KR20080039284A - Bearing steel component and method for production thereof, and bearing - Google Patents

Abstract

A bearing steel component and a method for producing the same, and a bearing are provided to effectively improve fatigue characteristics of hardened tissues formed on a transmission surface. A bearing steel component includes a bearing outer wheel(3), a bearing inner wheel(1), and a bearing steel ball(4). A shaft part is inserted into the bearing inner wheel. The bearing steel ball is interposed between the inner wheel and the outer wheel to constitute a bearing. A steel material is continuously cast to form cast pieces having a size of 300x400mm. The cast piece is broke down to be rolled as a billet having a size of 150mm and rolled as a rod steel of 24mmPhi.

Description

BEARING STEEL COMPONENT AND METHOD FOR PRODUCTION THEREOF, AND BEARING

The present invention relates to a bearing steel part, a method for manufacturing the same, and a bearing using the bearing steel part, which is provided with a hardened layer by hardening on the transmission surface.

Bearings are used in rotating parts such as automobiles and machinery, and excellent electric fatigue characteristics are required. As a method of improving the rolling fatigue characteristic, for example, as described in Patent Document 1, there is a method for defining a heating method for bearing steel, and by miniaturizing the old austenite particle diameter to 4.0 µm or less on average , The motor fatigue life is more than doubled. Although the technique described in this patent document 1 aims to improve the fatigue strength to some extent by miniaturizing the average particle diameter of the old austenite particle diameter of the bearing steel, even if the average old austenite particle diameter is fine, The spherical spherical γ particles may remain, and when this is present on the transmission surface, the effect of improving the desired rolling fatigue strength may not be obtained, and there is room for improvement.

Patent Document 1: Japanese Unexamined Patent Publication No. 2006-152407

The present invention was developed in view of the above-mentioned phenomenon, and an object of the present invention is to propose a bearing steel component having a further improved electric fatigue strength, and a bearing using these together with its advantageous manufacturing method. Here, the bearing steel component used in the present invention refers to a component constituting a bearing such as a bearing inner and outer ring, a bearing ball, a bearing roller, a needle, and the like, and that steel is used as a material.

By the way, the inventors earnestly examined about the hardening structure formed in the transmission surface especially in order to improve the fatigue characteristic as mentioned above effectively.

As a result, attention was paid to the particle diameter distribution of the old austenite particles in the quenched structure, and it was found that the rolling fatigue strength was improved by miniaturizing the average particle diameter and the maximum particle diameter of the old austenite particles. That is, the summary structure of this invention is as follows.

(Iii) Bearing steel parts quenched on the transmission surface, wherein the quenched structure is characterized in that the bearing steel is characterized in that the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter is 4 times or less the average particle diameter. part.

(Ii) C: 0.3-1.5 mass%,

Si: 3.0 mass% or less and

Mn: 2.0 mass% or less, and satisfy | filling following formula (1), and remainder has the component composition which is Fe and an unavoidable impurity, The bearing steel component as described in said (iii) characterized by the above-mentioned.

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn)> 2.0 ... (One)

(Iii) as said component composition,

Al: 0.25 mass% or less, The bearing steel component as described in said (ii) characterized by the above-mentioned.

(Iii) as said component composition,

Cr: 2.5 mass% or less,

Mo: 1.0 mass% or less,

Cu: 1.0 mass% or less,

Ni: 2.5 mass% or less,

Co: 1.0 mass% or less,

V: 0.5 mass% or less and

W: The bearing as described in said (ii) or (iii) containing 1 type (s) or 2 or more types chosen from 1.0 mass% or less, and satisfy | filling following formula (2) instead of said formula (1). Steel parts.

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 0.5W )> 2.0. (2)

(Iii) as said component composition,

Ti: 0.1 mass% or less,

Nb: 0.1 mass% or less,

Zr: 0.1 mass% or less,

B: 0.01 mass% or less,

Ta: 0.5 mass% or less,

Hf: 0.5 mass% or less and

Sb: 1 type (s) or 2 or more types selected from 0.015 mass% or less, and satisfy | filling following formula (3) instead of said formula (1) or (2), Said (ii), (b) ) Or a bearing steel component according to (iii).

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 1000B) (1 + 0.5W)> 2.0... (3)

(Iii) as said component composition,

S: 0.1 mass% or less,

Pb: 0.1 mass% or less,

Bi: 0.1 mass% or less,

Se: 0.1 mass% or less,

Te: 0.1 mass% or less,

Ca: 0.01 mass% or less,

Mg: 0.01 mass% or less and

REM: The bearing steel part in any one of said (ii)-(iii) containing 1 type (s) or 2 or more types chosen from 0.1 mass% or less.

(Iii) The bearing steel part according to the above (iv) to (v), wherein the bearing steel part is a ball or roller for bearing.

(Iii) The bearing steel part according to the above (i) to (iii), wherein the bearing steel part is a bearing inner ring or a bearing outer ring.

(Iii) A steel material containing at least 10% by volume in total of any one or both of the fine bainite structure and the fine martensite structure, and at least a portion of the material having a temperature raising rate of 400 ° C / s or more and reaching a temperature of 1000; A method for producing a bearing steel part, characterized by performing at least one high-frequency heating at or below 캜.

(Iii) In the above (iv), the raw material is subjected to a hot working step in which the total working rate at 800 to 1000 ° C. is 80% or more, and a temperature zone of 700 to 500 ° C. after this hot working step is 0.2 ° C. / 20% or more in the cooling process to cool at a cooling rate of s or more, and in the temperature zone below 700-800 degreeC before this cooling process, or 20% or more in the temperature range below the A ₁ point transformation point after this cooling process. It manufactures through the 2nd processing process which performs a process, The manufacturing method of the bearing steel component characterized by the above-mentioned.

(Iii) The method of manufacturing a bearing steel part according to (v) or (v), wherein a residence time of 800 ° C. or higher in one high frequency heating is 5 seconds or less.

(Iii) the steel material,

C: 0.3-1.5 mass%,

Si: 3.0 mass% or less and

Mn: 2.0 mass% or less, and satisfy | filling following formula (1), and remainder is a composition which consists of Fe and an unavoidable impurity, The bearing steel parts in any one of said (i)-(iii) characterized by the above-mentioned. Method of preparation.

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn)> 2.0 ... (One)

(Iii) the steel further

Al: 0.25 mass% or less, The manufacturing method of the bearing steel component of the said (xii) characterized by the above-mentioned.

(Iii) the steel further

Cr: 2.5 mass% or less,

Mo: 1.0 mass% or less,

Cu: 1.0 mass% or less,

Ni: 2.5 mass% or less,

Co: 1.0 mass% or less,

V: 0.5 mass% or less and

W: It is a composition containing 1 type (s) or 2 or more types chosen from 1.0 mass% or less, and satisfy | filling following formula (2) instead of said Formula (1), To said (iii) or (iii) characterized by the above-mentioned. The manufacturing method of the described bearing steel parts.

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 0.5W )> 2.0. (2)

(Iii) as said component composition,

Ti: 0.1 mass% or less,

Nb: 0.1 mass% or less,

Zr: 0.1 mass% or less,

B: 0.01 mass% or less,

Ta: 0.5 mass% or less,

Hf: 0.5 mass% or less and

Sb: 1 or 2 or more types selected from 0.015 mass% or less, and satisfying the following formula (3) instead of the formula (1) or (2): (iii) to (iii) The manufacturing method of the bearing steel component in any one of)).

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 1000B) (1 + 0.5W)> 2.0... (3)

(Iii) as said component composition,

S: 0.1 mass% or less,

Pb: 0.1 mass% or less,

Bi: 0.1 mass% or less,

Se: 0.1 mass% or less,

Te: 0.1 mass% or less,

Ca: 0.01 mass% or less,

Mg: 0.01 mass% or less and

REM: The manufacturing method of the bearing steel component as described in any one of said (iii)-(iii) containing 1 type or 2 or more types chosen from 0.1 mass% or less.

(Iii) The bearing steel component is a manufacturing method of the bearing steel component according to the above (i) to (iii), wherein the bearing steel parts are rollers or rollers for bearings.

(Iv) The bearing steel part is a bearing inner ring or a bearing outer ring, wherein the bearing steel part is produced according to (i) to (i).

(Iii) A bearing in which the bearing steel parts described in the above (iv) are used as a ball or roller of a bearing.

(Iii) A bearing in which the bearing steel parts described in the above (iv) are used as the inner ring or the outer ring of the bearing.

According to the present invention, it is possible to stably obtain a bearing steel component or a bearing having excellent rolling fatigue characteristics.

Hereinafter, the present invention will be described in detail. The bearing steel part of the present invention is formed of a steel material, preferably a bar steel or steel wire, in the shape of the parts constituting the bearings such as bearing inner and outer rings, bearing balls, bearing rollers and needles through a molding process (forging, cutting, etc.). After processing, it is manufactured by quenching the entire circumferential surface or the whole part.

As the steel parts, there are various shapes and structures for each part such as the above-described bearing inner and outer rings, bearing balls (steel balls), bearing rollers, and needles, all of which are hardened by quenching in the transmission surface or the whole, especially where electric fatigue strength is required. It is important that the hardened layer of the cured layer has a layer, wherein the average particle diameter of the old austenite particles is 12 µm or less, and the maximum particle diameter is 4 times or less the average particle diameter.

In the following, the results of the studies leading to this finding will be described. After the steel material of the composition shown by the following a steel or b steel is melted in a 150 kg vacuum melting furnace, hot forged to 150 mm length and width, a dummy billet is produced, and hot worked and cold drawn under various conditions. It cut and set it as the rod steel of 12 mm (phi).

[a steel] C: 0.48% by mass, Si: 0.55% by mass, Mn: 0.78% by mass, P: 0.011% by mass, S: 0.019% by mass, Al: 0.024% by mass, N: 0.0043% by mass, and the balance is Fe and Inevitable impurities.

[b steel] C: 0.48 mass%, Si: 0.51 mass%, Mn: 0.79 mass%, P: 0.011 mass%, S: 0.021 mass%, Al: 0.024 mass%, N: 0.0039 mass%, Mo: 0.45 mass %, Ti: 0.021 mass%, B: 0.0024 mass%, balance Fe and an unavoidable impurity.

The surface of this bar steel was quenched in various conditions under various conditions, cut into a predetermined length to obtain a rolling fatigue test piece, and a radial rolling fatigue test shown in FIG. 1 was performed. Moreover, about the test piece obtained similarly, the structure of the hardened layer was observed using the optical microscope, and the old austenite average particle diameter and the largest old austenite particle diameter were calculated | required.

The measurement of the former austenite average particle diameter was 400 times (1 area of view: 0.25 mm x 0.225 mm) to 1000 times (1 area of view: 0.10 mm x 0.09 mm) by an optical microscope, and the cured layer thickness from the surface. Observation of 5 fields of vision was carried out for each of the positions of 1/5, 1/2 and 4/5 of, and the average sphere austenite particle diameter at each position was measured, and the maximum average sphere austenite was measured. It was set as the particle diameter. In addition, the hardened layer thickness was made into the depth area | region from the surface until the area ratio of martensite structure reduces to 98%.

On the other hand, the maximum sphere austenite particle diameter is 400 times (area of 1 field of view: 0.25 mm x 0.225 mm) and is measured for an area corresponding to 5 fields of view and a total of 15 fields of view at the respective positions in the cured layer thickness direction, and a total field of view The value calculated | required by the following formula from the particle size distribution in inside was made into the largest particle diameter.

Maximum particle diameter = average particle diameter + 3σ (σ: standard deviation)

In addition, the measurement of old austenite particle | grains: sodium dodecyl benzene sulfonate: 11 g, ferrous chloride: 1 g in the picric acid aqueous solution which dissolved 50 g of picric acid with respect to 500 g of water with respect to the cross section cut | disconnected in the thickness direction of the hardened layer. And oxalic acid: 1.5 g of oxalic acid was added to act as a caustic solution to give a former austenite grain boundary.

2A and 2B show the results of this test. In the case where the average sphere austenite particle diameter is 12 µm or less, it can be seen that the fatigue strength can be significantly improved by setting the maximum sphere austenite particle diameter / average sphere austenite particle diameter to 4 or less. Moreover, it turns out that when the average austenite particle diameter is 5 micrometers or less and even 3 micrometers or less, the fatigue strength improvement effect by the maximum sphere austenite particle diameter / average sphere austenite particle diameter being 4 or less becomes more remarkable. .

Table 1 also shows the results used to obtain FIGS. 2A and 2B. Moreover, the rolling fatigue characteristic showed the time until breakage as a ratio with respect to the same time of the test No. 1 in Table 1 corresponded to a conventional product.

Here, in order to make the average particle diameter of the old austenite particles 12 m or less and the maximum particle size 4 times or less, the structure before high frequency quenching contains uniform fine bainite structure and / or martensite structure. The method of making it is advantageous and suitable. This method is described below.

That is, with respect to the whole structure of the high frequency quenching, the tissue fraction of the bainite structure and / or the martensite structure is made 10 vol% or more, preferably 25 vol% or more. If there are many bainite or martensite structures in the entire quenching tissue, the bainite or martensite tissues are finely dispersed carbides, and thus the ferrite / carbide interface of the austenite nucleation site during quenching heating Since the area is increased and the resulting austenite is refined, it effectively contributes to miniaturizing the former austenite particle diameter of the hardened hardened layer. When the austenitic particle diameter becomes finer during quenching heating, the grain boundary strength is increased and the fatigue strength is improved.

In order to make the structure fraction of uniform fine bainite structure and / or martensite structure into 10 volume% or more, the steel of the component composition mentioned later is hot-worked so that the total processing rate at 800-1000 degreeC may be 80% or more, What is necessary is just to cool the temperature range of 700-500 degreeC after a hot working by the cooling rate of 0.2 degreeC / s or more. This is because a sufficiently uniform fine bainite structure or martensite structure cannot be obtained if the total processing rate at 800 to 1000 ° C. is less than 80%. In addition, the bainite structure and / or martensite structure cannot be 10% by volume or more in total unless the temperature zone of 700 to 500 ° C is cooled at a cooling rate of 0.2 ° C / s or more after hot working.

In addition, in order to refine the average particle diameter and the maximum particle diameter of the old austenite to the cured layer after the high frequency quenching, it is necessary to perform 20% or more processing in a temperature zone of less than 800 ° C. before the high frequency quenching (second processing step) There is. Machining in the temperature zone below 800 ° C. is a hot working step, and may be carried out before cooling of the cooling rate (temperature zone below 700 ° C. to 800 ° C.), or cold work separately after cooling, or at temperatures below the A ₁ transformation point. It may be reheated at and warm processed. As for the processing rate below 800 degreeC, it is more preferable to set it as 30% or more.

Moreover, as a processing method, cold forging, cold ironing, rolling process, shot etc. are mentioned, for example.

Next, the preferable steel component for obtaining this whole structure is demonstrated.

C: 0.3-1.5 mass%

C is the element having the greatest influence on hardenability, and contributes to the improvement of the fatigue strength by increasing the hardness and depth of the hardened layer. However, if the content is less than 0.3% by mass, the depth of the hardened hardened layer must be drastically increased to secure the required fatigue strength, at which time the occurrence of quenching cracks becomes remarkable, and bainite structure becomes less likely to be formed. Therefore, 0.3 mass% or more is added. On the other hand, when it contains exceeding 1.5 mass%, grain boundary strength will fall, and also fatigue strength will fall, and also cutting property, cold forging property, and cracking resistance will also fall. For this reason, C was limited to the range of 0.3-1.5 mass%. Preferably it is 0.4-0.6 mass%.

Si: 3.0 mass% or less

Although Si acts not only as a deoxidizer but also contributes to the improvement of strength effectively, when content exceeds 3.0 mass%, the machinability and forging property fall, it is preferable that the amount of Si is 3.0 mass% or less.

Moreover, in order to improve strength, it is preferable to set it as 0.05 mass% or more.

Mn: 2.0 mass% or less

Mn is added because it is a useful component in improving the hardenability and securing the depth of the hardened layer during hardening. When content is less than 0.2 mass%, since the addition effect is lacking, 0.2 mass% or more is preferable. More preferably, it is 0.3 mass% or more. On the other hand, when the amount of Mn exceeds 2.0% by mass, the retained austenite after quenching increases, rather the surface hardness is lowered, and furthermore, the fatigue strength is lowered, so that Mn is preferably 2.0% by mass or less. In addition, when Mn contains much content, hardening of a base material will cause and machinability tends to become disadvantageous, and it is preferable to set it as 1.2 mass% or less. More preferably, it is 1.0 mass% or less.

In this invention, it is important to make the above three components into a basic component, and to satisfy following formula (1) in these basic components.

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn)> 2.0 ... (One)

By adjusting the contents of C, Si, and Mn so as to satisfy the formula (1), the total structure fraction of bainite and martensite as the whole structure of high frequency quenching can be made 10% by volume or more, and curing after high frequency quenching The layer can be made into the tissue of the present invention. Moreover, when the value of Formula (1) is 2.0 or less, the hardness of the hardened layer after high frequency quenching also becomes small, and also it is difficult to ensure sufficient hardened layer depth. In addition to the above basic components, the following Al may be added.

Al: 0.25 mass% or less

Al is an effective element for deoxidation. Moreover, it is an element useful also in miniaturizing the particle diameter of a hardening layer by suppressing austenite particle growth at the time of hardening heating. However, even if it contains content exceeding 0.25 mass%, the effect is saturated, but since the disadvantage which raises component cost rather arises, it is preferable to contain Al in 0.25 mass% or less. More preferably, it is 0.001 to 0.10 mass%.

As mentioned above, although the basic component and Al were demonstrated, in this invention, 1 type, or 2 or more types in 6 components mentioned below can be contained suitably.

Cr: 2.5 mass% or less Cr is effective for improving hardenability, and is an useful element in securing hardening depth. However, when excessively contained, the carbides are stabilized to promote the production of residual carbides, the grain boundary strengths are lowered, and the fatigue strength is degraded. Therefore, it is preferable to reduce Cr content as much as possible, but it is acceptable up to 2.5 mass%. Preferably it is 1.5 mass% or less.

Mo: 1.0 mass% or less

Mo is an element useful for suppressing the growth of austenite particles, and in order to do so, it is preferable to contain it in an amount of 0.05% by mass or more, but when it is added in excess of 1.0% by mass, Mo deteriorates machinability. It is preferable to set it as.

Cu: 1.0 mass% or less

Cu is effective for improving hardenability and is solubilized in ferrite, and this strengthening of solid solution improves fatigue strength. In addition, by suppressing the formation of carbides, the drop of grain boundary strength due to carbides is suppressed and the fatigue strength is improved. However, if the content exceeds 1.0% by mass, cracking occurs during hot working, so it is preferable to add it at 1.0% by mass or less. More preferably, it is 0.5 mass% or less. In addition, when the addition is less than 0.03% by mass, the effect of improving the hardenability and the effect of suppressing the decrease in the grain boundary strength is small.

Ni: 2.5 mass% or less

Since Ni is an element which improves hardenability, it is used when adjusting hardenability. It is also an element that suppresses the formation of carbides, suppresses the decrease in grain boundary strength due to carbides, and improves the fatigue strength. However, since Ni is an extremely expensive element and the cost of steel increases when it exceeds 2.5 mass%, it is preferable to add Ni at 2.5 mass% or less. In addition, when the addition is less than 0.05% by mass, the effect of improving the hardenability and the effect of suppressing the decrease in the grain boundary strength is small. More preferably, it is 0.1-1.0 mass%.

Co: 1.0 mass% or less

Co is an element that suppresses the formation of carbides, suppresses the decrease in grain boundary strength due to carbides, and improves the fatigue strength. However, Co is a very expensive element, and if it is added in excess of 1.0 mass%, the cost of the steel increases, so it is set to 1.0 mass% or less. Moreover, in addition of less than 0.01 mass%, since the fall suppression effect of grain boundary strength is small, it is preferable to add 0.01 mass% or more. More preferably, it is 0.02-0.5 mass%.

V: 0.5 mass% or less

V combines with C and N in steel and acts as a precipitation strengthening element. Moreover, it is an element which improves temper softening resistance, and improves fatigue strength by these effects. However, since the effect is saturated even if it contains exceeding 0.5 mass%, it is preferable to set it as 0.5 mass% or less. In addition, since the improvement effect of fatigue strength is small in addition of less than 0.01 mass%, it is preferable to add in 0.01 mass% or more. More preferably, it is 0.03-0.3 mass%.

W: 1.0 mass% or less

W is an element useful for suppressing the growth of austenite particles, and in order to do so, it is preferable to contain it at 0.005 mass% or more, but when it is added in excess of 1.0 mass%, the machinability deteriorates, W is 1.0 mass% or less. It is preferable to set it as.

When adding 1 type, or 2 or more types of said 6 components to a base component, it is necessary to satisfy following formula (2) for the same reason as said Formula (1).

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 0.5W )> 2.0. (2)

In the present invention, Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, Zr: 0.1 mass% or less, B: 0.01 mass% or less, Ta: 0.5 mass% or less, Hf: 0.5 mass% or less and Sb: 0.015 It can contain 1 type (s) or 2 or more types chosen from mass% or less.

Ti: 0.1 mass% or less

Ti binds to N mixed as an unavoidable impurity, thereby preventing B from becoming a BN and preventing the hardenability improving effect of B from being lost, and sufficiently exhibiting the hardenability improving effect of B.

In order to obtain this effect, it is preferable to contain at 0.005% by mass or more, but when contained in excess of 0.1% by mass, a large amount of TiN is formed, which is a starting point of fatigue breakdown, which causes a significant decrease in fatigue strength. It is preferable to make Ti 0.1 mass% or less. Preferably it is 0.01 to 0.07 mass%.

Nb: 0.1 mass% or less

Nb not only has an effect of improving hardenability, but also combines with C and N in steel to act as a precipitation strengthening element. Moreover, it is an element which improves temper softening resistance, and improves fatigue strength by these effects. However, since the effect is saturated even if it contains exceeding 0.1 mass%, it is preferable to set it as 0.1 mass% or less. In addition, when the addition is less than 0.005% by mass, it is preferable to add 0.005% by mass or more because the effect of enhancing the precipitation strengthening effect and the temper softening resistance is small. More preferably, it is 0.01-0.05 mass%.

Zr: 0.1 mass% or less

Zr not only improves hardenability but also combines with C and N in steel to act as a precipitation strengthening element. Moreover, it is an element which improves temper softening resistance, and improves fatigue strength by these effects. However, since the effect is saturated even if it contains exceeding 0.1 mass%, it is preferable to set it as 0.1 mass% or less. In addition, when the addition is less than 0.005% by mass, it is preferable to add 0.005% by mass or more because the effect of enhancing the precipitation strengthening effect and the temper softening resistance is small. More preferably, it is 0.01-0.05 mass%.

B: 0.01 mass% or less

B is a useful element that not only improves fatigue properties by strengthening grain boundaries but also improves strength, and is preferably added at 0.0003% by mass or more, but since the effect is saturated even when added in excess of 0.01% by mass, 0.01% by mass It limited to the following.

Ta: 0.5 mass% or less

Ta is effective against the delay of the microstructure change, and may be added because it has the effect of preventing the deterioration of fatigue strength, in particular, rolling fatigue. However, even if the content increases more than 0.5 mass%, since it does not contribute to further strength improvement, it is made into 0.5 mass% or less. Moreover, in order to express the improvement effect of fatigue strength, it is preferable to set it as 0.02 mass% or more.

Hf: 0.5 mass% or less

Hf is effective against the delay of the microstructure change, and may be added because it has the effect of preventing the deterioration of fatigue strength, in particular, rolling fatigue. However, even if the content increases more than 0.5 mass%, since it does not contribute to further strength improvement, it is made into 0.5 mass% or less. Moreover, in order to express the improvement effect of fatigue strength, it is preferable to set it as 0.02 mass% or more.

Sb: 0.015 mass% or less

Sb is effective against the delay of the microstructure change, and may be added because it has the effect of preventing the deterioration of fatigue strength, in particular, rolling fatigue. However, since the toughness deteriorates when its content exceeds 0.015 mass%, it is made into 0.015 mass% or less, Preferably it is 0.010 mass% or less. Moreover, in order to express the improvement effect of fatigue strength, it is preferable to set it as 0.005 mass% or more.

When adding 1 type, or 2 or more types of the said 7 components to a base component, it is necessary to satisfy following formula (3) for the same reason as said Formula (1).

^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 1000B) (1 + 0.5W)> 2.0... (3)

Furthermore, in the present invention, S: 0.1% by mass or less, Pb: 0.1% by mass or less, Bi: 0.1% by mass or less, Se: 0.1% by mass or less, Te: 0.1% by mass or less, Ca: 0.01% by mass or less, Mg: 0.01 mass% or less and REM: 0.1 mass% or less can be contained.

S: 0.1 mass% or less

S is a useful element which forms MnS in steel and improves machinability. When it exceeds 0.1 mass%, S segregates at grain boundaries and lowers grain boundary strength, so S is limited to 0.1 mass% or less. Preferably it is 0.04 mass% or less.

Pb: 0.1 mass% or less

Bi: 0.1 mass% or less

Since both Pb and Bi improve the machinability by the melting, lubricating and embrittlement action during cutting, they can be added for this purpose. However, even if it exceeds Pb: 0.1 mass% and Bi: 0.1 mass%, since an effect not only saturates but a component cost rises, it was made to contain in the said range, respectively. In addition, in order to improve machinability, it is preferable to contain Pb 0.01 mass% or more and Bi contain 0.01 mass% or more.

Se: 0.1 mass% or less

Te: 0.1 mass% or less

Se and Te, respectively, combine with Mn to form MnSe and MnTe, which act as chip breakers to improve machinability. However, when the content exceeds 0.1% by mass, not only the effect is saturated but also an increase in the component cost. Therefore, the content is set to 0.1% by mass or less. Moreover, in order to improve machinability, it is preferable to contain in 0.003 mass% or more in the case of Se, and 0.003 mass% or more in case of Te.

Ca: 0.01 mass% or less

REM: 0.1 mass% or less

Ca and REM each form a sulfide together with MnS, which improves machinability by acting as a chip breaker. However, even if Ca and REM exceed 0.01 mass% and 0.1 mass%, respectively, since it not only saturates an effect but raises a component cost, it was made to contain in said range, respectively. In addition, in order to improve machinability, it is preferable to contain Ca 0.0001 mass% or more and REM 0.0001 mass% or more.

Mg: 0.01 mass% or less

Mg is not only an element of deoxidation, but also has an effect of improving the machinability by being a stress concentration source, and thus can be added as necessary. However, when added excessively, not only the effect will be saturated but also the component cost will rise, and it shall be contained in 0.01 mass% or less. Moreover, in order to improve machinability, it is preferable to contain Mg in 0.0001 mass% or more.

The balance other than the elements described above is preferably Fe and unavoidable impurities, and examples of unavoidable impurities include P, O, and N, and each of P: 0.10% by mass, N: 0.01% by mass, and O: 0.008% by mass. Each can be allowed.

Next, the manufacturing method of this invention is demonstrated. The steel material adjusted to the above-mentioned predetermined component composition is subjected to hot working such as hot forging after rolling the steel bar to form a bearing steel part, and quenched on at least the raceway of the parts under heating temperature of 800 to 1000 ° C.

In this series of processes, first hot work is performed with the total processing rate of the temperature zone of 800 to 1000 DEG C or higher at 80% or higher, and then the temperature zone of 700 to 500 DEG C is cooled at a rate of 0.2 DEG C / s or higher, and then 20% or more in the temperature zone below 800 ° C, or hot working in the temperature range of 800 to 1000 ° C with a total processing rate of 80% or more, and then 20% or more in the temperature zone below 800 ° C. After processing, the average particle diameter of the old austenite particle diameter is 12 μm by cooling the temperature zone of 700 to 500 ° C. at a rate of 0.2 ° C./s or more, and by employing the quenching conditions described in detail below. It becomes below, and it becomes possible to set it as the quenched structure whose maximum particle diameter is four times or less of the average particle diameter.

Hereinafter, each regulation is explained in full detail.

[Processing conditions]

The total processing rate at 800-1000 degreeC at the time of hot working is made into 80% or more, and the temperature zone of 700-500 degreeC is cooled at the speed of 0.2 degreeC / s or more after that. By this condition, the structure before quenching can be made into uniform fine bainite and / or martensite structure, and the austenite particle refine | miniaturizes at the time of subsequent quenching heating. More preferably, the cooling rate is at least 0.5 ° C / s.

Further, at least 20% of the processing is carried out in a temperature zone below 800 ° C. before quenching. Processing in a temperature zone below 800 ° C. may be carried out before the cooling of the cooling rate (temperature zone below 700 to 800 ° C.) in the hot working step, or separately cold working after cooling, or at a temperature below the A ₁ transformation point. You may reheat at and warm process. It is preferable to make processing below 800 degreeC into 30% or more. Moreover, as a processing method, cold forging, cold ironing, rolling process, shot etc. are mentioned, for example. By processing at 800 DEG C or lower, the bainite or martensite structure before high frequency quenching becomes fine, and as a result, the average particle diameter of the old austenite particles in the cured layer obtained after the quenching is 12 µm or less, and the maximum particle diameter is It becomes four times or less of an average particle diameter, and a fatigue strength improves by this.

In addition, the processing rate here is a cross-sectional reduction rate before and behind a process in the case of rolling, forging, and drawing. In addition, in the case of a shot etc. which cannot be defined by a cross-sectional reduction rate, it is assumed that it is a hardness change corresponding to a cross-sectional reduction rate.

[Quenching condition]

Heating temperature is 800-1000 degreeC, and 600-800 degreeC is heated up at the temperature increase rate of 400 degreeC / s or more. When the heating temperature is less than 800 ° C., the formation of the austenite structure is insufficient and a hardened layer cannot be obtained. On the other hand, when the heating temperature exceeds 1000 ° C, the growth rate of the austenite particles increases markedly and the average particle diameter increases, and a remarkable difference is likely to occur even in the individual particle growth rate in the rapidly growing temperature zone. The maximum particle diameter is more than four times the average particle diameter, resulting in a drop in fatigue strength.

Moreover, even when the temperature increase rate of 600-800 degreeC is less than 400 degreeC / s, growth of austenite particle | grains is accelerated | stimulated, the particle size variation becomes large, the maximum particle diameter exceeds four times the average particle diameter, and fatigue strength Results in degradation. It is presumed that this is because, if the temperature rise rate is slow, reverse transformation from ferrite to austenite is initiated at a lower temperature, and it is easy to cause uneven grain growth by place.

Moreover, it is preferable to make heating temperature into 800-950 degreeC, and it is preferable that the temperature increase rate of 600-800 degreeC is 700 degreeC or more. More preferably, it is 1000 degreeC / s or more.

In addition, when the residence time of 800 ° C. or more becomes longer during heating, austenite particles grow, and as a result, the maximum particle diameter tends to be more than four times the average particle diameter. Therefore, the residence time of 800 ° C. or more is 5 seconds or less. It is preferable. As a method of satisfying such conditions, it is particularly preferable to use high frequency heating.

The bearing steel parts in this invention manufactured by the above manufacturing method are applicable as bearing components, such as a bearing steel ball or a bearing steel roller, a bearing inner ring, and a bearing outer ring, as mentioned above. Here, which of these parts can be appropriately selected. The bearing steel ball or roller, bearing inner ring, and bearing outer ring may be used for the parts having the weakest electric fatigue life depending on the shape and the number of bearing steel balls or rollers.

Example 1

As shown in FIG. 3, a bearing 10 having a bearing outer ring 3, a bearing inner ring 1, and a bearing steel ball 4 was manufactured as a bearing part.

The bearing inner ring 1 fits the shaft portion 2 to the inner circumferential surface thereof, and constitutes a bearing via a bearing steel ball 4 inserted between the outer ring 3 and the outer ring 3. As shown in FIG. 3, the bearing steel sphere 4, the contact surface 31 (spinning surface 31) with the bearing steel sphere 4 of the bearing outer ring 3, and the bearing steel sphere of the bearing inner ring 1. The contact surface 11 (electric pole surface 11) with (4) is required to improve the rolling fatigue life. First, the Example which applied this invention to the bearing inner ring 1 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it formed into the bearing inner ring by hot forging, and then cooled at the cooling rate shown in Table 3. Subsequently, after cutting or cold forging, the outer circumferential surface on which the bearing steel balls of the bearing inner ring are rolled is formed, and then quenched under high frequency under the conditions shown in Table 3 to form a quenched tissue layer. Tempering of powder was performed, and further finishing processing was carried out to make a product. Here, tempering was omitted for some of the bearing inner rings (hereinafter, simply referred to as inner rings). In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the area change rate of the cross section which goes straight to the axial direction with respect to the raceway. Table 3 shows the results of the investigation into the rolling fatigue life of the inner ring thus obtained.

Here, the electric fatigue life of the inner ring was evaluated as follows. The shaft portion 2 is fitted to the inner circumferential surface of the inner ring 1, the bearing steel balls 4 (hereinafter simply referred to as steel balls 4) are disposed on the outer circumferential surface of the inner ring 1, and the bearing outer ring 3 is provided. ) (Hereinafter simply referred to as outer ring 3) and the inner ring 1 in a state in which a constant load 900N is applied to the outer ring 3 as shown in FIG. 4 in a state where the outer ring 3 is fixed. ), The endurance test for rotating at a constant rotational speed (300 rpm) was performed, and the time until the quenched tissue layer 22 was broken by rolling fatigue was evaluated as rolling fatigue life.

In addition, this rolling fatigue life was shown by the relative ratio at the time of making the rolling fatigue life of the prior art example of No. 22 (the thing which applied the hot working and high frequency quenching conditions other than this invention) of Table 3 as 1.

In addition, the dimension and shape of other outer ring, steel ball, etc. were set here so that the shaft raceway surface of an inner ring might be the weakest part at the time of an endurance test.

Moreover, about the same inner ring, the hardening structure was calculated | required the average sphere austenite particle diameter and the largest sphere austenite particle diameter of a hardened layer by the method similar to the method mentioned above.

These results are also listed in Table 3.

Table 3 (continued)

As is apparent from Table 3, all of the inner rings having the hardened layer having the quenched structure, in which the average particle diameter of the old austenite particles were 12 µm or less and the maximum particle diameter was 4 times or less the average particle diameter, were 10 compared with the conventional example. An excellent electric fatigue life of more than twice was obtained.

On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

Next, the Example which applied this invention to the bearing outer ring 3 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it shape | molded by the bearing outer ring by hot forging, and cooled at the cooling rate shown in Table 3. After forming the inner circumferential surface through which the bearing steel balls of the bearing outer ring are driven by cutting or cold forging, and then quenching under high frequency under the conditions shown in Table 3 to form the quenched tissue layer, 170 ° C and 30 ° C are used using a heating furnace. Tempering of powder was performed, and further finishing processing was carried out to make a product. Here, tempering was abbreviate | omitted about some bearing outer ring (henceforth simply an outer ring). In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the area change rate of the cross section which goes straight to the axial direction with respect to the raceway.

Table 3 shows the results of investigating the rolling fatigue life of the outer ring thus obtained.

The rolling fatigue life of the outer ring was evaluated as follows.

On the inner circumferential surface of the outer ring 3, a bearing steel ball 4 (hereinafter referred to simply as steel ball 4) is arranged, and a bearing inner ring 1 (hereinafter referred to simply as inner ring 1) is mounted. As shown in FIG. 4 in a state where the outer ring 3 is fixed, an endurance test is performed in which the inner ring 1 is rotated at a constant rotational speed (300 rpm) while a constant load 900N is applied to the outer ring 3. , The time until the quenched tissue layer 22 was broken by the rolling fatigue was evaluated as the rolling fatigue life.

In addition, this rolling fatigue life was shown by the relative ratio at the time of making the rolling fatigue life of the prior art example of No. 22 (the thing which applied the hot working and high frequency quenching conditions other than this invention) of Table 3 as 1.

In addition, the dimension and shape of other inner rings, steel balls, etc. were set here so that the shaft raceway surface of an outer ring might be the weakest part at the time of an endurance test.

Moreover, about the same outer ring, the hardening structure was calculated | required the average sphere austenite particle diameter and the largest sphere austenite particle diameter of a hardened layer by the method similar to the above-mentioned method.

These results are also listed in Table 3.

As is apparent from Table 3, all of the inner rings having the hardened layer having the quenched structure, in which the average particle diameter of the old austenite particles were 12 µm or less and the maximum particle diameter was 4 times or less the average particle diameter, were 10 compared with the conventional example. An excellent electric fatigue life of more than twice was obtained.

On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

Moreover, the Example at the time of applying this invention to the bearing steel ball 4 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it hot-forged and adjusted the bar steel diameter, and cooled at the cooling rate shown in Table 3. In addition, the diameter was adjusted by cutting or cold forging. The steel material thus obtained was cut and formed into a bearing steel sphere, and then quenched under high frequency under the conditions shown in Table 3 to form a quenched tissue layer, and then tempered at 170 ° C. for 30 minutes using a heating furnace, followed by further finishing. It was made into the product. Here, tempering was omitted for some bearing steel balls (hereinafter, simply referred to as steel balls). In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the cross-sectional reduction rate. Table 3 shows the results of investigating the rolling fatigue life of the steel balls thus obtained.

The rolling fatigue life of the steel ball was evaluated as follows. Fit the shaft portion 2 to the inner circumferential surface of the bearing inner ring 1, arrange the bearing steel balls 4 (hereinafter simply referred to as steel balls 4) on the outer circumferential surface of the inner ring 1, and then the bearing outer ring ( 3) (hereinafter, simply referred to as outer ring 3) and the inner ring 1 in a state in which a constant load 900N is applied to the outer ring 3 as shown in FIG. 4 in a state where the outer ring 3 is fixed. ), The endurance test for rotating at a constant rotational speed (300 rpm) was performed, and the time until the quenched tissue layer 22 was broken by rolling fatigue was evaluated as rolling fatigue life.

In addition, this rolling fatigue life was shown by the relative ratio in Table 3 which made the rolling fatigue life of the prior art example of No. 22 (the thing which applied the hot working and high frequency quenching conditions other than this invention) to 1.

In addition, the dimension and shape of other outer ring, inner ring, etc. were set here so that the surface of a steel ball might be the weakest part at the time of an endurance test.

Moreover, about the same steel sphere, the hardening structure was calculated | required the average sphere austenite particle diameter and maximum sphere austenite particle diameter of a hardened layer by the method similar to the method mentioned above.

These results are also listed in Table 3.

As is apparent from Table 3, all the steel balls having a hardened layer having a quenched structure in which the average particle diameter of the old austenite particles were 12 µm or less and the maximum particle diameter was 4 times or less the average particle diameter were all 10 compared with the conventional example. An excellent electric fatigue life of more than twice was obtained.

On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

Example 2

Next, as shown in FIG. 5, a bearing 20 having a bearing outer ring 8, a bearing inner ring 6, and a roller 9 was manufactured as a bearing steel part.

The bearing inner ring 6 fits the shaft portion 2 to the inner circumferential surface thereof, and constitutes a bearing via the roller 9 inserted between the outer ring 8 and the outer circumferential surface thereof. As shown in this FIG. 5, the roller 9, the contact surface 81 with the roller 9 of the bearing outer ring 8 (rolling surface 81), and the contact surface with the roller 9 of the bearing inner ring 6 ( 61) (Curning surface 61) is required to improve the rolling fatigue life.

First, the Example which applied this invention to the bearing inner ring 6 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it shape | molded by the bearing inner ring by hot forging, and cooled at the cooling rate shown in Table 4. Subsequently, the outer peripheral surface to which the roller of a bearing inner ring rolls is formed by cutting or cold forging, Next, high frequency quenching is formed on the conditions shown in Table 4, and a hardened structure layer is formed, and it uses 170 degreeC and 30 minutes using a heating furnace. Tempering was performed, and further finishing processing was carried out to obtain a product. Here, tempering was omitted for some of the bearing inner rings (hereinafter, simply referred to as inner rings). In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the area change rate of the cross section which goes straight to the axial direction with respect to the raceway. Table 4 shows the results of the investigation into the rolling fatigue life of the inner ring thus obtained. Here, the electric fatigue life of the inner ring was evaluated as follows.

Fit the shaft part 2 to the inner peripheral surface of the inner ring 6, arrange | position the roller 9 to the outer peripheral surface of the inner ring 6, and attach the bearing outer ring 8 (henceforth the outer ring 8). As shown in FIG. 6 in the state which fixed the outer ring 8, the endurance test which rotates the inner ring 6 at a fixed rotational speed (300 rpm) is performed in the state which applied the fixed load 900N to the outer ring 8. As shown in FIG. Then, the time until the quenched tissue layer 22 was broken by rolling fatigue was evaluated as rolling fatigue life.

In addition, this rolling fatigue life was shown in Table 4 by the relative ratio when the rolling fatigue life of the prior art example of N0.22 (The thing which applied the hot working and high frequency quenching conditions other than this invention) was made into one. In addition, the dimension and shape of other outer ring | wheel, roller, etc. were set here so that the shaft raceway surface of an inner ring may be the weakest part at the time of an endurance test. Moreover, about the same inner ring, the hardening structure was calculated | required the average sphere austenite particle diameter and the largest sphere austenite particle diameter of a hardened layer by the method similar to the method mentioned above. These results are also listed in Table 4.

Table 4 (continued)

As is apparent from Table 4, all of the inner rings having a hardened layer having a quenched structure whose average particle diameter of the old austenite particles is 12 μm or less and the maximum particle diameter are 4 times or less of the average particle diameter are all 10 compared with the conventional example. An excellent electric fatigue life of more than twice was obtained.

On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

Next, the Example which applied this invention to the bearing outer ring 8 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it shape | molded by the bearing outer ring by hot forging, and cooled at the cooling rate shown in Table 4. After forming the inner circumferential surface on which the bearing steel balls of the bearing outer ring are driven by cutting or cold forging, and then quenching under high frequency under the conditions shown in Table 4 to form a quenched tissue layer, 170 ° C and 30 ° C are heated using a heating furnace. Tempering of powder was performed, and further finishing processing was carried out to make a product. Here, tempering was abbreviate | omitted about some bearing outer ring (henceforth simply an outer ring). In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the area change rate of the cross section which goes straight to the axial direction with respect to the raceway.

Table 4 shows the results of investigating the rolling fatigue life of the outer ring thus obtained.

The rolling fatigue life of the outer ring was evaluated as follows. The roller 9 is arranged on the inner circumferential surface of the outer ring 8, the bearing inner ring 6 (hereinafter referred to simply as the inner ring 6) is mounted, and is shown in FIG. 6 in a state where the outer ring 8 is fixed. As described above, an endurance test is performed in which the inner ring 6 is rotated at a constant rotational speed (300 rpm) while a constant load 900N is applied to the outer ring 8, until the quenched tissue layer 22 is broken by electric fatigue. The time was evaluated as the rolling fatigue life.

In addition, this rolling fatigue life was shown by the relative ratio at the time of making the rolling fatigue life of the prior art example of No. 22 (the thing which applied the hot working and high frequency quenching conditions other than this invention) of Table 4 as 1.

In addition, the dimension and shape of other inner ring | wheel, roller, etc. were set here so that the shaft transmission surface of an outer ring may be the weakest part at the time of an endurance test. Moreover, about the same outer ring, the hardening structure was calculated | required the average sphere austenite particle diameter and the largest sphere austenite particle diameter of a hardened layer by the method similar to the above-mentioned method.

These results are also listed in Table 4. As is apparent from Table 4, all of the outer rings having a hardened layer whose hardened layer had a quenched structure whose average particle diameter of the old austenite particles were 12 µm or less and the maximum particle diameter was 4 times or less the average particle diameter were all 10 compared with the conventional example. An excellent electric fatigue life of more than twice was obtained.

On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

Moreover, the Example at the time of applying this invention to the roller 9 is demonstrated. The steel raw material used as the component composition shown in Table 2 was melted by the converter, and it was set as the cast by continuous casting. The slab size was 300 × 400 mm. This cast piece was rolled into a billet of 150 mm in length and width through a breakdown step, and then rolled into a rod steel of 24 mm Φ. Subsequently, after cutting this bar steel to predetermined length, it performed by hot forging, adjusted the bar steel diameter, and cooled at the cooling rate shown in Table 4. Furthermore, the diameter was adjusted by cutting or cold forging. The obtained steel material was cut and formed into a bearing steel sphere, and then quenched under high frequency under the conditions shown in Table 4 to form a hardened tissue layer, and then tempered at 170 ° C. for 30 minutes using a heating furnace, and further finished. The product was processed to obtain a product. Here, tempering was abbreviate | omitted about some rollers. In addition, the total work rate in hot forging and cold forging was adjusted by adjusting the cross-sectional reduction rate.

Table 8 shows the results of the investigation on the rolling fatigue life of the roller thus obtained. The rolling fatigue life of the roller was evaluated as follows.

The shaft portion 2 is fitted to the inner circumferential surface of the bearing inner ring 6, the roller 9 is disposed on the outer circumferential surface of the inner ring 6, and the bearing outer ring 8 (hereinafter, simply referred to as outer ring 8) is formed. 6, the endurance test for rotating the inner ring 6 at a constant rotational speed (300 rpm) in a state in which a constant load 900N is applied to the outer ring 8 as shown in FIG. 6 while the outer ring 8 is fixed. It carried out and evaluated the time until the hardened structure layer 22 breaks by a rolling fatigue as a rolling fatigue life.

In addition, this rolling fatigue life was shown by the relative ratio at the time of making the rolling fatigue life of the prior art example of No. 22 (the thing which applied the hot working and high frequency quenching conditions other than this invention) of Table 4 as 1.

In addition, the dimension and shape of other outer ring, inner ring, etc. were set here so that the surface of a roller might be the weakest part at the time of an endurance test.

Moreover, about the same roller, the hardening structure was calculated | required the average sphere austenite particle diameter and maximum sphere austenite particle diameter of a hardened layer by the method similar to the above-mentioned method. These results are also listed in Table 4. As is apparent from Table 4, all steel balls having a hardened layer having a hardened layer whose hardened layer had an average particle diameter of 12 µm or less and a maximum particle diameter of 4 times or less of the average particle diameter were 10 compared with the conventional example. Excellent rolling fatigue life of more than twice can be obtained. On the other hand, the comparative example in which the average particle diameter of the old austenite particles is 12 µm or less and the maximum particle diameter does not become 4 times or less of the average particle diameter has a short rolling fatigue life.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the method of the electric fatigue test.

2A and 2B are graphs showing the influence of the old austenite particle diameter and the maximum old austenite particle diameter / average old austenite particle diameter on the rolling fatigue life.

3 is a view for explaining the components constituting the bearing.

It is a figure which shows the method of the electric fatigue test of a bearing.

It is a figure explaining the components which comprise a roller bearing.

It is a figure which shows the method of the electric fatigue test of a roller bearing.

Explanation of symbols on the main parts of the drawings

1: bearing inner ring 2: shaft portion

3: bearing outer ring 4: bearing steel ball

6: bearing inner ring 8: bearing outer ring

9: roller 11: front surface of bearing inner ring

22: quenched layer structure 31: transmission surface of the bearing outer ring

Claims (20)

Bearing steel parts quenched on the transmission surface, the quenched structure is characterized in that the bearing steel is characterized in that the average particle diameter of spherical austenite particles is 12 µm or less and the maximum particle diameter is 4 times or less the average particle diameter. part. The method of claim 1, C: 0.3-1.5 mass%, Si: 3.0 mass% or less and Mn: 2.0 mass% or less And the following formula (1), and the balance has a component composition of Fe and unavoidable impurities. ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn)> 2.0 ... (One) The method of claim 2, As said ingredient composition, Furthermore, Al: 0.25 mass% or less Bearing steel parts comprising a. The method of claim 2, As said ingredient composition, Furthermore, Cr: 2.5 mass% or less, Mo: 1.0 mass% or less, Cu: 1.0 mass% or less, Ni: 2.5 mass% or less, Co: 1.0 mass% or less, V: 0.5 mass% or less and W: 1.0 mass% or less The bearing steel component containing 1 type (s) or 2 or more types selected from among, and satisfy | filling following Formula (2) instead of said Formula (1). ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 0.5W )> 2.0. (2) The method according to any one of claims 2 to 4, As said ingredient composition, Furthermore, Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, Zr: 0.1 mass% or less, B: 0.01 mass% or less, Ta: 0.5 mass% or less, Hf: 0.5 mass% or less and Sb: 0.015 mass% or less The bearing steel component which contains the 1 type (s) or 2 or more types selected from among, and satisfy | fills following Formula (3) instead of said Formula (1) or (2). ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 1000B) (1 + 0.5W)> 2.0... (3) The method according to any one of claims 2 to 4, As said ingredient composition, Furthermore, S: 0.1 mass% or less, Pb: 0.1 mass% or less, Bi: 0.1 mass% or less, Se: 0.1 mass% or less, Te: 0.1 mass% or less, Ca: 0.01 mass% or less, Mg: 0.01 mass% or less and REM: 0.1 mass% or less Bearing steel parts characterized by containing one or two or more selected from. The bearing steel part according to any one of claims 1 to 4, wherein the bearing steel part is a ball or roller for bearing. The bearing steel part according to any one of claims 1 to 4, wherein the bearing steel part is a bearing inner ring or a bearing outer ring. It is made of steel materials containing at least 10% by volume of any one or both of the fine bainite structure and the fine martensite structure in total, and at least a portion of the material has a temperature raising rate of 400 ° C / s or more and an attainment temperature of 1000 ° C or less. A high frequency heating is performed at least once. 10. The method of claim 9, wherein the raw material is a hot working step in which the total working rate at 800 to 1000 ° C. is 80% or more, and a cooling rate of 0.2 ° C./s or more in a temperature zone of 700 to 500 ° C. after the hot working step. and a cooling step of cooling to a further embodiment more than 700 ~ 20% in the temperature region of less than 800 ℃ processing before the cooling step, or to carry out more than 20% of processing in the temperature region of more than a ₁ point transformation point after the cooling step The manufacturing method of the bearing steel component characterized by manufacturing through a 2nd processing process. The method of manufacturing a bearing steel part according to claim 9 or 10, wherein a residence time of 800 ° C or more in one high frequency heating is set to 5 seconds or less. The method according to claim 9 or 10, The steel, C: 0.3-1.5 mass%, Si: 3.0 mass% or less and Mn: 2.0 mass% or less And satisfying the following formula (1), the balance having a component composition consisting of Fe and unavoidable impurities. ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn)> 2.0 ... (One) The method of claim 12, The steel, in addition, Al: 0.25 mass% or less A method for producing a bearing steel part, comprising a. The method of claim 12, The steel, in addition, Cr: 2.5 mass% or less, Mo: 1.0 mass% or less, Cu: 1.0 mass% or less, Ni: 2.5 mass% or less, Co: 1.0 mass% or less, V: 0.5 mass% or less and W: 1.0 mass% or less It contains the 1 type (s) or 2 or more types chosen from among, and is a composition which satisfy | fills following formula (2) instead of said Formula (1), The manufacturing method of the bearing steel component characterized by the above-mentioned. ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 0.5W )> 2.0. (2) The method of claim 12, As the component composition, Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, Zr: 0.1 mass% or less, B: 0.01 mass% or less, Ta: 0.5 mass% or less, Hf: 0.5 mass% or less and Sb: 0.015 mass% or less It contains 1 type (s) or 2 or more types selected from among, and satisfy | fills following formula (3) instead of said formula (1) or (2), The manufacturing method of the bearing steel component characterized by the above-mentioned. ^{C 1/2 (1 + 0.7Si} ) (1 + 3Mn) (1 + 2.1Cr) (1 + 3.0Mo) (1 + 0.4Cu) (1 + 0.3Ni) (1 + 5.0V) (1 + 1000B) (1 + 0.5W)> 2.0... (3) The method of claim 12, As said ingredient composition, Furthermore, S: 0.1 mass% or less, Pb: 0.1 mass% or less, Bi: 0.1 mass% or less, Se: 0.1 mass% or less, Te: 0.1 mass% or less, Ca: 0.01 mass% or less, Mg: 0.01 mass% or less and REM: 0.1 mass% or less The manufacturing method of the bearing steel component characterized by containing 1 type (s) or 2 or more types selected from among. The method of manufacturing a bearing steel part according to claim 9 or 10, wherein the bearing steel part is a ball or roller for bearing. The method of manufacturing a bearing steel part according to claim 9 or 10, wherein the bearing steel part is a bearing inner ring or a bearing outer ring. The bearing in which the bearing steel component of Claim 7 is used as a bearing sphere or a roller. The bearing in which the bearing steel component of Claim 8 is used as a bearing inner ring or an outer ring.

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