JP4556755B2 - Powder mixture for powder metallurgy - Google Patents
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- JP4556755B2 JP4556755B2 JP2005124373A JP2005124373A JP4556755B2 JP 4556755 B2 JP4556755 B2 JP 4556755B2 JP 2005124373 A JP2005124373 A JP 2005124373A JP 2005124373 A JP2005124373 A JP 2005124373A JP 4556755 B2 JP4556755 B2 JP 4556755B2
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- 239000000843 powder Substances 0.000 title claims description 186
- 238000004663 powder metallurgy Methods 0.000 title claims description 24
- 239000000203 mixture Substances 0.000 title description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 82
- 229910052742 iron Inorganic materials 0.000 claims description 35
- 239000011812 mixed powder Substances 0.000 claims description 17
- 239000002994 raw material Substances 0.000 claims description 9
- 229910000831 Steel Inorganic materials 0.000 claims description 8
- 239000010959 steel Substances 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 2
- 229910001182 Mo alloy Inorganic materials 0.000 claims 1
- 229910000851 Alloy steel Inorganic materials 0.000 description 60
- 239000010949 copper Substances 0.000 description 28
- 229910045601 alloy Inorganic materials 0.000 description 27
- 239000000956 alloy Substances 0.000 description 27
- 238000005245 sintering Methods 0.000 description 22
- 238000009792 diffusion process Methods 0.000 description 18
- 239000002245 particle Substances 0.000 description 14
- 238000005452 bending Methods 0.000 description 12
- 229910052750 molybdenum Inorganic materials 0.000 description 11
- 238000010438 heat treatment Methods 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 10
- 238000000034 method Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 239000000314 lubricant Substances 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 7
- 229910052799 carbon Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000000465 moulding Methods 0.000 description 7
- 238000010791 quenching Methods 0.000 description 7
- 230000000171 quenching effect Effects 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 229910052748 manganese Inorganic materials 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 238000009725 powder blending Methods 0.000 description 5
- 238000005255 carburizing Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 230000001737 promoting effect Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- HGPXWXLYXNVULB-UHFFFAOYSA-M lithium stearate Chemical compound [Li+].CCCCCCCCCCCCCCCCCC([O-])=O HGPXWXLYXNVULB-UHFFFAOYSA-M 0.000 description 3
- RKISUIUJZGSLEV-UHFFFAOYSA-N n-[2-(octadecanoylamino)ethyl]octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(=O)NCCNC(=O)CCCCCCCCCCCCCCCCC RKISUIUJZGSLEV-UHFFFAOYSA-N 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 229910017116 Fe—Mo Inorganic materials 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000004453 electron probe microanalysis Methods 0.000 description 2
- 238000010191 image analysis Methods 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 229910000967 As alloy Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- UAUDZVJPLUQNMU-UHFFFAOYSA-N Erucasaeureamid Natural products CCCCCCCCC=CCCCCCCCCCCCC(N)=O UAUDZVJPLUQNMU-UHFFFAOYSA-N 0.000 description 1
- 229910001309 Ferromolybdenum Inorganic materials 0.000 description 1
- 229910000846 In alloy Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000000889 atomisation Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- CJZGTCYPCWQAJB-UHFFFAOYSA-L calcium stearate Chemical compound [Ca+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O CJZGTCYPCWQAJB-UHFFFAOYSA-L 0.000 description 1
- 239000008116 calcium stearate Substances 0.000 description 1
- 235000013539 calcium stearate Nutrition 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000005256 carbonitriding Methods 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
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- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- UAUDZVJPLUQNMU-KTKRTIGZSA-N erucamide Chemical compound CCCCCCCC\C=C/CCCCCCCCCCCC(N)=O UAUDZVJPLUQNMU-KTKRTIGZSA-N 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- LYRFLYHAGKPMFH-UHFFFAOYSA-N octadecanamide Chemical compound CCCCCCCCCCCCCCCCCC(N)=O LYRFLYHAGKPMFH-UHFFFAOYSA-N 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000000344 soap Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000008117 stearic acid Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000009692 water atomization Methods 0.000 description 1
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 1
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Description
本発明は、合金鋼粉を主体とする粉末冶金用混合粉体に関し、 特に密度が高く、かつ優れた強度を有する各種焼結金属部品を製造するために好適な粉末冶金用混合粉体に関するものである。 The present invention relates to a mixed powder for powder metallurgy mainly composed of alloy steel powder, and particularly to a mixed powder for powder metallurgy suitable for manufacturing various sintered metal parts having high density and excellent strength. It is.
粉末冶金技術は、高寸法精度の複雑な形状の部品をニアネット形状に生産することが可能であり、大幅に切削コストを低減できることから、粉末冶金製品が多方面に利用されている。最近では、部品の小型・軽量化のため、鉄系の粉末冶金製品の高強度化が強く要求されている。
粉末冶金用鉄基粉末成形体は、鉄基粉末に、銅粉，黒鉛粉などの合金用粉末と、さらにステアリン酸，ステアリン酸リチウム等の潤滑剤を混合した鉄基粉末混合粉を金型に充填した後、加圧成形し製造されるのが一般的である。鉄基粉末成形体の密度としては、 6.6〜7.1 Ｍｇ／ｍ3 が一般的である。これら鉄基粉末成形体は、さらに焼結処理を施され焼結体とされ、さらに必要に応じてサイジングや切削加工が施され、粉末冶金製品とされる。また、引張強度や疲労強度を高める必要がある場合は焼結後に浸炭熱処理や光輝熱処理を施されることもある。
Powder metallurgy technology is capable of producing a complex shape part with high dimensional accuracy in a near-net shape, and can greatly reduce cutting costs. Therefore, powder metallurgy products are widely used. Recently, in order to reduce the size and weight of parts, there is a strong demand for higher strength of iron-based powder metallurgy products.
The iron-based powder compact for powder metallurgy is made of iron-based powder mixed with iron-based powder, alloy powder such as copper powder and graphite powder, and lubricant such as stearic acid and lithium stearate. After filling, it is generally produced by pressure molding. The density of the iron-based powder molded body is generally 6.6 to 7.1 Mg / m 3 . These iron-based powder compacts are further subjected to a sintering treatment to obtain sintered bodies, and further subjected to sizing and cutting as necessary to obtain powder metallurgy products. In addition, when it is necessary to increase the tensile strength or fatigue strength, carburizing heat treatment or bright heat treatment may be performed after sintering.
粉末冶金製品の強度を向上させるために、焼入性を改善する合金元素を鉄基粉末に添加することが一般的に行われている。たとえば特公平6-89365 号公報では、フェライト安定化元素であるMoを添加して、Feの自己拡散速度の速いα単一相を形成して焼結を促進させる目的で、Moを 1.5〜20質量％の範囲で予合金として含む合金鋼粉が提案されている。しかしながら、Mo添加量が比較的高いため、合金鋼粉の圧縮性が低く、高い成形密度が得られないという欠点があった。 In order to improve the strength of powder metallurgy products, it is common practice to add alloy elements that improve hardenability to iron-based powders. For example, in Japanese Examined Patent Publication No. 6-89365, Mo is added for the purpose of promoting the sintering by adding Mo, which is a ferrite stabilizing element, to form an α single phase with a high self-diffusion rate of Fe and to promote sintering. Alloy steel powders included as prealloys in the mass% range have been proposed. However, since the amount of added Mo is relatively high, the compressibility of the alloy steel powder is low, and a high molding density cannot be obtained.
一方、 特公平7-51721 号公報には、 鉄粉にMoを0.2〜1.5 質量％，Mnを0.05〜0.25質量％の範囲で予合金化させた、圧粉成形時の圧縮性が比較的高い鋼粉が開示されている。しかしながら、この鋼粉ではMo量が 1.5質量％以下であるためα相単相とならない。したがって、粉末冶金用に一般的に用いられているメッシュベルト炉の焼結温度（1120〜1140℃）では、粒子間の焼結の進行が促進されないので、焼結ネック部の強度が低いという問題点があった。 On the other hand, in Japanese Patent Publication No. 7-51721, iron powder is pre-alloyed with Mo in the range of 0.2 to 1.5% by mass and Mn in the range of 0.05 to 0.25% by mass. Steel powder is disclosed. However, this steel powder does not become α-phase single phase because the Mo content is 1.5 mass% or less. Therefore, the sintering temperature of the mesh belt furnace (1120-1140 ° C) generally used for powder metallurgy does not promote the progress of sintering between particles, so the problem is that the strength of the sintering neck is low. There was a point.
また特公昭63-66362号公報では、Moを圧縮成形性を損なわない範囲（Mo： 0.1〜1.0 質量％）で鉄粉に予合金化し、この鉄粉の粒子表面にCuとNiを粉末の形で拡散付着させることによって、圧粉成形時の圧縮性と焼結後の部材の強度を両立させている。しかしながらこの技術は、特公平7-51721 号公報に開示された技術と同様に、Moを予合金化した鉄粉の焼結性があまり良くないので、CuとNiの添加による引張強度と疲労強度の向上には限界があった。 In Japanese Patent Publication No. 63-66362, Mo is pre-alloyed into iron powder within a range that does not impair compression moldability (Mo: 0.1 to 1.0 mass%), and Cu and Ni are formed into powder form on the surface of the iron powder particles. By diffusing and adhering, the compressibility at the time of compacting and the strength of the sintered member are made compatible. However, this technique, like the technique disclosed in Japanese Patent Publication No. 7-51721, is not so good in the sinterability of iron powder prealloyed with Mo, so the tensile strength and fatigue strength due to the addition of Cu and Ni are not good. There was a limit to improvement.
このように、従来の合金鋼粉では、圧縮性の向上と焼結性の改善を達成するのは困難であった。
本発明は、上記した従来技術の問題点を克服し、合金鋼粉を主体とする粉末冶金用混合粉体であって、焼結体の密度を高く維持しながら、引張強度のみならず疲労強度も高めることができる粉末冶金用混合粉体を提供することを目的とする。 The present invention overcomes the above-mentioned problems of the prior art, and is a mixed powder for powder metallurgy mainly composed of alloy steel powder, which maintains not only the tensile strength but also fatigue strength while maintaining a high density of the sintered body. It is an object to provide a mixed powder for powder metallurgy that can be improved.
本発明は、Mn：0.04〜0.5質量％およびMo： 0.2〜1.5 質量％を予合金化して含有し、残部がFeおよび不可避的不純物からなる鉄基粉末の表面にMo原料粉末が拡散付着された状態でMoを0.05〜1.0 質量％含有する合金鋼粉に、Ni粉： 0.2〜５質量％および／またはCu粉： 0.2〜３質量％を配合する粉末冶金用混合粉体である。 The present invention, Mn: 0.04 to 0.5 wt% Contact and Mo: the 0.2 to 1.5 wt% and contained in pre-alloyed, balance Mo raw material powder diffusion deposited on the surface of the iron-based powder ing of Fe and unavoidable impurities It is a mixed powder for powder metallurgy in which Ni powder: 0.2-5 mass% and / or Cu powder: 0.2-3 mass% are blended in an alloy steel powder containing 0.05-1.0 mass% of Mo in a finished state .
本発明の粉末冶金用混合粉体を使用することによって、優れた引張強度と疲労強度を有しかつ緻密な焼結体を製造することができる。 By using the mixed powder for powder metallurgy according to the present invention, a dense sintered body having excellent tensile strength and fatigue strength can be produced.
以下に本発明の粉末冶金用混合粉体（すなわち合金鋼粉とNi粉，Cu粉を混合した粉体）について、図面にしたがって、さらに詳細に説明する。
まず、合金鋼粉について説明する。
合金鋼粉の製造にあたっては、図２に示すように、まず所定量のMoとMnを予め合金成分として（すなわち予合金として）含有する鉄基粉末(a) とMo含有合金粉末となるMo原料粉末(b) を準備する。
Hereinafter, the mixed powder for powder metallurgy of the present invention (that is, a powder obtained by mixing alloy steel powder, Ni powder, and Cu powder) will be described in more detail with reference to the drawings.
First, the alloy steel powder will be described.
In the production of alloy steel powder, as shown in FIG. 2, first, an iron-based powder (a) containing a predetermined amount of Mo and Mn as alloy components in advance (ie, as a pre-alloy) and Mo raw material to be a Mo-containing alloy powder. Prepare powder (b).
鉄基粉末(a) としては、予合金として含有すべき合金成分を所定量に調整した溶鋼を水ないしガスで噴霧したアトマイズ鉄粉が好ましい。 アトマイズ鉄粉は、通常、アトマイズ後に還元性雰囲気（例えば水素雰囲気）中で加熱してＣとＯを低減させる処理を施すが、本発明の鉄基粉末(a) にはこのような熱処理を施さないアトマイズままの鉄粉を用いることも可能である。 The iron-based powder (a) is preferably atomized iron powder obtained by spraying molten steel adjusted with a predetermined amount of alloy components to be contained as a prealloy with water or gas. Atomized iron powder is usually heated in a reducing atmosphere (for example, hydrogen atmosphere) after atomization to reduce C and O, and the iron-based powder (a) of the present invention is subjected to such heat treatment. It is also possible to use non-atomized iron powder.
Mo原料粉末(b) としては、金属Mo粉末またはMo含有合金粉末を用いても良いし、あるいはMo含有化合物を用いても良い。Mo含有合金粉末は、市販のフェロモリブデンを粉末としたもの、およびMoを５質量％以上含有するFe−Moの水アトマイズ粉末あるいはガスアトマイズ粉末が使用できる。また、Mo含有化合物としては、入手の容易さおよび還元反応の容易さから、Mo酸化物が好ましい。 As the Mo raw material powder (b), metal Mo powder or Mo-containing alloy powder may be used, or Mo-containing compound may be used. As the Mo-containing alloy powder, commercially available ferromolybdenum powder and Fe-Mo water atomized powder or gas atomized powder containing 5% by mass or more of Mo can be used. Further, as the Mo-containing compound, Mo oxide is preferable because it is easily available and the reduction reaction is easy.
次いで、前記した鉄基粉末(a) とMo原料粉末(b) を、所定の比率で混合(c) する。混合(c) には適用可能な任意の方法（例えばヘンシェルミキサーやコーン型ミキサーなど）を用いることができる。鉄基粉末(a) とMo原料粉末(b) との付着性を改善するために、スピンドル油等を 0.1質量％以下の範囲で添加することも可能である。
この混合物を、水素雰囲気等の還元性雰囲気にて、 800〜1000℃の範囲で熱処理(d) することにより、Moが金属MoまたはMo含有合金として拡散付着した合金鋼粉(e) が得られる。なお、アトマイズままの高Ｃ，Ｏ量の鉄粉を使用した場合には、熱処理(d) でＣとＯを低減する。鉄基粉末にアトマイズままの鉄粉を用いた方が、拡散付着処理中にＣとＯが低減されて、鉄基粉末表面が活性になるため、金属MoまたはMo含有合金の拡散による付着が低温でも確実に起こるので好ましい。Fe−Mo合金の水アトマイズ粉末を拡散付着させる場合は、仕上げ還元処理を施していない、アトマイズままの状態で使用しても良い。
Next, the iron-based powder (a) and the Mo raw material powder (b) are mixed (c) at a predetermined ratio. For the mixing (c), any applicable method (for example, a Henschel mixer or a corn mixer) can be used. In order to improve the adhesion between the iron-based powder (a) and the Mo raw material powder (b), it is possible to add spindle oil or the like in the range of 0.1% by mass or less.
By heat-treating (d) this mixture in a reducing atmosphere such as a hydrogen atmosphere in the range of 800 to 1000 ° C., alloy steel powder (e) in which Mo diffuses and adheres as metal Mo or a Mo-containing alloy is obtained. . In addition, when iron powder with a high C and O amount as atomized is used, C and O are reduced by heat treatment (d). When atomized iron powder is used as the iron-based powder, the surface of the iron-based powder becomes active because C and O are reduced during the diffusion-adhesion treatment. However, it is preferable because it occurs surely. When the water atomized powder of Fe-Mo alloy is diffused and adhered, it may be used in an atomized state without finishing reduction treatment.
製造された合金鋼粉は、図１に模式的に示すように、金属MoまたはMo含有合金２と鉄基粉末１とが接触する部位３において、金属MoまたはMo含有合金２中のMoの一部が鉄基粉末１粒子中に拡散して、鉄基粉末１表面に付着（以下、拡散付着という）している。
なおMo原料粉末としてMo酸化物粉を用いた場合には、 前記の熱処理(d) においてMo酸化物が金属Moの形態に還元される。その結果、金属Mo粉末またはMo含有合金粉末をMo原料粉末として用いた場合と同様に、拡散付着によって部分的にMo含有量が増加した状態が得られる。
As shown schematically in FIG. 1, the produced alloy steel powder is a part of Mo in the metal Mo or the Mo-containing
When Mo oxide powder is used as the Mo raw material powder, the Mo oxide is reduced to the form of metallic Mo in the heat treatment (d). As a result, as in the case where the metal Mo powder or the Mo-containing alloy powder is used as the Mo raw material powder, a state in which the Mo content is partially increased by diffusion adhesion is obtained.
このようにして熱処理(d) （拡散付着処理を含む）を行なうと、通常は鉄基粉末１と金属MoまたはMo含有合金２が焼結して固まった状態となるので、所望の粒径に粉砕・分級し、必要に応じさらに焼鈍を施して、合金鋼粉４とする。
次に、合金鋼粉４における合金元素量の限定理由について説明する。
予合金としてのMo： 0.2〜1.5 質量％
本発明の合金鋼粉４で、予合金として（すなわち予め合金成分として）鉄基粉末１に含まれるMo含有量は、合金鋼粉４の質量に対して 0.2〜1.5 質量％である。予合金としてのMo含有量が 1.5質量％を超えても、焼入性向上の効果はさほど変わらず、かえって合金鋼粉４粒子の硬化により圧縮性が低下して好ましくない。経済的な観点からも不利となる。また、予合金としてのMo含有量が 0.2質量％未満の合金鋼粉４を成形・焼結後、浸炭処理および焼入れを行なった場合、 焼結体中にフェライト相が析出しやすくなり、その結果、焼結体が軟らかく強度的にも低いものとなる。
When the heat treatment (d) (including diffusion adhesion treatment) is performed in this manner, the iron-based powder 1 and the metal Mo or Mo-containing
Next, the reason for limiting the amount of alloy elements in the alloy steel powder 4 will be described.
Mo as a pre-alloy: 0.2 to 1.5 mass%
In the alloy steel powder 4 of the present invention, the Mo content contained in the iron-based powder 1 as a pre-alloy (that is, as an alloy component in advance) is 0.2 to 1.5 mass% with respect to the mass of the alloy steel powder 4. Even if the Mo content as a pre-alloy exceeds 1.5% by mass, the effect of improving the hardenability does not change so much. On the contrary, the compressibility is lowered by the hardening of 4 alloy steel powder particles, which is not preferable. It is also disadvantageous from an economic point of view. In addition, when alloy steel powder 4 with a Mo content of less than 0.2 mass% as a pre-alloy is molded and sintered, then carburizing and quenching are performed, the ferrite phase is likely to precipitate in the sintered body. The sintered body is soft and low in strength.
予合金としてのMn：0.04〜0.5質量％
予合金として鉄基粉末１に含まれるMnは、合金鋼粉４の質量に対して 0.5質量％以下である。予合金としてのMn含有量が 0.5質量％を超えると、Mn含有量に見合う焼入性向上の効果が得られなくなり、かえって合金鋼粉４が硬化して圧縮性が低下する。しかもMnを過剰に消費することになり、製造コストの上昇を招く。一方、Mnは鉄基粉末１中に不可避的不純物として0.04質量％は必ず含まれる。Mnを0.04質量％未満に低減させるためには、Mnを除去する処理に長時間を要するので、製造コストの上昇を招く。したがってMnは、0.04〜0.5 質量％とする。
Mn as a prealloy : 0.04 to 0.5 mass %
Mn contained in the iron-based powder 1 as a prealloy is 0.5 mass% or less with respect to the mass of the alloy steel powder 4. If the Mn content as the prealloy exceeds 0.5 mass%, the effect of improving the hardenability commensurate with the Mn content cannot be obtained, and the alloy steel powder 4 is hardened and the compressibility is lowered. In addition, excessive consumption of Mn leads to an increase in manufacturing cost. On the other hand, Mn is necessarily contained in the iron-based powder 1 by 0.04% by mass as an inevitable impurity. In order to reduce Mn to less than 0.04% by mass, it takes a long time to remove Mn, resulting in an increase in manufacturing cost. Thus Mn is a 0.04 to 0.5 wt%.
Moの拡散付着量：0.05〜1.0 質量％
鉄基粉末１はMoとMnとを予合金化して含有するものであり、その鉄基粉末１の表面に金属MoまたはMo含有合金粉末を拡散付着させたものが合金鋼粉４である。合金鋼粉４は、さらに予合金としてのMo含有量〔Mo〕P （質量％）とMoの平均含有量〔Mo〕Ｔ （質量％）とが、下記の (1)式を満足する必要がある。拡散付着Mo量は、 0.1〜0.5 質量％が好ましい。
Mo diffusion adhesion amount: 0.05-1.0 mass%
The iron-based powder 1 contains Mo and Mn pre-alloyed, and the alloy steel powder 4 is obtained by diffusing and adhering metal Mo or Mo-containing alloy powder to the surface of the iron-based powder 1. In alloy steel powder 4, the Mo content [Mo] P (mass%) and the average Mo content [Mo] T (mass%) as pre-alloys must satisfy the following formula (1). is there. The amount of diffusion deposited Mo is preferably 0.1 to 0.5% by mass.
0.05≦〔Mo〕T −〔Mo〕P≦ 1.0 ・・・ (1)
式中の〔Mo〕T −〔Mo〕P の意味は、鉄基粉末１表面に拡散付着されたMo量のことであり、以下では〔Mo〕T −〔Mo〕P を拡散付着量と記載する。
Moの拡散付着量が0.05質量％未満では、焼入性向上の効果が少なく、また合金鋼粉４同士の接触面における焼結促進の効果も小さくなる。一方、Moの拡散付着量が 1.0質量％を超えても焼入性向上や焼結促進の効果はほとんど改善されず、Moの過剰消費に起因する製造コストの上昇を招く。
0.05 ≦ [Mo] T − [Mo] P ≦ 1.0 (1)
The meaning of [Mo] T- [Mo] P in the formula is the amount of Mo diffused and deposited on the surface of the iron-based powder 1, and hereinafter, [Mo] T- [Mo] P will be described as the amount of diffuse deposited. To do.
When the amount of diffusion of Mo is less than 0.05% by mass, the effect of improving the hardenability is small, and the effect of promoting the sintering at the contact surface between the alloy steel powders 4 is also small. On the other hand, even if the amount of diffusion of Mo exceeds 1.0% by mass, the effects of improving hardenability and promoting sintering are hardly improved, resulting in an increase in manufacturing cost due to excessive consumption of Mo.
合金鋼粉４の表面にMoが拡散付着して形成されるMo高濃度部は、Mo含有量が２質量％以下で、面積率が合金鋼粉４の断面積の１〜30％であることが好ましい。Mo高濃度部のMo含有量が２質量％未満では、900 ℃以上でα相が生成せず、焼結が促進されない。また、Mo高濃度部の面積率が合金鋼粉４の断面積の１％未満では、焼結時に接触点の数が減少し、焼結が促進されない。一方、面積率が30％を超えると、焼結促進の効果はほとんど改善されず、Moの過剰消費に起因する製造コストの上昇を招く。しかも固溶硬化によって合金鋼粉４が硬化する割合が大きくなり、圧縮性が低下する。なお、Mo高濃度部の面積率は１〜20％が一層好ましい。 The Mo high-concentration part formed by diffusion adhesion of Mo on the surface of the alloy steel powder 4 has a Mo content of 2% by mass or less and an area ratio of 1-30% of the cross-sectional area of the alloy steel powder 4. Is preferred. If the Mo content in the Mo high concentration part is less than 2% by mass, an α phase is not generated at 900 ° C. or higher, and sintering is not promoted. Moreover, if the area ratio of Mo high concentration part is less than 1% of the cross-sectional area of the alloy steel powder 4, the number of contact points will reduce at the time of sintering, and sintering will not be accelerated | stimulated. On the other hand, when the area ratio exceeds 30%, the effect of promoting the sintering is hardly improved and the manufacturing cost is increased due to excessive consumption of Mo. Moreover, the rate at which the alloy steel powder 4 is hardened by solid solution hardening increases, and the compressibility decreases. The area ratio of the Mo high concentration portion is more preferably 1 to 20%.
Mo高濃度部の面積率は、合金鋼粉４の断面をＥＰＭＡによって分析し、画像解析を行ない、Mo含有量が２質量％以上の面積を測定することによって算出できる。
以上に説明した通り、合金鋼粉４は、予合金として鉄基粉末１中に含有される元素が少ないので、合金鋼粉４の硬度が低レベルに抑えられ、合金鋼粉４の圧縮成形にて高密度の成形体が得られる。また鉄基粉末１粒子の表面にはMoが高濃度で偏析している（すなわちMo高濃度部が形成されている）ので、合金鋼粉４の成形体を焼結するときには、合金鋼粉４同士の接触面でα単一相が形成される。その結果、焼結による合金鋼粉４同士の結合が促進される。
The area ratio of the Mo high concentration part can be calculated by analyzing the cross section of the alloy steel powder 4 by EPMA, performing image analysis, and measuring the area where the Mo content is 2 mass% or more.
As described above, since the alloy steel powder 4 contains a small amount of elements contained in the iron-based powder 1 as a pre-alloy, the hardness of the alloy steel powder 4 can be suppressed to a low level, and the alloy steel powder 4 can be compressed. And a high-density molded body is obtained. Further, Mo is segregated at a high concentration on the surface of one particle of the iron-based powder (that is, a high concentration portion of Mo is formed). Therefore, when the compact of the alloy steel powder 4 is sintered, the alloy steel powder 4 An α single phase is formed at the contact surface between them. As a result, the bonding of the alloy steel powders 4 by sintering is promoted.
なお本発明では、鉄基粉末１の平均粒径は、特定の数値に限定しないが、工業的に低コストで製造される30〜120 μｍの範囲内が好適である。なお平均粒径とは、ＪＩＳ規格Z8801 の標準篩で測定した粒度分布により、積算質量分布が50％となる粒子径を指す。
以上で説明した合金鋼粉４に所定量のNi粉および／またはCu粉を配合した粉体が、本発明の粉末冶金用混合粉体である。次に、合金鋼粉４に配合するNi粉とCu粉について説明する。なお下記のNi粉とCu粉の配合量（質量％）は、合金鋼粉４の 100質量部（ 100質量％）に対する比率を指す。
In the present invention, the average particle diameter of the iron-based powder 1 is not limited to a specific numerical value, but is preferably in the range of 30 to 120 μm, which is produced at an industrially low cost. The average particle size refers to the particle size at which the cumulative mass distribution is 50% based on the particle size distribution measured with a standard sieve of JIS standard Z8801.
The powder obtained by blending the alloy steel powder 4 described above with a predetermined amount of Ni powder and / or Cu powder is the mixed powder for powder metallurgy of the present invention. Next, the Ni powder and the Cu powder blended in the alloy steel powder 4 will be described. In addition, the compounding quantity (mass%) of the following Ni powder and Cu powder refers to the ratio with respect to 100 mass parts (100 mass%) of the alloy steel powder 4.
Ni粉： 0.2〜５質量％
Ni粉は、合金鋼粉４の焼結反応を活性化し、焼結体の空孔を微細化して、焼結体の引張強度および疲労強度を高める作用を有する。Ni配合量が 0.2質量％未満では、焼結反応を活性化する効果が得られない。一方、５質量％を超えると、焼結体中の残留オーステナイトが著しく増加し、焼結体の強度が低下する。したがって、Ni粉は0.2〜５質量％の範囲で配合する必要がある。好ましくは 0.5〜３質量％である。なおNi粉は、Ni酸化物を還元して製造したNi粉や熱分解法で製造したカルボニルNi粉等の従来から知られているNi粉が使用できる。
Ni powder: 0.2-5% by mass
The Ni powder has an effect of activating the sintering reaction of the alloy steel powder 4 and making the pores of the sintered body finer to increase the tensile strength and fatigue strength of the sintered body. If the Ni content is less than 0.2% by mass, the effect of activating the sintering reaction cannot be obtained. On the other hand, when it exceeds 5% by mass, the retained austenite in the sintered body is remarkably increased and the strength of the sintered body is lowered. Therefore, it is necessary to mix | blend Ni powder in 0.2-5 mass%. Preferably it is 0.5-3 mass%. As the Ni powder, conventionally known Ni powder such as Ni powder produced by reducing Ni oxide or carbonyl Ni powder produced by a thermal decomposition method can be used.
Cu粉： 0.2〜３質量％
Cu粉は、合金鋼粉４の焼結反応にて液相を形成して焼結反応を促進するとともに、焼結体の空孔を球状化し、焼結体の引張強度および疲労強度を高める作用を有する。Cu配合量が 0.2質量％未満では、焼結体の強度を高める効果が得られない。一方、３質量％を超えると、焼結体が脆化する。したがって、Cu粉は0.2〜３質量％の範囲で配合する必要がある。好ましくは１〜２質量％である。なおCu粉は、電解Cu粉やアトマイズCu粉等の従来から知られているCu粉が使用できる。
Cu powder: 0.2-3 mass%
The Cu powder forms a liquid phase in the sintering reaction of the alloy steel powder 4 to accelerate the sintering reaction, and also spheroidizes the pores of the sintered body to increase the tensile strength and fatigue strength of the sintered body. Have If the Cu content is less than 0.2% by mass, the effect of increasing the strength of the sintered body cannot be obtained. On the other hand, if it exceeds 3% by mass, the sintered body becomes brittle. Therefore, it is necessary to mix | blend Cu powder in 0.2-3 mass%. Preferably it is 1-2 mass%. As the Cu powder, conventionally known Cu powder such as electrolytic Cu powder and atomized Cu powder can be used.
Ni粉，Cu粉は、いずれか一方のみを合金鋼粉４に配合しても良いし、あるいは両方を合金鋼粉４に配合しても良い。Ni粉またはCu粉の一方のみを配合する場合は、Ni粉を 0.2〜５質量％の範囲で配合するか、またはCu粉を 0.2〜３質量％の範囲で配合する。Ni粉およびCu粉の両方を配合する場合は、Ni粉を 0.2〜５質量％の範囲で配合し、さらにCu粉を 0.2〜３質量％の範囲で配合する。 Only one of Ni powder and Cu powder may be blended in the alloy steel powder 4, or both may be blended in the alloy steel powder 4. When only one of Ni powder and Cu powder is blended, Ni powder is blended in the range of 0.2 to 5 mass%, or Cu powder is blended in the range of 0.2 to 3 mass%. When mix | blending both Ni powder and Cu powder, it mix | blends Ni powder in the range of 0.2-5 mass%, and also mix | blends Cu powder in the range of 0.2-3 mass%.
本発明では、合金鋼粉に、Ni粉，Cu粉をバインダー（結合材）で合金鋼粉に付着させても良いし、あるいはNi粉，Cu粉を配合した後、熱処理を施して、合金鋼粉４に拡散付着させても良い。これらのようにすると、Ni粉，Cu粉の偏析を防止することができ、焼結体特性のばらつきを抑えることができる。拡散付着は圧縮性が劣化する可能性があるため、バインダーでの付着の方が好ましい。 In the present invention, Ni powder and Cu powder may be adhered to the alloy steel powder with a binder (binding material) to the alloy steel powder, or after the Ni powder and Cu powder are blended, heat treatment is performed to obtain the alloy steel. The powder 4 may be diffused and adhered. By doing so, segregation of Ni powder and Cu powder can be prevented, and variations in sintered body characteristics can be suppressed. Since diffusion adhesion may deteriorate compressibility, adhesion with a binder is preferable.
加圧成形に関しては、他に、粉末状の潤滑剤を混合しても良い。また、金型に潤滑剤を塗布あるいは付着させることができる。いずれの目的でも、潤滑剤としては、成形時の粉末同士あるいは粉末と金型間の摩擦を低減する金属石鹸（たとえばステアリン酸亜鉛，ステアリン酸リチウム，ステアリン酸カルシウム等）や脂肪酸アミド（たとえばステアリン酸アミド，エチレンビスステアロアミド，エルカ酸アミド等）の公知の潤滑剤が好適である。 In addition to the pressure molding, a powdery lubricant may be mixed. Further, a lubricant can be applied or adhered to the mold. For any purpose, lubricants include metal soaps (eg, zinc stearate, lithium stearate, calcium stearate, etc.) and fatty acid amides (eg, stearic acid amide) that reduce friction between powders during molding or between the powder and the mold. , Ethylene bisstearamide, erucamide, etc.) are known.
また、潤滑剤混合時に加熱して、合金鋼粉に、潤滑剤をバインダーとして、Ni粉，Cu粉を付着させても良い。
成形方法については、公知の方法いずれもが適合する。たとえば、鉄基粉末混合物を室温とし、金型50〜70℃に加熱する方法は、粉末の取り扱いが容易で、圧粉体密度がさらに向上するため好適である。また、粉末，金型ともに 120〜130 ℃に加熱する温間成形も使用することができる。
Further, heating may be performed when the lubricant is mixed, and Ni powder or Cu powder may be adhered to the alloy steel powder using the lubricant as a binder.
Any known method is suitable for the molding method. For example, a method in which the iron-based powder mixture is brought to room temperature and heated to a mold of 50 to 70 ° C. is suitable because the powder can be easily handled and the green compact density is further improved. Also, warm molding in which both powder and mold are heated to 120 to 130 ° C. can be used.
焼結は、1100〜1300℃程度で施すことが好ましいが、特に安価で量産可能なメッシュベルト炉で可能な1160℃以下で焼結させることが好ましい。さらに好ましくは、1140℃以下とする。
得られた焼結体には、必要に応じて、浸炭焼入れ，光輝焼入れ，高周波焼入れ，浸炭窒化熱処理等の強化処理を施すことができる。焼入れ等を施す場合は、さらに焼戻し処理を施しても良い。
Sintering is preferably performed at about 1100 to 1300 ° C., but it is particularly preferable to sinter at 1160 ° C. or lower, which is possible with a mesh belt furnace that is inexpensive and can be mass-produced. More preferably, it is set to 1140 ° C. or lower.
The obtained sintered body can be subjected to strengthening treatment such as carburizing quenching, bright quenching, induction quenching, and carbonitriding heat treatment, if necessary. When quenching or the like, a tempering process may be further performed.
以下に実施例でさらに詳細に本発明について説明するが、 本発明の粉末冶金用混合粉体とその用途は、以下の例に何ら限定されるものではない。
〔実施例１〕
所定量のMoおよびMnを含む溶鋼を水アトマイズ法によって噴霧して、アトマイズままの鉄基粉末とした。この鉄基粉末にMo原料粉末としてMoＯ3 粉末を所定の比率添加し、Ｖ型混合器で15分間混合した。
Hereinafter, the present invention will be described in more detail with reference to Examples. However, the mixed powder for powder metallurgy according to the present invention and its application are not limited to the following examples.
[Example 1]
Molten steel containing a predetermined amount of Mo and Mn was sprayed by a water atomizing method to obtain an iron-based powder as atomized. A predetermined ratio of MoO 3 powder as Mo raw material powder was added to this iron-based powder, and mixed for 15 minutes with a V-type mixer.
この混合粉を露点30℃の水素雰囲気で熱処理（保持温度 875℃，保持時間１hr）して、MoＯ3 粉末をMo金属粉末に還元するとともに、鉄基粉末の表面に拡散付着させて合金鋼粉を製造した。なお、いずれの合金鋼粉も平均粒径は70〜90μｍの範囲にあった。その合金鋼粉に平均粒径４μｍのNi粉および平均粒径20μｍのCu粉を配合し、Ｖ型混合機で15分間混合し、粉末冶金用混合粉体とした。このようにして得られた粉末冶金用混合粉体は、表１に示す通りである。 This mixed powder is heat-treated in a hydrogen atmosphere with a dew point of 30 ° C (holding temperature: 875 ° C, holding time: 1 hour) to reduce the MoO 3 powder to Mo metal powder and to diffusely adhere it to the surface of the iron-based powder. Manufactured. All alloy steel powders had an average particle size in the range of 70 to 90 μm. The alloy steel powder was mixed with Ni powder having an average particle diameter of 4 μm and Cu powder having an average particle diameter of 20 μm and mixed for 15 minutes with a V-type mixer to obtain a mixed powder for powder metallurgy. The mixed powder for powder metallurgy thus obtained is as shown in Table 1.
試料No. ７〜９は、Mo予合金量，Mn予合金量，Mo拡散付着量，Ni粉配合量，Cu粉配合量が本発明の範囲を満足する例である。試料No. 10は、Mo予合金量が本発明の範囲を外れる例，試料No. ６，11は、Mn予合金量が本発明の範囲を外れる例である。
試料No. 13〜15は、Mo予合金量，Mn予合金量，Mo拡散付着量，Ni粉配合量が本発明の範囲を満足する例である。試料No. 12は、Ni粉配合量が本発明の範囲を外れる例である。
Sample Nos. 7 to 9 are examples in which the Mo prealloy amount, the Mn prealloy amount, the Mo diffusion adhesion amount, the Ni powder blending amount, and the Cu powder blending amount satisfy the scope of the present invention. Sample No. 10 is an example in which the Mo pre-alloy amount is outside the range of the present invention, and Sample Nos. 6 and 11 are examples in which the Mn pre-alloy amount is outside the range of the present invention.
Sample Nos. 13 to 15 are examples in which the Mo prealloy amount, the Mn prealloy amount, the Mo diffusion adhesion amount, and the Ni powder blending amount satisfy the scope of the present invention. Sample No. 12 is an example in which the amount of Ni powder is outside the scope of the present invention.
試料No. 17〜19は、Mo予合金量，Mn予合金量，Mo拡散付着量，Cu粉配合量が本発明の範囲を満足する例である。試料No. 16，20は、Cu粉配合量が本発明の範囲を外れる例である。
これらの粉末冶金用混合粉体 100質量部に合金化用粉末として黒鉛 0.3質量部と潤滑剤としてステアリン酸リチウム 0.8質量部を添加して、Ｖ型混合機で15分間混合した。次いで、粉末冶金用混合粉体を 130℃に加熱し、さらに金型（温度： 130℃）に充填して加圧成形（圧力：686MPa）した。
Sample Nos. 17 to 19 are examples in which the Mo prealloy amount, the Mn prealloy amount, the Mo diffusion adhesion amount, and the Cu powder blending amount satisfy the scope of the present invention. Samples Nos. 16 and 20 are examples in which the amount of Cu powder is outside the scope of the present invention.
To 100 parts by mass of these powders for powder metallurgy, 0.3 parts by mass of graphite as an alloying powder and 0.8 parts by mass of lithium stearate as a lubricant were added and mixed for 15 minutes with a V-type mixer. Next, the powder mixture for powder metallurgy was heated to 130 ° C., and further filled in a mold (temperature: 130 ° C.) and subjected to pressure molding (pressure: 686 MPa).
この成形体に、ＲＸ雰囲気（Ｎ2 −32体積％Ｈ2 −24体積％ＣＯ− 0.3体積％ＣＯ2 ）中で焼結（焼結温度1130℃，焼結時間20分）を施して、焼結体とした。得られた焼結体にカーボンポテンシャル 0.8質量％でガス浸炭（保持温度 870℃，保持時間60分）した後、焼入れ（焼入れ温度60℃，油焼入れ）および焼戻し（焼戻し温度 200℃，焼戻し時間60分）を行なった。なお、カーボンポテンシャルは、鋼を加熱する雰囲気の浸炭能力を示す指標であり、その温度で、そのガス雰囲気と平衡に達したときの鋼の表面の炭素濃度で表わす。 This molded body was sintered (sintering temperature 1130 ° C., sintering time 20 minutes) in RX atmosphere (N 2 −32 vol% H 2 −24 vol% CO−0.3 vol% CO 2 ) It was a ligation. The obtained sintered body was gas carburized at a carbon potential of 0.8% by mass (holding temperature 870 ° C, holding time 60 minutes), then quenched (quenching temperature 60 ° C, oil quenching) and tempered (tempering temperature 200 ° C, tempering time 60). Min). The carbon potential is an index indicating the carburizing ability of the atmosphere in which the steel is heated, and is represented by the carbon concentration on the surface of the steel when equilibrium is reached with the gas atmosphere at that temperature.
この焼結体の密度，引張強度，回転曲げ疲労強度を測定した。その結果は表２に示す通りである。なお、密度は、ＪＩＳ規格Z2501 に準拠して測定した。引張強度は、平行部の直径５mm，長さ15mmの小型丸棒試験片を焼結体から採取して、室温で引張試験を行なって測定した。回転曲げ疲労強度は、平行部の直径８mm，長さ15.4mmの平滑丸棒試験片を採取し、小野式回転曲げ疲労試験機を用いて107 回で破壊を生じない荷重から算出した。 The density, tensile strength, and rotational bending fatigue strength of this sintered body were measured. The results are as shown in Table 2. The density was measured according to JIS standard Z2501. The tensile strength was measured by taking a small round bar test piece having a diameter of 5 mm and a length of 15 mm at the parallel portion from the sintered body and performing a tensile test at room temperature. The rotational bending fatigue strength was calculated from a load that did not cause breakage in 10 7 times using a smooth round bar test piece having a diameter of 8 mm and a length of 15.4 mm at the parallel part, and using an Ono type rotary bending fatigue tester.
試料No. ６〜11の中の発明例（試料No. ７〜９）と比較例（試料No. ６，10，11）を比べると、密度，引張強度，回転曲げ疲労強度は、いずれも発明例の方が優れていた。
試料No. 12〜15の中の発明例（試料No. 13〜15）と比較例（試料No. 12）を比べると、密度の差異は認められなかったが、引張強度と回転曲げ疲労強度は発明例の方が優れていた。
Comparing the invention examples (sample Nos. 7-9) in sample Nos. 6-11 with the comparative examples (sample Nos. 6, 10, 11), the density, tensile strength, and rotational bending fatigue strength were all invented. The example was better.
When comparing the invention example (sample No. 13-15) in sample Nos. 12-15 and the comparative example (sample No. 12), no difference in density was observed, but the tensile strength and rotational bending fatigue strength were The inventive example was superior.
試料No. 16〜20の中の発明例（試料No. 17，19）と比較例（試料No. 16，20）を比べると、密度の差異は認められなかったが、引張強度と回転曲げ疲労強度は発明例の方が優れていた。
〔実施例２〕
実施例１と同様の方法で、所定量のMo，Mnを予合金し、所定量のMoあるいはFe−10Mo，Fe−50Mo水アトマイズ鉄粉を表面に拡散付着している合金鋼粉を製造した。その合金鋼粉に、所定量の平均粒径４μｍのNi粉， 0.3質量％の黒鉛粉，潤滑剤兼バインダーとして 0.6質量部のエチレンビスステアロアミドを添加し、 160℃に加熱しながら10分間混合し、Ni粉を合金鋼粉表面に付着させた（試料No. 26，29，30）。No.31 については、バインダーを添加して、加熱，混合の処理を行なった後で、Ni粉を添加し混合したが、それ以外は同様の処理で混合粉体とした。試料No. 32，33については、焼結を強化した（1250℃，60分，Ｎ2 −10 vol％Ｈ2 ）。
When the invention examples (Sample Nos. 17 and 19) in Sample Nos. 16 to 20 and the comparative examples (Sample Nos. 16 and 20) were compared, no difference in density was observed, but tensile strength and rotational bending fatigue The strength of the inventive example was superior.
[Example 2]
In the same manner as in Example 1, a predetermined amount of Mo, Mn was pre-alloyed, and an alloy steel powder having a predetermined amount of Mo or Fe-10Mo, Fe-50Mo water atomized iron powder diffused and adhered to the surface was produced. . To the alloy steel powder, a predetermined amount of Ni powder having an average particle size of 4 μm, 0.3 mass% graphite powder, 0.6 mass parts of ethylene bisstearamide as a lubricant and binder are added and heated to 160 ° C. for 10 minutes. After mixing, Ni powder was adhered to the surface of the alloy steel powder (Sample Nos. 26, 29, 30). For No. 31, the binder was added and the mixture was heated and mixed, and then Ni powder was added and mixed. Otherwise, the powder was mixed in the same manner. For sample Nos. 32 and 33, sintering was strengthened (1250 ° C., 60 minutes, N 2 −10 vol% H 2 ).
また、Ni粉を鉄基粉末の表面に拡散付着させた合金鋼粉も製造した（試料No.27 ）。また、比較として、Niを所定量のMo，Mnと同時に予合金し、所定量のMoを表面に拡散付着している合金鋼粉も製造した（試料No.28 ）。これらの合金鋼粉に、 0.3質量％の黒鉛粉，潤滑剤兼バインダーとして 0.6質量部のエチレンビスステアロアミドを添加し、 160℃に加熱しながら10分間混合した。 An alloy steel powder was also produced in which Ni powder was diffused and adhered to the surface of the iron-based powder (Sample No. 27). For comparison, Ni alloy was prealloyed simultaneously with a predetermined amount of Mo and Mn, and an alloy steel powder in which a predetermined amount of Mo was diffused and adhered to the surface was also produced (Sample No. 28). To these alloy steel powders, 0.3% by mass of graphite powder and 0.6 parts by mass of ethylene bisstearamide as a lubricant and binder were added and mixed for 10 minutes while heating to 160 ° C.
これらの混合粉体を実施例１と同様な方法で、成形，焼結，浸炭を行なった。次いで、これらの焼結体の密度，引張強度，回転曲げ疲労強度，平均空孔径を求めた。その結果は、表３，４に示す通りである。なお、平均空孔径は、鏡面研磨した50cm2 の像を画像解析して求めた。 These mixed powders were molded, sintered, and carburized in the same manner as in Example 1. Next, the density, tensile strength, rotational bending fatigue strength, and average pore diameter of these sintered bodies were determined. The results are as shown in Tables 3 and 4. The average pore diameter was obtained by image analysis of a mirror-polished 50 cm 2 image.
〔実施例３〕
実施例１と同様の方法で、所定量のMo，Mnを予合金し、所定量のMoを混合した。その混合粉を、露点30℃の水蒸気雰囲気で熱処理（保持温度： 875〜1000℃，保持時間：１hrして、合金鋼粉を製造した。このようにして得られた合金鋼粉は、表５に示す通りである。
Example 3
In the same manner as in Example 1, a predetermined amount of Mo and Mn were pre-alloyed and a predetermined amount of Mo was mixed. The mixed powder was heat-treated in a steam atmosphere with a dew point of 30 ° C. (holding temperature: 875 to 1000 ° C., holding time: 1 hr to produce alloy steel powder. The alloy steel powder thus obtained is shown in Table 5. As shown in
合金鋼粉のMo高濃度部の面積率は、合金鋼粉を樹脂に埋め込んだ後、研摩し、10個の粒子の断面をＥＰＭＡで分析して画像解析を行ない、Mo含有量が２質量％以上の面積を測定し、得られた10個の測定値を平均して算出した。
これらの合金鋼粉の密度，引張強度，回転曲げ疲労強度を、〔実施例１〕と同じ方法で測定した。その結果は表６に示す通りである。
The area ratio of the high concentration part of Mo in the alloy steel powder is determined by embedding the alloy steel powder in the resin and then polishing, analyzing the cross section of 10 particles with EPMA, and performing Mo analysis. The above areas were measured, and the ten measured values obtained were averaged.
The density, tensile strength, and rotational bending fatigue strength of these alloy steel powders were measured by the same method as in [Example 1]. The results are as shown in Table 6.
１ 鉄基粉末
２ Mo含有合金
３ 接触する部位
４ 合金鋼粉
1 Iron-based
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