JP2006249448A - Valve seat made of sintered alloy having wear resistance, strength and excellent machinability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve seat made of a sintered alloy having wear resistance, strength and excellent machinability. <P>SOLUTION: The sintered alloy has a composition consisting of 20-25% Al, 0.1-1.0% C, 0.1-1% MnS or CaCO<SB>3</SB>and the balance Fe with inevitable impurities or further containing 0.1-5%, in total, of one or more selected from Ni, Cu and Mo (hereinafter described as (Ni, Cu, Mo)) if necessary, and has a structure in which MnS or CaCO<SB>3</SB>is uniformly dispersed in an Fe-Al-C solid solution single-phase base material or an Fe-Al-C-(Ni, Cu, Mo) solid solution single-phase base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

この発明は、耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシートに関するものであり、特に低排ガス自動車であるＬＰガスおよびＬＮガス自動車のエンジンに組み込まれた場合に、すぐれた耐摩耗性を長期に亘って発揮する焼結合金製バルブシートに関するものである。   The present invention relates to a valve seat made of a sintered alloy having wear resistance and strength and excellent machinability, and particularly when incorporated in an engine of LP gas and LN gas vehicles which are low exhaust vehicles. The present invention relates to a sintered alloy valve seat that exhibits excellent wear resistance over a long period of time.

従来、各種自動車エンジンのバルブシートとして多くのＦｅ系焼結合金製のものが提案され、中でも質量％（以下、％は質量％を示す）で、
Ａｌ：５〜３０％、
Ｃ ：０．２〜３％、
を含有し、残りがＦｅと不可避不純物からなる組成、およびＦｅ−Ａｌ合金相とＦｅ−Ｃ相の２相混在組織、またはＦｅ−Ａｌ合金相とＦｅ−Ｃ相と炭素（Ｃ）相の３相混在組織を有するＦｅ−Ａｌ−Ｃ焼結合金製バルブシートが注目されている。 Conventionally, many valve seats made of Fe-based sintered alloys have been proposed as valve seats for various automobile engines, and in particular, mass% (hereinafter,% indicates mass%),
Al: 5-30%
C: 0.2-3%,
And the remainder composed of Fe and inevitable impurities, and a two-phase mixed structure of Fe—Al alloy phase and Fe—C phase, or 3 of Fe—Al alloy phase, Fe—C phase and carbon (C) phase. A valve seat made of an Fe—Al—C sintered alloy having a phase mixed structure has attracted attention.

また、上記の従来Ｆｅ−Ａｌ−Ｃ焼結合金製バルブシートは、通常の条件、すなわちアンモニア分解ガスやＲＸ分解ガスなどの雰囲気中、１０５０〜１１５０℃の温度に０．５〜２時間保持の条件で焼結しても、原料粉末として用いられるＦｅ粉末、Ａｌ粉末、および炭素粉末の粉末相互の焼結性が悪いために所定の強度をもった焼結体を製造することができず、このため前記原料粉末を所定の配合組成に配合し、混合し、プレス成形してなる圧粉体に５〜１００Ａ／ｍｍ^２の電流密度で通電プレス成形焼結（プレス圧力は通常１００ＭＰａ）を施すことにより製造されている。
特開２００２−１４６４９５ 特開２００２−１４６４９６ In addition, the above-described conventional Fe—Al—C sintered alloy valve seat is maintained at a temperature of 1050 to 1150 ° C. for 0.5 to 2 hours in an ordinary condition, that is, an atmosphere of ammonia decomposition gas or RX decomposition gas. Even if sintered under the conditions, it is not possible to produce a sintered body having a predetermined strength due to poor sinterability between powders of Fe powder, Al powder, and carbon powder used as raw material powder, For this reason, the above-mentioned raw material powder is blended into a predetermined composition, mixed, and press-molded and sintered (press pressure is usually 100 MPa) at a current density of 5 to 100 A / mm ^{2 on} the green compact formed by press molding. It is manufactured by.
JP 2002-146495 A JP2002-146696

近年、環境負荷低減のため、エンジンには排ガス低減が求められており、この要求を満たすためにガソリンエンジンにはリーンバーン化や直噴射化が進められており、ディーゼルエンジンにおいては筒内圧力の増加、そしてＬＰＧ、ＬＮＧに代表される代替燃料の採用が進められている。
ＬＰＧ燃料は既にタクシーなどでの使用実績があり、最も代替燃料として期待されている燃料であるが、ＬＰＧ燃料はガソリン燃料使用環境に比べて、クリーン燃焼であるために燃焼生成物による潤滑効果が期待できないこと、室内が乾燥状態になり安定な被膜形成が起りにくいこと、排ガス温度が高温になりガソリン燃料の場合排ガス温度は８００℃前後であるがＬＰＧ燃料の場合排ガス温度は９００℃前後に上昇することなどから、エンジンのバルブシートに対しては、
（ａ）排ガス温度が８００℃前後から９００℃前後に上昇するために、バルブシート基地の強度および硬さが低下してバルブシートの耐摩耗性が低下する、
（ｂ）クリーン燃焼であるために燃焼生成物による潤滑効果が期待できず、また室内が乾燥状態になり、バルブと金属接触が発生し易くなる、
（ｃ）バルブとの接触圧が増加する、などの現象が生じ、そのために金属接触が起り易くかつ摩耗が著しく増大するという問題点が発生した。
かかる現象に対して、上記の従来Ｆｅ−Ａｌ−Ｃ焼結合金製バルブシートは、上記の通り２相混在組織および３相混在組織をもちかつ前記構成相のうちのＦｅ−Ｃ相が高温耐酸化性に劣るものであるため、特にＬＰガス自動車のエンジンに組み込まれた場合、前記高温の低排ガスによって前記Ｆｅ−Ｃ相の酸化が相対的に速く進行し、これが原因で摩耗が加速されるようになり、さらに前記２相混在組織および３相混在組織の場合、相境界部の強度が焼結性不足が原因で低いために薄肉化および小径化に十分な強度を確保することができない。 In recent years, in order to reduce the environmental load, the engine has been required to reduce exhaust gas. To meet this demand, gasoline engines are being promoted with lean burn and direct injection. Increasing and adoption of alternative fuels represented by LPG and LNG are being promoted.
LPG fuel has already been used in taxis and the like, and is the fuel that is most expected as an alternative fuel. However, LPG fuel is a clean combustion compared to the environment where gasoline fuel is used. Unexpected, the room is in a dry state and stable film formation is difficult to occur, the exhaust gas temperature is high, the exhaust gas temperature is around 800 ° C for gasoline fuel, the exhaust gas temperature rises to around 900 ° C for LPG fuel For the engine valve seat,
(A) Since the exhaust gas temperature rises from around 800 ° C. to around 900 ° C., the strength and hardness of the valve seat base is lowered, and the wear resistance of the valve seat is lowered.
(B) Since it is clean combustion, the lubrication effect due to the combustion products cannot be expected, and the room is in a dry state, and metal contact with the valve is likely to occur.
(C) A phenomenon such as an increase in the contact pressure with the valve occurs, which causes a problem that metal contact easily occurs and wear significantly increases.
In response to such a phenomenon, the above-described conventional Fe—Al—C sintered alloy valve seat has a two-phase mixed structure and a three-phase mixed structure as described above, and the Fe—C phase of the constituent phases is high-temperature acid resistant In particular, when incorporated in an engine of an LP gas vehicle, the oxidation of the Fe-C phase proceeds relatively fast by the high temperature low exhaust gas, and this accelerates wear. Furthermore, in the case of the two-phase mixed structure and the three-phase mixed structure, the strength of the phase boundary portion is low due to insufficient sinterability, so that sufficient strength for thinning and diameter reduction cannot be ensured.

さらに、上記の従来Ｆｅ−Ａｌ−Ｃ焼結合金製バルブシートは、常温において極めて高い硬度を有するところから、被削性に劣り、上記の従来Ｆｅ−Ａｌ−Ｃ焼結合金製バルブシートを切削により仕上げ加工を行う際に使用する切削工具の消耗が激しく、したがって工具寿命が短くなる、などの課題があった。   Furthermore, the above-mentioned conventional Fe-Al-C sintered alloy valve seat has extremely high hardness at room temperature, so it is inferior in machinability, and the above conventional Fe-Al-C sintered alloy valve seat is cut. As a result, there is a problem that the cutting tool used for finishing is consumed very much and therefore the tool life is shortened.

そこで、本発明者等は、上述のような観点から、従来Ｆｅ−Ａｌ−Ｃ焼結合金製バルブシートに比べて一層の耐摩耗性と強度を向上させ、さらに被削性の改善を図るべく研究を行った。その結果、原料粉末として、Ｆｅ粉末、Ｆｅ−Ａｌ合金粉末（望ましくはＦｅ−５０％Ａｌ合金粉末）、Ｎｉ粉末、Ｃｕ粉末、Ｍｏ粉末、炭素（Ｃ）粉末、ＭｎＳ粉末およびＣａＣＯ_３粉末を用意し、これら原料粉末を成分組成が、
（ｉ）質量％で（以下、％は質量％を示す）、Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＭｎＳまたはＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅ、となるように配合し、通常の条件で混合し、得られた混合粉末をプレス成形して圧粉体を作製し、この圧粉体を真空、望ましくは１０Ｐａ以下の真空中、上記の通常の焼結温度に比して相対的に高い１１５０越え〜１３００℃の温度に１〜３時間保持の条件で焼結すると、製造されたバルブシートは、焼結時にＦｅ中にＡｌ、炭素（Ｃ）が完全に固溶して、Ｆｅ−Ａｌ−Ｃ固溶体単相素地中に、ＭｎＳまたはＣａＣＯ_３が均一分散した組織をもつようになり、この結果得られた焼結合金製バルブシートは、前記Ｆｅ−Ａｌ−Ｃ固溶体単相の素地組織によって耐摩耗性および強度が一段と向上しかつこの素地中にＭｎＳまたはＣａＣＯ_３が均一分散することにより被削性が向上する、
（ii）Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＮｉ，ＣｕおよびＭｏの内の１種または２種以上の合計（以下、（Ｎｉ，Ｃｕ，Ｍｏ）と記す）：０．１〜５％を含有し、さらにＭｎＳまたはＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅ、となるように配合し、通常の条件で混合し、得られた混合粉末をプレス成形して圧粉体を作製し、この圧粉体を真空、望ましくは１０Ｐａ以下の真空中、上記の通常の焼結温度に比して相対的に高い１１５０越え〜１３００℃の温度に１〜３時間保持の条件で焼結すると、製造されたバルブシートは、焼結時にＦｅ中にＡｌ、炭素（Ｃ）および（Ｎｉ，Ｃｕ，Ｍｏ）が完全に固溶して、Ｆｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相素地中に、ＭｎＳまたはＣａＣＯ_３が均一分散した組織をもつようになり、この結果得られた焼結合金製バルブシートは、前記Ｆｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相の素地組織によって耐摩耗性および強度が一段と向上しかつこの素地中にＭｎＳまたはＣａＣＯ_３が均一分散することにより被削性が向上する、という研究結果を得たのである。 In view of the above, the inventors of the present invention aim to further improve wear resistance and strength as compared with conventional valve seats made of Fe-Al-C sintered alloy, and to further improve machinability. I did research. As a result, Fe powder, Fe-Al alloy powder (desirably Fe-50% Al alloy powder), Ni powder, Cu powder, Mo powder, carbon (C) powder, MnS powder and CaCO ₃ powder are prepared as raw powders. The component composition of these raw material powders
(I) By mass% (hereinafter,% represents mass%), Al: 20 to 25%, C: 0.1 to 1.0%, MnS or CaCO ₃ : 0.1 to 1% And the balance is Fe, and mixed under normal conditions. The obtained mixed powder is press-molded to produce a green compact, and the green compact is vacuumed, desirably 10 Pa or less. In a vacuum of 1), when sintered under conditions of holding for 1 to 3 hours at a temperature higher than 1150 to 1300 ° C., which is relatively higher than the above normal sintering temperature, the manufactured valve seat becomes Fe during sintering. Al and carbon (C) are completely dissolved therein, and the Fe-Al-C solid solution single-phase substrate has a structure in which MnS or CaCO ₃ is uniformly dispersed. The gold valve seat is wear resistant by the base structure of the Fe-Al-C solid solution single phase. Machinability is improved by MnS or CaCO ₃ are uniformly dispersed in the further improved and this in the matrix strength and,
(Ii) Al: 20 to 25%, C: 0.1 to 1.0%, and one or more of Ni, Cu and Mo (hereinafter referred to as (Ni, Cu, Mo) )): 0.1 to 5%, further containing MnS or CaCO ₃ : 0.1 to 1%, the remainder being Fe, and mixing under normal conditions to obtain The obtained mixed powder is press-molded to produce a green compact, and this green compact is vacuum, preferably 10 Pa or less, in a vacuum of 10 Pa or less, which is relatively higher than the above normal sintering temperature, exceeding 1150 to 1300. When sintered at a temperature of 1 ° C. for 1 to 3 hours, the produced valve seat has Al, carbon (C) and (Ni, Cu, Mo) completely dissolved in Fe during sintering. , Fe-Al-C- (Ni , Cu, Mo) in the solid solution single-phase matrix, MnS or CaCO ₃ GaHitoshi The sintered alloy valve seat obtained as a result of this has a further improved wear resistance and strength due to the single-phase base structure of the Fe-Al-C- (Ni, Cu, Mo) solid solution. The research result that the machinability is improved by the improvement and uniform dispersion of MnS or CaCO ₃ in the substrate is obtained.

この発明は、上記の研究結果に基づいてなされたものであって、
（１）Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＭｎＳ：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ固溶体単相素地中にＭｎＳが均一分散している組織を有するＦｅ−Ａｌ−Ｃ−ＭｎＳ焼結合金で構成してなる耐摩耗性および強度を有しかつ被削性に優れたＦｅ−Ａｌ−Ｃ系焼結合金製バルブシート、
（２）Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ固溶体単相素地中にＣａＣＯ_３が均一分散している組織を有するＦｅ−Ａｌ−Ｃ−ＣａＣＯ_３焼結合金で構成してなる耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート、
（３）Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらに（Ｎｉ，Ｃｕ，Ｍｏ）：０．１〜５％を含有し、さらにＭｎＳ：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相素地中にＭｎＳが均一分散している組織を有するＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）−ＭｎＳ焼結合金で構成してなる耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート、
（４）Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらに（Ｎｉ，Ｃｕ，Ｍｏ）：０．１〜５％を含有し、さらにＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相素地中にＣａＣＯ_３が均一分散している組織を有するＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）−ＣａＣＯ_３焼結合金で構成してなる耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート、に特徴を有するものである。 This invention was made based on the above research results,
(1) Al: 20 to 25%, C: 0.1 to 1.0%, further MnS: 0.1 to 1%, the remainder comprising Fe and inevitable impurities, and Fe- Fe with wear resistance and strength composed of a Fe-Al-C-MnS sintered alloy having a structure in which MnS is uniformly dispersed in an Al-C solid solution single-phase substrate and excellent machinability -Valve seat made of Al-C sintered alloy,
(2) Al: 20~25%, C: contains 0.1% to 1.0%, further CaCO _3: contains 0.1% to 1%, the composition balance being Fe and inevitable impurities, and Fe -Abrasion resistance and strength composed of a sintered alloy of Fe-Al-C-CaCO ₃ having a structure in which CaCO ₃ is uniformly dispersed in an Al-C solid solution single-phase substrate and machinability Excellent sintered alloy valve seat,
(3) Al: 20 to 25%, C: 0.1 to 1.0%, further (Ni, Cu, Mo): 0.1 to 5%, MnS: 0.1 to 0.1% Fe-Al- having a composition containing 1%, the remainder consisting of Fe and inevitable impurities, and a structure in which MnS is uniformly dispersed in a Fe-Al-C- (Ni, Cu, Mo) solid solution single phase matrix A valve seat made of a sintered alloy having wear resistance and strength composed of a C- (Ni, Cu, Mo) -MnS sintered alloy and having excellent machinability;
(4) Al: 20~25%, C: contains 0.1% to 1.0%, further (Ni, Cu, Mo): contains 0.1% to 5%, more CaCO _3: 0.1 Fe- having a composition containing ~ 1%, the remainder consisting of Fe and inevitable impurities, and a structure in which CaCO ₃ is uniformly dispersed in a single-phase body of Fe-Al-C- (Ni, Cu, Mo) solid solution A valve seat made of a sintered alloy having wear resistance and strength composed of an Al-C- (Ni, Cu, Mo) -CaCO ₃ sintered alloy and having excellent machinability. is there.

つぎに、この発明のバルブシートを構成する焼結合金の組成を上記の通りに限定した理由を説明する。
Ａｌ：
Ａｌは、高温耐酸化性を向上させる成分であるが、Ａｌ成分の含有割合が２０％未満では所望のすぐれた高温耐酸化性を確保することができず、一方その含有割合が２５％を越えると、焼結時のＦｅへの完全固溶が困難となり、強度および高温耐酸化性低下の原因となる２相混在組織および３相混在組織が出現するようになることから、Ａｌ成分の含有割合を２０〜２５％と定めた。
Ｃ：
Ｃ成分には、素地の硬さを向上させ、もってバルブシートの耐摩耗性を向上させる作用があるが、その含有割合が０．１％未満では所望の硬さ向上効果が得られず、一方その含有量が１％を越えると素地の硬さが大きくなって被削性が低下すると共に、Ａｌの場合と同様に焼結時のＦｅへの完全固溶が困難となり、２相混在組織および３相混在組織となって、強度および耐摩耗性が急激に低下するようになることから、Ｃ成分の含有割合を０．１〜１％と定めた。
ＭｎＳ、ＣａＣＯ_３：
これら成分は、素地中に分散または粒界に存在して被削性を改善する作用を有するので含有させるが、これら成分は０．１％未満含有してもその量が少なく、したがって所望の効果が得られず、一方、１％を越えて含有すると焼結合金の機械的強度が劣化すると共に耐摩耗性が急激に低下するようになることから、これら成分の含有量は０．１〜１％と定めた。
これら成分の内でも、ＭｎＳは１２００℃以上になると分解してＭｎＳとして存在できなくなることから、この発明のＭｎＳを含む焼結合金バルブシートは１２００℃未満の温度範囲で使用するバルブシートに適しており、一方、この発明のＣａＣＯ_３を含むバルブシートは１２００℃以上の温度範囲で使用するバルブシートに適している。
Ｎｉ，Ｃｕ，Ｍｏ：
これら成分は、基地を固溶強化してバルブシートの特性を一層向上させる作用を有するので必要に応じて含有させるが、Ｎｉ，Ｃｕ，Ｍｏの内の１種または２種以上を合計で０．１％未満含有しても所望の効果が得られず，一方，５％を越えて含有するとＮｉ相、Ｃｕ相、Ｍｏ相が出現するようになって固溶体単相組織とならず、強度および耐摩耗性が急激に低下するようになることから、Ｎｉ，Ｃｕ，Ｍｏの内の１種または２種以上の合計を０．５〜５％と定めた。 Next, the reason why the composition of the sintered alloy constituting the valve seat of the present invention is limited as described above will be described.
Al:
Al is a component that improves high-temperature oxidation resistance. However, if the content ratio of the Al component is less than 20%, the desired excellent high-temperature oxidation resistance cannot be ensured, while the content ratio exceeds 25%. And, since it becomes difficult to completely dissolve in Fe during sintering, a two-phase mixed structure and a three-phase mixed structure that cause a decrease in strength and high-temperature oxidation resistance will appear. Of 20-25%.
C:
The component C has the effect of improving the hardness of the substrate and thus improving the wear resistance of the valve seat, but if the content ratio is less than 0.1%, the desired hardness improvement effect cannot be obtained. If its content exceeds 1%, the hardness of the substrate increases and machinability decreases, and as in the case of Al, complete solid solution in Fe during sintering becomes difficult, and a two-phase mixed structure and Since it becomes a three-phase mixed structure and strength and wear resistance are rapidly lowered, the content ratio of the C component is set to 0.1 to 1%.
MnS, CaCO ₃ :
These components are contained in the substrate because they have the action of improving the machinability by being dispersed or present at the grain boundaries, but even if these components are contained in less than 0.1%, the amount thereof is small, so the desired effect On the other hand, if the content exceeds 1%, the mechanical strength of the sintered alloy deteriorates and the wear resistance suddenly decreases. %.
Among these components, MnS decomposes when it reaches 1200 ° C. or higher and cannot exist as MnS. Therefore, the sintered alloy valve seat containing MnS of the present invention is suitable for a valve seat used in a temperature range of less than 1200 ° C. On the other hand, the valve seat containing CaCO ₃ of the present invention is suitable for a valve seat used in a temperature range of 1200 ° C. or higher.
Ni, Cu, Mo:
These components have the effect of solid solution strengthening the base to further improve the characteristics of the valve seat. Therefore, these components are contained as necessary, but one or more of Ni, Cu, and Mo are added in a total amount of 0.00. If the content is less than 1%, the desired effect cannot be obtained. On the other hand, if the content exceeds 5%, a Ni phase, a Cu phase, and a Mo phase appear and a solid solution single-phase structure is not formed. Since the wear properties are rapidly reduced, the total of one or more of Ni, Cu, and Mo is set to 0.5 to 5%.

この発明の焼結合金製バルブシートは、原料粉末として、Ｆｅ粉末、Ｆｅ−Ａｌ合金粉末、Ｎｉ粉末、Ｃｕ粉末、Ｍｏ粉末、炭素（Ｃ）粉末、ＭｎＳ粉末およびＣａＣＯ_３粉末を用意し、これら原料粉末を成分組成が前記（１）〜（４）に記載されている成分組成となるように配合し、通常の条件で混合し、得られた混合粉末をプレス成形して圧粉体を作製し、この圧粉体を真空、望ましくは１０Ｐａ以下の真空中、上記の通常の焼結温度に比して相対的に高い１１５０越え〜１３００℃の温度に１〜３時間保持の条件で焼結することにより製造することができる。 The sintered alloy valve seat of this invention is prepared with Fe powder, Fe-Al alloy powder, Ni powder, Cu powder, Mo powder, carbon (C) powder, MnS powder and CaCO ₃ powder as raw material powders. The raw material powder is blended so that the component composition becomes the component composition described in the above (1) to (4), mixed under normal conditions, and the obtained mixed powder is press-molded to produce a green compact. The green compact is sintered in a vacuum, desirably 10 Pa or less, at a temperature higher than 1150 to 1300 ° C., which is relatively higher than the normal sintering temperature, for 1 to 3 hours. Can be manufactured.

この発明の焼結合金製バルブシートは、被削性に優れるので切削工具の消耗を減らしつつ精密な切削加工を行うことができ、さらに耐摩耗性および強度を有することから、特に低排ガス自動車であるＬＰガス自動車のエンジンに組み込まれた場合に、自動車の高速化および高出力化に伴ない、排ガスが９００℃前後の高温に達するにもかかわらず、すぐれた耐摩耗性を長期に亘って発揮し、かつ薄肉化および小径化を可能とするものである。   The valve seat made of a sintered alloy according to the present invention is excellent in machinability, so that it can perform precise cutting while reducing wear of the cutting tool, and further has wear resistance and strength. When incorporated in an engine of a certain LP gas vehicle, it exhibits excellent wear resistance over a long period of time despite the fact that the exhaust gas reaches a high temperature of around 900 ° C as the speed of the vehicle increases and the output increases. In addition, it is possible to reduce the thickness and diameter.

つぎに、この発明の焼結合金製バルブシートを実施例により具体的に説明する。
原料粉末として、−１５０メッシュの還元鉄粉末、−１５０メッシュのＦｅ−５０％Ａｌ合金粉末、数μｍのＮｉ粉末、−２００メッシュのＣｕ粉末、数μｍのＭｏ粉末、平均粒径：１０μｍの炭素（Ｃ）粉末、平均粒径：１０μｍのＭｎＳ粉末および平均粒径：１μｍのＣａＣＯ_３粉末を用意し、さらに潤滑材としてのステアリン酸亜鉛を用意した。 Next, the sintered alloy valve seat of the present invention will be described in detail with reference to examples.
As raw material powder, -150 mesh reduced iron powder, -150 mesh Fe-50% Al alloy powder, several μm Ni powder, -200 mesh Cu powder, several μm Mo powder, average particle size: 10 μm carbon (C) MnS powder having an average particle size of 10 μm and CaCO ₃ powder having an average particle size of 1 μm were prepared, and zinc stearate as a lubricant was prepared.

前記用意した原料粉末を表１〜２に示される配合組成に配合し、潤滑材として前記配合粉末に対する割合で０．８％のステアリン酸亜鉛を加えてミキサーにて３０分間混合し、０．７Ｐａの圧力でリング状成形体にプレス成形し、この成形体を、３Ｐａの真空中、４００℃に２０分間保持の条件で加熱して前記潤滑材を除去した後、同じく３Ｐａの真空中、通常の焼結温度に比して相対的に高い１２５０℃に１．５時間保持の条件で真空高温焼結することにより外径：３９．２ｍｍ×内径：２８．０ｍｍ×高さ：１０ｍｍの寸法を有し、表３〜４に示される本発明焼結合金製バルブシート（以下、本発明バルブシートという）１〜２０および比較焼結合金製バルブシート（以下、比較バルブシートという）１〜７と同じ成分組成を有するリング状試験片を作製した。   The prepared raw material powder is blended in the blending composition shown in Tables 1 and 2, 0.8% zinc stearate is added as a lubricant in a ratio to the blended powder, and mixed in a mixer for 30 minutes, 0.7 Pa The molded product was press-molded into a ring-shaped molded body at a pressure of 3 Pa, and the molded body was heated in a condition of holding at 400 ° C. for 20 minutes in a vacuum of 3 Pa to remove the lubricant. By vacuum high-temperature sintering at 1250 ° C., which is relatively higher than the sintering temperature for 1.5 hours, the outer diameter is 39.2 mm, the inner diameter is 28.0 mm, and the height is 10 mm. The same as the present invention sintered alloy valve seats (hereinafter referred to as the present invention valve seats) 1-20 and comparative sintered alloy valve seats (hereinafter referred to as the comparative valve seats) 1-7 shown in Tables 3-4. Ring with component composition A test specimen was prepared.

また、比較の目的で、原料粉末として、−１５０メッシュの還元鉄粉末、平均粒径：２０μｍのＡｌ粉末および平均粒径：１０μｍの炭素（Ｃ）粉末を用い、これら原料粉末を表３に示される配合組成に配合し、潤滑材として前記配合粉末に対する割合で０．８％のステアリン酸亜鉛を加えてミキサーにて３０分間混合し、０．７Ｐａの圧力でリング状成形体にプレス成形し、この成形体を、同じ条件で脱潤滑材処理した後、１００ＭＰａの圧力を加えながら２５Ａ／ｍｍ^２の電流密度で３秒間保持の条件で通電プレス成形焼結することにより外径：３９．２ｍｍ×内径：２８．０ｍｍ×高さ：１０ｍｍの寸法を有し、表４に示される従来焼結合金製バルブシート（以下、従来バルブシートという）１と同じ成分組成を有するリング状試験片を作製した。
さらに、三菱マテリアル（株）製のＣＢＮ ＭＢ７１０の切削工具を用意した。 For comparison purposes, -150 mesh reduced iron powder, Al powder having an average particle size of 20 μm, and carbon (C) powder having an average particle size of 10 μm were used as raw material powder. These raw material powders are shown in Table 3. Blended into the blended composition, added 0.8% zinc stearate as a lubricant to the blended powder, mixed for 30 minutes with a mixer, press-molded into a ring-shaped molded body at a pressure of 0.7 Pa, This molded body was treated with a delubricating material under the same conditions, and then subjected to current press molding and sintering under the condition of holding at a current density of 25 A / mm ² for 3 seconds while applying a pressure of 100 MPa, so that the outer diameter was 39.2 mm × A ring-shaped test piece having an inner diameter: 28.0 mm × height: 10 mm, and having the same component composition as a conventional sintered alloy valve seat (hereinafter referred to as a conventional valve seat) 1 shown in Table 4. It was manufactured.
Furthermore, a cutting tool of CBN MB710 manufactured by Mitsubishi Materials Corporation was prepared.

先に用意した本発明バルブシート１〜２０、比較バルブシート１〜７および従来バルブシート１と同じ成分組成を有するリング状試験片をワーク回転速度：１０００ｒｐｍ、周速度：１０５ｍ／ｍｉｎとなる条件で回転させ、この回転しているリング状試験片の外周に当て、切削工具をリング状試験片の半径方向に、
送り速度：０．０７５ｍｍ／ｒｅｖ．
切削油：なし（ドライ）、
の条件で移動させ、リング状試験片のエンドフェイスを厚さ：０．５ｍｍの深さで切削し、その時の切削工具の摩耗量を測定し、その結果を表３〜４に示すことによりリング状試験片の被削性を評価した。
さらに、本発明バルブシート１〜２０、比較バルブシート１〜７および従来バルブシート１と同じ成分組成を有するリング状試験片について、その組織を金属顕微鏡を用いて観察し、その結果を表３〜４に示した。
さらに、本発明バルブシート１〜２０、比較バルブシート１〜７および従来バルブシート１と同じ成分組成を有するリング状試験片のビッカース硬さを測定し、その結果を表３〜４に示した。
さらに、強度を評価する目的で本発明バルブシート１〜２０、比較バルブシート１〜７および従来バルブシート１と同じ成分組成を有するリング状試験片の圧環強度を測定し、その結果も表３〜４に示した。 The ring-shaped test piece having the same component composition as the valve seats 1 to 20 of the present invention, the comparative valve seats 1 to 7 and the conventional valve seat 1 prepared in advance is used under the conditions that the workpiece rotational speed is 1000 rpm and the peripheral speed is 105 m / min. Rotate and place it on the outer periphery of the rotating ring-shaped specimen, and put the cutting tool in the radial direction of the ring-shaped specimen.
Feed rate: 0.075 mm / rev.
Cutting oil: None (dry)
The end face of the ring-shaped test piece was cut at a depth of 0.5 mm, and the amount of wear of the cutting tool at that time was measured. The machinability of the test piece was evaluated.
Furthermore, about the ring-shaped test piece which has the same component composition as this invention valve seat 1-20, comparative valve seat 1-7, and the conventional valve seat 1, the structure | tissue is observed using a metal microscope, The result is shown in Table 3- This is shown in FIG.
Furthermore, the Vickers hardness of the ring-shaped test piece which has the same component composition as this invention valve seat 1-20, comparative valve seat 1-7, and the conventional valve seat 1 was measured, and the result was shown to Tables 3-4.
Further, for the purpose of evaluating the strength, the crushing strength of the ring-shaped test piece having the same component composition as the valve seats 1 to 20 of the present invention, the comparative valve seats 1 to 7 and the conventional valve seat 1 was measured. This is shown in FIG.

次に、上記の本発明バルブシート１〜２０、比較バルブシート１〜７および従来バルブシート１と同じ成分組成を有するリング状試験片を、それぞれ排気量：５０００ｃｃのＬＰガス自動車のエンジンにバルブシートとして組み込み、
回転数：３０００ｒｐｍ、
相手材(バルブ)：ＪＩＳ・ＳＵＨ３５（耐熱鋼）製本体にステライト１２を１ｍｍの厚さで肉盛りしたもの、
試験時間：２００時間、
の条件で実機高速運転摩耗試験を行い、試験後、最大摩耗深さを測定すると共に、相手材であるバルブの最大摩耗深さも測定した。この結果も表３〜４に示した。 Next, the ring-shaped test pieces having the same composition as those of the present invention valve seats 1 to 20, comparative valve seats 1 to 7 and the conventional valve seat 1 are respectively applied to an engine of an LP gas vehicle having a displacement of 5000 cc. Embedded as
Rotational speed: 3000rpm,
Counterpart material (valve): A JIS / SUH35 (heat-resistant steel) body with Stellite 12 being 1 mm thick,
Test time: 200 hours
The actual machine high-speed operation wear test was performed under the conditions described above. After the test, the maximum wear depth was measured, and the maximum wear depth of the counterpart valve was also measured. The results are also shown in Tables 3-4.

表１〜４に示される結果から、本発明バルブシート１〜２０と同じ成分組成を有し単相組織を有するリング状試験片は、従来バルブシート１と同じ成分組成を有し通電プレス成形燒結して得られた２相混在組織を有するリング状試験片よりも工具摩耗量が小さいことから、本発明バルブシート１〜２０は被削性に優れていることがわかる。
さらに本発明バルブシート１〜２０と同じ成分組成を有し単相組織を有するリング状試験片は、硬さを有するので優れた耐摩耗性を有しかつ優れた強度を有するので特に低排ガス自動車であるＬＰガス自動車のエンジンに組み込まれた場合に、自動車の高速化および高出力化に伴ない、排ガスが９００℃前後の高温に達するにもかかわらず、極めて小さい相手攻撃性で、すぐれた耐摩耗性を長期に亘って発揮するのに対して、通電プレス成形燒結して得られた２相混在組織を有する従来バルブシート１は相手攻撃性が大きく、さらに強度および耐摩耗性が不足することがわかる。
また、ＭｎＳまたはＣａＣＯ_３をこの発明の範囲を越えて含有する比較バルブシート１〜２のリング状試験片は、いずれも強度が不足するようになり、さらに真空燒結してもこの発明の条件から外れた組成を有し２相混在組織を有する比較バルブシート３〜７は、強度および耐摩耗性が不足するなどして前記の苛酷な使用条件下では、比較的短時間で使用寿命に至ることが分かる。 From the results shown in Tables 1 to 4, the ring-shaped test piece having the same component composition as the valve seats 1 to 20 of the present invention and having a single-phase structure has the same component composition as the conventional valve seat 1 and is subjected to electric press molding. Since the amount of tool wear is smaller than that of the ring-shaped test piece having a two-phase mixed structure obtained in this way, it can be seen that the present valve seats 1 to 20 are excellent in machinability.
Furthermore, the ring-shaped test piece having the same component composition as the valve seats 1 to 20 of the present invention and having a single phase structure has hardness, and therefore has excellent wear resistance and excellent strength, so that it is particularly low exhaust gas automobile. When incorporated in an LP gas vehicle engine, the exhaust gas reaches a high temperature of around 900 ° C as the speed of the vehicle increases and the output increases. The conventional valve seat 1 having a two-phase mixed structure obtained by sintering by electrification press molding, while exhibiting wearability for a long period of time, has great opponent attack and lacks strength and wear resistance. I understand.
Moreover, the ring-shaped test pieces of the comparative valve seats 1 and 2 containing MnS or CaCO ₃ beyond the scope of the present invention are all insufficient in strength. Comparative valve seats 3 to 7 having an out-of-composition composition and a two-phase mixed structure can reach a service life in a relatively short time under the above severe use conditions due to insufficient strength and wear resistance. I understand.

Claims (4)

質量％で、Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＭｎＳ：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ固溶体単相素地中にＭｎＳが均一分散している組織を有するＦｅ−Ａｌ−Ｃ−ＭｎＳ焼結合金で構成してなることを特徴とする耐摩耗性および強度を有しかつ被削性に優れたＦｅ−Ａｌ−Ｃ系焼結合金製バルブシート。 In mass%, Al: 20 to 25%, C: 0.1 to 1.0%, MnS: 0.1 to 1%, and the remainder composed of Fe and inevitable impurities, and Fe -Abrasion resistance and strength characterized by comprising an Fe-Al-C-MnS sintered alloy having a structure in which MnS is uniformly dispersed in an Al-C solid solution single phase matrix Valve seat made of Fe-Al-C sintered alloy with excellent machinability. 質量％で、Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ固溶体単相素地中にＣａＣＯ_３が均一分散している組織を有するＦｅ−Ａｌ−Ｃ−ＣａＣＯ_３焼結合金で構成してなることを特徴とする耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート。 A composition containing Al: 20 to 25%, C: 0.1 to 1.0%, further containing CaCO ₃ : 0.1 to 1%, with the remainder consisting of Fe and inevitable impurities, and Fe-Al-C-CaCO ₃ sintered alloy having a structure in which CaCO ₃ is uniformly dispersed in an Fe-Al-C solid solution single-phase substrate, and having wear resistance and strength. A sintered alloy valve seat with excellent machinability. 質量％で、Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＮｉ，ＣｕおよびＭｏの内の１種または２種以上の合計（以下、（Ｎｉ，Ｃｕ，Ｍｏ）と記す）：０．１〜５％を含有し、さらにＭｎＳ：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相素地中にＭｎＳが均一分散している組織を有するＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）−ＭｎＳ焼結合金で構成してなることを特徴とする耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート。 In mass%, Al: 20 to 25%, C: 0.1 to 1.0%, and one or more of Ni, Cu and Mo (hereinafter referred to as (Ni, Cu, Mo)): 0.1 to 5%, further MnS: 0.1 to 1%, the remainder comprising Fe and inevitable impurities, and Fe-Al-C- (Ni, Cu) , Mo) Abrasion resistance characterized by comprising a Fe—Al—C— (Ni, Cu, Mo) —MnS sintered alloy having a structure in which MnS is uniformly dispersed in a solid solution single phase substrate. And a sintered alloy valve seat with high strength and excellent machinability. 質量％で、Ａｌ：２０〜２５％、Ｃ：０．１〜１．０％を含有し、さらにＮｉ，ＣｕおよびＭｏの内の１種または２種以上の合計（以下、（Ｎｉ，Ｃｕ，Ｍｏ）と記す）：０．１〜５％を含有し、さらにＣａＣＯ_３：０．１〜１％を含有し、残りがＦｅと不可避不純物からなる組成、並びにＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）固溶体単相素地中にＣａＣＯ_３が均一分散している組織を有するＦｅ−Ａｌ−Ｃ−（Ｎｉ，Ｃｕ，Ｍｏ）−ＣａＣＯ_３焼結合金で構成してなることを特徴とする耐摩耗性および強度を有しかつ被削性に優れた焼結合金製バルブシート。 In mass%, Al: 20 to 25%, C: 0.1 to 1.0%, and one or more of Ni, Cu and Mo (hereinafter referred to as (Ni, Cu, Mo)): 0.1 to 5%, further CaCO ₃ : 0.1 to 1%, the remainder consisting of Fe and inevitable impurities, and Fe—Al—C— (Ni, It is characterized by comprising a sintered alloy of Fe—Al—C— (Ni, Cu, Mo) —CaCO ₃ having a structure in which CaCO ₃ is uniformly dispersed in a single phase matrix of (Cu, Mo) solid solution. A sintered alloy valve seat with wear resistance and strength, and excellent machinability.