JP6294618B2 - Hub bearing - Google Patents
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- JP6294618B2 JP6294618B2 JP2013197730A JP2013197730A JP6294618B2 JP 6294618 B2 JP6294618 B2 JP 6294618B2 JP 2013197730 A JP2013197730 A JP 2013197730A JP 2013197730 A JP2013197730 A JP 2013197730A JP 6294618 B2 JP6294618 B2 JP 6294618B2
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Description
本発明は、自動車の車輪を回転自在に支持するためのハブベアリングに関する。 The present invention relates to a hub bearing for rotatably supporting automobile wheels.
自動車用のハブベアリングはその用途から晴天での走行のみならず雨天、悪路、海岸での走行など使用環境が非常に悪い条件で使用される。ハブベアリング内への水分や異物の侵入はシールにより抑えられてはいるものの完全なものではない。したがって、ハブベアリング内に水分や異物が侵入し、そこに封入されているグリース等の潤滑剤に混入することは免れない。さらに、省エネの観点からハブベアリングの低トルク化が求められ、その方法の一つとしてシールの軽接触化が考えられる。したがって水が浸入する可能性がより高まることとなる。 Hub bearings for automobiles are used under extremely bad conditions such as driving on fine weather, rainy weather, rough roads, and coasts. Intrusion of moisture and foreign matter into the hub bearing is suppressed by the seal, but it is not perfect. Therefore, it is inevitable that moisture and foreign matter enter the hub bearing and mix into the lubricant such as grease enclosed therein. Further, from the viewpoint of energy saving, a reduction in the torque of the hub bearing is required, and as one of the methods, a light contact of the seal can be considered. Therefore, the possibility of water intrusion is further increased.
自動車用のハブベアリングは、このような水が潤滑剤等に混入する条件下や、急加減速などの過酷な使用条件下、すべりを伴う条件下などで使用されると、ハブベアリングの転走面に白色組織変化を伴った特異的な剥離が早期に生じ、長時間使用することが困難となる。この特異的な剥離は、通常の金属疲労により生じる転走面内部からの剥離と異なり、転走面表面の比較的浅いところから生じる破壊現象であり、水あるいは潤滑剤が分解して水素が発生し、それが鋼中に侵入することで、水素脆性を起因とする早期剥離が起こっていると考えられる。 When hub bearings for automobiles are used under such conditions that water is mixed into the lubricant, severe operating conditions such as sudden acceleration / deceleration, or conditions that involve slipping, rolling of the hub bearings occurs. Specific exfoliation accompanied by white tissue change occurs on the surface at an early stage, making it difficult to use for a long time. This specific delamination is a destructive phenomenon that occurs from a relatively shallow surface of the rolling surface, unlike the delamination from the inside of the rolling surface caused by normal metal fatigue. Hydrogen is generated by decomposition of water or lubricant. However, it is thought that early exfoliation due to hydrogen embrittlement occurs because it penetrates into the steel.
軸受におけるこのような早期に発生する白色組織変化を伴った特異な剥離現象を防ぐ方法として、鋼材にＣｒを多く添加することで鋼表面に不動態膜を形成し、鋼中への水素の侵入を抑制するものが提案されている（特許文献１参照）。 As a method to prevent such an unusual peeling phenomenon with a white structure change that occurs early in the bearing, a passive film is formed on the steel surface by adding a large amount of Cr to the steel material, and hydrogen enters the steel. The thing which suppresses is proposed (refer patent document 1).
しかしながら、特許文献１の鋼材では、Ｃｒを多く添加することで炭化物が粗大化し、それが応力集中源となって早期剥離が起きることがある。また、不動態膜は水素の拡散を遅くする効果はあるが、発生した水素が鋼表面に吸着するのを促進する効果も併せ持つ。ハブベアリングが間欠的に使われる場合は、停止時に水素が散逸しうるため、鋼中への水素の侵入を遅らせることは、早期剥離の防止に有効であることがある。しかしながら、連続して使われる場合は、不動態膜が多くの水素を吸着する分、鋼中に侵入する水素量が増すため、早期剥離が生じることになる。また、特殊鋼材はコスト高になり、また海外調達が困難である。これらの理由により、特許文献１の鋼材では、自動車用のハブべアリングにおける早期剥離を十分に抑制できず、その適用は困難である。 However, in the steel material of Patent Document 1, carbide is coarsened by adding a large amount of Cr, which may cause early peeling due to a stress concentration source. Moreover, the passive film has the effect of slowing the diffusion of hydrogen, but also has the effect of promoting the adsorption of the generated hydrogen on the steel surface. When the hub bearing is used intermittently, hydrogen can be dissipated at the time of stopping, so delaying the penetration of hydrogen into the steel may be effective in preventing early delamination. However, when used continuously, the amount of hydrogen that penetrates into the steel increases by the amount of hydrogen absorbed by the passive film, resulting in early peeling. Also, special steel materials are expensive and difficult to procure overseas. For these reasons, the steel material of Patent Document 1 cannot sufficiently suppress early peeling in the hub bearing for automobiles, and its application is difficult.
本発明はこのような問題に対処するためになされたものであり、ハブベアリング運転時に内部に水が混入するような過酷な使用条件下でも、転走面等の転がり接触部における水素脆性による剥離を効果的に防止できる、長時間使用可能なハブベアリングの提供を目的とする。 The present invention has been made in order to cope with such a problem, and peeling due to hydrogen embrittlement at a rolling contact portion such as a rolling surface even under severe use conditions in which water is mixed inside during operation of the hub bearing. It is an object to provide a hub bearing that can be effectively used for a long time.
本発明のハブベアリングは、自動車の車輪を回転支持するハブベアリングであって、該ハブベアリングの、少なくとも一つの、転がり接触部を有する構成部材は、鋼材からなっていて該鋼材中に含まれる酸化物系介在物の少なくとも一部がＭｎＳで覆われており、かつ、該鋼材中の最大径が３μｍ以上の上記酸化物系介在物において、その全個数に対するＭｎＳで覆われたものの個数の割合が４０％をこえることを特徴とする。 The hub bearing according to the present invention is a hub bearing that rotatably supports a wheel of an automobile, and at least one component member having a rolling contact portion of the hub bearing is made of a steel material and is contained in the steel material. In the oxide inclusions in which at least a part of the physical inclusions are covered with MnS and the maximum diameter in the steel material is 3 μm or more, the ratio of the number of the inclusions covered with MnS to the total number thereof is It is characterized by exceeding 40%.
ここで、「転がり接触部を有する構成部材」とは、ハブベアリングの他の構成部材と転がり接触をする部位を有する構成部材を意味し、例えば後述の図１に示すようなハブベアリングにおいて、転動体４と転がり接触する内輪２、転動体４と転がり接触するハブ輪１、転動体４と転がり接触する外方部材３、および、転動体４等をいう。内輪２、ハブ輪１、外方部材３が有する転走面は、転がり接触部である。 Here, the “constituent member having a rolling contact portion” means a constituent member having a portion that is in rolling contact with another constituent member of the hub bearing. For example, in a hub bearing as shown in FIG. It refers to the inner ring 2 that is in rolling contact with the moving body 4, the hub wheel 1 that is in rolling contact with the rolling element 4, the outer member 3 that is in rolling contact with the rolling element 4, and the rolling element 4. The rolling surfaces of the inner ring 2, the hub wheel 1, and the outer member 3 are rolling contact portions.
上記鋼材の成分組成は、Ｃ：０．９５質量％以上１．１質量％以下、Ｓｉ：０．３５質量％未満、Ｍｎ：０．５質量％未満、Ｓ：０．０２５質量％未満、Ｃｒ：１．４質量％以上１．６質量％未満、残部が鉄および不純物であることを特徴とする。 The composition of the steel material is as follows: C: 0.95 mass% or more and 1.1 mass% or less, Si: less than 0.35 mass%, Mn: less than 0.5 mass%, S: less than 0.025 mass%, Cr : 1.4% by mass or more and less than 1.6% by mass, the balance being iron and impurities.
上記構成部材は、その表層に窒化処理が施されてなり、表面窒素濃度が０．０５〜０．６重量％であることを特徴とする。 The constituent member is characterized by nitriding the surface layer and having a surface nitrogen concentration of 0.05 to 0.6% by weight.
上記構成部材の表面から０．０５ｍｍ深さの箇所と上記窒素が含まれていない深さの箇所とのビッカース硬度差ΔＨＶが６０以上であることを特徴とする。 A Vickers hardness difference ΔHV between a location having a depth of 0.05 mm from the surface of the constituent member and a location having a depth not containing nitrogen is 60 or more.
また、上記ハブベアリングは、内周に複列の外側転走面が形成された外方部材と、外周に該複列の外側転走面に対向する複列の内側転走面が形成された内方部材と、該両転走面間に収容された複列の転動体とを備えてなり、上記内方部材はハブ輪と内輪とを有し、上記ハブ輪は、一端部に車輪取付フランジを一体に有して、外周に上記複列の外側転走面の一方に対向する内側転走面と、この内側転走面から軸方向に延びる小径段部とが形成されており、上記内輪は、外周に上記複列の外側転走面の他方に対向する内側転走面が形成されていて、上記ハブ輪の小径段部に圧入されており、上記小径段部の端部を径方向外方に塑性変形させて形成した加締部により、上記内輪は上記ハブ輪に対して固定されており、上記内輪は、上記構成部材であることを特徴とする。 The hub bearing has an outer member having a double row outer rolling surface formed on the inner periphery, and a double row inner rolling surface facing the outer rolling surface of the double row on the outer periphery. An inner member and a double row rolling element accommodated between the rolling surfaces, the inner member having a hub ring and an inner ring, and the hub ring is attached to one end of the wheel. An inner rolling surface that has a flange integrally and faces one of the outer rolling surfaces of the double row on the outer periphery, and a small-diameter step portion that extends in the axial direction from the inner rolling surface is formed. The inner ring has an inner rolling surface facing the other of the double-row outer rolling surfaces on the outer periphery, and is press-fitted into the small-diameter step portion of the hub wheel, and the end of the small-diameter step portion has a diameter. The inner ring is fixed to the hub ring by a caulking portion formed by plastic deformation outward in the direction, and the inner ring is the component member. It is characterized in.
本発明のハブベアリングは、自動車の車輪を回転支持するハブベアリングであって、該ハブベアリングの、少なくとも一つの、転がり接触部を有する構成部材が、鋼材からなっていて該鋼材中に含まれる酸化物系介在物の少なくとも一部がＭｎＳで覆われており、かつ、該鋼材中の最大径が３μｍ以上の該酸化物系介在物において、その全個数に対するＭｎＳで覆われたものの個数の割合が４０％をこえる。このように、構成部材の鋼材中に不可避に含まれる酸化物系介在物の多くが軟らかいＭｎＳで覆われていることにより、酸化物系介在物の周りに形成される引張応力場が緩和される。このため、鋼材内部に水素が集積しにくく、水素脆性を起因とする早期剥離を防止することができる。この結果、ハブベアリング運転時に内部（例えば、グリース中）に水が混入するような過酷な使用条件下でも、長寿命を持つハブベアリングとして好適に使用できる。 A hub bearing according to the present invention is a hub bearing that rotatably supports a wheel of an automobile, and at least one of the components having a rolling contact portion of the hub bearing is made of a steel material and is contained in the steel material. In the oxide inclusions in which at least part of the inclusions is covered with MnS and the maximum diameter in the steel material is 3 μm or more, the ratio of the number of the inclusions covered with MnS to the total number thereof is Over 40%. As described above, most of the oxide inclusions inevitably contained in the steel materials of the constituent members are covered with the soft MnS, thereby relaxing the tensile stress field formed around the oxide inclusions. . For this reason, it is difficult for hydrogen to accumulate in the steel material, and early peeling due to hydrogen embrittlement can be prevented. As a result, it can be suitably used as a hub bearing having a long life even under severe usage conditions in which water is mixed inside (for example, in grease) during operation of the hub bearing.
自動車の車輪を回転支持するハブベアリングにおける耐水素脆性を向上させるため、内輪、ハブ輪、外方部材、転動体等の転がり接触部の材料である鋼材に不可避に含まれる酸化物系介在物に着目した。転がり接触部にすべりなどで摩耗が生じれば、新生面が形成され、混入した水や潤滑剤が分解し、水素が発生する。発生した水素の一部は、鋼中に侵入する。酸化物系介在物の周りには、引張応力場が形成される。水素は、引張応力場に集積する性質がある。これに対して、酸化物系介在物の多くを（４０％をこえる）軟らかいＭｎＳ（約１５０ＨＶ）で覆うことで、上記引張応力場を緩和し、水素を集積しにくくした。その結果、耐水素脆性が向上することを見出した。本発明はこのような知見に基づくものである。 In order to improve hydrogen embrittlement resistance in hub bearings that support the rotation of automobile wheels, oxide inclusions inevitably contained in steel materials that are rolling contact parts such as inner rings, hub rings, outer members, and rolling elements Pay attention. If wear occurs due to slippage or the like at the rolling contact portion, a new surface is formed, the mixed water and lubricant are decomposed, and hydrogen is generated. Part of the generated hydrogen penetrates into the steel. A tensile stress field is formed around the oxide inclusions. Hydrogen has the property of accumulating in the tensile stress field. On the other hand, most of the oxide inclusions were covered with soft MnS (over 40%) (about 150 HV) to relax the tensile stress field and make it difficult to accumulate hydrogen. As a result, it has been found that hydrogen embrittlement resistance is improved. The present invention is based on such knowledge.
特に、鋼材中に侵入する水素の中でも、拡散性水素が水素脆性の原因と考えられている。拡散性水素は、結晶粒界などにトラップされていない比較的自由に動き得る水素のことをいう。この拡散性水素は、室温で時間と共に鋼材中から外に放出されるものである。例えば、拡散性水素は、２００℃までの加熱で放出される水素と定義でき、非拡散性水素は、２００℃をこえる加熱温度ではじめて鋼材中から放出される水素と定義でき、拡散性水素と非拡散性水素との合計量が、鋼材中に侵入した水素の総量である。 In particular, diffusible hydrogen is considered to be a cause of hydrogen embrittlement among hydrogen that penetrates into steel materials. Diffusible hydrogen refers to hydrogen that is not trapped in a grain boundary or the like and can move relatively freely. This diffusible hydrogen is released out of the steel material with time at room temperature. For example, diffusible hydrogen can be defined as hydrogen released by heating up to 200 ° C., and non-diffusible hydrogen can be defined as hydrogen released from steel material only at a heating temperature exceeding 200 ° C. The total amount of non-diffusible hydrogen is the total amount of hydrogen that has penetrated into the steel material.
ハブベアリングの構成部材の材料である鋼材中において、酸化物系介在物は不可避的に含まれる。本発明のハブベアリングでは、少なくとも一つの、転がり接触部を有する構成部材の、鋼材中の最大径が３μｍ以上の酸化物系介在物において、その全個数に対するＭｎＳで覆われたものの個数の割合（被覆率）が４０％をこえることを必須としている。被覆率を式で表すと以下のとおりとなる。
被覆率（％）＝（最大径が３μｍ以上の酸化物系介在物の中でＭｎＳで覆われた酸化物系介在物の個数）／（最大径が３μｍ以上の酸化物系介在物の全個数）×１００
また、被覆率は高い方が好ましく、５０％以上がより好ましく、９０％以上がさらに好ましい。ここで、ＭｎＳで覆われているとは、ＭｎＳが酸化物系介在物を核として析出し、この酸化物系介在物の周りに巻き付いたような状態をいい、酸化物系介在物の周囲が完全に覆われている場合のみならず一部が覆われている場合を含む。また、ＭｎＳは圧延方向に引き伸ばされた線形状である。
Oxide inclusions are inevitably included in the steel material, which is the material of the component of the hub bearing. In the hub bearing of the present invention, the ratio of the number of the constituent members having rolling contact portions covered with MnS to the total number of oxide inclusions having a maximum diameter of 3 μm or more in the steel material ( It is essential that the covering ratio) exceeds 40%. The coverage is represented by the following formula.
Coverage (%) = (number of oxide inclusions covered with MnS among oxide inclusions having a maximum diameter of 3 μm or more) / (total number of oxide inclusions having a maximum diameter of 3 μm or more) ) × 100
Moreover, the one where a coverage is high is preferable, 50% or more is more preferable, and 90% or more is further more preferable. Here, being covered with MnS means a state in which MnS is precipitated with oxide inclusions as nuclei and wound around the oxide inclusions. This includes not only the case of being completely covered but also the case of being partially covered. Further, MnS has a linear shape drawn in the rolling direction.
被覆率の算出において、対象とする酸化物系介在物を、その最大径が３μｍ以上のものとしている。最大径が３μｍ未満の微細な酸化物系介在物の存在状態（ＭｎＳの被覆状態）は水素脆性を起因とする早期剥離にほぼ寄与しない。また、最大径が３μｍ以上の酸化物系介在物は、光学顕微鏡によりその存在状態を容易に測定可能である。 In the calculation of the coverage, the target oxide inclusions have a maximum diameter of 3 μm or more. The presence state of fine oxide inclusions having a maximum diameter of less than 3 μm (covering state of MnS) hardly contributes to early peeling due to hydrogen embrittlement. The presence of oxide inclusions having a maximum diameter of 3 μm or more can be easily measured with an optical microscope.
また、対象とする酸化物系介在物の最大径の下限値をより大きくしてもよく、例えば、５μｍ以上、１０μｍ以上としてもよい。最大径が３μｍ以上の酸化物系介在物であれば、その最大径の下限値を大きくしても、上記被覆率は略同一となる。 Moreover, the lower limit value of the maximum diameter of the target oxide inclusions may be increased, for example, 5 μm or more and 10 μm or more. In the case of an oxide-based inclusion having a maximum diameter of 3 μm or more, the coverage is substantially the same even if the lower limit of the maximum diameter is increased.
酸化物系介在物のＭｎＳによる被覆率を上記範囲とする製造方法等は特に限定されない。一般的に、鋼材を連続鋳造する際のように冷却速度が速い場合には、酸化物系介在物と軟質介在物であるＭｎＳとが別々に析出し、被覆率は低くなりやすい。一方、鋼材をインゴット鋳造する際のように冷却速度が遅い場合には、酸化物系介在物が軟質介在物であるＭｎＳの析出の核となり、被覆率が高くなりやすい。 There is no particular limitation on the production method or the like in which the oxide inclusion inclusion coverage with MnS is within the above range. In general, when the cooling rate is high as in the case of continuous casting of steel, oxide inclusions and soft inclusions MnS precipitate separately, and the coverage tends to be low. On the other hand, when the cooling rate is slow as in the case of ingot casting of steel, the oxide inclusions become the core of precipitation of MnS, which is a soft inclusion, and the coverage tends to increase.
本発明において、上述の転がり接触部を有する構成部材に用いる鋼材の成分組成は、Ｃ：０．９５質量％以上１．１質量％以下、Ｓｉ：０．３５質量％未満、Ｍｎ：０．５質量％未満、Ｓ：０．０２５質量％未満、Ｃｒ：１．４質量％以上１．６質量％未満、残部が鉄および不純物であることが好ましい。上記成分組成の詳細を以下に説明する。 In this invention, the component composition of the steel material used for the structural member which has the above-mentioned rolling contact part is C: 0.95 mass% or more and 1.1 mass% or less, Si: Less than 0.35 mass%, Mn: 0.5 It is preferable that less than mass%, S: less than 0.025 mass%, Cr: 1.4 mass% or more and less than 1.6 mass%, and the balance being iron and impurities. The detail of the said component composition is demonstrated below.
Ｃ：０．９５質量％以上１．１質量％以下
Ｃ（炭素）は、鋼材の強度確保に必要な元素である。また、焼入性への影響も大きく、焼入硬化層の硬さおよび深さを高めて疲労強度の向上にも寄与する。上記範囲では、これらの効果を十分に得られる。
C: 0.95 mass% or more and 1.1 mass% or less C (carbon) is an element required for ensuring the strength of the steel material. In addition, the hardenability is greatly affected, and the hardness and depth of the hardened hardened layer is increased to contribute to the improvement of fatigue strength. Within the above range, these effects can be sufficiently obtained.
Ｓｉ：０．３５質量％未満
Ｓｉ（珪素）は、焼入加熱時にオーステナイト粒成長を抑制するため、本来は積極的に添加したいが、Ｓｉの添加により鍛造性、被削性が著しく劣化する。これらの観点より、０．３５質量％未満とする。
Si: Less than 0.35% by mass Si (silicon) is originally intended to be added positively in order to suppress austenite grain growth during quenching heating, but forgeability and machinability are significantly degraded by the addition of Si. From these viewpoints, the content is less than 0.35% by mass.
Ｍｎ：０．５質量％未満
Ｍｎ（マンガン）は、強度および焼き入れ性の向上に有効に寄与する元素である。また、Ｍｎが過剰であると、粒界に偏析して粒界割れを引き起こすと考えられるため、０．５質量％未満が適当である。
Mn: Less than 0.5% by mass Mn (manganese) is an element that contributes effectively to improving strength and hardenability. Further, if Mn is excessive, it is considered that segregation occurs at the grain boundary and causes grain boundary cracking, and therefore, less than 0.5% by mass is appropriate.
Ｓ：０．０２５質量％未満
Ｓ（硫黄）は、鋼材中でＭｎＳを形成する元素である。一方でオーステナイトの粒界に偏析し、粒界強度を低下させ、疲労強度を低下させるおそれもある。これらの観点より、０．０２５質量％未満とする。
S: Less than 0.025 mass% S (sulfur) is an element that forms MnS in a steel material. On the other hand, it segregates at the grain boundaries of austenite, which may reduce the grain boundary strength and reduce the fatigue strength. From these viewpoints, the content is less than 0.025% by mass.
Ｃｒ：１．４質量％以上１．６質量％未満
Ｃｒ（クロム）は、安定した炭化物を形成し、また焼入性を向上させて、強度、耐摩耗性、疲労強度の向上に寄与する元素である。一方、Ｃｒが過剰に含有されれば、鍛造性および被削性が低下する。これらの効果を十分に得るためには、上記範囲が適当である。
Cr: 1.4% by mass or more and less than 1.6% by mass Cr (chromium) is an element that forms stable carbides and improves hardenability and contributes to improvement in strength, wear resistance, and fatigue strength. It is. On the other hand, if Cr is excessively contained, forgeability and machinability are lowered. In order to sufficiently obtain these effects, the above range is appropriate.
上記成分組成を有する鋼材としては、例えば、高炭素クロム軸受鋼ＳＵＪ２（ＪＩＳ規格）、ＳＵＪ２相当材である５２１００（ＡＩＳＩまたはＳＡＥ規格）、１００Ｃｒ６（ＤＩＮ規格）、ＧＣｒ１５（ＧＳＢ規格）等に準じたもの挙げられる。上記成分組成を満たす各鋼材であっても、上述の所定の被覆率（％）を満たさないものは本発明のハブベアリングには使用できない。本発明のハブベアリングでは、上述の所定の被覆率（％）を満たし、かつ、上記成分組成を満たす鋼材を用いることが好ましい。 As the steel material having the above component composition, for example, high carbon chromium bearing steel SUJ2 (JIS standard), SUJ2 equivalent material 52100 (AISI or SAE standard), 100Cr6 (DIN standard), GCr15 (GSB standard), etc. There are things. Even steel materials satisfying the above component composition cannot be used in the hub bearing of the present invention if they do not satisfy the above-mentioned predetermined coverage (%). In the hub bearing of the present invention, it is preferable to use a steel material that satisfies the above-described predetermined coverage (%) and satisfies the above-described component composition.
本発明において、ハブベアリングの、少なくとも一つの、転がり接触部を有する構成部材に用いる鋼材は、表層に窒化処理を施すことが好ましい。内輪、ハブ輪、外方部材（軌道輪）については、該軌道輪の転走面に窒化処理を施す。窒化処理は、例えば、８５０℃の温度でＲＸガスにアンモニアガスを添加した雰囲気中で行われる。転走面に窒化処理を施して焼入することで、軌道輪が塑性変形しにくくなり、耐水素脆性が向上する。転走面の表面窒素濃度は、０．０５〜０．６重量％であることが好ましい。０．０５重量％未満では窒化による寿命向上の効果は得られない場合がある。一方、表面窒素濃度が０．６重量％をこえると、Ｃｒ炭窒化物が多く生成されるため、焼入性に寄与するＣｒ量が欠乏し、十分な焼入性が確保できないおそれがある。 In the present invention, it is preferable that the steel layer used for the structural member having the rolling contact portion of the hub bearing is subjected to nitriding treatment on the surface layer. For the inner ring, the hub ring, and the outer member (track ring), nitriding treatment is applied to the rolling surface of the track ring. The nitriding treatment is performed, for example, in an atmosphere in which ammonia gas is added to RX gas at a temperature of 850 ° C. By performing nitriding treatment on the rolling surface and quenching, the raceway is less likely to be plastically deformed and the hydrogen embrittlement resistance is improved. The surface nitrogen concentration on the rolling surface is preferably 0.05 to 0.6% by weight. If it is less than 0.05% by weight, the effect of improving the life by nitriding may not be obtained. On the other hand, when the surface nitrogen concentration exceeds 0.6% by weight, a large amount of Cr carbonitride is produced, so that the amount of Cr contributing to hardenability is deficient and sufficient hardenability may not be ensured.
窒化処理を施して焼入し、その後焼戻する。熱処理（焼入・焼戻条件）は、特に限定されず公知の条件を採用できる。例えば、まず、鋼材をＡ１点以上の所定の温度に加熱し、所定時間保持する。このとき、鋼材は、ＲＸガスにアンモニアガスを添加した雰囲気中等において加熱し、これにより鋼材表層に窒化処理を施す。その後、鋼材を油中等に浸漬することで、Ａ１点以上の温度からＭＳ点以下の温度に冷却し、焼入硬化工程が完了する。さらに、焼入硬化された鋼材をＡ１点以下の温度である所定温度に加熱し、所定時間保持した後、例えば室温まで空冷することにより焼戻工程が完了する。以上の工程により、熱処理が完了する。 Quenching is performed after nitriding, and then tempering. The heat treatment (quenching / tempering conditions) is not particularly limited, and known conditions can be adopted. For example, first, the steel material is heated to a predetermined temperature of point A1 or higher and held for a predetermined time. At this time, the steel material is heated in an atmosphere in which ammonia gas is added to RX gas or the like, thereby nitriding the steel material surface layer. Then, by immersing the steel material in oil or the like, the steel material is cooled from a temperature of A1 point or higher to a temperature of MS point or lower, and the quench hardening process is completed. Furthermore, the tempering process is completed by heating the quench-hardened steel material to a predetermined temperature which is a temperature of A1 or lower, holding the steel material for a predetermined time, and then air-cooling it to room temperature, for example. Through the above steps, the heat treatment is completed.
本発明のハブベアリングは、その潤滑に用いる潤滑油中や、使用雰囲気中に水分が混入・侵入する環境下で用いられる場合が多い。また、ハブベアリングは、その運動形態から、接触要素間で金属接触が起こり、すべりを伴う条件などで使用されるため、鋼材部材表面における金属新生面の露出により水素が鋼材中に侵入しやすい等、水素の影響を受けやすい部品である。 The hub bearing of the present invention is often used in a lubricating oil used for lubrication or in an environment in which moisture is mixed / invaded in a use atmosphere. In addition, because the hub bearing is used in a condition in which metal contact occurs between the contact elements due to its motion form and slipping occurs, hydrogen easily enters the steel due to the exposure of the new metal surface on the steel member surface, etc. It is a component that is susceptible to hydrogen.
本発明のハブベアリングの一例（従動輪用第三世代ハブベアリング）を図１に示す。図１は、ハブベアリングの断面図である。ハブベアリング６は、ハブ輪１および内輪２を有する内方部材５と、外輪である外方部材３と、複列の転動体４、４とを備えている。ハブ輪１はその一端部に車輪（図示せず）を取付けるための車輪取付けフランジ１ｄを一体に有し、外周に内側転走面１ａと、この内側転走面１ａから軸方向に延びる小径段部１ｂとが形成されている。本明細書においては、軸方向に関して「外」とは、車両への組付け状態で幅方向外側をいい、「内」とは、幅方向中央側をいう。上記の小径段部１ｂは、内側転走面１ａから軸方向内側に位置する。 An example of the hub bearing of the present invention (third generation hub bearing for a driven wheel) is shown in FIG. FIG. 1 is a cross-sectional view of a hub bearing. The hub bearing 6 includes an inner member 5 having a hub wheel 1 and an inner ring 2, an outer member 3 that is an outer ring, and double-row rolling elements 4 and 4. The hub wheel 1 integrally has a wheel mounting flange 1d for mounting a wheel (not shown) at one end thereof, an inner rolling surface 1a on the outer periphery, and a small diameter step extending in the axial direction from the inner rolling surface 1a. Part 1b is formed. In the present specification, “outside” in the axial direction means the outside in the width direction when assembled to the vehicle, and “inside” means the center in the width direction. Said small diameter step part 1b is located in the axial direction inner side from the inner side rolling surface 1a.
ハブ輪１の小径段部１ｂには、外周に内側転走面２ａが形成された内輪２が圧入されている。そして、ハブ輪１の小径段部１ｂの端部を径方向外方に塑性変形させて形成した加締部１ｃにより、ハブ輪１に対して内輪２が軸方向へ抜けるのを防止している。外方部材３は、外周に車体取付けフランジ３ｂを一体に有し、内周に外側転走面３ａ、３ａと、これら複列の外側転走面３ａ、３ａに対向する内側転走面１ａ、２ａとの間には複列の転動体４、４が転動自在に収容されている。 An inner ring 2 having an inner rolling surface 2a formed on the outer periphery is press-fitted into the small-diameter step portion 1b of the hub wheel 1. The inner ring 2 is prevented from coming off in the axial direction with respect to the hub wheel 1 by a crimped portion 1c formed by plastically deforming the end of the small-diameter stepped portion 1b of the hub wheel 1 radially outward. . The outer member 3 integrally has a vehicle body mounting flange 3b on the outer periphery, an outer rolling surface 3a, 3a on the inner periphery, and an inner rolling surface 1a facing the double row outer rolling surfaces 3a, 3a, Two rows of rolling elements 4 and 4 are accommodated between 2a so as to roll freely.
グリースを、シール部材７と、外方部材３と、シール部材８と、内方部材５と、ハブ輪１とに囲まれた空間に封入でき、外方部材３と、内方部材５とに挟まれた複列の転動体４、４の周囲を被覆し、転動体４、４の転動面と、内側転走面１ａ、２ａおよび外側転走面３ａ、３ａとの転がり接触の潤滑に供される。 Grease can be enclosed in a space surrounded by the seal member 7, the outer member 3, the seal member 8, the inner member 5, and the hub wheel 1, and the outer member 3 and the inner member 5 Covers the periphery of the sandwiched double-row rolling elements 4 and 4, and lubricates rolling contact between the rolling surfaces of the rolling elements 4 and 4 and the inner rolling surfaces 1a and 2a and the outer rolling surfaces 3a and 3a. Provided.
本発明のハブベアリングにおいて、上述の所定の鋼材からなる構成部材以外の構成部材に使用する材質としては、軸受鋼、浸炭鋼、または機械構造用炭素鋼を挙げることができる。これらの中で鍛造性が良く安価なＳ５３Ｃなどの機械構造用炭素鋼を用いることが好ましい。該炭素鋼は一般に高周波熱処理を施すことで、転がり疲労強度を確保した上で用いられる。 In the hub bearing of the present invention, examples of the material used for the constituent members other than the constituent members made of the above-described predetermined steel materials include bearing steel, carburized steel, and carbon steel for machine structure. Among these, it is preferable to use carbon steel for mechanical structure such as S53C which has good forgeability and is inexpensive. The carbon steel is generally used after high-temperature heat treatment is performed to ensure rolling fatigue strength.
例えば、（１）内輪２は酸化物系介在物をＭｎＳで覆った上述の所定の鋼材から形成され、（２）ハブ輪１はＳ５３Ｃなどの機械構造用炭素鋼で形成されて、内側転走面１ａをはじめ、シール部材７が摺接するシールランド部、および小径段部１ｂが高周波焼入れによって表面硬さが５８〜６４ＨＲＣの範囲にあり、（３）外方部材３はＳ５３Ｃなどの機械構造用炭素鋼で形成されて、複列の外側転走面３ａ、３ａをはじめ、シール部材７、８が嵌合する端部内径面が高周波焼入れによって表面硬さが５８〜６４ＨＲＣの範囲にある、という構成が考えられる。 For example, (1) the inner ring 2 is formed of the above-mentioned predetermined steel material in which oxide inclusions are covered with MnS, and (2) the hub ring 1 is formed of carbon steel for machine structural use such as S53C and is inwardly rolled. The surface land has a surface hardness in the range of 58 to 64 HRC by induction hardening, including the surface 1a, the seal land portion with which the seal member 7 is in sliding contact, and the small diameter step portion 1b. (3) The outer member 3 is for mechanical structures such as S53C It is formed of carbon steel, and the inner surface of the end portion into which the sealing members 7 and 8 are fitted, including the double row outer rolling surfaces 3a and 3a, has a surface hardness in the range of 58 to 64 HRC by induction hardening. Configuration is conceivable.
本発明のハブベアリングを、転がり接触部を有する構成部材に用いる鋼材の点から、実施例により具体的に説明するが、これらの例によって何ら限定されるものではない。 The hub bearing of the present invention will be described in detail with reference to examples from the viewpoint of steel materials used for components having rolling contact portions, but is not limited to these examples.
＜化学成分分析＞
表１に、実施例および比較例の鋼材について、それぞれの化学成分を示す。比較例１の鋼材は連続鋳造により、実施例１〜３の鋼材はインゴット鋳造により、それぞれ製造したものである。表中の被覆率は、後述の介在物検査結果における、酸化系介在物がＭｎＳによって覆われていた割合（％）である。比較例１（従来鋼）と実施例１〜３（開発鋼）とで化学成分自体に大きな違いはないが、被覆率は異なる。
Table 1 shows chemical components of the steel materials of Examples and Comparative Examples. The steel material of Comparative Example 1 was manufactured by continuous casting, and the steel materials of Examples 1 to 3 were manufactured by ingot casting. The coverage in the table is the ratio (%) in which the oxidized inclusions were covered with MnS in the inclusion inspection results described later. There is no significant difference in the chemical composition itself between Comparative Example 1 (conventional steel) and Examples 1 to 3 (developed steel), but the coverage is different.
＜介在物検査＞
介在物検査は、鋼材断面の３０ｍｍ×３０ｍｍの面積（被検面積９００ｍｍ2）を観察して検出された酸化物系介在物（最大径が３μｍ以上のもの）のうち、それぞれがＭｎＳで覆われているかを判断した。ここで、鋼材断面（表面）を観察して検出された酸化物系介在物とは、該断面（表面）に露出している酸化物系介在物である。比較例１（上図）および実施例１（下図）の代表例の写真を図２に、実施例２（上図）および実施例３（下図）の代表例の写真を図３に、それぞれ示す。各図において、各サンプル略中央の黒点またはこれが引き伸ばされたものが酸化物系介在物であり、その周囲を覆う薄い線状物がＭｎＳである。
<Inclusion inspection>
In the inclusion inspection, each of the oxide inclusions (with a maximum diameter of 3 μm or more) detected by observing a 30 mm × 30 mm area (test area 900 mm 2 ) of the steel cross section is covered with MnS. Judged whether or not. Here, the oxide inclusions detected by observing the steel material cross section (surface) are oxide inclusions exposed on the cross section (surface). A photograph of a representative example of Comparative Example 1 (upper figure) and Example 1 (lower figure) is shown in FIG. 2, and a photograph of a representative example of Example 2 (upper figure) and Example 3 (lower figure) is shown in FIG. . In each figure, the black spot at the approximate center of each sample or a stretched one is an oxide inclusion, and the thin line covering the periphery is MnS.
比較例１は４０７１個中９８８個（被覆率２４％）、実施例１は３９８５個中１６２０個（被覆率４１％）、実施例２は４１０３個中２１３７個（被覆率５２％）、実施例３は４２６７個中４００５個（被覆率９４％）が、ＭｎＳで覆われていた。 Comparative Example 1 is 988 out of 4071 (coverage 24%), Example 1 is 1620 out of 3985 (coverage 41%), and Example 2 is 2137 out of 4103 (coverage 52%). 3 was covered with MnS in 4005 out of 4267 (coverage 94%).
＜超音波軸荷重疲労試験＞
超音波軸荷重疲労試験は、超音波振動により試験片を共振状態にして、繰返し応力を発生させ、試験片の疲労強度を短時間で求めることができる疲労試験である。このため、鋼材中に侵入した水素が散逸する前に疲労させることが可能であり、水素の影響を合理的に評価できる。比較例１および実施例１〜３の鋼材を用いて、図４に示す形状の超音波軸荷重疲労試験片を製作した。なお、図４中の数値単位はｍｍである。熱処理は、いずれについても、８５０℃のＲＸガス雰囲気中で５０分加熱して、８０℃の油中でずぶ焼入を施した後、１８０℃で１２０分の焼戻を施した。
<Ultrasonic axial load fatigue test>
The ultrasonic axial load fatigue test is a fatigue test in which a test piece is brought into a resonance state by ultrasonic vibration, repeated stress is generated, and the fatigue strength of the test piece can be obtained in a short time. For this reason, it is possible to fatigue before the hydrogen which penetrate | invaded in steel materials dissipates, and the influence of hydrogen can be rationally evaluated. Using the steel materials of Comparative Example 1 and Examples 1 to 3, ultrasonic axial load fatigue test pieces having the shape shown in FIG. 4 were produced. The numerical unit in FIG. 4 is mm. In each of the heat treatments, heating was performed in an RX gas atmosphere at 850 ° C. for 50 minutes, followed by quenching in oil at 80 ° C., followed by tempering at 180 ° C. for 120 minutes.
超音波軸荷重疲労試験を開始する前に、鋼中水素量が５ｍａｓｓ−ｐｐｍとなる電流密度で２０時間の陰極電解水素チャージを施し、その後、１０分後に試験した（チャージあり）。また、水素チャージなしでの試験も行った（チャージなし）。図５に超音波軸荷重疲労試験結果を示す。図５において、横軸は負荷回数であり、縦軸は応力振幅（ＭＰａ）である。比較例１（従来鋼）はチャージすることで、疲労強度が明らかに低下したのに対し、実施例１〜３（開発鋼）は、水素チャージなしよりも若干低下する程度であった。この結果より、実施例１〜３（開発鋼）は比較例１（従来鋼）と比較して、破壊の起点になる酸化物系介在物のまわりに水素が集積しにくい特性を有するといえる。 Before starting the ultrasonic axial load fatigue test, a cathode electrolytic hydrogen charge was applied for 20 hours at a current density at which the hydrogen content in the steel was 5 mass-ppm, and then the test was conducted 10 minutes later (with charge). A test without hydrogen charge was also conducted (no charge). FIG. 5 shows the results of the ultrasonic axial load fatigue test. In FIG. 5, the horizontal axis represents the number of loads, and the vertical axis represents the stress amplitude (MPa). In comparison example 1 (conventional steel), the fatigue strength was clearly reduced by charging, while in examples 1 to 3 (development steel) was slightly lower than that without hydrogen charging. From these results, it can be said that Examples 1 to 3 (developed steel) have characteristics that hydrogen is less likely to accumulate around oxide inclusions that are the starting points of fracture, as compared with Comparative Example 1 (conventional steel).
＜スラスト型寿命試験（転がり疲労試験）＞
ハブベアリングが自動車に用いられる際には、水が混入する転がり接触条件下では水が分解して水素が発生し、それが鋼中に侵入して早期剥離が起きる。そこで、水混入油中での転がり疲労試験を行った。比較例１および実施例１の鋼材を用いて、スラスト軸受５１１０６の内外輪を製作した。それぞれ試験片１（比較例１）と試験片２（実施例１）とする。熱処理は、いずれも８５０℃のＲＸガス雰囲気中で５０分加熱し、８０℃の油でずぶ焼入を施した後、１８０℃で１２０分の焼戻を施した。また、実施例１の鋼材については、８５０℃のＲＸガス雰囲気中にアンモニアガスを添加したものも製作した。これを試験片３（実施例１＋窒化処理）とする。
<Thrust type life test (rolling fatigue test)>
When a hub bearing is used in an automobile, water is decomposed to generate hydrogen under rolling contact conditions in which water is mixed, and hydrogen is generated, which penetrates into steel and causes early peeling. Therefore, a rolling fatigue test was performed in water-mixed oil. Using the steel materials of Comparative Example 1 and Example 1, the inner and outer rings of the thrust bearing 51106 were manufactured. Test piece 1 (Comparative Example 1) and test piece 2 (Example 1) are used. In each heat treatment, heating was performed in an RX gas atmosphere at 850 ° C. for 50 minutes, and after quenching with oil at 80 ° C., tempering was performed at 180 ° C. for 120 minutes. Moreover, about the steel material of Example 1, what added ammonia gas in 850 degreeC RX gas atmosphere was also manufactured. This is designated as test piece 3 (Example 1 + nitriding treatment).
ＶＧ１５０のポリグリコール系合成油（密度１．０７３ｇ／ｃｍ3、４０℃における動粘度１５０ｍｍ2／ｓ、１００℃における動粘度２３．６ｍｍ2／ｓ）に４０±０．０１重量％の純水を混入した。水混入油作製後、水が蒸発しないように食品包装用の薄いフィルムで封をし、３０分以上スターラーで攪拌した後、２００ｍＬの水混入油浴中で、上記試験片の内外輪を用いたスラスト軸受５１１０６を回転させる試験を行なった。ここで、ボールは、ＳＵＳ４４０Ｃ製のものを１２個用いた。保持器は１２個のボールを等間隔で保持する樹脂製のものを用いた。アキシャル荷重Ｆａ＝５．１０ｋＮのみを作用させ、０〜２５００ｍｉｎ-1で内輪を急加減速させた。図６に運転パターンを示す。この荷重条件での弾性ヘルツ接触計算でのレース面と鋼球間の最大接触面圧は２．３ＧＰａである。なお、弾性ヘルツ接触計算では、５１１０６、およびＳＵＳ４４０Ｃ製鋼球のヤング率とポアソン比はそれぞれＥ＝２０４ＧＰａ、ν＝０．２９とした。剥離の検出は振動計で行なった。 VG150 polyglycol synthetic oil (density 1.073 g / cm 3 , kinematic viscosity at 40 ° C. 150 mm 2 / s, kinematic viscosity at 100 ° C. 23.6 mm 2 / s) with 40 ± 0.01 wt% pure water It was mixed. After making the water-mixed oil, seal with a thin film for food packaging so that water does not evaporate, stir with a stirrer for 30 minutes or more, and then use the inner and outer rings of the above test piece in a 200 mL water-mixed oil bath A test for rotating the thrust bearing 51106 was performed. Here, 12 balls made of SUS440C were used. A cage made of resin that holds 12 balls at equal intervals was used. Only the axial load Fa = 5.10 kN was applied, and the inner ring was suddenly accelerated or decelerated at 0 to 2500 min −1 . FIG. 6 shows an operation pattern. The maximum contact surface pressure between the race surface and the steel ball in the elastic Hertz contact calculation under this load condition is 2.3 GPa. In the elastic Hertz contact calculation, the Young's modulus and Poisson's ratio of 51106 and SUS440C steel balls were E = 204 GPa and ν = 0.29, respectively. The peeling was detected with a vibrometer.
試験は、試験片２（実施例１）、試験片３（実施例１＋窒化処理）、試験片１（比較例１）のいずれも５個ずつ用意して行なった。剥離は、すべて５１１０６内輪あるいは外輪のレース面に生じ、すべて水素起因の特徴を有する剥離であった。 The test was performed by preparing five pieces of each of the test piece 2 (Example 1), the test piece 3 (Example 1 + nitriding treatment), and the test piece 1 (Comparative Example 1). All peeling occurred on the race surface of the inner ring or outer ring 51106, and all peeling was characterized by hydrogen.
表２に、各試験片の剥離寿命を２母数ワイブル分布に当てはめて求めたＬ１０、Ｌ５０、およびワイブルスロープ（形状母数）ｅを示す。試験片１（比較例１）は、Ｌ１０＝３８．５時間であった。それに対し、試験片２（実施例１）はＬ１０＝１１８．８時間であり、試験片１（比較例１）に対して約３倍の長寿命を示した。このことから、本発明のハブベアリングは、水素脆性起因の早期剥離を起きにくくする効果を有するといえる。また、試験片３（実施例１＋窒化処理）は、Ｌ１０＝１８３．４時間であり、試験片１（比較例１）に対して約５倍の長寿命を示した。このことから、試験片２（実施例１）に窒化処理を加えることで、より水素脆性起因の早期剥離を起きにくくする効果を有するといえる。 Table 2 shows L 10 , L 50 , and Weibull slope (shape parameter) e obtained by applying the peel life of each test piece to the 2-parameter Weibull distribution. Test piece 1 (Comparative Example 1) had L 10 = 38.5 hours. On the other hand, the test piece 2 (Example 1) had L 10 = 118.8 hours, which was about three times as long as the test piece 1 (Comparative Example 1). From this, it can be said that the hub bearing of the present invention has an effect of making it difficult to cause early peeling due to hydrogen embrittlement. Further, the test piece 3 (Example 1 + nitriding) is L 10 = 183.4 hours, showed about 5 times longer life to the test piece 1 (Comparative Example 1). From this, it can be said that adding nitriding treatment to the test piece 2 (Example 1) has an effect of making it difficult to cause early peeling due to hydrogen embrittlement.
試験片３（実施例１＋窒化処理）を５００℃で１時間焼戻した。図７に試験片３の転走面からの深さ方向の断面硬度分布（ビッカース硬度ＨＶ）を示す。測定は、ビッカース硬度計を用い５０μｍ間隔で行なった。図７に示すように、転走表面から０．０５ｍｍ深さと窒化されていない深さ（０．２ｍｍ以上）の箇所との硬度差ΔＨＶは６０であった。 Test piece 3 (Example 1 + nitriding treatment) was tempered at 500 ° C. for 1 hour. FIG. 7 shows the cross-sectional hardness distribution (Vickers hardness HV) in the depth direction from the rolling surface of the test piece 3. The measurement was performed at 50 μm intervals using a Vickers hardness meter. As shown in FIG. 7, the hardness difference ΔHV between the rolling surface of 0.05 mm and the non-nitrided depth (0.2 mm or more) was 60.
また、図８に同試験片における転走面からの深さ方向の断面窒素濃度分布を示す。測定にはＥｌｅｃｔｒｏｎ Ｐｒｏｂｅ Ｍｉｃｒｏ Ａｎａｌｙｚｅｒ（ＥＰＭＡ）を用いて、加速電圧１５ｋＶ、スポット径２μｍ、測定間隔２μｍ、測定時間１ｓｅｃ（秒）で測定した。試験片の転走面側から内部に向かう方向にＥＰＭＡによって鋼材中の窒素濃度分布を測定した。図８に示すように、表面窒素濃度は０．０５重量％であった。なお、表面窒素濃度における「表面」とは、表面からの深さが０〜０．０１ｍｍまでの範囲である。表層の窒素濃度が高くなるほどΔＨＶは大きくなる。 FIG. 8 shows the cross-sectional nitrogen concentration distribution in the depth direction from the rolling surface of the test piece. Measurement was performed using an Electron Probe Micro Analyzer (EPMA) at an acceleration voltage of 15 kV, a spot diameter of 2 μm, a measurement interval of 2 μm, and a measurement time of 1 sec (seconds). The nitrogen concentration distribution in the steel material was measured by EPMA in the direction from the rolling surface side to the inside of the test piece. As shown in FIG. 8, the surface nitrogen concentration was 0.05% by weight. The “surface” in the surface nitrogen concentration is a range where the depth from the surface is 0 to 0.01 mm. As the nitrogen concentration in the surface layer increases, ΔHV increases.
本発明のハブベアリングは、転がり接触部を有する構成部材が所定の鋼材からなっているので、鋼材内部に水素が集積しにくく、水素脆性を起因とする早期剥離を防止することができる。このため、ハブベアリング運転時に内部に水が混入するような過酷な使用条件下でも、長寿命を持つハブベアリングとして好適に使用できる。 In the hub bearing of the present invention, since the constituent member having the rolling contact portion is made of a predetermined steel material, it is difficult for hydrogen to accumulate inside the steel material, and early peeling due to hydrogen embrittlement can be prevented. For this reason, it can be suitably used as a long-lived hub bearing even under harsh usage conditions in which water is mixed inside during operation of the hub bearing.
１ ハブ輪
１ａ 内側転走面
１ｂ 小径段部
１ｃ 加締部
１ｄ 車輪取付けフランジ
２ 内輪
２ａ 内側転走面
３ 外方部材
３ａ 外側転走面
３ｂ 車体取付けフランジ
４ 転動体
５ 内方部材
６ ハブベアリング
７ シール部材
８ シール部材
DESCRIPTION OF SYMBOLS 1 Hub wheel 1a Inner rolling surface 1b Small diameter step part 1c Clamping part 1d Wheel mounting flange 2 Inner ring 2a Inner rolling surface 3 Outer member 3a Outer rolling surface 3b Car body mounting flange 4 Rolling element 5 Inner member 6 Hub bearing 7 Seal member 8 Seal member
Claims (4)
前記ハブベアリングの、少なくとも一つの、転がり接触部を有する構成部材は、鋼材からなっていて該鋼材の成分組成は、Ｃ：０．９５質量％以上１．１質量％以下、Ｓｉ：０．３５質量％未満、Ｍｎ：０．５質量％未満、Ｓ：０．０２５質量％未満、Ｃｒ：１．４質量％以上１．６質量％未満、残部が鉄および不純物であり、
該鋼材中に含まれる酸化物系介在物の少なくとも一部がＭｎＳで覆われており、かつ、該鋼材中の最大径が３μｍ以上の前記酸化物系介在物において、その全個数に対するＭｎＳで覆われたものの個数の割合が４０％をこえることを特徴とするハブベアリング。 A hub bearing that rotatably supports the wheels of an automobile,
The constituent member having at least one rolling contact portion of the hub bearing is made of steel, and the component composition of the steel is C: 0.95 mass% to 1.1 mass%, Si: 0.35 Less than mass%, Mn: less than 0.5 mass%, S: less than 0.025 mass%, Cr: 1.4 mass% or more and less than 1.6 mass%, the balance being iron and impurities,
At least a part of the oxide inclusions contained in the steel material is covered with MnS, and the oxide inclusions having a maximum diameter of 3 μm or more in the steel material are covered with MnS for the total number thereof. Hub bearing characterized by the ratio of the number of cracks exceeding 40%.
前記内方部材はハブ輪と内輪とを有し、
前記ハブ輪は、一端部に車輪取付フランジを一体に有して、外周に前記複列の外側転走面の一方に対向する内側転走面と、この内側転走面から軸方向に延びる小径段部とが形成されており、
前記内輪は、外周に前記複列の外側転走面の他方に対向する内側転走面が形成されていて、前記ハブ輪の小径段部に圧入されており、
前記小径段部の端部を径方向外方に塑性変形させて形成した加締部により、前記内輪は前記ハブ輪に対して固定されており、
前記内輪は、前記構成部材であることを特徴とする請求項１から請求項３のいずれか一項記載のハブベアリング。 The hub bearing has an outer member in which a double row outer rolling surface is formed on an inner periphery, and an inner member in which a double row inner rolling surface that faces the outer rolling surface of the double row is formed on an outer periphery. Comprising a member and a double row rolling element accommodated between the rolling surfaces,
The inner member has a hub ring and an inner ring,
The hub wheel has a wheel mounting flange integrally at one end, an inner rolling surface facing one of the double-row outer rolling surfaces on the outer periphery, and a small diameter extending in the axial direction from the inner rolling surface. A step is formed,
The inner ring is formed with an inner rolling surface opposite to the other of the double row outer rolling surfaces on the outer periphery, and is press-fitted into a small-diameter step portion of the hub wheel,
The inner ring is fixed to the hub ring by a crimped part formed by plastically deforming the end of the small diameter step part radially outwardly,
The hub bearing according to any one of claims 1 to 3 , wherein the inner ring is the component member.
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| JP2013197730A JP6294618B2 (en) | 2013-09-25 | 2013-09-25 | Hub bearing |
| CN201480048776.9A CN105555982A (en) | 2013-09-05 | 2014-09-05 | Rolling component |
| EP14842553.1A EP3042977B1 (en) | 2013-09-05 | 2014-09-05 | Method of testing the suitability of use of a rolling component |
| US14/917,008 US10208798B2 (en) | 2013-09-05 | 2014-09-05 | Rolling device |
| PCT/JP2014/073481 WO2015034044A1 (en) | 2013-09-05 | 2014-09-05 | Rolling component |
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| JPS54126622A (en) * | 1978-03-27 | 1979-10-02 | Daido Steel Co Ltd | Freeecutting steel for high performance gear and method of making same |
| JPH01168848A (en) * | 1987-12-23 | 1989-07-04 | Sanyo Special Steel Co Ltd | Universal free cutting steel for automobile parts and its production |
| JP3706560B2 (en) * | 2000-08-30 | 2005-10-12 | 株式会社神戸製鋼所 | Mechanical structural steel with excellent chip control and mechanical properties |
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| JP2005187888A (en) * | 2003-12-25 | 2005-07-14 | Sanyo Special Steel Co Ltd | Method for quenching hyper-eutectoid steel excellent in static strength used for rolling bearing |
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