the implementation of the high strength treatment. It is not possible to reliably form a pore having a diameter that can be obtained. On the other hand, if a lubricant powder having an average particle size of 20 μm or more is selectively used, even if the pores formed in the above embodiment shrink due to the influence of thermal expansion of the metal powder, the porous metal parts become empty. Effectively contributes to improving the pore ratio. However, if a lubricant powder having an excessively large average particle size (specifically, a lubricant powder having an average particle size of 200 μm or more) is used, not only does the lubricant powder not exhibit the lubricating function that it should originally exhibit. Since the newly formed pores are also likely to be excessively large coarse pores, the strength of the porous metal part may be reduced. Therefore, if the decomposition temperature is equal to or lower than the treatment temperature for the high-strength treatment and the lubricant powder having an average particle size of 20 μm or more and less than 200 μm is selectively used, the type and composition of the metal powder to be used are not restricted. In both cases, it is possible to obtain a porous metal part having both a high porosity and a required strength.
上記構成において、金属粉末に対する潤滑剤粉末の添加量は、０．３質量％以上３質量％未満とするのが好ましい。 In the above configuration, the amount of the lubricant powder added to the metal powder is preferably 0.3% by mass or more and less than 3% by mass.
成形工程と、高強度化処理工程との間には、圧粉体を高強度化処理の処理温度よりも低い温度で加熱する脱脂処理工程を設けても良く、この場合、潤滑剤粉末としては、分解温度が脱脂処理工程における圧粉体の加熱温度よりも低いものを使用するのが好ましい。このようにすれば、潤滑剤粉末に由来する残渣物が多孔質金属部品の内部に残存するのを効果的に防止することができるので、高品質の多孔質金属部品を得る上で有利となる。 A degreasing treatment step of heating the green compact at a temperature lower than the treatment temperature of the high strength treatment may be provided between the molding step and the high strength treatment step. In this case, the lubricant powder may be used. It is preferable to use one having a decomposition temperature lower than the heating temperature of the green compact in the degreasing treatment step. By doing so, it is possible to effectively prevent the residue derived from the lubricant powder from remaining inside the porous metal part, which is advantageous in obtaining a high-quality porous metal part. ..
加熱を伴う高硬度化処理としては、圧粉体を金属（金属粉末）の焼結温度以上で加熱する焼結処理を採用することができる。この場合、金属粉末の粒子同士がネック結合することによって高強度化した圧粉体（このような圧粉体は、一般的に「焼結体」と称される）を得ることができる。 As the hardness increasing treatment accompanied by heating, a sintering treatment in which the green compact is heated at a temperature equal to or higher than the sintering temperature of the metal (metal powder) can be adopted. In this case, it is possible to obtain a green compact (such a green compact is generally referred to as a "sintered material") having high strength by neck-bonding the particles of the metal powder to each other.
また、加熱を伴う高強度化処理としては、金属粉末の粒子表面に酸化皮膜を形成する皮膜形成処理を採用することもできる。この場合、酸化皮膜を介して金属粉末の粒子同士が結合することによって高強度化した圧粉体を得ることができる。 Further, as the strength increasing treatment accompanied by heating, a film forming treatment for forming an oxide film on the particle surface of the metal powder can also be adopted. In this case, it is possible to obtain a green compact having high strength by binding the particles of the metal powder to each other through the oxide film.
以上より、本発明によれば、使用する金属粉末の種類や組成に制限を加えずとも、高い空孔率と必要強度を兼ね備えた多孔質金属部品を作製することが可能となる。 From the above, according to the present invention, it is possible to produce a porous metal part having a high porosity and a required strength without limiting the type and composition of the metal powder to be used.
以下、本発明の実施の形態を図面に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
本発明に係る多孔質金属部品の製造方法は、例えば、図１に示すように、内周に挿入した軸Ｓをラジアル方向に支持するためのすべり軸受１、より具体的には、無数の内部空孔２を有し、空孔率が１０ｖｏｌ％を超えた多孔質金属製のすべり軸受１を製造する際に適用される。このすべり軸受１は、その多孔質組織（無数の内部空孔２）に潤滑油を含浸させた、いわゆる含油状態で使用される。従って、例えば、支持すべき軸Ｓが回転すると、これに伴って、すべり軸受１の内部空孔２に含浸させた潤滑油がすべり軸受１の内周面と軸Ｓの外周面との間の軸受隙間（ラジアル軸受隙間）に滲み出して油膜を形成し、この油膜を介して軸Ｓがラジアル方向に回転自在に支持される。 The method for manufacturing a porous metal part according to the present invention is, for example, as shown in FIG. 1, a slide bearing 1 for supporting a shaft S inserted in the inner circumference in the radial direction, and more specifically, innumerable internal parts. It is applied when manufacturing a slide bearing 1 made of a porous metal having pores 2 and having a pore ratio exceeding 10 vol%. The plain bearing 1 is used in a so-called oil-containing state in which its porous structure (innumerable internal pores 2) is impregnated with lubricating oil. Therefore, for example, when the shaft S to be supported rotates, the lubricating oil impregnated in the internal pores 2 of the slide bearing 1 is impregnated between the inner peripheral surface of the slide bearing 1 and the outer peripheral surface of the shaft S. An oil film is formed by exuding into the bearing gap (radial bearing gap), and the shaft S is rotatably supported in the radial direction through the oil film.
上記のすべり軸受１は、焼結金属の多孔質体からなる。すなわち、このすべり軸受１において、内部空孔２は、ネック結合した金属粉末の粒子３相互間に形成されている。このようなすべり軸受１は、例えば、成形工程、高強度化処理工程としての焼結工程、整形工程および含油工程を順に経て作製される。以下、上記の各工程について詳細に説明する。 The above-mentioned slide bearing 1 is made of a porous body of sintered metal. That is, in the slide bearing 1, the internal pores 2 are formed between the neck-bonded metal powder particles 3. Such a slide bearing 1 is manufactured through, for example, a molding step, a sintering step as a strength-enhancing treatment step, a shaping step, and an oil-impregnating step in this order. Hereinafter, each of the above steps will be described in detail.
成形工程では、例えば、一軸加圧成形法で金属粉末を主成分とした原料粉末を圧縮することにより、すべり軸受１の基材となる円筒状の圧粉体を得る。このとき、成形金型、および原料粉末の少なくとも一方を加熱した状態で原料粉末を圧縮するようにしても良いし、成形金型として、特に粉末充填部（キャビティ）の内壁面が、潤滑性に富む硬質皮膜（例えば、ＤＬＣ膜や、ＣｒＮ、ＴｉＮなどの窒化膜）で被覆されたものを用いるようにしても良い。 In the molding step, for example, a raw material powder containing a metal powder as a main component is compressed by a uniaxial pressure molding method to obtain a cylindrical green compact to be a base material of the slide bearing 1. At this time, the raw material powder may be compressed while at least one of the molding mold and the raw material powder is heated, and the inner wall surface of the molding mold, particularly the powder filling portion (cavity), becomes lubricious. A material coated with a rich hard film (for example, a DLC film or a nitride film such as CrN or TiN) may be used.
なお、圧粉体は、一軸加圧成形法以外の手法で得ることも可能である。具体的には、多軸ＣＮＣプレスによる成形、射出成形（ＭＩＭ）、あるいは冷間静水圧加圧法（ＣＩＰ）などを利用して圧粉体を得るようにしても良い。 The green compact can also be obtained by a method other than the uniaxial pressure molding method. Specifically, a green compact may be obtained by using molding by a multi-axis CNC press, injection molding (MIM), cold hydrostatic pressure (CIP), or the like.
ここで、原料粉末としては、金属粉末を主成分とし、これに所定量の潤滑剤粉末を添加・混合したものが使用される。金属粉末としては、焼結可能なものであれば問題なく使用することができ、例えば、鉄、銅、アルミニウム等の群から選択される何れか一種の金属を主成分とする粉末を使用することができる。金属粉末は、一種のみを使用しても良いし、二種以上を混合して使用しても良い。また、使用する金属粉末の製法も特に問わない。すなわち、例えば、ガスアトマイズや水アトマイズ等のアトマイズ法により製造されるアトマイズ粉末、還元法により製造される還元粉末、電解法により製造される電解粉末、カルボニル法により製造されるカルボニル粉末などが使用できる。なお、金属粉末として鉄粉末を使用する場合には、多孔質状をなし、かつ表面に比較的大きな凹凸を有する還元鉄粉を使用するのが好ましい。すべり軸受１をはじめとする多孔質金属部品の空孔率（含油率）および強度向上を図る上で有利となるからである。 Here, as the raw material powder, a metal powder is used as a main component, and a predetermined amount of lubricant powder is added / mixed thereto. As the metal powder, any sinterable powder can be used without any problem. For example, a powder containing any kind of metal selected from the group of iron, copper, aluminum and the like as a main component should be used. Can be done. As the metal powder, only one kind may be used, or two or more kinds may be mixed and used. Further, the manufacturing method of the metal powder used is not particularly limited. That is, for example, atomizing powder produced by an atomizing method such as gas atomizing or water atomizing, reducing powder produced by a reducing method, electrolytic powder produced by an electrolytic method, carbonyl powder produced by a carbonyl method, or the like can be used. When iron powder is used as the metal powder, it is preferable to use reduced iron powder which is porous and has relatively large irregularities on the surface. This is because it is advantageous in improving the porosity (oil content) and strength of the porous metal parts such as the slide bearing 1.
潤滑剤粉末としては、後述する高強度化処理工程（焼結工程）の処理温度で分解（熱分解）するもの、すなわち、分解温度が高強度化処理の処理温度以下のものを使用する。具体的には、例えば、ステアリン酸アルミニウムやステアリン酸亜鉛等の金属石けん、脂肪酸、高級アルコール、グリセリン、エステル、アミンおよびその誘導体、脂肪酸アミドなどのワックス、各種樹脂などが使用できる。上記の潤滑剤粉末は、一種のみを使用しても良いし、二種以上を混合して使用しても良い。但し、潤滑剤粉末としては、比較的大粒径のもの、具体的には平均粒径が２０μｍ以上２００μｍ未満のものを使用する。これは、潤滑剤粉末を、成形金型装置に対する原料粉末の充填、原料粉末の圧縮（圧粉体の成形）および圧粉体の離型という一連の圧粉体成形プロセスにおける潤滑性確保だけではなく、空孔形成材としても有効に活用するためである。また、金属粉末に対する潤滑剤粉末の添加量は、０．３質量％以上３質量％未満とする。 As the lubricant powder, one that decomposes (thermally decomposes) at the treatment temperature of the high-strength treatment step (sintering step) described later, that is, one whose decomposition temperature is equal to or lower than the treatment temperature of the high-strength treatment is used. Specifically, for example, metal soaps such as aluminum stearate and zinc stearate, fatty acids, higher alcohols, glycerin, esters, amines and derivatives thereof, waxes such as fatty acid amides, and various resins can be used. As the above-mentioned lubricant powder, only one kind may be used, or two or more kinds may be mixed and used. However, as the lubricant powder, one having a relatively large particle size, specifically, one having an average particle size of 20 μm or more and less than 200 μm is used. This is not only to ensure the lubricity of the lubricant powder in a series of green compact molding processes such as filling the raw material powder into the molding mold device, compressing the raw material powder (molding the green compact), and releasing the green compact. This is because it is effectively used as a pore-forming material. The amount of the lubricant powder added to the metal powder is 0.3% by mass or more and less than 3% by mass.
上記の圧縮工程で得られた圧粉体は、高強度化処理工程としての焼結工程において、加熱を伴う高強度化処理（ここでは焼結処理）が施される。焼結処理は、所定の雰囲気下に置かれた圧粉体を金属粉末の焼結温度以上（使用する金属粉末の種類や組成によって変わるが、一般的には８００℃以上）で所定時間加熱することにより行われる。これにより、金属粉末の粒子同士がネック結合した焼結体が得られる。なお、焼結処理は、例えば、ヒータが設置された焼結ゾーンと、自然放熱を行う冷却ゾーンとが連続的に設けられた連続焼結炉を用いて実施することができる。 The green compact obtained in the above compression step is subjected to a high strength treatment (here, a sintering treatment) accompanied by heating in the sintering step as the high strength treatment step. In the sintering process, the green compact placed in a predetermined atmosphere is heated at a temperature equal to or higher than the sintering temperature of the metal powder (generally 800 ° C or higher, although it varies depending on the type and composition of the metal powder used) for a predetermined time. It is done by. As a result, a sintered body in which the particles of the metal powder are neck-bonded to each other can be obtained. The sintering process can be carried out using, for example, a continuous sintering furnace in which a sintering zone in which a heater is installed and a cooling zone in which natural heat is dissipated are continuously provided.
整形工程では、焼結体を完成品形状に仕上げるための整形加工が実施される。整形加工としては、例えば、相対的な昇降移動が可能に同軸配置されたダイ、コアおよび上下パンチを有するサイジング金型を用いて焼結体の内径面および外径面のそれぞれをコアの外径面およびダイの内径面に倣わせて変形させる、いわゆるサイジングを採用することができる。最後に、完成品形状に仕上げられた焼結体は含油工程において、内部空孔に潤滑油を含浸させる含油処理に供される。これにより、図１に示す、多孔質金属部品としてのすべり軸受１が完成する。 In the shaping process, shaping is performed to finish the sintered body into a finished product shape. As the shaping process, for example, using a sizing die having a die, a core, and upper and lower punches coaxially arranged so as to be able to move up and down relative to each other, the inner diameter surface and the outer diameter surface of the sintered body are each formed into the outer diameter of the core. So-called sizing, in which the surface and the inner diameter surface of the die are deformed, can be adopted. Finally, the sintered body finished in the finished product shape is subjected to an oil impregnation treatment in which the internal pores are impregnated with lubricating oil in the oil impregnation step. As a result, the slide bearing 1 as a porous metal part shown in FIG. 1 is completed.
以上で説明したように、本実施形態では、焼結金属製のすべり軸受１を得るための原料粉末として、分解温度が圧粉体を高強度化するための高強度化処理の処理温度以下（ここでは焼結温度以下）であると共に、平均粒径が２０μｍ以上２００μｍ未満の潤滑剤粉末を含むものが使用される。 As described above, in the present embodiment, as the raw material powder for obtaining the plain bearing 1 made of sintered metal, the decomposition temperature is equal to or lower than the processing temperature of the high-strength treatment for increasing the strength of the green compact ( Here, those containing a lubricant powder having an average particle size of 20 μm or more and less than 200 μm are used as well as having a sintering temperature or less).
このようにすれば、焼結処理の実施に伴って、圧粉体中に点在していた潤滑剤粉末が分解・除去されるため、圧粉体中の潤滑剤粉末が点在していた箇所に新たに空孔が形成される。潤滑剤粉末の平均粒径が２０μｍ未満の場合には、圧粉体を加熱・焼結するのに伴って金属粉末が熱膨張等するため、焼結金属の多孔質体からなるすべり軸受１の空孔率向上に有効に寄与し得るような径を有する空孔を確実に形成することができない。これに対し、平均粒径が２０μｍ以上の潤滑剤粉末を選択使用すれば、上記態様で形成される空孔が金属粉末の熱膨張等の影響によって収縮等しても、すべり軸受１の空孔率向上に有効に寄与する。但し、平均粒径が過度に大きい潤滑剤粉末（具体的には、平均粒径が２００μｍ以上の潤滑剤粉末）を使用すると、潤滑剤粉末が本来的に発揮すべき潤滑機能を発揮できないばかりか、新たに形成される空孔も過度に大きい粗大空孔となり易いためすべり軸受１の強度低下を招来する可能性がある。従って、分解温度が高強度化処理の処理温度以下であると共に、平均粒径が２０μｍ以上２００μｍ未満の潤滑剤粉末を選択的に使用すれば、使用する金属粉末の種類や組成に制限を加えずとも、１０ｖｏｌ％を超える高い空孔率と必要強度とを兼ね備えた焼結金属製のすべり軸受１を得ることができる。 In this way, the lubricant powder scattered in the green compact is decomposed and removed with the execution of the sintering treatment, so that the lubricant powder in the green compact is scattered. A new hole is formed at the location. When the average particle size of the lubricant powder is less than 20 μm, the metal powder expands thermally as the green compact is heated and sintered, so that the slide bearing 1 made of a porous body of sintered metal It is not possible to reliably form pores having a diameter that can effectively contribute to the improvement of the pore ratio. On the other hand, if a lubricant powder having an average particle size of 20 μm or more is selectively used, even if the pores formed in the above embodiment shrink due to the influence of thermal expansion of the metal powder or the like, the pores of the slide bearing 1 Effectively contributes to rate improvement. However, if a lubricant powder having an excessively large average particle size (specifically, a lubricant powder having an average particle size of 200 μm or more) is used, not only does the lubricant powder not exhibit the lubricating function that it should originally exhibit. Since the newly formed pores are also likely to be excessively large coarse pores, the strength of the slide bearing 1 may be lowered. Therefore, if the decomposition temperature is equal to or lower than the processing temperature of the high-strength treatment and the lubricant powder having an average particle size of 20 μm or more and less than 200 μm is selectively used, the type and composition of the metal powder to be used are not restricted. In either case, it is possible to obtain a plain bearing 1 made of sintered metal, which has a high porosity of more than 10 vol% and a required strength.
以上、本発明の実施形態に係る多孔質金属部品（焼結金属製のすべり軸受１）の製造方法について説明したが、本発明の実施の形態はこれに限定されるわけではない。すなわち、本発明は、例えば、図２に模式的に示すように、無数の内部空孔１１を有し、内部空孔１１が、主に酸化皮膜１３を介して結合した金属粉末の粒子１２相互間に画成されたすべり軸受１０を得る際にも、好ましく適用することができる。 Although the method for manufacturing the porous metal part (sintered metal slide bearing 1) according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this. That is, for example, as schematically shown in FIG. 2, the present invention has innumerable internal pores 11, and the internal pores 11 are bonded to each other mainly through the oxide film 13. It can also be preferably applied when obtaining a plain bearing 10 defined between them.
図２に示すすべり軸受１０は、図１に示すすべり軸受１と同様に、１０ｖｏｌ％を超える空孔率を有し、内部空孔に潤滑油を含浸させた状態で使用されるものである。このすべり軸受１０は、主に、酸化皮膜を形成可能な金属粉末（例えば、鉄、銅、アルミニウム、マグネシウム、クロム等のイオン化傾向の大きい金属の粉末、あるいは上記金属を含む合金粉末）を主成分とする原料粉末を用いて圧粉体を作製する点、および圧粉体に施すべき加熱を伴う高強度化処理として、酸化皮膜を形成する皮膜形成処理が採用される点を除き、図１に示すすべり軸受１と同様の手順を踏んで作製される。そのため、以下では、皮膜形成処理についてのみ詳細に説明する。 Like the slide bearing 1 shown in FIG. 1, the slide bearing 10 shown in FIG. 2 has a pore ratio of more than 10 vol% and is used in a state where the internal pores are impregnated with lubricating oil. The plain bearing 10 is mainly composed of a metal powder capable of forming an oxide film (for example, a powder of a metal having a high ionization tendency such as iron, copper, aluminum, magnesium, chromium, or an alloy powder containing the above metal). FIG. 1 shows FIG. 1 except that a green compact is produced using the raw material powder and a film forming treatment for forming an oxide film is adopted as a high-strength treatment accompanied by heating to be applied to the green compact. It is manufactured by following the same procedure as the slide bearing 1 shown. Therefore, in the following, only the film forming treatment will be described in detail.
皮膜形成処理は、酸化雰囲気下（例えば、大気、酸素、あるいはこれらに窒素やアルゴンなどの不活性ガスを混合したガス雰囲気下）に置かれた圧粉体を３５０℃以上７００℃以下で所定時間（圧粉体の大きさにもよるが、概ね５分以内）加熱する、というものである。これにより、圧粉体を構成する金属粒子の表面に酸化皮膜１３が徐々に形成され、この酸化皮膜１３が成長するのに伴って、隣接する金属粒子同士が酸化皮膜１３を介して結合したすべり軸受１０が得られる。なお、例えば、金属粉末として鉄粉末を採用した場合、酸化皮膜１３は、主にＦｅ3Ｏ4、Ｆｅ2Ｏ3、ＦｅＯの群から選択される２種類以上の混相となり、金属粉末として銅粉末を採用した場合、酸化皮膜１３は、主にＣｕ０、Ｃｕ2Ｏ、Ｃｕ2+1Ｏの群から選択される２種類以上の混相となるが、どのような相になるかは、皮膜形成処理の処理要件等によって異なる。また、酸化皮膜１３の形成に際しては、圧粉体を構成する金属粉末を水蒸気と反応させるようにしても良い。このような処理は、水蒸気処理とも称される。 In the film forming treatment, a green compact placed in an oxidizing atmosphere (for example, an atmosphere, oxygen, or a gas atmosphere in which an inert gas such as nitrogen or argon is mixed with the atmosphere) is placed at 350 ° C. or higher and 700 ° C. or lower for a predetermined time. It is heated (within about 5 minutes, depending on the size of the green compact). As a result, an oxide film 13 is gradually formed on the surface of the metal particles constituting the green compact, and as the oxide film 13 grows, adjacent metal particles are bonded to each other via the oxide film 13. The bearing 10 is obtained. For example, when iron powder is used as the metal powder, the oxide film 13 is a mixed phase of two or more types mainly selected from the group of Fe 3 O 4 , Fe 2 O 3 , and Fe O, and the copper powder is used as the metal powder. When is adopted, the oxide film 13 is a mixed phase of two or more types mainly selected from the group of Cu 0, Cu 2 O, and Cu 2 + 1 O, but the phase is determined by the film forming process. It depends on the processing requirements of. Further, when forming the oxide film 13 , the metal powder constituting the green compact may be reacted with water vapor. Such treatment is also referred to as steam treatment.
上記のように、酸化皮膜１３を形成する処理は、その処理温度が、圧粉体を焼結する場合の処理温度よりも格段に低いので、処理後における圧粉体の寸法変化量を小さくすることができる。そのため、圧粉体を焼結した場合には、その後の実施が必要不可欠であったサイジング等の整形加工を省略することも可能となる。また、寸法変化量を小さくできれば、圧粉体を成形するための整形金型の設計処理温度が容易となる。さらに、処理温度が低ければ、処理時に必要なエネルギーも削減できるため、処理コストを低減できる。 As described above, in the treatment for forming the oxide film 13 , the treatment temperature thereof is significantly lower than the treatment temperature in the case of sintering the green compact, so that the amount of dimensional change of the green compact after the treatment is reduced. be able to. Therefore, when the green compact is sintered, it is possible to omit the shaping process such as sizing, which is indispensable for the subsequent implementation. Further, if the amount of dimensional change can be reduced, the design processing temperature of the shaping die for molding the green compact becomes easy. Further, if the processing temperature is low, the energy required for processing can be reduced, so that the processing cost can be reduced.
以上で説明した各実施形態において、成形工程と高強度化処理工程との間には、圧粉体を高強度化処理の処理温度（焼結処理温度又は皮膜形成処理温度）よりも低い温度で加熱する脱脂処理工程を設けても良い。この場合、潤滑剤粉末としては、その分解温度が脱脂処理工程における圧粉体の加熱温度よりも低いものを使用するのが好ましい。このようにすれば、圧粉体に含まれる潤滑剤粉末は、実質的に、脱脂処理工程および高強度化処理工程の双方で除去されるため、潤滑剤粉末に由来する残渣物がすべり軸受１の内部に残存するのを効果的に防止することができる。そのため、高品質のすべり軸受１を得る上で有利となる。また、潤滑剤成分をより確実に除去し、残渣物を少なくするために、脱脂工程は不活性雰囲気、還元性雰囲気、真空雰囲気で実施しても良い。 In each of the embodiments described above, between the molding step and the high-strength treatment step, the green compact is at a temperature lower than the high-strength treatment treatment temperature (sintering treatment temperature or film formation treatment temperature). A degreasing treatment step of heating may be provided. In this case, it is preferable to use a lubricant powder whose decomposition temperature is lower than the heating temperature of the green compact in the degreasing treatment step. In this way, the lubricant powder contained in the green compact is substantially removed in both the degreasing treatment step and the high-strength treatment step, so that the residue derived from the lubricant powder is removed from the slide bearing 1. It can be effectively prevented from remaining inside the. Therefore, it is advantageous in obtaining a high-quality slide bearing 1. Further, in order to more reliably remove the lubricant component and reduce the amount of residue, the degreasing step may be carried out in an inert atmosphere, a reducing atmosphere or a vacuum atmosphere.
また、以上で説明した本発明に係る多孔質金属部品の製造方法は、内部空孔に潤滑油を含浸させた状態で使用されるすべり軸受のみならず、例えば、内部空孔が流体の流路として活用されるフィルタを製造する際にも好ましく適用することができる。 Further, the method for manufacturing a porous metal part according to the present invention described above is not limited to a plain bearing used in a state where the internal pores are impregnated with a lubricating oil, for example, the internal pores are a flow path of a fluid. It can also be preferably applied when manufacturing a filter utilized as a bearing.
本発明の有用性を確認するため、（１）潤滑剤粉末の粒径、（２）潤滑剤粉末の添加量、（３）圧粉体の密度、（４）圧粉体を高強度化するための方法、（５）金属粉末の組成、および（６）潤滑剤粉末の種類が、多孔質金属部品の空孔率に与える影響を調査・確認した。何れの確認試験においても、空孔率は、各試験体の内部空孔に含浸させた潤滑油量、すなわち含油率に基づいて評価した。含油率は、ＪＩＳ Ｚ ２５０１に準拠した方法で求めた。各試験体に対する含油処理は、いわゆる真空含浸法により行い、ここでは、各試験体を７０℃の油圧作動油（昭和シェル石油社製のシェルテラスＳ２Ｍ６８、ＩＳＯ粘度ＶＧ６８相当）中に１時間以上浸漬させた。以下、上記（１）−（６）の確認試験について詳細に説明する。 In order to confirm the usefulness of the present invention, (1) the particle size of the lubricant powder, (2) the amount of the lubricant powder added, (3) the density of the green compact, and (4) the strength of the green compact is increased. The effect of the method, (5) composition of metal powder, and (6) type of lubricant powder on the porosity of porous metal parts was investigated and confirmed. In each confirmation test, the pore ratio was evaluated based on the amount of lubricating oil impregnated in the internal pores of each test piece, that is, the oil content. The oil content was determined by a method conforming to JIS Z 2501. The oil impregnation treatment for each test piece is performed by the so-called vacuum impregnation method, and here, each test piece is immersed in hydraulic hydraulic oil at 70 ° C. (Shell Terrace S2M68 manufactured by Showa Shell Sekiyu Co., Ltd., equivalent to ISO viscosity VG68) for 1 hour or more. I let you. Hereinafter, the confirmation tests of (1)-(6) above will be described in detail.
（１）第１の確認試験：潤滑剤粉末の粒径
はじめに、使用する潤滑剤粉末の粒径が、多孔質金属部品の空孔率（含油率）に与える影響を調査・確認した。この確認試験の実施に際して、４種類の試験体（実施例１−３および比較例１）を作製した。４種類の試験体は、原料粉末に含める潤滑剤粉末の平均粒径を相互に異ならせる以外は、同様の条件・手順で作製した。詳細は、以下のとおりである。
［原料粉末］
金属粉末としての還元鉄粉（平均粒径１００μｍ）に対し、潤滑剤粉末としてのアミドワックス（分解温度２００〜４００℃）を０．５質量％添加したもの。
［試験体の作製手順］
ＳＫＤ１１製の成形金型を用いた一軸加圧成形法で上記の原料粉末を圧縮することにより、内径寸法６ｍｍ×外径寸法１２ｍｍ×全長寸法５±０．２ｍｍの円筒状圧粉体（密度：６．５ｇ／ｃｍ３）を得てから、この圧粉体に脱脂処理および焼結処理を施した。脱脂処理の処理条件は、雰囲気：不活性、加熱温度：５００℃、加熱時間：０．５ｈｒとし、焼結処理の処理条件は、雰囲気：不活性、加熱温度：１１００℃、加熱時間：０．５ｈｒとした。
(1) First confirmation test: Particle size of lubricant powder First, the effect of the particle size of the lubricant powder used on the porosity (oil content) of porous metal parts was investigated and confirmed. In carrying out this confirmation test, four types of test bodies (Example 1-3 and Comparative Example 1) were prepared. The four types of test specimens were prepared under the same conditions and procedures except that the average particle sizes of the lubricant powders contained in the raw material powders were different from each other. The details are as follows.
[Ingredient powder]
A product obtained by adding 0.5% by mass of amide wax (decomposition temperature 200 to 400 ° C.) as a lubricant powder to reduced iron powder (average particle size 100 μm) as a metal powder.
[Procedure for preparing test specimens]
By compressing the above raw material powder by a uniaxial pressure molding method using a molding die made of SKD11, a cylindrical green compact having an inner diameter of 6 mm × an outer diameter of 12 mm × a total length of 5 ± 0.2 mm (density: After obtaining 6.5 g / cm 3 ), this green compact was degreased and sintered. The treatment conditions for the degreasing treatment were atmosphere: inert, heating temperature: 500 ° C., heating time: 0.5 hr, and the treatment conditions for sintering treatment were atmosphere: inert, heating temperature: 1100 ° C., heating time: 0. It was set to 5 hr.
この確認試験の試験結果を下記の表１に示す。なお、この試験では、含油率が１０ｖｏｌ％を超えた場合を「○」、含油率が１０ｖｏｌ％以下の場合を「×」で評価した。 The test results of this confirmation test are shown in Table 1 below. In this test, the case where the oil content exceeded 10 vol% was evaluated as "◯", and the case where the oil content was 10 vol% or less was evaluated as "x".
表１からも明らかなように、平均粒径が２０μｍ未満の潤滑剤粉末を用いた比較例１では、含油率が１０ｖｏｌ％を下回った。これは、圧粉体を焼結するのに伴って金属粉末が熱膨張等することにより、潤滑剤粉末が分解・除去されるのに伴って形成された空孔が収縮したこと、また、金属粒子間の空隙が潰れたこと、などに起因すると考えられる。これに対し、平均粒径が２０μｍ以上の潤滑剤粉末を用いた実施例１−３は、何れも、含油率が１０ｖｏｌ％を十分に上回った。これは、潤滑剤粉末が分解・除去されるのに伴って形成される空孔が十分に大きかったため、金属粉末の熱膨張等によって上記の空孔が収縮等しても、上記の空孔が消失するような事態が回避されたためであると推察される。なお、参考までに、図３（ａ）に、実施例３の断面拡大写真を示し、図３（ｂ）に、比較例１の断面拡大写真を示す。 As is clear from Table 1, in Comparative Example 1 using the lubricant powder having an average particle size of less than 20 μm, the oil content was less than 10 vol%. This is because the metal powder thermally expands as the green compact is sintered, and the pores formed as the lubricant powder is decomposed and removed shrinks, and the metal It is considered that this is caused by the collapse of the voids between the particles. On the other hand, in Examples 1-3 using the lubricant powder having an average particle size of 20 μm or more, the oil content was sufficiently higher than 10 vol%. This is because the pores formed as the lubricant powder is decomposed and removed are sufficiently large, so that even if the pores shrink due to thermal expansion of the metal powder or the like, the pores remain. It is presumed that this is because the situation of disappearing was avoided. For reference, FIG. 3 (a) shows an enlarged cross-sectional photograph of Example 3, and FIG. 3 (b) shows an enlarged cross-sectional photograph of Comparative Example 1.
（２）第２の確認試験：潤滑剤粉末の添加量
次に、金属粉末に対する潤滑剤粉末の添加量が、多孔質金属部品の含油率に与える影響を調査・確認するため、比較例２−３および実施例４−６に係る試験体を新たに作製した。すなわち、比較例２−３および実施例４−６に係る試験体は、還元鉄粉に対し、平均粒径が１３０μｍの潤滑剤粉末（アミドワックス）を添加・混合した原料粉末を用いて作製した点で共通するが、還元鉄粉に対する潤滑剤粉末の添加量は相互に異なる。なお、新たに作製した各試験体の作製手順は、第１の確認試験で使用した各試験体の作製手順と同様である。
(2) Second confirmation test: Amount of lubricant powder added Next, in order to investigate and confirm the effect of the amount of lubricant powder added to the metal powder on the oil content of the porous metal parts, Comparative Example 2- A new test body according to 3 and Example 4-6 was prepared. That is, the test specimens according to Comparative Examples 2-3 and 4-6 were prepared by using a raw material powder obtained by adding and mixing a lubricant powder (amide wax) having an average particle size of 130 μm to the reduced iron powder. Although common in that, the amount of the lubricant powder added to the reduced iron powder is different from each other. The preparation procedure of each newly prepared test piece is the same as the preparation procedure of each test piece used in the first confirmation test.
この確認試験の試験結果を下記の表２に示す。なお、この試験では、含油率が１０ｖｏｌ％を超えた場合を「○」、含油率が１０ｖｏｌ％以下の場合を「×」、含油率が１０ｖｏｌ％を超えたものの、試験体を作製する過程（詳細には、圧粉体を焼結炉に搬送する段階）で圧粉体に部分的な欠損等が生じた場合を「△」で評価した。 The test results of this confirmation test are shown in Table 2 below. In this test, the case where the oil content exceeds 10 vol% is "○", the case where the oil content is 10 vol% or less is "x", and the oil content exceeds 10 vol%, but the process of preparing the test piece ( Specifically, the case where the green compact was partially chipped during the stage of transporting the green compact to the sintering furnace was evaluated as “Δ”.
表２からも明らかなように、潤滑剤粉末の添加量が０．３質量％を下回る場合（具体的には０．２質量％の場合：比較例２）、含油率が１０ｖｏｌ％を下回り、潤滑剤粉末の添加量が３質量％の場合（比較例３）、含油率は１０ｖｏｌ％を十分に上回るものの、圧粉体の搬送時に圧粉体に部分的な欠損等が生じたため、実用上好ましくない。従って、潤滑剤粉末の添加量は、０．３質量％以上３質量％未満とするのが好ましいことがわかる。 As is clear from Table 2, when the amount of the lubricant powder added is less than 0.3% by mass (specifically, when 0.2% by mass: Comparative Example 2), the oil content is less than 10 vol%. When the amount of the lubricant powder added is 3% by mass (Comparative Example 3), the oil content is sufficiently higher than 10 vol%, but the green compact is partially chipped during transportation of the green compact, so that it is practically used. Not preferable. Therefore, it can be seen that the amount of the lubricant powder added is preferably 0.3% by mass or more and less than 3% by mass.
（３）第３の確認試験：圧粉体の密度
次に、圧粉体の密度が、多孔質金属部品の含油率に与える影響を調査・確認するため、比較例４−５および実施例７−８に係る試験体を新たに作製した。すなわち、比較例４−５および実施例７−８に係る試験体は、金属粉末としての還元鉄粉に対し、平均粒径が１３０μｍの潤滑剤粉末を０．５質量％添加・混合した原料粉末を用いて成形した圧粉体を基材とする点で共通するが、圧粉体の密度は相互に異なる。なお、新たに作製した各試験体の作製手順は、第１の確認試験で使用した各試験体の作製手順と同様である。
(3) Third confirmation test: Density of green compact Next, in order to investigate and confirm the influence of the density of green compact on the oil content of porous metal parts, Comparative Examples 4-5 and Example 7 A new test piece according to -8 was prepared. That is, in the test specimens according to Comparative Examples 4-5 and 7-8, 0.5% by mass of a lubricant powder having an average particle size of 130 μm was added and mixed with the reduced iron powder as a metal powder. It is common in that the green compact formed using the above is used as the base material, but the density of the green compact is different from each other. The preparation procedure of each newly prepared test body is the same as the preparation procedure of each test body used in the first confirmation test.
この確認試験の試験結果を下記の表３に示す。なお、この試験で採用した各試験体の評価基準は、第２の確認試験と同様である。 The test results of this confirmation test are shown in Table 3 below. The evaluation criteria of each test piece adopted in this test are the same as those in the second confirmation test.
表３からも明らかなように、圧粉体の密度が５．５ｇ／ｃｍ３の場合（比較例４）、含油率は１０ｖｏｌ％を十分に上回るものの、圧粉体の搬送時に圧粉体に部分的な欠損等が生じたため、実用上好ましくない。また、圧粉体の密度が７．２ｇ／ｃｍ３の場合（比較例５）、含油率が１０ｖｏｌ％を大幅に下回る。従って、特に純鉄系の多孔質金属部品を得る場合、圧粉体は、その密度が５．５ｇ／ｃｍ３を超え、かつ７．２ｇ／ｃｍ３未満となるように成形するのが好ましい。 As is clear from Table 3, when the density of the green compact is 5.5 g / cm 3 (Comparative Example 4), the oil content is sufficiently higher than 10 vol%, but it becomes a green compact when the green compact is conveyed. It is not practically preferable because a partial defect or the like has occurred. Further, when the density of the green compact is 7.2 g / cm 3 (Comparative Example 5), the oil content is significantly lower than 10 vol%. Therefore, particularly when obtaining a porous metal parts pure iron, powder compact, the density exceeds 5.5 g / cm 3, and preferably molded to be less than 7.2 g / cm 3.
（４）第４の確認試験：圧粉体を高強度化するための方法
次に、圧粉体を高強度化するための方法が、多孔質金属部品の含油率に与える影響を調査・確認するため、実施例９−１０に係る試験体を新たに作製・準備した。すなわち、実施例９−１０に係る試験体は、金属粉末（還元鉄粉）に対し、平均粒径が１３０μｍの潤滑剤粉末を０．５質量％添加・混合した原料粉末を用いて成形した密度６．５ｇ／ｃｍ３の圧粉体を基材とする点で共通するが、圧粉体に施した高強度化処理の手法が相互に異なる。具体的に説明すると、実施例９に係る試験体は、高強度化処理として、圧粉体を大気中で５００℃に加熱することにより、圧粉体を構成する鉄粒子の表面に鉄粒子同士を結合する酸化皮膜を形成する、という処理を採用して作製し、実施例１０に係る試験体は、高強度化処理として、５００℃に加熱された圧粉体を水蒸気と反応させることにより、圧粉体を構成する鉄粒子の表面に鉄粒子同士を結合する酸化皮膜を形成する、という処理（水蒸気処理）を採用して作製した。
(4) Fourth confirmation test: Method for increasing the strength of the green compact Next, the effect of the method for increasing the strength of the green compact on the oil content of porous metal parts is investigated and confirmed. Therefore, a new test body according to Example 9-10 was prepared and prepared. That is, the test piece according to Example 9-10 has a density formed by using a raw material powder obtained by adding and mixing 0.5% by mass of a lubricant powder having an average particle size of 130 μm with respect to a metal powder (reduced iron powder). It is common in that it uses a green compact of 6.5 g / cm 3 as a base material, but the methods of high-strength treatment applied to the green compact are different from each other. Specifically, in the test piece according to Example 9, as a high-strength treatment, the green compact is heated to 500 ° C. in the air, so that the iron particles are placed on the surface of the iron particles constituting the green compact. The test piece according to Example 10 was prepared by adopting a process of forming an oxide film for binding the above, and the test piece according to Example 10 was prepared by reacting a green compact heated to 500 ° C. with steam as a high-strength treatment. It was produced by adopting a treatment (steam treatment) of forming an oxide film that binds iron particles to each other on the surface of iron particles constituting the green compact.
この確認試験の試験結果を下記の表４に示す。なお、この試験で採用した各試験体の評価基準は、第１の確認試験と同様である。 The test results of this confirmation test are shown in Table 4 below. The evaluation criteria of each test piece adopted in this test are the same as those in the first confirmation test.
表４からも明らかなように、実施例９−１０（および実施例３）に係る試験体は、何れも含油率が１０ｖｏｌ％を十分に超えた。従って、本発明は、圧粉体に施すべき加熱を伴う高強度化処理として、焼結処理のみならず、酸化皮膜の形成処理を採用する場合でも、好ましく適用し得ることがわかる。 As is clear from Table 4, the test specimens according to Examples 9-10 (and Example 3) all had an oil content sufficiently exceeding 10 vol%. Therefore, it can be seen that the present invention can be preferably applied not only to the sintering treatment but also to the oxide film forming treatment as the strength increasing treatment accompanied by heating to be applied to the green compact.
（５）第５の確認試験：金属粉末の組成
次に、金属粉末の組成が、多孔質金属部品の含油率に与える影響を調査・確認するため、実施例１１−１２に係る試験体を新たに作製した。実施例１１は、金属粉末を、鉄−銅系粉末（Ｆｅ−４０％Ｃｕの粉末であって、Ｆｅは還元鉄粉、Ｃｕは還元銅粉）に置換した以外は、実施例３と同様の手順を踏んで作製し、実施例１２は、金属粉末を、銅−錫系粉末（Ｃｕ−１０％Ｓｎの粉末であって、Ｃｕは還元銅粉、Ｓｎはアトマイズ錫粉）に置換した以外は、実施例３と同様の手順を踏んで作製した。
(5) Fifth Confirmation Test: Composition of Metal Powder Next, in order to investigate and confirm the influence of the composition of the metal powder on the oil content of the porous metal parts, a new test piece according to Example 11-12 was prepared. Made in. Example 11 is the same as in Example 3 except that the metal powder is replaced with an iron-copper powder (a powder of Fe-40% Cu, Fe is reduced iron powder and Cu is reduced copper powder). In Example 12, the metal powder was replaced with a copper-tin powder (Cu-10% Sn powder, Cu was reduced copper powder, Sn was atomized tin powder). , The same procedure as in Example 3 was followed.
この確認試験の試験結果を下記の表５に示す。なお、この試験で採用した各試験体の評価基準は、第１の確認試験と同様である。 The test results of this confirmation test are shown in Table 5 below. The evaluation criteria of each test piece adopted in this test are the same as those in the first confirmation test.
表５からも明らかなように、実施例１１−１２（および実施例３）に係る試験体は、何れも含油率が１０ｖｏｌ％を十分に超えた。従って、本発明は、使用する金属粉末の材質や組成によらず、含油率（空孔率）が高められた多孔質金属部品を得る上で有用であることがわかる。 As is clear from Table 5, the oil content of each of the test specimens according to Examples 11-12 (and Example 3) sufficiently exceeded 10 vol%. Therefore, it can be seen that the present invention is useful for obtaining a porous metal part having an increased oil content (vacancy ratio) regardless of the material and composition of the metal powder used.
（６）第６の確認試験：潤滑剤粉末の種類
最後に、金属粉末に添加する潤滑剤粉末の種類が、多孔質金属部品の含油率に与える影響を調査・確認するため、実施例１３−１４に係る試験体を新たに作製した。すなわち、実施例１３−１４に係る試験体は、金属粉末としての還元鉄粉に対し、平均粒径が１３０μｍの潤滑剤粉末を０．５質量％添加・混合した原料粉末を用いて成形した密度６．５ｇ／ｃｍ３の圧粉体を基材とする点で共通しているが、実施例１３では、潤滑剤粉末として、金属石けん系のステアリン酸亜鉛（分解温度：２００〜５００℃）を採用し、実施例１４では、潤滑剤粉末として、アミドワックスと上記のステアリン酸亜鉛とを１：１の重量比率で混合したものを採用した。
(6) Sixth Confirmation Test: Type of Lubricant Powder Finally, in order to investigate and confirm the influence of the type of lubricant powder added to the metal powder on the oil content of the porous metal part, Example 13- A test body according to 14 was newly prepared. That is, the test piece according to Examples 13-14 has a density formed by using a raw material powder obtained by adding and mixing 0.5% by mass of a lubricant powder having an average particle size of 130 μm with respect to the reduced iron powder as a metal powder. It is common in that a green compact of 6.5 g / cm 3 is used as a base material, but in Example 13, a metallic soap-based zinc stearate (decomposition temperature: 200 to 500 ° C.) is used as the lubricant powder. In Example 14, a mixture of amide wax and the above zinc stearate in a weight ratio of 1: 1 was adopted as the lubricant powder.
この確認試験の試験結果を下記の表６に示す。なお、この試験で採用した各試験体の評価基準は、第１の確認試験と同様である。 The test results of this confirmation test are shown in Table 6 below. The evaluation criteria of each test piece adopted in this test are the same as those in the first confirmation test.
表６からも明らかなように、実施例１３−１４に係る試験体は、何れも、実施例３に係る試験体と同様に、含油率が１０ｖｏｌ％を十分に超えた。従って、本発明は、分解温度が、加熱を伴う高強度化処理の処理温度（より好ましくは脱脂処理の処理温度）よりも低い潤滑剤粉末を使用すれば、その添加量が適切な範囲内である限りにおいて、使用する潤滑剤粉末の種類に関わらず含油率（空孔率）が十分に高められた多孔質金属部品を得る上で有用であることがわかる。 As is clear from Table 6, all of the test bodies according to Examples 13-14 had an oil content well exceeding 10 vol%, similarly to the test bodies according to Example 3. Therefore, in the present invention, if a lubricant powder whose decomposition temperature is lower than the treatment temperature of the high-strength treatment accompanied by heating (more preferably the treatment temperature of the degreasing treatment) is used, the addition amount thereof is within an appropriate range. As far as it is concerned, it can be seen that it is useful for obtaining a porous metal part having a sufficiently increased oil content (vacancy ratio) regardless of the type of lubricant powder used.
以上の確認試験結果から、本発明は、使用する金属粉末の種類や組成等に制限を加えずとも、高い空孔率と必要強度を兼ね備えた多孔質金属部品を作製することができる極めて有用なものであることがわかる。 From the above confirmation test results, the present invention is extremely useful because it can produce a porous metal part having a high porosity and a required strength without limiting the type and composition of the metal powder to be used. It turns out that it is a thing.
１ すべり軸受（多孔質金属部品）
２ 内部空孔
３ 金属粉末の粒子
１０ すべり軸受（多孔質金属部品）
１１ 内部空孔
１２ 金属粉末の粒子
１３ 酸化皮膜
1 Plain bearing (porous metal parts)
2 Internal pores 3 Metal powder particles 10 Plain bearings (porous metal parts)
11 Internal pores 12 Metal powder particles 13 Oxide film
Claims (4)
金属粉末に潤滑剤粉末を添加してなる原料粉末の圧粉体を成形する成形工程と、加熱を伴う高強度化処理を前記圧粉体に施す高強度化処理工程とを有し、
前記潤滑剤粉末として、分解温度が前記高強度化処理の処理温度以下であると共に、平均粒径が１３０μｍ以上２００μｍ未満のものを使用し、
前記金属粉末に対する前記潤滑剤粉末の添加量を、０．３質量％以上３質量％未満としたことを特徴とする多孔質金属部品の製造方法。 A method for producing a porous metal part having a porosity of more than 10 vol% and 20 vol% or less.
It has a molding step of molding a green compact of a raw material powder formed by adding a lubricant powder to a metal powder, and a high strength treatment step of applying a high strength treatment accompanied by heating to the green compact.
As the lubricant powder, one having a decomposition temperature equal to or lower than the treatment temperature of the high-strength treatment and an average particle size of 130 μm or more and less than 200 μm is used.
A method for producing a porous metal part, wherein the amount of the lubricant powder added to the metal powder is 0.3% by mass or more and less than 3% by mass.
前記潤滑剤粉末として、分解温度が前記脱脂処理工程における前記圧粉体の加熱温度よりも低いものを使用する請求項１に記載の多孔質金属部品の製造方法。 Between the molding step and the high-strength treatment step, there is a degreasing treatment step of heating the green compact at a temperature lower than the treatment temperature of the high-strength treatment.
The method for producing a porous metal part according to claim 1 , wherein the lubricant powder having a decomposition temperature lower than the heating temperature of the green compact in the degreasing treatment step is used.
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