【発明の詳細な説明】[Detailed description of the invention]
この発明は、7.0ｇ／cm3以上の高密度および高
強度、さらにすぐれた耐摩耗性、耐熱性、耐食
性、および耐酸化性を有し、特に多様化、小型
化、および高性能化がはかられつつある内燃機関
の弁座として用いた場合にすぐれた性能（耐久
性）を発揮するFe基焼結合金に関するものであ
る。
近年、内燃機関の弁座の製造に焼結合金が多用
されるようになつてきた。これは、焼結合金が高
い生産性（経済性）をもつほか、焼結合金のもつ
特有の組織や多孔が内燃機関弁座の性能に有効に
作用することによるものである。
しかしながら、最近の内燃機関の多様化、小型
化、および高性能化に伴い、弁座の使用条件も
増々苛酷になりつつあり、この場合従来焼結合金
製弁座では焼結合金のもつ多孔が、逆に障害とな
つて所望の耐久性を示さないものである。
そこで、焼結合金製弁座における耐久性劣化の
原因となる多孔を、コイニングや、熱間あるいは
冷間鍛造などによりつぶして密度を上げたり、さ
らにはこの多孔中にCuやPbなどを含浸させたり
して耐久性向上をはかる試みもなされているが、
これらの方法はいずれもコストアツプをまねき、
経済性において問題がある。
本発明者等は、上述のような観点から、コスト
アツプの原因となるコイニングや、鍛造加工、さ
らには金属含浸などの密度向上手段を必要とする
ことなく、焼結ままの状態で高密度を有し、かつ
苛酷な使用条件下でもすぐれた耐久性（性能）を
発揮する内燃機関の弁座を得べく、材料面から研
究を行なつた結果、重量％で、
Ｃ：0.5〜２％、Mo：3.5〜13％、
Ni：６〜12％、Cr：１〜６％、
Co：0.1〜５％、Cu：0.1〜５％、
を含有し、さらに必要に応じて、
Ｓ：0.05〜0.4％、
を含有し、残りがFeと不可避不純物からなる組
成を有するFe基焼結合金は、焼結ままの状態で
7.0ｇ／cm3以上の高密度および高強度を有し、さ
らにすぐれた耐摩耗性、耐熱性、耐食性、および
耐酸化性を有し、したがつてこのFe基焼結合金
を内燃機関の弁座の製造に用いると、この結果の
弁座は苛酷な使用条件下でもすぐれた耐久性（性
能）を示すという知見を得たのである。
この発明は上記知見にもとづいてなされたもの
であつて、以下に成分組成範囲を上記の通りに限
定した理由を説明する。
(a) Ｃ
Ｃ成分には、素地に固溶して、これを強化する
ほか、炭化物を形成して耐摩耗性を向上させる作
用があるが、その含有量が0.5％未満では前記作
用に所望の効果が得られず、一方2.0％を越えて
含有させると、圧粉体の成形性が劣化するように
なると共に、焼結合金の被削性も悪化し、さらに
脆化傾向が現われ、かつ相手材たる弁への攻撃性
が増すようになることから、その含有量を0.5〜
2.0％と定めた。
(b) Mo
Mo成分には、Ｃ成分と結合して炭化物を形成
し、耐摩耗性を向上させる作用があるほか、素地
に固溶して耐熱性および耐食性を向上させる作用
があるが、その含有量が3.5％未満では前記作用
に所望の効果が得られず、一方13.0％を越えて含
有させても前記作用により一層の向上効果は現わ
れず、むしろ密度および強度に低下傾向が現われ
るようになることから、経済性をも考慮して、そ
の含有量を3.5〜13.0％と定めた。
(c) Ni
Ni成分は密度を著しく向上させ、焼結合金が
7.0ｇ／cm3以上の高密度をもつようにするには不
可欠の成分であり、さらにこの成分には強度およ
び耐熱性を向上させる作用があるが、その含有量
が６％未満では7.0ｇ／cm3以上の高密度を確保す
ることができないばかりでなく、強度および耐熱
性も不十分であり、一方12％を越えて含有させて
もより一層の顕著な向上効果が現われず、むしろ
粘さが増して被削性が劣化するようになることか
ら、その含有量を６〜12％と定めた。
(d) Cr
Cr成分には、Moと同様Ｃ成分と結合して炭化
物を形成し、もつて耐摩耗性を向上させる作用が
あるほか、素地に固溶して耐食性および耐酸化性
を向上させる作用があるが、その含有量が１％未
満では前記作用に所望の効果が得られず、一方６
％を越えて含有させると、密度が7.0ｇ／cm3以下
となつて強度が低下するほか、硬さが上昇して相
手攻撃性が増すようになることから、その含有量
を１〜６％と定めた。
(e) Co
Co成分には素地に固溶して耐熱性（赤熱硬さ）
を向上させる作用があるが、その含有量が0.1％
未満では所望の耐熱性向上効果を得ることができ
ず、一方５％を越えて含有させてもより一層の向
上効果が現われず、経済性を考慮して、その含有
量を0.1〜６％と定めた。
(f) Cu
Cu成分には、その一部が素地に固溶して耐銹
性を向上させるほか、焼結性を促進させて密度を
上昇させ、さらに熱伝導性および耐溶着性をも向
上させる作用があり、この作用はNiとの共存に
おいて一段と顕著になるが、その含有量が0.1％
未満では前記作用に所望の向上効果が得られず、
一方５％を越えて含有させると、耐摩耗性が低下
するほか、結晶粒の粗大化をきたして相手材たる
弁の摩耗が増加するようになることから、その含
有量を0.1〜５％と定めた。
(g) Ｓ
Ｓ成分には合金の被削性を改善すると共に、相
手材たる弁とのなじみ性を向上させる作用があ
り、特にこれらの作用はCoとの共存において顕
著に現われるようになることから、これらの特性
が要求される場合に必要に応じて含有されるが、
その含有量が0.05％未満では前記作用に所望の向
上効果が得られず、一方0.40％を越えて含有させ
ると強度が低下するようになることから、その含
有量を0.05〜0.40％と定めた。なお、望ましくは
0.1〜0.2％の含有が好ましい。
つぎに、この発明のFe基焼結合金を実施例に
より具体的に説明する。
実施例
原料粉末として、粒度：−100meshのアトマイ
ズ鉄粉、同−100meshのFe―Cr合金（Cr：12％）
粉末、同−100meshの炭素粉末、同−400meshの
カーボニルNi粉末、同−200meshのFe―Mo合金
（Mo：58％含有）粉末、同−200meshのCo粉末、
同−250meshのCu粉末、および同−100meshの
Fe―Ｓ合金（Ｓ：１％含有）粉末を用意し、こ
れら原料粉末をそれぞれ第１表に示される配合組
成に配合し、マイニユートミキサにて15分間混合
した後、6ton／cm2の圧力にて弁座形状の圧粉体に
成形し、ついでこの圧粉体を、それぞれ水素雰囲
気中、1140〜1180℃の温度範囲内の温度に１時間
保持の条件で焼結することによつて、実質的に配
合組成と同一の最終成分組成をもつた本発明焼結
合金製弁座１〜16、比較焼結合金製弁座１〜９、
および従来内燃機関の弁座として多用されている
従来焼結合金製弁座をそれぞれ製造した。
なお、比較焼結合金製弁座１〜９は、いずれも
構成成分のうちのいずれかの成分含有量（第１表
に※印を付したもの）がこの発明の範囲から外れ
た組成をもつものである。
ついで、この結果得られた本発明焼結合金製弁
座１〜16、比較焼結合金製弁座１〜９、およ
This invention has high density and high strength of 7.0 g/cm 3 or more, as well as excellent wear resistance, heat resistance, corrosion resistance, and oxidation resistance, and is particularly suitable for diversification, miniaturization, and high performance. This invention relates to Fe-based sintered alloys that exhibit excellent performance (durability) when used as valve seats in internal combustion engines, which are becoming increasingly popular. In recent years, sintered alloys have come into widespread use in the manufacture of valve seats for internal combustion engines. This is because, in addition to the high productivity (economic efficiency) of sintered alloys, the unique structure and porosity of sintered alloys have an effective effect on the performance of internal combustion engine valve seats. However, with the recent diversification, miniaturization, and high performance of internal combustion engines, the operating conditions for valve seats are becoming increasingly severe. On the contrary, it becomes a hindrance and does not exhibit the desired durability. Therefore, the pores that cause durability deterioration in sintered metal valve seats are crushed by coining, hot or cold forging, etc. to increase their density, and furthermore, the pores are impregnated with Cu, Pb, etc. Attempts have been made to improve durability by
All of these methods lead to increased costs;
There is a problem in terms of economy. From the above-mentioned viewpoint, the present inventors have achieved high density in the as-sintered state without requiring density-improving means such as coining, forging, or even metal impregnation, which would increase costs. In order to obtain a valve seat for an internal combustion engine that exhibits excellent durability (performance) even under harsh operating conditions, we conducted research from a material perspective, and found that, in weight percent, C: 0.5 to 2%, Mo :3.5-13%, Ni: 6-12%, Cr: 1-6%, Co: 0.1-5%, Cu: 0.1-5%, and if necessary, S: 0.05-0.4%. , and the remainder is Fe and unavoidable impurities in the as-sintered state.
This Fe-based sintered alloy has a high density of 7.0 g/cm3 or more and high strength, as well as excellent wear resistance, heat resistance, corrosion resistance, and oxidation resistance. When used in the manufacture of valve seats, they found that the resulting valve seats exhibit excellent durability (performance) even under severe usage conditions. This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below. (a) C The C component has the effect of forming a solid solution in the base material and strengthening it, as well as forming carbides and improving wear resistance, but if its content is less than 0.5%, the desired effect may not be achieved. On the other hand, if the content exceeds 2.0%, the formability of the green compact will deteriorate, the machinability of the sintered alloy will also deteriorate, and a tendency towards embrittlement will appear. Since the aggressiveness towards the valve, which is the mating material, increases, the content should be reduced to 0.5~
It was set at 2.0%. (b) Mo The Mo component has the effect of combining with the C component to form carbide and improving wear resistance, and also has the effect of solid dissolving in the base material and improving heat resistance and corrosion resistance. If the content is less than 3.5%, the desired effect cannot be obtained in the above-mentioned action, and on the other hand, if the content exceeds 13.0%, no further improvement effect will appear due to the above-mentioned action, but rather a tendency to decrease in density and strength will appear. Therefore, considering economic efficiency, the content was set at 3.5 to 13.0%. (c) Ni The Ni component significantly improves the density, making the sintered alloy
It is an essential component to have a high density of 7.0 g/cm 3 or more, and it also has the effect of improving strength and heat resistance, but if its content is less than 6%, it will have a high density of 7.0 g/cm 3 or more. Not only is it not possible to secure a high density of cm 3 or more, but the strength and heat resistance are also insufficient.On the other hand, even if the content exceeds 12%, there is no significant improvement effect, and the viscosity is increased. The content was set at 6% to 12% because the increase in the content of Ni leads to deterioration of machinability. (d) Cr Similar to Mo, the Cr component combines with the C component to form carbide, which has the effect of improving wear resistance, and also dissolves in the base material to improve corrosion resistance and oxidation resistance. However, if the content is less than 1%, the desired effect cannot be obtained;
If the content exceeds 1%, the density will be less than 7.0g/cm 3 and the strength will decrease, and the hardness will increase and the opponent's aggressiveness will increase, so the content should be reduced from 1 to 6%. It was determined that (e) Co The Co component has heat resistance (red-hot hardness) as a solid solution in the base material.
The content is 0.1%.
If the content is less than 5%, the desired effect of improving heat resistance cannot be obtained, and on the other hand, if the content exceeds 5%, no further improvement effect will be obtained. Established. (f) Cu Some of the Cu components are dissolved in the base material to improve rust resistance, promote sinterability, increase density, and further improve thermal conductivity and welding resistance. This effect becomes even more pronounced when it coexists with Ni, but when the content is 0.1%
If it is less than that, the desired effect of improving the above action cannot be obtained;
On the other hand, if the content exceeds 5%, the wear resistance will decrease and the crystal grains will become coarser, increasing wear on the valve, which is the mating material, so the content should be set at 0.1 to 5%. Established. (g) SS The S component has the effect of improving the machinability of the alloy as well as its compatibility with the mating material, the valve, and these effects become particularly noticeable when coexisting with Co. Therefore, it is included as necessary when these characteristics are required, but
If the content is less than 0.05%, the desired effect of improving the above action cannot be obtained, while if the content exceeds 0.40%, the strength will decrease, so the content was set at 0.05 to 0.40%. . Note that preferably
The content is preferably 0.1 to 0.2%. Next, the Fe-based sintered alloy of the present invention will be specifically explained with reference to Examples. Example As raw material powder, atomized iron powder with particle size of -100mesh and Fe-Cr alloy (Cr: 12%) with particle size of -100mesh
Powder, -100mesh carbon powder, -400mesh carbonyl Ni powder, -200mesh Fe-Mo alloy (Mo: 58% content) powder, -200mesh Co powder,
-250mesh Cu powder and -100mesh
Prepare Fe-S alloy (S: 1% content) powder, mix these raw material powders to the composition shown in Table 1, mix for 15 minutes in a micro mixer, and then apply a pressure of 6 ton/cm 2. By molding the powder into a valve seat-shaped powder body in a hydrogen atmosphere, and then sintering the powder body at a temperature within the temperature range of 1140 to 1180°C for 1 hour in a hydrogen atmosphere, Sintered alloy valve seats 1 to 16 of the present invention, comparative sintered alloy valve seats 1 to 9, which have substantially the same final component composition as the blended composition;
and a conventional sintered metal valve seat, which has been widely used as a valve seat for internal combustion engines, were manufactured. In addition, comparative sintered alloy valve seats 1 to 9 all have compositions in which the content of one of the constituent components (those marked with * in Table 1) is outside the scope of the present invention. It is something. Next, the resulting sintered alloy valve seats 1 to 16 of the present invention, comparative sintered alloy valve seats 1 to 9, and
【表】【table】
【表】
び従来焼結合金製弁座について密度、強度を評価
する目的で圧環強度、およびビツカース硬さを測
定すると共に、実用機関にシユミレートした弁座
摩耗試験機を用い、弁材：弁用オーステナイト
鋼、弁温度：850℃、弁リフト量：6.8mm、着座荷
重：40Kg、回転数：3000r.p.m.、雰囲気：LPG燃
焼ガス，試験時間：72時間の条件で耐久摩耗試験
を行ない、全沈下摩耗量と弁座摩耗量を測定し
た。これらの測定結果を第１表に合せて示した。
第１表に示される結果から、本発明焼結合金製
弁座１〜16は、いずれも焼結ままの状態で7.0
ｇ／cm3以上の高密度を有すると共に、きわめて高
い硬さを有し、しかもその実用に際しては密度が
7.0ｇ／cm3以下にして相対的に硬さも低い従来焼
結合金製弁座に比して著しくすぐれた耐摩耗性を
有し、しかも相手攻撃性（全沈下摩耗量―弁座摩
耗量＝相手材たる弁の摩耗量）も低いことが明ら
かである。
また、比較焼結合金製弁座に見られるように、
構成成分のうちのいずれかの成分含有量がこの発
明の範囲から外れると、密度、耐摩耗性、および
相手攻撃性のうちの少なくともいずれかの性質が
劣つたものになることがわかる。
上述のように、この発明のFe基焼結合金は、
礎結ままの状態で7.0ｇ／cm3以上の高密度および
高強度を有し、かつすぐれた耐摩耗性、耐熱性、
耐食性、および耐酸化性を有しているので、特に
苛酷な条件下で使用される弁座の製造に用いた場
合にすぐれた耐久性（性能）を著しく長期に亘つ
て発揮するのである。[Table] In order to evaluate the density and strength of conventional sintered alloy valve seats, we measured the radial crushing strength and Vickers hardness, and also measured the valve seat wear tester using a valve seat wear tester that simulated a practical institution. Austenitic steel, valve temperature: 850℃, valve lift amount: 6.8mm, seating load: 40Kg, rotation speed: 3000rpm, atmosphere: LPG combustion gas, test time: 72 hours. The amount of wear and valve seat wear was measured. These measurement results are also shown in Table 1. From the results shown in Table 1, it can be seen that valve seats 1 to 16 made of the sintered alloy of the present invention all have a 7.0 value in the as-sintered state.
It has a high density of more than g/cm 3 and extremely high hardness, and in practical use,
It has significantly superior wear resistance compared to conventional sintered metal valve seats, which are less than 7.0 g/cm 3 and have relatively low hardness, and are more resistant to attack (total sinkage wear amount - valve seat wear amount = It is clear that the amount of wear on the valve, which is the mating material, is also low. In addition, as seen in the comparison sintered alloy valve seat,
It can be seen that when the content of any one of the constituent components is out of the range of the present invention, at least one of the properties of density, abrasion resistance, and aggressiveness against opponents becomes inferior. As mentioned above, the Fe-based sintered alloy of this invention is
It has high density and strength of 7.0 g/cm 3 or more in the as-built state, and has excellent abrasion resistance, heat resistance,
Because it has corrosion resistance and oxidation resistance, it exhibits excellent durability (performance) over a long period of time, especially when used in the manufacture of valve seats used under harsh conditions.