JPH06299240A - Manufacture of steel material for bearing having excellent spheroidizing characteristic - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a steel material for bearing which can obtain the uniform spheroidal carbide structure without containing coarse flaky carbide by the ordinary spheroidizing and has excellent cold- workability after annealing and rolling fatigue resistant characteristic in the bearing parts executing the quenching and the tempering treatment. CONSTITUTION:At the time of hot-rolling the steel containing 0.8-1.2% C and the other specific composition, the rolling is executed in the specific rolling condition having an intermediate cooling, in which after rolling, immediately the steel material temp. is cooled so as to become once Ms point-700 deg.C, and making the steel material temp. at the outlet side of the finish rolling at 700-880 deg.C. After finish-rolling, this steel material is rapidly cooled at 550-700 deg.C, and thereafter cooled to >=450 deg.C at 0.05-1 deg.C/sec average cooling velocity. By this method, the steel material for bearing having excellent spheroidizing- characteristic composed of substantially proeutectoid cementite and pearlite in the structure can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a bearing steel material having excellent spheroidizing annealing characteristics. More specifically, it reduces reticulated proeutectoid cementite in the production of a bearing steel material, In a bearing part that has been hardened and tempered, it is possible to obtain a uniform spherical carbide structure that does not contain coarse plate-shaped carbides, has excellent cold workability such as cutting after annealing, cold forging, and cutting. The present invention relates to a method for manufacturing a bearing steel material capable of obtaining excellent rolling fatigue characteristics.

[0002]

2. Description of the Related Art Bearing parts are usually manufactured by performing cold working such as cutting, cold forging, and cutting of steel bar wire rods. In cold working, as-rolled steel is too hard and cold working is difficult. Therefore, spheroidizing annealing is performed before cold working for the purpose of improving cold workability. However, an ordinary spheroidized annealing structure is composed of fine spherical carbides and coarse plate-shaped carbides, and it is extremely difficult at present to obtain a uniform spherical carbide structure. Such non-uniformity of the carbide structure deteriorates cold workability and also causes deterioration of rolling contact fatigue life in the final part.

On the other hand, in Japanese Patent Laid-Open No. 64-55330, a steel consisting of specific components has an Ac ₃ point or an Ac cm.
Heating above the point, processing rate 1 in austenite unrecrystallized region
A method for producing a steel material capable of spheroidizing for a short time is shown, which comprises performing hot rolling at 0 to 80% and cooling to a temperature range just above the Ms point at a cooling rate of 1.5 to 100 ° C / sec. Has been done. However, in this method, since the rolled material has a fine pearlite or bainite structure, it is possible to spheroidize in a short time, but the spherical carbide obtained from the fine pearlite or bainite structure part becomes remarkably fine, and grain It can be said that a sufficiently uniform spheroidal carbide structure cannot be obtained because of a large difference from the size of the spheroidal carbide obtained from the field proeutectoid cementite portion.

Further, in Japanese Patent Laid-Open No. 3-53021,
Steel consisting of specific components is heated to a temperature of Ar ₁ + 200 ° C. or higher, hot rolling is performed at a reduction rate of 20 to 90%, and then hot rolling of 20 to 90% is performed at Ar ₁ to Ar ₁ + 200 ° C. 5 to a temperature of Ar ₁ ~Ar ₁ + 200 ℃ after performing
A method for producing a high carbon steel material for spheroidizing annealing, which is characterized by holding for 900 seconds, is shown. It is said that the use of this method can obtain a desired pre-structure for shortening the spheroidizing annealing time, but the reduction of reticulated pro-eutectoid cementite by this method is not always sufficient.

[0005]

The object of the present invention is to obtain a uniform spheroidal carbide structure which does not contain coarse plate-shaped carbides by ordinary spheroidizing annealing, and is capable of cutting after annealing and cold working. An object of the present invention is to provide a method for manufacturing a bearing steel material which is excellent in cold workability such as forging and cutting, and which can obtain excellent rolling fatigue characteristics in a bearing component subjected to quenching and tempering.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to obtain a uniform spheroidized structure that does not contain coarse plate-shaped carbides by ordinary spheroidization annealing and obtained the following findings. . (1) In order to obtain a uniform spheroidized structure that does not contain coarse plate-like carbides by ordinary spheroidizing annealing, the rolled material should have a reduced reticulated pro-eutectoid cementite and an intra-precipitated cementite in the austenite grains. Of the pearlite and the coarsening of the lamellar spacing of pearlite.

(2) In order to realize the above, the following five points are essential. Using a steel material containing carbonitride-forming elements such as specific amounts of Al and N, the rolling heating temperature is limited to 900 to 1150 ° C. to prevent coarsening of austenite grains at the time of rolling heating, and to partially fine Retaining carbides to reduce the net amount of solid solution carbon and make it difficult to form reticulated pro-eutectoid cementite after rolling. Total area reduction of 50% in the temperature range from heating temperature to 880 ℃ or higher
The above rolling is performed and the austenite grains are recrystallized to 6
Granulate to ~ 7.

In the temperature range of less than 880 ° C to 400 ° C,
"After rolling with a surface reduction rate of 10% or more, the steel temperature immediately increases to M
The temperature of the steel material on the delivery side of the final rolling is 700 to 700 ° C., and the steel sheet is cooled to s point to 700 ° C. and then rolled at a reduction rate of 10% or more.
By setting the temperature to 880 ° C., a deformation zone is introduced into the austenite grains to nucleate intragranular pro-eutectoid cementite to reduce reticulated pro-eutectoid cementite and to suppress growth coarsening of the austenite grains.

Immediately after the final rolling, the steel is rapidly cooled to a final rolling quenching temperature of 550 to 700 ° C. or quenched into a molten salt maintained at a molten salt temperature of 550 to 700 ° C. Of reticulated pro-eutectoid cementite at the boundary-
Control growth. After that, up to 450 ° C at a cooling rate of 0.05 to 1.0 ° C /
Cooling in seconds to coarsen the lamellar spacing of pearlite formed in austenite grains.

(3) Further, when heating in hot rolling,
By setting the heating rate of 650 to 750 ° C. to 10 to 100 ° C./hour, the residual amount of fine carbide during heating is increased, the net amount of dissolved carbon is further reduced, and the amount of reticulated pro-eutectoid cementite after rolling is increased. Is also reduced. The present invention has been made based on the above new findings, and the gist thereof is as follows.

According to the first aspect of the present invention, the weight ratio is as follows.
C: 0.80 to 1.20%, Si: 0.15 to 1.50
%, Mn: 0.15 to 1.50%, Cr: 0.50 to 1.6
0%, S: 0.003 to 0.02%, Al: 0.015
.About.0.05%, N: 0.004 to 0.015%, P: 0.020% or less, Ti: 0.0020% or less,
O: When the steel having a balance of iron and inevitable impurities is restricted to 0.0015% or less, A) a step of heating to a heating temperature of 900 to 1150 ° C., and B) the heating temperature to 880 Total area reduction of 5 in the temperature range above ℃
0% or more rolling, C) after that, in a temperature range of less than 880 ℃ ~ 400 ℃,
"After rolling with a surface reduction rate of 10% or more, the steel temperature immediately increases to M
The temperature of the steel material on the outgoing side of the final rolling is 700 to 880, and the rolling temperature is 700 to 880 ° C., and the steel sheet temperature on the delivery side of the final rolling is 700 to 880.
A step of setting the final rolling outlet temperature to ℃, and D) quenching immediately after the final rolling to raise the temperature of the steel material to 550
To 700 ° C. for the final rolling quenching temperature, and E) thereafter cooling up to 450 ° C. at a cooling rate of 0.05 to 1.0 ° C./sec. And a pearlite, which are excellent in spheroidizing annealing characteristics.

In the invention of claim 2 of the present invention, the above D) and E) are: D) immediately after the final rolling, quenching into a molten salt maintained at a molten salt temperature of 550 to 700 ° C. 0.5 in salt
2. The structure according to claim 1, wherein the holding is ˜30 seconds, and E) the subsequent cooling up to 450 ° C. at a cooling rate of 0.05 to 1.0 ° C./second. And a pearlite, which are excellent in spheroidizing annealing characteristics.

In the invention of claim 3 of the present invention, the heating rate at 650 to 750 ° C. is 10 to 10 in heating in hot rolling.
The method for producing a bearing steel material having excellent spheroidizing annealing properties according to claim 1 or 2, wherein the temperature is 0 ° C / hour.

According to a fourth aspect of the present invention, the components are further Ni: 0.50 to 2.00%, Mo: 0.05 to 0.5.
The method for producing a steel material for bearings having excellent spheroidizing annealing characteristics according to claim 1, 2 or 3, containing 0% of 1 type or 2 types.

In the invention of claim 5 of the present invention, the components are further Nb: 0.01 to 0.3%, V: 0.03 to 0.3.
%, 1 type or 2 types, is a manufacturing method of the steel material for bearings excellent in the spheroidizing annealing characteristic of Claim 1 or 2 or 3 or 4.

[0016]

The present invention will be described in detail below. First, the reason why the component content range of the steel of the present invention is limited as described above will be described. C: 0.80 to 1.20%, C is an element effective for obtaining the rolling fatigue strength and wear resistance required as a bearing component of the final product, but if less than 0.80%, the effect is unsatisfactory. When the content exceeds 1.20%, the amount of reticulated grain boundary pro-eutectoid cementite becomes remarkable, resulting in deterioration of workability after spheroidizing annealing and deterioration of strength of the final product. It was set to .20%.

Si: 0.15 to 1.50%, Si is added as a deoxidizing element and for the purpose of increasing the strength of the final product by suppressing the structural change in the rolling fatigue process, but 0.15%. If the content is less than 0.1%, the effect is insufficient. On the other hand, if it exceeds 1.50%, these effects are saturated and rather the toughness of the final product is deteriorated.
It was set to 5 to 1.50%.

Mn: 0.15 to 1.50%, Mn is an element effective in increasing the strength of the final product by improving the hardenability, but if it is less than 0.15%, this effect is insufficient. On the other hand, on the other hand, if it exceeds 1.5%, this effect is saturated and rather the toughness of the final product is deteriorated, so the content was made 0.15 to 1.5%.

Cr: 0.50 to 1.60%, Cr is effective in improving the hardenability, strengthening the toughness, promoting the formation of carbides and improving the wear resistance. This effect is insufficient below 0.5%, while 1.
If it exceeds 6%, this effect is saturated and rather the toughness of the final product is deteriorated, so the content was made 0.50 to 1.60%.

S: 0.003 to 0.02%, S is M in steel
It exists as nS and contributes to improvement of machinability and refinement of the structure, but if it is less than 0.003%, its effect is insufficient. On the other hand, when it exceeds 0.02%, the effect is saturated,
Rather, it causes deterioration of toughness and increase of anisotropy. For the above reason, the S content is set to 0.003 to 0.02%.

Al: 0.015 to 0.05%, Al is added as a deoxidizing element and a crystal grain refining element, but 0.0
If it is less than 15%, its effect is insufficient, while on the other hand, it is 0.0.
If it exceeds 5%, the effect is saturated and rather the toughness is deteriorated, so the content was made 0.015-0.05%.

N: 0.004 to 0.015%, N is AlN
Although it contributes to the refinement of austenite grains through the precipitation behavior of, the effect is insufficient if it is less than 0.004%, while on the other hand, if it exceeds 0.015%, the effect saturates and rather deteriorates the toughness. , Its content is N: 0.004
˜0.015%.

P: 0.020% or less, P causes grain boundary segregation or center segregation in the steel and causes deterioration of strength of the final product. In particular, when P exceeds 0.020%, the deterioration of strength becomes remarkable, so 0.020% was made the upper limit.

Ti: 0.0020% or less, Ti forms a hard precipitate TiN, which becomes a starting point of rolling fatigue fracture in the final product and causes strength deterioration. Especially Ti is 0.
If it exceeds 0020%, the strength will be significantly deteriorated.
The upper limit was 0.0020%.

O: 0.0015% or less O forms hard inclusions Al ₂ O ₃ , which becomes a starting point of rolling fatigue fracture in the final product and causes strength deterioration. In particular, when O exceeds 0.0015%, the deterioration of strength becomes remarkable, so 0.0005% was made the upper limit.

Next, in the steel of the fourth aspect of the invention, one or two kinds of Ni and Mo can be contained for the purpose of improving hardenability. Ni: 0.50 to 2.00%, Mo:
0.05 to 0.50%, Ni and Mo are effective elements for increasing the strength of the final product by improving the hardenability, but Ni: less than 0.50%, Mo: less than 0.05%. However, this effect is insufficient, while Ni: 2.00%, M
If the content of o: 0.5% is exceeded, this effect is saturated and rather the toughness of the final product is deteriorated. Therefore, the content is Ni: 0.5.
0 to 2.00% and Mo: 0.05 to 0.50%.

Next, in the steel according to the fifth aspect of the invention, one or two kinds of Nb and V can be contained for the purpose of refining the structure. Nb: 0.01 to 0.3%, V: 0.0
3 to 0.3%, Nb and V are added as crystal grain refining elements, but if Nb: less than 0.01% and V: less than 0.03%, the effect is insufficient, while Nb: 0%. .3%, V:
If the content exceeds 0.3%, the effect is saturated and rather the toughness is deteriorated, so the content is Nb: 0.01 to 0.3%,
V: 0.03 to 0.3%.

Next, the reason for limiting the hot rolling conditions in the present invention will be described. First, heating temperature is 900 ~
The reason why 1150 ° C. is set is that at a heating temperature of less than 900 ° C., the coarse rolling-intermediate rolling temperature becomes low, and the austenite grains are not sufficiently refined by the recrystallization zone rolling. Then, since the austenite crystal grains are remarkably coarsened, the effect of reducing the amount of solid dissolved carbon due to the residual fine carbide cannot be expected.

Next, the reason why rolling with a total surface reduction rate of 50% or more is performed within the temperature range of the heating temperature to 880 ° C. or more is to recrystallize the austenite grains into about 6 to 7 grains. The reason why the total area reduction rate is 50% or more is that the effect of recrystallizing and refining is small when the total area reduction rate is less than 50%.

Further, in a temperature range of less than 880 ° C to 400 ° C, "after the rolling with a surface reduction rate of 10% or more, immediately, the steel material temperature is once cooled to the Ms point to 700 ° C, and subsequently the surface reduction rate is reduced. Rolling in a process that has one or more steps of "rolling 10% or more" introduces a deformation zone into the austenite grains to nucleate the intragranular pro-eutectoid cementite and reduce the reticulated pro-eutectoid cementite. This is because The reason for interposing cooling during rolling is to suppress the release of processing strain due to recovery and accumulate strain between passes to form a deformation zone capable of nucleating intragranular pro-eutectoid cementite.

Here, the reason why the area reduction rate before and after cooling is 10% or more is that if the area reduction rate is less than 10%, the accumulated strain amount is small and a sufficient deformation zone is not formed in the austenite grains. is there. Moreover, the temperature after cooling is set to Ms point to 700.
The reason why the temperature is set to 0 ° C is that if the temperature after cooling exceeds 700 ° C, prevention of deformation band disappearance due to release of processing strain is insufficient, while if it is less than the Ms point, a martensite structure occurs. Since the effect of preventing the deformation band disappearance becomes particularly remarkable by cooling to below 600 ° C, it is desirable to set the temperature after cooling to the Ms point or higher and lower than 600 ° C if possible.

Further, in the present invention, in the temperature range of less than 880 ° C., “after the rolling with a surface reduction rate of 10% or more, immediately cooling the steel material temperature so that the temperature of the steel material once becomes Ms point to 700 ° C., and subsequently the surface reduction rate is reduced. It is possible to perform arbitrary rolling before and after the step of "rolling 10% or more", and when repeating this step twice or more, it can be performed continuously or with any rolling in between. good.

Further, the temperature of the steel material on the delivery side of the final rolling is set to 700.
The reason why the temperature is set in the range of ˜880 ° C. is that the rolling load remarkably increases at the final rolling outlet temperature of less than 700 ° C.,
Further, if the final rolling outlet temperature exceeds 880 ° C., there is a risk that the austenite grains immediately after rolling may grow and become coarse.

Next, in the invention of claim 1, the steel material is quenched immediately after the final rolling so as to bring the temperature of the steel material to the final quenching temperature of 550 to 700 ° C., and in the invention of claim 2, immediately after the final rolling, 550 to 550. Quenching in a molten salt held at a molten salt temperature of 700 ° C. and holding the molten salt in the molten salt for 0.5 to 30 seconds is the formation of reticulated pro-eutectoid cementite at grain boundaries.
This is to suppress growth. In the invention of claim 1, the quenching temperature range is set to 550 to 700 ° C. The reason is that the generation and growth of reticulated pro-eutectoid cementite is insufficiently controlled at a temperature higher than 700 ° C. and the risk of bainite structure being generated at a temperature lower than 550 ° C. Because there is. 550 to 700 after the final rolling
The rapid cooling rate to 0 ° C is preferably 10 ° C / s or more.

Next, the temperature of the molten salt to be quenched in the invention of claim 2 is set to 550 to 700 ° C. because the molten salt temperature is 70.
This is because if the temperature exceeds 0 ° C, the formation and growth of reticulated pro-eutectoid cementite are not sufficiently suppressed, and if the molten salt temperature is lower than 550 ° C, a bainite structure may be generated. Further, the retention time in the molten salt was set to 0.5 to 30 seconds because
This is because if it is less than 5 seconds, there is a risk that the central portion of the steel material cross section cannot be sufficiently cooled, and if it exceeds 30 seconds, the productivity is reduced.

Then, "after that, the temperature up to 450 ° C.
The reason why “cooling is performed at a cooling rate of 1.0 ° C./sec” is to coarsen the lamellar spacing of the pearlite formed in the austenite grains. Cooling rate in this temperature range is 1.0 ° C /
If it exceeds 2 seconds, the lamellar spacing of pearlite becomes remarkably fine, while if it is less than 0.05 ° C / second, the effect of slow cooling is saturated,
It takes time for mischief, so the cooling rate is 0.05-
The rate was 1.0 ° C./second. Here, in order to obtain a more uniform spheroidal carbide structure after spheroidizing annealing, the cooling rate in this temperature range is preferably 0.4 ° C./sec or less. Any cooling rate can be selected for cooling at 500 ° C. or lower. As a method for adjusting cooling, a method such as attaching a slow cooling cover can be considered.

The structure obtained after rolling is essentially composed of proeutectoid cementite and pearlite.
This is because if the structure contains bainite and martensite, these parts become a fine spherical carbide structure after spheroidizing annealing, and a uniform spherical carbide structure cannot be obtained.

Next, the invention of claim 3 relates to a method of manufacturing a bearing steel material for obtaining a more uniform spheroidizing annealed structure after spheroidizing annealing. In the hot rolling according to the invention of claim 3, the heating rate of 650 to 750 ° C. is 1
0 to 100 ° C./hour means that the carbide is further stabilized in the austenite by gradually heating in the temperature range immediately below the A ₁ point in the temperature rising process, and the residual amount of the fine carbide during rolling heating is increased. This is to increase the amount and reduce the net amount of dissolved carbon. However, the heating rate of 650 to 750 ° C. is 100
This effect is small when the temperature exceeds ℃ / hour, while the effect of gradual heating is saturated when the temperature is lower than 10 ℃ / hour, and time is consumed unnecessarily, so the heating rate was set to 10 to 100 ℃ / hour.

In order to obtain an even more uniform spheroidal carbide structure after spheroidizing annealing, the steel for bearings manufactured by the manufacturing method of the present invention has a former austenite grain size of 9 or more in the structure after rolling. It is desirable to use a certain bearing steel material. This is because by setting the former austenite grain size of the structure after rolling to No. 9 or more, the austenite grain size during spheroidizing annealing heat retention is refined, and the uniformity of carbides after spheroidizing annealing can be further increased. Because you can
This is because this effect is particularly remarkable when the number is 9 or higher. less than,
The effects of the present invention will be more specifically shown by examples.

[0040]

EXAMPLES Table 1 shows the chemical composition of the test materials. All of these were cast by continuous casting after melting in a converter. After slab rolling into a 162 mm square steel piece, it was rolled into a round bar steel under the rolling conditions shown in Table 2.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

In the method of the present invention, after rolling, controlled cooling was performed by covering the cooling floor with a slow cooling cover. Also,
50m from the above 162mm square billet for some steel types
Cut out square pieces of m square and have a thickness of 15 under the rolling conditions shown in Table 3.
rolled to mm. After rolling, these rolled materials were subjected to spheroidizing annealing.

With respect to the spheroidized annealed material, the spheroidization rate, average and maximum values of carbide diameter (circle equivalent diameter) and hardness (index of cold workability) were evaluated. The spheroidization ratio was expressed as the ratio of the number of cementites having a major axis / minor axis of 5.0 or less to the total number of cementites. Table 4 shows the evaluation results of each steel material in comparison with the present invention and comparative examples. As is clear from this, in the method of the present invention,
In each case, the spheroidization rate is 100%. Further, when the average carbide diameter is 1 μm and the maximum carbide diameter is less than 2 μm, a uniform spherical carbide structure without coarse plate-like carbide is obtained. Further, the hardness is HRB 90 or less, which is a good softening level as compared with the comparative example.

On the other hand, Comparative Examples 5 and 35 are cases in which the heating temperature during rolling exceeds the upper limit value of the range of the present invention, and Comparative Examples 6 and 36 are in the rolling in the temperature range below 880 ° C.
"After rolling with a surface reduction rate of 10% or more, the steel temperature immediately increases to M
It is a case where the step of cooling to s point to 700 ° C. and subsequently rolling at a surface reduction rate of 10% or more is not performed, and in Comparative Example 7, the cooling stop temperature of the rapid cooling immediately after the final rolling is the main value. Comparative Examples 8 and 37 are cases where the upper limit value of the range of the invention was exceeded, and Comparative Examples 8 and 37 were cases where the cooling rate was higher than the upper limit value of the range of the present invention up to 450 ° C. immediately after rolling, and both were spherical. The degree of softening is 70% or less, the sizes of spheroidized carbides are not uniform, and the degree of softening is not sufficient.

Next, with respect to the steel materials produced in the invention examples 3, 4, 34 and comparative example 5 in Table 4, the diameter is 12 mmφ and the length is 2 mm.
2mm Cylindrical rolling fatigue test piece was prepared, and after heat treatment,
Hertz maximum contact stress 60 by point contact type rolling contact fatigue tester
A rolling fatigue test was performed at 0 kgf / mm ² . As a measure of the fatigue life, usually, "stress repetition of the test results to fatigue failure in a cumulative failure probability of 10% obtained by plotting the Weibull probability paper" is used as the L ₁₀ life. As compared with the L ₁₀ life of Comparative Example 5, the L ₁₀ life of Invention Example was 1.5 times in Invention Example 3, 1.8 times in Invention Example 4, and Invention Example 34.
The life is improved by 1.5 times.

[0049]

As described above, by using the method of the present invention, it is possible to obtain a uniform spheroidized structure that does not contain coarse plate-shaped carbides by ordinary spheroidizing annealing, and cut after annealing, It is possible to manufacture bearing steels that have excellent cold workability such as cold forging and cutting, and can also obtain excellent rolling fatigue characteristics in bearing parts that have been subjected to quenching and tempering treatment, and the industrial effect is extremely There is something remarkable.

Claims (5)

[Claims] 1. A weight ratio of C: 0.80 to 1.20%, Si: 0.15 to 1.50.
%, Mn: 0.15 to 1.50%, Cr: 0.50 to 1.6
0%, S: 0.003 to 0.02%. Al: 0.015
.About.0.05%, N: 0.004 to 0.015%, P: 0.020% or less, Ti: 0.0020% or less,
O: When the steel having a balance of iron and inevitable impurities is restricted to 0.0015% or less, A) a step of heating to a heating temperature of 900 to 1150 ° C., and B) the heating temperature to 880 Total area reduction of 5 in the temperature range above ℃
0% or more rolling, C) after that, in a temperature range of less than 880 ℃ ~ 400 ℃,
"After rolling with a surface reduction rate of 10% or more, the steel temperature immediately increases to M
The temperature of the steel material on the outgoing side of the final rolling is 700 to 880, and the temperature is 700 to 880.
A step of setting the final rolling outlet temperature to ℃, and D) quenching immediately after the final rolling to raise the temperature of the steel material to 550
To 700 ° C. for the final rolling quenching temperature, and E) thereafter cooling up to 450 ° C. at a cooling rate of 0.05 to 1.0 ° C./sec. And a method for producing a bearing steel material having excellent spheroidizing annealing characteristics, which is composed of pearlite. 2. D) and E) of claim 1 are: D) Immediately after the final rolling, quenching is performed in a molten salt maintained at a molten salt temperature of 550 to 700 ° C., and 0.5 is applied in the molten salt.
Holding for ~ 30 seconds, and E) thereafter cooling up to 450 ° C at a cooling rate of 0.05-1.0 ° C / sec.
A method for producing a bearing steel material having a spheroidizing annealing property, the structure of which is substantially composed of proeutectoid cementite and pearlite. 3. Heating of hot rolling, 650-750
The method for producing a bearing steel material having excellent spheroidizing annealing properties according to claim 1 or 2, wherein the heating rate at 10 ° C is 10 to 100 ° C / hour. 4. The composition further comprises Ni: 0.50 to 2.00%, Mo: 0.05 to 0.50.
%, 1 type or 2 types are contained, The manufacturing method of the steel material for bearings excellent in the spheroidization annealing characteristic of Claim 1 or 2 or 3. 5. The composition according to claim 1, 2 or 3 or 4, further comprising one or two of Nb: 0.01 to 0.3% and V: 0.03 to 0.3%. A method for manufacturing a bearing steel material having excellent spheroidizing annealing characteristics.