JP2013160376A - Rolling support device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling support device having high crushing strength in which cracking and early exfoliation hardly occurs and which has a long service life even when being used under contaminated lubrication.SOLUTION: At least one rolling member among an inner ring 1, an outer ring 2, and a ball 3 constituting a deep groove ball bearing is manufactured by applying a heat treatment including carbonitriding or nitriding after working a blank made of steel into a prescribed shape. In the ball 3, a Vickers hardness HV of a surface 3a of the ball 3 measured at a measurement load of 2.94 N satisfies HV≥800, and a Rockwell hardness HRC of the surface 3a of the ball 3 measured by a C scale satisfies HRC≤66.

Description

  The present invention relates to a rolling support device such as a rolling bearing, a ball screw, and a linear guide.

Rolling bearings used in transmissions and engines of automobiles, agricultural machinery, construction machinery, steel machinery, etc. are under conditions where foreign matters such as metal chips, shavings, burrs, and abrasion powder are mixed in the lubricating oil (hereinafter referred to as “ In many cases, it is used as "under lubrication mixed with foreign matter."), And there is a case where the raceway or rolling element is prematurely peeled off by foreign matter, resulting in a significant decrease in service life.
Such early peeling under foreign matter-mixed lubrication is performed on the edge portion of the indentation (hereinafter referred to as “indentation edge”) formed on the rolling surface by foreign matter biting between the raceway and the rolling element. It is said that the cause is stress concentration.

  Therefore, in order to alleviate the stress concentration on the indentation edge even in the case where the indentation is formed on the rolling surface under the contamination with foreign matters, the applicant of the present application disclosed in Patent Document 1 at least one of the inner and outer rings. The amount of retained austenite of the surface layer portion forming the raceway surface and the surface layer portion forming the rolling surface of the rolling element is set to 20% by volume or more and 45% by volume or less, and the carbonitride of the surface layer portion forming the rolling surface of the rolling element It has been proposed that the content is 5% to 15% by volume.

Japanese Patent Laid-Open No. 64-55423

  By the way, in recent years, it has been found that the early peeling that occurs under the contamination with foreign matter is caused not only by the stress concentration on the indentation edge described above but also by the tangential force acting on the rolling surface of the race and the rolling element. ing. Factors affecting the tangential force include the surface shape and surface roughness of the rolling surface in addition to the sliding speed and surface pressure of the rolling surface. That is, in order to make it difficult for early peeling to occur under lubrication mixed with foreign matter, it is necessary to suppress stress concentration on the indentation edge formed on the rolling surface and to reduce the tangential force acting on the rolling surface.

  However, in Patent Document 1 described above, in order to suppress stress concentration on the indentation edge, the amount of retained austenite in the surface layer portion that forms the rolling surface is increased, so that the hardness of the surface layer portion is reduced and wear resistance is increased. In some cases, the indentation resistance is lowered, and the indentation due to the foreign matter is easily formed on the rolling surface. As a result, as the size and number of indentations to be formed increase, the shape of the rolling surface tends to collapse and the surface roughness increases, so the tangential force acting on the rolling surface increases.

Here, in order to reduce the tangential force, it is effective to improve the initial roughness by processing, but it is also important to suppress the deterioration of the surface roughness that occurs during the operation of the bearing. .
Further, it is known that surface origin type separation represented by indentation origin type separation is more likely to occur on the driven side having a lower peripheral speed than the driving side having a higher peripheral speed among the two contacting objects. On the other hand, the better the surface roughness of the contact partner material at the site where peeling occurs, the longer the surface-initiated peeling life can be extended. For example, in the case of a ball bearing, due to the effect of differential slip that occurs between the rolling elements and the races, the rolling elements are on the drive side and the races are on the driven side.

Therefore, in a rolling support device such as a ball bearing, the raceway is easily peeled off, and the life becomes longer as the rolling element has a better roughness.
Hardness is a material factor that affects the ease of indentation. In particular, the hardness of the surface layer greatly affects the foreign matter indentation.
On the other hand, if the rolling element of a rolling bearing cracks, the bearing locks and cannot rotate, causing a serious accident. Therefore, the rolling element of a rolling bearing is not only separated but also against cracking. It is necessary to have sufficient strength.

However, as described above, the more the hardness is improved and the more the foreign object indentation is made, the longer the peeling life is. However, when the hardness is improved to the center, cracking is likely to occur.
Therefore, the present invention has been made paying attention to the above-mentioned problems, and its purpose is to prevent cracks and early peeling even when used under foreign matter lubrication, to have a long life, and to achieve crushing. An object of the present invention is to provide a rolling support device having high strength.

In order to solve the above problems, as a result of intensive studies by the present inventors, the hardness of only the surface layer of the rolling element is improved, and the portion other than the surface layer is reduced in hardness and cracks are generated from the surface. It was found that it is effective to stop propagation with a short crack and make it difficult to break.
This invention is based on the said knowledge by the present inventors, The rolling support apparatus which concerns on Claim 1 of this invention for solving the said subject is the 1st member which has the track surface arrange | positioned mutually, and A second member, and a rolling element that is arranged between the first member and the second member so as to be freely rollable and has a rolling surface with respect to the raceway surface, and the rolling element rolls, In the rolling support device in which one of the first member and the second member moves relative to the other,
The rolling element and at least one rolling member of the first member and the second member are obtained by processing a material made of steel into a predetermined shape and then performing heat treatment including carbonitriding or nitriding. ,
In the rolling element, the Vickers hardness HV of the surface of the rolling element measured at a measurement load of 2.94N satisfies HV ≧ 800, and the Rockwell hardness HRC of the surface of the rolling element measured on the C scale is HRC. It is characterized by satisfying ≦ 66.

Here, the steel has a C content of 0.8 mass% to 1.2 mass%, an Si content of 0.3 mass% to 2.0 mass%, and an Mn content of 0.3 mass%. Preferably, the Cr content is 0.5% by mass or more and 1.6% by mass or less, and the balance is made of Fe and inevitable impurities.
In addition, the rolling support apparatus of this invention points out a rolling bearing, a ball screw, and a linear guide, for example. Here, when the rolling support device is a rolling bearing, the first member and the second member indicate an inner ring and an outer ring. Similarly, when the rolling support device is a ball screw, the first member and the second member indicate a screw shaft and a nut, and when the rolling support device is a linear guide, the first member and the second member are guide rails. And a slider. The rolling element refers to a ball.

Here, even if a crack occurs on the surface of the rolling element, in order to stop the propagation with a short crack and make it difficult to break, in order to improve the hardness of only the very surface layer of the rolling element, grinding or barreling is performed by continuous quenching. Although it is possible to control the peening conditions, it is preferable that a highly hard nitride is deposited only on the surface layer part by optimizing the carbonitriding conditions.
Usually, the greater the Vickers hardness of the material, the greater the Rockwell hardness.

However, the picker hardness of light load has a small indentation and a small measurement range, whereas the Rockwell C scale has a large indentation and a large measurement range.
Therefore, when there is a steep hardness gradient from the surface to the inside, a correlation cannot always be obtained between the Vickers hardness and the Rockwell hardness.
In the present invention, a rolling element having a surface hardness of HV ≧ 800 and HRC ≦ 66 is realized by providing a steep hardness gradient. In addition, the value of the said hardness is a value which converted the measured value (spherical hardness) into plane hardness according to JIS-B1501.

Thus, by setting the rolling element surface hardness to HV ≧ 800 and HRC ≦ 66 (preferably HV ≧ 830, HRC ≦ 65), it is possible to suppress deterioration of rolling element surface properties and improve crack strength due to formation of foreign matter indentations. It becomes possible to achieve both, and the tangential force acting between the rolling member and the mating member in rolling contact can be reduced.
Therefore, even when the rolling support device of the present invention is used under foreign matter-mixed lubrication, cracks and early peeling are unlikely to occur, and the life is extended.

In the rolling support device of the present invention, the nitrogen content of the rolling surface of the rolling element is 0.2 to 1.5% by mass, and the rolling surface of the rolling element is nitrided containing Si and Mn. The area ratio of the product (hereinafter referred to as Si-Mn nitride) is preferably 1% or more and less than 10%.
In the rolling support device of the present invention, carbonitriding is performed in order to enrich the surface layer of the raceway or rolling element with predetermined nitrogen.

Nitrogen, like carbon, not only acts to strengthen the solid solution strengthening of martensite and ensure the stability of retained austenite, but also has the effect of forming a nitride or carbonitride to improve the pressure resistance and wear resistance.
The higher the surface nitrogen content is, the better the wear resistance and pressure scar resistance are. When the surface nitrogen content exceeds 0.2%, the effect is remarkable, but more preferably 0.35% or more.

On the other hand, if the nitrogen content is too high, there is a drawback that toughness and static strength are lowered. Since the toughness and static strength are necessary performances for rolling elements of a rolling bearing, it is not preferable that the nitrogen content is too high.
Therefore, the upper limit of the nitrogen content on the surface of the rolling element constituting the rolling support device of the present invention is 1.5%, more preferably 1.0%.

As described above, it has been clarified that the higher the nitrogen content on the surface, the better the pressure-proof scar resistance and wear resistance of the material.
However, the present inventors have further found that even when the nitrogen content is the same, the pressure scar resistance and wear resistance change depending on the presence of nitrogen inside the material.
Nitrogen may be present as a solid solution in the material or may be precipitated as a nitride.

Although detailed numerical values will be described later, when carbonitriding a material containing a large amount of Si-Mn, even if the nitrogen content is the same, the amount of nitrogen present as a solid solution in the material is less than the Si-Mn-based surface. The amount of nitrogen present by precipitation of nitride increases.
The higher the area ratio of the Si—Mn nitride, the more excellent the wear resistance and the scratch resistance, and when the area ratio of the Si—Mn nitride exceeds 1%, a remarkable effect appears. % Or more.

Moreover, when the precipitation amount of Si-Mn nitride is too large as in the case of the nitrogen content, there is a drawback that toughness and static strength are lowered.
Since toughness and static strength are necessary performances for rolling elements of a rolling bearing, it is not preferable that the amount of Si-Mn nitride precipitates is excessive.
Therefore, the upper limit of the area ratio of the Si—Mn nitride of the present invention is set to 10%, more preferably 8%.

In order to achieve the above, a normal carbonitriding process is insufficient, and a special carbonitriding process with an increased ammonia flow rate is required.
In the rolling support device of the present invention, the nitrogen content at a position 200 μm deep from the surface of the rolling surface of the rolling element is 0.3 mass% or less, and the surface of the rolling surface of the rolling element is It is preferable that the area ratio of the Si—Mn nitride at a depth of 200 μm to 200 μm is 3% or less.

As described above, on the surface of the rolling element, the higher the nitrogen content and the larger the area ratio of the nitride, the less likely the surface of the rolling element is indented or scratched.
However, the higher the nitrogen content and the larger the area ratio of nitride, the easier it is to crack.
Therefore, by increasing the nitrogen content only in the extreme surface layer, steepening the nitrogen content gradient from the surface to the core, and lowering the nitrogen content in the core, the pressure resistance and scratch resistance are improved and the crack strength is increased. It is possible to achieve both improvements.

As for the specific value of the nitrogen content, the nitrogen content at a position of 200 μm from the rolling surface of the rolling element is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less.
Further, the area ratio of the Si—Mn nitride is preferably 3% or less, and more preferably 2% or less. By doing in this way, it is possible to improve crack resistance.

In order to make the gradient of the nitrogen content ratio and nitride area ratio from the rolling contact surface abrupt, it is important to perform nitriding for a short time in a high nitrogen atmosphere with an increased ammonia flow rate.
<About rolling elements>
Hereinafter, the rolling element which comprises the rolling support apparatus which concerns on this invention is demonstrated in detail.
Among the rolling members used in the present invention, after the heat treatment, the rolling elements were measured on the surface of the rolling elements with a Vickers hardness HV measured at a measurement load of 2.94 N of HV ≧ 800 and C scale. It is obtained by processing a material made of steel into a predetermined shape so that the Rockwell hardness HRC is HRC ≦ 66, and then performing a heat treatment including carbonitriding or nitriding. By defining the hardness of the surface of the rolling element in this way, it is possible to achieve both an increase in bearing life and an improvement in the cracking resistance of the rolling element by improving the pressure scar resistance and scratch resistance of the rolling element.

  Furthermore, the nitrogen content of the rolling surface of the rolling element is 0.2 to 1.5% by mass, the area ratio of the Si—Mn nitride is 1% or more and less than 10%, and is located 200 μm from the rolling element rolling surface. When the nitrogen content is 0.3% by mass or less and the area ratio of the Si—Mn nitride is 3% or less, the above functions can be further improved.

<About the steel used as the material>
Each component of the steel constituting the rolling element constituting the rolling support device according to the present invention will be described in detail below.
[About C (carbon)]
Carbon is an important element for obtaining the strength and life required for steel. If the amount of carbon is too small, not only the sufficient strength cannot be obtained, but also the heat treatment time required to obtain the hardened layer depth required for carbonitriding described later is increased, leading to an increase in heat treatment cost.
Therefore, the steel constituting the rolling element constituting the rolling support device according to the present invention has a C content of 0.8% by mass to 1.2% by mass and a Cr content of 0.9% by mass to 1%. It is preferable to set it to 2 mass% or less.

Here, if the C content of the steel constituting the material is too small, not only can the necessary strength be imparted to the rolling member, but also to obtain the necessary hardened layer depth on the rolling surface when performing nitriding or carbonitriding. This increases the heat treatment time and increases the heat treatment cost. Therefore, the C content of the steel constituting the material is preferably 0.8% by mass or more, and more preferably 0.9% by mass or more.
On the other hand, if the C content of the steel material is too large, huge carbides are generated during steelmaking, which not only adversely affects the subsequent quenching characteristics and rolling fatigue life, but also reduces the header workability and reduces the cost. Invite rise. Therefore, the C content is preferably 1.2% by mass or less.

[Si (silicon) and Mn (manganese)]
As described above, in order to sufficiently precipitate the Si—Mn nitride, it is necessary to use a steel material containing a large amount of Si and Mn. In SUJ2 (Si content 0.25%, Mn content 0.4%) which is a general bearing material, even if nitrogen is excessively added by carbonitriding or the like, the amount of Si—Mn nitride is small.

  For this reason, as content of Si and Mn in the steel which makes the raw material of a rolling element, Si content rate is 0.3 mass% or more and 2.0 mass% or less, and Mn content rate is 0.3 mass% or more. It is preferable that it is 0 mass% or less. In order to efficiently precipitate Si—Mn nitride on the rolling surface and to dissolve N (nitrogen) within the scope of the present invention in the surface layer portion forming the rolling surface, the Si content and the Mn content It is preferable to make the total of 1 mass% or more.

  Here, the Si content and the Mn content are each 0.3% by mass or more in order to precipitate Si—Mn nitride efficiently. On the other hand, if the Si content is too high, not only the workability and machinability are lowered, but also the carbonitriding characteristics and nitriding characteristics are lowered, and the N content of the surface layer portion forming the rolling surface is within the scope of the present invention. It becomes impossible to. Moreover, when there is too much Mn content, the amount of retained austenite of the surface layer part which makes a rolling surface after heat processing will increase, and hardness, abrasion resistance, and pressure dent will deteriorate. Therefore, it is preferable that both Si content rate and Mn content rate shall be 2.0 mass% or less.

[Cr (chromium)]
Cr present in the steel constituting the rolling element has the effect of improving the hardenability and temper softening resistance by forming a solid solution in the base, and forming fine carbides and carbonitrides with high hardness. In order to suppress the hardness of the rolling member and the coarsening of crystal grains during heat treatment, it has the effect of improving the rolling fatigue life. In order to obtain these effects, the Cr content of the material steel is preferably 0.5% by mass or more, and more preferably 1.3% by mass or more.

Here, when the Cr content of the steel forming the rolling element is too large, huge carbides are generated during steelmaking, which adversely affects the subsequent quenching characteristics and rolling fatigue life, and header workability and machinability. May decrease. Therefore, the Cr content of the steel constituting the material is preferably 2.0% by mass or less, and more preferably 1.6% by mass or less.
In addition to the elements described above, carbide forming promoting elements such as Mo and V, which have the same action as Cr, are included in the steel that forms the material in a range that does not cause an increase in cost due to an increase in material cost or a decrease in workability. (For example, each may be selectively contained at about 0 to 2%).

  The balance of the steel constituting the material is substantially made of Fe, but may contain S, P, Al, Ti, O, etc. as inevitable impurities. These elements are said to have no particularly remarkable inhibitory effect on surface-initiated peeling starting from the indentation edge. Origin-type peeling occurs. For this reason, strict impurity regulation that causes a significant increase in cost is not performed, but the content of inevitable impurities is set to a quality level that satisfies the cleanliness regulation of high carbon chromium bearing steel defined in JIS G 4805.

<About heat treatment>
First, after the above-described steel material is processed into a predetermined shape by forming or rough grinding, the steel is heated and held in a furnace introduced with RX gas, or mixed gas (for example, “Carbonitriding” is performed by heating and holding in a furnace in which (RX gas + enrich gas + ammonia gas) is introduced. In particular, this “carbonitriding” is “special carbonitriding” in which nitriding is performed in a short time in a high nitrogen atmosphere with an increased ammonia flow rate. In these treatments, after heat treatment, the abundance of Si-Mn nitride on the rolling surface of the rolling element is 1% or more and 10% or less, and the nitrogen content of the surface layer portion forming the rolling surface is 0.2 mass. % To 1.5% by mass or less is preferable.

  Next, quenching and tempering are performed. These treatments are preferably performed under such conditions that the surface layer portion that forms the rolling surface after the heat treatment has a hardness necessary for a rolling member (for example, Hv 750 or more). In particular, the surface of the rolling element after this heat treatment is such that the Vickers hardness HV measured at a measurement load of 2.94 N is HV ≧ 800 and the Rockwell hardness HRC measured on the C scale is HRC ≦ 66. Perform under conditions.

  As described above, according to the rolling support device according to the present invention, even when used under foreign matter lubrication, it is difficult to cause cracking or early peeling, has a long life, and has a high crushing strength. Can be provided.

It is sectional drawing which shows a deep groove ball bearing as an example of the rolling support apparatus which concerns on this invention.

  Hereinafter, the results of verifying the effects of the present invention based on examples will be described.

  In this example, a deep groove ball bearing (inner diameter: 30 mm, outer diameter: 62 mm, width: 16 mm) having a designation number of 6206 manufactured by NSK Ltd. was produced by the following procedure. As shown in FIG. 1, this deep groove ball bearing includes a race ring (inner ring 1, outer ring 2), rolling elements (ball 3), and cage 4. In this deep groove ball bearing (rolling support device), an inner ring (first member) 1 and an outer ring (second member) 2 have raceway surfaces 1a and 2a arranged to face each other. The ball 3 is disposed between the inner ring 1 and the outer ring 2 so as to freely roll, and has a rolling surface 3a for the raceway surfaces 1a and 2a. Then, as the ball 3 rolls, one of the inner ring 1 and the outer ring 2 moves relative to the other.

<Production of race ring>
The inner ring 1 and the outer ring 2 were produced by processing a material made of two types of high carbon chrome bearing steel (SUJ2) into a predetermined shape, and then performing heat treatment and mirror finishing. Here, as the heat treatment in the production of the bearing ring, after quenching (after heating and holding at 840 to 880 ° C. for 1 hour in the furnace introduced with RX gas and oil quenching), tempering (160 to 220 ° C.) , 2 hours).
In addition, the material which consists of SUJ2 is C content rate 0.99 mass%, Si content rate is 0.25 mass%, Mn content rate is 0.40 mass%, Cr content rate is 1.49 mass%. Of steel.

<Production of rolling elements>
On the other hand, after rolling the raw material which consists of steel into the predetermined shape by header processing and rough grinding, multiple types of rolling elements were produced by performing heat processing and mirror surface finishing. Here, SUJ2 wire and SUJ3 (3 types of high carbon chromium bearing steel) are used as the above materials, and “Special carbonitriding and quenching” and “Subsequent quenching” are used as heat treatment in the production of rolling elements. did. The material consisting of SUJ2 has a C content of 1.0 mass%, an Si content of 0.55 mass%, an Mn content of 1.1 mass%, and a Cr content of 1.15 mass%. Of steel.

“Special carbonitriding and quenching” is a special carbonitriding process by heating and holding at 830 ° C. for 1 to 20 hours in a furnace where mixed gas (RX gas + enriched gas + ammonia gas atmosphere) is introduced after processing the above materials. , A heat treatment method for tempering at 180 to 270 ° C.
On the other hand, the above-mentioned “subsequent quenching” is performed by tempering (160 ° C. to 220 ° C.) after processing the above-mentioned raw material, after heating and holding at 840 to 880 ° C. for 1 hour in an oven introduced with RX gas, and then oil quenching. , 2 hours).

Here, the rolling elements using the SUJ3 material were adjusted in hardness (Vickers hardness Hv, Rockwell hardness HRC) by changing the hardness according to heat treatment conditions (time, ammonia flow rate). Moreover, the rolling element using SUJ2 material adjusted hardness (Vickers hardness Hv, Rockwell hardness HRC) by changing ball peening conditions (time, rotation speed). All of the obtained rolling elements had a Vickers hardness Hv of 800 or more and a Rockwell hardness HRC of 66 or less. In addition, the said hardness was measured using the Vickers hardness test method prescribed | regulated to JISZ2244 with respect to the surface layer part of each rolling element.
For each of the above conditions of “material”, “heat treatment method”, “Vickers hardness”, and “Rockwell hardness”, test specimens were prepared in combinations shown in Table 1.

[Measurement of nitrogen content]
For each test specimen, the nitrogen content in the surface layer part (the part from the surface to a depth of 50 μm) and the inside (the part from the surface to a depth of 200 μm) was measured using an electron beam microanalyzer (EPMA). And measured at an acceleration voltage of 15 kV. The results are shown in Table 1.
[Measurement of area ratio of Si-Mn nitride]
The area ratio of the Si-Mn nitride is measured by using a field emission scanning electron microscope (FE-SEM) to observe the surface of the rolling surface at an acceleration voltage of 10 KV, and at a magnification of 5,000 times. I took photos over 3 fields of view. Thereafter, the presence rate (area ratio) was measured after binarizing the obtained photograph using an image analysis apparatus. The results are shown in Table 1.
The values of HV hardness, HRC hardness, nitrogen content, and nitride area ratio of the rolling elements shown in Table 1 were measured 10 times for the same lot product, and the average value was shown.

(Evaluation)
Using the obtained rolling elements (ball 3), SUJ2 inner ring 1 and outer ring 2, and plastic cage 4, a deep groove ball bearing (inner diameter: 30 mm, outer diameter) manufactured by NSK Ltd. (Diameter: 62 mm, width 16 mm, dynamic load rating: 19.5 kN, static load rating: 11.3 kN) went. The results are shown in Table 1.

<About life test>
The life test is performed 12 times for each specimen (Examples 1 to 13 and Comparative Examples 1 to 4), the life time until peeling occurs is investigated, a Weibull plot is created, and the results of the Weibull distribution are used. , L ₁₀ life was obtained and used as the life value. In Table 1, the foreign matter mixing lifetime is shown as a ratio value with the value of Comparative Example 1 having the shortest lifetime as 1.
[Conditions for life test]
Test load: Fr = 6.5 kN
Rotational speed: 3,000 min ^-1
Lubricating oil: ISO-VG68
Hardness of foreign matter: HV519
Foreign material size: 74-147 μm
Foreign matter contamination: 0.05g

<About crushing test>
In addition, a crushing test was carried out on a nominal 3/8 inch steel ball used in the life test and a steel ball of the same lot.
The crushing test was performed by a method in which two balls having two conical seats with an angle of 120 degrees were stacked and pressed at 2.0 kN / s.
One of the two balls was provided with a defect of φ0.2 mm × depth 0.2 mm by a high hardness drill, and the load when the ball provided with the defect was broken was determined.
The crushing test was performed five times for each specimen, and Table 1 shows the average value of the crushing load. In addition, the crushing value in Table 1 shows the value of Comparative Example 4 as 1.

  From the results in Table 1, Examples 1 to 3 using the balls 3 having a surface Vickers hardness of 800 or more measured with a measurement load of 2.94 N and a Rockwell hardness of 66 or less measured on the C scale. It can be seen that No. 13 has both a long life and high crushing strength as compared with Comparative Examples 1 to 4.

Further, among Examples 1 to 13, it can be seen that in Examples 3 to 6 and 8 to 13 in which the Vickers hardness of the surface 3a of the ball 3 exceeds 830, the effect of extending the life appears more remarkably. Moreover, in Examples 1-3, 7-11 whose hardness of the surface 3a of the ball | bowl 3 is 65 or less, it turns out that crushing strength further improves.
In addition, even with the same Vickers hardness, Examples 7 to 13 subjected to carbonitriding clearly show a remarkable effect of extending the life and improving the crushing strength as compared with Examples 1 to 6 subjected to soaking. Yes.

  Among Examples 7 to 13 subjected to heat treatment by special carbonitriding, Examples 7 to 12 having a nitrogen content of 0.3% by mass or less and a nitride area ratio of 3% or less are more effective. It can be seen that the crushing strength is improved. In particular, it can be seen that in Examples 8 to 12 in which the nitrogen content is 0.2% by mass or more and the area ratio of the Si—Mn nitride is 1% or more, the effect of extending the life is further remarkable.

Therefore, according to the rolling support device according to the present invention, even when used under foreign matter lubrication, it is difficult to cause cracking or early peeling, has a long life, and provides a rolling support device with high crushing strength. Can do.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably. For example, in the above embodiment, the evaluation result of the ball bearing is shown, but equivalent performance can be obtained with other ball bearings and various roller bearings. Moreover, in the said Example, although the case where SUJ3 material was used for the raw material of a rolling element was shown, C: 0.8-1.2 mass%, Si: 0.3-2.0 mass%, Mn: 0 The same performance can be obtained as long as the component satisfies 3 to 2.0 mass% and Cr: 0.5 to 1.6 mass%.

1 Inner ring (first member)
2 Outer ring (second member)
3 balls (rolling elements)
3a Rolling surface 4 Cage

Claims (5)

A first member and a second member having raceway surfaces arranged to face each other; a rolling element which is disposed between the first member and the second member so as to freely roll and has a rolling surface with respect to the raceway surface; In the rolling support device in which one of the first member and the second member moves relative to the other by rolling the rolling element,
The rolling element and at least one rolling member of the first member and the second member are obtained by processing a material made of steel into a predetermined shape and then performing heat treatment including carbonitriding or nitriding. ,
In the rolling element, the Vickers hardness HV of the surface of the rolling element measured at a measurement load of 2.94 N satisfies HV ≧ 800, and the Rockwell hardness HRC of the surface of the rolling element measured on the C scale is HRC. A rolling support device satisfying ≦ 66.   2. The rolling support device according to claim 1, wherein the Vickers hardness HV satisfies HV ≧ 830 or the Rockwell hardness HRC satisfies HRC ≦ 65. 3.   The nitrogen content of the rolling surface of the rolling element is 0.2 to 1.5 mass%, and the area ratio of the nitride containing Si and Mn on the rolling surface of the rolling element is 1% or more and 10%. The rolling support device according to claim 1 or 2, wherein the rolling support device is less than the number.   The nitrogen content at a position 200 μm deep from the surface of the rolling surface of the rolling element is 0.3 mass% or less, and Si at a position 200 μm deep from the surface of the rolling surface of the rolling element The rolling support device according to claim 3, wherein the area ratio of the nitride containing Mn is 3% or less.   The steel has a C content of 0.8% by mass or more and 1.2% by mass or less, an Si content of 0.3% by mass or more and 2.0% by mass or less, and an Mn content of 0.3% by mass or more. The content of Cr is 0.5% by mass or more and 1.6% by mass or less at 2.0% by mass or less, and the balance is made of Fe and inevitable impurities. Rolling support device.

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