JP3795402B2 - Cast iron-based sintered sliding member and manufacturing method thereof - Google Patents
Cast iron-based sintered sliding member and manufacturing method thereof Download PDFInfo
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- 229910001018 Cast iron Inorganic materials 0.000 title claims description 45
- 238000004519 manufacturing process Methods 0.000 title claims description 15
- 239000000463 material Substances 0.000 claims description 49
- 229910001060 Gray iron Inorganic materials 0.000 claims description 43
- 238000005266 casting Methods 0.000 claims description 38
- 229910045601 alloy Inorganic materials 0.000 claims description 33
- 239000000956 alloy Substances 0.000 claims description 33
- 238000000034 method Methods 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 24
- 239000011248 coating agent Substances 0.000 claims description 23
- 238000000576 coating method Methods 0.000 claims description 23
- 239000003921 oil Substances 0.000 claims description 21
- 238000005520 cutting process Methods 0.000 claims description 19
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 17
- 239000010687 lubricating oil Substances 0.000 claims description 17
- 238000001816 cooling Methods 0.000 claims description 11
- 238000005470 impregnation Methods 0.000 claims description 11
- 230000009466 transformation Effects 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 8
- 238000000465 moulding Methods 0.000 claims description 8
- 238000005245 sintering Methods 0.000 claims description 7
- 230000006835 compression Effects 0.000 claims description 6
- 238000007906 compression Methods 0.000 claims description 6
- 230000007935 neutral effect Effects 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 5
- 238000011068 loading method Methods 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 2
- 239000002245 particle Substances 0.000 description 33
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 28
- 239000010439 graphite Substances 0.000 description 21
- 229910002804 graphite Inorganic materials 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 15
- 239000011812 mixed powder Substances 0.000 description 12
- 230000001186 cumulative effect Effects 0.000 description 8
- 230000013011 mating Effects 0.000 description 6
- 238000005461 lubrication Methods 0.000 description 5
- 239000011572 manganese Substances 0.000 description 5
- 229910000859 α-Fe Inorganic materials 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000004519 grease Substances 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 230000001050 lubricating effect Effects 0.000 description 4
- 229910000975 Carbon steel Inorganic materials 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 239000010962 carbon steel Substances 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 229910052737 gold Inorganic materials 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 238000000748 compression moulding Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- 239000010953 base metal Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
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- 238000010304 firing Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- CDRCPXYWYPYVPY-UHFFFAOYSA-N iron(2+) oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Fe+2].[Fe+2].[Fe+2].[Fe+2] CDRCPXYWYPYVPY-UHFFFAOYSA-N 0.000 description 1
- 239000010721 machine oil Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 239000010705 motor oil Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
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Description
【０００１】
【発明の属する技術分野】
本発明は、成長ねずみ鋳鉄鋳物を切削して得られた切粉を使用した鋳鉄系焼結摺動部材及びその製造方法に関する。
【０００２】
【従来の技術】
従来から、炭素が片状黒鉛の形で存在しているねずみ鋳鉄が知られている。このねずみ鋳鉄から作製された鋳物（ねずみ鋳鉄鋳物）は、大きな振動吸収能と高い熱伝導性を有することから内燃機関用材料として広く用いられている。また、ねずみ鋳鉄は優れた鋳造性を有することから、流体機械やバルブなど形状が複雑なものが多い産業機械器具材料としても広く用いられている。さらに、ねずみ鋳鉄鋳物を長時間加熱したり加熱冷却を繰り返したりすることによってこの鋳物を成長させ、この成長によって生じた多孔質部（ポーラス部）に潤滑油を含浸させることにより摺動性に優れた含油摺動部材が得られることが知られており、この含油摺動部材は軸受や滑り板などの摺動用途に広く用いられている。
【０００３】
上述した各種用途に使用されるねずみ鋳鉄鋳物は、荒引き加工、中引き加工、仕上げ加工、場合によっては研削加工などの機械加工を経て最終製品となる。ねずみ鋳鉄鋳物にこれらの機械加工を施す際には、各加工工程で鋳鉄の切粉が生じる。このようにして生じた切粉の大部分は、通常、廃棄処分されている。
【０００４】
廃棄処分されるねずみ鋳鉄鋳物の切粉に着目し、この切粉を積極的に利用した技術として、例えば特公昭５８−２１００２号公報に開示された技術が知られている。この技術は、ねずみ鋳鉄の粉末（切屑）を４トン／ｃｍ２以上の成形圧力で成形して成形品を得、その後、鋳鉄に対して弱脱炭素性雰囲気もしくは中性雰囲気であるアンモニア分解ガス雰囲気又はドライ水素雰囲気において上記の成形品を少なくとも１０１０℃の温度で焼結し、１０ｋｇ／ｍｍ２以上の引張り強さを有する焼結成形体を製造する技術である。
【０００５】
また、上記の切粉を使用して軸受などの摺動用途の焼結成形体を製造する技術としては、例えば特公昭５８−１２３２１号公報に開示された技術が知られている。この技術は、鋳造品を切削又は研削して得られた切屑を粉砕することによりねずみ鋳鉄粉末を生成し、このねずみ鋳鉄粉末９０重量％乃至９９．５重量％に炭素粉末０．５重量％乃至１０重量％を混合して混合粉末を作製し、この混合粉末を圧縮成形した後に焼結成形体を製造する技術である。
【０００６】
上述したように、特公昭５８−２１００２号公報に開示された技術によれば、１０ｋｇ／ｍｍ２以上の引張り強さを有する焼結成形体が製造されるので、この技術（製造方法）で製造された焼結成形体は機械部品として有効に利用され得るものである。しかし、この焼結成形体には、潤滑性に寄与する遊離黒鉛の含有量が少ないので、この焼結成形体は摩擦・摩耗等の摺動特性に劣る。従って、この焼結成形体を軸受などの摺動用部品として使用するに当たっては、潤滑条件や使用条件などを十分に注意しなければならない、という問題がある。
【０００７】
また、特公昭５８−１２３２１号公報に開示された技術では、焼結成形体に潤滑性を付与する目的で炭素粉末を含有している。しかし、この炭素粉末は焼結性を阻害する原因となり、この結果、焼結成形体の強度が弱いという欠点がある。このような欠点をもつ焼結成形体は摺動用部品としては使用し難い、という問題がある。
【０００８】
【発明が解決しようとする課題】
上述した問題を解決するために、本願出願人は先に、特願２００１−６００２号（以下「先行技術」という）において、摺動特性に優れた鋳鉄系焼結摺動部材及びその製造方法を提案した。この先行技術は、成長ねずみ鋳鉄鋳物を切削し、この切削によって得られた切粉を所定の金型内に装填し、この装填した切粉を３トン／ｃｍ２以上５トン／ｃｍ２以下の範囲内の成形圧力で圧縮成形して圧粉体を形成し、中性雰囲気または還元性雰囲気において１１００℃以上１１５０℃以下の範囲の温度で３０分間以上９０分間以下の時間内だけ前記圧粉体を焼結して鋳鉄系焼結摺動部材を製造する方法である。この製造方法によって得られた鋳鉄系焼結摺動部材は、遊離黒鉛が全体にわたって分散含有されているので摩擦摩耗特性に優れており、軸受や滑り板などの摺動用部品に適用できるものである。
【０００９】
本発明は、上記先行技術を有効に利用すると共に、先行技術で得られた鋳鉄系焼結摺動部材の摩擦摩耗特性をさらに向上させた鋳鉄系焼結摺動部材及びその製造方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するための本発明の鋳鉄系焼結摺動部材は、
（１）成長ねずみ鋳鉄鋳物を切削することによって生じる切粉を焼結してなる焼結合金を母材とし、この母材の少なくとも摺動表面に四三酸化鉄の被膜が形成されていることを特徴とするものである。
【００１１】
ここで、
（２）前記四三酸化鉄の被膜は、２μｍ以上５μｍ以下の範囲内の厚さを有するものであってもよい。
【００１２】
さらに、
（３）前記四三酸化鉄の被膜は、ビッカース硬さ（ＨｍＶ）が４４０以上５６０以下の範囲内のものであってもよい。
【００１３】
さらにまた、前記鋳鉄系焼結摺動部材は、
（４）その総体積の７体積％以上１５体積％以下の範囲内の潤滑油が含有されているものであってもよい。
【００１４】
また、上記目的を達成するための本発明の鋳鉄系焼結摺動部材の製造方法は、（５）成長ねずみ鋳鉄鋳物を切削し、
（６）この切削によって得られた切粉を所定の金型内に装填し、
（７）この装填した切粉を３トン／ｃｍ２以上５トン／ｃｍ２以下の範囲内の成形圧力で圧縮成形して圧粉体を形成し、
（８）中性雰囲気または還元性雰囲気において１１００℃以上１１５０℃以下の範囲内の温度で３０分間以上９０分間以下の時間内だけ前記圧粉体を焼結して焼結合金母材を作製し、
（９）この焼結合金母材に水蒸気処理を施して少なくとも摺動表面に四三酸化鉄の被膜を形成させて鋳鉄系焼結摺動部材を製造することを特徴とするものである。
【００１５】
ここで、
（１０）前記成長ねずみ鋳鉄鋳物を得るに当たり、ねずみ鋳鉄鋳物のＡ１変態点よりも高い温度とＡ１変態点よりも低い温度との間で加熱冷却を繰り返す反覆加熱冷却処理をねずみ鋳鉄鋳物に施すことにより前記成長ねずみ鋳鉄鋳物を得てもよい。
【００１６】
さらに、
（１１）前記切粉を所定の金型内に装填するに当たり、２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を総重量の８５重量％以上９７重量％以下の範囲内で前記金型内に装填すると共に、５５メッシュの篩を通過する切粉を総重量の３重量％以上１５重量％以下の範囲内で前記金型内に装填してもよい。
【００１７】
さらにまた、
（１２）２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を前記金型内に装填するに当たり、該切粉の総重量のうち、１０重量％以上９０重量％以下の範囲内であって２０メッシュの篩を通過するが３６メッシュの篩を通過しない切粉と、１０重量％以上９０重量％以下の範囲内であって３６メッシュの篩を通過するが５５メッシュの篩を通過しない切粉とを混合して前記金型内に装填してもよい。
【００１８】
さらにまた、
（１３）前記水蒸気処理は、処理温度が４５０℃以上５５０℃以下の範囲内であって、６０分間以上９０分間以下の時間内で行ってもよい。
【００１９】
さらにまた、
（１４）前記鋳鉄系焼結摺動部材に含油処理を施すに当たり、含油率が該鋳鉄系焼結摺動部材の総体積の７体積％以上１５体積％以下の範囲内になるように該鋳鉄系焼結摺動部材に含油処理を施してもよい。
【００２０】
上記した四三酸化鉄の被膜について説明する。
【００２１】
焼結摺動部材の観点からは、四三酸化鉄の被膜は少なくとも焼結摺動部材の摺動表面に形成されていればよい。しかし、四三酸化鉄による防錆作用を考慮した場合は、摺動部材の全ての表面に四三酸化鉄の被膜を形成することが好ましく、これにより、摩擦摩耗特性の向上に加えて焼結摺動部材に耐蝕性、耐錆性を付与できる。
【００２２】
また、四三酸化鉄の被膜の厚さが２μｍ未満の場合は、摺動特性、特に耐摩耗性の向上に効果が認められにくい。一方、この被膜の厚さが5μｍを超えた場合は、焼結合金母材の多孔部を封孔させる割合が多くなり、焼結合金母材に含浸される潤滑油の含油率を低下させるおそれがある。このような観点からは、四三酸化鉄の被膜は、２μｍ以上５μｍ以下の範囲内の厚さを有するものが好ましい。
【００２３】
ところで、焼結合金母材の硬さを高めて耐摩耗性を向上させる技術としては、例えば焼結合金母材に焼入れを施し、表面硬さを高める技術が知られている。しかし、この技術では、８００℃以上の高温で焼入れをするので、焼結合金母材の組織に大きな変化をもたらす。一方、水蒸気処理では、４５０以上５５０℃以下の範囲で行われるので、焼結合金母材の組織に影響を及ぼすことがなく、焼入れと同等の硬さを得ることができる。四三酸化鉄の被膜の表面硬さがビッカース硬さ（ＨｍＶ）４４０未満の場合は、耐摩耗性の向上に効果が認められにくく、一方、四三酸化鉄の被膜の表面硬さがビッカース硬さ５６０を超えた場合は相手材表面を損傷させる虞がある。このような観点から、四三酸化鉄の被膜の表面硬さはビッカース硬さ４５０以上５６０以下の範囲内であることが好ましい。
【００２４】
また、潤滑油を含有させるに際しては、周知の加熱含浸法や真空含浸法を用いる。潤滑油としては、エンジン油やマシン油などの鉱油を使用する。
【００２５】
【発明の実施の形態】
＜焼結合金母材の作製＞
【００２６】
炭素（Ｃ）２．５〜４．０重量％（２．５重量％以上４．０重量％以下を表しており、以下同様である）、珪素（Ｓｉ）０．５〜３．５重量％、マンガン（Ｍｎ）０．２〜１．０重量％、燐（Ｐ）０．０３〜０．８重量％、硫黄（Ｓ）０．０１〜０．１２重量％、残部鉄（Ｆｅ）からなるねずみ鋳鉄鋳物に、このねずみ鋳鉄鋳物のＡ１変態点（７２３℃）よりも高い温度とＡ１変態点よりも低い温度との間で加熱冷却を繰り返す反覆加熱冷却処理を施し、素地中の片状黒鉛を肥大成長させた成長ねずみ鋳鉄鋳物を得る。成長ねずみ鋳鉄鋳物としては、素地がオールフェライト組織のものが好ましい。ここで、素地がオールフェライト組織とは、素地がフェライト組織だけからなることをいうが、フェライト組織以外にパーライト組織など他の組織が僅かに存在する素地も、ここでいうオールフェライト組織に含まれる。
【００２７】
この成長ねずみ鋳鉄鋳物に荒引き、中引き及び仕上げの切削加工を施し、この成長ねずみ鋳鉄の切粉を得る。このようにして得られた切粉の素地中には、成長によって肥大化した片状黒鉛が多く含まれており、これらの片状黒鉛が表面に露出している割合は多い。この割合は、一般のねずみ鋳鉄鋳物を切削して得られた切粉の表面に露出している片状黒鉛の割合よりも多い。
【００２８】
次に、切削加工の各工程で得られた切粉を、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉と、５５メッシュの篩を通過する粒度の切粉とに選別する。さらに、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉を、２０メッシュの篩を通過するが３６メッシュの篩を通過しない粒度の切粉と、３６メッシュを通過するが５５メッシュの篩を通過しない粒度の切粉とに選別する。
【００２９】
上記のように選別した切粉のうち、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉は主として焼結合金母材の骨格を形成する。また、５５メッシュの篩を通過する粒度の切粉では、切粉中に占める黒鉛量が多い。従って、５５メッシュの篩を通過する切粉を焼結合金母材全体に分散して含有させることにより、この焼結合金母材は、黒鉛等の潤滑性成分を別途に含有させなくても、潤滑作用を発揮する。
【００３０】
選別した各粒度の切粉のうち、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉８５〜９７重量％と、５５メッシュの篩を通過する粒度の切粉３〜１５重量％とを混合して混合粉末を作製する。ここでは、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉のうち、２０メッシュの篩を通過するが３６メッシュの篩を通過しない粒度の切粉１０〜９０重量％と、３６メッシュを通過するが５５メッシュの篩を通過しない粒度の切粉１０〜９０重量％とを混合した切粉８５〜９７重量％に対し、５５メッシュの篩を通過する粒度の切粉３〜１５重量％を混合した混合粉末になるように作製する。なお、各切粉の重量％は、作製した混合粉末の総重量に対する割合である。
【００３１】
このようにして得た混合粉末を金型中に装填し、３トン／ｃｍ２以上５トン／ｃｍ２以下の範囲内の成形圧力で圧縮成形して圧粉体を作製する。この圧粉体を、中性雰囲気または還元性雰囲気において１１００℃以上１１５０℃以下の範囲内の温度で３０分間以上９０分間以下の範囲内の時間だけ焼結して焼結合金母材を作製する。
【００３２】
＜鋳鉄系焼結摺動部材の製造＞
【００３３】
上記のようにして得た焼結合金母材を加熱炉内に置き、加熱炉内の温度を４５０℃以上５５０℃以下の範囲内に昇温して、この温度を保持した状態で加熱炉内に水蒸気を６０分間以上９０分間以下の時間内で連続して噴射して焼結合金母材に水蒸気処理を施す。この水蒸気処理により、焼結合金母材の摺動表面に２μｍ以上５μｍ以下の範囲内の厚さであって、ビッカース硬さが４４０以上５６０以下の範囲内の四三酸化鉄の被膜を形成させる。水蒸気処理を施すに当たり、処理温度及び処理時間は、焼結合金母材の摺動表面に形成される四三酸化鉄の被膜の巧拙（被膜が一様な厚さを有するか否か）、焼結合金母材に含有されている遊離炭素（黒鉛）の脱炭、多孔部の封孔等に影響を及ぼすので重要な要素となる。このようにして、少なくとも摺動表面に四三酸化鉄の被膜が形成された鋳鉄系焼結摺動部材が製造される。
【００３４】
上記鋳鉄系焼結摺動部材に含油処理を施すことにより、７体積％以上１５体積％以下の含油率の鋳鉄系含油焼結摺動部材が得られる。従って、鋳鉄系含油焼結摺動部材には、７体積％以上１５体積％以下の範囲内の潤滑油が含有されていることとなる。
【００３５】
この鋳鉄系焼結摺動部材には、少なくとも摺動表面には四三酸化鉄の硬質な被膜と、遊離黒鉛と、多孔部及び遊離黒鉛に含有された潤滑油とが存在するので、相手材との摺動においては、先行技術において提案した鋳鉄系焼結摺動部材に比較して、摩擦摩耗特性の大幅な向上を図ることができる。
【００３６】
【実施例】
以下、本発明の実施例について詳細に説明する。本発明はこれらの例に何等限定されるものではない。
【００３７】
〔実施例１〕
【００３８】
３．６５重量％の炭素（Ｃ）、２．２２重量％の珪素（Ｓｉ）、０．４５重量％のマンガン（Ｍｎ）、０．０４５重量％の燐（Ｐ）、０．０８４重量％の硫黄（Ｓ）、残部鉄（Ｆｅ）からなる組成を有し、内径３３ｍｍ、外径５４ｍｍ、長さ２０３ｍｍの円筒状ねずみ鋳鉄鋳物（ＦＣ１５０）を作製した。このねずみ鋳鉄鋳物のＡ１変態点（７２３℃）よりも高い温度と低い温度との間で加熱冷却を繰り返す（Ａ１変態点をはさんで上下する）反復加熱冷却処理によって、ねずみ鋳鉄素地中の片状黒鉛を肥大成長させると共に、この成長に伴い片状黒鉛の周囲を多孔質化させた。このようにして成長ねずみ鋳鉄鋳物を得た。
【００３９】
上記の成長ねずみ鋳鉄鋳物の表面に生成した酸化スケールを除去し、その後、この成長ねずみ鋳鉄鋳物に荒引き、中引き及び仕上げの切削加工を施し、内径４０ｍｍ、外径５０ｍｍ、長さ４０ｍｍの軸受ブッシュを作製した。このようにして成長ねずみ鋳鉄鋳物を切削加工して軸受ブッシュを作製する際に多量の切粉が生じた。これら多量の切粉を、２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉と、５５メッシュの篩を通過する切粉とに選別した。
【００４０】
さらに、２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を、２０メッシュの篩を通過するが３６メッシュの篩を通過しない切粉と、３６メッシュの篩を通過するが５５メッシュの篩を通過しない切粉とに選別した。
【００４１】
上記のように選別した各粒度の切粉の中から、２０メッシュの篩を通過するが３６メッシュの篩を通過しない切粉を総重量の５６重量％、３６メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を総重量の３６重量％、５５メッシュの篩を通過する切粉を総重量の８重量％、それぞれ計量した。各切粉の組成を表１に示す。
【表１】
表１において、−２０メッシュは、２０メッシュの篩を通過することを表し、＋５５メッシュは、５５メッシュの篩を通過しないことを表す。なお、以下の各表においても同様である。
【００４３】
上記のようにして選別し計量した各切粉を混合して混合粉末を作製した。ついで、この混合粉末を直方体状の中空部を有する金型内に装填し、成形圧力４トン／ｃｍ２で圧縮成形して圧粉体を作製した。その後、水素ガス雰囲気（本発明にいう中性雰囲気または還元性雰囲気の一例である）に調整した加熱炉において、この圧粉体を１１３０℃の温度で６０分間焼結し、直方体状の焼結体を得た。このようにして得た焼結体を切削加工して、一辺が３０ｍｍ、厚さ５ｍｍの横断面正方形状の焼結合金母材を作製した。
【００４４】
ついで、焼結合金母材を加熱炉内に置き、加熱炉内の温度を４８０℃に昇温した後、この温度を保持した状態で加熱炉内に水蒸気を９０分間連続して噴射し、焼結合金母材に水蒸気処理を施した。この水蒸気処理により、焼結合金母材の表面に厚さ３μｍの四三酸化鉄の被膜が形成された鋳鉄系焼結摺動部材を得た。四三酸化鉄の被膜はビッカース硬さ（ＨｍＶ）４４２であった。また、この鋳鉄系焼結摺動部材に含油処理を施したところ、潤滑油の含油率は１０．３体積％であった。
【００４５】
〔実施例２〕
【００４６】
上記した実施例１と同様にして、成長ねずみ鋳鉄鋳物を切削加工して軸受ブッシュを作製する際に生じた切粉を、２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉と、５５メッシュの篩を通過する切粉とに選別した。
【００４７】
さらに、２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を、２０メッシュの篩を通過するが３６メッシュの篩を通過しない切粉と、３６メッシュの篩を通過するが５５メッシュの篩を通過しない切粉とに選別した。このようにして選別した各粒度の切粉の中から、２０メッシュの篩を通過するが３６メッシュの篩を通過しない切粉を総重量の３０重量％、３６メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を総重量の６０重量％、５５メッシュの篩を通過する切粉を総重量の１０重量％、それぞれ計量した。各切粉の組成を表２に示す。
【表２】
上記のようにして選別し計量した各切粉を混合して混合粉末を形成した。ついで、この混合粉末を直方体状の中空部を有する金型内に装填し、成形圧力４トン／ｃｍ２で圧縮成形して圧粉体を作製した。その後、実施例１と同様に、水素ガス雰囲気に調整した加熱炉において、この圧粉体を１１３０℃の温度で６０分間焼結し、直方体状の焼結体を得た。このようにして得た焼結体を切削加工して、一辺が３０ｍｍ、厚さ５ｍｍの横断面正方形状の焼結合金母材を作製した。
【００４９】
ついで、焼結合金母材を加熱炉内に置き、加熱炉内の温度を５５０℃に昇温した後、この温度を保持した状態で加熱炉内に水蒸気を６０分間連続して噴射し、焼結合金母材に水蒸気処理を施した。この水蒸気処理により、焼結合金母材の表面に厚さ５μｍの四三酸化鉄の被膜が形成された鋳鉄系焼結摺動部材を得た。四三酸化鉄の被膜はビッカース硬さ（ＨｍＶ）５０３であった。また、この鋳鉄系焼結摺動部材に含油処理を施したところ、潤滑油の含油率は９．６体積％であった。
【００５０】
〔比較例１〕
【００５１】
３．６５重量％のＣ、２．２２重量％のＳｉ、０．４５重量％のＭｎ、０．０４５重量％のＰ、０．０８４重量％のＳ、残部Ｆｅからなり、内径３３ｍｍ、外径５４ｍｍ、長さ２０３ｍｍの円筒状ねずみ鋳鉄鋳物（ＦＣ１５０）を作製した。このねずみ鋳鉄鋳物に荒引き、中引き及び仕上げの各切削加工を施し、内径４０ｍｍ、外径５０ｍｍ、長さ４０ｍｍの軸受ブッシュを作製した。このようにしてねずみ鋳鉄鋳物を切削加工して軸受ブッシュを作製する際には多量の切粉が生じた。これら多量の切粉を、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉と、５５メッシュの篩を通過する粒度の切粉とに選別した。
【００５２】
さらに、２０メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉を、２０メッシュの篩を通過するが３６メッシュの篩を通過しない粒度の切粉と、３６メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉とに選別した。
【００５３】
上記のように選別した各粒度の切粉の中から、２０メッシュの篩を通過するが３６メッシュの篩を通過しない粒度の切粉を総重量の５６重量％、３６メッシュの篩を通過するが５５メッシュの篩を通過しない粒度の切粉を総重量の３６重量％、５５メッシュの篩を通過する粒度の切粉を総重量の８重量％、それぞれ計量した。各切粉の組成を表３に示す。
【表３】
上記のように選別し計量した各切粉を混合して混合粉末を形成した。ついで、この混合粉末を直方体状の中空部を有する金型内に装填し、成形圧力４トン／ｃｍ２で圧縮成形して圧粉体を作製した。その後、加熱炉において、この圧粉体を１１３０℃の温度で６０分間焼結して焼結体を得た。この焼結体を切削加工して、一辺が３０ｍｍ、厚さ５ｍｍの横断面正方形状の焼結摺動部材を製造した。この鋳鉄系焼結摺動部材に含油処理を施したところ、潤滑油の含油率は１２．３体積％であった。
【００５５】
〔比較例２〕
【００５６】
実施例１と同様の成分組成であって、同様の粒度分布の切粉を使用し、かつ同様の条件で焼結した一辺が３０ｍｍ、厚さ５ｍｍの横断面正方形状の焼結合金母材を焼結摺動部材とした。この鋳鉄系焼結摺動部材に含油処理を施したところ、潤滑油の含油率は１２．２体積％であった。この比較例２の焼結摺動部材は、上記した先行技術の焼結摺動部材に相当するものである。
【００５７】
つぎに、上記した実施例１、実施例２、比較例１、及び比較例２で得た焼結摺動部材について、下記に示す試験条件により耐荷重試験を行った。
【００５８】
〔耐荷重試験〕
試験条件
すべり速度 ：３ｍ／ｍｉｎ
荷重（面圧）：１０分間毎に３０ｋｇｆ／ｃｍ２の荷重（面圧）を累積負荷した。
相手材 ：機械構造用炭素鋼（Ｓ４５Ｃ）
試験方法 ：スラスト試験で行い、摩擦係数が０．３に達した時点で試験を中止した。
潤滑方法 ：試験開始時に摺動面にグリースを塗布した。
【００５９】
この耐荷重試験の結果を図１に示す。図１は、累積荷重（面圧）と摩擦係数の推移を示したグラフであり、縦軸は摩擦係数を表し、横軸は累積荷重（面圧）を表す。
【００６０】
図１に示すように、比較例１の摺動部材では、試験開始から比較的安定した摩擦係数で推移したが、累積荷重が９０ｋｇｆ／ｃｍ２を超えると摩擦係数が徐々に上昇し、累積荷重１８０ｋｇｆ／ｃｍ２で摩擦係数が０．３に達したので試験を中止した。比較例１の焼結摺動部材が累積荷重１８０ｋｇｆ／ｃｍ２で異常摩耗に移行した理由は、この焼結摺動部材に含有されている潤滑油が枯渇したからである、と推察される。
【００６１】
また、比較例２の焼結摺動部材は、試験開始から徐々に摩擦係数が低下し、累積荷重が２１０ｋｇｆ／ｃｍ２を超えるあたりから摩擦係数が徐々に上昇し始め、累積荷重が３３０ｋｇｆ／ｃｍ２で摩擦係数が０．３に達したので試験を中止した。この比較例２の焼結摺動部材について、試験後、相手材の表面を観察したところ、この焼結摺動部材に含有されている遊離黒鉛の潤滑被膜が相手材の表面に形成されていることが確認された。比較例２の焼結摺動部材が比較例１の焼結摺動部材よりも耐荷重性に優れている理由は、比較例２の焼結摺動部材に含有されている遊離黒鉛は、比較例１の焼結摺動部材のそれよりも多く、この遊離黒鉛の潤滑作用と焼結摺動部材に含有された潤滑油の潤滑作用とが相俟って発揮されたからである、と推察される。
【００６２】
一方、実施例１及び実施例２の焼結摺動部材は、試験開始から累積荷重が４８０ｋｇｆ／ｃｍ２まで摩擦係数が０．１５以下と安定した値を示した。この耐荷重試験の結果から、実施例１及び実施例２の焼結摺動部材は比較例２の焼結摺動部材の１．６倍の耐荷重性能を有するものであることがわかる。
【００６３】
つぎに、上記した耐荷重試験の結果を踏まえ、実施例１、実施例２、及び比較例２の焼結摺動部材について下記に示す試験条件により耐久試験を行い、耐摩耗性を比較した。試験結果を表４に示す。
【００６４】
〔耐久試験〕
【００６５】
＜試験条件１＞
すべり速度 ：５ｍ／ｍｉｎ
荷重（面圧）：１００ｋｇｆ／ｃｍ２
試験時間 ：１０ｈｒ
相手材 ：機械構造用炭素鋼（Ｓ４５Ｃ）
試験方法 ：スラスト試験
潤滑方法 ：試験開始時に摺動面にグリースを塗布した。
【００６６】
＜試験条件２＞
すべり速度 ：３ｍ／ｍｉｎ
荷重（面圧）：２５０ｋｇｆ／ｃｍ２
試験時間 ：１０ｈｒ
相手材 ：機械構造用炭素鋼（Ｓ４５Ｃ）
試験方法 ：スラスト試験
潤滑方法 ：試験開始時に摺動面にグリースを塗布した。
【表４】
表４における実施例１、実施例２及び比較例２の摺動部材の摩耗量とは、各実施例及び比較例の焼結摺動部材の厚さ５ｍｍが耐久試験によって減少したときの減少量をいう。相手材の摩耗量も同様である。
【００６８】
耐久試験条件１においては、実施例１、実施例２及び比較例２の焼結摺動部材の摩耗量は極めて少なく、特に実施例１及び実施例２双方の焼結摺動部材の摩耗量は零であった。一方、耐久試験条件２においては、実施例１及び実施例２双方の焼結摺動部材の摩耗量は極めて少なかった。これに対し、比較例２の焼結摺動部材は試験開始後３０分で異常摩耗を起こしたので摩耗量の測定はできず、表４にはその摩耗量が記載されていない。
【００６９】
以上の耐荷重試験及び耐久試験の結果から、実施例１及び実施例２の焼結摺動部材では、その摺動表面に、四三酸化鉄の硬質の被膜と、遊離黒鉛と、多孔部及び遊離黒鉛に含有された潤滑油とが存在し、且つ、潤滑油剤（グリース）が介在しているので、相手材との摺動の際に低い摩擦係数で安定して摺動して摩耗量も極めて少ない、ことが判明した。従って、実施例１及び実施例２の焼結摺動部材は、その使用条件によっては従来技術及び先行技術の使用条件を大幅に上回り、使用範囲が大幅に拡大されることとなる。
【００７０】
【発明の効果】
以上説明したように本発明の鋳鉄系焼結摺動部材は、成長ねずみ鋳鉄鋳物を切削することによって生じる切粉を焼結してなる焼結合金母材の少なくとも摺動表面に四三酸化鉄の被膜が形成されているものであり、少なくとも摺動表面には、四三酸化鉄の硬質な被膜と、遊離黒鉛と、多孔部及び遊離黒鉛に含有された潤滑油とが存在するので、相手材との摺動において摩擦摩耗特性を大幅に向上させられる。
【００７１】
また、本発明の鋳鉄系焼結摺動部材の製造方法では、成長ねずみ鋳鉄鋳物を切削することによって得られる切粉を焼結して焼結合金母材を形成し、その後、該焼結合金母材に水蒸気処理を施して焼結合金母材の表面に四三酸化鉄の被膜を形成するので、摩擦摩耗特性に優れた鋳鉄系焼結摺動部材を製造できる。
【図面の簡単な説明】
【図１】実施例と比較例の耐荷重試験の結果を比較して示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cast iron-based sintered sliding member using chips obtained by cutting a gray cast iron casting and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, gray cast iron in which carbon is present in the form of flake graphite is known. Castings (greycast iron castings) made from this gray cast iron are widely used as materials for internal combustion engines because of their large vibration absorption capability and high thermal conductivity. Also, gray cast iron has excellent castability, and is therefore widely used as an industrial machine tool material with many complicated shapes such as fluid machines and valves. Furthermore, this cast iron is made to grow by heating the cast iron casting for a long time or by repeated heating and cooling, and the porous part (porous part) generated by this growth is impregnated with lubricating oil, so that it has excellent slidability. It is known that an oil-containing sliding member can be obtained, and this oil-containing sliding member is widely used for sliding applications such as bearings and sliding plates.
[0003]
Gray cast iron castings used in the various applications described above become final products through mechanical processing such as roughing, thinning, finishing, and sometimes grinding. When these machining operations are performed on gray cast iron castings, cast iron chips are produced in each processing step. Most of the chips produced in this way are usually disposed of.
[0004]
Focusing on the scraps of gray cast iron castings to be disposed of, as a technique that actively uses the chips, for example, a technique disclosed in Japanese Patent Publication No. 58-21002 is known. In this technology, a gray cast iron powder (chip) is molded at a molding pressure of 4 ton / cm 2 or more to obtain a molded product, and then ammonia decomposition gas that is a weak decarbonizing atmosphere or a neutral atmosphere with respect to the cast iron. This is a technique for producing a sintered compact having a tensile strength of 10 kg / mm 2 or more by sintering the above molded product at a temperature of at least 1010 ° C. in an atmosphere or a dry hydrogen atmosphere.
[0005]
In addition, as a technique for manufacturing a sintered compact for sliding use such as a bearing using the above-described chips, for example, a technique disclosed in Japanese Patent Publication No. 58-12321 is known. This technique produces gray cast iron powder by pulverizing chips obtained by cutting or grinding a cast product. The gray cast iron powder is 90 wt% to 99.5 wt% and the carbon powder is 0.5 wt% to This is a technique for producing a sintered compact after mixing 10% by weight to prepare a mixed powder and compression molding the mixed powder.
[0006]
As described above, according to the technique disclosed in Japanese Patent Publication No. 58-21002, a sintered compact having a tensile strength of 10 kg / mm 2 or more is manufactured. The sintered compact can be effectively used as a machine part. However, since this sintered compact has a small content of free graphite that contributes to lubricity, this sintered compact has poor sliding properties such as friction and wear. Therefore, there is a problem that when the sintered compact is used as a sliding part such as a bearing, the lubrication conditions and the use conditions must be carefully taken into account.
[0007]
Moreover, in the technique disclosed in Japanese Patent Publication No. 58-12321, carbon powder is contained for the purpose of imparting lubricity to the sintered compact. However, this carbon powder becomes a cause of inhibiting the sinterability, and as a result, there is a drawback that the strength of the sintered compact is weak. There is a problem that a sintered compact having such a defect is difficult to use as a sliding part.
[0008]
[Problems to be solved by the invention]
In order to solve the above-described problem, the applicant of the present application previously described a cast iron-based sintered sliding member excellent in sliding characteristics and a method for manufacturing the same in Japanese Patent Application No. 2001-6002 (hereinafter referred to as “prior art”). Proposed. The prior art cutting growth gray iron castings, the chips obtained by the cutting predetermined and loaded into the mold, of the loaded with chips 3 t / cm 2 or more 5 t / cm 2 or less A green compact is formed by compression molding at a molding pressure within a range, and the green compact is only in a neutral atmosphere or a reducing atmosphere at a temperature in the range of 1100 ° C. to 1150 ° C. for a period of 30 minutes to 90 minutes. Is a method for producing a cast iron-based sintered sliding member. The cast iron-based sintered sliding member obtained by this manufacturing method has excellent friction and wear characteristics because free graphite is dispersed and contained throughout, and can be applied to sliding parts such as bearings and sliding plates. .
[0009]
The present invention provides a cast iron-based sintered sliding member that effectively utilizes the above-described prior art, and further improves the frictional wear characteristics of the cast iron-based sintered sliding member obtained by the prior art, and a method for manufacturing the same. For the purpose.
[0010]
[Means for Solving the Problems]
The cast iron-based sintered sliding member of the present invention for achieving the above object is
(1) A sintered alloy formed by sintering chips produced by cutting a gray cast iron casting is used as a base material, and a coating of iron trioxide is formed on at least the sliding surface of the base material. It is characterized by.
[0011]
here,
(2) The coating of iron trioxide may have a thickness in the range of 2 μm to 5 μm.
[0012]
further,
(3) The coating of triiron tetroxide may have a Vickers hardness (HmV) in the range of 440 to 560.
[0013]
Furthermore, the cast iron-based sintered sliding member is
(4) Lubricating oil in the range of 7% by volume to 15% by volume of the total volume may be contained.
[0014]
Moreover, the manufacturing method of the cast iron-type sintered sliding member of the present invention for achieving the above object is (5) cutting a gray cast iron casting,
(6) The chips obtained by this cutting are loaded into a predetermined mold,
(7) The loaded chips are compression molded at a molding pressure within a range of 3 ton / cm 2 to 5 ton / cm 2 to form a green compact,
(8) Sintering the green compact for 30 minutes to 90 minutes at a temperature in the range of 1100 ° C. to 1150 ° C. in a neutral or reducing atmosphere to produce a sintered alloy base material ,
(9) A cast iron-based sintered sliding member is produced by subjecting this sintered alloy base material to steam treatment to form a coating of iron trioxide at least on the sliding surface.
[0015]
here,
(10) in obtaining the growth gray iron castings, the repetition heating and cooling process of repeating the heating and cooling with the temperature lower than the high temperature and the A 1 transformation point than the A 1 transformation point of the gray iron castings gray iron castings You may obtain the said growth gray cast iron casting by giving.
[0016]
further,
(11) In loading the chips into a predetermined mold, the chips that pass through a 20-mesh sieve but do not pass through a 55-mesh sieve are within a range of 85 wt% to 97 wt% of the total weight. In addition to loading into the mold, chips passing through a 55 mesh screen may be loaded into the mold within a range of 3 wt% to 15 wt% of the total weight.
[0017]
Furthermore,
(12) When the chips that pass through a 20-mesh sieve but do not pass through the 55-mesh sieve are loaded into the mold, the total weight of the chips is within the range of 10% to 90% by weight. A chip that passes through a 20-mesh sieve but does not pass through a 36-mesh sieve, and passes through a 36-mesh sieve but within a range of 10% to 90% by weight but passes through a 55-mesh sieve. You may mix with the chip which does not carry and load in the said metal mold | die.
[0018]
Furthermore,
(13) The steam treatment may be performed at a treatment temperature within a range of 450 ° C. or more and 550 ° C. or less and within a time period of 60 minutes or more and 90 minutes or less.
[0019]
Furthermore,
(14) In performing the oil impregnation treatment on the cast iron-based sintered sliding member, the cast iron is adjusted so that the oil content is in the range of 7% by volume to 15% by volume of the total volume of the cast iron-based sintered sliding member. An oil impregnation treatment may be applied to the system sintered sliding member.
[0020]
The above-described coating of triiron tetroxide will be described.
[0021]
From the viewpoint of the sintered sliding member, the coating film of iron trioxide may be formed at least on the sliding surface of the sintered sliding member. However, when considering the anti-corrosive action due to triiron tetroxide, it is preferable to form a triiron tetroxide film on the entire surface of the sliding member. Corrosion resistance and rust resistance can be imparted to the sliding member.
[0022]
Also, when the thickness of the triiron tetroxide coating is less than 2 μm, it is difficult to recognize the effect of improving the sliding characteristics, particularly the wear resistance. On the other hand, if the thickness of the coating exceeds 5 μm, the ratio of sealing the porous portion of the sintered alloy base material increases, which may reduce the oil content of the lubricating oil impregnated in the sintered alloy base material. There is. From such a viewpoint, it is preferable that the coating of iron trioxide has a thickness in the range of 2 μm to 5 μm.
[0023]
By the way, as a technique for increasing the hardness of the sintered alloy base material to improve the wear resistance, for example, a technique for quenching the sintered alloy base material to increase the surface hardness is known. However, since this technique quenches at a high temperature of 800 ° C. or higher, it brings about a great change in the structure of the sintered alloy base material. On the other hand, since the steam treatment is performed in the range of 450 to 550 ° C., the hardness of the sintered alloy base material can be obtained without affecting the structure of the sintered alloy base material. When the surface hardness of the iron tetroxide film is less than 440 Vickers hardness (HmV), it is difficult to improve the wear resistance, while the surface hardness of the iron tetroxide film is Vickers hardness. If it exceeds 560, the mating material surface may be damaged. From such a viewpoint, it is preferable that the surface hardness of the iron tetroxide film is in the range of Vickers hardness of 450 or more and 560 or less.
[0024]
In addition, when the lubricating oil is contained, a known heat impregnation method or vacuum impregnation method is used. As the lubricating oil, mineral oil such as engine oil or machine oil is used.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
<Preparation of sintered alloy base material>
[0026]
Carbon (C) 2.5 to 4.0 wt% (representing 2.5 wt% to 4.0 wt%, the same applies hereinafter), silicon (Si) 0.5 to 3.5 wt% Manganese (Mn) 0.2-1.0 wt%, phosphorus (P) 0.03-0.8 wt%, sulfur (S) 0.01-0.12 wt%, balance iron (Fe) the gray iron castings, subjected to repetition heating and cooling process of repeating the heating and cooling with the temperature lower than the high temperature and the a 1 transformation point than the a 1 transformation point of the gray iron casting (723 ° C.), pieces of in the matrix A gray cast iron casting obtained by enlarging glassy graphite is obtained. The growing gray cast iron casting preferably has an all-ferrite structure. Here, the base is an all-ferrite structure, which means that the base is composed only of a ferrite structure, but a base having a small amount of other structures such as a pearlite structure in addition to the ferrite structure is also included in the all-ferrite structure here. .
[0027]
The grown gray cast iron casting is subjected to roughing, thinning and finishing cutting to obtain chips of the grown gray cast iron. The chip base obtained in this way contains a large amount of flake graphite enlarged by growth, and a large proportion of the flake graphite is exposed on the surface. This ratio is larger than the ratio of flake graphite exposed on the surface of chips obtained by cutting a general gray cast iron casting.
[0028]
Next, the chips obtained in each step of the cutting process are divided into chips having a particle size that passes through a 20-mesh sieve but does not pass through a 55-mesh sieve, and particles having a particle size that passes through a 55-mesh sieve. Sort out. Furthermore, a particle having a particle size that passes through a 20-mesh sieve but does not pass through a 55-mesh sieve, and a particle having a particle size that passes through a 20-mesh sieve but does not pass through a 36-mesh sieve are passed through the 36 mesh. Sort into chips of particle size that do not pass through a 55 mesh sieve.
[0029]
Of the chips selected as described above, chips having a particle size that passes through a 20-mesh sieve but does not pass through a 55-mesh sieve mainly form a skeleton of a sintered alloy base material. In addition, the amount of graphite occupying in the chips is large in the chips having a particle size passing through a 55 mesh sieve. Therefore, by containing the chips passing through the 55 mesh sieve dispersed throughout the sintered alloy base material, this sintered alloy base material can be used without containing a lubricating component such as graphite separately. Exhibits lubrication.
[0030]
Of the selected particles of each particle size, 85 to 97% by weight of particles having a particle size that passes through a 20-mesh sieve but does not pass through a 55-mesh sieve, and 3 to 15 particles having a particle size that passes through a 55-mesh sieve. A mixed powder is prepared by mixing with wt%. Here, 10 to 90% by weight of a fine particle having a particle size passing through a 20 mesh sieve but not passing through a 55 mesh sieve but passing through a 20 mesh sieve but not passing through a 36 mesh sieve , And a particle size 3 to pass through a 55 mesh sieve, compared to 85 to 97% by weight of a powder mixed with 10 to 90% by weight of a particle size that passes through a 36 mesh but does not pass through a 55 mesh screen. It is made to be a mixed powder in which 15% by weight is mixed. In addition, the weight% of each chip | tip is a ratio with respect to the total weight of the produced mixed powder.
[0031]
The mixed powder thus obtained is loaded into a mold and compression molded at a molding pressure within a range of 3 ton / cm 2 to 5 ton / cm 2 to produce a green compact. The green compact is sintered in a neutral atmosphere or a reducing atmosphere at a temperature in the range of 1100 ° C. to 1150 ° C. for a time in the range of 30 minutes to 90 minutes to produce a sintered alloy base material. .
[0032]
<Manufacture of cast iron-based sintered sliding members>
[0033]
The sintered alloy base material obtained as described above is placed in a heating furnace, the temperature in the heating furnace is raised to a range of 450 ° C. or more and 550 ° C. or less, and this temperature is maintained in the heating furnace. Then, water vapor is continuously sprayed within a period of 60 minutes to 90 minutes to subject the sintered alloy base material to water vapor treatment. By this steam treatment, a coating film of iron trioxide having a thickness in the range of 2 μm to 5 μm and a Vickers hardness in the range of 440 to 560 is formed on the sliding surface of the sintered alloy base material. . In performing the steam treatment, the treatment temperature and treatment time depend on the skill of the iron trioxide film formed on the sliding surface of the sintered alloy base material (whether the film has a uniform thickness), firing. This is an important factor because it affects the decarburization of free carbon (graphite) contained in the bonded gold base material and the sealing of the porous portion. In this manner, a cast iron-based sintered sliding member having at least a sliding iron tetraoxide coating formed on the sliding surface is manufactured.
[0034]
By subjecting the cast iron-based sintered sliding member to oil impregnation treatment, a cast iron-based oil impregnated sintered sliding member having an oil content of 7% by volume to 15% by volume is obtained. Therefore, the cast iron oil-containing sintered sliding member contains the lubricating oil in the range of 7% by volume to 15% by volume.
[0035]
In this cast iron-based sintered sliding member, at least the sliding surface has a hard coating of iron trioxide, free graphite, and the lubricating oil contained in the porous portion and free graphite. In comparison with the cast iron-based sintered sliding member proposed in the prior art, the friction and wear characteristics can be greatly improved.
[0036]
【Example】
Examples of the present invention will be described in detail below. The present invention is not limited to these examples.
[0037]
[Example 1]
[0038]
3.65 wt% carbon (C), 2.22 wt% silicon (Si), 0.45 wt% manganese (Mn), 0.045 wt% phosphorus (P), 0.084 wt% A cylindrical gray cast iron casting (FC150) having a composition composed of sulfur (S) and the balance iron (Fe) and having an inner diameter of 33 mm, an outer diameter of 54 mm, and a length of 203 mm was produced. This Rat A 1 transformation point of iron casting (723 ° C.) (across by up and down the A 1 transformation point) repeating heating and cooling between higher temperatures and lower temperatures than the repetitive heating and cooling processes, gray cast iron material mixture The flake graphite was enlarged and the periphery of the flake graphite was made porous along with this growth. A grown gray cast iron casting was thus obtained.
[0039]
The oxidized scale produced on the surface of the above-mentioned grown gray cast iron casting is removed, and then the grown gray cast iron casting is subjected to roughing, thinning and finishing cutting, and the bearing has an inner diameter of 40 mm, an outer diameter of 50 mm and a length of 40 mm. A bush was made. In this way, a large amount of swarf was generated when the bearing gray was produced by cutting the gray cast iron casting. These large amounts of chips were sorted into chips that passed through a 20 mesh screen but not through a 55 mesh screen, and chips that passed through a 55 mesh screen.
[0040]
Furthermore, the chips that pass through the 20 mesh sieve but do not pass through the 55 mesh sieve, the chips that pass through the 20 mesh sieve but not through the 36 mesh sieve, and pass through the 36 mesh sieve but 55 mesh. Were sorted into chips that did not pass through the sieve.
[0041]
Of the swarf of each particle size selected as described above, the swarf that passes through a 20-mesh sieve but does not pass through the 36-mesh sieve passes 56% by weight of the total weight and passes through the 36-mesh sieve, but 55 mesh. 36 wt% of the total weight of the chips not passing through the sieve and 8 wt% of the total weight of the chips passing through the 55 mesh sieve were weighed. The composition of each chip is shown in Table 1.
[Table 1]
In Table 1, −20 mesh indicates passing through a 20 mesh screen, and +55 mesh indicates not passing through a 55 mesh screen. The same applies to the following tables.
[0043]
Each of the chips selected and weighed as described above was mixed to prepare a mixed powder. Next, this mixed powder was loaded into a mold having a rectangular parallelepiped hollow portion and compression molded at a molding pressure of 4 ton / cm 2 to produce a green compact. Thereafter, the green compact is sintered at a temperature of 1130 ° C. for 60 minutes in a heating furnace adjusted to a hydrogen gas atmosphere (which is an example of a neutral atmosphere or a reducing atmosphere according to the present invention), and is sintered in a rectangular parallelepiped shape. Got the body. The sintered body thus obtained was cut to produce a sintered alloy base material having a square cross section with a side of 30 mm and a thickness of 5 mm.
[0044]
Next, after placing the sintered alloy base material in a heating furnace and raising the temperature in the heating furnace to 480 ° C., steam is continuously injected into the heating furnace for 90 minutes while maintaining this temperature, The bonded gold base material was subjected to steam treatment. By this steam treatment, a cast iron-based sintered sliding member having a 3 μm thick iron trioxide coating formed on the surface of the sintered alloy base material was obtained. The coating of triiron tetroxide had a Vickers hardness (HV) of 442. In addition, when the cast iron-based sintered sliding member was subjected to oil impregnation treatment, the oil content of the lubricating oil was 10.3% by volume.
[0045]
[Example 2]
[0046]
In the same manner as in Example 1 described above, the chips generated when cutting a gray cast iron casting to produce a bearing bush are cut through a 20 mesh screen but not through a 55 mesh screen. , And the chips passing through a 55 mesh sieve.
[0047]
Furthermore, the chips that pass through the 20 mesh sieve but do not pass through the 55 mesh sieve, the chips that pass through the 20 mesh sieve but not through the 36 mesh sieve, and pass through the 36 mesh sieve but 55 mesh. Were sorted into chips that did not pass through the sieve. Of the swarf of each particle size thus selected, the swarf that passes through a 20 mesh screen but does not pass through a 36 mesh screen passes through 30% by weight of the total weight and passes through a 36 mesh screen, but 55 mesh. The chips that did not pass through the sieve were weighed 60% by weight of the total weight, and the chips that passed through the 55 mesh sieve were weighed 10% by weight of the total weight. The composition of each chip is shown in Table 2.
[Table 2]
Each of the chips selected and weighed as described above was mixed to form a mixed powder. Next, this mixed powder was loaded into a mold having a rectangular parallelepiped hollow portion and compression molded at a molding pressure of 4 ton / cm 2 to produce a green compact. Thereafter, in the same manner as in Example 1, in a heating furnace adjusted to a hydrogen gas atmosphere, the green compact was sintered at a temperature of 1130 ° C. for 60 minutes to obtain a rectangular parallelepiped sintered body. The sintered body thus obtained was cut to produce a sintered alloy base material having a square cross section with a side of 30 mm and a thickness of 5 mm.
[0049]
Next, after placing the sintered alloy base material in a heating furnace and raising the temperature in the heating furnace to 550 ° C., steam is continuously injected into the heating furnace for 60 minutes while maintaining this temperature, The bonded gold base material was subjected to steam treatment. By this steam treatment, a cast iron-based sintered sliding member having a 5 μm-thick iron trioxide coating formed on the surface of the sintered alloy base material was obtained. The coating of triiron tetroxide had a Vickers hardness (HmV) of 503. In addition, when the cast iron-based sintered sliding member was subjected to oil impregnation treatment, the oil content of the lubricating oil was 9.6% by volume.
[0050]
[Comparative Example 1]
[0051]
3.65% by weight C, 2.22% by weight Si, 0.45% by weight Mn, 0.045% by weight P, 0.084% by weight S, balance Fe, inner diameter 33 mm, outer diameter A cylindrical gray cast iron casting (FC150) having a length of 54 mm and a length of 203 mm was produced. The gray cast iron casting was subjected to roughing, thinning, and finishing cuttings to produce a bearing bush having an inner diameter of 40 mm, an outer diameter of 50 mm, and a length of 40 mm. When a gray cast iron casting was cut in this way to produce a bearing bush, a large amount of chips were generated. These large amounts of chips were sorted into fine particles having a particle size that passed through a 20 mesh screen but not through a 55 mesh screen, and fine particles that passed through a 55 mesh screen.
[0052]
Furthermore, a particle having a particle size that passes through a 20-mesh sieve but does not pass through a 55-mesh sieve, and a particle having a particle size that passes through a 20-mesh sieve but does not pass through a 36-mesh sieve are passed through a 36-mesh sieve. However, it was sorted into chips having a particle size that did not pass through a 55 mesh sieve.
[0053]
Of the swarf of each particle size selected as described above, the swarf having a particle size that passes through a 20 mesh sieve but does not pass through a 36 mesh sieve passes through a 36 mesh sieve, 56% by weight of the total weight. 36% by weight of the total particle weight of the chips not passing through the 55 mesh sieve and 8% by weight of the total particle weight of the particles passing through the 55 mesh sieve were weighed. The composition of each chip is shown in Table 3.
[Table 3]
Each of the chips selected and weighed as described above was mixed to form a mixed powder. Next, this mixed powder was loaded into a mold having a rectangular parallelepiped hollow portion and compression molded at a molding pressure of 4 ton / cm 2 to produce a green compact. Thereafter, this green compact was sintered at a temperature of 1130 ° C. for 60 minutes in a heating furnace to obtain a sintered body. The sintered body was cut to produce a sintered sliding member having a square cross section with a side of 30 mm and a thickness of 5 mm. When this cast iron-based sintered sliding member was subjected to oil impregnation treatment, the oil content of the lubricating oil was 12.3% by volume.
[0055]
[Comparative Example 2]
[0056]
A sintered alloy base material having the same component composition as in Example 1 and using a chip having the same particle size distribution and sintered under the same conditions and having a square cross section with a side of 30 mm and a thickness of 5 mm. A sintered sliding member was obtained. When this cast iron-based sintered sliding member was subjected to oil impregnation treatment, the oil content of the lubricating oil was 12.2% by volume. The sintered sliding member of Comparative Example 2 corresponds to the above-described prior art sintered sliding member.
[0057]
Next, with respect to the sintered sliding members obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 described above, a load resistance test was performed under the test conditions shown below.
[0058]
(Load test)
Test condition sliding speed: 3m / min
Load (surface pressure): A load (surface pressure) of 30 kgf / cm 2 was accumulated every 10 minutes.
Mating material: Carbon steel for machine structure (S45C)
Test method: A thrust test was performed, and the test was stopped when the friction coefficient reached 0.3.
Lubrication method: Grease was applied to the sliding surface at the start of the test.
[0059]
The results of this load resistance test are shown in FIG. FIG. 1 is a graph showing the transition of the cumulative load (surface pressure) and the friction coefficient, where the vertical axis represents the friction coefficient and the horizontal axis represents the cumulative load (surface pressure).
[0060]
As shown in FIG. 1, the sliding member of Comparative Example 1 transitioned with a relatively stable friction coefficient from the start of the test. However, when the cumulative load exceeded 90 kgf / cm 2 , the friction coefficient gradually increased and the cumulative load increased. Since the friction coefficient reached 0.3 at 180 kgf / cm 2 , the test was stopped. The reason why the sintered sliding member of Comparative Example 1 shifted to abnormal wear at a cumulative load of 180 kgf / cm 2 is presumed to be that the lubricating oil contained in the sintered sliding member was depleted.
[0061]
Further, the sintered sliding member of Comparative Example 2 has a friction coefficient that gradually decreases from the start of the test, and the friction coefficient starts to gradually increase when the cumulative load exceeds 210 kgf / cm 2 , and the cumulative load is 330 kgf / cm. Since the coefficient of friction reached 0.3 at 2 , the test was stopped. Regarding the sintered sliding member of Comparative Example 2, when the surface of the counterpart material was observed after the test, a free graphite lubricating film contained in the sintered slide member was formed on the surface of the counterpart material. It was confirmed. The reason why the sintered sliding member of Comparative Example 2 has better load resistance than the sintered sliding member of Comparative Example 1 is that the free graphite contained in the sintered sliding member of Comparative Example 2 is More than that of the sintered sliding member of Example 1, it is surmised that the lubricating action of this free graphite and the lubricating action of the lubricating oil contained in the sintered sliding member were exerted together. The
[0062]
On the other hand, the sintered sliding member of Example 1 and Example 2 showed a stable value with a friction coefficient of 0.15 or less from the start of the test until the cumulative load was 480 kgf / cm 2 . From the results of the load bearing test, it can be seen that the sintered sliding members of Example 1 and Example 2 have a load bearing performance 1.6 times that of the sintered sliding member of Comparative Example 2.
[0063]
Next, based on the results of the load resistance test described above, durability tests were performed on the sintered sliding members of Example 1, Example 2, and Comparative Example 2 under the test conditions shown below to compare the wear resistance. The test results are shown in Table 4.
[0064]
〔An endurance test〕
[0065]
<Test condition 1>
Sliding speed: 5m / min
Load (surface pressure): 100 kgf / cm 2
Test time: 10 hr
Mating material: Carbon steel for machine structure (S45C)
Test method: Thrust test lubrication method: Grease was applied to the sliding surface at the start of the test.
[0066]
<Test condition 2>
Sliding speed: 3m / min
Load (surface pressure): 250 kgf / cm 2
Test time: 10 hr
Mating material: Carbon steel for machine structure (S45C)
Test method: Thrust test lubrication method: Grease was applied to the sliding surface at the start of the test.
[Table 4]
The amount of wear of the sliding members of Example 1, Example 2 and Comparative Example 2 in Table 4 is the amount of reduction when the thickness 5 mm of the sintered sliding member of each Example and Comparative Example is reduced by the durability test. Say. The same applies to the wear amount of the mating material.
[0068]
In the durability test condition 1, the amount of wear of the sintered sliding members of Example 1, Example 2 and Comparative Example 2 is extremely small. In particular, the amount of wear of the sintered sliding members of both Example 1 and Example 2 is It was zero. On the other hand, in the durability test condition 2, the wear amount of the sintered sliding members of both Example 1 and Example 2 was extremely small. On the other hand, since the sintered sliding member of Comparative Example 2 was abnormally worn 30 minutes after the start of the test, the amount of wear could not be measured, and Table 4 does not describe the amount of wear.
[0069]
From the results of the above load bearing test and durability test, in the sintered sliding member of Example 1 and Example 2, the sliding surface has a hard coating of iron trioxide, free graphite, a porous portion, and Since there is a lubricating oil contained in free graphite and a lubricating oil (grease) is present, it slides stably with a low coefficient of friction when sliding against the mating material, and the amount of wear is also It turned out to be very few. Therefore, the sintered sliding member of Example 1 and Example 2 greatly exceeds the use conditions of the prior art and the prior art depending on the use conditions, and the use range is greatly expanded.
[0070]
【The invention's effect】
As described above, the cast iron-based sintered sliding member according to the present invention is made of iron trioxide on at least a sliding surface of a sintered alloy base material obtained by sintering chips generated by cutting a grown gray cast iron casting. Since at least the sliding surface has a hard coating of iron trioxide, free graphite, and the lubricating oil contained in the porous portion and free graphite, Friction and wear characteristics can be greatly improved in sliding with the material.
[0071]
In the method for producing a cast iron-based sintered sliding member of the present invention, a sintered alloy base material is formed by sintering chips obtained by cutting a grown gray cast iron casting, and then the sintered alloy. Since the base metal is steam-treated to form a coating of iron trioxide on the surface of the sintered alloy base material, a cast iron-based sintered sliding member having excellent friction and wear characteristics can be manufactured.
[Brief description of the drawings]
FIG. 1 is a graph showing a comparison of results of a load resistance test between an example and a comparative example.
Claims (9)
この切削によって得られた切粉を所定の金型内に装填し、
この装填した切粉を３トン／ｃｍ２以上５トン／ｃｍ２以下の範囲内の成形圧力で圧縮成形して圧粉体を形成し、
中性雰囲気または還元性雰囲気において１１００℃以上１１５０℃以下の範囲内の温度で３０分間以上９０分間以下の時間内だけ前記圧粉体を焼結して焼結合金母材を作製し、
この焼結合金母材に水蒸気処理を施して少なくとも摺動表面に四三酸化鉄の被膜を形成させることを特徴とする鋳鉄系焼結摺動部材の製造方法。Cutting the grown gray iron castings subjected to repetition heating and cooling process of repeating the heating and cooling between the temperature lower than the high temperature and the A 1 transformation point than the A 1 transformation point of the gray iron castings gray iron castings,
The chips obtained by this cutting are loaded into a predetermined mold,
The loaded chips are compression molded at a molding pressure within a range of 3 ton / cm 2 to 5 ton / cm 2 to form a green compact,
Sintering the green compact for 30 minutes to 90 minutes at a temperature in the range of 1100 ° C. to 1150 ° C. in a neutral or reducing atmosphere to produce a sintered alloy base material;
A method for producing a cast iron-based sintered sliding member, wherein the sintered alloy base material is subjected to steam treatment to form a coating of iron trioxide at least on a sliding surface.
２０メッシュの篩を通過するが５５メッシュの篩を通過しない切粉を総重量の８５重量％以上９７重量％以下の範囲内で前記金型内に装填すると共に、５５メッシュの篩を通過する切粉を総重量の３重量％以上１５重量％以下の範囲内で前記金型内に装填することを特徴とする請求項５に記載の鋳鉄系焼結摺動部材の製造方法。In loading the chips into a predetermined mold,
Chips that pass through a 20-mesh sieve but do not pass through a 55-mesh sieve are loaded into the mold within a range of 85% by weight to 97% by weight of the total weight, and the chips that pass through the 55-mesh sieve 6. The method for producing a cast iron-based sintered sliding member according to claim 5, wherein powder is loaded into the mold within a range of 3 wt% to 15 wt% of the total weight.
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