JP2004323939A

JP2004323939A - Method for manufacturing sintered part

Info

Publication number: JP2004323939A
Application number: JP2003122546A
Authority: JP
Inventors: Yoshitsugu Tsuchiya; 嘉嗣土屋
Original assignee: Sumitomo Electric Sintered Alloy Ltd
Current assignee: Sumitomo Electric Sintered Alloy Ltd
Priority date: 2003-04-25
Filing date: 2003-04-25
Publication date: 2004-11-18

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which sintered parts obtained by subjecting a powder material to die compaction and then to machining can be manufactured while combining securement of high strength with that of high shape accuracy. <P>SOLUTION: The sintered parts can be manufactured by the following steps I to IV: a step I of preparing a powder mixture 1 obtained by mixing, by mass, any of (1) ≥70% reduced iron powder and ≤29% additive metal powder, (2) ≥70% water atomized powder of Fe and ≤29% additive metal powder and (3) ≥80% water atomized powder of Fe alloy and ≤19% additive metal powder, 0.4 to 1.0% carbon powder and ≤0.1% lubricant; a step II of subjecting the powder mixture to compaction using die wall lubrication; a step III of cutting or grinding the resultant green compact obtained in the step II; and a step IV of sintering the cut or ground green compact. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、機械加工を必要とする焼結部品を高強度と良好な形状精度を確保して作製することを可能ならしめる焼結部品の製造方法とその方法で得られる焼結部品に関する。
【０００２】
【従来の技術】
下記特許文献１は、形状が複雑などの理由により全体を金型成形するのが困難な部品を容易に作製することができる方法として、材料の金属粉末を金型成形が可能な範囲の形状で成形し、得られた成形体を機械加工した後に焼結する方法を開示している。
【０００３】
また、下記特許文献２は、金型潤滑成形法（金型に潤滑剤を付着させて成形を行う方法。以下ではこの方法によって得られる成形体を金型潤滑成形体と言う）で金属粉末を成形した後に、得られた成形体を焼結して高密度と高い面圧疲労強度を有する鉄基焼結体を得る方法を開示している。
【０００４】
【特許文献１】
特開昭５５−１２２８０４号公報
【特許文献２】
特開２００２−１５５３０３号公報
【０００５】
【発明が解決しようとする課題】
上記特許文献１が開示している方法は、複雑な部品を製造するのに適した方法である。何故なら、硬度が高まった焼結体を機械加工するのは困難であるが、焼結前の成形体は簡単に機械加工することができ、これにより金型成形が困難な部位を有する複雑な焼結部品であっても容易に作製することが可能になる。ところが、この方法では、金型に対する成形体の焼き付きを防止するために材料の金属粉末に潤滑剤を添加しているので、高強度部品を得るのが難しい。成形体の内部に取り込まれた潤滑剤が焼結部品の密度を低下させ、部品強度が犠牲になる。
【０００６】
一方、特許文献２の方法は、金型を潤滑するので材料の金属粉末に添加する潤滑剤の量が微量でよく、焼結体の密度を高めて高強度を得ることができる。また、金型の寿命が長く、部品の脱潤滑剤の工程も短縮できる利点がある。
【０００７】
しかしながら、金型潤滑成形体を焼結前に機械加工すると、成形体の一部が欠けるなどして良好な品質を維持できなくなることが多い。
【０００８】
ＰＯＷＤＥＲＭＩＸＥＳＷＩＴＨＨＩＧＨＧＲＥＥＮＳＴＲＥＮＧＴＨには、潤滑剤混合粉末の成形体の機械加工品の比較例（良くない例）として金型潤滑成形体の機械加工品のデータが示されており、これを見ると金型潤滑成形体は、潤滑剤添加金属粉を成形して機械加工する方法に比べて機械加工が難しいことが分かる。
【０００９】
以上要するに、特許文献１、２が示しているような従来の製造方法では、複雑な部品を焼結前に機械加工すると、得られる焼結部品の高強度と高品質を両立させるのが難しい。
【００１０】
そこで、この発明は、焼結前に粉末成形体を機械加工する手順を経て高強度と高品質を両立した焼結部品を作製できるようにすることを課題としている。
【００１１】
【課題を解決するための手段】
上記の課題を解決するため、この発明においては、１）還元鉄粉７０質量％以上、添加金属粉２９質量％以下、２）Ｆｅの水アトマイズ粉７０質量％以上、添加金属粉２９質量％以下、３）Ｆｅ合金の水アトマイズ粉８０質量％以上、添加金属粉１９質量％以下、
上記１）〜３）のいずれかと、カーボン粉：０．４〜１．０質量％と、潤滑剤：０．１質量％以下とを混合した粉末を準備する工程、
その混合粉を金型潤滑成形する工程、
金型潤滑成形して得られた成形体を切削または研削する工程、
切削または研削した成形体を焼結する工程を含む焼結体の製造方法を提供する。
なお、ここで云うＦｅ合金とは、合金成分として、Ｎｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎのうち少なくとも一種以上を含む金属を指す。
【００１２】
この方法における混合粉の金型潤滑成形は、混合粉及び金型の温度が１００℃以上、成形圧６００ＭＰａ以上の条件下で行うのがよい。
【００１３】
また、還元鉄粉又はＦｅもしくはＦｅ合金の水アトマイズ粉は、沈降法（流体中での粉体粒子の沈降速度から粒子の大きさを求める方法）による平均粒径が６０〜１００μｍのもの、
カーボン粉は、粒径（ＪＩＳＺ８８０１のふるい法による粒径）２０μｍ以下の粒子がカーボン粉の総量の７０％以上を占めるものがよい。
【００１４】
添加金属粉がＮｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎの中から選ばれた少なくとも１種であり、この添加金属粉として粒径（上記のふるい法による粒径）４５μｍ以下の金属粒子が添加金属粉の総量の８０％以上を占めるものを用いるのも有効なことである。
【００１５】
このほか、焼結体は焼結後に熱処理（焼入れ）するが、その焼入れを、焼結工程における冷却過程での焼結部品の冷却速度を１℃／ｓｅｃ以上にして行うのも好ましい。このような工程を経て製造される焼結部品は、従来のように焼結体を切削、研削することが困難であるが、この発明の方法によれば容易に切削、研削を行え、金型成形が困難な部位を有する複雑な焼結部品であっても、従来より少ない工程で作製することができる。
【００１６】
なお、この発明においては、上記の方法で製造されて、焼結前に切削または研削された部位に焼結肌を残している焼結部品も併せて提供する。この焼結部品はＦｅの質量％が７０〜９９％であり、Ｃ及びＦｅ以外の金属成分が残部を占める組成になっているものが特に好ましい。
【００１７】
また、焼結前の切削または研削により、加工面の面粗さがＲｚ＝２．５以下になっているものが好ましい。加工面が焼結前に切削または研削された面であることは、加工面に粉末の脱落痕があることによって見分けることができる。
【００１８】
【作用】
Ｆｅの含有量が７０質量％以上又はＦｅ合金の含有量が８０質量％以上の混合粉を用いると、金型潤滑成形して得られる成形体の強度が高くなる。
【００１９】
カーボン粉は焼結後の焼結部品の硬度を高めるのに必要である。このカーボン粉は、少なすぎると部品の硬度が不足し、多すぎると部品が脆くなるので、添加量を０．４〜１．０質量％の範囲とする。カーボン粉は焼結部品の硬度を高めるほか、成形体を切削或いは研削加工するときの潤滑効果も発揮し、従って、小さな粒子が成形体の各部に広く分布していることが望ましく、具体的には２０μｍ以下の粒子が総量の７０％以上を占めるものを用いるのがよい。
【００２０】
また、添加金属粉は必須ではないが、成形体の強度をより高めるのに有効である。この添加金属粉は多すぎると逆効果になるので、その添加量を、還元鉄粉又はＦｅの水アトマイズ粉を用いる場合には２９質量％以下、Ｆｅ合金の水アトマイズ粉を用いる場合には１９質量％以下に制限する。
【００２１】
潤滑剤は、切削、研削加工中に潤滑効果を発揮する。また、粉末同士を結びつける働きをし、これも成形体の強度を高めるのに役立つ。Ｆｅ密度７．８６ｇ／ｃｍ^３に対し、潤滑剤密度１ｇ／ｃｍ^３であるので、潤滑剤の量が少なければ成形体の密度が高まり、これにより内部空孔が少なくなるため、粉末同士の接触面積が増大して成形体、およびそれを焼結して得られる部品の強度が向上する。
【００２２】
この強度向上に加え、内部空孔減少により成形体の切削形態は断続切削よりも連続切削に近い状態になるため、焼結する前の成形体を切削加工あるいは研削加工したときの成形体の欠けや加工面の荒れが少なくなる。
【００２３】
なお、金型潤滑成形は、混合粉及び金型の温度が１００℃以上、成形圧６００ＭＰａ以上の条件下で行うのがよい。温間金型潤滑成形を行うと粉末の塑性変形が容易になり、空孔が小さくなって成形体の密度、強度が冷間成形や金型を潤滑せずに温間成形を行う場合よりも高まる。成形体の密度は成形圧にも左右され、成形圧が高くなるほどその密度は高まる。
【００２４】
また、ＦｅまたはＦｅ合金として、粒径の大きい粉末（好ましくは平均粒径が６０〜１００μｍ）を用いると当該粉が全質量の７０％以上を占めるので、大きい金属粒子の割合が大きくなる。成形体強度として現われるのは、基本的に大きな粉末であるＦｅまたはＦｅ合金粉同士の絡みつきがメインであり、塑性変形の起点となる小さな粒子（カーボン、添加金属粉）が残りを占めることにより、材料の混合粉が塑性変形し易くなって粉末同士の絡みつきがよくなる。図２に、粉末粒子の粒度と見かけ密度・成形体強度の関係のイメージ図を示す。このように、粒径の大きな粉末粒子を多く使用すると成形体の強度がさらに高まり、切削加工、研削加工時の欠けや加工面の荒れがより少なくなる。
【００２５】
成形体の強度は、添加金属の無い混合粉を用いる場合よりも添加金属を僅かに加えた混合粉を用いる場合の方がより向上する。添加金属粉は、４５μｍ以下の粒径の粒子が８０％以上を占めるものがＦｅまたはＦｅ合金の粒子間に入り込み易く、これによって粉末の充填密度が高まり、ＦｅまたはＦｅ合金の粒子間に入り込んだ添加金属粉（Ｎｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎ）が塑性変形の起点になるため、粉末同士の絡みつきがより良くなって成形体の強度がさらに向上する。
【００２６】
このほか、焼結工程における冷却過程において、１℃／ｓｅｃ以上の冷却速度で焼結体を冷却すると、焼結工程と焼入れ工程を統合でき、製造の簡略化が図れる。
【００２７】
この発明の方法で作製される焼結部品は、焼結前に切削または研削された部位に焼結肌を残したものになる。部材を切削または研削加工するとその部材の加工面に粉末の脱落が生じるが、加工面の面粗度はＲｚ２．５以下となる。また、加工面に加工工具の送りマークが残るが、焼結によりその送りマークは変形してなだらかになり、そのため、機械加工した部位の焼結肌は、焼結体を機械加工して得られる肌面に対して機能的に遜色がない。
【００２８】
また、Ｒｚ＝２．５以下であれば、十分な仕上がり精度を保ったまま凸凹による表面積の増加の効果で焼結時に内部まで加熱され易くなり、焼結性が向上し、焼結工程の冷却過程での放熱量も増加するので、材料特性（硬度や強度）が改善される効果がある。
【００２９】
【発明の実施の形態】
この発明の実施形態を以下に述べる。図１に、この発明の製造方法の一例を示す。まず、工程Ｉにおいて所定の混合粉、即ち、還元鉄粉又はＦｅの水アトマイズ粉：７０質量％以上と、カーボン粉：０．４〜１．０質量％と、添加金属粉：２９質量％以下と、潤滑剤：０．１質量％以下とを混合するか、又はＦｅ合金の水アトマイズ粉：８０質量％以上、添加金属粉：１９質量％以下と、カーボン粉：０．４〜１．０質量％と、潤滑剤：０．１質量％以下とを混合した混合粉１を準備する。
【００３０】
次に、工程ＩＩにおいて準備した混合粉１を金型潤滑成形法で金型２による成形が可能な範囲の形状に成形し、さらに、得られた成形体３の一部を、工程ＩＩＩにおいて切削、或いは研削加工して所望の部品形状に仕上げる。
【００３１】
その後、機械加工を終えた成形体３を工程ＩＶにおいて焼結し、さらに、工程Ｖにおいて加熱、油焼入れを行って所望の焼結部品４を得る。
【００３２】
なお、焼結工程ＩＶの冷却過程において、加熱した部品を１℃／ｓｅｃ以上の速度で冷却（所謂シンターハードニング処理）すると、焼入れがなされ、後段の熱処理、油漬の工程が不要になる。
【００３３】
以下に、この発明の方法の実施例と比較例を挙げる。
【００３４】
表１に示す組成の混合粉Ｎｏ．１〜Ｎｏ．４（本発明用）と比較用混合粉Ｎｏ．５及びＮｏ．６を準備した。これ等の混合粉は、請求項３、４、５での規定条件を満たすものである。
【００３５】
そして、Ｎｏ．１〜Ｎｏ．４の混合粉を金型と共に１３０℃の温度に加温して金型潤滑法で温間成形した。金型にはエチレンビスアミド系潤滑剤を塗布したが、この潤滑剤は、高級脂肪酸系潤滑剤でもよい。また、潤滑剤の塗布は固体粉末を噴射して行ったが、液体分散などで行ってもよい。Ｎｏ．５の混合粉も、Ｎｏ．１〜Ｎｏ．４の混合粉と同様の条件で金型潤滑法で温間成形した。
【００３６】
一方、Ｎｏ．６の混合粉は、その混合粉と金型を共に１３０℃の温度に加温して金型無潤滑により温間成形した。
【００３７】
成形圧６００ＭＰａ、８００ＭＰａ、１０００ＭＰａの各条件で得られた成形体の密度、硬度、強度を表２に示す。
【００３８】
得られた成形体は外形φ３４ｍｍ、内径φ２０ｍｍ、高さ１０ｍｍの円筒形状である。
【００３９】
次に、それぞれの成形圧において得られた成形体の外周を切れ味の良いバイトを用いて下記の条件で旋削した。
【００４０】

切削加工後の成形体の仕上がり面粗さと欠け量を表３に示す。
【００４１】
また、切削加工後の成形体を、ベルト炉を用いて１１３０℃、２０分の条件で焼結し、その後、冷却速度１℃／ｓｅｃと０．５℃／ｓｅｃの２条件で冷却した。この焼結と冷却はともに、Ｎ_２／Ｈ_２＝９０／１０の混合ガス雰囲気下で行った。こうして得られた焼結部品の引っ張り強度と硬度を表４に示す。
【００４２】
【表１】

【００４３】
【表２】

【００４４】
【表３】

【００４５】
【表４】

【００４６】
表２からわかるように、この発明の方法によれば、密度、硬度、強度に優れた粉末成形体が得られる。
【００４７】
また、表３からわかるように、潤滑剤を０．１質量％以下にしたもの（粉種１〜４）の方が潤滑剤を０．１質量％以上含むもの（粉種５、６）に比べて切削加工による成形体の欠け量が小さく、仕上がり面粗さが向上する。また、上述した「ＰＯＷＤＥＲＭＩＸＥＳＷＩＴＨＨＩＧＨＧＲＥＥＮＳＴＲＥＮＧＴＨ」に示されているような従来の温間成形品（粉種５）よりも欠け量が小さく、仕上がり面粗さが向上する。
【００４８】
さらに、焼結工程での冷却過程における冷却速度を１℃／ｓｅｃ以上にして焼入れを行ったものは、引っ張り強度と硬度に優れる焼結部品が得られる。
【００４９】
【発明の効果】
以上述べたように、この発明の方法によれば、金型潤滑成形法によって切削または研削加工を高品位に行える成形体を得ることができ、形状が複雑等の理由により焼結前に機械加工を施す焼結部品を高強度と高品質を両立して作製することが可能になる。
【００５０】
なお、沈降法による平均粒径が６０〜１００μｍのＦｅやＦｅ合金粉を用いた混合粉、Ｎｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎの中から選ばれた少なくとも１種の金属を添加した混合粉、あるいは添加金属粉として粒径４５μｍ以下の金属粒子が添加金属粉の総量の８０％以上を占めるものを用いた混合粉を使用してこの発明の方法で製造される焼結部品は、強度及び機械加工面の品位がより高まる。
【００５１】
また、焼結工程の冷却過程における冷却速度を１℃／ｓｅｃ以上にして行う方法は、焼結と焼入れの工程を統合でき、生産性の面で有利になる。
【図面の簡単な説明】
【図１】この発明の方法の概要を示す工程図
【図２】粉末粒子の粒度と見かけ密度・成形体強度の関係のイメージ図
【符号の説明】
１混合粉
２金型
３成形体
４焼結部品[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a sintered part that can manufacture a sintered part requiring machining with high strength and good shape accuracy, and a sintered part obtained by the method.
[0002]
[Prior art]
Patent Literature 1 below discloses a method for easily manufacturing a part whose entire shape is difficult to mold due to a complicated shape or the like. It discloses a method of forming and then sintering the obtained molded body after machining.
[0003]
Patent Document 2 below discloses a method in which a metal powder is formed by a mold lubrication molding method (a method in which a lubricant is adhered to a mold and molding is performed; a molded body obtained by this method is hereinafter referred to as a mold lubricated molded body). It discloses a method for obtaining an iron-based sintered body having a high density and a high surface pressure fatigue strength by sintering the obtained formed body after forming.
[0004]
[Patent Document 1]
JP-A-55-122804 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-155303
[Problems to be solved by the invention]
The method disclosed in Patent Document 1 is a method suitable for manufacturing a complicated component. Because it is difficult to machine a sintered body with increased hardness, the molded body before sintering can be easily machined, which makes it difficult to mold Even a sintered part can be easily manufactured. However, in this method, it is difficult to obtain a high-strength part because a lubricant is added to the metal powder of the material in order to prevent seizure of the molded body on the mold. Lubricants incorporated into the compact reduce the density of the sintered part, sacrificing part strength.
[0006]
On the other hand, the method of Patent Document 2 lubricates the mold, so that the amount of the lubricant to be added to the metal powder of the material may be small, and the density of the sintered body can be increased to obtain high strength. In addition, there is an advantage that the life of the mold is long, and the process of delubricating parts can be shortened.
[0007]
However, if the lubricated mold is machined before sintering, it often becomes impossible to maintain good quality due to a lack of the molded body.
[0008]
POWDER MIXES WITH HIGH HIGH GREEN STRENGTH shows data on machined lubricated moldings as comparative examples (poor examples) of machined lubricated powder compacts. It can be seen that machining of the lubricated mold is more difficult than machining the lubricant-added metal powder and machining.
[0009]
In short, in the conventional manufacturing methods as shown in Patent Documents 1 and 2, if a complicated component is machined before sintering, it is difficult to achieve both high strength and high quality of the obtained sintered component.
[0010]
Accordingly, an object of the present invention is to make it possible to produce a sintered part having both high strength and high quality through a procedure of machining a powder compact before sintering.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, 1) 70% by mass or more of reduced iron powder and 29% by mass or less of added metal powder 2) 70% by mass or more of water atomized powder of Fe and 29% by mass or less of added metal powder 3) 80% by mass or more of water atomized powder of Fe alloy, 19% by mass or less of added metal powder,
A step of preparing a powder obtained by mixing any one of the above 1) to 3), carbon powder: 0.4 to 1.0% by mass, and lubricant: 0.1% by mass or less;
A step of lubricating the mixed powder in a mold,
A step of cutting or grinding a molded body obtained by mold lubrication molding,
Provided is a method for manufacturing a sintered body including a step of sintering a cut or ground molded body.
Here, the Fe alloy refers to a metal containing at least one of Ni, Cu, Mo, Cr, and Mn as an alloy component.
[0012]
The mold lubrication molding of the mixed powder in this method is preferably performed under conditions where the temperature of the mixed powder and the mold is 100 ° C. or more and the molding pressure is 600 MPa or more.
[0013]
Further, the reduced iron powder or the water atomized powder of Fe or Fe alloy has an average particle diameter of 60 to 100 μm by a sedimentation method (a method of obtaining a particle size from a sedimentation velocity of a powder particle in a fluid),
The carbon powder preferably has a particle size of 20 μm or less (particle size according to a sieving method of JISZ8801) occupying 70% or more of the total amount of the carbon powder.
[0014]
The additive metal powder is at least one selected from the group consisting of Ni, Cu, Mo, Cr, and Mn, and as the additive metal powder, metal particles having a particle size of 45 μm or less (particle size by the above-described sieving method) are used. It is also effective to use one that occupies 80% or more of the total amount.
[0015]
In addition, the sintered body is heat-treated (quenched) after sintering, and the quenching is preferably performed at a cooling rate of the sintered component of 1 ° C./sec or more in the cooling process in the sintering step. It is difficult to cut and grind the sintered body of the sintered component manufactured through such a process as in the past, but according to the method of the present invention, the cutting and grinding can be easily performed, Even a complex sintered part having a part that is difficult to mold can be manufactured with fewer steps than before.
[0016]
In the present invention, there is also provided a sintered part manufactured by the above-described method and having a sintered surface left in a portion cut or ground before sintering. It is particularly preferable that the sintered component has a composition in which the mass% of Fe is 70 to 99% and a metal component other than C and Fe accounts for the balance.
[0017]
Further, it is preferable that the surface roughness of the processed surface is reduced to Rz = 2.5 or less by cutting or grinding before sintering. The fact that the processed surface is a surface that has been cut or ground before sintering can be discriminated by the presence of powder falling marks on the processed surface.
[0018]
[Action]
When a mixed powder having an Fe content of 70% by mass or more or an Fe alloy content of 80% by mass or more is used, the strength of a molded product obtained by die lubrication molding is increased.
[0019]
Carbon powder is necessary to increase the hardness of the sintered component after sintering. If the amount of the carbon powder is too small, the hardness of the component is insufficient, and if it is too large, the component becomes brittle. Therefore, the amount of the carbon powder is set in the range of 0.4 to 1.0% by mass. Carbon powder not only increases the hardness of the sintered part, but also exerts a lubricating effect when cutting or grinding the compact, so that it is desirable that small particles are widely distributed in each part of the compact. It is preferable to use particles having a particle size of 20 μm or less occupying 70% or more of the total amount.
[0020]
Further, the added metal powder is not essential, but is effective for further increasing the strength of the molded body. If the amount of the added metal powder is too large, it has an adverse effect. Therefore, the added amount is 29% by mass or less when reduced iron powder or Fe water atomized powder is used, and 19% when Fe alloy water atomized powder is used. Limit to less than mass%.
[0021]
The lubricant exerts a lubricating effect during cutting and grinding. It also serves to bind the powders together, which also helps to increase the strength of the compact. To Fe Density 7.86 g / cm ^3, since it is the lubricant density of 1 g / cm ^3, the less the amount of the lubricant increased density of the molded body, thereby the internal pores is reduced, the contact of the powder particles The area is increased, and the strength of the molded body and the parts obtained by sintering the molded body are improved.
[0022]
In addition to this strength improvement, the cutting form of the molded body is closer to continuous cutting than intermittent cutting due to the reduction of internal voids, so chipping of the molded body before cutting or grinding before sintering And roughness of the machined surface are reduced.
[0023]
It is preferable that the mold lubrication molding is performed under the condition that the temperature of the mixed powder and the mold is 100 ° C. or more and the molding pressure is 600 MPa or more. When warm mold lubrication molding is performed, plastic deformation of the powder becomes easier, the pores become smaller, and the density and strength of the compact are lower than when cold molding or warm molding without lubricating the mold. Increase. The density of the compact also depends on the compacting pressure, and the higher the compacting pressure, the higher the density.
[0024]
When a powder having a large particle diameter (preferably having an average particle diameter of 60 to 100 μm) is used as Fe or an Fe alloy, the powder occupies 70% or more of the total mass, so that the ratio of the large metal particles increases. The main manifestation of the strength of the compact is that the entanglement of Fe or Fe alloy powder, which is basically a large powder, is mainly involved, and small particles (carbon, added metal powder) serving as a starting point of plastic deformation occupy the remainder. The mixed powder of the material is easily plastically deformed, and the entanglement between the powders is improved. FIG. 2 shows an image diagram of the relationship between the particle size of the powder particles and the apparent density / strength of the compact. As described above, when a large number of powder particles having a large particle diameter are used, the strength of the molded body is further increased, and chipping and roughening of the processed surface during cutting and grinding are further reduced.
[0025]
The strength of the molded body is more improved when a mixed powder containing a small amount of the added metal is used than when a mixed powder containing no added metal is used. As for the added metal powder, particles having a particle size of 45 μm or less occupying 80% or more easily enter between particles of Fe or Fe alloy, thereby increasing the packing density of the powder and entering between particles of Fe or Fe alloy. Since the added metal powder (Ni, Cu, Mo, Cr, Mn) is the starting point of the plastic deformation, the entanglement between the powders is further improved, and the strength of the compact is further improved.
[0026]
In addition, when the sintered body is cooled at a cooling rate of 1 ° C./sec or more in the cooling step in the sintering step, the sintering step and the quenching step can be integrated, and the production can be simplified.
[0027]
The sintered part produced by the method of the present invention has a sintered surface left in a portion cut or ground before sintering. When the member is cut or ground, powder falls off on the processed surface of the member, but the surface roughness of the processed surface is Rz 2.5 or less. In addition, although the feed mark of the processing tool remains on the processing surface, the feed mark is deformed and smoothed by sintering. Therefore, the sintered surface of the machined portion is obtained by machining the sintered body. Functionally comparable to the skin.
[0028]
When Rz is 2.5 or less, the inside is easily heated at the time of sintering by the effect of the increase in the surface area due to the unevenness while maintaining sufficient finishing accuracy, the sinterability is improved, and the cooling in the sintering process is improved. Since the amount of heat radiation in the process also increases, there is an effect that the material properties (hardness and strength) are improved.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below. FIG. 1 shows an example of the manufacturing method of the present invention. First, in Step I, a predetermined mixed powder, that is, a reduced iron powder or a water atomized powder of Fe: 70% by mass or more, a carbon powder: 0.4 to 1.0% by mass, and an added metal powder: 29% by mass or less And lubricant: 0.1% by mass or less, or water atomized powder of Fe alloy: 80% by mass or more, added metal powder: 19% by mass or less, and carbon powder: 0.4 to 1.0 A mixed powder 1 in which a mass% and a lubricant: 0.1 mass% or less are mixed is prepared.
[0030]
Next, the mixed powder 1 prepared in the step II is molded by a mold lubrication molding method into a shape within a range that can be molded by the mold 2, and a part of the obtained molded body 3 is cut in the step III. Or, it is finished by grinding to a desired part shape.
[0031]
Thereafter, the formed body 3 after the machining is sintered in step IV, and further heated and oil-quenched in step V to obtain a desired sintered part 4.
[0032]
In the cooling step of the sintering step IV, if the heated component is cooled at a rate of 1 ° C./sec or more (so-called sinter hardening treatment), quenching is performed, and the subsequent heat treatment and oil immersion steps become unnecessary.
[0033]
Hereinafter, examples and comparative examples of the method of the present invention will be described.
[0034]
Mixed powder No. having the composition shown in Table 1 1 to No. 4 (for the present invention) and Comparative Mixed Powder No. 4 5 and No. 5 6 was prepared. These mixed powders satisfy the conditions specified in claims 3, 4, and 5.
[0035]
And No. 1 to No. The mixed powder of No. 4 was heated together with the mold to a temperature of 130 ° C. and warm-molded by a mold lubrication method. The mold was coated with an ethylenebisamide-based lubricant, but this lubricant may be a higher fatty acid-based lubricant. Further, the application of the lubricant is performed by spraying solid powder, but may be performed by liquid dispersion or the like. No. No. 5 mixed powder also 1 to No. Under the same conditions as for the mixed powder of No. 4, warm molding was performed by a mold lubrication method.
[0036]
On the other hand, No. The mixed powder of No. 6 was formed by warming both the mixed powder and the mold to a temperature of 130 ° C. and without lubrication of the mold.
[0037]
Table 2 shows the density, hardness, and strength of the molded body obtained under the molding pressures of 600 MPa, 800 MPa, and 1000 MPa.
[0038]
The obtained molded body has a cylindrical shape with an outer diameter of 34 mm, an inner diameter of 20 mm, and a height of 10 mm.
[0039]
Next, the outer periphery of the molded body obtained at each molding pressure was turned using a sharp cutting tool under the following conditions.
[0040]

Table 3 shows the finished surface roughness and chipping amount of the molded body after the cutting.
[0041]
Further, the compact after cutting was sintered using a belt furnace at 1130 ° C. for 20 minutes, and then cooled under two conditions of a cooling rate of 1 ° C./sec and 0.5 ° C./sec. Both sintering and cooling were performed in a mixed gas atmosphere of N ₂ / H ₂ = 90/10. Table 4 shows the tensile strength and hardness of the sintered parts thus obtained.
[0042]
[Table 1]

[0043]
[Table 2]

[0044]
[Table 3]

[0045]
[Table 4]

[0046]
As can be seen from Table 2, according to the method of the present invention, a powder compact excellent in density, hardness and strength can be obtained.
[0047]
Further, as can be seen from Table 3, the one containing 0.1% by mass or less of the lubricant (powder types 1 to 4) is the one containing 0.1% by mass or more of the lubricant (powder types 5 and 6). In comparison, the amount of chipping of the formed body due to the cutting process is small, and the finished surface roughness is improved. Further, the chipping amount is smaller than that of the conventional warm-formed product (powder type 5) as shown in the above-mentioned “POWDER MIXES WITH HIGH GREEN STRENGTH”, and the finished surface roughness is improved.
[0048]
Furthermore, when quenching is performed at a cooling rate of 1 ° C./sec or more in the cooling process in the sintering step, a sintered part having excellent tensile strength and hardness can be obtained.
[0049]
【The invention's effect】
As described above, according to the method of the present invention, it is possible to obtain a molded body capable of performing high-quality cutting or grinding by a mold lubrication molding method, and to perform machining before sintering due to a complicated shape or the like. It is possible to produce a sintered part to which high strength and high quality are compatible.
[0050]
In addition, mixed powder using Fe or Fe alloy powder having an average particle size of 60 to 100 μm by a sedimentation method, mixed powder added with at least one metal selected from Ni, Cu, Mo, Cr, and Mn, Alternatively, a sintered part manufactured by the method of the present invention using a mixed powder using metal particles having a particle size of 45 μm or less occupying 80% or more of the total amount of the added metal powder as the added metal powder has strength and mechanical strength. The quality of the machined surface is improved.
[0051]
In addition, a method in which the cooling rate in the cooling step of the sintering step is set to 1 ° C./sec or more can integrate the sintering and quenching steps, which is advantageous in terms of productivity.
[Brief description of the drawings]
FIG. 1 is a process diagram showing the outline of the method of the present invention. FIG. 2 is an image diagram showing the relationship between the particle size of powder particles and the apparent density and strength of a compact.
1 mixed powder 2 mold 3 molded body 4 sintered part

Claims

１）還元鉄粉７０質量％以上、添加金属粉２９質量％以下、２）Ｆｅの水アトマイズ粉７０質量％以上、添加金属粉２９質量％以下、３）Ｆｅ合金の水アトマイズ粉８０質量％以上、添加金属粉１９質量％以下、
上記１）〜３）のいずれかと、カーボン粉：０．４〜１．０質量％と、潤滑剤：０．１質量％以下とを混合した粉末を準備する工程、
その混合粉を金型潤滑成形する工程、
金型潤滑成形して得られた成形体を切削または研削する工程、
切削または研削した成形体を焼結する工程を含む焼結部品の製造方法。1) 70% by mass or less of reduced iron powder, 29% by mass or less of added metal powder 2) 70% by mass or more of water atomized powder of Fe, 29% by mass or less of added metal powder 3) 80% by mass or more of water atomized powder of Fe alloy , Added metal powder 19% by mass or less,
A step of preparing a powder obtained by mixing any one of the above 1) to 3), carbon powder: 0.4 to 1.0% by mass, and lubricant: 0.1% by mass or less;
A step of lubricating the mixed powder in a mold,
A step of cutting or grinding a molded body obtained by mold lubrication molding,
A method for producing a sintered part, comprising a step of sintering a cut or ground compact.

混合粉の金型潤滑成形を、混合粉及び金型の温度が１００℃以上、成形圧６００ＭＰａ以上の条件下で行う請求項１に記載の焼結部品の製造方法。The method for producing a sintered part according to claim 1, wherein the mold lubrication molding of the mixed powder is performed under the conditions of a temperature of the mixed powder and the mold of 100C or more and a molding pressure of 600MPa or more.

還元鉄粉又はＦｅもしくはＦｅ合金の水アトマイズ粉として、沈降法による平均粒径が６０〜１００μｍのものを用いる請求項１または２に記載の焼結部品の製造方法。The method for producing a sintered component according to claim 1 or 2, wherein the reduced iron powder or the water atomized powder of Fe or Fe alloy has a mean particle size of 60 to 100 µm by a sedimentation method.

カーボン粉として、粒径（ＪＩＳＺ８８０１のふるい法による粒径）２０μｍ以下の粒子がカーボン粉の総量の７０％以上を占めるものを用いる請求項１または２に記載の焼結部品の製造方法。The method for producing a sintered component according to claim 1 or 2, wherein particles having a particle size (particle size of 20 μm or less according to JISZ8801) occupying 70% or more of the total amount of the carbon powder are used as the carbon powder.

添加金属粉がＮｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎの中から選ばれた少なくとも１種であり、この添加金属粉として粒径（ＪＩＳＺ８８０１のふるい法による粒径）４５μｍ以下の金属粒子が添加金属粉の総量の８０％以上を占めるものを用いる請求項１または２に記載の焼結部品の製造方法。The additive metal powder is at least one selected from the group consisting of Ni, Cu, Mo, Cr, and Mn, and as the additive metal powder, metal particles having a particle size of 45 μm or less (particle size according to a sieving method of JISZ8801) are used. The method for producing a sintered part according to claim 1 or 2, wherein a component occupying 80% or more of the total amount of the component is used.

焼結工程における冷却過程での部品の冷却速度を１℃／ｓｅｃ以上とする請求項１乃至５のいずれかに記載の焼結部品の製造方法。The method for manufacturing a sintered part according to any one of claims 1 to 5, wherein a cooling rate of the part during the cooling step in the sintering step is 1 ° C / sec or more.

請求項１乃至６のいずれかに記載の方法で製造される焼結部品であって、焼結前に切削または研削された部位に焼結肌を残していることを特徴とする焼結部品。A sintered part produced by the method according to any one of claims 1 to 6, wherein a sintered surface is left in a portion cut or ground before sintering.

Ｆｅの質量％が７０〜９９％であり、Ｃ及びＦｅ以外の金属成分が残部を占めることを特徴とする請求項７に記載の焼結部品。The sintered component according to claim 7, wherein the mass% of Fe is 70 to 99%, and a metal component other than C and Fe accounts for the balance.

焼結前の切削または研削により、加工面の面粗さがＲｚ＝２．５以下となっており、かつ、その加工面に粉末の脱落があることを特徴とする請求項７または８に記載の焼結部品。The surface roughness of the processed surface is reduced to Rz = 2.5 or less by cutting or grinding before sintering, and the processed surface has powder falling off. Sintered parts.