JP5389577B2 - Method for producing sintered body by powder metallurgy - Google Patents

Method for producing sintered body by powder metallurgy Download PDF

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JP5389577B2
JP5389577B2 JP2009209266A JP2009209266A JP5389577B2 JP 5389577 B2 JP5389577 B2 JP 5389577B2 JP 2009209266 A JP2009209266 A JP 2009209266A JP 2009209266 A JP2009209266 A JP 2009209266A JP 5389577 B2 JP5389577 B2 JP 5389577B2
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powder
mass
alloy steel
amount
sintered body
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JP2010100932A (en
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繁 宇波
由紀子 尾▲崎▼
唯之 筒井
祐司 山西
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JFE Steel Corp
Hitachi Powdered Metals Co Ltd
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Hitachi Powdered Metals Co Ltd
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Priority to JP2009209266A priority Critical patent/JP5389577B2/en
Priority to US13/120,702 priority patent/US20110176950A1/en
Priority to CN2009801376315A priority patent/CN102165083B/en
Priority to EP09816266.2A priority patent/EP2339042B1/en
Priority to KR1020117006410A priority patent/KR101382304B1/en
Priority to PCT/JP2009/066865 priority patent/WO2010035853A1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps

Description

本発明は、粉末冶金法による自動車用高強度焼結部品等に好適な焼結体の製造方法に関するものである。   The present invention relates to a method for producing a sintered body suitable for automotive high-strength sintered parts by powder metallurgy.

鉄粉や合金鋼粉を金型内で加圧して成形した後、焼結して焼結体を得る粉末冶金法は、高い寸怯精度を要求されるギヤ等の自動車用部品の製造に広く使用されている。自動車用部品として使用される焼結体は、原料粉（鉄粉、合金鋼粉）にＣｕ粉、黒鉛粉、潤滑剤等を混合した混合粉を金型に充填して加圧成形し、これを焼結することにより製造され、―般に６．０〜７．２ｇ／ｃｍ３程度の密度を有する。 The powder metallurgy method, in which iron powder or alloy steel powder is pressed and molded in a mold and then sintered to obtain a sintered body, is widely used in the manufacture of automotive parts such as gears that require high dimensional accuracy. It is used. Sintered bodies used as automotive parts are filled with powder mixed with raw powder (iron powder, alloy steel powder), Cu powder, graphite powder, lubricant, etc. And generally has a density of about 6.0 to 7.2 g / cm 3 .

自動車部品の中でも高強度を要求される部品（以下、自動車用高強度焼結部品という）を製造する場合は、合金元素（たとえば、Ｎｉ、Ｃｕ、Ｍｏ、Ｃｒ、Ｍｎ等）を鉄基粉末に添加して原料粉として使用する技術が実用化されている。このような原料粉にＣｕ粉、黒鉛粉、潤滑剤等を混合して加圧成形し、さらに焼結する手順は、上記した通常の自動車用部品と同様である。但し、自動車用高強度焼結部品では、必要に応じて、光輝焼入れ焼戻し処理、浸炭処理等が施される。   When manufacturing parts that require high strength among automobile parts (hereinafter referred to as "high-strength sintered parts for automobiles"), alloy elements (for example, Ni, Cu, Mo, Cr, Mn, etc.) are used as iron-based powders. The technology of adding and using as raw material powder has been put into practical use. The procedure of mixing Cu powder, graphite powder, lubricant, etc. into such raw material powder, press-molding it, and further sintering it is the same as the above-described ordinary automotive parts. However, high-strength sintered parts for automobiles are subjected to a bright quenching and tempering process, a carburizing process, and the like as necessary.

なお、合金元素を添加する方法としては、予め鉄基粉末を合金化（いわゆる予合金化）する方法、所望の合金元素を含有する合金用粉末を結合剤とともに鉄基粉末と混合する方法、合金用粉末を鉄基粉末と混合する（結合剤を用いない）方法、合金用粉末を鉄基粉末と混合した後に高温に保持して冶金的に結合させる（いわゆる拡散付着）方法、などがある。これらの方法で得られる合金鋼粉 (あるいは混合粉体)の特性や合金元素の均一度、焼結による合金元素の拡散状態はそれぞれ異なる。このため、合金元素の選択および添加方法の選択は、焼結体の品質に多大な影響を及ぼす重要な因子である。   In addition, as a method of adding an alloy element, a method of previously alloying an iron-based powder (so-called pre-alloying), a method of mixing an alloy powder containing a desired alloy element with an iron-based powder together with a binder, an alloy There are a method of mixing a powder for iron with an iron-based powder (without using a binder), a method of mixing an alloy powder with an iron-based powder, and then metallurgically bonding them by holding them at a high temperature (so-called diffusion adhesion). The characteristics of alloy steel powder (or mixed powder) obtained by these methods, the uniformity of alloy elements, and the diffusion state of alloy elements by sintering differ. For this reason, selection of alloy elements and selection of addition methods are important factors that greatly affect the quality of the sintered body.

例えば、特許文献１には、Ｎｉ、Ｃｕ、Ｍｏ等の金属粉末を鉄粉に拡散付着したものを原料粉として使用する技術が開示されている。この技術は、原料粉を加圧成形した後に行なう焼結によって、鉄粉の表面に付着した金属粉末から鉄粉中にＮｉ、Ｃｕ、Ｍｏ等が拡散し、鉄粉を合金化する。ところが、Ｎｉ、Ｃｕ、Ｍｏ等の拡散には長時間を要するので、鉄粉を十分に合金化するためには長時間の焼結が必要となり、焼結の生産性が低下する。さらに、自動車用高強度焼結部品に要求される強度を得るためには、Ｎｉ、Ｃｕ、Ｍｏ等の金属粉末を多量に使用しなければならないので、原料コストの上昇を招く。   For example, Patent Document 1 discloses a technique in which a metal powder such as Ni, Cu, or Mo diffused and adhered to iron powder is used as a raw material powder. In this technique, Ni, Cu, Mo, etc. diffuse into the iron powder from the metal powder adhering to the surface of the iron powder by sintering after the raw material powder is pressure-molded to alloy the iron powder. However, since diffusion of Ni, Cu, Mo, etc. takes a long time, long-time sintering is required to sufficiently alloy the iron powder, and the productivity of the sintering is reduced. Furthermore, in order to obtain the strength required for high-strength sintered parts for automobiles, a large amount of metal powder such as Ni, Cu, Mo, etc. must be used, leading to an increase in raw material costs.

また、特許文献１に開示された技術で製造した焼結体は、ＮｉやＣｕを含有するが、Ｎｉは人体に有害な元素であり、Ｃｕは鋼材をリサイクルした場合に有害な元素としてスクラップに蓄積される問題がある。そこで、ＮｉやＣｕを含有しない合金鋼粉が検討されている。
例えば、特許文献２には、Ｍｏ：０．２〜１．４質量％、Ｃｒ：０．１〜０．３質量％、Ｃ：０．１０質量％以下、Ｏ：０．３質量％以下を含有する合金鋼粉が開示されている。Ｃｒ、Ｍｏは焼入れ性を改善する作用を有するので、この合金鋼粉から製造される焼結体は、比較的高い強度を有する。しかし、特許文献２に開示された合金鋼粉はＣｒ含有量が十分でないため、自動車用高強度焼結部品に要求されるような高い強度は得られない。Ｃｒ、Ｍｏの含有量を増加すれば、この問題は解決するが、Ｃｒ、Ｍｏを多量に添加すると、合金鋼粉の圧縮性の低下や原料コストの上昇を招いてしまう。 Moreover, although the sintered compact manufactured with the technique disclosed by patent document 1 contains Ni and Cu, Ni is an element harmful to a human body, and Cu is scraped as a harmful element when steel materials are recycled. There are problems that accumulate. Therefore, alloy steel powders that do not contain Ni or Cu have been studied.
For example, Patent Document 2 includes Mo: 0.2 to 1.4% by mass, Cr: 0.1 to 0.3% by mass, C: 0.10% by mass or less, and O: 0.3% by mass or less. An alloy steel powder is disclosed. Since Cr and Mo have an effect of improving hardenability, a sintered body produced from this alloy steel powder has a relatively high strength. However, since the alloy steel powder disclosed in Patent Document 2 does not have a sufficient Cr content, the high strength required for high-strength sintered parts for automobiles cannot be obtained. Increasing the content of Cr and Mo solves this problem, but adding a large amount of Cr and Mo causes a decrease in compressibility of alloy steel powder and an increase in raw material cost.

特許文献３には、Ｃ：０．１質量％以下、Ｍｎ：０．０８質量％以下、Ｃｒ：０．５〜３質量％、Ｍｏ：０．１〜２質量％、Ｓ：０．０１質量％以下、Ｐ：０．２質量％以下、Ｏ：０．２質量％以下を含有する合金鋼粉が開示されている。しかし、特許文献３の合金鋼粉は、焼入れ性を向上させる作用を有するＭｎの含有量が十分ではないため、自動車用高強度焼結部品に要求されるような高い強度は得られない。Ｍｎ含有量を増加すれば、この問題は解決するが、Ｍｎは酸化され易い元素であるため、Ｍｎを多量に添加すると、加圧成形後の焼結によって、或いは焼結後の熱処理によって酸化物が生成し、焼結体の強度が低下してしまう。   In Patent Document 3, C: 0.1 mass% or less, Mn: 0.08 mass% or less, Cr: 0.5-3 mass%, Mo: 0.1-2 mass%, S: 0.01 mass% Alloy steel powder containing no more than%, P: 0.2 mass% or less, and O: 0.2 mass% or less is disclosed. However, since the alloy steel powder of Patent Document 3 does not have a sufficient content of Mn having an effect of improving the hardenability, high strength required for high-strength sintered parts for automobiles cannot be obtained. Increasing the Mn content solves this problem, but Mn is an element that is easily oxidized. Therefore, when Mn is added in a large amount, the oxide is oxidized by sintering after pressure forming or by heat treatment after sintering. Is generated, and the strength of the sintered body is reduced.

特許文献４には、Ｃｒ：１．３〜１．７質量％、Ｍｏ：０．１５〜０．３質量％、Ｍｎ：０．０９〜０．３質量％、Ｃ：０．０１質量％以下、Ｏ：０．２５質量％以下を含有する合金鋼粉が開示されている。しかし、特許文献４の合金鋼粉は、Ｃｒ含有量が多いため合金鋼粉の圧縮性が低下し、焼結体の密度が低くなる。また、Ｃｒは酸化され易い元素であるため、Ｃｒを多量に添加すると、加圧成形後の焼結によって、或いは焼結後の熱処理によって酸化物が生成し、焼結体の強度が低下してしまう。   In Patent Document 4, Cr: 1.3-1.7% by mass, Mo: 0.15-0.3% by mass, Mn: 0.09-0.3% by mass, C: 0.01% by mass or less , O: Alloy steel powder containing 0.25% by mass or less is disclosed. However, since the alloy steel powder of Patent Document 4 has a high Cr content, the compressibility of the alloy steel powder is lowered and the density of the sintered body is lowered. In addition, since Cr is an element that is easily oxidized, if a large amount of Cr is added, an oxide is generated by sintering after pressure forming or by heat treatment after sintering, and the strength of the sintered body decreases. End up.

特公昭４５−９６４９号公報Japanese Patent Publication No. 45-9649 特開昭６１−１１７２０１号公報JP 61-117201 A 特開平５−２８７４５２号公報Japanese Patent Laid-Open No. 5-287852 特表２００５−５３００３７号公報JP 2005-530037 A

したがって本発明の目的は、以上のような従来技術の課題を解決し、粉末冶金法による焼結体の製造方法であって、ＮｉやＣｕを添加しない粉末冶金用合金鋼粉を用いて、高強度の焼結体を安価に製造することができる方法を提供することにある。   Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, a method for producing a sintered body by powder metallurgy, and using alloy steel powder for powder metallurgy without adding Ni or Cu, An object of the present invention is to provide a method capable of producing a strong sintered body at low cost.

本発明者は、上記課題を解決することができる粉末冶金用合金鋼粉の成分条件および焼結体の製造条件について詳細な検討を行った。その結果、粉末冶金用合金鋼粉のＣｒ含有量、Ｍｎ含有量、Ｍｏ含有量を最適化し、且つ原料粉を特定の条件で高圧成形および高温焼結することにより、ＮｉやＣｕを添加せず且つＭｏ添加量が比較的少ない合金鋼粉を用い、自動車用高強度焼結部品として使用可能な高強度焼結体を安価に製造できることを見出した。   The present inventor has conducted detailed studies on the component conditions of the alloy steel powder for powder metallurgy and the manufacturing conditions of the sintered body that can solve the above-mentioned problems. As a result, by optimizing the Cr content, Mn content, and Mo content of alloy steel powder for powder metallurgy, and by adding high-pressure molding and high-temperature sintering of the raw material powder under specific conditions, no Ni or Cu is added. Moreover, it has been found that a high-strength sintered body that can be used as a high-strength sintered part for automobiles can be manufactured at low cost by using alloy steel powder with a relatively small amount of Mo addition.

また、酸素量がある程度高い合金鋼粉を用いても、合金鋼粉に十分な量の黒鉛粉末を添加し、焼結時に黒鉛と酸素を反応させて還元することにより、焼結体の強度低下が抑えられることが判った。すなわち、上記の粉末冶金用合金鋼粉は、易酸化元素であるＣｒやＭｎを含有するため、その酸素量を低減するためには、１１００℃程度の高温の減圧雰囲気中で還元処理する必要がある。しかし、このような高価な還元処理ではなく、安価な水素ガス雰囲気による還元処理を施した酸素量がある程度高い合金鋼粉を用いても、十分な量の黒鉛粉末を添加し、焼結すれば、焼結時に合金鋼粉の酸素が黒鉛と反応して還元されて除去されるため、焼結体の強度低下が抑えられることが判った。
また、焼結時において合金鋼粉中の酸素の還元に使用される黒鉛量は、主に合金鋼粉のＣｒ量、Ｍｎ量およびこれら元素の酸化率によって決まるので、焼結体の強度に重要な影響を与える焼結体中のＣ量は、合金鋼粉のＣｒ量、Ｍｎ量およびこれらの元素の酸化率により決定される量の黒鉛を付加的に添加することで制御できることが判った。 In addition, even when alloy steel powder with a certain amount of oxygen is used, the strength of the sintered body is reduced by adding a sufficient amount of graphite powder to the alloy steel powder and reacting and reducing graphite and oxygen during sintering. Was found to be suppressed. That is, the above-mentioned alloy steel powder for powder metallurgy contains oxidizable elements such as Cr and Mn. Therefore, in order to reduce the amount of oxygen, it is necessary to perform a reduction treatment in a high-temperature reduced pressure atmosphere of about 1100 ° C. is there. However, instead of such an expensive reduction treatment, even if an alloy steel powder with a certain amount of oxygen that has been reduced in an inexpensive hydrogen gas atmosphere is used, if a sufficient amount of graphite powder is added and sintered, It has been found that, during sintering, oxygen in the alloy steel powder reacts with graphite to be reduced and removed, so that a decrease in strength of the sintered body can be suppressed.
Also, the amount of graphite used to reduce oxygen in alloy steel powder during sintering is mainly determined by the amount of Cr and Mn in the alloy steel powder and the oxidation rate of these elements, so it is important for the strength of the sintered body. It has been found that the amount of C in the sintered body having a significant influence can be controlled by additionally adding graphite in an amount determined by the amount of Cr in the alloy steel powder, the amount of Mn, and the oxidation rate of these elements.

本発明はこのような知見に基づきなされたもので、以下を要旨とするものである。
［1］Ｃｒ：０．３〜０．７質量％、Ｍｎ：０．１〜０．５質量％、Ｍｏ：０．１〜０．５質量％、Ｏ：０．２５〜０．５質量％を含有し、残部がＦｅおよび不可避的不純物からなる粉末冶金用合金鋼粉を用い、該粉末冶金用合金鋼粉またはこれを含む混合粉を７００ＭＰａ以上の圧力で成形した後、１１５０〜１３００℃の温度で焼結することを特徴とする粉末冶金法による焼結体の製造方法。
［2］上記［1］の製造方法において、混合粉が黒鉛粉末を含むことを特徴とする粉末冶金法による焼結体の製造方法。
［3］上記［1］または［2］の製造方法において、混合粉が、焼結体中に残留させるＣ量と、焼結時に粉末冶金用合金鋼粉中の酸素と反応するＣ量の合計に相当する量の黒鉛粉末を含むことを特徴とする粉末冶金法による焼結体の製造方法。 The present invention has been made on the basis of such findings and has the following gist.
[1] Cr: 0.3 to 0.7 mass%, Mn: 0.1 to 0.5 mass%, Mo: 0.1 to 0.5 mass%, O: 0.25 to 0.5 mass% Powder metallurgy alloy steel powder consisting of Fe and unavoidable impurities, and forming the powder metallurgy alloy steel powder or mixed powder containing this at a pressure of 700 MPa or more, A method for producing a sintered body by powder metallurgy, which comprises sintering at a temperature.
[2] A method for producing a sintered body by a powder metallurgy method, wherein the mixed powder contains graphite powder in the production method of [1].
[3] In the production method of [1] or [2] above, the total amount of C that the mixed powder remains in the sintered body and the amount of C that reacts with oxygen in the alloy steel powder for powder metallurgy during sintering A method for producing a sintered body by a powder metallurgy method, comprising an amount of graphite powder corresponding to

［4］上記［2］の製造方法において、粉末冶金用合金鋼粉に、下記（1）式の条件を満足する量［％Ｇｒ］（粉末冶金用合金鋼粉の質量に対する質量％）の黒鉛粉末を添加することを特徴とする請求項２に記載の粉末冶金法による焼結体の製造方法。
［％Ｇｒ］＝ｔ×（α×０．４６×［％Ｃｒ］＋β×０．２９×［％Ｍｎ］）＋γ＋［％Ｃ］ …（1）
但し ［％Ｃｒ］：粉末冶金用合金鋼粉中のＣｒ量（質量％）
［％Ｍｎ］：粉末冶金用合金鋼粉中のＭｎ量（質量％）
［％Ｃ］：黒鉛粉末のなかで、焼結体中に残留させるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）
α：粉末冶金用合金鋼粉中のＣｒの酸化率
β：粉末冶金用合金鋼粉中のＭｎの酸化率
γ：黒鉛粉末のなかで、粉末冶金用合金鋼粉に吸着されている酸素分および焼結雰囲気中に含まれる酸素分との反応に消費されるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）。但し、γ≦０．２質量％
ｔ：０．２５〜０．７５ [4] In the manufacturing method of [2] above, the amount of graphite [% Gr] (mass% with respect to the mass of the alloy steel powder for powder metallurgy) satisfying the condition of the following formula (1) in the alloy steel powder for powder metallurgy: Powder is added, The manufacturing method of the sintered compact by the powder metallurgy method of Claim 2 characterized by the above-mentioned.
[% Gr] = t × (α × 0.46 × [% Cr] + β × 0.29 × [% Mn]) + γ + [% C] (1)
However, [% Cr]: Cr content (% by mass) in alloy steel powder for powder metallurgy
[% Mn]: Mn content (% by mass) in alloy steel powder for powder metallurgy
[% C]: amount of C remaining in the sintered body in the graphite powder (mass% with respect to the mass of the alloy steel powder for powder metallurgy)
α: oxidation rate of Cr in alloy steel powder for powder metallurgy β: oxidation rate of Mn in alloy steel powder for powder metallurgy γ: oxygen content adsorbed by alloy steel powder for powder metallurgy in graphite powder and C amount (mass% with respect to the mass of the alloy steel powder for powder metallurgy) consumed in the reaction with oxygen contained in the sintering atmosphere. However, γ ≦ 0.2 mass%
t: 0.25 to 0.75

本発明によれば、粉末治金法による焼結体の製造方法において、ＮｉやＣｕを添加せず且つＭｏ添加量が比較的少ない合金鋼粉を用い、自動車用高強度焼結部品として使用可能な高強度焼結体を安価に製造することができる。   According to the present invention, in a method for producing a sintered body by a powder metallurgy method, alloy steel powder that does not contain Ni or Cu and has a relatively small amount of Mo addition can be used as a high-strength sintered part for automobiles. A high strength sintered body can be manufactured at low cost.

実施例２の試料番号２，５〜７の成形圧力と引張強さとの関係を、既存高強度材である試料番号８〜１１のそれと比較して示したグラフThe graph which showed the relationship between the molding pressure of sample numbers 2-5 of Example 2, and the tensile strength compared with that of sample numbers 8-11 which are the existing high strength materials.

まず、本発明で用いる粉末冶金用合金鋼粉（以下、単に「合金鋼粉」という場合がある）の化学成分とその限定理由について説明する。
・Ｃｒ：０．３〜０．７質量％
Ｃｒは焼入れ性を向上させる元素であり、焼結後の焼入れによってマルテンサイト変態を生じさせることによって、焼結体の強度を高める効果を有する。Ｃｒ含有量が０．３質量％未満では、その効果が十分でない。―方、Ｃｒ含有量が０．７質量％を超えると、固溶硬化により各粒子の硬度が増加し、且つ合金鋼粉の酸素量が増加することにより、加圧成形の際の圧縮性が低下する。さらに、焼結後の焼入れ時の雰囲気による酸化が増加するため、焼入れ性向上による焼結体の強度の大幅な向上は期待できず、むしろ圧縮性低下による焼結体の強度低下が顕著になる。このためＣｒ含有量は０．３〜０．７質量％とする。 First, chemical components of alloy steel powder for powder metallurgy used in the present invention (hereinafter sometimes simply referred to as “alloy steel powder”) and the reasons for limitation thereof will be described.
・ Cr: 0.3-0.7 mass%
Cr is an element that improves hardenability and has the effect of increasing the strength of the sintered body by causing martensitic transformation by quenching after sintering. If the Cr content is less than 0.3% by mass, the effect is not sufficient. -On the other hand, if the Cr content exceeds 0.7 mass%, the hardness of each particle increases due to solid solution hardening, and the oxygen content of the alloy steel powder increases, so that the compressibility during pressure forming is increased. descend. Furthermore, since the oxidation due to the atmosphere during quenching after sintering increases, a significant improvement in the strength of the sintered body due to an improvement in hardenability cannot be expected, but rather a decrease in the strength of the sintered body due to a decrease in compressibility becomes significant. . For this reason, Cr content shall be 0.3-0.7 mass%.

・Ｍｎ：０．１〜０．５質量％
Ｍｎは焼入れ性を向上させる元素であり、焼結後の焼入れによってマルテンサイト変態を生じさせることによって、焼結体の強度を高める効果を有する。Ｍｎ含有量が０．１質量％未満では、その効果が十分でない。―方、Ｍｎ含有量が０．５質量％を超えると、固溶硬化により各粒子の硬度が増加し、且つ合金鋼粉の酸素量が増加することにより、加圧成形の際の圧縮性が低下し、焼結体の強度が低下する。また、焼結を弱酸化性雰囲気（例えば、炭化水素変性ガス雰囲気等）で行う場合には、Ｍｎを過剰に含有すると焼結後の焼入れ時の雰囲気による酸化が増加するため、焼入れ性向上による焼結体の強度の大幅な向上は期待できず、むしろ圧縮性低下による焼結体の強度低下が顕著になる。このためＭｎ含有量は０．１〜０．５質量％、好ましくは０．１〜０．２５質量％とする。 Mn: 0.1 to 0.5% by mass
Mn is an element that improves hardenability, and has the effect of increasing the strength of the sintered body by causing martensitic transformation by quenching after sintering. If the Mn content is less than 0.1% by mass, the effect is not sufficient. -On the other hand, if the Mn content exceeds 0.5% by mass, the hardness of each particle is increased by solid solution hardening, and the oxygen content of the alloy steel powder is increased. The strength of the sintered body is reduced. In addition, when sintering is performed in a weakly oxidizing atmosphere (for example, a hydrocarbon-modified gas atmosphere), if Mn is excessively contained, oxidation due to the atmosphere at the time of quenching after sintering increases, thereby improving hardenability. A significant improvement in the strength of the sintered body cannot be expected, but rather a significant decrease in the strength of the sintered body due to a decrease in compressibility. Therefore, the Mn content is 0.1 to 0.5% by mass, preferably 0.1 to 0.25% by mass.

・Ｍｏ：０．１〜０．５質量％
Ｍｏは焼入れ性向上、固溶強化および析出強化によって、焼結体の強度を高める効果を有する。Ｍｏ含有量が０．１質量％未満では、その効果が十分でない。―方、Ｍｏ含有量が０．５質量％を超えると、加圧成形の際の圧縮性が低下するため、焼結体の強度の大幅な向上は期待できず、むしろＭｏの添加量増加に伴って原料コストが著しく上昇する。このためＭｏ含有量は０．１〜０．５質量％とする。 -Mo: 0.1-0.5 mass%
Mo has the effect of increasing the strength of the sintered body by improving hardenability, solid solution strengthening and precipitation strengthening. If the Mo content is less than 0.1% by mass, the effect is not sufficient. -On the other hand, if the Mo content exceeds 0.5% by mass, the compressibility at the time of pressure molding will decrease, so a significant improvement in the strength of the sintered body cannot be expected, but rather the Mo addition amount will increase. Along with this, the raw material cost rises significantly. For this reason, Mo content shall be 0.1-0.5 mass%.

・Ｏ：０．２５〜０．５質量％
Ｏ含有量を０．２５質量％未満にするには、非常に清浄な還元雰囲気中または減圧雰囲気下での還元処理が必要となり、製造コストが増大する。一方、Ｏ含有量が０．５質量％を超えると圧縮性が低下し、且つ焼結が阻害されるので、焼結体の強度が低下する。このためＯ含有量は０．２５〜０．５質量％、好ましくは０．２５〜０．３５質量％とする。
一般に、Ｃｒ、Ｍｎ等のような易酸化元素を含有する合金鋼粉では、Ｏ含有量を少なくしようとすると、非常に清浄な還元雰囲気中または減圧雰囲気下での還元処理が必要となり、製造コストが増大する。これに対して本発明者らは、安価な通常の還元雰囲気中で還元処理を行うことで合金鋼粉中のＯ含有量がある程度高くなっても、後の焼結工程において、合金鋼粉中の酸素を還元できることを見出した。このため本発明では、合金鋼粉中のＯ含有量を０．２５〜０．５質量％とし、一般の易酸化元素を含有する合金鋼粉に較べて高めとしてある。
また、本発明で用いる合金鋼粉は、Ｃ含有量を０．０１質量％以下、望ましくは０．００５質量％以下とすることが好ましい。Ｃ含有量が０．０１質量％を超えると、合金鋼粉の各粒子の硬度が過剰に高まるので、加圧成形の際の圧縮性が低下し、焼結体の強度が低下しやすい。
上記した成分以外の残部は、Ｆｅおよび不可避的不純物である。 ・ O: 0.25 to 0.5 mass%
In order to reduce the O content to less than 0.25% by mass, a reduction treatment in a very clean reducing atmosphere or a reduced pressure atmosphere is required, which increases the manufacturing cost. On the other hand, when the O content exceeds 0.5% by mass, the compressibility is lowered and the sintering is inhibited, so that the strength of the sintered body is lowered. Therefore, the O content is 0.25 to 0.5% by mass, preferably 0.25 to 0.35% by mass.
In general, in an alloy steel powder containing an easily oxidizable element such as Cr, Mn, etc., reducing the O content requires a reduction treatment in a very clean reducing atmosphere or a reduced pressure atmosphere, which is a manufacturing cost. Will increase. On the other hand, the present inventors perform reduction treatment in an inexpensive ordinary reducing atmosphere, and even if the O content in the alloy steel powder increases to some extent, Of oxygen can be reduced. For this reason, in this invention, O content in alloy steel powder shall be 0.25-0.5 mass%, and it is set as high compared with the alloy steel powder containing a general easily oxidizable element.
The alloy steel powder used in the present invention preferably has a C content of 0.01% by mass or less, desirably 0.005% by mass or less. If the C content exceeds 0.01% by mass, the hardness of each particle of the alloy steel powder is excessively increased, so that the compressibility during pressure forming is lowered and the strength of the sintered body is likely to be lowered.
The balance other than the above components is Fe and inevitable impurities.

以上のような合金鋼粉は、例えば、次のようにして製造される。
所定の化学成分を有する合金鋼を溶製し、水アトマイズ法で合金鋼粉を製造する。この水アトマイズ法では、操業条件や使用する装置の構成に特別な制限はなく、従来公知の技術を適用すればよい。次いで、その合金鋼粉に還元熱処理を施す。この還元熱処理についても、操業条件や使用する装置の構成に特別な制限はなく、従来公知の技術を適用し、水素ガス雰囲気または真空雰囲気で行なえばよい。なお、本発明では、必要に応じて合金鋼粉に添加される黒鉛粉末により、合金鋼粉中の酸素を後の焼結工程で除去できるので、安価な水素ガス雰囲気を用いて還元処理を行うことができる。 The alloy steel powder as described above is manufactured, for example, as follows.
Alloy steel having a predetermined chemical component is melted and alloy steel powder is produced by a water atomization method. In this water atomization method, there are no particular restrictions on the operating conditions and the configuration of the apparatus used, and a conventionally known technique may be applied. Next, the alloy steel powder is subjected to a reduction heat treatment. This reduction heat treatment is not particularly limited in the operating conditions and the configuration of the apparatus used, and may be performed in a hydrogen gas atmosphere or a vacuum atmosphere by applying a conventionally known technique. In the present invention, the oxygen in the alloy steel powder can be removed in the subsequent sintering step by the graphite powder added to the alloy steel powder as necessary, so that the reduction treatment is performed using an inexpensive hydrogen gas atmosphere. be able to.

次に、本発明の製造条件について説明する。
本発明では、上述した合金鋼粉に必要に応じて他の金属粉末、黒鉛粉末、潤滑剤等の１種以上を添加し混合した後、合金鋼粉またはこれを含む混合粉を金型に充填して加圧成形し、次いで焼結を行なって焼結体を得る。
前記潤滑剤としては、例えば、ステアリン酸亜鉛、ステアリン酸リチウム、オレイン酸、ステアリン酸アミド、エチレンビスステアロアミド等の公知の潤滑剤の１種以上を使用することができる。潤滑剤の配合量は、合金鋼粉の質量に対して０．２〜１質量％が好ましい。 Next, the manufacturing conditions of the present invention will be described.
In the present invention, one or more of other metal powders, graphite powders, lubricants, and the like are added to the above-described alloy steel powder as necessary, and then the alloy steel powder or mixed powder containing the same is filled into the mold. Then, pressure forming is performed, and then sintering is performed to obtain a sintered body.
As the lubricant, for example, one or more kinds of known lubricants such as zinc stearate, lithium stearate, oleic acid, stearamide, ethylene bisstearamide, and the like can be used. The blending amount of the lubricant is preferably 0.2 to 1% by mass with respect to the mass of the alloy steel powder.

前記黒鉛粉末については、焼結性をより向上させるために合金鋼粉の酸素を低減させたい場合には、焼結体中に残留させるＣ量と、焼結時に合金鋼粉中の酸素と反応するＣ量の合計に相当する量の黒鉛粉末を添加すればよい。すなわち、後述するような焼結温度の範囲では、合金鋼粉中の酸素は合金鋼粉中のＣｒやＭｎよりもＣと反応し易く、黒鉛粉末の形態で与えられたＣと結合し、ＣＯガスとして還元除去される。この分、焼結体中に残留するＣ量が減少することになるので、焼結体中に所望のＣ量を残留させるためには、そのＣ量の減少分（すなわち、焼結時に合金鋼粉中の酸素と反応するＣ量）を予め余分に添加しておけばよい。   For the graphite powder, when it is desired to reduce the oxygen in the alloy steel powder in order to further improve the sinterability, the amount of C remaining in the sintered body and the reaction with the oxygen in the alloy steel powder during sintering An amount of graphite powder corresponding to the total amount of C to be added may be added. That is, in the range of the sintering temperature as described later, oxygen in the alloy steel powder reacts more easily with C than Cr and Mn in the alloy steel powder, and combines with C given in the form of graphite powder, and CO. It is reduced and removed as a gas. Since the amount of C remaining in the sintered body is reduced by this amount, in order to retain the desired amount of C in the sintered body, the amount of decrease in the C amount (that is, alloy steel during sintering) Extra amount of C that reacts with oxygen in the powder may be added in advance.

焼結体に残留するＣ量は焼結体の強度に大きな影響を与えるため、焼結体中に残留するＣ量を制御すること、すなわち合金鋼粉中の酸素と反応するＣ量を予め決定することは、極めて重要である。この課題に対し、本発明者らは、焼結時において合金鋼粉中の酸素の還元に使用される黒鉛量は、主に合金鋼粉のＣｒ量、Ｍｎ量およびこれらの元素の酸化率によって決まること、したがって、焼結体に残留させるＣ量は、合金鋼粉のＣｒ量、Ｍｎ量およびこれらの元素の酸化率により決定される量の黒鉛を付加的に添加することで制御できることを見出した。   Since the amount of C remaining in the sintered body has a great influence on the strength of the sintered body, the amount of C remaining in the sintered body is controlled, that is, the amount of C that reacts with oxygen in the alloy steel powder is determined in advance. It is extremely important to do. In response to this problem, the inventors have determined that the amount of graphite used for the reduction of oxygen in the alloy steel powder during sintering depends mainly on the amount of Cr in the alloy steel powder, the amount of Mn, and the oxidation rates of these elements. Therefore, it has been found that the amount of C remaining in the sintered body can be controlled by additionally adding graphite in an amount determined by the amount of Cr in the alloy steel powder, the amount of Mn, and the oxidation rate of these elements. It was.

具体的には、合金鋼粉中のＣｒ量［％Ｃｒ］およびＭｎ量［％Mｎ］と、合金鋼粉中のＣｒの酸化率αおよびＭｎの酸化率βを予め求めておき、焼結体中に残留させるＣ量［％Ｃ］に対して、下記（1）式により黒鉛粉末の添加量［％Ｇｒ］（粉末冶金用合金鋼粉の質量に対する質量％）を求め、合金鋼粉に黒鉛粉末を添加することにより、焼結体中のＣ量を容易に所望の量に制御できる。したがって、本発明では、粉末冶金用合金鋼粉に、下記（1）式の条件を満足する量［％Ｇｒ］（粉末冶金用合金鋼粉の質量に対する質量％）の黒鉛粉末を添加することが好ましい。
［％Ｇｒ］＝ｔ×（α×０．４６×［％Ｃｒ］＋β×０．２９×［％Ｍｎ］）＋γ＋［％Ｃ］ …（1）
但し ［％Ｃｒ］：粉末冶金用合金鋼粉中のＣｒ量（質量％）
［％Ｍｎ］：粉末冶金用合金鋼粉中のＭｎ量（質量％）
［％Ｃ］：黒鉛粉末のなかで、焼結体中に残留させるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）
α：粉末冶金用合金鋼粉中のＣｒの酸化率
β：粉末冶金用合金鋼粉中のＭｎの酸化率
γ：黒鉛粉末のなかで、粉末冶金用合金鋼粉に吸着されている酸素分および焼結雰囲気中に含まれる酸素分との反応に消費されるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）。但し、γ≦０．２質量％
ｔ：０．２５〜０．７５ Specifically, the Cr amount [% Cr] and Mn amount [% Mn] in the alloy steel powder, the Cr oxidation rate α and the Mn oxidation rate β in the alloy steel powder are obtained in advance, and the sintered body The amount of graphite powder added [% Gr] (mass% with respect to the mass of the alloy steel powder for powder metallurgy) is obtained from the following formula (1) with respect to the amount of C [% C] remaining in the graphite, By adding the powder, the amount of C in the sintered body can be easily controlled to a desired amount. Therefore, in the present invention, graphite powder in an amount [% Gr] (mass% with respect to the mass of the alloy steel powder for powder metallurgy) satisfying the condition of the following formula (1) may be added to the alloy steel powder for powder metallurgy. preferable.
[% Gr] = t × (α × 0.46 × [% Cr] + β × 0.29 × [% Mn]) + γ + [% C] (1)
However, [% Cr]: Cr content (% by mass) in alloy steel powder for powder metallurgy
[% Mn]: Mn content (% by mass) in alloy steel powder for powder metallurgy
[% C]: amount of C remaining in the sintered body in the graphite powder (mass% with respect to the mass of the alloy steel powder for powder metallurgy)
α: oxidation rate of Cr in alloy steel powder for powder metallurgy β: oxidation rate of Mn in alloy steel powder for powder metallurgy γ: oxygen content adsorbed by alloy steel powder for powder metallurgy in graphite powder and C amount (mass% with respect to the mass of the alloy steel powder for powder metallurgy) consumed in the reaction with oxygen contained in the sintering atmosphere. However, γ ≦ 0.2 mass%
t: 0.25 to 0.75

上記（1）式において、α×０．４６×［％Ｃｒ］は、合金鋼粉中に含有されるＣｒと結合する酸素を還元するために必要なＣ量であり、また、β×０．２９×［％Ｍｎ］は、合金鋼粉中に含有されるＭｎと結合する酸素を還元するために必要なＣ量であり、易酸化元素であるＣｒやＭｎを含有する合金鋼粉に固有のものである。すなわち、０．４６は２Ｃｒ＋３Ｏ＝Ｃｒ２Ｏ３の関係よりＣｒ：５２（原子量），Ｏ：１６（原子量）で計算した係数、０．２９はＭｎ＋Ｏ＝ＭｎＯの関係よりＭｎ：５５（原子量），Ｏ：１６（原子量）で計算した係数である。
また、上記（1）式において、係数ｔの上限：０．７５は、合金鋼粉中のＣｒおよびＭｎと結合する酸素の全量が還元されるとした場合について、ＯとＣがＣ＋Ｏ＝ＣＯで反応するとして考え、ＣとＯの質量比（１２：１６＝０．７５：１）から計算した値である。一方、合金鋼粉中のＣｒおよびＭｎと結合する酸素は、必ずその全量が還元されるとは限らず、焼結条件等によって、一部の酸素が還元されない場合もあり得るので、還元されずに残存する酸素の量を考慮して係数ｔの下限を０．２５とした。 In the above formula (1), α × 0.46 × [% Cr] is the amount of C necessary for reducing oxygen combined with Cr contained in the alloy steel powder, and β × 0. 29 × [% Mn] is the amount of C necessary for reducing oxygen combined with Mn contained in the alloy steel powder, and is specific to the alloy steel powder containing Cr and Mn, which are oxidizable elements. Is. That is, 0.46 of Cr than the relationship 2Cr + 3O = Cr 2 O 3 : 52 ( atomic weight), O: 16 Factor calculated in (atomic weight), 0.29 Mn than relationship Mn + O = MnO: 55 (atomic weight) O: A coefficient calculated by 16 (atomic weight).
Further, in the above formula (1), the upper limit of the coefficient t: 0.75 is that when the total amount of oxygen combined with Cr and Mn in the alloy steel powder is reduced, O and C are C + O = CO. It is a value calculated from the mass ratio of C and O (12: 16 = 0.75: 1). On the other hand, the oxygen combined with Cr and Mn in the alloy steel powder is not necessarily reduced in its entirety, and some oxygen may not be reduced depending on the sintering conditions, etc., so it is not reduced. The lower limit of the coefficient t was set to 0.25 in consideration of the amount of remaining oxygen.

また、酸化率α＝［粉末冶金用合金鋼粉中に酸化物として含まれるＣｒ量］／［粉末冶金用合金鋼粉中のＣｒ量］、酸化率β＝［粉末冶金用合金鋼粉中に酸化物として含まれるＭｎ量］／［粉末冶金用合金鋼粉中のＭｎ量］である。酸化物として含まれるＣｒ量、Ｍｎ量は、粉末冶金用合金鋼粉を臭素または沃素などをアルコールに溶解したハロゲン−アルコール溶液に溶解して、その抽出残渣中の金属分を原子吸光法で分析することにより測定することができる。なお、使用する合金鋼粉の酸化率α，βに特別な制限はないが、（α×０．４６×［％Ｃｒ］＋β×０．２９×［％Ｍｎ］）の値を０．０５質量％未満とするためには、非常に清浄な還元雰囲気または減圧雰囲気が必要になり、コストが増大するので、（α×０．４６×［％Ｃｒ］＋β×０．２９×［％Ｍｎ］）の値が０．０５質量％以上となるような酸化率α，βであることが好ましい。   Also, the oxidation rate α = [the amount of Cr contained in the alloy steel powder for powder metallurgy as an oxide] / [the amount of Cr in the alloy steel powder for powder metallurgy], the oxidation rate β = [in the alloy steel powder for powder metallurgy Mn amount contained as oxide] / [Mn amount in alloy steel powder for powder metallurgy]. The amount of Cr and Mn contained as oxides is determined by dissolving alloy steel powder for powder metallurgy in a halogen-alcohol solution in which bromine or iodine is dissolved in alcohol and analyzing the metal content in the extraction residue by atomic absorption spectrometry. Can be measured. The oxidation rate α, β of the alloy steel powder used is not particularly limited, but the value of (α × 0.46 × [% Cr] + β × 0.29 × [% Mn]) is 0.05 mass. In order to make it less than%, a very clean reducing atmosphere or reduced-pressure atmosphere is required, and the cost increases, so (α × 0.46 × [% Cr] + β × 0.29 × [% Mn]) It is preferable that the oxidation rates α and β are such that the value of is 0.05% by mass or more.

また、γは、添加された黒鉛粉末のなかで、粉末冶金用合金鋼粉の粒子表面に吸着されている酸素分（酸素含有ガス、水分の形態で吸着されている酸素分）および焼結雰囲気に含まれる酸素分（酸素含有ガス、水分として含まれる酸素分）との反応で消費されるＣ量である。γの値は経験則に基づき決めてもよいし、通常の純鉄粉を類似の成形・焼結条件で処理した場合のＣ消費量を調べ、このＣ消費量をγとしてもよい。但し、γは０．２質量％以下とする。γが０．２質量％を超えると、不必要に炭素を消費する条件で焼結体を製造している可能性が高い。一方、γを０．０１質量％未満とするには、焼結に到る全工程で厳しい酸化管理が必要となり、製造コストにも影響するので、一般にはγは０．０１質量％以上であることが好ましい。   In addition, γ is the oxygen content adsorbed on the particle surface of the alloy steel powder for powder metallurgy (oxygen-containing gas, oxygen content adsorbed in the form of moisture) and sintering atmosphere in the added graphite powder. Is the amount of C consumed in the reaction with the oxygen content (oxygen-containing gas, oxygen content contained as moisture). The value of γ may be determined based on empirical rules, or C consumption when normal pure iron powder is processed under similar molding and sintering conditions may be examined, and this C consumption may be set as γ. However, γ is 0.2% by mass or less. When γ exceeds 0.2% by mass, there is a high possibility that a sintered body is manufactured under the condition that carbon is unnecessarily consumed. On the other hand, in order to make γ less than 0.01% by mass, strict oxidation control is required in all processes leading to sintering, which also affects the manufacturing cost. Therefore, γ is generally 0.01% by mass or more. It is preferable.

以下、加圧成形および焼結される「合金鋼粉または合金鋼粉を含む混合粉」のことを、説明の便宜上「原料粉末」と呼ぶ。
原料粉末の加圧成形では、使用する装置の構成などに特別な制限はないが、７００ＭＰａ以上の圧力で成形を行う必要がある。成形圧力が７００ＭＰａ未満では、十分な強度の焼結体が得られない。また、焼結後に浸炭焼入れ処理（通常、浸炭性ガス雰囲気中で加熱して焼結体にＣを固溶（浸炭）させた後、油中に焼入れする処理）を行う場合に、成形圧力が７００ＭＰａ未満では、得られる成形体の密度が十分でなく、浸炭性ガス雰囲気中に含まれる酸素により粒界酸化（浸炭性ガス雰囲気中に含有される酸素と、焼結体中の易酸化元素であるＣｒ，Ｍｎが結合することにより生じる粒界酸化）が生じて焼結体（熱処理体）強度が低下する。これに対して、７００ＭＰａ以上の成形圧力で成形を行うと、十分な密度の成形体が得られるため、焼結後に浸炭焼入れ処理する場合であっても粒界酸化が生じ難く、十分な強度の熱処理体を得ることができる。
また、加圧成形は、室温（約２０℃）〜１６０℃の温度で行なうことが好ましい。例えば、金型の温度を５０〜７０℃に維持しつつ、室温の原料粉末を充填して加圧成形すれば、良好な圧縮性が得られる。また、金型と原料粉末を１２０〜１３０℃に加熱して加圧成形する技術（いわゆる温間成形）も適用できる。 Hereinafter, “alloyed steel powder or mixed powder containing alloyed steel powder” that is pressed and sintered is referred to as “raw material powder” for convenience of explanation.
In the pressure molding of the raw material powder, there is no particular limitation on the configuration of the apparatus to be used, but it is necessary to perform the molding at a pressure of 700 MPa or more. When the molding pressure is less than 700 MPa, a sintered body with sufficient strength cannot be obtained. In addition, when performing carburizing and quenching after sintering (usually heating in a carburizing gas atmosphere to dissolve C (carburized) in the sintered body and then quenching in oil), the molding pressure is reduced. If it is less than 700 MPa, the density of the obtained molded body is not sufficient, and it is a grain boundary oxidation by oxygen contained in the carburizing gas atmosphere (the oxygen contained in the carburizing gas atmosphere and the oxidizable element in the sintered body). Grain boundary oxidation caused by bonding of certain Cr and Mn occurs, and the strength of the sintered body (heat treated body) decreases. On the other hand, when molding is performed at a molding pressure of 700 MPa or more, a molded body having a sufficient density is obtained. Therefore, even when carburizing and quenching is performed after sintering, grain boundary oxidation hardly occurs, and sufficient strength is obtained. A heat-treated body can be obtained.
The pressure molding is preferably performed at a temperature of room temperature (about 20 ° C.) to 160 ° C. For example, good compressibility can be obtained by filling the raw material powder at room temperature and performing pressure molding while maintaining the temperature of the mold at 50 to 70 ° C. Moreover, the technique (what is called warm molding) which heats a metal mold | die and raw material powder to 120-130 degreeC, and is pressure-molded is also applicable.

上記加圧成形後の焼結は、１１５０〜１３００℃の温度で行う必要がある。焼結温度が１１５０℃未満では、上記の還元反応が不十分となり、粉末粒子の結合が不十分であるため、十分な強度の焼結体が得られない。一方、焼結温度が１３００℃を超えると結晶粒の粗大化が生じ、却って強度が低下してしまう。また、製造コストの観点からは、焼結温度は１１５０〜１２００℃が特に好ましい。
また、このような焼結温度による焼結時間は、焼結性および製造コストの観点から２０〜１２０分程度が好ましい。 Sintering after the pressure molding needs to be performed at a temperature of 1150 to 1300 ° C. If the sintering temperature is less than 1150 ° C., the above reduction reaction is insufficient, and the powder particles are not sufficiently bonded, so that a sintered body having sufficient strength cannot be obtained. On the other hand, when the sintering temperature exceeds 1300 ° C., the crystal grains become coarse and the strength is lowered. Further, from the viewpoint of manufacturing cost, the sintering temperature is particularly preferably 1150 to 1200 ° C.
In addition, the sintering time at such a sintering temperature is preferably about 20 to 120 minutes from the viewpoint of sinterability and manufacturing cost.

また、焼結を行う雰囲気には、還元ガス、不活性ガス、炭化水素変性ガス（いわゆるＲＸガス）等を使用する。また、雰囲気を真空にしてもよい。本発明で使用する合金鋼粉は、酸化され易い元素であるＣｒ、Ｍｏの配合量を少なくしたので、ＲＸガス雰囲気で焼結しても粒界酸化が抑制され、自動車用高強度焼結部品等として十分な特性が得られる。
使用する焼結設備などに特別な制限はないが、焼結コスト削減の観点からは、大量生産が可能なメッシュベルト炉やプッシャー炉を使用することが好ましい。
なお、得られる焼結体の酸素含有量に特別な制限はないが、一般には、０．１質量％以下が好ましく、０．０５質量％以下がさらに好ましい。また、焼結体Ｃ量にも特別な制限はないが、一般に０．１〜０．９質量％程度である。 In addition, a reducing gas, an inert gas, a hydrocarbon-modified gas (so-called RX gas), or the like is used as an atmosphere for sintering. The atmosphere may be a vacuum. The alloy steel powder used in the present invention reduces the compounding amount of Cr and Mo, which are easily oxidizable elements, so that grain boundary oxidation is suppressed even when sintered in an RX gas atmosphere, and high strength sintered parts for automobiles. As a result, sufficient characteristics can be obtained.
Although there is no special restriction | limiting in the sintering equipment to be used, From a viewpoint of sintering cost reduction, it is preferable to use the mesh belt furnace and pusher furnace which can be mass-produced.
In addition, although there is no special restriction | limiting in oxygen content of the sintered compact obtained, generally 0.1 mass% or less is preferable and 0.05 mass% or less is further more preferable. Further, the amount of the sintered body C is not particularly limited, but is generally about 0.1 to 0.9% by mass.

以上のようにして得られた焼結体は、焼結したままでも自動車用高強度焼結部品として使用できる。但し、必要に応じて浸炭焼入れ（いわゆるＣＱＴ）、光輝焼入れ（いわゆるＢＱＴ）、高周波焼入れ、浸炭窒化熱処理等の熱処理を施してもよい。浸炭焼入れ、光輝焼入れ、高周波焼入れを施す場合は、さらに焼戻しを行なうことが好ましい。これらの熱処理を行なうことによって、自動車用高強度焼結部品としての特性がさらに向上する。なお、これらの熱処理では、操業条件や使用する装置の構成に特別な制限はなく、従来公知の技術を適用すればよい。   The sintered body obtained as described above can be used as a high-strength sintered part for automobiles even when it is sintered. However, heat treatment such as carburizing quenching (so-called CQT), bright quenching (so-called BQT), induction quenching, and carbonitriding heat treatment may be performed as necessary. When carburizing quenching, bright quenching, and induction quenching are performed, it is preferable to further perform tempering. By performing these heat treatments, the characteristics as a high-strength sintered part for automobiles are further improved. In these heat treatments, there are no particular restrictions on the operating conditions and the configuration of the apparatus used, and conventionally known techniques may be applied.

［実施例１］
表１に示す組成の合金鋼粉に、焼結後のＣ量（焼結体Ｃ量）が０．３質量％となる量の黒鉛粉末を添加し、混合した原料粉末を用いた。この原料粉末を成形圧力７００ＭＰａで底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において１２００℃で焼結した。この角柱状焼結体に浸炭焼入れ焼戻しを施した後、引張強さと衝撃値を測定するとともに、金属組織を観察した。また、浸炭焼入れ焼戻し前の焼結体について、Ｃ分析を行った。それらの結果を表１に併せて示す。 [Example 1]
The alloy powder having the composition shown in Table 1 was added with graphite powder in such an amount that the amount of C after sintering (the amount of sintered body C) was 0.3% by mass, and mixed raw material powder was used. This raw material powder was molded into a prismatic molded body having a molding pressure of 700 MPa and a bottom surface of 10 mm × 60 mm, and sintered at 1200 ° C. in a nitrogen gas atmosphere. After subjecting this prismatic sintered body to carburizing, quenching and tempering, the tensile strength and impact value were measured, and the metal structure was observed. Moreover, C analysis was performed about the sintered compact before carburizing quenching tempering. The results are also shown in Table 1.

表１において、合金鋼粉のＣｒ量が少ない試料番号１（比較例）は、生成するマルテンサイト量が少ないため焼結体の引張強さは低い。一方、Ｃｒ量が多すぎる試料番号４（比較例）は、粒界酸化が生じるため、この場合も焼結体の引張強さは低い。これに対して、本発明例である試料番号２，３は、十分な焼入れ性が確保されるため、焼結体は１０００ＭＰａ以上の高い引張強さが得られている。
また、合金鋼粉のＭｎ量が少ない試料番号５（比較例）は、生成するマルテンサイト量が少ないため焼結体の引張強さは低い。一方、Ｍｎ量が多すぎる試料番号８（比較例）は、粒界酸化が生じるため、この場合も焼結体の引張強さは低い。これに対して、本発明例である試料番号６，７は、十分な焼入れ性が確保されるため、焼結体は１０００ＭＰａ以上の高い引張強さが得られている。 In Table 1, Sample No. 1 (Comparative Example) with a small amount of Cr in the alloy steel powder has a low tensile strength of the sintered body because the amount of martensite produced is small. On the other hand, Sample No. 4 (Comparative Example) with too much Cr content causes grain boundary oxidation, so that the tensile strength of the sintered body is also low in this case. On the other hand, Sample Nos. 2 and 3, which are examples of the present invention, ensure a sufficient hardenability, so that the sintered body has a high tensile strength of 1000 MPa or more.
Moreover, sample number 5 (comparative example) with a small amount of Mn in the alloy steel powder has a low tensile strength of the sintered body because the amount of martensite produced is small. On the other hand, Sample No. 8 (Comparative Example) having an excessive amount of Mn causes grain boundary oxidation, and in this case, the tensile strength of the sintered body is low. On the other hand, Sample Nos. 6 and 7, which are examples of the present invention, ensure a sufficient hardenability, so that the sintered body has a high tensile strength of 1000 MPa or more.

また、合金鋼粉のＭｏ量が少ない試料番号９（比較例）は、生成するマルテンサイト量が少ないため焼結体の引張強さは低い。一方、Ｍｎ量が多すぎる試料番号１２（比較例）は、原料粉体の圧縮性が低下するため、この場合も焼結体の引張強さは低い。これに対して、本発明例である試料番号１０，１１は、十分な焼入れ性が確保されるため、焼結体は１０００ＭＰａ以上の高い引張強さが得られている。
また、合金鋼粉のＯ量が多すぎる試料番号１６（比較例）は、原料粉体の圧縮性が低下するため焼結体の引張強さは低い。これに対して、本発明例である試料番号１３〜１５の焼結体は１０００ＭＰａ以上の高い引張強さが得られている。 Sample No. 9 (comparative example) with a small amount of Mo in the alloy steel powder has a low tensile strength of the sintered body because the amount of martensite produced is small. On the other hand, Sample No. 12 (Comparative Example) having an excessive amount of Mn has a low compressive strength of the raw material powder, so that the tensile strength of the sintered body is also low in this case. On the other hand, Sample Nos. 10 and 11, which are examples of the present invention, have sufficient hardenability, so that the sintered body has a high tensile strength of 1000 MPa or more.
Further, Sample No. 16 (Comparative Example) in which the amount of O of the alloy steel powder is too large has a low tensile strength of the sintered body because the compressibility of the raw material powder decreases. On the other hand, high tensile strength of 1000 MPa or more is obtained in the sintered bodies of sample numbers 13 to 15 which are examples of the present invention.

Figure 0005389577
Figure 0005389577

［実施例２］
実施例１（表１）の試料番号２で用いた合金鋼粉（Ｃｒ：０．３質量％、Ｍｎ：０．３質量％、Ｍｏ：０．２質量％、Ｃ：０．００４質量％、Ｏ量：０．３質量％、残部がＦｅおよび不可避不純物）に、焼結後のＣ量（焼結体Ｃ量）が０．３質量％となる量の黒鉛粉末と成形潤滑剤（ステアリン酸亜鉛）を添加し、混合した原料粉末を用いた。この原料粉末を底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において焼結した。この角柱状焼結体に浸炭焼入れ焼戻しを施した後、引張強さと密度を測定した。この結果を、成形圧力および焼結温度とともに表２に示す。また図１に、試料番号２，５〜７の成形圧力と引張強さとの関係を、既存高強度材である試料番号８〜１１のそれと比較して示す。 [Example 2]
Alloy steel powder used in sample number 2 of Example 1 (Table 1) (Cr: 0.3% by mass, Mn: 0.3% by mass, Mo: 0.2% by mass, C: 0.004% by mass, O amount: 0.3% by mass, the balance being Fe and inevitable impurities), graphite powder and molding lubricant (stearic acid) in which the amount of C after sintering (sintered body C amount) is 0.3% by mass Zinc) was added and mixed raw material powder was used. This raw material powder was formed into a prismatic shaped body having a bottom surface of 10 mm × 60 mm and sintered in a nitrogen gas atmosphere. After subjecting this prismatic sintered body to carburizing, quenching and tempering, tensile strength and density were measured. The results are shown in Table 2 together with the molding pressure and sintering temperature. FIG. 1 shows the relationship between the molding pressure and tensile strength of sample numbers 2 to 7 in comparison with that of sample numbers 8 to 11 which are existing high strength materials.

表２において、焼結温度が低すぎる試料番号１（比較例）は、合金鋼粉の粒子の結合が不十分であり、さらに浸炭焼入れ時に粒界酸化が生じるため、焼結体の引張強さは低い。一方、焼結温度が高すぎる試料番号４（比較例）は、結晶粒の粗大化が生じ、この場合も焼結体の引張強さは低い。また、図１に示すように、加圧成形時の圧力が低すぎる試料番号５，６（比較例）は、密度が低いために浸炭焼入れ時に粒界酸化が生じ、既存の高強度材（試料番号８〜１１）よりも引張強さが著しく低い。これに対して、本発明例である試料番号２，３，７の焼結体は１０００ＭＰａ以上の高い引張強さが得られている。   In Table 2, since the sintering temperature of sample number 1 (comparative example) is too low, the bonding of alloy steel powder particles is insufficient, and further, grain boundary oxidation occurs during carburizing and quenching, so the tensile strength of the sintered body Is low. On the other hand, Sample No. 4 (Comparative Example) whose sintering temperature is too high causes coarsening of crystal grains, and in this case, the tensile strength of the sintered body is low. Further, as shown in FIG. 1, Sample Nos. 5 and 6 (Comparative Example) in which the pressure during pressure molding is too low cause grain boundary oxidation during carburizing and quenching due to the low density, and the existing high strength material (Sample The tensile strength is significantly lower than the numbers 8-11). In contrast, the sintered bodies of sample numbers 2, 3, and 7 as examples of the present invention have a high tensile strength of 1000 MPa or more.

Figure 0005389577
Figure 0005389577

［実施例３］
表３に示す組成の合金鋼粉に黒鉛粉末を添加し、混合した原料粉末を用いた。この原料粉末を成形圧力７００ＭＰａで底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において１２００℃で焼結した。この角柱状焼結体の引張強さを測定するとともに、Ｃ分析を行った。それらの結果を表３に併せて示す。
表３において、試料番号１〜４は黒鉛粉末の添加量を０．６０質量％で一定としているため、合金鋼粉中の酸素量の増加とともに脱炭量が増加し、焼結体のＣ量にバラツキが生じ、引張強度が大きく変動している。一方、試料番号５〜７は、焼結時に酸素と反応する量を考慮して黒鉛粉末を添加しているため、焼結体のＣ量と引張強度に実質的なバラツキは生じていない。 [Example 3]
A raw material powder obtained by adding graphite powder to alloy steel powder having the composition shown in Table 3 and mixing it was used. This raw material powder was molded into a prismatic molded body having a molding pressure of 700 MPa and a bottom surface of 10 mm × 60 mm, and sintered at 1200 ° C. in a nitrogen gas atmosphere. While measuring the tensile strength of this prismatic sintered body, C analysis was performed. The results are also shown in Table 3.
In Table 3, since the sample numbers 1 to 4 have a constant graphite powder addition amount of 0.60% by mass, the amount of decarburization increases as the amount of oxygen in the alloy steel powder increases, and the amount of C in the sintered body The tensile strength varies greatly. On the other hand, in Sample Nos. 5 to 7, since graphite powder is added in consideration of the amount that reacts with oxygen during sintering, there is no substantial variation in the C content and tensile strength of the sintered body.

Figure 0005389577
Figure 0005389577

［実施例４］
表４に示す組成の合金鋼粉に、焼結後のＣ量（焼結体Ｃ量）が０．４質量％となるように、上記（1）式（ｔ＝０．７５、γ＝０．１質量％）により求めた量の黒鉛粉末を添加し、混合した原料粉末を用いた。この原料粉末を成形圧力７００ＭＰａで底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において１２００℃で焼結した。この角柱状焼結体に浸炭焼入れ焼戻しを施した後、引張強さと衝撃値を測定するとともに、金属組織を観察した。また、浸炭焼入れ焼戻し前の焼結体について、Ｃ分析を行った。それらの結果を表４に併せて示す。
なお、表４によれば、いずれの焼結体（但し、Ｎｏ．１６の焼結体は除く）もＣ分析で測定されたＣ量はほぼ０．４０質量％であり、上記（1）式により、目標とする焼結体中のＣ量に対し、黒鉛粉末の添加量を正確に求めることが可能であることが判った。なお、合金鋼粉中の酸素含有量が多いＮｏ．１６は、焼結体Ｃ量が目標値（０．４０質量％）から大幅に逸脱したが、これはγが（1）式の設定値：０．１質量％よりも相当に逸脱したためであると考えられる。 [Example 4]
In the alloy steel powder having the composition shown in Table 4, the above formula (1) (t = 0.75, γ = 0) so that the C amount after sintering (sintered body C amount) is 0.4 mass%. The amount of graphite powder obtained by (1% by mass) was added, and the mixed raw material powder was used. This raw material powder was molded into a prismatic molded body having a molding pressure of 700 MPa and a bottom surface of 10 mm × 60 mm, and sintered at 1200 ° C. in a nitrogen gas atmosphere. After subjecting this prismatic sintered body to carburizing, quenching and tempering, the tensile strength and impact value were measured, and the metal structure was observed. Moreover, C analysis was performed about the sintered compact before carburizing quenching tempering. The results are also shown in Table 4.
According to Table 4, the amount of C measured by C analysis in any sintered body (excluding the sintered body of No. 16) is approximately 0.40% by mass, and the above formula (1) Thus, it was found that the amount of graphite powder added can be accurately determined with respect to the target amount of C in the sintered body. In addition, No. with much oxygen content in alloy steel powder. In No. 16, the amount of sintered body C deviated significantly from the target value (0.40% by mass) because γ deviated considerably from the set value of equation (1): 0.1% by mass. it is conceivable that.

Figure 0005389577
Figure 0005389577

［実施例５］
表５に示す組成の合金鋼粉に黒鉛粉末を添加し、混合した原料粉末を用いた。この原料粉末を成形圧力７００ＭＰａで底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において１２００℃で焼結した。この角柱状焼結体の引張強さを測定するとともに、Ｃ分析を行った。それらの結果を表５に併せて示す。
表５において、試料番号１〜４は黒鉛粉末の添加量を０．６０質量％で一定としたものである。これらは、合金鋼粉中の酸素量の増加とともに脱炭量が増加し、焼結体のＣ量にバラツキが生じ、引張強度が大きく変動している。一方、試料番号５〜７は、焼結時に酸素と反応するＣ量を考慮して、上記（1）式（ｔ＝０．７５、γ＝０．１質量％）により求めた量の黒鉛粉末を添加したものである。これらは、焼結体のＣ量と引張強度に実質的なバラツキは生じていない。 [Example 5]
A raw material powder obtained by adding graphite powder to alloy steel powder having the composition shown in Table 5 and mixing it was used. This raw material powder was molded into a prismatic molded body having a molding pressure of 700 MPa and a bottom surface of 10 mm × 60 mm, and sintered at 1200 ° C. in a nitrogen gas atmosphere. While measuring the tensile strength of this prismatic sintered body, C analysis was performed. The results are also shown in Table 5.
In Table 5, Sample Nos. 1-4 are those in which the amount of graphite powder added is constant at 0.60% by mass. In these, as the amount of oxygen in the alloy steel powder increases, the amount of decarburization increases, the amount of C in the sintered body varies, and the tensile strength varies greatly. On the other hand, Sample Nos. 5 to 7 are graphite powders in an amount obtained by the above formula (1) (t = 0.75, γ = 0.1% by mass) in consideration of the amount of C that reacts with oxygen during sintering. Is added. These have no substantial variation in the amount of C and the tensile strength of the sintered body.

Figure 0005389577
Figure 0005389577

［実施例６］
表６に示す組成の合金鋼粉に黒鉛粉末を添加し、混合した原料粉末を用いた。この原料粉末を成形圧力７００ＭＰａで底面が１０ｍｍ×６０ｍｍの角柱状成形体に成形し、窒素ガス雰囲気中において１１５０℃で焼結した。この角柱状焼結体の引張強さを測定するとともに、Ｃ分析を行った。それらの結果を表６に併せて示す。
表６において、試料番号１〜３は、焼結時に酸素と反応するＣ量を考慮して、焼結体Ｃ量が０．５質量％となるように、上記（1）式（ｔ＝０．５、γ＝０．１質量％）により求めた量の黒鉛粉末を添加したものである。これらは、焼結体のＣ量と引張強度に実質的なバラツキは生じていない。 [Example 6]
A raw material powder obtained by adding graphite powder to alloy steel powder having the composition shown in Table 6 and mixing it was used. This raw material powder was molded into a prismatic molded body having a molding pressure of 700 MPa and a bottom surface of 10 mm × 60 mm, and sintered at 1150 ° C. in a nitrogen gas atmosphere. While measuring the tensile strength of this prismatic sintered body, C analysis was performed. The results are also shown in Table 6.
In Table 6, Sample Nos. 1 to 3 take into account the amount of C that reacts with oxygen during sintering, so that the amount of sintered body C is 0.5% by mass (1) above (t = 0) .5, γ = 0.1% by mass) of graphite powder was added. These have no substantial variation in the amount of C and the tensile strength of the sintered body.

Figure 0005389577
Figure 0005389577

Claims (4)

Ｃｒ：０．３〜０．７質量％、Ｍｎ：０．１〜０．５質量％、Ｍｏ：０．１〜０．５質量％、Ｏ：０．２５〜０．５質量％を含有し、残部がＦｅおよび不可避的不純物からなる粉末冶金用合金鋼粉を用い、該粉末冶金用合金鋼粉またはこれを含む混合粉を７００ＭＰａ以上の圧力で成形した後、１１５０〜１３００℃の温度で焼結することを特徴とする粉末冶金法による焼結体の製造方法。   Cr: 0.3-0.7% by mass, Mn: 0.1-0.5% by mass, Mo: 0.1-0.5% by mass, O: 0.25-0.5% by mass Then, using the alloy steel powder for powder metallurgy consisting of Fe and the inevitable impurities as the balance, the alloy steel powder for powder metallurgy or the mixed powder containing this is formed at a pressure of 700 MPa or more and then sintered at a temperature of 1150 to 1300 ° C A method for producing a sintered body by powder metallurgy, characterized by: 混合粉が黒鉛粉末を含むことを特徴とする請求項１に記載の粉末冶金法による焼結体の製造方法。   The method for producing a sintered body by a powder metallurgy method according to claim 1, wherein the mixed powder contains graphite powder. 混合粉が、焼結体中に残留させるＣ量と、焼結時に粉末冶金用合金鋼粉中の酸素と反応するＣ量の合計に相当する量の黒鉛粉末を含むことを特徴とする請求項１または２に記載の粉末冶金法による焼結体の製造方法。   The mixed powder contains graphite powder in an amount corresponding to the total amount of C remaining in the sintered body and the amount of C that reacts with oxygen in powder metallurgy alloy steel powder during sintering. A method for producing a sintered body by the powder metallurgy method according to 1 or 2. 粉末冶金用合金鋼粉に、下記（1）式の条件を満足する量［％Ｇｒ］（粉末冶金用合金鋼粉の質量に対する質量％）の黒鉛粉末を添加することを特徴とする請求項２に記載の粉末冶金法による焼結体の製造方法。
［％Ｇｒ］＝ｔ×（α×０．４６×［％Ｃｒ］＋β×０．２９×［％Ｍｎ］）＋γ＋［％Ｃ］ …（1）
但し ［％Ｃｒ］：粉末冶金用合金鋼粉中のＣｒ量（質量％）
［％Ｍｎ］：粉末冶金用合金鋼粉中のＭｎ量（質量％）
［％Ｃ］：黒鉛粉末のなかで、焼結体中に残留させるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）
α：粉末冶金用合金鋼粉中のＣｒの酸化率
β：粉末冶金用合金鋼粉中のＭｎの酸化率
γ：黒鉛粉末のなかで、粉末冶金用合金鋼粉に吸着されている酸素分および焼結雰囲気中に含まれる酸素分との反応に消費されるＣ量（粉末冶金用合金鋼粉の質量に対する質量％）。但し、γ≦０．２質量％
ｔ：０．２５〜０．７５ 3. A graphite powder in an amount [% Gr] (mass% with respect to the mass of the alloy steel powder for powder metallurgy) satisfying the condition of the following formula (1) is added to the alloy steel powder for powder metallurgy: The manufacturing method of the sintered compact by the powder metallurgy method of description.
[% Gr] = t × (α × 0.46 × [% Cr] + β × 0.29 × [% Mn]) + γ + [% C] (1)
However, [% Cr]: Cr content (% by mass) in alloy steel powder for powder metallurgy
[% Mn]: Mn content (% by mass) in alloy steel powder for powder metallurgy
[% C]: amount of C remaining in the sintered body in the graphite powder (mass% with respect to the mass of the alloy steel powder for powder metallurgy)
α: oxidation rate of Cr in alloy steel powder for powder metallurgy β: oxidation rate of Mn in alloy steel powder for powder metallurgy γ: oxygen content adsorbed by alloy steel powder for powder metallurgy in graphite powder and C amount (mass% with respect to the mass of the alloy steel powder for powder metallurgy) consumed in the reaction with oxygen contained in the sintering atmosphere. However, γ ≦ 0.2 mass%
t: 0.25 to 0.75
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20180043821A (en) 2015-09-30 2018-04-30 제이에프이 스틸 가부시키가이샤 METHOD FOR MANUFACTURING ALLOY POWDER FOR POWDER METAL

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012126971A (en) * 2010-12-16 2012-07-05 Jfe Steel Corp Alloy steel powder for powder metallurgy, iron-based sintered material, and method for producing the same
CN104039484B (en) * 2012-01-05 2016-12-07 霍加纳斯股份有限公司 Metal dust and application thereof
CN103008664B (en) * 2012-11-25 2014-07-16 安徽普源分离机械制造有限公司 Preparation method for valve clack of butterfly valve
CN103056369A (en) * 2012-12-31 2013-04-24 上海汽车粉末冶金有限公司 Process for producing part by powder metallurgy
JP6155894B2 (en) * 2013-06-20 2017-07-05 株式会社豊田中央研究所 Iron-based sintered material and method for producing the same
EP3135470A4 (en) * 2014-04-22 2018-04-18 NTN Corporation Sintered mechanical component, device for forming powder compact, and method for forming powder compact
EP3194631B1 (en) * 2014-09-16 2021-06-02 Höganäs AB (publ) A sintered component and a method for making a sintered component
JP6489684B2 (en) * 2015-03-27 2019-03-27 株式会社ダイヤメット Heat-resistant sintered material with excellent oxidation resistance, high-temperature wear resistance, and salt damage resistance, and method for producing the same
KR102383515B1 (en) * 2018-03-26 2022-04-08 제이에프이 스틸 가부시키가이샤 Alloy steel powder for powder metallurgy and iron-based mixed powder for powder metallurgy
US11668298B2 (en) 2018-11-07 2023-06-06 Hyundai Motor Company Slide of variable oil pump for vehicle and method of manufacturing the same

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3687654A (en) * 1971-03-10 1972-08-29 Smith Inland A O Method of making alloy steel powder
JPS61117201A (en) 1984-11-10 1986-06-04 Toyota Motor Corp Low alloy iron powder for sintering
JPS62237518A (en) 1986-04-09 1987-10-17 Hitachi Ltd Data moving system
JPH03122202A (en) * 1989-10-04 1991-05-24 Daido Steel Co Ltd Manufacture of sintered metal product and metal powder for sintering
JPH04254502A (en) * 1991-02-04 1992-09-09 Seiko Electronic Components Ltd Injection-molding composition and production of metallic sintered body
JP3224417B2 (en) 1992-02-14 2001-10-29 川崎製鉄株式会社 Alloy steel powder and sintered body for sintered body having high strength, high fatigue strength and high toughness
CN1104570A (en) * 1993-05-18 1995-07-05 川崎制铁株式会社 Atomised iron powder for powder metallurgy
JPH0827536A (en) * 1994-07-15 1996-01-30 Sumitomo Metal Mining Co Ltd Production of sintered compact of stainless steel
JPH0959740A (en) * 1995-08-22 1997-03-04 Kobe Steel Ltd Powder mixture for powder metallurgy and its sintered compact
US5876481A (en) * 1996-06-14 1999-03-02 Quebec Metal Powders Limited Low alloy steel powders for sinterhardening
CA2372780C (en) * 2001-05-17 2007-02-13 Kawasaki Steel Corporation Iron-based mixed powder for powder metallurgy and iron-based sintered compact
JP2003026840A (en) * 2001-07-12 2003-01-29 Toray Ind Inc Foamed polyolefin resin article
JP2003268401A (en) 2002-03-14 2003-09-25 Toyota Motor Corp Method for manufacturing sintered member
SE0201824D0 (en) 2002-06-14 2002-06-14 Hoeganaes Ab Pre-alloyed iron based powder
US7384445B2 (en) * 2004-04-21 2008-06-10 Höganäs Ab Sintered metal parts and method for the manufacturing thereof
DE112005000921T5 (en) * 2004-04-23 2007-04-19 Kabushiki Kaisha Toyota Chuo Kenkyusho Iron-based sintered alloy, iron-based sintered alloy element and manufacturing method therefor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20180043821A (en) 2015-09-30 2018-04-30 제이에프이 스틸 가부시키가이샤 METHOD FOR MANUFACTURING ALLOY POWDER FOR POWDER METAL

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