【発明の詳細な説明】[Detailed description of the invention]
〔産業上の利用分野〕
本発明は、耐摩耗性鉄系焼結合金、更に詳しく
は比較的高面圧で使用される摺動部で優れた耐摩
耗性を示す鉄系焼結合金に関するものである。
〔従来の技術〕
従来、機械構成部品のうち比較的高面圧で使用
される摺動部分においては、一般に安定した潤滑
油皮膜が得難いため、部品構成材料に対し高い耐
摩耗性及び耐ピツチング性が要求されている。該
材料として現在では硬さが高い焼入れ鋼やチル鋳
鉄もしくは硬質クロムメツキや軟窒化処理鋼等の
表面処理材料等が使用されているが、これらの材
料は必ずしも充分ではなく、摩耗やピツチング等
のトラブルが生じているものが少なくない。また
一方で、自動車部品においては近年ますます高性
能化、長寿命化の要求が大きく、特にこれらの部
品の性能向上が強く望まれている。鉄系焼結合金
は一般に耐摩耗性が優れているとされており、こ
れらは部品構成材料として比較的低面圧の部分に
は有利に使用されている。
〔発明が解決しようとする問題点〕
しかしながら、高面圧部分に適用すると、焼結
合金が一般に多くの気孔を有しているため、潤滑
油が焼結材料の気孔中に逃げてしまい安定した油
膜が得られず、その材料強度も低いので高面圧に
よる座屈や陥没現象が生じ易いし、また表面部の
局部的疲労現象であるピツチングが生じ易い等の
不具合が生じる。このため高面圧部分での鉄系焼
結合金の使用例はほとんどなかつた。
本発明者らは、鉄系焼結合金のこれらの欠点を
改良すべく種々検討を重ねた結果、高密度、高硬
度を有し上記のような欠点をすべて解消した鉄系
焼結合金で、なおかつ析出炭化物の形状分布をも
改良され、自らの耐摩耗性耐ピツチング性は勿
論、相手材の摩耗についても良好な効果を示す本
発明焼結合金を完成した。
〔問題点を解決するための手段〕
すなわち本発明の耐摩耗性鉄系焼結合金は、重
量比でクロム４（Cr）：15〜25％、銅（Cu）：１
〜５％、燐（Ｐ）：0.3〜0.8％、炭素(C)：2.0％以
上4.0％未満、残部鉄および２％以下の不純物よ
りなり密度7.3ｇ／cm3以上であることを特徴とす
る。
以下に本発明合金における各成分元素の使用目
的及び限定の理由について説明する。
Ｐは一般的にもFe系焼結合金の焼結を促進す
る事が知られているが本発明焼結合金中では著し
い効果を示している。後記実施例にも示す如く、
1100〜1200℃の一般的な焼結温度で高密度焼結体
が得られるのはＰの効果によるものである。この
ようなＰの効果は0.3％以上で顕著であるが、0.8
％までで充分であるので0.3〜0.8％とした。
Ｃはその１部がCrと化合し、（Fe、Cr）7C3など
の複合炭化物を形成して耐摩耗性を向上させ又そ
の残部はマトリツクスの硬さや強さを上昇させる
有効な元素としてその効力を発揮する。本発明焼
結合金においては２％未満のＣでは材料の硬さ、
および炭化物の量が不足するので、高面圧で充分
な耐摩耗性を得るには２％以上が必要である。し
かし４％以上の場合には炭化物粒子が成長し相手
材料を摩耗させるため４％未満が好ましい。
Crは一部マトリツクス中に固溶析出しマトリ
ツクスを強化するが、大半はＣと結合して炭化物
粒子を形成する。15％未満ではCr量に対するＣ
量が多くなり、炭化物粒子が大きくなるため好ま
しくないので15％以上とした。またCr量は多い
程有効であるが25％を越える場合には増加の効果
は少なくなり、しかも原料粉末中にFe−Cr系の
γ相が多くなつて粉末成形が困難となるため25％
以下とした。
Cuは通常の鉄系焼結合金の場合と同様に、焼
結後の冷却中にマトリツクス中に微細に析出し該
合金を強化する効果も有しているが、本発明焼結
合金中における最も重要な効果は炭化物を微細
化、球状化する点である。Cu量の好ましい範囲
は１〜５％である。
本発明の焼結合金は硬さ（ビツカース硬さHv）
400〜700を有する。またこの合金は、第１図の顕
微鏡組織（400倍）の１例で示すように強固なFe
−Cr−Cu−Ｐ−Ｃ系（α相＋γ相）マトリツク
ス中に、非常に硬く、微細粒状の（Fe、Cr）7C3
などの複合炭化物を均一に分布させたものであ
る。この本発明焼結合金は、通常の鉄系焼結合金
とほぼ同一の製法により、上記の如き高密度高硬
度を有する焼結合金として得ることができ、その
摩耗試験の効果もきわめて良好である。
〔実施例〕
以下の実施例により本発明を更に詳細に説明す
る。なお、本発明は下記実施例に限定されるもの
ではない。
重量比でCr：25％、Cu：５％、Ｐ：0.8％、
Ｃ：3.5％、残部Fe及び通常の鉄系焼結合金に含
まれる２％以下の不純物より成る合金組成から炭
素(C)を除いた組成を有する100メツシユ以上の噴
霧合金粉末を製造し、これに炭素源としての鱗片
状天然黒鉛粉末および潤滑剤としてステアリン酸
亜鉛粉末を添加し、混合機を用いて均一に混合し
た。その後、金型中で6.5ton／cm2の加圧力により
上記噴霧合金粉末をプレス成形して密度6.2〜6.4
ｇ／cm3の成形体となし、この成形体を分解アンモ
ニアガス雰囲気中（N2＋H2）で1100〜1200℃×
60分加熱焼結を行ない、まつたく通常の鉄系焼結
合金と同様にして本発明による焼結合金を得た。
得られた焼結合金の密度及び硬さを測定し、また
これらに摩耗試験を行つてパツト摩耗量及びカム
摩耗量を求めた。この摩耗試験は、得られた本発
明による焼結合金でO.H.C（オーバーヘツドカム）
動弁機構を有する排気量2200c.c.のデイーゼルエン
ジンの第２図に示すようなロツカーアームパツド
１を製作し、これをロツカーアーム２にロー付し
て合金チル鋳鉄製カム３（図中の矢印は回転方向
を示す）との組合せで実機運転して行なつた。こ
の実機運転はエンジン単体で行ない、4400r.p.m
×全負荷×50時間＋2000r.p.m×無負荷×150時間
のサイクルパターンを５回合計1000時間の試験と
して行ない、摩耗量はパツド、カムともに最大摩
耗深さを測定した。
実施例及び比較例における合金組成、密度と硬
さ、並びに摩耗試験結果を以下の表に示す。
なお、比較例は従来の合金SCr2を焼き入れ焼
きもどしたものの表面に硬質クロムメツキを施し
たものである。
[Industrial Application Field] The present invention relates to a wear-resistant iron-based sintered alloy, and more particularly to an iron-based sintered alloy that exhibits excellent wear resistance in sliding parts used under relatively high surface pressure. It is. [Prior art] Conventionally, it is generally difficult to obtain a stable lubricant film on sliding parts of machine components that are used under relatively high surface pressure, so it has been difficult to obtain a stable lubricant film on sliding parts of machine components that are used under relatively high surface pressure. is required. Currently, hardened steel, chilled cast iron, hard chrome plating, soft nitrided steel, and other surface-treated materials are used as such materials, but these materials are not always sufficient and can cause problems such as wear and pitting. There are many cases where this occurs. On the other hand, in recent years there has been a growing demand for higher performance and longer life for automobile parts, and in particular, there is a strong desire to improve the performance of these parts. Iron-based sintered alloys are generally considered to have excellent wear resistance, and they are advantageously used as component materials for parts with relatively low surface pressure. [Problems to be solved by the invention] However, when applied to high surface pressure parts, sintered alloys generally have many pores, so lubricating oil escapes into the pores of the sintered material, resulting in unstable stability. Since an oil film cannot be obtained and the material strength is low, problems such as buckling or caving due to high surface pressure are likely to occur, and pitting, which is a local fatigue phenomenon on the surface, is likely to occur. For this reason, there have been almost no examples of using iron-based sintered alloys in high surface pressure parts. As a result of various studies to improve these drawbacks of iron-based sintered alloys, the present inventors have developed an iron-based sintered alloy that has high density and high hardness and eliminates all of the above-mentioned drawbacks. Moreover, the shape distribution of the precipitated carbides has been improved, and the sintered alloy of the present invention has been completed, which exhibits good effects not only on its own wear resistance and pitting resistance, but also on the wear of the mating material. [Means for solving the problem] That is, the wear-resistant iron-based sintered alloy of the present invention has a weight ratio of chromium 4 (Cr): 15 to 25% and copper (Cu): 1.
~5%, phosphorus (P): 0.3~0.8%, carbon (C): 2.0% or more and less than 4.0%, the balance being iron and impurities of 2% or less, and having a density of 7.3 g/cm 3 or more. . The purposes of use of each component element in the alloy of the present invention and reasons for limitations will be explained below. Although P is generally known to promote sintering of Fe-based sintered alloys, P has a remarkable effect in the sintered alloys of the present invention. As shown in the examples below,
The reason why a high-density sintered body can be obtained at a general sintering temperature of 1100 to 1200°C is due to the effect of P. This effect of P is noticeable above 0.3%, but at 0.8%
% is sufficient, so it was set at 0.3 to 0.8%. A part of C combines with Cr to form composite carbides such as (Fe, Cr) 7 C 3 to improve wear resistance, and the remainder is an effective element that increases the hardness and strength of the matrix. Demonstrate its effectiveness. In the sintered alloy of the present invention, if the C content is less than 2%, the hardness of the material
Since the amount of carbide is insufficient, 2% or more is required to obtain sufficient wear resistance under high surface pressure. However, if it is 4% or more, carbide particles will grow and wear out the mating material, so it is preferably less than 4%. A part of Cr precipitates as a solid solution in the matrix and strengthens the matrix, but most of it combines with C to form carbide particles. If less than 15%, C relative to Cr content
This is not preferable because the amount increases and the carbide particles become larger, so it was set to 15% or more. In addition, the higher the Cr content, the more effective it is, but if it exceeds 25%, the effect of increasing it becomes less, and moreover, the amount of Fe-Cr system γ phase increases in the raw powder, making powder compaction difficult.
The following was made. As in the case of ordinary iron-based sintered alloys, Cu precipitates finely in the matrix during cooling after sintering and has the effect of strengthening the alloy. The important effect is that the carbide is made finer and spheroidized. The preferred range of Cu amount is 1 to 5%. The sintered alloy of the present invention has a hardness (Bitzkers hardness Hv)
Having 400-700. In addition, this alloy has strong Fe as shown in the microscopic structure (400x magnification) in Figure 1.
-Cr-Cu-P-C system (α phase + γ phase) matrix contains very hard, fine grains (Fe, Cr) 7 C 3
It is made by uniformly distributing composite carbides such as The sintered alloy of the present invention can be obtained as a sintered alloy having high density and high hardness as described above by using almost the same manufacturing method as that for ordinary iron-based sintered alloys, and its wear test effects are also extremely good. . [Example] The present invention will be explained in more detail with the following example. Note that the present invention is not limited to the following examples. Weight ratio: Cr: 25%, Cu: 5%, P: 0.8%,
Produce a sprayed alloy powder of 100 meshes or more having a composition excluding carbon (C) from an alloy composition consisting of C: 3.5%, balance Fe, and impurities of 2% or less contained in ordinary iron-based sintered alloys. A scaly natural graphite powder as a carbon source and a zinc stearate powder as a lubricant were added to the mixture and mixed uniformly using a mixer. Thereafter, the above sprayed alloy powder was press-molded in a mold with a pressure of 6.5 ton/cm 2 to a density of 6.2 to 6.4.
g/cm 3 and heat the molded product at 1100 to 1200°C in a decomposed ammonia gas atmosphere (N 2 + H 2 ).
A sintered alloy according to the present invention was obtained by heating and sintering for 60 minutes in the same manner as a conventional iron-based sintered alloy.
The density and hardness of the obtained sintered alloy were measured, and a wear test was performed on these to determine the amount of wear on the parts and the amount of cam wear. This wear test was carried out using OHC (overhead cam) on the obtained sintered alloy according to the present invention.
A rocker arm pad 1 as shown in Figure 2 for a diesel engine with a displacement of 2200 c.c. having a valve mechanism is manufactured, and this is brazed to the rocker arm 2, and an alloy chilled cast iron cam 3 (as shown in the figure) is manufactured. The arrow indicates the direction of rotation). This actual machine operation was performed with the engine alone, and the speed was 4400r.pm.
A cycle pattern of x full load x 50 hours + 2000 rpm x no load x 150 hours was conducted five times for a total of 1000 hours, and the amount of wear was determined by measuring the maximum wear depth for both pads and cams. The alloy composition, density and hardness, and wear test results for Examples and Comparative Examples are shown in the table below. The comparative example is a conventional alloy SCr 2 which has been quenched and tempered, and the surface of which has been hard chrome plated.
〔発明の効果〕〔Effect of the invention〕
以上のように、本発明による組成を用いた鉄系
焼結合金は、機械構成部品として比較的高面圧で
使用される摺動部に適用しても、その高密、高強
度及び耐摩耗性によつて従来からのトラブルが全
て解消され、良好に作用するので、今日望まれて
いる自動車等の高性等化及び長寿命化に対し、大
いに有利である。また本発明の焼結合金は、特に
適している内燃機関のカム、ロツカーアームパツ
ド、バルブリフターやバルブチツプ等高面圧がか
かる摩耗部の他、一般的な耐摩耗性材料としても
使用できる等、応用範囲も広く、工業的にきわめ
て価値のあるものである。
As described above, the iron-based sintered alloy using the composition according to the present invention has high density, high strength, and wear resistance even when applied to sliding parts used as machine components under relatively high surface pressure. This eliminates all the conventional troubles and works well, so it is very advantageous for achieving higher performance and longer life of automobiles, etc., which are desired today. The sintered alloy of the present invention can also be used as a general wear-resistant material, in addition to wear parts that are subject to high surface pressure, such as cams, rocker arm pads, valve lifters, and valve chips, which are particularly suitable for internal combustion engines. It has a wide range of applications and is extremely valuable industrially.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は本発明の耐摩耗性鉄系焼結合金の一実
施例の合属組織の顕微鏡写真（倍率400倍）、第２
図は摩耗試験を行うための装置の一部分の側面図
を示す。
図中、１……ロツカーパツド、２……ロツカー
アーム、３……カム。
Figure 1 is a micrograph (magnification: 400x) of the composite structure of one embodiment of the wear-resistant iron-based sintered alloy of the present invention;
The figure shows a side view of a part of an apparatus for carrying out wear tests. In the diagram, 1...Rotscar pad, 2...Rotscar arm, 3...Cam.