JP3573872B2

JP3573872B2 - Method of manufacturing sintered alloy joint valve seat and sintered alloy material for joint valve seat

Info

Publication number: JP3573872B2
Application number: JP10511696A
Authority: JP
Inventors: 輝夫高橋; 新垣内
Original assignee: Nippon Piston Ring Co Ltd
Current assignee: Nippon Piston Ring Co Ltd
Priority date: 1996-04-25
Filing date: 1996-04-25
Publication date: 2004-10-06
Anticipated expiration: 2016-04-25
Also published as: JPH09287422A

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関用のバルブシートに関し、とくにシリンダヘッドに接合できる焼結合金製バルブシートに関する。
【０００２】
【従来の技術】
バルブシートは、エンジンのシリンダヘッドに圧入されて使用され、燃焼ガスのシールとバルブを冷却する役割を担っている。そのため、バルブによる叩かれ、すべりによる摩耗、燃焼ガスによる加熱、燃料と燃料に含まれる添加物およびその燃焼生成物、熱変成物による腐食等をうける。
【０００３】
焼結合金は、合金粉末を配合混練して金型に充填し圧縮成形したのち、所定の温度、雰囲気中で焼結したものであり、通常の溶製法では得難い合金が容易に製造できる。また、機能の複合化が容易なため独特な機能を付与した部品の製造も可能であり、多孔質材や難加工材などの製造や、形の複雑な機械部品の製造に適している。近年、耐摩耗性が要求されるバルブシートにこの焼結合金が適用されている。
【０００４】
例えば、特開昭５９−２５９５９号公報には、Ｃ、Ｎｉ、Ｃｒ、Ｍｏ、Ｗ、Ｃｏを多量に含み、基地組織中にＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子とＦｅ−Ｍｏ粒子の硬質粒子が分散し、連続空孔が銅合金にて溶浸されたバルブシート用焼結合金材が開示されている。このバルブシート用焼結合金材は、強度および剛性に優れ、かつ耐摩耗性に優れたバルブシートとして、成形・焼結後油焼入れ焼戻し処理により製品化され、圧入によりシリンダヘッドに組み入れられ使用されている。
【０００５】
しかし、最近では、自動車の高速化・軽量化等の要望から、内燃エンジンでは、多バルブ化が進んでおり、各気筒には複数の吸・排気ポートが近接して配置されている。このような最近の傾向から、バルブ間の距離を狭くしたり、吸・排気ポート径を大きくする等の設計の自由度を確保したり、あるいは、バルブ・バルブシートの熱引け性を良くし熱負荷の軽減を図る等の目的で、シリンダヘッドにバルブシートを接合する接合型バルブシートが考えられている。
【０００６】
しかしながら、上記したような従来のバルブシート用焼結合金材を接合型バルブシートに適用すると、バルブシートを接合するとき、あるいは、エンジンの運転時に、バルブシートにクラック（亀裂）が発生し、バルブシートのシール性が低下するという問題があった。
このような問題に対し、例えば、特開平７−１８９６２８号公報には、Ｃｕ基合金またはオーステナイト基地鉄系合金を抵抗溶接によりシリンダヘッドに接合されてなる接合型バルブシートが提案されている。
【０００７】
しかし、このバルブシートは、接合時、あるいは運転時にクラックが発生しないが、高価な合金元素を含んでおり経済的に不利であること、あるいはさらに、強度、剛性が低いこと、また、耐摩耗性が劣るという問題があった。
【０００８】
【発明が解決しようとする課題】
本発明は、上記した問題点を有利に解決し、接合型バルブシートとしてもクラックが発生しない、伸び・靱性に優れかつ耐摩耗性に優れた焼結合金製接合型バルブシートおよび焼結合金材の製造方法を提案することを目的とする。
【０００９】
【課題を解決するための手段】
本発明者らは、銅溶浸によって封孔処理を施した鉄系焼結合金材は、バルブシート用として強度、熱伝導率の点で最適であるという考えで、上記課題を解決するために、鉄系焼結合金材について鋭意検討した結果、従来の鉄系焼結合金材は、銅を溶浸した延性・靱性の低い材料であり、接合時に発生する多大な熱応力（引張応力）に耐えられず、クラックを生じるが、しかし、材料の伸びを１．０％以上とすることができれば、鉄系焼結合金材でも接合時にクラックが発生しないことを見いだし、本発明を構成した。
【００１０】
本発明は、重量％で、Ｃ：0.5 〜1.7 ％、Ni：0.5 〜2.5 ％、Cr：3.0 〜8.0 ％、Ｗ：1.0 〜3.8 ％、Co：4.5 〜8.5 ％を含有し残部が不可避的不純物およびFeからなり、かつ250 メッシュ以下のＣ−Cr−Ｗ−Co−Fe粒子を容量％で8 〜14％有し、焼結空孔が銅合金にて溶浸され、基地組織がオーステナイト、ベイナイトと粒状パーライトからなり、 1.0 ％以上の伸びを有する焼結合金材からなることを特徴とする焼結合金製接合型バルブシートである。
【００１１】
また、本発明は、重量％で、Ｃ：0.5 〜1.7 ％、Ni：0.5 〜2.5 ％、Cr：3.0 〜8.0 ％、Mo：0.1 〜0.9 ％、Ｗ：1.0 〜3.8 ％、Co：4.5 〜8.5 ％を含有し残部が不可避的不純物およびFeからなり、かつ250 メッシュ以下のＣ−Cr−Ｗ−Co−Fe粒子とFe−Mo粒子とを容量％で8 〜14％有し、焼結空孔が銅合金にて溶浸され、基地組織がオーステナイト、ベイナイトと粒状パーライトからなり、 1.0 ％以上の伸びを有する焼結合金材からなることを特徴とする焼結合金製接合型バルブシートである。
【００１２】
更にまた、本発明は、重量％で、Ｃ：０．５〜１．７％、Ｎｉ：０．５〜２．５％、Ｃｒ：３．０〜８．０％、Ｗ：１．０〜３．８％、Ｃｏ：４．５〜８．５％を含有し残部が不可避的不純物およびＦｅからなり、かつ２５０メッシュ以下のＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子を容量％で８〜１４％有する焼結体、もしくは重量％で、Ｃ：０．５〜１．７％、Ｎｉ：０．５〜２．５％、Ｃｒ：３．０〜８．０％、Ｍｏ：０．１〜０．９％、Ｗ：１．０〜３．８％、Ｃｏ：４．５〜８．５％を含有し残部が不可避的不純物およびＦｅからなり、かつ２５０メッシュ以下のＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子とＦｅ−Ｍｏ粒子とを容量％で８〜１４％有する焼結体を、溶浸用銅合金とともに銅合金の融点以上に加熱し、空孔に銅合金を溶浸させ、さらに、Ａ_ｃ３あるいはＡ_ｃｍ変態点以上１２００℃以下の温度に加熱したのち、４．５ ℃／ｍｉｎ以下の冷却速度で６５０ ℃以下まで冷却しついで空冷することを特徴とする伸び特性・耐摩耗性に優れた接合型バルブシート用焼結合金材の製造方法であり、また、本発明は、前記焼結体を、溶浸用銅合金とともにＡ_Ｃ３あるいはＡ_ｃｍ変態点以上でかつ銅合金の融点以上１２００℃以下の温度に加熱し、銅合金の溶浸処理と熱処理用加熱とを同時に行ってもよい。
【００１３】
【発明の実施の形態】
本発明のバルブシート用焼結合金材の成分組成について説明する。
Ｃ：０．５〜１．７％
Ｃは、基地を所定の組織、硬さに調整するため、およびＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子を形成するために必要な元素であり、０．５％未満では基地のフェライト量が過多となり基地強度が低下し、さらに、硬質粒子量も不足する。また、１．７％を超えると基地のセメンタイト量が多くなり被削性が低下する。このため、Ｃは、０．５〜１．７％の範囲とした。なお、より好ましくは１．０〜１．５％である。Ｃは、黒鉛粉末およびＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ合金粉末として添加されるのが好ましい。
【００１４】
Ｎｉ：０．５〜２．５％
Ｎｉは、基地に固溶して耐熱性を向上させる元素であり、０．５％未満ではその効果が少なく、また２．５％を超えると焼入れ性が劣化する。このため、Ｎｉは０．５％〜２．５％の範囲とした。なお、より好ましくは０．８〜２．３％である。ＮｉはＮｉ粉として添加するか、あるいは鉄粉中に予合金化しておくのが好ましい。
【００１５】
Ｃｒ：３．０〜８．０％
Ｃｒは、耐摩耗性を向上させる元素であり、Ｃ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ合金粉末として添加される。Ｃｒが３．０％未満では、硬質粒子量が不足し耐摩耗性・耐熱性が劣化する。８．０％を超えると、硬質粒子量が過多となり、焼結体の強度が低下する。このため、Ｃｒは３．０〜８．０％の範囲に限定した。なお、より好ましくは３．５〜７．５％である。
【００１６】
Ｍｏ：０．１〜０．９％
Ｍｏは添加されていなくても使用に供することができるが、Ｍｏを添加した場合には更に、耐摩耗性を向上させることができる。本発明では、Ｆｅ−Ｍｏ粒子を形成し、硬質粒子として基地中に分散して耐摩耗性向上に寄与する。Ｍｏが０．１％未満では、Ｆｅ−Ｍｏ粒子量が少なく耐摩耗性がそれほど向上しない。また、０．９％を超えるとＦｅ−Ｍｏ粒子量が過多となり、焼結体の強度が不足する。このため、Ｍｏは０．１〜０．９％の範囲に限定した。なお、より好ましくは０．３〜０．７％である。ＭｏはＦｅ−Ｍｏ粉末あるいは低Ｃ−Ｆｅ−Ｍｏ粉末として添加されるのが好ましい。
【００１７】
Ｗ：１．０〜３．８％
Ｗは、Ｃ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子を形成することにより、耐摩耗性を向上させる。１．０％未満では、硬質粒子量が不足し耐摩耗性が劣化し、３．８％を超えると硬質粒子が過多となり焼結体の強度が不足する。このため、Ｗは１．０〜３．８％の範囲に限定した。なお、より好ましくは１．３〜３．３％である。Ｗは、Ｃ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ合金粉末として添加するのが好ましい。
【００１８】
Ｃｏ：４．５〜８．５％
Ｃｏは、Ｃ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子を形成することにより、耐摩耗性を向上させる。さらに、Ｃｏは、硬質粒子と基地との結合を強化したり、基地中に固溶し耐熱性を向上させる効果を有する。４．５％未満ではその効果が認められず、また８．５％を超えると硬質粒子が過多となり焼結体の強度が不足する。このため、Ｃｏは、４．５〜８．５％の範囲とした。なお、より好ましくは５．０〜８．０％である。Ｃｏは、Ｃ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ合金粉末およびＣｏ粉末として添加するのが好ましい。Ｃｏ粉末の代わりに一部、鉄粉中に合金化して添加してもよい。
【００１９】
本発明のバルブシート用焼結合金材は残部は実質的にＦｅである。
本発明のバルブシート用焼結合金材は、上記組成を有し、さらに、硬質粒子として、２５０メッシュ以下のＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子を、またはＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子およびＦｅ−Ｍｏ粒子を容量％で、８〜１４％含有する。
硬質粒子として２５０メッシュを超える粗い粉末を用いると、混合粉末の圧縮成形性が低下し、さらに、焼結合金において硬質粒子の脱落、不均一性による耐摩耗性の低下が生じるため、硬質粒子は２５０メッシュ以下とする。
【００２０】
硬質粒子量が８容量％未満では、硬質粒子が不足し耐摩耗性が劣化する。一方、１４容量％を超えると、硬質粒子が過多となり混合粉末の圧縮成形性が低下し、焼結体の強度が不足する。
ベースとなる鉄粉は、アトマイズ鉄粉あるいは還元鉄粉等いずれの鉄粉も好適に適用できる。鉄粉には予め合金元素を予合金させてもよい。
【００２１】
硬質粒子であるＣ−Ｃｒ−Ｗ−Ｃｏ−Ｆｅ粒子は、Ｃ：２．０〜３．０％、Ｃｏ：７．０〜１５％、Ｗ：１５〜２５％、Ｆｅ：１．０〜８．０％、残部が実質的にＣｒである合金粉末として添加するのが好ましい。
硬質粒子であるＦｅ−Ｍｏ粒子は、Ｍｏ：５０〜７０％のフェロモリブデン粉末として添加するのが好ましい。
【００２２】
本発明のバルブシート用焼結合金材を得るには、純鉄粉にＮｉ、Ｃｏの単粉を混合するか、純鉄粉にＣ、Ｎｉ、Ｃｏを予合金した合金鉄粉に、さらに、硬質粒子となる合金粉、Ｃ粉を上記した組成になるように配合し混練する。なお、潤滑材としてステアリン酸亜鉛等を配合してもよい。
次に、これら粉末を金型に充填し、成形プレスにより圧縮・成形し圧粉体とする。ついで、圧粉体を焼結させて焼結体を得る。
【００２３】
焼結条件は、圧粉体を保護雰囲気中で１１００〜１２００℃の温度範囲に加熱し焼結されるのが望ましい。１１００℃未満では、焼結拡散が不十分であり、１２００℃を超えると硬質粒子、基地の過拡散が生じ耐摩耗性が劣化する。
焼結体を、さらに、溶浸用銅合金とともに銅合金の融点以上に加熱し、空孔に銅合金を溶浸させる溶浸処理を施す。この溶浸処理は後述する焼結体の熱処理と同時に行っても構わない。
【００２４】
つぎに、本発明では、上記組成の焼結体を溶浸処理を施したのちあるいは溶浸処理を施さず、加熱し冷却する熱処理を施す。
本発明では、焼結合金材の伸びを１．０％以上と、伸び特性を向上させるために、焼結合金材の組織をオーステナイト＋ベイナイト＋粒状パーライト組織とする。そのために、熱処理条件を限定している。
【００２５】
熱処理の加熱温度は、焼結体のＡ_ｃ３あるいはＡ_ｃｍ変態点以上、１２００℃以下とする。
加熱温度がＡ_ｃ３あるいはＡ_ｃｍ変態点未満では、伸び特性の優れたオーステナイト＋ベイナイト＋粒状パーライト組織が得られず、焼戻しマルテンサイト＋パーライト組織となり伸び値の向上が望めない。また、１２００℃を超えると、結晶粒が粗大化し、さらに硬質粒子、基地の過拡散が生じ延性・靱性、耐摩耗性が劣化する。このようなことから、熱処理の加熱温度はＡ_ｃ３あるいはＡ_ｃｍ変態点以上好ましくは１２００℃以下とする。好ましくは、７５０ ℃以上１２００℃以下である。なお、溶浸処理を施していない焼結体については、加熱時に溶浸用銅合金とともに銅合金の融点以上に加熱し溶浸処理を同時に行っても良い。
【００２６】
上記加熱温度に加熱したのち、４．５ ℃／ｍｉｎ以下の冷却速度で６５０ ℃以下まで冷却しついで空冷する。
６５０ ℃以下までの冷却速度が４．５ ℃／ｍｉｎを超える冷却速度では、伸び特性の優れたオーステナイト＋ベイナイト＋粒状パーライト組織が得られず、マルテンサイト＋ベイナイト組織となり、高い伸び値が得られない。冷却速度の制御が６５０ ℃を超える温度までの場合は、所定の伸び特性の優れた組織が得られない。
【００２７】
上記した熱処理を施したのち、必要に応じ焼戻しを施してもよい。
上記した組成と熱処理を組み合わせることにより、焼結合金材の伸び特性が向上し、本発明の焼結合金材を接合型バルブシートに適用しても、クラックの発生は見られない。また、本発明の焼結合金製接合型バルブシートの少なくとも接合面に銅めっきを施すことは、接合性を向上させるうえから好ましいことである。
【００２８】
接合型バルブシートは、焼結合金材を所定の形状に加工し、抵抗溶接、摩擦圧接、電子ビーム溶接等によりシリンダヘッドに接合される。
【００２９】
【実施例】
まず、試験Ｎｏ．１〜Ｎｏ．７、Ｎｏ．１３は原料粉末として、重量％で、Ｃ粉末（−３２５メッシュ）１．２％、Ｃｏ粉末（５μｍ以下）６．０％、Ｎｉ粉末（−３２５メッシュ）２．０％、Ｆｅ−６０％Ｍｏ粉末（−２５０メッシュ）１．０％、２．５％Ｃ− １．０％Ｃｏ−１９％Ｗ−６３．５％Ｃｒ−５％Ｆｅ合金粉末（−２５０メッシュ）１１．５％、残部アトマイズ純鉄粉に、ステアリン酸亜鉛１％を配合し、混練した。試験Ｎｏ．８〜Ｎｏ．１２は原料粉末として、重量％で、Ｃ粉末（−３２５メッシュ）１．２％、Ｃｏ粉末（５μｍ以下）６．０％、Ｎｉ粉末（−３２５メッシュ）２．０％、２．５％Ｃ− １．０％Ｃｏ−１９％Ｗ−６３．５％Ｃｒ−５％Ｆｅ合金粉末（−２５０メッシュ）１１．５％、残部アトマイズ純鉄粉に、ステアリン酸亜鉛１％を配合し、混練した。これら混合原料粉末を６ｔｏｎ／ｃｍ^２の圧力で圧粉成形し、還元性雰囲気で１１１０℃、６０ｍｉｎ焼結し、これに溶浸用銅合金を載置し１１３０℃、６０ｍｉｎ溶浸処理を施した。一部の焼結体（試験Ｎｏ．７、Ｎｏ．１２）は上記溶浸処理を施していない。
【００３０】
ついで、表１に示す加熱冷却条件で、焼結体を熱処理した。試験Ｎｏ．７、Ｎｏ．１２は、加熱時に溶浸用銅合金を載置し溶浸処理を同時に行った。
【００３１】
【表１】

【００３２】
試験Ｎｏ．１〜Ｎｏ．７の焼結合金材の組成は、Ｃ：１．３％、Ｎｉ：２．０％、Ｃｒ：７．５％、Ｍｏ：０．６％、Ｗ：２．２％、Ｃｏ：７．５％、残部不純物およびＦｅであり、基地中に分散した硬質粒子は、１３容量％であった。また、試験Ｎｏ．８〜Ｎｏ．１２の焼結合金材の組成は、Ｃ：１．３％、Ｎｉ：２．０％、Ｃｒ：７．５％、Ｗ：２．２％、Ｃｏ：７．５％、残部不純物およびＦｅであり、基地中に分散した硬質粒子は、１２容量％であった。焼結空孔の１０〜１５％には銅合金が溶浸されていた。この焼結合金材の変態点（Ａ_ｃｍ）は、７３５℃であった。熱処理後に、焼結合金材の引張試験を実施し、伸びを測定した。測定結果を表１に併記する。
【００３３】
本発明適用例の試験Ｎｏ．１〜３、Ｎｏ．５〜７、Ｎｏ．８〜９、Ｎｏ．１１〜１２は、伸びが１．０％以上あるのに対し、比較例の試験Ｎｏ．４、Ｎｏ．１０の伸びはそれぞれ０．８％、０．６％、従来例の試験Ｎｏ．１３の伸びは０．３％と１．０％未満であり、本発明適用例は優れた伸び特性を有していることがわかる。
本発明適用例の試験Ｎｏ．１、従来例の試験Ｎｏ．１３と同じ組成・処理条件で処理し、バルブシートに加工したのち、シリンダヘッド（材質：ＡＤＣ４）に抵抗溶接により接合した。この接合時の熱応力により、本発明適用例の試験Ｎｏ．１のバルブシートには、クラックの発生はみられなかった。しかし、従来例の試験Ｎｏ．１３のバルブシートには、半径方向のクラックが発生した。本発明の範囲であれば、接合型バルブシートに適用しても、接合時の熱応力により、クラックを発生することはない。
【００３４】
表１に示す熱処理を施した焼結合金材を、通常圧入タイプのバルブシートに加工し、耐摩耗性を単体リグ摩耗試験で確認した。試験条件は、つぎのとおりである。
試験温度：３５０℃（シート面）
コンタクト数：１．６ ×１０^６回
カム回転数：３０００ｒｐｍ
バルブ回転数：２０ｒｐｍ
スプリング荷重：３０ｋｇｆ（リフト時）
バルブ材質：ＳＵＨ３５（ステライトＮｏ．６盛金）
リフト量：７．２ｍｍ
試験結果を図１に示す。
【００３５】
本発明適用例の試験Ｎｏ．１〜３、Ｎｏ．５〜７、Ｎｏ．８〜９、Ｎｏ．１１〜１２では、バルブシート摩耗量は９〜１１μｍであり、従来例のＮｏ．１３と同等の耐摩耗性を示した。
【００３６】
【発明の効果】
本発明によれば、伸び・靱性に優れかつ耐摩耗性に優れた焼結合金材が得られ、該焼結合金材を用いた接合型バルブシートにはクラックを生じることがなく高いシール性を維持することができるという効果が得られる。
【図面の簡単な説明】
【図１】単体リグ試験後のバルブシート摩耗量を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a valve seat for an internal combustion engine, and more particularly to a sintered alloy valve seat that can be joined to a cylinder head.
[0002]
[Prior art]
The valve seat is used by being press-fitted into a cylinder head of the engine, and plays a role of sealing a combustion gas and cooling the valve. As a result, the valve is hit by a valve, worn by sliding, heated by a combustion gas, corroded by a fuel and additives contained in the fuel, its combustion products, and thermal denatured products.
[0003]
The sintered alloy is obtained by compounding and kneading alloy powder, filling in a mold, compression-molding, and then sintering at a predetermined temperature and atmosphere. An alloy which is difficult to obtain by a normal melting method can be easily produced. In addition, since it is easy to combine functions, it is possible to manufacture parts with unique functions, and it is suitable for manufacturing porous materials and difficult-to-process materials, and for manufacturing mechanical parts having complicated shapes. In recent years, this sintered alloy has been applied to valve seats requiring abrasion resistance.
[0004]
For example, Japanese Unexamined Patent Publication No. 59-25959 discloses that a matrix contains a large amount of C, Ni, Cr, Mo, W, and Co, and the base tissue contains hard C-Cr-W-Co-Fe particles and Fe-Mo particles. A sintered alloy material for a valve seat in which particles are dispersed and continuous pores are infiltrated with a copper alloy is disclosed. This sintered alloy material for valve seats has excellent strength, rigidity, and excellent wear resistance. It is commercialized as an oil quenching and tempering treatment after molding and sintering. ing.
[0005]
However, recently, in response to demands for speeding up and reducing the weight of automobiles, the number of valves in internal combustion engines has been increasing, and a plurality of intake / exhaust ports are arranged close to each cylinder. Due to such recent trends, the degree of freedom in design, such as reducing the distance between valves, increasing the diameter of the intake / exhaust ports, etc., or improving the heat-releasing properties of valves and valve seats, For the purpose of reducing the load and the like, a joint type valve seat for joining a valve seat to a cylinder head has been considered.
[0006]
However, when the above-described conventional sintered alloy material for a valve seat is applied to a joint-type valve seat, a crack (crack) occurs in the valve seat when the valve seat is joined or the engine is operated, and the valve seat is cracked. There is a problem that the sealing property of the sheet is reduced.
To cope with such a problem, for example, Japanese Patent Application Laid-Open No. Hei 7-189628 proposes a joint type valve seat in which a Cu-based alloy or an austenitic base iron-based alloy is joined to a cylinder head by resistance welding.
[0007]
However, this valve seat does not crack at the time of joining or operation, but contains an expensive alloy element and is economically disadvantageous, or has low strength and rigidity, and has abrasion resistance. Was inferior.
[0008]
[Problems to be solved by the invention]
The present invention advantageously solves the above-mentioned problems, does not generate cracks even when used as a jointed valve seat, has excellent elongation and toughness, and has excellent wear resistance. The purpose of the present invention is to propose a manufacturing method.
[0009]
[Means for Solving the Problems]
The present inventors have thought that the iron-based sintered alloy material subjected to the sealing treatment by copper infiltration is optimal for valve seats in terms of strength and thermal conductivity, and to solve the above problems. As a result of diligent studies on iron-based sintered alloy materials, conventional iron-based sintered alloy materials are low in ductility and toughness infiltrated with copper, and are subject to a large amount of thermal stress (tensile stress) generated during joining. It was not able to withstand, and cracks were generated. However, if the elongation of the material could be made 1.0% or more, it was found that cracks did not occur at the time of joining even with an iron-based sintered alloy material, and the present invention was constituted.
[0010]
The present invention contains C: 0.5-1.7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, W: 1.0-3.8%, Co: 4.5-8.5% by weight, and the balance is inevitable impurities. And 8 to 14% by volume of C-Cr-W-Co-Fe particles consisting of Si and Fe and having a mesh size of 250 mesh or less, the sintered pores are infiltrated with a copper alloy, and the base structures are austenite and bainite. and Ri Do granular perlite, a sintered alloy joined type valve seat, characterized in Rukoto such a sintered alloy material having an elongation of 1.0% or more.
[0011]
In the present invention, C: 0.5-1.7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, Mo: 0.1-0.9%, W: 1.0-3.8%, Co: 4.5-8.5% by weight. % Of C-Cr-W-Co-Fe particles and Fe-Mo particles of 250 mesh or less, the balance being 8 to 14% by volume. There is infiltration of copper alloy, the base structure is austenite, Ri Do bainite and granular pearlite, in sintered alloy joined type valve seat, characterized in Rukoto such a sintered alloy material having an elongation of 1.0% or more is there.
[0012]
Furthermore, in the present invention, C: 0.5-1.7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, W: 1.0-% by weight%. C-Cr-W-Co-Fe particles containing 3.8%, Co: 4.5-8.5%, the balance consisting of unavoidable impurities and Fe, and 250 mesh or less, having a volume percentage of 8-14. % Or by weight%, C: 0.5-1.7%, Ni: 0.5-2.5%, Cr: 3.0-8.0%, Mo: 0.1- C-Cr-W- containing 0.9%, W: 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and 250 mesh or less. A sintered body having 8 to 14% by volume of Co-Fe particles and Fe-Mo particles is heated together with the copper alloy for infiltration to a temperature equal to or higher than the melting point of the copper alloy, and the copper alloy is filled in the pores. Immersed was _further, after heating to _{A c3} or _{A cm} transformation point or above 1200 ° C. or less of the temperature, elongation properties, characterized in that it followed air cooled to 650 ° C. or less in the following cooling rate 4.5 ° C. / min - a method for producing a wear-resistant high joint type valve seat sintered alloy material, also, the present invention, and the sintered body, in conjunction with infiltration copper alloy a _C3 or a _cm transformation point or higher The copper alloy may be heated to a temperature equal to or higher than the melting point of the copper alloy and equal to or lower than 1200 ° C., and the infiltration treatment and the heat treatment for the copper alloy may be simultaneously performed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The component composition of the sintered alloy material for a valve seat of the present invention will be described.
C: 0.5 to 1.7%
C is an element necessary for adjusting the matrix to a predetermined structure and hardness and for forming C—Cr—W—Co—Fe particles. When the content is less than 0.5%, the amount of ferrite in the matrix is excessive. And the strength of the matrix is reduced, and the amount of hard particles is also insufficient. On the other hand, when the content exceeds 1.7%, the amount of cementite in the matrix increases and the machinability decreases. For this reason, C is set in the range of 0.5 to 1.7%. Note that the content is more preferably 1.0 to 1.5%. C is preferably added as a graphite powder and a C-Cr-W-Co-Fe alloy powder.
[0014]
Ni: 0.5 to 2.5%
Ni is an element that forms a solid solution in the matrix to improve heat resistance. If its content is less than 0.5%, its effect is small, and if it exceeds 2.5%, the hardenability deteriorates. Therefore, Ni is set in the range of 0.5% to 2.5%. In addition, more preferably, it is 0.8 to 2.3%. Ni is preferably added as Ni powder or pre-alloyed in iron powder.
[0015]
Cr: 3.0 to 8.0%
Cr is an element that improves wear resistance, and is added as a C-Cr-W-Co-Fe alloy powder. If the Cr content is less than 3.0%, the amount of hard particles is insufficient, and the wear resistance and heat resistance deteriorate. If it exceeds 8.0%, the amount of hard particles becomes excessive, and the strength of the sintered body decreases. For this reason, Cr was limited to the range of 3.0 to 8.0%. In addition, more preferably, it is 3.5 to 7.5%.
[0016]
Mo: 0.1 to 0.9%
Even if Mo is not added, it can be used, but when Mo is added, the abrasion resistance can be further improved. In the present invention, Fe—Mo particles are formed and dispersed in the matrix as hard particles, thereby contributing to an improvement in wear resistance. If Mo is less than 0.1%, the amount of Fe-Mo particles is small, and the wear resistance is not so improved. On the other hand, if it exceeds 0.9%, the amount of Fe-Mo particles becomes excessive, and the strength of the sintered body becomes insufficient. For this reason, Mo was limited to the range of 0.1 to 0.9%. The content is more preferably 0.3 to 0.7%. Mo is preferably added as Fe-Mo powder or low C-Fe-Mo powder.
[0017]
W: 1.0 to 3.8%
W improves wear resistance by forming C-Cr-W-Co-Fe particles. If it is less than 1.0%, the amount of hard particles is insufficient and wear resistance is deteriorated. If it exceeds 3.8%, the amount of hard particles is excessive and the strength of the sintered body is insufficient. For this reason, W is limited to the range of 1.0 to 3.8%. In addition, more preferably, it is 1.3 to 3.3%. W is preferably added as a C-Cr-W-Co-Fe alloy powder.
[0018]
Co: 4.5 to 8.5%
Co improves wear resistance by forming C-Cr-W-Co-Fe particles. Further, Co has an effect of strengthening the bond between the hard particles and the matrix, or forming a solid solution in the matrix to improve heat resistance. If it is less than 4.5%, the effect is not recognized, and if it exceeds 8.5%, the hard particles are excessive and the strength of the sintered body is insufficient. For this reason, Co is set in the range of 4.5 to 8.5%. In addition, more preferably, it is 5.0 to 8.0%. Co is preferably added as a C—Cr—W—Co—Fe alloy powder and a Co powder. Instead of the Co powder, a part thereof may be alloyed and added to the iron powder.
[0019]
The balance of the sintered alloy material for a valve seat of the present invention is substantially Fe.
The sintered alloy material for a valve seat of the present invention has the above composition, and further comprises, as hard particles, C-Cr-W-Co-Fe particles of 250 mesh or less, or C-Cr-W-Co-Fe particles. It contains 8 to 14% by volume of particles and Fe-Mo particles.
When a coarse powder exceeding 250 mesh is used as the hard particles, the compression moldability of the mixed powder is reduced, and further, the hard particles fall off in the sintered alloy, and the wear resistance is reduced due to non-uniformity. 250 mesh or less.
[0020]
If the amount of the hard particles is less than 8% by volume, the hard particles are insufficient and the wear resistance is deteriorated. On the other hand, when the content exceeds 14% by volume, the amount of the hard particles becomes excessive, and the compression moldability of the mixed powder is reduced, and the strength of the sintered body is insufficient.
Any iron powder such as atomized iron powder or reduced iron powder can be suitably used as the base iron powder. The alloying element may be pre-alloyed to the iron powder in advance.
[0021]
C-Cr-W-Co-Fe particles, which are hard particles, contain C: 2.0 to 3.0%, Co: 7.0 to 15%, W: 15 to 25%, and Fe: 1.0 to 8%. 0.0%, with the balance being substantially Cr.
The Fe-Mo particles, which are hard particles, are preferably added as a ferromolybdenum powder having a Mo content of 50 to 70%.
[0022]
In order to obtain the sintered alloy material for a valve seat of the present invention, a single powder of Ni and Co is mixed with pure iron powder, or an alloy iron powder obtained by pre-alloying C, Ni, and Co with pure iron powder, An alloy powder and a C powder which are to be hard particles are blended and kneaded so as to have the above-mentioned composition. In addition, you may mix zinc stearate etc. as a lubricant.
Next, these powders are filled in a mold, and compressed and molded by a molding press to obtain a green compact. Next, the compact is sintered to obtain a sintered body.
[0023]
As for the sintering conditions, it is desirable that the green compact be heated to a temperature range of 1100 to 1200 ° C. in a protective atmosphere and sintered. If the temperature is lower than 1100 ° C., the sintering diffusion is insufficient. If the temperature exceeds 1200 ° C., the hard particles and the matrix are excessively diffused and the wear resistance is deteriorated.
The sintered body is further heated together with the copper alloy for infiltration to a temperature equal to or higher than the melting point of the copper alloy and subjected to infiltration treatment for infiltrating the copper alloy into the pores. This infiltration treatment may be performed simultaneously with the heat treatment of the sintered body described later.
[0024]
Next, in the present invention, after performing the infiltration treatment on the sintered body having the above composition, or without performing the infiltration treatment, a heat treatment of heating and cooling is performed.
In the present invention, the structure of the sintered alloy material is austenite + bainite + granular pearlite structure in order to improve the elongation characteristics of the sintered alloy material to 1.0% or more. Therefore, heat treatment conditions are limited.
[0025]
The heating temperature of the heat treatment is set to a temperature from the _Ac3 or _Acm transformation point of the sintered body to 1200 ° C or less.
If the heating temperature is _lower than the _Ac3 or _Acm transformation point, an austenite + bainite + granular pearlite structure with excellent elongation characteristics cannot be obtained, and a tempered martensite + pearlite structure cannot be obtained, and improvement in elongation value cannot be expected. On the other hand, when the temperature exceeds 1200 ° C., the crystal grains become coarse, and the hard particles and the matrix are excessively diffused, and the ductility, toughness and wear resistance are deteriorated. For this reason, the heating temperature of the heat treatment is set to a temperature equal to or higher than the _Ac3 or _Acm transformation point, and preferably equal to or lower than 1200 ° C. Preferably, it is 750 ° C or more and 1200 ° C or less. The sintered body that has not been subjected to the infiltration treatment may be heated together with the copper alloy for infiltration to a temperature equal to or higher than the melting point of the copper alloy at the time of heating to perform the infiltration treatment at the same time.
[0026]
After heating to the above-mentioned heating temperature, it is cooled to 650 ° C. or less at a cooling rate of 4.5 ° C./min or less, and then air-cooled.
When the cooling rate to 650 ° C. or lower exceeds 4.5 ° C./min, an austenite + bainite + granular pearlite structure having excellent elongation characteristics cannot be obtained, but a martensite + bainite structure is obtained, and a high elongation value is obtained. Absent. If the cooling rate is controlled up to a temperature exceeding 650 ° C., a structure having a predetermined elongation characteristic cannot be obtained.
[0027]
After performing the above-described heat treatment, tempering may be performed as necessary.
By combining the above composition and heat treatment, the elongation characteristics of the sintered alloy material are improved, and even when the sintered alloy material of the present invention is applied to a joint type valve seat, no crack is observed. In addition, it is preferable to apply copper plating to at least the joint surface of the joint valve seat made of the sintered alloy of the present invention from the viewpoint of improving the jointability.
[0028]
The joint type valve seat is formed by processing a sintered alloy material into a predetermined shape, and is joined to a cylinder head by resistance welding, friction welding, electron beam welding, or the like.
[0029]
【Example】
First, test no. 1 to No. 7, no. 13 is a raw material powder in terms of% by weight, C powder (-325 mesh) 1.2%, Co powder (5 μm or less) 6.0%, Ni powder (-325 mesh) 2.0%, Fe-60% Mo Powder (-250 mesh) 1.0%, 2.5% C-1.0% Co-19% W-63.5% Cr-5% Fe alloy powder (-250 mesh) 11.5%, remaining atomized 1% zinc stearate was mixed with pure iron powder and kneaded. Test No. 8 to No. 12 is 1.2% of C powder (−325 mesh), 6.0% of Co powder (5 μm or less), 2.0% of Ni powder (−325 mesh), and 2.5% of C as a raw material powder by weight. -1% of 1.0% Co-19% W-63.5% Cr-5% Fe alloy powder (-250 mesh) and the remaining atomized pure iron powder mixed with 1% of zinc stearate and kneaded. . These mixed raw material powders were compacted at a pressure of 6 ton / cm ² , sintered in a reducing atmosphere at 1110 ° C. for 60 minutes, and a copper alloy for infiltration was placed thereon and subjected to infiltration treatment at 1130 ° C. for 60 minutes. . Some of the sintered bodies (test Nos. 7, 12) were not subjected to the infiltration treatment.
[0030]
Next, the sintered body was heat-treated under the heating and cooling conditions shown in Table 1. Test No. 7, no. In No. 12, a copper alloy for infiltration was placed at the time of heating, and infiltration was performed simultaneously.
[0031]
[Table 1]

[0032]
Test No. 1 to No. The composition of the sintered alloy material of No. 7 is C: 1.3%, Ni: 2.0%, Cr: 7.5%, Mo: 0.6%, W: 2.2%, Co: 7.5. %, The balance of impurities and Fe, and 13% by volume of the hard particles dispersed in the matrix. Test No. 8 to No. The composition of the sintered alloy material of No. 12 was C: 1.3%, Ni: 2.0%, Cr: 7.5%, W: 2.2%, Co: 7.5%, the balance of impurities and Fe. Yes, the hard particles dispersed in the matrix were 12% by volume. Copper alloy was infiltrated into 10 to 15% of the sintered pores. The transformation point (A _cm ) of this sintered alloy material was 735 ° C. After the heat treatment, a tensile test was performed on the sintered alloy material, and the elongation was measured. Table 1 also shows the measurement results.
[0033]
Test No. of the application example of the present invention. 1-3, No. Nos. 5 to 7; 8-9, No. Test Nos. 11 to 12 have an elongation of 1.0% or more, whereas Test No. 4, no. The elongation of each of Test No. 10 was 0.8% and 0.6%, respectively. The elongation of No. 13 is 0.3% and less than 1.0%, which indicates that the application examples of the present invention have excellent elongation characteristics.
Test No. of the application example of the present invention. Test No. 1 of the conventional example. After processing under the same composition and processing conditions as in Example 13 and processing into a valve seat, it was joined to a cylinder head (material: ADC4) by resistance welding. Due to the thermal stress at the time of this joining, the test No. of the application example of the present invention was performed. No crack was observed in the valve seat of No. 1. However, Test No. In the valve seat of No. 13, cracks occurred in the radial direction. Within the scope of the present invention, even when applied to a joint-type valve seat, cracks do not occur due to thermal stress during joining.
[0034]
The heat-treated sintered alloy material shown in Table 1 was processed into a normal press-fit type valve seat, and the wear resistance was confirmed by a simple rig wear test. The test conditions are as follows.
Test temperature: 350 ° C (sheet side)
Number of contacts: 1.6 × 10 ⁶ times Number of cam rotation: 3000 rpm
Valve rotation speed: 20 rpm
Spring load: 30kgf (at the time of lift)
Valve material: SUH35 (Stellite No. 6 metal)
Lift amount: 7.2mm
The test results are shown in FIG.
[0035]
Test No. of the application example of the present invention. 1-3, No. Nos. 5 to 7; 8-9, No. In Nos. 11 to 12, the wear amount of the valve seat was 9 to 11 µm. 13 showed the same abrasion resistance.
[0036]
【The invention's effect】
According to the present invention, a sintered alloy material having excellent elongation and toughness and excellent wear resistance can be obtained. The effect of being able to maintain is obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the amount of valve seat wear after a single rig test.

Claims

% By weight, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, W: 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance consisting of unavoidable impurities and Fe And C-Cr-W-Co-Fe particles of 250 mesh or less having a volume percentage of 8 to 14%, the sintered pores are infiltrated with a copper alloy, and the matrix structure is composed of austenite, bainite and granular pearlite. Do Ri, sintered alloy joined type valve seat, characterized in Rukoto such a sintered alloy material having an elongation of 1.0% or more.

By weight%, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, Mo: 0.1 to 0.9%, W: 1.0 to 3.8%, Co: 4.5 to 8.5%, with the balance being the balance It has 8 to 14% by volume of C-Cr-W-Co-Fe particles and Fe-Mo particles consisting of unavoidable impurities and Fe and having a mesh size of 250 mesh or less. soaked, the base tissue austenite, Ri Do bainite and granular perlite, sintered alloy joined type valve seat, characterized in Rukoto such a sintered alloy material having an elongation of 1.0% or more.

By weight%, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, W: 1.0 to 3.8%, Co: A sintered body containing 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having 8 to 14% by volume of C-Cr-W-Co-Fe particles of 250 mesh or less, The copper alloy is heated together with the copper alloy for infiltration to a temperature higher than the melting point of the copper alloy, the pores are infiltrated with the copper alloy, and further heated to a temperature not lower than the _Ac3 or A _cm transformation point and not higher than 1200 ° C. A method for producing a sintered alloy material for a joined type valve seat having excellent elongation characteristics and abrasion resistance, characterized by cooling to 650 ° C. or lower at a cooling rate of not more than min and then air cooling.

By weight%, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, Mo: 0.1 to 0.9%, W: C-Cr-W-Co-Fe particles containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having a mesh size of 250 mesh or less and Fe- the sintered body having from 8 to 14% by volume% and Mo particles, heated with infiltration copper alloy or a copper alloy melting point, voids infiltrated with copper alloy, further, a _c3 or a _cm transformation A joint type valve seat having excellent elongation characteristics and abrasion resistance, wherein the valve is heated to a temperature not lower than the point and not higher than 1200 ° C., and then cooled at a cooling rate of 4.5 ° C./min or lower to 650 ° C. or lower and air-cooled. Manufacturing method for sintered alloy material.

By weight%, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, W: 1.0 to 3.8%, Co: A sintered body containing 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having 8 to 14% by volume of C-Cr-W-Co-Fe particles of 250 mesh or less, After heating together with the copper alloy for infiltration to a temperature not lower than the _Ac3 or A _cm transformation point and not lower than the melting point of the copper alloy and not higher than 1200 ° C., it is cooled to 650 ° C. or lower at a cooling rate of 4.5 ° C./min and then air-cooled. A method for producing a sintered alloy material for a joined valve seat having excellent elongation characteristics and abrasion resistance.

By weight%, C: 0.5 to 1.7%, Ni: 0.5 to 2.5%, Cr: 3.0 to 8.0%, Mo: 0.1 to 0.9%, W: C-Cr-W-Co-Fe particles containing 1.0 to 3.8%, Co: 4.5 to 8.5%, the balance being unavoidable impurities and Fe, and having a mesh size of 250 mesh or less and Fe- 3. A sintered body having 8 to 14% by volume of Mo particles is heated together with the copper alloy for infiltration to a temperature not lower than the _Ac3 or _Acm transformation point and not lower than the melting point of the copper alloy and not higher than 1200 ° C. A method for producing a sintered alloy material for a joint-type valve seat having excellent elongation characteristics and wear resistance, comprising cooling at a cooling rate of 5 ° C./min or less to 650 ° C. or less and then air cooling.