JP3939200B2 - Grease-filled heat-resistant rolling bearing - Google Patents

Description

【００４３】
【化２】

【００４４】
【化３】

【００４５】
【化４】

【００４６】
他の基油である合成油は、特にその種類を限定したものではなく、例えばポリオールエステル油やアルキルジフェニルエーテル油、ポリオレフィン油などが用いられる。
【００４７】
ポリオールエステル油としては、例えば炭素数７〜２２のアルコール類と芳香族トリカルボン酸またはテトラカルボン酸との芳香族エステル、炭素数７〜２２の脂肪族カルボン酸とトリメチロールプロパン、ペンタエリスリトールまたはジペンタエリスリトールとのエステルなどが挙げられる。
【００４８】
アルキルジフェニルエーテル油としては、モノアルキルジフェニルエーテル、ジアルキルジフェニルエーテルが挙げられる。
【００４９】
ポリオレフィン油は、室温で液状を示し、動粘度が１００ｍｍ²／ｓ以上のものが蒸発損失が小さくて好ましいものである。
【００５０】
この発明に用いる潤滑グリースの増ちょう剤である粒子状フッ素樹脂は、フッ素樹脂を基油に分散しやすい微粒子状に調整したものであり、パーフルオロポリエーテル油と親和性が良く、高温で安定性がよく、耐薬品性を有する。フッ素樹脂の種類としては、テトラフルオロエチレン−ヘキサフルオロエチレン共重合体（ＦＥＰ）やポリテトラフルオロエチレン（ＰＴＦＥ）等のフッ素樹脂を例示できる。
【００５１】
また、ウレア化合物からなる増ちょう剤としては、尿素結合を分子内に２個有するジウレアが好ましく、脂環族ウレアや芳香族ウレアは耐熱性の面でより好ましいものである。
【００５２】
ジウレア化合物の具体例としては、以下の化５の式に示すものを挙げられる。
【００５３】
【化５】

【００５４】
上記の式で表わされるジウレア化合物のうちでもＲ₁とＲ₃が、脂肪族基、脂環族基または芳香族基である（Ｒ₁とＲ₃は同種の基でも異種の基であってもよい。）脂環族ウレアまたは芳香族ウレアが耐熱性の点で好ましい。なお、このようなウレア化合物を基油中に製造するには、例えばジイソシアナート化合物にイソシアナート基当量のアミン化合物を反応させればよい。
【００５５】
【実施例および比較例】
表１に示す潤滑グリースと鋼材の組み合わせにより、実施例および比較例のグリース封入耐熱性転がり軸受を作製した。
【００５６】
表１のグリースの種類の欄に示す「フッ素系Ｇ」は、増ちょう剤としてフッ素樹脂粒子（デュポン社製：ＴＰＬ）を用い、基油としてパーフルオロポリエーテル油（デュポン社製：クライトックス２４０ＡＣ）を用いて調製されたフッ素系グリースである。
【００５７】
また、表１に示す「ウレア系Ｇ」は、増ちょう剤としてウレア化合物（化５の式において、Ｒ₁、およびＲ₃がシクロヘキシル基、Ｒ₂がジフェニルメタン基である脂環族ウレアである。）を用い、基油として合成油である芳香族エステル油（旭電化工業社製：プルーバーＴ９０）を用いたウレア系グリースである。
【００５８】
そして、表１に示す「（フッ素＋ウレア）Ｇ」は、上記のフッ素系グリースを５０重量％と前記のウレア系グリースを５０重量％混合して得られる潤滑グリースである。
【００５９】
実施例に用いた鋼材は、以下の組成（重量％）の３種頚（▲１▼のＭ５０と▲２▼▲３▼の高Ｃ−Ｓｉ−Ｎｉ鋼）であり、▲４▼は比較例に用いたＳＵＪ２である。以下の表中には、鋼材の種類を丸付きの番号で示す。
▲１▼ 0.8Ｃ−0.3Ｓｉ−4.0Ｃｒ−4.3Ｍｏ−1.0Ｖ (Ｍ５０)
▲２▼ 1.1Ｃ−1.0Ｓｉ−1.5Ｍｎ−1.0Ｎｉ−1.5Ｃｒ鋼
▲３▼ 1.1Ｃ−1.0Ｓｉ−1.5Ｍｎ−1.0Ｎｉ−1.5Ｃｒ−0.5Ｖ−0.2Ｍｏ鋼
▲４▼ 1.0Ｃ−0.3Ｓｉ−0.5Ｍｎ−1.5Ｃｒ鋼 （ＳＵＪ２）
いずれの鋼も焼入または浸炭窒化および焼入し、その後に▲１▼は５５０℃、▲２▼▲３▼は３００℃で焼戻しを行なった。因みに、５５０℃はＭ５０の標準的な焼戻し温度である。▲２▼▲３▼を３００℃で焼戻した理由は、２００℃での使用条件で経年寸法変化を抑えるためには２５０℃以上の焼戻しが必要であり、さらに余裕をみて３００℃に設定したものである。焼戻後の鋼材硬度は、Ｍ５０でＨＲＣ６１．５であり、▲２▼、▲３▼の３００℃焼戻品でそれぞれＨＲＣ５９．５〜６０．５、６０〜６１であった。また、▲２▼の鋼材に浸炭窒化した後に３００℃で焼戻したものは、ＨＲＣ６１以上であった。▲４▼のＳＵＪ２は３００℃の焼戻しでＨＲＣ５６〜５７であった。
【００６０】
このようにして所定の硬度に調製された各鋼材で実施例および比較例の玉軸受６２０６（ＮＴＮ社製：６２０６Ｃ３）を作製し、以下の▲１▼〜▲４▼の評価試験を行なった。
【００６１】
各試験の概要と結果は以下の通りである。
▲１▼玉軸受６２０６での高温寿命試験
実施例および比較例の玉軸受（６２０６Ｃ３）を、荷重Ｆｒ＝６．８６ｋＮ、内輪回転速度２０００ｒｐｍ、試験温度：常温〜２００℃という高温・高荷重で連続回転させて寿命を評価した。なお、計算寿命は、１９１時間（潤滑係数は考慮せず。）であり、サンプル数Ｎを１０とし、疲労強度を１０％寿命（サンプルの９０％が破損しないで使える負荷回数）で評価した。
【００６２】
【表１】

【００６３】
表１の結果からも明らかなように、比較例２は比較的長寿命であるが、同一鋼材を採用した実施例２の４０％程度の寿命時間であった。その他の比較例は、グリースが原因（ウレアグリース）となって焼付いたり、鋼材（▲４▼ＳＵＪ２）が原因で短寿命であった。
【００６４】
一方、鋼材にＭ５０を用いた実施例ｌの寿命は、長寿命であり、常温試験において実施例２は、非常に長寿命であった。鋼材の焼戻し温度が低い（１８０℃）実施例６は、焼戻温度が３００℃の実施例２に比べて硬度がＨＲＣ６２．５〜６３．５と３ポイントほど高いが、その寿命は大きく変わらず長寿命であった。
【００６５】
▲２▼微動摩耗試験（常温におけるファフナ型）
ＡＳＴＭのＤ４１７０に準拠したファフナ（Fafnier）型微動摩耗試験を行なった。用いた試験片は軸受型式は５１２０４（内径２０×外径×厚さ１４ｍｍ）の軌道輪、摺動相手はＳＵＪ２製の鋼球である。荷重２４５０Ｎまたは７０００Ｎ、揺動角１２度、揺動サイクル３０Ｈｚ、グリース量１±０．１ｇ、大気中の常温での試験雰囲気で試験時間８時間後の摩耗量（ｍｇ）を重量の減量値で評価し、その結果を表２に示した。表の結果は、繰り返し数４回の摩耗量の範囲と平均値を示している。
【００６６】
【表２】

【００６７】
試験機の構造上、高温の評価ではないが、グリースと鋼材を組み合わせた実施例の摩耗は少なかった。特に、鋼材▲１▼を用いた実施例１は、摩耗の面では安定して優れていた。
【００６８】
ＳＵＪ２の鋼材▲４▼は、フッ素とウレアグリースだけか、またはウレアグリースだけでもかなり耐摩耗性の効果があった。高温寿命試験ほど鋼材やグリースの差が現れ難かった原因としては、試験条件が常温であるために鋼材の特性が影響しなかったことに加えて、ファフナ型試験は鋼球とレースの接触楕円幅以上に揺動し、その際に相手鋼球も通常のＳＵＪ２であるために、厳しく摩耗しなかったと考えられた。
【００６９】
常温での摩耗試験として、鋼材の焼戻し温度が低い（１８０℃）実施例６も試験したが、焼戻温度３００℃である実施例２に比べて高硬度のため、摩耗が少なかった。なお、実施例のグリースの使用により摩耗が少なかった鋼材１（Ｍ５０）でもフッ素グリースを用いた比較例７では摩耗が大きく、フッ素系樹脂とウレア化合物で増ちょうさせたグリースでなければ鋼材１の耐摩耗特性が充分に生かせないといえる。
【００７０】
▲３▼微動摩耗試験（プレートに対する鋼球の摩擦）
フレッティングのような微小すべりに対する摩耗特性を確認するために、フレッティング試験機（ＮＴＮ社製）を用いて微動摩耗試験を行なった。すなわち、鋼材の平板（２０ｍｍ角で厚さ５ｍｍ）型試験片に対して、ＳＵＪ２製または表３に示した組成の鋼球１個を９８Ｎまたは２９４Ｎの荷重で押し当て、接点を振幅０．４７ｍｍ、振動数３０Ｈｚで８時間（繰り返し数１回）の微小往復摺動させた。この試験後の▲１▼平板の摩耗深さと▲２▼鋼球の摩耗体積を測定した。
【００７１】
▲１▼平板の摩耗深さは、摩耗方向と直角の５点を表面粗さ計（タリサーフ）で測定し、最大深さを求めた。▲２▼鋼球の摩耗体積Ｖは、以下の式を用い、摩耗痕直径から求め、結果を表３に示した。因みに、この試験では、揺動量が少ないので潤滑剤が試験面に介在し難く、摩耗が加速される。
Ｖ＝（πｈ²×（３ｒ−ｈ））／３、 ｈ＝ｒ−（４ｒ²−Ｃ²）^1/2／２（但し、式中のｒ＝鋼球の半径、ｈ＝鋼球の摩耗深さ、Ｃ＝摩耗痕の直径である。）
【００７２】
【表３】

【００７３】
表３の結果からも明らかなように、ファフナ型試験結果と同様に、実施例の組み合わせの場合に平板および鋼球の摩耗が少なかった。特に摺接相手の鋼球を実施例の組成で形成し、平板に浸炭窒化または焼戻し温度が低いもの（実施例３ａ、実施例５、６）、セラミックス（Ｓｉ₃Ｎ₄）を用いたもの（実施例７）では特に摩耗が減少した。
【００７４】
▲４▼高温での摩擦摩耗試験
高温のサバン型摩擦摩耗試験機による２００℃で評価した。高温摩擦摩耗試験機（ＮＴＮ社製）は、幅面をラッピング仕上げした平板（縦４０ｍｍ、幅６ｍｍ、厚さ５ｍｍ）と、回転リング（外径超仕上げのＭ５０製の外径１００ｍｍ、内径３０ｍｍ、厚さ１０ｍｍ）を押付けるサバン型摩耗試験機を改良したものであり、高温で高温潤滑油を摩擦面に供給し、高温での摩擦摩耗を評価する構造である。グリースの評価のため、高温潤滑油の代わりに高温空気と平板サンプルを加熱することで試験面を２００℃に保持し、荷重１００Ｎ、回転速度３０００ｒｐｍで試験時間１０分（繰り返し数１回）で評価した。
【００７５】
【表４】

【００７６】
表４に示した試験結果からも明らかなように、実施例のものは非常に摩耗が少なく、高温での摩擦摩耗特性に優れていた。この場合も浸炭窒化したものが良い結果であった。また、１８０℃焼戻し品も試験時の耐熱時間が短いので評価することができたが、高温焼戻し品と大きく変わることはなかった。セラミックス（Ｓｉ₃Ｎ₄）を試験片にした実施例７は、他の鋼試験片の実施例よりも更に摩耗が少ない結果であった。
【００７７】
【発明の効果】
この発明は、以上説明したように、内輪および外輪が、２５０℃以上の高温で焼戻されたＨＲＣ５９以上の硬度を示す鋼材で形成され、潤滑グリースが所定の基油と増ちょう剤からなるグリース封入耐熱性転がり軸受としたので、高温での軸受寿命（潤滑寿命と材料の疲労寿命）をバランス良く長寿命にして、転がり軸受が高温・高荷重で断続運転する場合において焼付や潤滑不良がなく、特に高温・高荷重で摩耗量が少なく、低騒音レベルで長寿命の耐熱性転がり軸受になる利点がある。
【００７８】
また、軸受材料を浸炭窒化することで、高温での表面硬度を確保し、一層の転動寿命の長寿命化や耐フレッティング、耐摩耗強度を向上させたものである。
【００７９】
軸受鋼材として所定の成分からなるものを使用すると、コストパフォーマンスに優れたものになり、セラミックスの転動体を用いると常温から高温（２００℃）まで安定して長寿命で耐摩耗特性も優れたものになる。また、鋼材に浸炭窒化処理により硬度をＨＲＣ６１以上にしたものは一層優れた長寿命性および耐摩耗性がある。
【図面の簡単な説明】
【図１】実施形態の耐熱性転がり軸受の断面図
【符号の説明】
１ 内輪
２ 外輪
３ 保持器
４ 転動体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rolling bearing in which lubricating grease is sealed in a bearing, and more particularly to a grease-sealed heat-resistant rolling bearing that can be used in a high temperature range of 200 ° C. or higher.
[0002]
[Prior art]
Bearings for plastic film stretchers such as polyethylene, dryer roll support bearings for paper machines, and alternators and electromagnetic clutch bearings that are electrical equipment auxiliary parts for automobiles have a maximum operating temperature of 150 ° C or higher. If normal lubricating grease that does not take heat resistance into consideration is sealed and lubricated, the volatilized base oil leaks from the bearing, and if it proceeds further and the lubricating oil is insufficient, seizure or poor lubrication may occur.
[0003]
Fluorine grease with excellent heat resistance that can be enclosed in a rolling bearing is not very widely used because it is very expensive, and it cannot be said that the lubrication characteristics are necessarily sufficient under normal temperature conditions.
[0004]
Furthermore, the hydrocarbon grease rust preventive agent is not uniformly dispersed in the fluorine grease, and it has been difficult to fully exhibit the rust preventive performance by mixing it.
[0005]
In other words, heat-resistant lubricating greases such as fluorine grease are not as stable at high temperatures as they are at low temperatures, and there is no other knowledge of lubricating greases that have stable and excellent lubricating properties over a wide temperature range from room temperature to about 200 ° C. The known lubricating grease with a low heat resistance level has a drawback that it is likely to leak due to oil repellency at high temperatures.
[0006]
On the other hand, when considering heat resistance from the material (steel material) of rolling bearings, JIS standard bearing steel that can withstand the use conditions up to 200 ° C can be tempered in advance at a temperature about 50 to 100 ° C higher than such use temperature. Even at high temperatures exceeding 200 ° C., the dimensional change can be considerably suppressed.
[0007]
[Problems to be solved by the invention]
However, when tempering at a high temperature exceeding 200 ° C. with respect to the material of a normal rolling bearing, the hardness and mechanical strength are weakened and it is easy to cause “rolling fatigue peeling”, “wear” or “cracking”. This shortens the service life of the bearing.
[0008]
Furthermore, under operating conditions in which the rolling bearing is operated intermittently at high temperatures, the lubricating oil volatilizes when left at a high temperature, causing a “lubricating oil film breakage”, so that “fretting wear” is likely to occur, and acoustic degradation occurs. And vibration, bearing life is shortened.
[0009]
In recent years, since the usage conditions of rolling bearings are often required to be high load and high speed, there are also increasing specifications that require high temperature heat resistance such as 200 ° C to 220 ° C.
[0010]
Therefore, the object of the present invention is to solve the above-mentioned problems, and when the rolling bearing is intermittently operated at high temperature and high load, there is no seizure or lubrication failure, and especially the amount of wear is small at high temperature and high load. Thus, a heat-resistant rolling bearing capable of maintaining a low rotational torque with a low noise level and a long service life is provided.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in a rolling bearing in which a plurality of rolling elements are interposed between an inner ring and an outer ring and lubricating grease is sealed around the rolling elements, the inner ring and the outer ring have 250 The lubricating grease is made of a steel material having a hardness of HRC 59 or higher that has been tempered at a high temperature of ℃ or higher, and the lubricating grease is based on perfluoropolyether oil and synthetic oil, and is a particulate fluororesin and urea It was a grease-filled heat-resistant rolling bearing characterized by being a lubricating grease containing a compound as a thickener.
[0012]
The grease-filled heat-resistant rolling bearing of the present invention configured as described above has a predetermined hardness steel material (for example, high-speed tool steel, martensitic stainless steel, high-temperature steel, and the like. Since it is made of Si-Cr steel, etc., the inner ring and the outer ring are not worn and the dimensional change does not occur at the degree of friction at 200 ° C. or less, resulting in a shortage of lubricating oil at a high temperature for a short time. However, it is difficult to cause fretting phenomenon, and the rolling bearing has a long service life.
[0013]
Also, since the lubricating grease is a lubricating grease that uses perfluoropolyether oil and synthetic oil as a base oil and a particulate fluororesin and a urea compound as a thickener, the base oil is difficult to volatilize and the lubricating grease leaks. Is suppressed.
[0014]
In addition, the lubricating grease used in the present invention has been improved by the particulate fluororesin to which the physical properties of the conventional grease, which is easy to cure at high temperatures with only the urea compound, are improved, and has excellent heat resistance almost similar to that of the fluorine grease. Have.
[0015]
In addition, the lubricating grease used in the present invention can be used by uniformly dispersing hydrocarbon-based rust-preventing additives that could not be used as rust-preventing agents with conventional fluorine greases. It can be made.
[0016]
Further, in order to solve the same problem as described above, in the grease-filled heat-resistant rolling bearing having the above-described configuration, the steel material has 0.6 to 1.3 mass% of C and 0.3 to 3.0 mass of Si. %, Ni is 0.1 to 3.0% by mass, Mn is 0.2 to 1.5% by mass, and Cr is 0.3 to 5.0% by mass. it can.
[0017]
The above grease-filled heat-resistant rolling bearing made of a steel material with a predetermined composition described above has a reduced wear amount from room temperature to high temperature more reliably because the bearing is made of a steel material with a predetermined composition. Less bearings.
[0018]
In order to further improve the wear resistance, the steel material further contains 0.05 to 1.0% by mass of V, and 0.05 to 1.0% by mass of Mo. It is preferable to use an encapsulated heat resistant rolling bearing.
[0019]
A grease-filled heat-resistant rolling bearing in which inner and outer rings are formed of a steel material to which vanadium is added has improved wear resistance due to improved galling resistance, rolling fatigue resistance, and surface damage resistance.
[0020]
In addition, a rolling bearing in which the inner ring and the outer ring of such a heat-resistant rolling bearing are formed of steel and the rolling elements are formed of ceramics can suppress seizure and increase in wear caused by the so-called “togane” phenomenon. In addition, the conventional rolling bearing eliminates the drawback that seizure by the same kind of metal is likely to occur when the lubricating oil film is thin.
[0021]
Moreover, in the rolling bearing having the above-described configuration, it is preferable to use a grease-filled heat-resistant rolling bearing in which a carbonitriding layer having a hardness of HV725 (HRC61) or higher is formed on the steel material surface.
[0022]
Rolling bearings constructed in this way are carbonitrided on steel bearing materials, ensuring surface hardness at high temperatures, further extending rolling life, and improving fretting and wear resistance. Can be made.
[0023]
The grease-filled heat-resistant rolling bearing according to the present invention combines a predetermined grease and a bearing material in this way to prolong the bearing life (lubricating life and material fatigue life) in a well-balanced manner and to lubricate at high temperatures. It is possible to suppress the time-dependent acoustic deterioration and the occurrence of vibration due to fretting due to oil film breakage and wear.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings.
[0025]
The grease-filled heat resistant rolling bearing of the embodiment shown in FIG. 1 has a plurality of rolling elements 4 interposed between an inner ring 1 and an outer ring 2 via a cage 3, and lubricating grease (not shown) is provided around the rolling elements 4. )) Is a deep groove ball bearing. The rolling bearing applicable to this invention may be a well-known form in which heat resistance is ensured by the material, and in particular, the type of the bearing and other forms can be used without any particular limitation.
[0026]
The steel material used in the present invention is adopted as a material for forming the cage 3 provided as necessary in addition to the inner ring 1 and the outer ring 2, and when used for a long time at the heat-resistant temperature of grease of a predetermined composition, It is a high-hardness steel material that can hold the rolling element reliably and rotatably with little dimensional change.
[0027]
Specific examples of the steel material include high speed tool steel such as M50, martensitic stainless steel containing 10% or more of Cr, and high Si steel. In particular, high-Si steel is a steel material that is suitable in terms of material cost and rolling life, and in particular, C is 0.6 to 1.3% by mass (% in the following steel material composition is all mass%). An alloy steel containing 0.3 to 3.0% of Si, 0.1 to 3.0% of Ni, 0.2 to 1.5% of Mn, and 0.3 to 5.0% of Cr By using it, it is possible to reduce the cost and improve the life of the raceway or rolling element at a high temperature.
[0028]
The above-described M50 is a Cr—Mo—V high-speed tool steel, and has a precipitation secondary hardening phenomenon due to tempering. Therefore, HRC60 or more can be secured even at high temperature tempering of 500 ° C. or higher. In addition, because of the high alloy, a large amount of carbide precipitates, and it is difficult to obtain the rolling life of the following high Si steel, but it is the most excellent in corrosion resistance, wear resistance and fretting resistance.
[0029]
Steel containing 10% or more of Cr also has high tempering resistance, excellent corrosion resistance, and stable austenite even at high temperature tempering, so it has a feature of excellent rolling life. The bearing can be made strong against fretting.
[0030]
On the other hand, a high Si material has no problem in terms of rolling life, but is slightly inferior to the above steel in terms of wear resistance and fretting resistance. Therefore, a composition in which C is increased and Cr or Ni is added. Is required. In particular, it is preferable to use the high Si steel having the predetermined composition described above.
[0031]
In that case, the amount of Si was included in the range of 0.3 to 3.0% because Si suppresses softening when the temperature becomes high, so that an effect of improving heat resistance can be expected. If the Si content is less than 0.3%, the effect cannot be obtained. Even if the Si content exceeds 3.0%, the effect is saturated, and hot workability and machinability are deteriorated.
[0032]
The reason why Ni was contained in an amount of 0.1 to 3.0%, V was 0.05 to 1.0%, and Mo was less than 0.05 to 0.25% alone or in combination was as follows. .
[0033]
Ni dissolves in steel and strengthens the matrix, suppresses the change of the structure particularly in the rolling fatigue process, and improves the toughness against cracking.
[0034]
Therefore, Ni has an effect of improving rolling fatigue characteristics, surface damage resistance, and fatigue crack strength, and in order to obtain these effects, Ni needs to be contained by 0.1% or more. However, even if Ni is contained exceeding 3.0%, a large amount of retained austenite is generated during the quenching process, and a predetermined hardness cannot be obtained, and the cost of the steel material is increased.
[0035]
Both Mn and Cr improve the hardenability of the steel material. Mn solidifies in the steel to strengthen the steel, and Cr forms carbides and strengthens the steel. The reason why the lower limit of the Mn content is 0.2% and the lower limit of the Cr content is 0.3% is to obtain these effects. Moreover, the upper limit of the Mn content was limited to 1.5% in order to avoid a decrease in machinability, and the upper limit of the Cr content was limited to 5.0% for large carbides. This is to prevent embrittlement due to formation. These elements can also improve rolling fatigue characteristics and improve crack fatigue strength by containing appropriate amounts. In particular, since Cr precipitates a large amount of carbide by adding to steel with increased C, wear resistance at high temperatures can be remarkably improved.
[0036]
The action of these alloy components prevents the surface from being softened even at high temperatures, and it can be made into a bearing part with excellent high-temperature life. Further, by adding the following amounts of V and Mo, further improvement of the characteristics is intended. Can do.
[0037]
V combines with carbon to precipitate fine carbides, refines crystal grains to improve strength and toughness, and suppresses softening at high temperatures. Therefore, like Ni described above, V has an effect of improving galling resistance, rolling fatigue characteristics, and surface damage resistance. In order to obtain this effect, the lower limit of the V content is set to 0.05%. The reason why the upper limit is limited to 1.0% is that if V is contained in a large amount exceeding 1.0%, machinability and hot workability are lowered.
[0038]
Mo improves the hardenability of the steel, prevents temper embrittlement, and further suppresses softening at high temperatures. Therefore, Mo also has an effect of improving galling resistance, rolling fatigue characteristics, and surface damage resistance. In order to obtain this effect, the lower limit of the Mo content is set to 0.05%. If the Mo content is 0.25% or more, the machinability is lowered and the steel material cost is also increased.
[0039]
In addition, forming bearing parts with ceramics such as Si ₃ N ₄ , SiC, Al ₂ O ₃ , and ZrO ₂ also prevents wear due to wear resistance and seizure due to metal contact when the grease film is thin. effective. By using at least a rolling element as a ceramic, it is possible to prevent seizure and wear due to the “toggle” phenomenon.
[0040]
In this way, the combination of grease components and steel, preferably including ceramics, can increase the life at high temperatures (lubrication life and fatigue life of materials) in a well-balanced manner, and fretting by running out of the lubricating oil film when still at high temperatures. It is possible to suppress deterioration with time and vibration due to wear and vibration. Further, by carbonitriding the steel bearing material, it is possible to extend the rolling life and improve the fretting resistance and wear resistance.
[0041]
The perfluoropolyether oil, which is the base oil of the lubricating grease used in the present invention, is a compound in which the hydrogen atom of the aliphatic hydrocarbon polyester is substituted with a fluorine atom. Typical examples thereof include Krytox (DuPont product), Fomblin Y, Z, and M (Montesyson product names, shown in Chemical Formulas 2, 3, and 4 respectively) shown in the formula (1).
[0042]
[Chemical 1]

[0043]
[Chemical 2]

[0044]
[Chemical 3]

[0045]
[Formula 4]

[0046]
The type of synthetic oil that is another base oil is not particularly limited, and for example, polyol ester oil, alkyl diphenyl ether oil, polyolefin oil, and the like are used.
[0047]
Examples of the polyol ester oil include aromatic esters of alcohols having 7 to 22 carbon atoms and aromatic tricarboxylic acid or tetracarboxylic acid, aliphatic carboxylic acids having 7 to 22 carbon atoms and trimethylolpropane, pentaerythritol or dipenta. And esters with erythritol.
[0048]
Examples of the alkyl diphenyl ether oil include monoalkyl diphenyl ether and dialkyl diphenyl ether.
[0049]
Polyolefin oils are liquid at room temperature, and those having a kinematic viscosity of 100 mm ² / s or more are preferable because of low evaporation loss.
[0050]
The particulate fluororesin that is a thickener for the lubricating grease used in the present invention is prepared by adjusting the fluororesin into fine particles that are easy to disperse in the base oil. It has good affinity with perfluoropolyether oil and is stable at high temperatures. It has good chemical resistance. Examples of the fluororesin include fluororesins such as tetrafluoroethylene-hexafluoroethylene copolymer (FEP) and polytetrafluoroethylene (PTFE).
[0051]
Further, as the thickener made of a urea compound, diurea having two urea bonds in the molecule is preferable, and alicyclic urea and aromatic urea are more preferable in terms of heat resistance.
[0052]
Specific examples of the diurea compound include those shown in the following chemical formula 5.
[0053]
[Chemical formula 5]

[0054]
Among the diurea compounds represented by the above formula, R ₁ and R ₃ are aliphatic groups, alicyclic groups or aromatic groups (R ₁ and R ₃ may be the same or different groups). Good) Alicyclic ureas or aromatic ureas are preferred from the viewpoint of heat resistance. In order to produce such a urea compound in a base oil, for example, an isocyanate compound equivalent to an isocyanate group may be reacted with a diisocyanate compound.
[0055]
Examples and Comparative Examples
The grease-encapsulated heat-resistant rolling bearings of Examples and Comparative Examples were produced by combining the lubricating grease and steel material shown in Table 1.
[0056]
“Fluorine-based G” shown in the column of grease type in Table 1 uses fluororesin particles (manufactured by DuPont: TPL) as a thickener and perfluoropolyether oil (manufactured by DuPont: Krytox 240AC) as a base oil. ) -Based fluorine grease.
[0057]
“Urea G” shown in Table 1 is a urea compound (in the formula of Chemical Formula 5, R ₁ and R ₃ are cyclohexyl groups, and R ₂ is a diphenylmethane group as a thickener. ), And a urea-based grease using an aromatic ester oil (Asahi Denka Kogyo Co., Ltd .: Prover T90) as a base oil.
[0058]
“(Fluorine + Urea) G” shown in Table 1 is a lubricating grease obtained by mixing 50% by weight of the above-mentioned fluorine-based grease and 50% by weight of the above-mentioned urea-based grease.
[0059]
The steel materials used in the examples are three kinds of necks (M50 of (1) and high C-Si-Ni steel of (2) and (3)) having the following composition (% by weight), and (4) is a comparative example. It is SUJ2 used for. In the following table, the types of steel materials are indicated by numbers with circles.
(1) 0.8C-0.3Si-4.0Cr-4.3Mo-1.0V (M50)
(2) 1.1C-1.0Si-1.5Mn-1.0Ni-1.5Cr steel (3) 1.1C-1.0Si-1.5Mn-1.0Ni-1.5Cr-0.5V-0.2Mo steel (4) 1.0C-0.3Si -0.5Mn-1.5Cr steel (SUJ2)
All the steels were quenched or carbonitrided and quenched, and then tempered at 550 ° C. for (1) and at 300 ° C. for (2) and (3). Incidentally, 550 ° C. is a standard tempering temperature of M50. The reason for tempering (2) and (3) at 300 ° C is that tempering at 250 ° C or higher is necessary to suppress changes over time in the conditions of use at 200 ° C, and the temperature was set to 300 ° C with a margin. It is. The steel material hardness after tempering was HRC 61.5 at M50, and HRC 59.5 to 60.5 and 60 to 61 for 300 ° C. tempered products (2) and (3), respectively. In addition, carbon steel that was carbonitrided and then tempered at 300 ° C. was HRC 61 or higher. The SUJ2 of (4) was HRC 56-57 after tempering at 300 ° C.
[0060]
The ball bearing 6206 of Example and Comparative Example (NTN Corp .: 6206C3) was produced from each steel material thus prepared to a predetermined hardness, and the following evaluation tests (1) to (4) were performed.
[0061]
The outline and results of each test are as follows.
{Circle around (1)} High Temperature Life Test with Ball Bearing 6206 The ball bearing (6206C3) of Example and Comparative Example was continuously loaded at high temperature and high load of load Fr = 6.86 kN, inner ring rotational speed 2000 rpm, test temperature: normal temperature to 200 ° C. The life was evaluated by rotating. The calculated life was 191 hours (without considering the lubrication coefficient), the number of samples N was 10, and the fatigue strength was evaluated by 10% life (the number of loads that can be used without damaging 90% of the samples).
[0062]
[Table 1]

[0063]
As is clear from the results in Table 1, Comparative Example 2 has a relatively long life, but it has a life time of about 40% of Example 2 in which the same steel material is used. The other comparative examples had a short life due to the seizure caused by grease (urea grease) or due to the steel material (4) SUJ2.
[0064]
On the other hand, the life of Example 1 using M50 as the steel material was long, and Example 2 was very long in the normal temperature test. Example 6 in which the tempering temperature of the steel material is low (180 ° C.) is higher by about 3 points in hardness than HRC 62.5 to 63.5 in comparison with Example 2 in which the tempering temperature is 300 ° C., but its life does not change greatly. Long life.
[0065]
(2) Fine wear test (fafner type at normal temperature)
A Fafnier type fine wear test in accordance with ASTM D4170 was performed. The test piece used is a bearing type 51204 (inner diameter 20 × outer diameter × thickness 14 mm) and a sliding ball is a SUJ2 steel ball. Load 2450N or 7000N, rocking angle 12 degrees, rocking cycle 30Hz, grease amount 1 ± 0.1g, wear amount (mg) after 8 hours test time in a test atmosphere at normal temperature in the atmosphere as weight reduction value The results are shown in Table 2. The results in the table show the range of wear amount and the average value of 4 repetitions.
[0066]
[Table 2]

[0067]
Although it was not a high-temperature evaluation due to the structure of the testing machine, there was little wear in the examples combining grease and steel. In particular, Example 1 using the steel material (1) was stable and excellent in terms of wear.
[0068]
The steel material (4) of SUJ2 had a considerable wear resistance effect only with fluorine and urea grease or with urea grease alone. The reason why the difference in steel and grease was less likely to appear in the high-temperature life test was that the properties of the steel did not affect because the test conditions were at room temperature. It was considered that the steel ball oscillated as described above and the mating steel ball was normal SUJ2 and therefore did not wear severely.
[0069]
As a wear test at normal temperature, Example 6 in which the tempering temperature of the steel material was low (180 ° C.) was also tested, but the wear was less because of the high hardness compared to Example 2 in which the tempering temperature was 300 ° C. In addition, steel material 1 (M50), which was less worn due to the use of the grease of the example, was worn much in comparative example 7 using fluorine grease, and it was not grease increased with a fluorine-based resin and a urea compound. It can be said that the wear resistance characteristics cannot be fully utilized.
[0070]
(3) Fine wear test (friction of steel ball against plate)
In order to confirm the wear characteristics against microslip such as fretting, a fine wear test was performed using a fretting tester (manufactured by NTN). That is, one steel ball made of SUJ2 or having the composition shown in Table 3 was pressed against a flat plate test piece (20 mm square and 5 mm thick) of steel with a load of 98 N or 294 N, and the contact amplitude was 0.47 mm. The sample was slid back and forth at a frequency of 30 Hz for 8 hours (one repetition). After this test, (1) the wear depth of the flat plate and (2) the wear volume of the steel ball were measured.
[0071]
(1) The wear depth of the flat plate was determined by measuring five points perpendicular to the wear direction with a surface roughness meter (Tarisurf) and determining the maximum depth. (2) The wear volume V of the steel ball was determined from the wear scar diameter using the following formula, and the results are shown in Table 3. Incidentally, in this test, since the amount of rocking is small, it is difficult for the lubricant to intervene on the test surface, and wear is accelerated.
V = (πh ² × (3r−h)) / 3, h = r− (4r ² −C ² ) ^1/2 / 2 (where r = steel ball radius, h = steel ball wear) Depth, C = wear scar diameter.)
[0072]
[Table 3]

[0073]
As is clear from the results in Table 3, as in the case of the Fafner type test results, the wear of the flat plate and the steel ball was small in the combination of the examples. In particular, steel balls for sliding contact are formed with the composition of the example, and the carbonitriding or tempering temperature is low (Example 3a, Example 5 or 6) on the flat plate, and ceramic (Si ₃ N ₄ ) is used ( In Example 7), wear was particularly reduced.
[0074]
{Circle around (4)} Friction and Wear Test at High Temperature Evaluation was performed at 200 ° C. using a high temperature Sabang type friction and wear tester. The high temperature friction and wear tester (manufactured by NTN) has a wrapping finished flat plate (length 40mm, width 6mm, thickness 5mm) and rotating ring (outer diameter M50 made outer diameter 100mm, inner diameter 30mm, thickness This is an improvement of a Sabang type wear tester that presses 10 mm), and has a structure in which high-temperature lubricating oil is supplied to a friction surface at a high temperature to evaluate frictional wear at a high temperature. For the evaluation of grease, the test surface is maintained at 200 ° C. by heating high-temperature air and a flat plate sample instead of high-temperature lubricating oil, and evaluated at a load of 100 N and a rotation speed of 3000 rpm for a test time of 10 minutes (repetition number of 1 time). did.
[0075]
[Table 4]

[0076]
As is apparent from the test results shown in Table 4, the examples had very little wear and were excellent in friction and wear characteristics at high temperatures. Also in this case, carbonitriding was a good result. Further, the 180 ° C. tempered product could be evaluated because of its short heat resistance time during the test, but it was not significantly different from the high temperature tempered product. Example 7 which used ceramics (Si ₃ N ₄ ) as a test piece was a result of less wear than the examples of other steel test pieces.
[0077]
【The invention's effect】
As described above, according to the present invention, the inner ring and the outer ring are made of a steel material having a hardness of HRC 59 or higher tempered at a high temperature of 250 ° C. or higher, and the lubricating grease includes a predetermined base oil and a thickener. Encapsulated heat-resistant rolling bearings have a long and well-balanced bearing life (lubrication life and material fatigue life) at high temperatures, and there is no seizure or lubrication failure when the rolling bearing is intermittently operated at high temperatures and high loads. Especially, there is an advantage that it becomes a heat-resistant rolling bearing with a low wear level, a low noise level, and a long life at a high temperature and high load.
[0078]
In addition, carbonitriding of the bearing material ensures the surface hardness at high temperatures, and further increases the rolling life, fretting resistance, and wear resistance.
[0079]
Use of bearing steels made of certain components will give excellent cost performance, and use of ceramic rolling elements will provide stable and long-life and excellent wear resistance from room temperature to high temperature (200 ° C). become. Further, a steel material having a hardness of HRC 61 or higher by carbonitriding has a further excellent long life and wear resistance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heat-resistant rolling bearing of an embodiment.
1 Inner ring 2 Outer ring 3 Cage 4 Rolling element

Claims (5)

In a rolling bearing in which a plurality of rolling elements are interposed between an inner ring and an outer ring, and lubricating grease is sealed around the rolling elements,
The inner ring and the outer ring are made of a steel material having a hardness of HRC 59 or higher tempered at a high temperature of 250 ° C. or higher, and the lubricating grease is based on perfluoropolyether oil and synthetic oil, A grease-filled heat-resistant rolling bearing characterized by being a lubricating grease containing a particulate fluororesin and a urea compound as a thickener. Steel material is 0.6 to 1.3% by mass of C, 0.3 to 3.0% by mass of Si, 0.1 to 3.0% by mass of Ni, and 0.2 to 1.5% by mass of Mn. The grease-filled heat-resistant rolling bearing according to claim 1, which is an alloy steel material containing 0.3 to 5.0 mass% of Cr. The grease-filled heat-resistant rolling bearing according to claim 1 or 2, wherein the steel material is a steel material containing 0.05 to 1.0 mass% V and 0.05 to less than 0.25 mass% Mo. The grease-sealed heat-resistant rolling bearing according to any one of claims 1 to 3, wherein the inner ring and the outer ring are made of steel and the rolling elements are made of ceramics. The grease-sealed heat-resistant rolling bearing according to any one of claims 1 to 4, wherein a carbonitriding layer having a hardness of HV725 (HRC61) or higher is formed on a steel material surface.

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