JP3491094B2 - Manufacturing method of sintered steel with excellent machinability - Google Patents

Manufacturing method of sintered steel with excellent machinability

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Publication number
JP3491094B2
JP3491094B2 JP08184694A JP8184694A JP3491094B2 JP 3491094 B2 JP3491094 B2 JP 3491094B2 JP 08184694 A JP08184694 A JP 08184694A JP 8184694 A JP8184694 A JP 8184694A JP 3491094 B2 JP3491094 B2 JP 3491094B2
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JP
Japan
Prior art keywords
powder
graphite
particle size
average particle
sintered
Prior art date
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JP08184694A
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Japanese (ja)
Other versions
JPH07286230A (en
Inventor
聡 上ノ薗
邦明 小倉
哲 成谷
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JFE Steel Corp
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JFE Steel Corp
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Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は、粉末冶金用水アトマイ
ズ鋼粉を用いた焼結鋼に係わり、とくに焼結後の切削性
が優れた焼結鋼の製造方法に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered steel using water atomized steel powder for powder metallurgy, and more particularly to a method for producing a sintered steel having excellent machinability after sintering.

【0002】[0002]

【従来の技術】粉末冶金用鉄粉は、鉄粉にCu粉、黒鉛粉
末などを添加混合し、金型中で圧粉成形して焼結し、通
常5.0 〜7.2g/cm3の密度を有する焼結機械部品等の製造
に用いられる。粉末冶金法は寸法精度良く複雑形状の焼
結体を製造できるが、寸法精度の厳しい部品を製造する
場合、焼結後の切削加工、あるいはドリル穴あけ加工が
必要となることがある。
2. Description of the Related Art Iron powder for powder metallurgy is manufactured by adding and mixing Cu powder, graphite powder, etc. to iron powder, compacting and sintering in a mold, and usually obtaining a density of 5.0 to 7.2 g / cm 3 . It is used to manufacture sintered machine parts and other products. The powder metallurgy method can manufacture a sintered body having a complicated shape with high dimensional accuracy, but when manufacturing a component with strict dimensional accuracy, cutting or drilling after sintering may be necessary.

【0003】粉末冶金製品は一般に切削性が劣り、溶製
材製品に比べると工具寿命が短い問題点を有しているた
め機械加工時のコストが高価になる欠点を有している。
粉末冶金製品における切削性の劣化は、粉末冶金製品に
含まれる気孔による断続切削あるいは熱伝導率の低下に
よる切削温度の上昇に起因すると言われている。切削性
の改善を行うためには、S、MnS などの快削成分が鉄粉
に混合されることが多い。これらS、MnS は切りくずの
破断を容易にする効果、あるいは工具にS、MnS の薄い
構成刃先を形成し工具すくい面での潤滑作用により切削
性の向上をもたらすと言われている。特公平3-25481号
公報においては若干のMn(0.1 〜0.5 重量%(以下%と
略す))とSi、Cなどを含む純鉄粉にさらにSを0.03〜
0.07%添加した溶湯を水または気体で噴霧した粉末冶金
用粉末が提案されている。
[0003] Powder metallurgy products generally have inferior machinability and have a problem that tool life is shorter than ingot products, so that the cost during machining is high.
It is said that the deterioration of the machinability of the powder metallurgy product is caused by the intermittent cutting due to the pores contained in the powder metallurgy product or the increase of the cutting temperature due to the decrease of the thermal conductivity. In order to improve the machinability, free-cutting components such as S and MnS are often mixed with iron powder. These S and MnS are said to bring about the effect of facilitating the fracture of chips, or to improve the cutting property by forming a thin S, MnS cutting edge on the tool and lubricating the rake face of the tool. In Japanese Examined Patent Publication No. 3-25481, pure iron powder containing a small amount of Mn (0.1 to 0.5% by weight (hereinafter abbreviated as%)) and Si, C, etc. is further added with 0.03 to S.
A powder for powder metallurgy has been proposed in which a molten metal added with 0.07% is sprayed with water or gas.

【0004】また、特公昭61-40027号公報においては、
焼結鋼中に遊離黒鉛を析出させる方法として、原料粉末
として平均粒径:20 〜350 μm を有する炭素粉末と同じ
く平均粒径:1〜15μmを有し、かつ焼結時に炭素拡散を
抑制する作用を有するSi、SnおよびP の単味粉末、およ
びこれらの成分を15% 以上含有する合金粉末からなる群
のうちの1 種または2 種以上と、平均粒径:40 〜120 μ
m を有するFe基合金粉末のうちいずれか、または両方と
を用意し、これら原料粉末を、炭素粉末:1〜4% 、炭素
拡散抑制作用を有する粉末を炭素拡散抑制成分量で0.2
〜4 % 、Fe粉末およびFe基合金粉末のうちいずれか、ま
たは両方と残りからなる配合組成( 以上重量%)に配合
し、混合して、Fe粉末およびFe基合金粉末のうちいずれ
か、または両方と炭素粉末の表面に炭素拡散抑制作用を
有する粉末を均一にまぶし被覆した状態としてFe素地に
黒鉛を分散させ、以後通常の粉末冶金法にしたがってプ
レス成形し、焼結することを特徴とする遊離黒鉛分散型
鉄系焼結しゅう動材の製造法が開示されている。遊離黒
鉛を析出するために、Si、Sn、およびP などの単味ある
いはその合金粉末を使用するため、コストが高い問題が
ある。またSi、Sn、およびP によって平均粒径20〜350
μm の黒鉛粉末の浸炭を抑制するため、焼結鋼基地は比
較的炭素含有量が低くなるため強度が低い問題があっ
た。
In Japanese Patent Publication No. 61-40027,
As a method of precipitating free graphite in sintered steel, carbon powder having an average particle size of 20 to 350 μm as a raw material powder has an average particle size of 1 to 15 μm and suppresses carbon diffusion during sintering. One or two or more selected from the group consisting of Si, Sn and P plain powders having an action, and alloy powders containing 15% or more of these components, and an average particle size: 40 to 120 μm
Prepare one or both of Fe-based alloy powders having m, and use these raw material powders as carbon powder: 1 to 4%, and a powder having a carbon diffusion suppressing effect in a carbon diffusion suppressing component amount of 0.2.
~ 4%, one of Fe powder and Fe-based alloy powder, or a mixture composition (both by weight% or more) consisting of both and the rest, mixed, and mixed with either Fe powder or Fe-based alloy powder, or Both of them and the surface of the carbon powder are uniformly sprinkled with a powder having a carbon diffusion suppressing effect, and graphite is dispersed in the Fe substrate, and thereafter, the powder is press-molded and sintered according to a usual powder metallurgy method. A method for producing a free graphite-dispersed iron-based sintered sliding material is disclosed. There is a problem that the cost is high because plain or alloy powder thereof such as Si, Sn, and P is used for precipitating free graphite. Also, depending on Si, Sn, and P, the average particle size is 20-350.
In order to suppress the carburization of μm graphite powder, the sintered steel matrix has a relatively low carbon content, which causes a problem of low strength.

【0005】特公平5-63545 号公報にも、自己潤滑性を
有する鉄基焼結部材として、フェライトとパーライトか
らなる基地組織中に鉄酸化物と遊離黒鉛を分散させた焼
結鋼が開示されている。その遊離黒鉛量は0.5 〜3%が好
ましく、基地に固溶させる黒鉛より大きな粒径の黒鉛を
添加することにより遊離黒鉛を生成させるとしている。
Japanese Patent Publication No. 5-63545 also discloses, as an iron-based sintered member having self-lubricating property, a sintered steel in which iron oxide and free graphite are dispersed in a matrix structure composed of ferrite and pearlite. ing. The amount of free graphite is preferably 0.5 to 3%, and it is said that free graphite is generated by adding graphite having a particle size larger than that of the solid solution graphite in the matrix.

【0006】上述の特公昭61-40027号公報と特公平5-63
545 号公報に開示された技術はいずれも鉄基地中に黒鉛
を分散させる技術であるが、その目的は従来からいわれ
ている黒鉛の自己潤滑作用をしゅう動部品に適用するた
めの技術であり、本発明の目的とする切削性の向上に関
する技術ではない。
[0006] Japanese Patent Publication No. 61-40027 and Japanese Patent Publication No. 5-63
All of the techniques disclosed in Japanese Patent No. 545 are techniques for dispersing graphite in an iron base, but the purpose is to apply the conventional self-lubricating action of graphite to sliding parts. It is not a technique relating to improvement of machinability which is an object of the present invention.

【0007】[0007]

【発明が解決しようとする課題】しかしながら、これら
を含めて水を用いた噴霧法により製造されるSを含有す
る粉末冶金用鉄粉を水素を含有する雰囲気中で焼結した
場合、S が除去されて切削性が著しく低下するという問
題があった。本発明は、このような従来技術の欠点に鑑
み、粉末冶金用鉄粉を水素を含有する雰囲気で焼結した
場合にも切削性に優れた焼結鋼の安価な製造方法を提供
することを目的とする。
However, when the S-containing iron powder for powder metallurgy produced by the atomization method using water including them is sintered in an atmosphere containing hydrogen, S is removed. As a result, there is a problem that the machinability is significantly reduced. In view of such drawbacks of the prior art, the present invention provides an inexpensive manufacturing method of sintered steel excellent in machinability even when the iron powder for powder metallurgy is sintered in an atmosphere containing hydrogen. To aim.

【0008】[0008]

【課題を解決するための手段】本発明者らはSを含有す
る水を用いた噴霧法により製造される粉末冶金用鉄粉
を、水素を含有する雰囲気で焼結した場合の切削性低下
の原因について鋭意検討を加えた。Sを0.03〜0.3 %を
含有する粉末冶金用アトマイズ鉄粉を水素を含む窒素雰
囲気中で焼結した場合、純窒素中で焼結した焼結鋼に比
べ、S量と残留黒鉛量が減少していた。またFeS が水素
で還元されると仮定し、焼結鋼中のSの減少量を計算す
ると、分析値とよく一致した。これらの事実から、アト
マイズ鉄粉中あるいは鉄粉表面に存在するFeS が残留黒
鉛の生成に直接かかわることがわかった。また水を用い
た噴霧法により製造されたSを0.03〜0.3 %を含有する
粉末冶金用アトマイズ鉄粉を水素を含む窒素雰囲気中で
焼結途中、急冷し、残留黒鉛の分析を行った結果、残留
黒鉛は焼結中の浸炭が阻害された結果生成することが分
かった。
Means for Solving the Problems The present inventors have found that when the iron powder for powder metallurgy produced by a spraying method using water containing S is sintered in an atmosphere containing hydrogen, the machinability is reduced. The cause was examined thoroughly. When atomized iron powder for powder metallurgy containing 0.03 to 0.3% S is sintered in a nitrogen atmosphere containing hydrogen, the amount of S and the amount of residual graphite are reduced as compared with the sintered steel sintered in pure nitrogen. Was there. Assuming that FeS is reduced by hydrogen, the reduction amount of S in the sintered steel was calculated, and it was in good agreement with the analytical value. From these facts, it was found that FeS existing in atomized iron powder or on the surface of iron powder is directly involved in the formation of residual graphite. Further, the atomized iron powder for powder metallurgy containing 0.03 to 0.3% of S produced by a spraying method using water was rapidly cooled during the sintering in a nitrogen atmosphere containing hydrogen, and the residual graphite was analyzed. It has been found that residual graphite forms as a result of the inhibition of carburization during sintering.

【0009】したがって、このように水素を含む窒素雰
囲気で焼結した場合、粉末に含まれるFeS が水素で還元
され焼結中の浸炭を阻害する作用が無くなった結果、浸
炭が進み焼結鋼表面の残留黒鉛が減少して切削性が低下
することが判明した。粉末冶金により部品を製造する工
場では、部品特性の安定化のため、あるいは易酸化性の
合金元素を含む鋼粉を使用する場合に水素を含有する窒
素雰囲気を用いることが多い。
Therefore, when sintering is performed in a nitrogen atmosphere containing hydrogen as described above, FeS contained in the powder is reduced by hydrogen and the effect of inhibiting carburization during sintering disappears, and as a result, carburization proceeds and the surface of the sintered steel surface is reduced. It was found that the residual graphite of No. 3 decreased and the machinability deteriorated. In a factory where parts are manufactured by powder metallurgy, a nitrogen atmosphere containing hydrogen is often used for stabilizing the characteristics of parts or when using steel powder containing an easily oxidizable alloying element.

【0010】水素を含有する雰囲気で焼結した場合にも
切削性に優れた焼結鋼を製造するためには、焼結中に粉
末に含まれるFeS が水素で還元されないようにするか、
あるいは焼結中の浸炭速度の遅い黒鉛を添加すればよ
い。そこで、後者の観点から種々の黒鉛について検討し
た結果、平均粒径25〜120μm の黒鉛粉末は、焼結中の
浸炭速度が遅くなり、水素を含む焼結雰囲気において
は、焼結鋼中に残留黒鉛として残留し、切削性を向上さ
せることと、平均粒径15μm 以下の黒鉛粉末の浸炭速度
は逆に速いことを発見した。したがって、平均粒径25〜
120 μm の黒鉛粉末と平均粒径15μm 以下の黒鉛粉末と
を併用することにより、焼結体の強度を低下させずに切
削性を向上させ得ることが分かった。また、S を鉄粉中
に共存させると浸炭阻害効果を高めることも分かった。
In order to produce a sintered steel having excellent machinability even when sintered in an atmosphere containing hydrogen, it is necessary to prevent FeS contained in the powder from being reduced by hydrogen during sintering, or
Alternatively, graphite having a slow carburizing rate during sintering may be added. Therefore, as a result of investigating various graphites from the latter point of view, graphite powder with an average particle size of 25 to 120 μm has a slow carburizing rate during sintering, and remains in the sintered steel in a sintering atmosphere containing hydrogen. It was discovered that it remains as graphite to improve the machinability and that the carburizing rate of graphite powder with an average particle size of 15 μm or less is fast. Therefore, the average particle size is 25 ~
It was found that the machinability can be improved without reducing the strength of the sintered body by using the graphite powder of 120 μm and the graphite powder having an average particle size of 15 μm or less. It was also found that the coexistence of S in iron powder enhances the carburizing inhibition effect.

【0011】本発明は、上のような知見に基づくもので
ある。すなわち本発明は、請求項1が純鉄粉あるいは合
金鋼粉を用いて成形・焼結により焼結鋼を得る粉末冶金
法において、粉末冶金用鉄粉に平均粒径25〜120 μmの
黒鉛粉末を0.1 〜1.0 %、平均粒径15μm 以下の黒鉛粉
末0.5 〜2%を混合した混合粉末を成形・焼結すること
を特徴とする切削性に優れた焼結鋼の製造方法であり、
請求項2が純鉄粉あるいは合金鋼粉を用いて成形・焼結
により焼結鋼を得る粉末冶金法において、Mnを0.1 % 未
満とSを0.08〜0.3 %を含有する粉末冶金用アトマイズ
鉄粉に、平均粒径25〜120 μm の黒鉛粉末を0.1 〜1.0
%、平均粒径15μm 以下の黒鉛粉末0.5 〜2%を混合し
た混合粉末を成形・焼結することを特徴とする切削性に
優れた焼結鋼の製造方法である。
The present invention is based on the above findings. That is, according to the present invention, in claim 1, in the powder metallurgy method of obtaining sintered steel by molding and sintering using pure iron powder or alloy steel powder, graphite powder having an average particle size of 25 to 120 μm is added to iron powder for powder metallurgy. Of 0.1 to 1.0% and 0.5 to 2% of graphite powder having an average particle size of 15 μm or less is molded and sintered, which is a method for producing a sintered steel having excellent machinability.
Atomized iron powder for powder metallurgy according to claim 2, which is used in a powder metallurgy method for obtaining a sintered steel by molding and sintering pure iron powder or alloy steel powder, containing less than 0.1% Mn and 0.08 to 0.3% S. , Graphite powder with an average particle size of 25 to 120 μm in an amount of 0.1 to 1.0
%, And 0.5 to 2% of graphite powder having an average particle size of 15 μm or less is mixed and molded and sintered to produce a sintered steel having excellent machinability.

【0012】[0012]

【作 用】本発明によれば、平均粒径25〜120 μm の黒
鉛粉末と平均粒径15μm 以下の黒鉛粉末とを併用するこ
とにより、焼結体の強度を低下させずに焼結鋼の切削性
を向上させることができる。また、鉄粉中にS を共存さ
せると浸炭阻害効果を高めることにより、焼結鋼表層部
に必要残留黒鉛量を確保し、なお一層焼結鋼の切削性を
向上させることができる。
[Operation] According to the present invention, a graphite powder having an average particle diameter of 25 to 120 μm and a graphite powder having an average particle diameter of 15 μm or less are used in combination, so that the strength of the sintered body is not lowered and The machinability can be improved. Further, the coexistence of S 2 in the iron powder enhances the carburizing inhibition effect, so that the required amount of residual graphite can be secured in the surface layer portion of the sintered steel, and the machinability of the sintered steel can be further improved.

【0013】まず、大小2 種類の黒鉛粉末の限定条件に
ついて説明する。添加する黒鉛をすべて平均粒径25〜12
0 μm の黒鉛粉末とすると、浸炭が遅く、焼結鋼基地に
含有されるCが少なく強度が低い。しかし平均粒径15μ
m 以下の黒鉛粉末は焼結中の浸炭速度が速いので、これ
を追加混合して焼結鋼基地に含有するべきC含有量を確
保し強度の低下を防止できる。このように、浸炭速度の
速い平均粒径15μm 以下の黒鉛粉末により焼結鋼基地に
含有されるべきC含有量を確保し強度の低下を防ぎなが
ら、浸炭速度の遅い平均粒径25〜120 μm の黒鉛粉末を
添加することにより残留黒鉛を生成させ切削性の向上が
図ることができる。これは通常の焼結材であるFe-C系あ
るいはFe-Cu-C 系の黒鉛粉末の一部を大粒径黒鉛とする
だけであり、かつ、大粒径黒鉛の価格は通常用いられる
小粒径黒鉛とほとんど変わらないのでコスト面の上昇も
ほとんどない。
First, the limiting conditions for two types of large and small graphite powders will be described. All graphite to be added has an average particle size of 25 to 12
When graphite powder of 0 μm is used, carburization is slow, the amount of C contained in the sintered steel matrix is small, and the strength is low. However, the average particle size is 15μ
Since the graphite powder of m or less has a high carburizing rate during sintering, it can be additionally mixed to secure the C content to be contained in the sintered steel matrix and prevent the strength from decreasing. As described above, graphite powder having a fast carburization rate of 15 μm or less of average particle size secures the C content to be contained in the sintered steel matrix and prevents the strength from decreasing. By adding the graphite powder of No. 1 above, residual graphite is generated and the machinability can be improved. This is because only a part of the graphite powder of Fe-C system or Fe-Cu-C system, which is a normal sintered material, is made into large particle size graphite, and the price of large particle size graphite is small. Since it is almost the same as the particle size graphite, there is almost no increase in cost.

【0014】したがって本発明は、原料粉末冶金用鉄粉
に平均粒径25〜120 μm の黒鉛粉末を0.1 〜1.0 %、平
均粒径15μm 以下の黒鉛粉末0.5 〜2%を含有した混合
粉末を成形焼結することを特徴とする。平均粒径25〜12
0 μm の黒鉛粉末は焼結鋼中の残留黒鉛源として切削性
を向上させるために添加する。平均粒径25μm 未満では
浸炭速度が速すぎるため残留黒鉛が少なく、切削性が悪
い。平均粒径を25μm 以上に限定した理由は、粒径が大
きいほど浸炭速度が遅いことと、切削性を向上させる残
留黒鉛の粒径が大きいほど切削性が向上するからであ
る。平均粒径が120 μm を超えると、均一な混合が進み
にくく焼結鋼中の残留黒鉛の分布が不均一となり、部分
的に切削性が悪くなるため、切削性が低下する。好適な
範囲は50〜100 μm である。
Therefore, according to the present invention, a mixed powder containing 0.1 to 1.0% of graphite powder having an average particle size of 25 to 120 μm and 0.5 to 2% of graphite powder having an average particle size of 15 μm or less is molded into a raw material powder metallurgy iron powder. Characterized by sintering. Average particle size 25-12
Graphite powder of 0 μm is added as a residual graphite source in sintered steel to improve machinability. If the average particle size is less than 25 μm, the carburizing speed is too fast, and the residual graphite is small, resulting in poor machinability. The reason for limiting the average particle size to 25 μm or more is that the larger the particle size is, the slower the carburizing rate is, and the larger the particle size of the residual graphite for improving the machinability is, the more the machinability is improved. If the average particle size exceeds 120 μm, uniform mixing is difficult to proceed, the distribution of residual graphite in the sintered steel becomes uneven, and the machinability partially deteriorates, resulting in a decrease in machinability. The preferred range is 50-100 μm.

【0015】平均粒径25〜120 μm の黒鉛粉末添加量を
0.1 %以上とした理由は、0.1 %未満では残留黒鉛が少
なく切削性が向上しないからである。黒鉛粉末添加量の
上限を1.0 %としたのは焼結体に肌荒れが生ずるからで
ある。好適な添加範囲は0.2〜0.6 % である。平均粒径1
5μm 以下の黒鉛粉末は焼結中に浸炭し、所望の強度を
得るために添加する。浸炭させるための黒鉛粉末は平均
粒径15μm 以下とする必要がある。15μm を超えると浸
炭が遅くなり、希望の強度が得られない。平均粒径15μ
m 以下の黒鉛粉末の添加量を0.5 〜2%に限定した理由
は、0.5 %未満では鋼に含有されるCが少なく強度に劣
り、2%を超えると初析セメンタイトが析出し切削性が
低下するからである。好適な添加範囲は、0.8 〜2.0 %
である。
Add the amount of graphite powder with an average particle size of 25 to 120 μm
The reason why the content is 0.1% or more is that if the content is less than 0.1%, there is little residual graphite and the machinability is not improved. The upper limit of the amount of graphite powder added was set to 1.0% because roughening of the sintered body occurs. The preferable addition range is 0.2 to 0.6%. Average particle size 1
Graphite powder of 5 μm or less is carburized during sintering and added to obtain desired strength. Graphite powder for carburizing must have an average particle size of 15 μm or less. If it exceeds 15 μm, carburization becomes slow and desired strength cannot be obtained. Average particle size 15μ
The reason why the addition amount of graphite powder of m or less is limited to 0.5 to 2% is that if less than 0.5%, the C content in the steel is small and the strength is poor, and if it exceeds 2%, proeutectoid cementite precipitates and the machinability deteriorates. Because it does. The preferred addition range is 0.8-2.0%
Is.

【0016】焼結鋼に残留する残留黒鉛量は0.1 〜0.3
% が好ましい。0.1 % 未満では切削性が悪く、0.3 % を
超えると焼結鋼に肌荒れが生じやすい。上述したような
残留黒鉛の効果を発揮させるためには、粉末冶金用鉄粉
のMnを0.1 % 未満とし、Sを0.08〜0.3 %を含有させる
ことが好ましい。S含有量の好ましい範囲を0.08%から
0.3 %に限定した理由は以下のとおりである。Sを0.08
〜0.3 %を含有する鉄粉のSは、粉末中のFeS 源として
含有され、焼結中の平均粒径25μm 以上の黒鉛粉末によ
る浸炭を一層抑制して焼結鋼中の残留黒鉛をさらに増加
させることにより、切削性を一層向上させる。S 0.08
%未満では、このFeS に基づく浸炭阻止効果がなく、S
を含まない鉄粉に比べ残留黒鉛の増加が少なく切削性の
一層の向上が認められない。Sを 0.3%を超えて含有さ
せると焼結中すすを発生しやすく、焼結炉をいためる恐
れがある。S の好適な範囲は0.1 〜0.2 % である。
The amount of residual graphite remaining in the sintered steel is 0.1 to 0.3.
% Is preferred. If it is less than 0.1%, the machinability is poor, and if it exceeds 0.3%, the sintered steel tends to be rough. In order to exert the effect of residual graphite as described above, it is preferable that the iron powder for powder metallurgy has Mn of less than 0.1% and S of 0.08 to 0.3%. The preferred range of S content is 0.08%
The reason for limiting to 0.3% is as follows. 0.08 for S
S of iron powder containing ~ 0.3% is contained as a FeS source in the powder, and further suppresses carburization by graphite powder with an average particle size of 25 μm or more during sintering to further increase the residual graphite in the sintered steel. By doing so, the machinability is further improved. S 0.08
If it is less than%, there is no carburizing prevention effect based on FeS, and S
Compared with iron powder that does not contain iron, the increase in residual graphite is small and no further improvement in machinability is observed. If S is contained in an amount of more than 0.3%, soot is likely to be generated during sintering and the sintering furnace may be damaged. The preferred range of S is 0.1 to 0.2%.

【0017】水を用いた噴霧法により製造される粉末冶
金用鉄粉のMnは0.1 % 未満が好ましい。Mn0.1 % 以上で
は、粉末中のMnがS と結合しやすいので、粉末中のFeS
が少なくなり、前述したFeS に基づく切削性向上効果が
なく、S を含まない鉄粉に比べ残留黒鉛の増加が少なく
切削性の一層の向上が認められない。本発明の黒鉛を混
合する対象の粉末冶金用鉄粉は、粉末冶金に用いられる
鉄粉ならば、純鉄粉でも良いし、合金鋼粉でも良く、と
くに限定されない。
The Mn of the iron powder for powder metallurgy produced by the spraying method using water is preferably less than 0.1%. When Mn is 0.1% or more, Mn in the powder easily bonds with S.
However, the effect of improving the machinability based on FeS described above is not exhibited, and the residual graphite is less increased than the iron powder containing no S, and no further improvement in machinability is observed. The iron powder for powder metallurgy to which the graphite of the present invention is mixed is not particularly limited, as long as it is an iron powder used in powder metallurgy, pure iron powder or alloy steel powder may be used.

【0018】[0018]

【実施例】【Example】

(請求項1の実施例および比較例)−1 表1に用いた4 種類の鉄粉の化学組成を示す。これらの
鉄粉は、溶鋼を水噴霧し、得た生粉を窒素雰囲気中で 1
40℃で60分乾燥した後、純水素雰囲気 930℃で20分還元
したのち、粉砕・分級して製造した。
(Examples and Comparative Examples of Claim 1) -1 Table 1 shows the chemical compositions of the four iron powders used. These iron powders are produced by water-spraying molten steel and the resulting raw powders in a nitrogen atmosphere.
It was dried at 40 ° C for 60 minutes, reduced in a pure hydrogen atmosphere at 930 ° C for 20 minutes, and then pulverized and classified to produce.

【0019】[0019]

【表1】 [Table 1]

【0020】鉄粉No. 1 〜4 にステアリン酸亜鉛1重量
%と、銅粉、平均粒径の異なる2種の黒鉛粉末を表2〜
5に示した配合で混合後、圧粉密度6.85g/cm3 になるよ
うに成形し、水素を10体積%含む窒素気流中で1130℃20
分焼結した。表2〜5において添加した黒鉛粉末2種の
なかで、粒径の大きい方の黒鉛粉末の添加量と平均粒径
をそれぞれ添加黒鉛量1、添加黒鉛平均粒径1として示
した。また粒径の小さい方の黒鉛粉末の添加量と平均粒
径をそれぞれ添加黒鉛量2、添加黒鉛平均粒径2として
示した。焼結中のガス流量は成形体1kgあたり5Nl/min
であった。得られた焼結鋼について引張強度、シャルピ
ー衝撃値の測定を行った。
Iron powders Nos. 1 to 4 each contain 1% by weight of zinc stearate, copper powder, and two types of graphite powders having different average particle sizes.
After mixing with the composition shown in 5, mold to a green compact density of 6.85 g / cm 3 in a nitrogen stream containing 10% by volume of hydrogen at 1130 ° C 20
Minute sintering. In Tables 2 to 5, among the two types of graphite powder added, the addition amount and average particle size of the graphite powder having the larger particle size are shown as the added graphite amount 1 and the added graphite average particle size 1, respectively. The addition amount and average particle size of the graphite powder having the smaller particle size are shown as the addition graphite amount 2 and the addition graphite average particle size 2, respectively. Gas flow rate during sintering is 5 Nl / min per 1 kg of compact
Met. The tensile strength and the Charpy impact value of the obtained sintered steel were measured.

【0021】[0021]

【表2】 [Table 2]

【0022】[0022]

【表3】 [Table 3]

【0023】[0023]

【表4】 [Table 4]

【0024】[0024]

【表5】 [Table 5]

【0025】切削性の評価は外径60φ、高さ10mmの円板
形状、圧粉密度6.85g/cm3 とし、上記の条件で焼結後、
直径1mmφのハイス製ドリルを用いて10000rpm、0.012m
m/rev の条件で加工が不可能になるまでの加工した穴の
平均数(ドリル3本の平均値)を工具寿命として評価し
た。焼結鋼の残留黒鉛量は、硝酸溶解残さをガラスフィ
ルタでろ過し、赤外線吸収法で定量化した。
The machinability was evaluated by using a disk shape having an outer diameter of 60φ and a height of 10 mm, a green compact density of 6.85 g / cm 3, and sintering after the above conditions.
Using a HSS drill with a diameter of 1 mmφ, 10,000 rpm, 0.012 m
The tool life was evaluated as the average number of holes that were machined until the machining became impossible under the condition of m / rev (the average value of three drills). The residual graphite content of the sintered steel was quantified by infrared absorption method after filtering the nitric acid dissolution residue with a glass filter.

【0026】表2〜5の本発明例1〜24に示すように、
鉄粉No. 1〜4にCu粉末0.5 〜4%、平均粒径25〜120
μm の黒鉛粉末を0.1 〜1 %、平均粒径15μm 以下の黒
鉛粉末0.5 〜2%を含有した混合粉末を成形焼結するこ
とにより、水素を含有する雰囲気で焼結しても、優れた
切削性が得られることがわかる。鉄粉No. 4 をFe-2%Cu-
1.0%Gr-1.0%Znst (黒鉛粉末の平均粒径は10μm )の配
合で混合・成形後、水素を10体積% 含む窒素気流中で11
30℃20分焼結した場合、ドリル穿孔数は15個であり、残
留黒鉛量は0.03%だった。比較例1 、2、8、9、15、
16、22、23に示すように、粒径の大きい方の黒鉛粉末の
添加量が0.1 % 未満、あるいは平均粒径が25μm 未満で
は、残留黒鉛が少なく切削性が劣る。比較例3、10、1
7、24に示すように粒径の大きい方の黒鉛の粒径が120
μm を超えると切削性が低下する。比較例4、11、18、
25に示すように、粒径の大きい方の黒鉛粉末の添加量が
1 %を超えると、焼結鋼に肌荒れが生じた。比較例5、1
2、19、26に示すように粒径の小さい方の黒鉛粉末の添
加量が0.5 % 未満では、焼結鋼引張強度が低下する。比
較例6、13、20、27に示すように粒径の小さい方の黒鉛
粉末添加量が2 % を超えると切削性が低下する。比較例
7、14、21、28に示すよう粒径の小さい方の黒鉛粉末の
粒径が15μm を超えると、引張強度が低下する。なお、
添加Cu量が0.5%未満の本発明例5、11、17、23では引
張強度が低く、添加Cu量が4%を超える本発明例6、1
2、18、24では衝撃値が劣化するので、Cuの添加量は0.5
〜4%の範囲が望ましい。
As shown in Examples 1 to 24 of the present invention in Tables 2 to 5,
Iron powder No. 1-4, Cu powder 0.5-4%, average particle size 25-120
By forming and sintering a mixed powder containing 0.1 to 1% of graphite powder of μm and 0.5 to 2% of graphite powder with an average particle size of 15 μm or less, excellent cutting can be achieved even when sintered in an atmosphere containing hydrogen. It can be seen that the sex is obtained. Iron powder No. 4 with Fe-2% Cu-
After mixing and molding with a mixture of 1.0% Gr-1.0% Znst (average particle size of graphite powder is 10 μm), it was mixed in a nitrogen stream containing 10% by volume of hydrogen.
When sintered at 30 ° C for 20 minutes, the number of drilled holes was 15 and the amount of residual graphite was 0.03%. Comparative Examples 1, 2, 8, 9, 15,
As shown in 16, 22, and 23, when the addition amount of the graphite powder with the larger particle size is less than 0.1% or the average particle size is less than 25 μm, the residual graphite is small and the machinability is poor. Comparative Examples 3, 10, 1
As shown in 7 and 24, the particle size of graphite with the larger particle size is 120
If it exceeds μm, the machinability deteriorates. Comparative Examples 4, 11, 18,
As shown in 25, the addition amount of graphite powder with a larger particle size
If it exceeds 1%, the sintered steel becomes rough. Comparative Examples 5 and 1
As shown in Nos. 2, 19, and 26, if the addition amount of the graphite powder with the smaller particle size is less than 0.5%, the tensile strength of the sintered steel decreases. As shown in Comparative Examples 6, 13, 20, and 27, if the amount of graphite powder added with a smaller particle size exceeds 2%, the machinability deteriorates. As shown in Comparative Examples 7, 14, 21, and 28, when the particle size of the smaller graphite powder exceeds 15 μm, the tensile strength is reduced. In addition,
In the present invention examples 5, 11, 17, 23 in which the added Cu amount is less than 0.5%, the tensile strength is low, and the present invention examples 6, 1 in which the added Cu amount exceeds 4%
Since the impact value deteriorates at 2, 18, and 24, the addition amount of Cu is 0.5
The range of up to 4% is desirable.

【0027】(請求項1の実施例および比較例)−2 表6に用いた鉄粉の化学組成を示す。これらの鉄粉は、
溶鋼を水噴霧して得た生粉を窒素雰囲気中で140 ℃で60
分乾燥した後、純水素雰囲気930 ℃で20分還元した後、
粉砕・分級して製造した。
(Example of claim 1 and comparative example) -2 Table 6 shows the chemical composition of the iron powder used. These iron powders
Raw powder obtained by spraying molten steel with water at 60 ° C in a nitrogen atmosphere at 60 ° C
After drying for 20 minutes, reducing it in a pure hydrogen atmosphere at 930 ℃ for 20 minutes,
It was manufactured by crushing and classifying.

【0028】[0028]

【表6】 [Table 6]

【0029】鉄粉No. 5〜8にステアリン酸亜鉛1重量
% と、平均粒径の異なる2種の黒鉛粉末を表7〜10に
示す配合で混合後、圧粉密度6.85g/cm3 になるように成
形し、水素を10体積% 含む窒素気流中で1150℃30分焼結
した。
Iron powder Nos. 5 to 8 and 1 weight of zinc stearate
% And two types of graphite powders having different average particle diameters are mixed according to the formulations shown in Tables 7 to 10 and molded into a green compact density of 6.85 g / cm 3 in a nitrogen stream containing 10% by volume of hydrogen. Sintered at 1150 ° C for 30 minutes.

【0030】[0030]

【表7】 [Table 7]

【0031】[0031]

【表8】 [Table 8]

【0032】[0032]

【表9】 [Table 9]

【0033】[0033]

【表10】 [Table 10]

【0034】焼結後、(請求項1の実施例および比較
例)−1と同様の方法で引張強度、シャルピー衝撃値、
切削性、残留黒鉛量の測定を行った。表7〜10から本
発明例に示すように、鉄粉5〜8に平均粒径25〜12
0μm の黒鉛粉末を0.1 〜1 % 、平均粒径15μm 以下の
黒鉛粉末0.5 〜2 % 含む混合粉末を成形焼結することに
より、水素を含有する雰囲気中で焼結しても、優れた切
削性が得られることがわかる。鉄粉No. 8 をFe-2%Cu-1.
0%Gr-1.0%Znst (黒鉛粉末の平均粒径は10μm )の配合
で混合・成形後、水素を10体積% 含む窒素雰囲気気流中
で1130℃20分焼結した場合、ドリル穿孔数は2 個であ
り、残留黒鉛量は0.03% であった。比較例29、30、36、
37、43、44、50、51に示すように粒径の大きい方の黒鉛
粉末の添加量が0.1 % 未満、あるいは平均粒径が25μm
未満では、残留黒鉛が少なく切削性が劣る。比較例31、
38、45、52に示すように粒径の大きい方の黒鉛粉末の粒
径が120 μm を超えると切削性が低下する。比較例32、
39、46、53に示すように粒径の大きい方の黒鉛粉末量が
1 % を超えると、焼結鋼の肌荒れが生じた。比較例33、
40、47、54に示すように粒径の小さい方の黒鉛粉末の添
加量が0.5 % 未満では、焼結鋼の引張強度が低下する。
比較例34、41、48、55に示すように粒径の小さい方の黒
鉛粉末の添加量が2% を超えると切削性が低下する。比
較例35、42、49、56に示すように粒径の小さい方の黒鉛
粉末の粒径が15μm を超えると引張強度が低下する。
After sintering, the tensile strength, the Charpy impact value, and the like in the same manner as in (Example 1 of Claim 1 and Comparative Example) -1.
The machinability and the amount of residual graphite were measured. As shown in Tables 7 to 10 of the present invention, iron powders 5 to 8 have an average particle size of 25 to 12
By forming and sintering a mixed powder containing 0.1 to 1% of graphite powder of 0 μm and 0.5 to 2% of graphite powder having an average particle size of 15 μm or less, excellent machinability is obtained even when sintered in an atmosphere containing hydrogen. It can be seen that Iron powder No. 8 to Fe-2% Cu-1.
After mixing and molding with a mixture of 0% Gr-1.0% Znst (graphite powder has an average particle size of 10 μm) and sintering in a nitrogen atmosphere flow containing 10% by volume of hydrogen at 1130 ° C for 20 minutes, the number of drill holes is 2 And the amount of residual graphite was 0.03%. Comparative Examples 29, 30, 36,
As shown in 37, 43, 44, 50, 51, the addition amount of graphite powder with the larger particle size is less than 0.1%, or the average particle size is 25 μm.
If it is less than 1, the residual graphite is small and the machinability is poor. Comparative Example 31,
As shown in 38, 45 and 52, if the particle size of the graphite powder with the larger particle size exceeds 120 μm, the machinability deteriorates. Comparative Example 32,
As shown in 39, 46 and 53, the amount of graphite powder with the larger particle size
If it exceeds 1%, the surface of the sintered steel becomes rough. Comparative Example 33,
As shown in 40, 47, and 54, when the addition amount of the graphite powder with the smaller particle size is less than 0.5%, the tensile strength of the sintered steel decreases.
As shown in Comparative Examples 34, 41, 48 and 55, if the addition amount of the graphite powder with the smaller particle size exceeds 2%, the machinability deteriorates. As shown in Comparative Examples 35, 42, 49 and 56, when the particle size of the graphite powder having the smaller particle size exceeds 15 μm, the tensile strength decreases.

【0035】(請求項2の実施例と比較例)−1 (請求項1の実施例および比較例)−1の中で、鉄粉の
組成の影響を示すために、同一配合条件の結果を表11
にまとめて示した。すなわち、鉄粉No. 1〜4に、銅粉
末2 重量 %、ステアリン酸亜鉛1 重量% 、平均粒径60μ
m の黒鉛粉末を0.4 % と平均粒径10μm の黒鉛粉末0.8
% を含有した混合粉末を(請求項1の実施例および比較
例)−1で用いたと同じ条件で成形・焼結し、引張強
度、シャルピー衝撃値、切削性、残留黒鉛量の測定を行
った。
(Examples and Comparative Examples of Claim 2) -1 (Examples and Comparative Examples of Claim 1) -1 In order to show the influence of the composition of the iron powder, the results of the same compounding conditions are shown. Table 11
Are summarized in. That is, iron powder No. 1 to 4, copper powder 2% by weight, zinc stearate 1% by weight, average particle diameter 60 μ
0.4% m graphite powder and 0.8% graphite powder with an average particle size of 10 μm
% Of the mixed powder was molded and sintered under the same conditions as used in (Example 1 and Comparative Example 1), and the tensile strength, Charpy impact value, machinability, and residual graphite content were measured. .

【0036】[0036]

【表11】 [Table 11]

【0037】本発明例41からMn0.1 % 未満、S 量が0.08
〜3 % の鉄粉の焼結鋼は、S 量が0.08% 未満、あるいは
Mn0.1 % 以上の鉄粉の焼結鋼に比べ残留黒鉛量の増加
と、切削性の一層の向上が認められ、水を用いた噴霧法
により製造されるMn0.1 % 未満S を0.08〜0.3 % を含有
する粉末冶金用鉄粉の使用が好ましいことがわかる。比
較例57、58からS 量が0.08% 未満あるいはMn0.1 % 以上
の鉄粉の焼結鋼の場合、切削性が劣る。比較例59に示す
ように、S 含有量が0.3 % を超えた鉄粉No. 3 を焼結し
た場合、焼結鋼にすすが発生し、焼結炉の汚染が懸念さ
れた。
Inventive Example 41: Mn less than 0.1%, S content 0.08
Sintered steel with ~ 3% iron powder has an S content of less than 0.08%, or
An increase in the amount of residual graphite and a further improvement in machinability were observed in comparison with the sintered steel of iron powder of Mn0.1% or more, and Mn of less than 0.1% Sn produced by a spray method using water was 0.08- It can be seen that the use of iron powder for powder metallurgy containing 0.3% is preferred. From Comparative Examples 57 and 58, in the case of a sintered steel of iron powder having an S content of less than 0.08% or Mn of 0.1% or more, the machinability is poor. As shown in Comparative Example 59, when iron powder No. 3 with an S content exceeding 0.3% was sintered, soot was generated in the sintered steel, and there was a concern that the sintering furnace would be contaminated.

【0038】(請求項2の実施例と比較例)−2 (請求項1の実施例と比較例)−2のなかで、鉄粉の組
成の影響を示すために、同一配合条件の結果を表12に
まとめて示した。すなわち、鉄粉No. 5〜8に、ステア
リン酸亜鉛1重量% 、平均粒径50μm の黒鉛粉末を0.3
% 、平均粒径10μm の黒鉛粉末0.9 % を含有した混合粉
末を(請求項1の実施例と比較例)−2で用いたと同じ
条件で成形・焼結し、引張強度、シャルピー衝撃値、切
削性、残留黒鉛量の測定を行った。
(Example and Comparative Example of Claim 2) -2 (Example and Comparative Example of Claim 1) -2 In order to show the influence of the composition of the iron powder, the results of the same compounding conditions are shown. The results are summarized in Table 12. That is, 1% by weight of zinc stearate and 0.3% of graphite powder having an average particle size of 50 μm was added to iron powder Nos. 5 to 8.
%, A mixed powder containing 0.9% of graphite powder having an average particle size of 10 μm was molded and sintered under the same conditions as those used in (Example 1 and Comparative Example of claim 1) -2, tensile strength, Charpy impact value, cutting The properties and the amount of residual graphite were measured.

【0039】[0039]

【表12】 [Table 12]

【0040】本発明例42からMn0.1 % 未満、S 0.03〜0.
3 % の鉄粉の焼結鋼は、S 量が0.08% 未満、あるいはMn
0.1 % 以上の粉末の焼結鋼に比べ残留黒鉛量の増加と、
切削性の一層の向上が認められ、水を用いた噴霧法によ
り製造されるMn0.1 % 未満、S を0.08〜0.3 % を含有す
る粉末冶金用鉄粉の使用が好ましいことが分かる。比較
例60、61からS 量が0.08% 未満あるいはMn0.1 % 以上の
粉末の焼結鋼の場合、切削性は劣る。比較例62に示すよ
うに、S 含有量が0.3 % を超えた鉄粉No. 7を焼結した
場合、焼結鋼にすすが発生し、焼結炉の汚染が懸念され
た。
Inventive Example 42-Mn less than 0.1%, S 0.03-0.
Sintered steel with 3% iron powder has an S content of less than 0.08% or Mn
An increase in the amount of residual graphite compared to sintered steel with powder of 0.1% or more,
Further improvement in machinability is recognized, and it is understood that the use of iron powder for powder metallurgy containing Mn less than 0.1% and S 8 0.08 to 0.3% produced by a spraying method using water is preferable. In Comparative Examples 60 and 61, the machinability is poor in the case of the sintered steel of the powder in which the S content is less than 0.08% or Mn 0.1% or more. As shown in Comparative Example 62, when iron powder No. 7 with an S content exceeding 0.3% was sintered, soot was generated in the sintered steel, and there was a concern that the sintering furnace would be contaminated.

【0041】表11、表12には典型的な例を示したが、い
わゆる純鉄粉についての表2〜表5の結果および1%Cr-
0.3%Mo 合金鋼粉についての表7〜表10の結果を比較す
れば、鉄粉のMn含有量を0.1%未満およびS含有量を0.08
〜0.3%に限定することが切削性の一層の向上に有効であ
ることが分かる。
Typical examples are shown in Tables 11 and 12, and the results of Tables 2 to 5 and 1% Cr-for so-called pure iron powder are shown.
Comparing the results of Table 7 to Table 10 for 0.3% Mo alloy steel powder, the Mn content of the iron powder is less than 0.1% and the S content is 0.08.
It can be seen that limiting the content to ~ 0.3% is effective in further improving the machinability.

【0042】[0042]

【発明の効果】本発明により、従来の硫化物により切削
性を改善した焼結鋼よりも、優れた切削性を有する焼結
鋼を容易に得ることができる。
EFFECTS OF THE INVENTION According to the present invention, it is possible to easily obtain a sintered steel having excellent machinability as compared with the conventional sintered steel whose machinability has been improved.

───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7,DB名) C22C 33/02 ─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. 7 , DB name) C22C 33/02

Claims (2)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】 純鉄粉あるいは合金鋼粉を用いて成形・
焼結により焼結鋼を得る粉末冶金法において、粉末冶金
用鉄粉に平均粒径25〜120 μm の黒鉛粉末を0.1 〜 1.0
重量%、平均粒径15μm 以下の黒鉛粉末0.5 〜2重量%
を混合した混合粉末を成形・焼結することを特徴とする
切削性に優れた焼結鋼の製造方法。
1. Molding using pure iron powder or alloy steel powder
In the powder metallurgy method of obtaining sintered steel by sintering, 0.1 to 1.0 of graphite powder with an average particle size of 25 to 120 μm is added to iron powder for powder metallurgy.
% By weight, graphite powder with an average particle size of 15 μm or less 0.5-2% by weight
A method for producing a sintered steel having excellent machinability, which comprises molding and sintering a mixed powder containing a mixture of:
【請求項2】 純鉄粉あるいは合金鋼粉を用いて成形・
焼結により焼結鋼を得る粉末冶金法において、Mnを0.1
重量% 未満とSを0.08〜0.3 重量%を含有する粉末冶金
用アトマイズ鉄粉に平均粒径25〜120 μm の黒鉛粉末を
0.1 〜1.0 %、平均粒径15μm 以下の黒鉛粉末0.5 〜2
重量%を混合した混合粉末を成形・焼結することを特徴
とする切削性に優れた焼結鋼の製造方法。
2. Molding using pure iron powder or alloy steel powder
In powder metallurgy to obtain sintered steel by sintering, Mn is 0.1
Atomized iron powder for powder metallurgy containing less than 10 wt% and 0.08 to 0.3 wt% S with graphite powder with an average particle size of 25 to 120 μm.
Graphite powder with a particle size of 0.1-1.0% and an average particle size of 15μm or less 0.5-2
A method for producing a sintered steel having excellent machinability, which comprises molding and sintering a mixed powder in which the weight% is mixed.
JP08184694A 1994-04-20 1994-04-20 Manufacturing method of sintered steel with excellent machinability Expired - Fee Related JP3491094B2 (en)

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