1
DESCRIPTION
BEARING STEEL AND METHOD FOR PRODUCING SAME
5 Technical Field [0001]
The present invention relates to a bearing steel in which an influence of harmful inclusions such as aluminum oxides, titanium nitrides, and manganese sulfides is suppressed by controlling formation of complex oxysulfides inchiding REM (Rare Earth 10 Metal) and which has excellent fatigue properties, and a method for producing the same. Priority is claimed on Japanese Patent Application No. 2011-230832, filed on October 20, 2011, and the contents of which are incorporated herein by reference.
Background Ail
15 [0002]
Bearing steel is used in a rolling bearing such as a "ball bearing" or a "roller bearing" which is used in various industrial machines or vehicles. In addition, in recent years, for example, the bearing steel has also been used in a bearing for a disk drive or the like used in a hard disk device which is a magnetic recording medium. In addition, 20 the bearing steel is also used in a bearing for an electronic device, a household electric appliance, a measuring instrument, a medical instrument, or the like. [0003]
It is required for the bearing steel used in the bearings to be excellent in rolling fatigue properties. When the bearing steel includes coarse inclusions and a large 25 number of inclusions, fatigue life is negatively influenced. Accordingly, it is desirable

2 that the inclusions are as fine as possible and a number of the inclusions is as small as
possible in order to improve the fatigue properties.
[0004]
Oxides such as ahmiina (AI2O3), sulfides such as manganese sulfides (MnS),
5 nitrides such as titanium nitrides (TiN), or the like is known as harmfiil inclusions
included in the bearing steel.
[0005]
A large amount of dissolved oxygen is included in molten steel made in a
converter or a vacuum processing chamber. Alumina inclusions are formed by
10 combining the dissolved oxygen and AI having high affinity for the oxygen.
[0006]
In addition, a ladle or the like used in steel-making process is often constructed
by using an alumina-based refractory. Accordingly, even when the molten steel is
deoxidized by using Si or Mn instead of Al, Al is dissolved in the molten steel due to
15 reaction between the molten steel and the above refractory, the dissolved Al is reoxidized,
and thereby, the alumina is formed in the molten steel. The alumina inclusions are hard
and form a coarse alumina cluster by being agglomerated and combined, which causes a
deterioration of the fatigue properties.
[0007]
20 For decreasing and removing the alumina inclusions, the deoxidization products
are mainly decreased by applying a secondary refining apparatus such as a RH
(Ruhrstahl-Hausen) vacuum degassing apparatus or a powder injection apparatus. In
addition, reoxidization Is suppressed by shielding air or reforming slag, the oxides are
prevented from mixing by slag cut, and a combination thereof is conducted for a decrease
25 in the inclusions.

3 [0008]
For example, a following producing method is known. In the producing
method, when an Al-killed steel containing 0.005 mass% or more of Al is produced, the
alumina in the fomied inclusions is controlled to be in a range of 30 mass% to 85 mass%
5 by adding alloy consisting of Al and at least two selected from Ca, Mg, and REM (Rare
Earth Metal) into molten steel.
[0009]
Patent Document 1 discloses technology of controlling the formed inclusions to
be complex inclusions whose melting point is low by adding at least two selected from
10 REM, Mg, and Ca to molten steel in order prevent the formation of the ahmiina cluster.
Although the teclinology may be effective in preventing sliver defects, it is difficult to
refine the size of the harmfol inclusions to the required level for the bearing steel. This
is because the inclusions are further coarsened by being agglomerated and combined
when the inclusions are controlled to be the inclusions whose mehing point is low.
15 [0010]
In a case where REM is added, since REM makes the inclusions spheroidal, an
effect in improving the fatigue properties is obtained. Although REM is added as
necessary in order to control morphology of the inclusions as described above, addition
of more than 0.010 mass% of REM results in an increase in the inclusions and a decrease
20 in the fatigue life. For example. Patent Document 2 discloses the necessity to control
REM content to be 0.010 mass% or less. However, Patent Document 2 does not
disclose the mechanism or a composition and an existence condition of the inclusions.
[0011]
The shape of sulfides such as MnS is elongated by plastic deformation such as
25 forging. Tiuis, when repeated stress is applied, the sulfides accumulate the fatigue and

4 act as a fracture origin, and thereby, the fatigue properties deteriorate. Accordingly, it is
necessary to control the sulfides in order to improve the fatigue properties.
[0012]
As a method of suppressing the foi-mation of the sulfides, a method of
5 desulfurization using Ca is known. However, AI-Ca-0 complex oxides which are
formed by adding Ca have problems such that the shape thereof tends to be elongated by
the plastic deformation and that the complex oxides accumulate the fatigue and act as the
fracture origin when the repeated stress is applied. In addition, the utilization of Ca is
not effective in TiN.
10 [0013]
Since the nitrides such as TiN are extremely hard and are precipitated with a
sharp shape, the nitrides accumulate the fatigue and act as the fracture origin, and thereby,
the fatigue properties deteriorate. For example. Patent Document 3 discloses that, when
Ti is added exceeding 0.001 mass%, the fatigue properties deteriorate.
15 [0014]
In order to suppress the formation of TiN, it is important to control Ti content to
be 0.001 mass% or less. However, since Ti is also included in molten iron or slag, it is
difficult to stably reduce the content. Thus, it is necessary to effectively remove Ti and
N in the molten steel, but the production cost of the steei unpreferably increases.
20 [0015]
As described above, the technology of controlling the harmffil inclusions such as
AI2O3, Al-Ca-0 complex oxides, MnS, and TiN in order to improve the fatigue properties
required as the bearing steel is not found at present.
25 Related Ait Documents

Patent Documents
[0016]
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. H09-263820
5 [Patent Document 2] Japanese Unexamined Patent Application, First
Publication No. HI 1-279695
[Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2004-277777
10 Summary of Invention
Technical Problem to be Solved [0017]
An object of an embodiment of the present invention is to provide a bearing steel in which the above problems in the related art are solved and which has excellent 15 fatigue properties, and a method for producing the same.
Solution to Problem [0018]
As a result of experiments and studies in order to solve the above problems in 20 the related art, the present inventors have found that, in order.to control the formation and the morphology of the above harmful inclusions, it is possible to form complex inclusions including REM, Ca, O, S, and Al (hereinafter, referred to as REM-Ca-Al-0-S complex oxysulfides) in a metallographic structure of the bearing steel by adjusting each amount of cliemical compositions such as REM, Al, and Ca and by controlling a 25 deoxidization method and a method for producing the bearing steei.

6 [0019]
Since AI2O3 and Al-Ca-0 complex oxides are transformed into the
REM-Ca-Al-O-S complex oxysulfides, it is possible to suppress the formation of coarse
alumina cluster and to prevent the above complex oxides from being elongated and
5 coarsened due to plastic deformation. Moreover, since the REM-Ca-Al-0-S complex
oxysulfides fix S in the steel, it is possible to suppress the formation of coarse MnS.
Furthermore, since TIN complexly precipitates on a surface of the REM-Ca-Al-0-S
complex oxysulfides, it is possible to decrease a number of TiN existing independently.
■ [0020]
10 An aspect of the present invention employs the following.
(1) A bearing steel according to an aspect of the invention includes, as a
chemical composition, by mass %, C: 0.9% to 1.5%, Si: 0.1% to 0.8%, Mn: 0.1% to
1.5%, Cr: 0.5% to 2.0%, Al: 0.01% to 0.05%, Ca: 0.00001% to 0.0050%, Rare Earth
Metal: 0.0001% to 0.050%, O: 0.0001% to 0.0030%, Ti: limited to less than 0.005%, N:
15 limited to 0.015% or less, P: limited to 0.03% or less, S: limited to 0.05% or less, and a balance consisting of Fe and unavoidable impurities, and includes, as a metallographic structure, inclusions which contain complex oxysulfides including Rare Earth Metal, Ca, O, S, and Al, TiN, MnS, AI2O3, and complex oxides including Ai and Ca, wherein, a number fraction of the complex oxysulfides in a total iiuniber of the inclusions is 50% to
20 less than 100% and a number of complex oxysulfides having a major axis of 5 [.un or
T
more is 0.001 pieces to 2 pieces m an observed section of 1 mm , and a number of TiN existing independently from the complex oxysulfides and having a major axis of 5 (.an or more is 0.001 .pieces to less than 1.0 piece in the observed section of 1 mm^.
(2) In the bearing steel according to (1), when the S content in the chemical
25 composition is iiiore than 0.01% to 0.05%, the Ca content may be 0.00050% to 0.0050%.

7 (3) The bearing steel according to (1) or (2) may further include, as the chemical
composition, by mass %, at least one of V: 0.05% to 0.70%, Mo: 0.05% to 1.00%, W:
0.05% to 1.00%, Ni: 0.10% to 3.50%, Cu: 0.10% to 0.50%, Nb: 0.005% to less than
0.050%, and B: 0.0005% to 0.0050%.
5 (4) In the bearing steel according to any one of (1) to (3), an Al content in the
complex oxysulfides may be 20 mass% or less in AI2O3 equivalent.
(5) In the bearing steel according to any one of (1) to (4), a total number of MnS
having a major axis of 10 |.UTI or more and the TIN existing independently from the
complex oxysulfides and having the major axis of 5 jam or more may be 5 pieces or less
10 in the obsei-ved section of 1 mm^.
(6) In the bearing steel according to any one of (1) to (5), the Cu content and the Ni content expressed in mass% may satisfy Cu < Ni.
(7) A method for producing a bearing steel according to an aspect of the invention includes: Al-deoxidizing a molten steel using Al; REM-deoxidizing the molten
15 steel using Rare Earth Metal after the Al-deoxidizing for 5 minutes to 10 minutes; casting the molten steel after the REM-deoxidizing so as to obtain a cast piece which includes, as a chemical composition, by mass %, C: 0.9% to 1.5%, Si: 0.1% to 0.8%, Mn: 0.1% to 1.5%, Cr: 0.5% to 2.0%, Al: 0.01% to 0.05%, Ca: 0.00001% to 0.0050%, Rare Earth Metal: 0.0001% to 0.050%, 0: 0.0001% to 0.0030%, Ti: limited to less than 0.005%, N:
20 limited to 0.015% or less, P: limited to 0.03% or less, S: limited to 0.05% or less, and a balance consisting of Fe and unavoidable impurities; heating the cast piece in a temperature range of 1270°C to 1300°C and holding the cast piece after the heating in a temperature range of 1200°C to 1250°C for 60 seconds or more; and hot-plastic-working the cast piece after the heating and the holding so as to obtain a hot-worked steel.
25 (8) The method for producing the bearing steel according to (7) may finlher

include vacuum-degassing the molten steel using Ca after the REM-deoxidizing and before the casting, when the molten steel includes, as a chemical composition, by mass %, S: more than 0.01% to 0.05%.
(9) In the method for producing the bearing steel according to (7) or (8), the cast
5 piece may further include, as the chemical composition, by mass %, at least one of V:
0.05% to 0.70%, Mo: 0.05% to 1.00%, W: 0.05% to 1.00%, Ni: 0.10% to 3.50%, Cu: 0.10% to 0.50%, Nb: 0.005% to less than 0.050%, and B: 0.0005% to 0.0050%.
(10) In the method for producing the bearing steel according to any one of (7) to
(9), in the casting, the molten steel may be cast while being rotated horizontally in a mold
10 under a condition of 0.1 m/minute to 0.5 m/minute.
(11) The method for producing the bearing steel according to any one of (7) to
(10) may further include soft-annealing the hot-worked steel after the hot-plastic-working
by being heated in a temperature range of 700°C to 750°C and held for 30 hours to 50
hours so as to obtain a softened steel.
15 (12) The method for producing the bearing steel according to any one of (7) to
(11) may further include fluxing the molten steel using CaO-CaF2 for a desulfurization
after the REM-deoxidizing and before the vacuum-degassing.
Effects of Invention
20 [0021]
According to the above aspects of the bearing steel and the method for producing the same, since AI2O3 and Al-Ca-0 complex oxides are transformed into the REM-Ca-Al-0-S complex oxysulfides, it is possible to suppress the formation of coarse alumina cluster and to prevent the complex oxides from being elongated and coarsened.
25 Moreover, since the REM-Ca-Al-0-S complex oxysulfides fix S, it is possible to

9 suppress the formation of coarse MnS. Furthennore, since the REM-Ca-Al-0-S
complex oxysulfides complexly involve TiN, it is possible to decrease a number of TiN
existing independently. As a result, it is possible to solve the above problems.
5 Brief Description of Drawings [0022]
FIG. 1 is a metallographic micrograph of bearing steel according to an embodiment of the present invention.
FIG. 2 is a metallographic micrograph of bearing steel according to a related ait.
10 FIG. 3 is a relationship between fatigue properties of a bearing steel and a total
number of MnS having a major axis of 10 |.im or more and TiN existing independently from REM-Ca-Al-0-S complex oxysulfides and having a major axis of 5 |im or more.
Detailed Description of Preferred Embodiments
15 [0023]
Hereinafter, a preferable embodiment of the present invention will be described in detail.
[0024]
First, limitation range and reasons for the limitation of base elements of the 20 bearing steel according to an embodiment of the present invention will be described in detail. Herein, the described % is mass%. [0025]
Al: 0.01% to 0.05%
Al"(aluminum) is a deoxidizing element and an element which is required to 25 form REM-Ca-Al-O-S complex oxysulfides. In order to obtain the effects, the Al

10 content needs to be 0.01% or more. However, when the Al content is more than 0.05%,
AI2O3 and Ai-Ca-0 complex oxides do not transform into the REM-Ca-Al-0-S complex
oxysulfides. The reason for the above seems that, when the Al content is more than
0.05%, the state of the AI2O3 and the Al-Ca-0 complex oxides is more stable than that of
5 the REM-Ca-Al-0-S complex oxysulfides.
[0026]
AI2O3 is a hard oxide, and AI2O3 not only causes deterioration of fatigue
properties but also drastically deteriorates durability of a refractory during casting.
During continuous casting, the hard oxides adhere to nozzles, and thereby, may cause .
10 nozzle blockage. Although the Al-Ca-O complex oxides are not as hard as AI2O3, the
size of the Al-Ca-0 complex oxides is generally larger tlian that of AI2O3, and thereby,
cause the deterioration of the fatigue properties. Accordingly, the upper limit of the Al
content should be 0.05%.
[0027]
15 REM: 0.0001% to 0.050%
REM (Rare Earth Metai) is a strong desulflirizing and deoxidizing element and
is a significantly important element in order to obtain the sufficient effect of the aspect of
the present invention. Here, REM represents collectively a total of 17 elements which
are 15 elements from lanthanum with atomic number 57 to lutetium with atomic nimiber
20 71 in addition to scandium with atomic number 21 and j'ttrium with atomic number 39.
[0028]
When the REM content is less than 0.0001%, AI2O3 and the Ai-Ca-0 complex
oxides which are not transformed into the REM-Ca-Al-O-S complex oxysulfides increase.
Thus, coarse MnS is formed by S which is not combined with the REM-Ca-Ai-0-S
25 complex oxysulfides, and TiN increases which exists independently and which does not

11
precipitate on a surface of the REM-Ca-Al-0-S complex oxysulfides.
[0029]
When the REM content is more than 0.050%, a production cost increases, and productivity deteriorates because the nozzle blockage tends to occur during casting due 5 to the formed REM-containing inclusions. Accordingly, the REM content should be 0.0001% to 0.050%. It is more preferable tliat the REM content is 0.0003% to 0.050%. It is still more preferable that the REM content is more than 0.001% to 0.050%. It is most preferable that the REM content is more than 0.003% to 0.050%.
[0030]
10 C: 0.9% to 1.5%
C (carbon) is an element which improves the fatigue life by ensuring hardness in quenching and which enhances strength due to dispersion of spheroidal carbides and martensitic transformation of matrix. In order to obtain the effects, the C content needs to be 0.9% or more. However, when the C content is more than 1.5%, aUhough wear 15 resistance is enhanced, tool life decreases during cutting because the hardness of a base material excessively increases, and cracks may occur during quenching. Thus, the C content should be 0.9% to 1.5%. It is preferable that the lower limit of the C content is 1.0% and the upper limit thereof is 1.2%.
[0031]
20 Si: 0.1% to 0.8%
Si (silicon) is an element which increases hardenability and which improves the fatigue life. In order to obtain the effects, the Si content needs to be 0.1% or more. However, when the Si content is more than 0.8%, the above effects are saturated, the tool life decreases during cutting because the hardness of the base material increases, and the 25 cracks may occur during quenching. Tlius, the Si content should be 0.1% to 0.8%. It

12 is preferable that the lower limit of the Si content is 0.15% and the upper limit thereof is
0.7%.
[0032]
Mn: 0.1% to 1.5%
5 Mn (manganese) is an element which increases the strength by increasing the
hardenability and improves the fatigue life. In order to obtain the effects, the Mn
content needs to be 0.1% or more. However, when the Mn content is more than 1.5%,
the effect in increasing the hardenability is saturated. Moreover, the tool life decreases
during cutting because the hardness of the base material increases and the cracks may
10 occur during quenching. Thus, the Mn content should be 0.1% to 1.5%. It is
preferable that the lower limit of the Mn content is 0.2% and the upper limit thereof is
1.15%. It is most preferable that the lower limit of the Mn content is more than 0.5%
and the upper limit thereof is 1.15%.
[0033]
15 Cr: 0.5% to 2.0%
Cr (chromium) is an element which increases the hardenability and improves the
fatigue life. In order to obtain the effects, the Cr content needs to be 0.5% or more.
However, when the Cr content is more than 2.0%, the above effects are saturated.
Moreover, the tool life decreases during cutting because the hardness of the base material
20 increases and the cracks may occur during quenching. Thus, the Cr content should be
0.5% to 2.0%. It is preferable that the lower Umit of the Cr content is 0.9% and the
upper limit thereof is 1.6%. It is most preferable that the lower limit of the Cr content is
more than 1.0% and the upper limit thereof is less than 1.6%.
[0034]
25 Ca: 0.00001% to 0.0050%

13 Ca (calcium) is a deoxidizing and desulfurizing element. Ca has a fiinction of
softening oxides. It is known that, when Ca is added to free cutting steel, an oxide film
called Belag is formed due to cutting heat during the cutting, the film covers and protects
the surface of a tool, and thereby, the life of the cutting tool is prolonged.
5 [0035]
Moreover, Ca is an element which is required to form the REM-Ca-Al-0-S
complex oxysulfides. Since the REM-Ca-Ai-0-S complex oxysulfides fix S, the
formation of the coarse MnS is suppressed. However, when the Ca content is less than
0.00001%, the REM-Ca-Ai-0-S complex oxysulfides are not formed, but REM-Ai-0-S
10 complex oxysulfides which do not include Ca are formed.
[0036]
The REM-Al-0-S complex oxysulfides which do not include Ca have a small effect in fixing S. In order to enhance the effect in fixing S, it is necessary to form 15 REM-Ca-Al-O-S complex oxysulfides including Ca and REM. Thus, the Ca content needs to be 0.00001% or more. It is preferable that the lower limit of the Ca content is 0.00010%. It is more preferable that the lower limit of the Ca content is 0.00050%. In order to detect the Ca content which is a level of 0.00001% in the steel, high sensitivity element spectrometry such as ICP-AES (inductively coupled plasma-atomic emission 20 spectrometry), ICP-MS (inductively coupled plasma-mass spectrometry), or the like may be used as necessary. [0037]
In general, even when Ca is not puiposely added, steel unavoidably contains approximately 0.0001% of Ca. The above mentioned Ca which is unavoidably 25 contained also has an eftect in forming the REM-Ca-Al-O-S complex oxysulfides.

14 Accordingly, in a case where Ca unavoidably contained in the steel is 0.00001% or more,
Ca may not be purposely added thereto. The REM-Ca-Al-0-S complex oxysulfides
which are formed using Ca unavoidably contained in the steel have the effect in fixing S.
[0038]
5 Since the number of inclusions wliich is observed in a polished surface of the
bearing steel which is basically cleanliness steel is small, it is possible to directly analyze
the composition of the inclusions (REM-Ca-Al-0-S complex oxysulfides, AI2O3,
Al-Ca-0 complex oxides, MnS, TiN, or the like) by using a scanning electron
microscope (SEM) provided with EPMA (electron probe micro analysis) or EDX (energy
10 dispersive X-Ray analysis). In otlier words, it is possible to confirm the formation of the REM-Ca-A!-0-S complex oxysulfides because existence of Alj Ca, or S in the inclusions is analyzed for each of the inclusions by using an X-ray signal when an electron beam is applied thereto. Moreover, it is possible to semi-quantitatively calculate the composition from the signal intensity. In addition, the composition may be
15 directly analyzed by using TEM (Transmission Electron Microscope) provided with EDX or the like as necessary. Tlie present inventors have used various raw materials (cast piece) including a high purity raw material in which the Ca content is less than 0.00001% and have investigated the lower limit of Ca for forming the REM-Ca-Al-0-S complex oxysulfides by using the above analysis method. As a result, it has been found that,
20 when the Ca content in the steel (cast piece) is 0.00001% or more, the REM-Ca-Al-0-S complex oxysulfides are formed as inclusions instead of the REM-Ai-0-S complex oxysulfides which do not include Ca as described above. [0039] In order to increase the effect in fixing S in respect to the REM-Ca-Al-0-S
25 complex oxysulfides, it is preferable to purposely add Ca to the steel. For example, it is

15 preferable to purposely add Ca to the steel in a case where S content is high and the
effect in fixing S in respect to the REM-Ca-Al-O-S complex oxysulfides should be
fiirther increased. Specifically, when the S content is more than 0.01% to 0.05%, it is
preferable to purposely add Ca to the steel so that the Ca content is 0.00050% to
5 0.0050%. As a result, even when the S content is high such as more than 0.01% to
0.05%, the effect in fixing S in respect to the REM-Ca-Al-0-S complex oxysulfides is
sufficiently increased, and the precipitation of MnS is sufficiently suppressed.
[0040]
When the Ca content is more than 0.0050%, the Al-Ca-O complex oxides and
10 CaO which are coarse oxides are excessively formed, and thereby, the fatigue life is
shortened. In particular, the size of the Al-Ca-0 complex oxides obtained by
complexing Ca with AI2O3 is generally larger than that of AI2O3, and thereby, the
Al-Ca-0 complex oxides cause the deterioration of the fatigue properties. Therefore,
the upper limit of the Ca content should be 0.0050% or less. In addition, Ca is
15 solid-soluted in the REM-Ca-Al-0-S complex oxysulfides and CaS does not
independently exist.
[0041]
0:0.0001% to 0.0030%
Although O (oxygen) is an element which should be removed from the steel
20 through the deoxidization, 0 is an element which is required to precipitate the
REM-Ca-Al-0-S complex oxysulfides. In order to obtain the effect, the O content
needs to be 0.0001% or more. Mowever, when the 0 content is more than 0.0030%,
oxides excessively remain, and thereby the fatigue life deteriorates. Therefore, the
upper limit of the O content should be 0.0030% or less. In addition, the above 0
25 content indicates the total oxygen (TO) whose content is the amount of the solid-soluted

16 oxygen in the steel and the oxygen included in the REM-Ca-Al-0-S complex oxysulfides,
AI2O3 or the like.
[0042]
The bearing steel according to the embodiment includes unavoidable impurities
5 in addition to the above described base elements. Herein, the unavoidable impurities
indicate elements such as Ti, N, P, S, Mg, Pb, Sb, Sn, Cd, or the like which are
unavoidably mixed from auxiliary materials such as scrap or from producing processes.
In the elements, Ti, N, P, and S are limited to the following in order to sufficiently obtain
the effects of the aspect of the present invention. Herein, the described % is mass%.
10 In addition, although the limitation range of the impurities includes 0%, it is industrially
difficult for the level of impurities to stably be 0%.
[0043]
Ti: less than 0.005%
Ti (titanium) is an impurity and an element which forms fine inclusions such as
15 Tic, TiN, and TiS and which deteriorates the fatigue properties. In particular, since TiN
is precipitated in an angular shape, stress tends to be concentrated at TiN, and thereby, to
act as the fracture origin when the repeated stress is applied. Accordingly, it is
significantly important to suppress the amount of TiN precipitated in the angular shape.
[0044]
20 In a case where the REM-Ca-Al-0-S complex oxysulfldes exist in the
metallographic structure, TiN complexly precipitates on the REM-Ca-Al-0-S complex
oxysulfldes which act as preferential nucleation sites. Thus, the REM-Ca-Al-0-S
complex oxysulfldes become REM-Ca-Al-0-S-TiN complex oxysulfide having an
approximately spherical shape as shown in FIG 1. As a result, independent
25 precipitation of TiN, which is hard and has the sharp and angular shape as shown B in

17 FIG.2, is suppressed. The metallographic structure will be described in detail later.
[0045]
It is necessary to limit the Ti content to be less than 0.005% in order to
complexly precipitate TiN on the REM-Ca-Ai-0-S complex oxysulfides and to decrease
5 the amount of TiN precipitates existing independently. In the related art, it is necessary
to limit the Ti content to be 0.001% or less in order to suppress the deterioration of the
fatigue properties due to TiN. However, in the aspect of the present invention, in so far
as the Ti content is less than 0.005%, the acceptable fatigue properties are obtained by
the effect of the REM-Ca-Al-0-S complex oxysulfides even when Ti content more than
10 the level in the related art is included. As described above, it is possible to produce the
bearing steel which stably shows the excellent fatigue properties in so far as the Ti
content is limited to less than 0.005%.
[0046]
Since it is preferable that the Ti content is as small as possible in order to
15 decrease the amount of TiN precipitates, the limitation range includes 0%. However, it
is not easy to technically control the Ti content to be 0%., and the production cost of the
steel increases in order to stably control the Ti content to be 0.0002% or less. Therefore,
it is preferable that the limitation range of the Ti content is more than 0.0002% to less
than 0.005%. For the production cost, it is more preferable that the limitation range of
20 the Ti content is more than 0.001% to less than 0.005%. Generally, in ordinary
producing condition, approximately 0.003%i of Ti is unavoidably contained.
[0047]
N: 0.015% or less
N (nitrogen) is an impurity and an element which deteriorates the fatigue
25 properties by forming nitrides and which negatively influence ductility and toughness

18 due to strain aging. When the N content is more than 0.015%, the above harmful
influence is unacceptable. Therefore, the N content is limited to 0.015% or less.
[0048]
Since it is preferable that the N content is as small as possible in order to
5 decrease the amount of nitrides, the limitation range includes 0%. However, it is not
easy to technically control the N content to be 0%, and the production cost of the steel
increases in order to stably control the N content to be less than 0.0008%. Therefore, it
is preferable that the limitation range of the N content is 0.0008% to 0.015%. It is more
preferable that the limitation range of the N content is 0.0008% to 0.010%.
10 [0049]
P:. 0.03% or less
P (phosphorus) is an impurit}', and an element which segregates to grain
boundaries and which shortens the fatigue life. When the P content is more than 0.03%,
the decrease in the fatigue lite is unacceptable. Accordingly, the P content is limited to
15 0.03% or less.
[0050]
Since it is preferable that the P content is as small as possible in order to
suppress the decrease in the fatigue life, the limitation range includes 0%. However, it
is not easy to teclinically control the P content to be 0%, and the production cost of the
20 steel increases in order to stably control the P content to be less than 0.0005%.
Therefore, it is preferable that the limitation range of the P content is 0.0005% to 0.03%.
It is more preferable that the limitation range of tiie P content is 0.0005% to 0.02%.
[0051]
S: 0.05% or less
25 S (sulfur) is an impurity, and an element which forms sulfides. When the S

19 content is more than 0.05%/the effect in fixing S obtained by REM and Ca included in
the REM-Ca-Al-0-S complex oxysulfides is insufficient, coarse MnS as shown by D in
FIG. 2 is formed, and thereby, the fatigue life deteriorates. Therefore, the S content
needs to be limited to 0.05% or less.
5 [0052]
Since it is preferable that the S content is as small as possible in order to
suppress the precipitation of MnS, the limitation range includes 0%. However, it is not
easy to technically control the S content to be 0%, and the production cost of the steel
increases in order to stably control the S content to be 0.0003% or less. Therefore, it is
10 preferable that the limitation range of the S content is more than 0.0003% to 0.05%. In addition, since S has a function of increasing machinability, tlie machinability is improved when the S content is 0.005% or more. Thus, in a case where the machinability is regarded as important, tlie limitation range of the S content may be 0.005% to 0.05%.
15 [0053]
When the S content is 0.05% or less and the Ca content which is unavoidably contained is 0.00001% or more, it is possible to suppress tlie amount of MnS precipitates within an acceptable range by the effect in fixing S derived from the REM-Ca-Al-0-S complex oxysulfides. In the case, Ca maj^ not be purposely added. However, in order
20 to further increase the effect in fixing S, it is preferable to purposely add Ca. When the S content is higher within the limitation range, specifically, when the S content is more than 0.01% to 0.05%, it is preferable that the Ca content is controlled to be 0.00050% to 0.0050% by adding Ca. As a result, it is possible to preferably increase the effect In fixing S obtained by the REM-Ca-Al-0-S complex oxysulfides and to preferably
25 suppress the precipitation of MnS.

20 [0054]
In addition, although the effect in fixing S derived from the REM-Ca-Al-0-S
complex oxysuifides is obtained by REM and Ca, REM may cause the nozzle blockage
or the like during casting, and therefore, it is difficult to add REM whose content is more
5 than the above described upper limit. Accordingly, it is preferable to control the effect
in fixing S by the Ca content.
[0055]
The above are the base elements (base components) of the steel in the
embodiment. The above base elements are included or controlled and the balance
10 consists of Fe and unavoidable impurities. However, in the embodiment, in addition to
the base elements, the following optional elements may be additionally included in the
steel instead of a part of Fe which is the balance as necessary. Moreover, even when the
optional elements whose content is less than a lower limit of each optional element are
unavoidably included in the steel, the effects in the embodiment are not decreased.
15 [0056]
Specifically, the bearing steel according to the embodiment may further include,
as an optional element, at least one selected from the group consisting of V, Mo, W, Ni,
Cu, Nb, and B. Hereinafter, limitation range and reasons for the limitation of the
optional elements will be described. Here, the described % is mass%.
20 [0057]
V: 0.05% to 0.70%
V is an element which forms carbides, nitrides, and carbon-nitrides. Addition
of V results in the formation of the fine carbides, nitrides, and carbon-nitrides of V
having an equivalent circle diameter of less than 0.2 \xm, and thereby, it is possible to
25 obtain the eftect of improving temper softening resistance, of increasing a yield point, of

21 refinmg prior-austenite, or the like. It is possible to increase the hardness and the tensile
strength by sufficient precipitation of the above precipitates resulted from increasing the
V content and prolonging the tempering time.
[0058]
5 In order to obtain the effects, it is preferable that the V content is 0.05% to
0.70%. When the V content is less than 0.05%, the above effects are not obtained. It is more preferable that the lower limit of the V content is 0.10%. Moreover, even when
V whose content is less than the lower limit is contained in the steel, the effects in the
embodiment are not decreased. Moreover, since it is not necessary to purposely add the
10 optional element to the steel in order to reduce costs of alloy, the lower limit may be 0%. [0059]
When the V content is more than 0.70%, the coarse spheroidal carbides may not be sufficiently dissolved by heating before quenching, the so-called undissolved carbides may remain, and thereby, the workability or the fatigue properties may deteriorate. In 15 addition, by adding V, a supercooled structure which causes the cracks before working or the wire breakage during wire drawing tends to be formed. Accordingly, it is preferable that the upper limit of the V content is 0.70%. In a case where a decrease in quality unevenness and an increase in production stability at producing the bearings are regarded as important, the upper limit of the V content is preferably 0.50%, and more preferably 20 0.30%.
[0060]
Mo: 0.05% to 1.00%
Mo is an element which increases the hardenability and improves the temper softening resistance. In addition. Mo is an element which forms Mo-containing 25- carbides in the steel. In order to obtain the effects, it is preferable that the Vlo content is

22 0.05% to 1.00%.
[0061]
The temperature in which the Mo-containing carbides precipitate is lower than
that of V-containing carbides or the like. The Mo-containing carbides are effective in
5 improving the above properties for the bearing steel which is tempered at a lower
temperature. Accordingly, it is preferable that the lower limit of the Mo content is
0.05%. It is more preferable that the lower limit of the Mo content is 0.10%.
Moreover, even when Mo whose content is less than the lower limit is contained in the
steel, the effects in the embodiment are not decreased. Moreover, since it is not
10 necessary to purposely add the optional element to the steel in order to reduce costs of
alloy, the lower limit may be 0%.
[0062]
When the Mo content is more than 1.00%, the supercooled structure tends to be
formed during cooling after hot rolling or cooling after heat treatment before working.
15 The supercooled structure causes season cracks or cracks during working. Therefore, it
is preferable that the upper limit of the Mo content is 1.00%. It is more preferable that
the upper limit of the Mo content is 0.50%.
[0063]
In order to decrease in quality unevenness and to increase in production stability
20 at producing the bearings, it is preferable that the upper limit of the Mo content is 0.20%..
Furthermore, in order to stabilize shape accuracy by precisely controlling the
transformation strain caused by temperature variation during cooling, it is preferable that
the upper limit of the Mo content is 0.15%.
[0064]
25 W: 0.05% to 1.00%.

23 W is an element which increases the hardenability and improves the temper
softening resistance in conmion with Mo. Moreover, W is an element which
precipitates as carbides in the steel. In order to obtain the effects, it is preferable that
the W content is 0.05% to 1.00%. It is more preferable that the lower limit of the W
5 content is 0.10%. Moreover, even when W whose content is less than the lower limit is
contained in the steel, the effects in the embodiment are not decreased. Moreover, since
it is not necessary to purposely add the optional element to the steel in order to reduce
costs of alloy, the lower limit may be 0%.
[0065]
10 On the other hand, when the W content is more than 1.00%, the supercooled
structure tends to be formed during cooling after hot roiling or cooling after heat
treatment before working in common with Mo. Accordingly, it is preferable that the
upper limit of the W content is 1.00%. It is more preferable that the upper limit of the
W content is 0.50%.
15 [0066]
In order to decrease in quality unevenness and to increase in production stability
at producing the bearings, it is preferable that the upper limit of the W content is 0.20%.
Furthermore, in order to stabilize shape accuracy by precisely controlling the
transformation strain caused by temperature variation during cooling, it is preferable that
20 the upper limit of the W content is 0.15%.
[0067]
Ni: 0.10% to 3.50%
Ni is an element which strengthens the steel. In order to obtain the effect, it is
preferable that the Ni content is 0.10% to 3.50%. When the Ni content is less than
25 0.10%, it is difficuU to obtain the above effect. Accordingly, it is preferable that the

24 lower limit of the Ni content is 0.10%. It is more preferable that the lower limit of the
Ni content is 0.20%. Moreover, even when Ni whose content is less than the lower
limit is contained in the steel, the effects in the embodiment are not decreased.
Moreover, since it is not necessary to purposely add the optional element to the steel in
5 order to reduce costs of alloy, the lower limit may be 0%.
[0068]
On the other hand, when the Ni content is more than 3.50%, a fraction of
retained austenite increases. As a result, the steel may not be hardened even if the
quenching is perfonned, and therefore, the hardness required as the bearing steel may not
10 be satisfied. In addition, in the bearings including a large amount of the retained
austenite, tlie shape accuracy of bearing products may deteriorate with the usage thereof
because the maitensitic transformation with transformation expansion occurs.
Accordingly, it is preferable that the upper limit of the Ni content is 3.50%.
[0069]
15 Since Ni is an expensive element, it is preferable that the upper limit of the Ni
content is 2.50% in order to reduce the production cost. It is more preferable that the
upper limit of the Ni content is 1.00%.
[0070]
Ni is also an element wiiicli suppresses harmful influence of Cu when Ni
20 coexists with Cu. Cu may cause a decrease in hot ductility of the steel and occurrence
of the cracks or flaws during hot rolling or hot foiging. However, when Cu and Ni are
simultaneously added, Cu and Ni form an alloy phase, and thereby, the decrease in the
hot ductility is suppressed. Therefore, it is preferable that Ni is added when Cu exists in
the steel. It is preferable that the Ni content is within the above range and that the Cu
25 and Ni contents expressed in mass% satisfy Cu < Ni.

25 [0071]
Cu: 0.10% to 0.50%
Cu is an element which improves corrosion resistance and suppresses
decarburization. In order to obtain the effects, it is preferable that the Cu content is
5 0.10% to 0.50%. When the Cu content is less than 0.10%, it is difficult to obtain the
above effects. Accordingly, it is preferable that the lower limit of the Cu content is
0.10%. It is more preferable that the lower limit of the Cu content is 0.20%.
Moreover, even when Cu whose content is less than the lower limit is contained in the
steel, the effects in the embodiment are not decreased. Moreover, since it is not
10 necessary to purposely add the optional element to the steel in order to reduce costs of
alloy, the lower limit may be 0%.
[0072]
On the other hand, when the Cu content is more than 0.50%, the hot ductility
may deteriorate, which may cause the occurrence of the cracks or the flaws in the
15 producing processes such as casting, roiling, and forging. Accordingly, it is preferable
that the upper limit of the Cu content is 0.50%. It Is more preferable that the upper limit
of the Cu content is 0.40%. In addition, as described above, it is preferable that the Cu
content is within the above range and that tlie Cu and Ni contents expressed in mass%
satisfy Cu < Ni. As a result, since the decrease in the hot ductility is suppressed, it is
20 possible to satisfactorily maintain the quality of the bearing steel.
[0073]
Nb: 0.005% to less than 0.050%
Nb is an element which bonds to C and N in the steel and forms carbides,
nitrides, and carbon it rides. Even when a small amount of Nb is added, it is possible to
25 obtain an effect in suppressing grain coarsening as compared with a case where Nb is not

26 added. Fnilhermore, in a case where Nb is added in combination with an element such
as V which forms carbides, nitrides and carbonitrides, since Nb tends to form the nitrides
as compared with V, V may not form the nitrides. As a result, it is possible to obtain an
effect in which V-containing carbides effective in refining the grain size of the austenite
5 tends to be formed. As described above, even when the small amoiuit of Nb is added, it
is possible to more effectively control the grain size of the austenite or impart the temper
softening resistance.
[0074]
In order to obtain the effects, it is preferable that the Nb content is 0.005% to
10 less than 0.050%. When the Nb content is less than 0.005%, it is difficult to obtain the
above effects. Accordingly, it is preferable that the lower limit of the Nb content is
0.005%. It is more preferable that the lower limit of the Nb content is 0.010%.
Moreover, e^'en when Nb whose content is less than the lower limit is contained in the
steel, the effects in the embodiment are not decreased. Moreover, since it is not
15 necessary to purposely add the optional element to the steel in order to reduce costs of
alloy, the lower limit may be 0%.
[0075]
On the other hand, Nb is an element which decreases the hot ductilit)^ When
the Nb content is 0.050% or more, Nb may cause the occurrence of the cracks or the
20 flaws in the producing processes such as casting, rolling, and forging, and the
productivity may excessively deteriorate.. Accordingly, it is preferable that the upper
limit of the Nb content is less than 0.050%. In a case where cold workability or
machinability is regarded as important, it is preferable that the upper limit of the Nb
content is 0.030%. It is more preferable that the upper limit of the Nb content is
25 0.020%. In a case where Nb is added in combination with elements such as V which

27 increase the hardenability and improve the temper softening resistance, the upper limit of
the Nb content may be 0.010%.
[0076]
B: 0.0005% to 0.0050%
5 B is an element which increases the hardenability of tire steel with a small
amount of addition. Moreover, B is an element which forms carbides containing B and
Fe during cooling after hot rolling, increases the growth rate of ferrite, and improves the
workabiUty of the steel, in a case where the base material is a high carbon steel.
Furthermore, by the segregation to austenite grain boundary of B itself, B suppresses the
10 grain boundary segregation of P, and improves the strength of grain boundary. As a
result, B is an element which improves grain boundary strength and which increases the
fatigue strength and impact strength.
[0077]
In order to obtain the effects, it is preferable that the B content is 0.0005% to
15 0.0050%. When tlie B content is less than 0.0005%, the effects may not be obtained.
Accordingly, it is preferable that the lower limit of the B content is 0.0005%. It is more
preferable that the lower limit of the B content is 0.0010%. Moreover, even when B
whose content is less than the lower limit is contained in the steel, the effects in the
embodiment are not decreased. Moreover, since it is not necessary to purposely add the
20 optional element to the steel in order to reduce costs of alloy, the lower limit may be 0%.
[0078]
On the other hand, when the B content is more th^n 0.0050%, tlie above effects
are saturated. In addition, the supercooled structure such as martensite or bainite tends
to be formed in the producing processes such as casting, rolling, and forging, and thereby,
25 the productivity or the impact strength of products may deteriorate. Accordingly, it is

28 preferable that the upper limit of the B content is 0.0050%. It is more preferable that
the upper limit of the B content is 0.0030%.
[0079]
Next, the metallographic structure of the bearing steel according to the
5 embodiment will be described.
[0080]
As described above, the metallographic structure of the bearing steel according
to the embodiment includes the complex oxysulfides including Rare Earth Metal, Ca, O,
S, and Al (REM-Ca-Al-0-S complex oxysulfides), AI2O3, the complex oxides including
10 Al and Ca (Al-Ca-O complex oxides), MnS, TiN, and other inclusions. In addition, TiN
preferentially precipitates on the REM-Ca-Al~0-S complex oxysulfides, and thereby,
REM-Ca-Al-0-S-TiN complex oxysulfides are formed. Here, TiN in the
REM-Ca-Al-0-S-TiN complex oxysulfides represents TiN which complexly precipitates
on the surface of the REM-Ca-Al-0-S complex oxysulfides.
15 [0081]
REM added to the steel reacts with and deoxidizes AI2O3 and Al-Ca-O complex
oxides in the steel in order to form REM oxides. Subsequently, the REM oxides react
with Ca which is unavoidably contained in the steel or Ca which is added as necessary in
order to form REM complex oxides. The REM complex oxides react with S which is
20 the impurity included in the steel in order to form REM-Ca-Al-0-S complex oxysulfides
including REM, Ca, O, S, and Al. TiN preferentially precipitates on the surface of tlie
REM-Ca-Al-0-S complex oxysulfides.
[0082]
The REM-Ca-Al-0-S complex oxysulfides show the following effects. It is
25 possible to prevent (he oxides such as AI2O3 and AhCa-0 complex oxides from

29 remaining in the metallographic structure, to prevent MnS which is coarse sulfides from
being formed, and to prevent TiN which is nitrides from existing independently. As a
result, the fatigue properties of the bearing steel are improved.
[0083]
5 As shown in FIG. 1, the REM-Ca-Al-0-S complex oxysulfides have the
approximately spherical shape, and therefore, it is difficult to be elongated or fractured
by plastic deformation such as forging. Accordingly, even when the repeated stress is
applied, it is difficult to act as the fracture origin. Here, the approximately spherical
shape indicates that maximum difference between a concave and a convex of the surface
10 of the inclusions is 0.5 |.im or less or that a value calculated by dividing a major axis by a
minor axis of the inclusions is 3 or less, as shown in FIG. 1.
[0084]
In order to obtain the effects, in the metallographic structure, it is necessary that
a number fraction of the REM-Ca-Al-O-S complex oxysulfides is 50% to less than 100%
15 in a total number of the inclusions such as AI2O3, Al-Ca-0 complex oxides, MnS, and
TiN. When the number fraction of the REM-Ca-Al-O-S complex oxysulfides is less
than 50%, it is difficuh to obtain the effect in improving the fatigue properties of the
bearing steel. In addition, it is substantially difficult to control the number fraction of
the REM-Ca-Al-0-S complex oxysulfides to be 100%. It is more preferable that the
20 number fraction of the REM-Ca-Al-0-S complex oxysulfides is 60% to less than 100%.
In addition, for example, the number fraction may be obtained by mainly considering the
inclusions having a major axis of 1 |.im or more.
[0085]
In addition, in order to obtain the effects, it is necessary that a number of
25 REM-Ca-Al-0"S complex oxysulfides having a major axis of 5 |.un or more is 0.001

30 pieces to 2 pieces in an observed section of 1 mm"^. Here, the REM-Ca-Al-0-S
complex oxysulfides having a major axis less than 5 |.im is excluded from the
consideration of the number because the existence thereof is harmless in a case where the
oxygen content and the sulfur content are within a determined range.
5 [0086]
When the number of the REM-Ca-Ai-O-S complex oxysulfides having the
major axis of 5 |jm or more is less than 0.001 pieces, it is difficult to sufficiently obtain
the effect in suppressing the harmful inclusions such as AI2O3, AI-Ca-0 complex oxides,
MnS, and TiN. In addition, when the number of the REM-Ca-Al-0-S complex
10 oxysulfides having the major axis of 5 |.mi or more is more than 2 pieces in an observed
section of 1 mm , the effects are saturated and the fatigue properties deteriorates due to
the excessive amount of precipitates. It is more preferable that the number of the
REM-Ca-Al-O-S complex oxysulfides having the major axis of 5 f.mi or more is 0.001
pieces to 1.5 pieces in the observed section of 1 mm .
15 [0087]
In addition, in order to reliably improve the fatigue properties of the bearing
steel, it is necessary to decrease a number of TiN which exists independently from the
REM-Ca-Al-0-S complex oxysulfides and which acts as the fracture origin when the
repeated stress is applied. Specifically, it is necessary that the number of TiN is 0.001
20 pieces to less than 1.0 piece in the observed section of 1 mm , which exists
independently from the REM-Ca-Al-0-S complex oxysulfides and having a major axis
of 5 i-unormore.
[0088]
When the number of TiN existing independently from the REM-Ca-Al-0-S

31 complex oxysulfides is 1.0 piece or more in the observed section of 1 mm , it is difficiilt
to sufficiently obtain the effect in improving the fatigue properties of the bearing steel.
In order to optimally improve the fatigue properties of the bearing steel, it is preferable
that the number of TiN existing independently from the REM-Ca-AI-0-S complex
5 oxysulfides is as small as possible. However, it is substantially difficult to control the
number of TIN to be less than 0.001 pieces. Accordingly, the number of TiN existing
independently from the REM-Ca-Al-0-S complex oxysulfides should be 0.001 pieces to
less than 1.0 piece in the observed section of 1 mm . The number of TiN existing
independently fiom the complex oxysulfides is preferably 0.001 pieces to 0.7 pieces and
10 is more preferably 0.001 pieces to 0.5 pieces in the observed section of 1 mm .
[0089]
The number of incUisions such as the REM-Ca-Al-O-S complex oxysulfides,
AI2O3, the AhCa-0 complex oxides, MnS, and TiN can be measured by using a scanning
electron microscope (SEM) provided with EPMA (electron probe micro analysis) or
15 EDX (energy dispersive X-Ray analysis), a transmission electron microscope (TEM), or
the like.
[0090]
The existence of the inclusions may be confirmed by observing a cross-section
wliich is orthogonal to an extending direction of the bearing steel using the microscope,
20 and the type of inclusions may be identified by conducting a composition analysis using
EPMA or EDX. When the shape of the bearing steel is a round bar and when the radius
of the observing section (cross-section perpendicular to the longitudinal direction) is r in
unit of mm, it is preferable to averagely observe an observing area which is from the
surface of the bearing steel (hot-worked steel) to the depth of l/2r, for example. An
25 observing magnification may be higher than or equal to the magnification in which the

32 inclusions having a major axis of 1 pm or more can be distinguished. In addition, it is
preferable to observe plural visual fields so that the obseiTed area in total is at least 1000
mm^. Thereby, the number fraction and the number of each inclusion existing in the
observed section of 1 mm may be obtained.
5 [0091]
In addition, it is preferable that an Al content in the REM-Ca-Al-0-S complex
oxysulfides is 20 mass% or less in AI2O3 equivalent. In other words, it is preferable that
the Al content in the REM-Ca-AI-0-S complex oxysulfides is 10.6 mass% or less in Al
equivalent. Because it may be possible to shift the melting point of the '
10 REM-Ca-Al-0-S complex oxysulfides to higher than the melting point of molten steel,
and thereby, the REM-Ca-Al-0-S complex oxysulfides may be changed into hard
inclusions. In the inclusions having a higlier melting point than that of molten steei, the
hardness thereof is generally higher.
[0092]
15 In order to reliably increase the melting point of the inclusions to higher than the
melting point of the molten steel and to change the inclusions into the hard inclusions, it.
is preferable that the Al content in the REM-Ca-Al-0-S complex oxysulfides is 10
mass% or less in AI2O3 equivalent. It is most preferable that the Al content in the
REM-Ca-Ai-0"S complex oxysulfides is 5 mass% or less in AI2O3 equivalent. In
20 addition, in order to preferentially precipitate TiN on the REM-Ca-Al-0-S complex
oxysulfides, it is preferable that the Al content in the above inclusions is 1 mass% or
more in AI2O3 equivalent.
[0093]
As described above, TiN complexly precipitates on the surface of the
25 REM-Ca-Al-O-S complex oxysulfides which act as the preferential nucieation sites.

33 Thus, the REM-Ca-Al-0-S-TiN complex oxysulfides are formed. As a result,
precipitation of TIN which is hard and has the sharp angular shape independently
precipitates is suppressed.
[0094]
5 As shown in FIG. 1, the REM-Ca-Al-O-S-TiN complex oxysulfides have the
approximately spherical shape and are the harmless inclusions which hardly act as the
fracture origin. The reason why TiN complexly precipitates on the REM-Ca-Al-O-S
complex oxysulfides which act as the preferential nucleation sites seems that the crystal
structure of the REM-Ca-Al-0-S complex oxysulfides is similar to the crystal structure
10 ofTiN.
[0095]
The above REM-Ca-Al-0-S complex oxysulfides do not include Ti as oxides.
The reason for the above seems that, since the large amount of C, for example 0.9% to
1.5% of C, is contained, the level of oxygen during deoxidization is low, and therefore Ti
15 oxides is hardly formed. In addition, from the circumstantial fact that the
REM-Ca-Al-O-S complex oxj'sulfides do not include Ti as oxides, it is deduced that the
crystal structure of the REM-Ca-Al-0-S complex oxysulfides is similar to the crystal
structure of TiN.
[0096]
20 In general, the Al-Ca-O complex oxides are formed in the metallograpliic
structure of the steel when the steel simultaneously contains Al and Ca. However, the
Al-Ca-0 complex oxides are also transformed to the REM-Ca-Al-0-S complex
oxysulfides by adding REM, and the melting point thereof is shifted to higher.
Therefore, it is possible to prevent the AhCa-O complex oxides from being elongated
25 and coarsened by plastic deformation. Since Ca is added as necessary to the molten

34 steel after REM is added, it is difficult to form Ca-based sulfides such as CaS, Ca-Mn-S,
or the like. The production method will be described later in detail.
[0097]
As described above, since the REM-Ca-Al-0-S complex oxysuifides fix S, the
5 formation of the coarse MnS is suppressed. Moreover, since the REM-Ca-Al-0-S
complex oxysuifides complexly involve TiN, the number of TiN precipitating
independently in the metallographic structure decreases. As a result, the fatigue
properties are improved. Although it is preferable as ideal that the amount of MnS
precipitates and the amount of TiN precipitates existing independently from the
10 REM-Ca-Al-0-S complex oxysuifides are small in the metallographic structure of the
bearing steel according to the embodiment, it is unnecessary to decrease the amount
thereof to zero.
[0098]
In order to reliably satisfy the fatigue properties required as the bearing steel, it
15 is preferable that the amount of MnS and TiN precipitates which exist independently
from the REM-Ca-Al-0-S complex oxysuifides in the metallographic structure satisfy
the following condition. Atotal number of MnS having a major axis of 10 pm or more
and the TiN existing independently from the REM-Ca-Al-0-S complex oxysuifides and
having the major axis of 5 pm or more is preferably 5 pieces or less in the observed
20 section of 1 mm^.
[0099]
Since the elongated MnS having the major axis of 10 pm or more may act as the
fracture origin when the repeated stress is applied, and thereby, the fatigue life is
negatively influenced. Since all of elongated MnS element having tlie major axis of 10
25 i-un or more negatively influence the fatigue life, the upper limit of the major axis may

35 not be limited. Similarly, since TiN which exists independently from the
REM-Ca-Al-O-S complex oxysulfides and which has the major axis of 5 |im or more
acts as the fracture origin due to the angular shape thereof, and thereby, the fatigue life is
negatively influenced. Since all of TiN having the major axis of 5 j.im or more
5 negatively influence the fatigue life, the upper limit of the major axis may not be limited.
[0100]
FIG. 3 shows a relationship between the fatigue properties (LIO fatigue life) of
the bearing steel and the total number of MnS having the major axis of 10 }jm or more
and TiN existing independently from the REM-Ca-Al-O-S complex oxysulfides and
10 having the major axis of 5 jim or more (total number of MnS and TiN existing
independently).
[Old]
As shown in FIG. 3, when the number of MnS and the number of TiN is more
than 5 pieces in total in the observed section of 1 mm^, the fatigue properties of the
15 bearing steel deteriorate. Accordingly, it is preferable that the total number of MnS and
TiN is controlled to the above range. It is more preferable that the above total number is
4 pieces or less in the observed section of 1 mm . it is most preferable that the above
total number is 3 pieces or less in the observed section of I mm^. In addition, the lower
limit of the above total number of MnS and TiN may be more than 0.001 pieces.
20 [0102]
As described above, since AI2O3 and the Al-Ca-O complex oxides which are the
harmful inclusions negatively influencing the fatigue properties of the bearing steel are
mostly transformed to the REM-Ca-Al-0-S complex oxysulfides by the effect derived
from the added REM, and therefore, the existing amount decreases. In addition, the
25 amount of MnS precipitates which is the harmful inclusions is suppressed by the effect

36 derived from the desulfurization of REM and Ca included in the REM-Ca-Al-0-S
complex oxysuifides, in particular, by the effect derived from the desulflirization of Ca.
Furthermore, since TiN which is the harmful inclusion preferentially precipitates on the
surface of the REM-Ca-Al-0-S complex oxysulfides, the amount of TiN precipitating
5 independently decreases. As a result, it is possible to obtain the bearing steel which is
excellent in the fatigue properties.
[0103]
Next, a method for producing the bearing steel according to the embodiment
will be described.
10 [0104]
In the method for producing the bearing steel according to the embodiment, the
order of adding deoxidizing agents is important when the molten steel is refined.
[0105]
In an Al-deoxidizing process, the molten steel after adjusting the composition is
15 Al-deoxidized by adding Al. In a REM-deoxidizing process, the molten steel after the
Al-deoxidizing is REM -deoxidized by adding REM for'5 minutes to 10 minutes. In a
vacuum-degassing process, the molten steel after the REM-deoxidizing may be
vacuum-degassed as necessary by adding Ca. By conducting the ladle refining of the
molten steel in which the deoxidizing agents are added in this order, the REM-Ca-AI-0-S
20 complex oxysulfides are formed, and therefore, it is possible to suppress the formation of
harmfiil AI2O3, the Al-Ca-0 complex oxides, MnS, and TiN.
[0106]
In order to add REM, misch metal or the like may be used, specifically, massive
misch metal may be added to the molten steel at the end of the refining. In addition, in'
25 a fluxing process, the molten sleel after the REM-deoxidizing and before the

37 vacuum-degassing may be fluxed as necessary by adding a flux such as CaO-CaF2 in
order to appropriately desulftu'ize the molten steel and to change the properties of the
inclusions.
[0107]
5 The reason why the Al-deoxidizing process is conducted first is that the
production cost increases when the deoxidization is conducted using elements other than
Al. The reason why the REM-deoxidizing process is conducted after the
Al-deoxidizing process is that REM is reacted with the Al-Ca-0 complex oxides which
are formed by reacting AI2O3 which is formed in the Al-deoxidizing process with Ca
10 which is unavoidably contained in the molten steel, and thereby, the amount of the
Al-Ca-O complex oxides remaining in the metallographic structure is decreased.
[0108]
in addition, the reason why the deoxidization is conducted for 5 minutes to 10
minutes in the REM-deoxidizing process is as follows. When the deoxidization is
15 shorter than 5 minutes, it is difficult to prevent the Al-Ca-O complex oxides from
remaining. On the other hand, the upper limit of the deoxidization time is not
particularly limited in the REM-deoxidizing process. However, when the deoxidization
is longer than 10 minutes, the effect thereof is saturated.
[0109]
20 The reason why the vacuum-degassing process may be conducted as necessary
by adding Ca after the REM-deoxidizing process is as follows. When Ca is added
before adding REM, in other words, when the vacuum-degassing process is conducted
before the REM-deoxidizing process, the Al-Ca-O complex oxides which have the low
melting point and which tend to be elongated may be excessively formed. The Al-Ca-O
25 complex oxides are hardly formed by the amount of Ca which is unavoidably contained.

38 However, the Al-Ca-0 complex oxides may be excessively formed by the amount of Ca
which is puiposely added (for example, 0.00050% or more). Once the Al-Ca-0
complex oxides are formed, it is difficult to sufficiently transform the inclusions even
when REM is added after adding Ca. In addition, another reason of this process order is
5 to suppress the formation of Ca-containing sulfides such as CaS, Ca-Mn-S, or the like.
[0110]
It is preferable to conduct the vacuum-degassing process in which Ca is added
when the molten steel includes, as the chemical composition, by mass%, S: more than
0.01% to 0.05%. As described above, when the S content is more than 0.01% to 0.05%*,
10 it is preferable to add Ca so that the Ca content is 0.00050% to 0.0050%. As a result, it
is possible to further increase the effect such that the REM-Ca-Al-0-S complex
oxysulfides fix S. Moreover, the MnS precipitates are sufficiently suppressed.
[0111]
111 addition, tlie reason why tlie fluxing process may be conducted as necessary
15 after the REM-deoxidizing and before the vacuum-degassing process is as follows.
When the flux is added before adding REM, in other words, when the fluxing process is
conducted before the REM-deoxidizing process, the Al content in the REM-Ca-Al-O-S
complex oxysulfides becomes more than 20 mass% in AI2O3 equivalent, the melting
point of the complex oxysulfides is shifted to lower, and as a result, the complex
20 oxysulfides tend to be fractured. The fractured complex oxysulfides negatively
influence the fatigue properties in common with the elongated inclusions,' and therefore,
the effect in changing the properties of the inclusions derived from the added REM is not
sufficiently obtained.
[0112]
25 Subsequently, in a casting process, the molten steel after the REM-deoxidizing

39 or after the vacuum-degassing process is cast in order to obtain a cast piece. In the
casting process, it is preferable that the molten steel is cast and solidified while being
rotated horizontally in a mold under a condition of 0.1 m/minute to 0.5 m/minute.
[0113]
5 The specific gravity of the REM-Ca-Al-0-S complex oxysulfides formed by the
ladle refining such as the Ai deoxidization or REM deoxidization as described above is
approximately 6 and is close to 7 which is the specific gravity of the steel. Thus, it is
difficult for the REM-Ca-Al-0-S complex oxysulfides to be separated by flotation in the
molten steel. Moreover, since the REM-Ca-Al-0-S complex oxysulfides tend to
10 penetrate deeply into unsolidified layer of the cast piece due to a downward flow when the molten steel is poured into the mold, the REM-Ca-Al-O-S complex oxysulfides tend to segregate in a center of the cast piece. When the REM-Ca-Al-O-S complex oxysulfides segregate in the center of tlie cast piece, the amount of the complex oxysulfides near a surface of the cast piece comparatively decreases. Thereby, the
15 TiN-detoxifying effect of the REM-Ca-Al-0-S complex oxysulfides, by acting as the preferential nucleation sites of TiN, decreases near the surface of the cast piece. [0114]
Accordingly, it is preferable that the molten steel is stirred and rotated horizontally in the mold as necessary and that the inclusions is uniformly dispersed in
20 order to suppress the segregation of the REM-Ca-Al-0-S complex oxysulfides. It is possible to uniformly disperse the REM-Ca-Al-0-S complex oxysulfides by rotating the molten steel horizontally in the mold under the condition of 0.1 m/minute to 0.5 m/minute. When the rate of the rotation in the niold is slower than 0.1 m/minute, the effect in uniformly dispersing the REM-Ca-Al-0-S complex oxysulfides is small. In
25 addition, it is assumed that the upper limit of the range of the rotation rate is 0.5

40 m/minutes under a typical condition. For a method of stirring the molten steel,
electromagnetic force or the like may be applied.
[0115]
Subsequently, in a heating and holding process, the cast piece after the casting
5 process is heated m a temperature range of 1270°C to 1300°C and is held after the
heating in a temperature range of 1200°C to 1250°C for 60 seconds or longer. In the
heating and liolding process after the casting process, the cast piece which is cooled to a
room temperature may be reheated and held, or the cast piece which is not cooled to the
room temperature may be reheated and held. From an industrial standpoint, although
10 the cast piece may be heated for a long time, for example, approximatety 72 hours in a
flirnace in the temperature range of 1200°C to 1250°C for homogenization of the
material, the heating does not negatively influence the control of the complex oxysulfides.
Accordingly, the upper limit of the holding time in the temperature range of i200°C to
i250°C is not particularly limited. The upper limit thereof may be 100 hours in
15 consideration of the typical operational condition.
[0116]
The reason why the cast piece is heated in the temperature range of 1270°C to
1300°C is that the temperature which is lower than 1270°C is insufiicient as a
temperature of solutionizing treatment, and therefore, it is ditficult to dissolve and
20 solid-solute TiN which precipitates independently from the REM-Ca-Al-0-S complex
oxysulfides during cooling after the casting process. F^or the temperature which is
higher than 1300°C, expensive equipment is required for the heating and the cost of the
heating also increases.
[0117]
25 The reason why the cast piece is held in the temperature range of 1200°C to

41 1250°C after the heating is for preferential and complex precipitation of TIN, which is
dissolved in the heating, on the surface of the REM-Ca-Al-0-S complex oxysulfides.
In order to precipitate and sufficiently grow TIN on the surface of the REM-Ca-Al-O-S
complex oxysulfides which act as the preferential nucleation sites, the holding for 60
5 seconds or longer is necessary. In addition, from an industrial standpoint, although the
cast piece may be heated for a long time, for example, approximately 72 hours for
homogenization of the material, the holding does not negatively influence the control of
the complex oxysulfides.
[0118]
10 In general steel, for example, in low carbon steel, even when the cast piece is
heated in the temperature range of 1270°C to 1300°C, and thereafter, is held in the temperature range of 1200°C to 1250°C, TiN is in a state of being solid-soluted and is not precipitated. However, in the steel according to the embodiment, since the steel is high carbon steel such that the C content is 0.9% to 1.5% and the solubility of N of the steel is
15 low, it is considered that TiN preferentially precipitates and grows on the
REM-Ca-Al-0-S complex oxysulfides when the cast piece is held in this temperature range,
[0119]
Subsequently, in a hot-plastic-working process, the cast jiiece after the heating
20 and holding process is subjected to the plastic deformation such as hot forging or hot roiling in order to obtain the hot-worked steel (bearing steel), it is preferable that the hot-working is conducted in a temperature range of Arm (temperature where cementite starts to form in austenite during cooling in hyper-eutectoid steel) to 1200°C. When the hot-working is conducted at a temperature of lower than Am,, the amount of cementite
25 increases, and thereby, the plastic deformability decreases. When the hot-working is

42 conducted at a temperature of higher than 1200°C, the production cost increases because
the energy is excessively used for the heating. In addition, it is preferable that the cast
piece after the heating and holding process is not cooled and is subjected to the
hot-plastic-working process in view of the production cost. In addition, the hot-worked
5 steel may be given a shape in the hot-plastic-working process in order to make the
product (bearing steel or bearings) having a final shape.
[0120]
Since the bearing steel according to the embodiment is the super-eutectoid steel containing 0.9% to 1.5% of C in mass%, the hot-worked steel generally shows the 10 metallographic structure which mainly includes pre-eutectoid cementite with plate shape and pearlite. Moreover, the hardness thereof is hard, for example, approximately 250 Hv to 400 Hv in Vickers hardness.
[0121]
Since the hot-worked steel after the hot-plastic-working process is hard, it is 15 preferable that the hot-worked steel is subjected to a soft-annealing process of conducting heat treatment such as spheroidizing. In the soft-annealing process, it is preferable that the hot-worked steel is held in a temperature range of 700°C to 750°C for 30 hours to 50 hours. When the holding time is shorter than 30 hours, the softening is insufficient. When the holding time is longer than 50 hours, and the effect thereof is saturated. By 20 the soft-aimealing process, it is possible to proceed the spheroidizing of the carbides and to make the softened steel from the hot-worked steel. [0122]
The softened steel may be subjected to at least one of a cold-working process and a cutting process as necessary and may be formed in a shape which is close to that of 25 a final part. Subsequently, in a quenching process, the steel with the shape which is

43 close to that of the final part after the cold-working process and the cutting process is
subjected to the quenching fi"oin a temperature range of 830°C to 900°C in order to
increase the hardness. By the quenching process, it is possible to control the hardness
of the steel to be 800 Hv or more in Vickers hardness. In addition, as necessary, in a
5 final-finishing process, the steel after the quenching process may be subjected to the
final-finishing which use a method capable of performing the highly hard or highly
precise machining such as grinding, in order to make a bearing having the shape of the
final part by forming a bearing sliding part or the like which is required to have a precise
dimension.
10
Example 1
[0123]
Hereinafter, the effect of an aspect of the present invention will be described in detail with reference to the following example. However, the condition in the example
15 is an example condition employed to confirm the operability and the effects of the
present invention, so that the present invention is not limited to the example condition. The present invention can employ various types of conditions as long as the conditions do not depart from the scope of the present invention and can achieve the object of the present invention.
20 [0124]
The molten steel after adjusting the composition w^as subjected to the ladle refining which included, as necessary, the Al-deoxidizing process, the REM-deoxidizing process, the fluxing process, or the vacuum-degassing process with adding Ca in the order as shown in Tables 1 to 3. In the tables, the underlined values indicate out of the
25 range of the present invention. Metallic AI was used in the Al-deoxidizing process,

44 misch metal was used in the REM-deoxidizing process, Ca-Si alloy was used in the
vacuum-degas sing process, and a flux of CaO : CaF2 ^ 50 : 50 (mass ratio) was used in
the fluxing process.
[0125]
5 The molten steel after the ladle refining was cast into a cast piece having 300
mm square in the casting process using a continuous casting apparatus. In Tables 4 to 9,
the chemical composition of the cast piece is shown. The balance of the chemical
composition was Fe and unavoidable impurities. In the tables, the underlined values
indicate out of the range of the present invention, and the blank column indicates that no
10 alloying element was purposely added. In addition, in the casting process, the rotation in the mold was conducted by electromagnetic stirring under the conditions as siio\s'n in Tables 1 to 3. The cast piece after the casting process was subjected to the heat treatment under the heating and holding condition as shown in Tables 1 to 3 in the heating and holding process.
15 [0126]
The cast piece after the heating and holding process was hot-forged at a temperature of 1190^*0 in the hot-plastic-working process in order to obtain a hot-worked steel (bearing steel) having a shape of round bar with 20 mm in diameter. As necessary, the hot-worked steel was subjected to a heat treatment at a temperature of 720°C for 40
20 hours in the soft-annealing process in order to obtain a softened steel (bearing steel).
Thereafter, the machining was conducted so as to have a shape of round bar with 10 mm in diameter by the cutting process. The steel after the cutting process was subjected to the quenching from a temperature of 850°C in the quenching process in order to obtain a bearing steel which was a product.
25 " [0127]

45 In the observation of the metallographic structure, the inclusions in the steel was
observed by using a scanning electron microscope after conducting a selective
potentiostatic etching by electrolytic dissolution method (SPEED method) for an
observing section which was a cross-section which was orthogonal to an extending
5 direction of tlie bearing steel. The type of inclusions was identified by conducting a
composition analysis using EDX. In the observation, when the radius of the obsemng
section (cross-section perpendicular to the longitudinal direction) was r in unit of mm, an
observing area which was from the surface to the depth of l/2r was averagely observed.
The observation was conducted on plural visual fields so tliat the observed area in total
10 was at least 1000 mm , and the number of each inclusion was measured. In Tables 10 to 12, the number fraction of the complex oxysulfides in the total number of the inclusions, the number of the complex oxysulfides having the major axis of 5 j-un or more in the observed section of 1 mm , the number of TiN existing independently from the complex oxysulfides and having the major axis of 5 |im or more in the observed section of 1 mm ,
15 the total number of MnS having the major axis of 10 |,im or more and TiN existing
independently from the complex oxysulfides and having the major axis of 5 |,nn or more in the observed section of 1 mm , and the Al content in the complex oxysulfides in AI2O3 equivalent are shown. [0128]
20 In addition, the fatigue properties of the above bearing steel were measured by
an ultrasonic fatigue test under a load condition of 1000 MPa, and the fatigue properties were evaluated as LIO fatigue properties using Weibull statistics. When the LIO fatigue properties were 10 x 10*^ cycles or more, the fatigue properties were judged to be acceptable. In addition, for an evaluation of mechanical properties, the bearing steel
25 was tempered at a temperature of 180°C, and thereafter, a Vickers hardness Hv was

46 measured. When the temper hardness at the temperature of 180°C was 600 Hv or more,
the mechanical properties were judged to be acceptable.
[0129]
The measurement resuUs and evaluation results are shown in Tables 10 to 12.
5 In the tables, the underlined values indicate out of the range of the present invention. In
the tables, No. 1 to No. 61 are invention examples and No. 62 to No. 98 are comparative
examples. As shown in Tables 10 to 12, in the invention examples, generally, TiN
complexly precipitated on the REM-Ca-Al-0-S complex oxysulfides (in the tables,
represented as REM-Ca-Al-O-S-(TiN)) was mainly observed, and AI2O3 and the Al-Ca-0
10 complex oxides were almost not observed.
[0130]
In addition, in No. 1 to No. 61 of the invention examples, the number or the
fraction of the REM-Ca-Al-0-S complex oxysulfides, TiN, MnS, or the like achieved the
target. As a result, in the invention examples, the LIO fatigue properties were lOx 10*'
15 cycles or more, and therefore, the fatigue properties were acceptable. In addition, in the
invention examples, the Vickers liardness Hv after tiie tempering at the temperature of
180°C was 600 Hv or more, and therefore, the mechanical properties were acceptable.
[0131]
On the other hand, in No. 62 to No. 98 of the comparative examples, the
20 chemical composition, the metal lographic structure, or the production method did not
achieve the target. As a result, the LIO fatigue properties and/or the Vickers hardness
Hv after the tempering at the temperature of 180°C was insufficient.
In Nos. 62 to 65 of tlie comparative Examples, the Ca content was less than the
range of the present invention. As a result, the formation of the oxysulfides was
25 insutTicient, the number of the elongated sulfides was excessive, and the LIO fatigue

47 properties were insufficient.
In No. 66 of the comparative example, the heating temperature and the holding
time were less than the range of the present invention. As a result, the number of TiN
existing independently from the REM-Ca-Al-0-S complex oxysulfides was excessive
5 and the LIO fatigue properties were insufficient.
In Nos. 67, 68, 73 to 75, and 78 to 98 of the comparative examples, the alloying
elements were out of the range of the present invention. As a result, the LIO fatigue
properties were insufficient, the quenching cracks or the cracks during working occurred,
or the performance as the bearings was not satisfied.
10 In No. 69 of the comparative example, the REM content was more than the
range of the present invention. As a result, the adhesion to the refractory was excessive
and the production was judged as difficult.
In Nos. 70 and 72 of the comparative example, the order of the processes during
the ladle refining was different from that of tlie present invention. As a result, the
15 morphology of the oxysulfides or the oxides changed, the inclusions coarsened, and the
LIO fatigue properties were insufficient.
In No. 71 of the comparative example, the REM-deoxidizing time was shorter
than the range of the invention. As a result, the formation of the oxysulfides was
insufficient, the number of the elongated sulfides was excessive, and the LIO fatigue
20 properties were insufficient.
In No. 76 of the comparative example, the holding temperature was lower than
the range of the invention. As a result, tlie number of TiN existing independently from
the REM-Ca-Al-0-S complex oxysulfides was excessive and the LtO fatigue properties
were insufficient.
25 In No. 77 of the comparative example, the holding temperature was higher than

48 the range of the present invention (thus, the holding time in the temperature range of
1200°C to 1250°C during cooling thereafter was 60 seconds or shorter). As a result, the
number of TiN existing independently from the REM-Ca-Al-0-S complex oxysulfides
was excessive and the LIO fatigue properties were insutficient.
5 [0132]
[Table 1]
[0133]
[Table 2]
[0134]
10 [Table 3]
[0135]
[Table 4]
[0136]
[Table 5]
15 [0137]
[Table 6]
[0138]
[Table 7]
[0139]
20 [Table 8]
[0140]
[Table 9]
[0141]-
[Table 10]
25 [0142]

49 [Table 11]
[0143]
[Table 12]
5 Industrial Applicability [0144]
According to the above aspect of the present invention, it is possible to control the fonnation and the morphology of AI2O3, Al-Ca-O complex oxides, MnS, and TIN which are the harmfiil inclusions by forming the REM-Ca-Al-0-S complex oxysulfides 10 in the metallograpiiic structure of the steel. As a result, it is possible to provide the bearing steel excellent in the fatigue properties and the method for producing the same. Accordingly, the present invention has significant industrial applicability.
Reference Signs List
15 [0145]
A REM-Ca-Ai-0-S COMPLEX OXYSULFIDES
B TiN
C PRE-EUTECTOID CEMENTITE
D MnS
20

L/lg- S^
TABLE 1

No. PRODUCTION CONDITION

LADLE REFINING CONDITION miliaODlIIGI HEATING AN D HOLDING CONDITION

IN ORDER OF AL-DEOXIDIZING PROCESS. REM-DEOXIDiZING PROCESS, FLUXING PROCESS. OR VACUUM-DEGASSING PROCESS REM-DEOXIDIZING TIME
(tn i nute) ROTATION
FLOW RATE
IN MOLD
(mpm) HEATING
TELfPERATURE
CO HOLDING Te^PERATURE
CO HOLDING TIME
(second)
t-U
_i
Q-
> 1 Ai-^REM 8 - 1280 1220 120

2 AI~*REM 8 - 1280 1220 120

3 AI-^REM 8 - 1280 1220 120

4 Af-»REM--> DEGASSING 8 0.05 1280 1220 120

5 AJ-REM-> DEGASSING 8 0.2 1280 1220 120

6 A!-*REM-^ DEGASSING 8 0.2 1280 1220 120

7 Ai~,REM-> DEGASSING 8 0.2 1280 1220 120

8 AI-REM-* DEGASSING 8 0.2 1280 1220 120

9 A!-*REM-^ DEGASSING 8 0.2 1280 1220 120

10 Al-»REM-^ DEGASSING 8 0.2 1280 1220 120

11 AJ-^REM-^ DEGASSING 8 0.2 1280 1220 120

12 Al-»REM-» DEGASSING 8 0.2 1280 1220 120

13 AI-REM-DEGASSING 8 0.2 1280 1220 120

14 AMREM-* DEGASSING 8 0.2 1280 1220 120

15 AMREM-^ DEGASSING to 0.25 1280 1220 120

16 AMREM-* DEGASSING 6 0.15 1280 1220 120

1? Ai^REM^ DEGASSING 8 0.2 1280 1220 120

18 AMREM^ DEGASSING 8 0.2 1280 1220 120

19 AMREM-^DEGASSING 8 0.2 1280 1220 120

20 AM REM-* DEGASSING 10 0.2 1280 1220 200

21 Al^REM-^DEGASSING 8 0.2 1280 1220 120

22 AMREM^DEGASSING 6 0.2 1280 1220 70

23 AMREM^DEGASSING 6 0.25 1280 1220 120

24 Al-^REM-* DEGASSING 8 0.2 1280 1220 120

25 Al~»REM-^ DEGASSING 8 0.2 1280 1220 120

26 Al-»REM-»DEGASSING 8 0.2 1280 1220 120

27 AMREM^DEGASSiNG 8 0.2 1280 1220 120

28 AMREM^DEGASSiNG 6 0.2 1280 1220 120

29 AI-^REM->OEGASSING 6 0.25 1280 1220 150

30 AMREM-* DEGASSING 8 0.15 1280 1220 120

.^7^

iTN

TABLE 2

No. PRODUCTION CONDITION

LADLE REFINING CONDITION GASIIfSOKBIIiaJ HEATING AND HOLDING CONDITION

IN ORDER OF AL-
DEOXIDIZING PROCESS,
REM-DEOXIDIZING
PROCESS,FLUXING
PROCESS.OR VACUUM-
DEGASSING PROCESS REM-DEOXIDIZING
TIME
(minute) ROTATION
FLOW RATE
IN MOLD
(mpm) HEATING
TEMPERATURE
("O HOLDING TEMPERATURE
CO HOLDING TIME
(second)
UJ
_j o_
-a;
X
UJ
UJ
>> 31 At-'REM^ DEGASSING 8 0.2 1280 1220 120

32 AMREM-* DEGASSING 8 0.2 1280 1220 120

33 AMREM^ DEGASSING 8 0.2 1280 1220 120

34 AMREM^ DEGASSING 8 0.2 1280 1220 120

35 AMREM-> DEGASSING 6 0.2 1280 1220 120

36 AI^REM-* DEGASSING 8 0.2 1280 1220 120

37 AI-»REM^ DEGASSING 10 0.2 1280 1220 300

38 AMREM^ DEGASSING 8 0.2 1280 1220 120

39 AMREM^ DEGASSING 8 0.2 1280 1220 120

40 AM REM^ DEGASSING 8 0.2 1280 1220 120

41 A;-REM^ DEGASSING 8 0.2 1280 1220 120

42 AI^REM^ DEGASSING 8 0.2 1280 1220 120

43 Ai^REM-* DEGASSING 8 0.2 1280 1220 120

44 AI-»REM^ DEGASSING 8 0.2 1280 1220 120

45 AI^REM-DEGASSING 8 0.2 1280 1220 120

46 AI-*REM-^ DEGASSING 8 0.2 1280 1220 120

47 Al-REM-DEGASSING 8 0.2 1280 1220 120

48 Ai-REM^ DEGASSING 8 0.2 1280 1220 120

49 Ai^REM^ DEGASSING 8 0.2 1280 1220 120

50 At^REM-^ DEGASSING 8 0.2 1280 1220 120

51 AI-'REM-* DEGASSING 8 0.2 1280 1220 72 HOURS

52 AI-REM^ DEGASSING 8 0.2 1280 1220 120

53 Af-'REM-^ DEGASSING 12 0.2 1280 1220 120

54 AI^REM-^ DEGASSING 6 0.2 1280 1220 150

55 AI^REM-* DEGASSING 8 0.35 1280 1220 120

56 A1-»REM^ DEGASSING 8 0.3 1280 1220 80

57 AMREM^RUX^KGASSIIHJ 6 0.2 1280 1220 120

58 Al-*REM-» DEGASSING 8 0.2 1280 1220 120

59 AI-»REM-* DEGASSING 8 0.2 1280 1220 120

60 AI->REM-» DEGASSING 8 0.2 1280 1220 120

61 ! A1^REM->DE6ASSING 8- 0.2 1280 1220 120

V+r ^1-
TABLE 3

No. PRODUCTION CONDITION

LADLE REFINING CONDITION GASlllffiC^flllia, HEATING AN D HOLDING CONDITION

IN ORDER OF AL-
DE0XIDIZIN6 PROCESS,
REM-DEOXIDIZING
PROCESS, FLUXING
PROCESS, OR VACUUM-
DEGASSiNG PROCESS REM-DEOXIDIZING TIME
(minute) ROTATION
FLOW RATE
IN HOLD
(mpm) HEATING TEf,lPERATURE HOLDING
TEMPERATURE HOLDING
TIME
(second)
—t
:^
X
LU
UJ
>
1—
a.
CD 62 Ai-*REM 6 0.2 1280 1220 150

63 AI-^REM 6 0.2 1280 1220 150

64 AI-»REM 8 - 1280 1220 120

65 AI-*REM 8 " 1280 1220 120

66 AI-*REM-^DEGASS!NG 6 0.2 1250 1200 45

67 Ai-*REM-*DEGASSIN6 6 0.3 1280 1220 150

68 AI->REM->DEGASSING 6 0.2 1280 1220 120

69 AI-»REM-'DEGASS1NG 6 0.2 - - -

70 AI~*nFfiA8SlNfi-^REM 6 0.2 1280 1220 120

71 AI->REM->DEGASSING 3 0.2 1280 1220 80

72 AI-'FIiix-^OEGASSIfUj-^REM 6 0.2 1280 1220 120

73 AMREM-»DE6ASSING 8 0.2 1280 1220 120

74 Al-^REM-'DEGASSING 8 0.2 1280 1220 120

75 Al^REM^DEGASSlNG 6 0.2 1280 1220 120

76 Al^REM-^DEGASSING 6 0.2 1280 1190 120

77 Al^REM^DEGASSlNG 6 0.2 1280 1260 120

78 AI-REM^DEGASSING 8 0.2 1280 1220 120

79 AMREM^DEGASSING 8 0.2 1280 1220 120

80 Al-»REM-^DEGASSING 8 0.2 1280 1220 120

81 AMREM-DEGASSING 8 0.2 1280 1220 120

82 AI-REM-DE6ASSING 8 0.2 1280 1220 120

83 AMREM^DEGASSING 8 0.2 1280 1220 120

84 AMREM^DEGASSING 8 0.2 1280 1220 120

85 Al-^REM-»DEGASS1NG 8 0.2 1280 1220 120

86 Al-^REM-*DEGASSING 8 0.2 1280 1220 120

87 AiwREM-^DEGASSING 8 0.2 1280 1220 120

88 Al-*REM-DEGASS!NG 8 0.2 1280 1220 120

89 A!-»REM-^DE6ASSING 8 0.2 1280 1220 120

90 Ai^REM^DEGASSING 8 ■ 0.2 1280 1220 120

91 Ai->REM^DEGASS1NG 8 0.2 1280 1220 120

92 Ai-->REM^DEGASSING 8 0.2 1280 1220 120

93 Al-REM-^DEGASSING 8 0.2 1280 1220 120

94 Al^REM->DEGASSING 8 0.2 1280 1220 120

95 AI-»REM-^DEGASSING 8 0.2 1280 1220 120

96 AMREM^DEGASSING 8 0.2 1280 1220 120

97 Ai-'REM-'DEGASSING 8 0.2 1280 1220 120

98 Al^REM-»DEGASSiNG 8 0.2 1280 1220 120

4/i^ "^y
TABLE 4

No. PRODUCTION RESULT

CHEMICAL COMPOSITION OF CAST PIECE (MASS%)

C Si Mn P S Cr A! Ca REM Ti N 0
UJ
_j
CL.
-<
X
UJ
UJ
E:
LJJ
>- 1 0.99 0.26 0.71 0.010 0.009 1.17 0.033 0.00004 0.0003 0.002 0.0062 0.0013

2 0.97 0.22 0.75 0.011 0.011 1.20 0.033 0.00002 0.0064 0.003 0.0057 0.0013

3 1.10 0.24 0.90 0.011 0.049 1.09 0.034 O.O0003 0.0052 0.002 0.0064 0.0011

4 1.06 0.22 0.82 0.010 0.007 0.60 0.028 0.00030 0.0009 0.002 0.0074 0.0012

5 1.08 0.23 0.76 0.011 0.007 1,14 0.035 0.00030 0.0012 0.002 0.0056 0.0006

6 0.98 0.30 0.74 0.011 0.007 1.19 0.037 0.00031 0.0031 0.003 0.0057 0.0011

7 1.03 0.22 0.83 0.012 0.0066 1.04 0.030 0.00034 0.0029 0.0019 0.0054 0.0007

8 1.00 0.23 0.72 0.014 0.008 1.05 0.029 0.00041 0.0003 0.0045 0.0075 0.0010

9 0.98 0.28 0.79 0.011 0.007 1.19 0.031 0.00044 0.0019 0.001 0.0057 0.0007

10 1.04 0.21 0.87 0.010 0.009 1.16 0.034 0.00045 .0.0017 0.002 0.0074 0.0010

11 1.05 0.23 0.79 0.012 0.009 l.OI 0.028 0.00029 0.0005 0.001 0.0070 0.0013

12 1.05 0.22 0.75 0.015 0.011 1.09 0.O37 0.00039 0.0068 0.003 0.0067 0.0012

13 I.Of 0.23 0.76 0.010 0.009 1.16 0.038 0.00121 0.0067 0.002 0.0069 0.0009

14 1.10 0.22 0.86 0.014 0.011 1.02 0.032 0.00071 0.0052 0.002 0.0064 0.0009

15 0.98 0.24 0.74 0.007 0.007 1.04 0.026 0.00060 0.0050 0.0006 0.005 0.0006

16 1.00 0.25 0.75 0.007 0.003 1.05 0.025 0.00080 0.0007 0.0006 0.004 0.0006

17 1.00 0,28 0.73 0.014 0.006 1.17 0.032 0.00083 0.0051 0.003 0.0045 0.0010

18 0.96 0.30 0.74 0.012 0.006 1.14 0.028 0.00087 0.0013 0.002 0.0045 0.0011

19 1.04 0.29 0.84 0.013 0.007 1.12 0.035 0.00088 0.0025 0.002 0.0059 O.O009

20 1.00 0.24 0.75 0.007 0.008 1.05 0.027 0.00090 0.0060 0.0004 0.006 O.O005

21 1.09 0.28 0.8 i 0.010 0.009 1.20 0.039 O.00097 0.00167 0.0014 0.0057 0.0009

22 1.01 0.65 0.74 0.007 0.005 !.04 0.026 0.00100 0.0018 0.0004 0.005 0.0005

23 0.98 0.26 0.76 0.006 0.006 1.05 0.027 0.00100 0.0022 0.0009 0.004 O.0004

24 0.92 0.25 0.75 O.007 0.016 0.99 0.015 0.00100 0.0090 0.0040 0.012 0.0015

25 1.08 0.24 0.76 0.015 0.006 1.15 0.036 0.00103 0.0059 0.003 0.0072 0.0009

26 1.01 0.24 0.83 0.012 0.008 1.04 0.038 0.00104 0.0060 0.002 0.0071 0.0014

27 1.01 0.25 0.75 0.008 0.007 1.04 0.025 0.00110 0.0020 0.0006 0.005 0.0005

28 1.01 0.25 0.75 0.007 0.005 1.03 0.024 0.00110 0.0013 0.0015 0.005 0.0005

29 1.00 0.25 0.74 0.010 0.008 1.05 0.026 0.00110 0.0043 0.0010 0.005 0.0005

30 0.99 0.25 0.74 0.007 0.007 1.04 0.025 0.00110 0.0046 0.0009 0.005 0.0005

m^ ^^
TABLE 5

No. PRODUCTION RESULT

CHEMICAL COMPOSIT ON OF CAST PIECE (MASS%)

C Si Mn P s Gr Al Ca REM Ti N 0
UJ
_i
Ou
-a; X UJ
LU
>•
h^ LU IS 31 0.96 0.30 0.86 0.010 0.007 1.11 0.033 0.00114 0.0067 0.001 0.0080 0.0010

32 1.07 0.23 0.89 0.014 0.008 1.01 0.031 0.00121 0.0054 0.002 0.0064 0.0010

33 1.04 0.22 0.72 0.013 0.009 1.04 0.040 0.00121 0.0041 0.002 0.0061 0.0010

34 1.10 0.21 0.71 0.014 0.009 1.09 0.035 0.00131 0.0069 0.001 0.0075 0.0006

35 0.98 0,24 0.75 0.007 0.007 1.05 0.O22 0.00150 0.0023 0.0008 0.005 0.0006

36 1.02 0.27 0.77 0.013 0.0094 1.07 0.040 0.00169 0.00592 0.0015 0.0080 0.0009

37 1.45 0.25 0.75 0.007 0.009 1.04 0.025 0.00170 0.0160 0.0020 0.008 0.0004

38 1.03 0.27 0.83 0.013 0.009 1.13 0.031 0.00177 0.0034 0.002 0.0079 0.0005

39 0.98 0.27 0.79 0.011 0.007 0.97 0.029 0.00040 0.0016 0.002 0.0054 0.0013

40 1.04 0.23 0.77 0.015 0.008 1.13 0.027 0.00130 0.0007 0.002 0.0064 O.O009

41 1.07 0.28 0.88 0.011 0.006 1.05 0.032 0.00182 0.0015 0.003 0.0060 0.0012

42 0.97 0.26 0.30 0.012 0.009 1.03 0.039 0.00131 0.0017 0.003 0.O068 0.0011

43 1.06 0.21 0.85 0.015 0.006 1.08 0.027 0.00121 0.0031 0.003 0.0079 0.0010

44 0.98 0.22 0.76 0.015 0.006 1.72 0.033 0.00115 0.0008 0.003 0.0046 0.0009

45 1.08 0.23 0.80 0.013 0.008 1.55 0.026 0.00129 0.0010 0.002 0.0074 0.0010

46 0.99 0.20 0.74 0.014 0.007 1.01 0.031 0.00061 0.0007 0.002 0.0047 0.0009

47 0.95 0.23 0.85 0.010 0.010 1.02 0.033 0.00189 0.0064 0.002 0.0057 0.0013

48 1.02 0.22 0.89 0.011 0.007 1.14 0.033 0.00073 0.0020 0.002 0.0055 0.0009

49 1.01 0.29 0.89 0.012 0.007 1.11 0.031 0.00033 0.0070 0.002 0.0060 0.0006

50 1.10 0.22 0.71 0.011 0.009 1.03 0.033 0.00164 0.0062 0.001 0.0076 0.0007

51 0.98 0.29 0.82 0.013 0.005 1.03 0.031 0.00044 0.0038 0.003 0.0073 0.0007

52 1.00 0.26 0.77 0.011 0.006 1.17 0.039 0.00068 0.0005 0.002 0.0055 0.0010

53 1.01 0.25 0.75 O.O07 0.009 1.05 0.025 0.00200 0.0390 0.0010 0.005 0.0005

54 0.99 0.24 0.73 0.007 0.003 1.05 0.023 O.OO200 0.0011 0.0011 0.004 0.0005

55 1.01 0.24 0.76 0.008 0.008 1.04 0.038 0.00200 0.0055 0.0012 O.OOS 0.0003

56 1.00 0.26 0.75 0.008 0.008 1.05 0.024 0.00200 0.0110 0.0010 0.005 0.0004

57 1.01 0.25 0.75 0.007 0.001 1.05 0.025 0.00250 0.0020 0.0025 0.005 0.0005

58 1.02 0.24 1.10 0.0O7 0.009 1.05 0.025 0.00440 0.0150 0.0009 0.005 0.0003

59 0.97 0.26 0.84 0.011 0.009 1.13 0.025 0.00241 0.0032 0.002 0.0069 0.0011

60 0.98 0.27 0.79 0.015 0.011 1.14 0.038 0.00250 0.0062 0.002 0.0047 0.0007

61 1.07 0.24 0.72 0.015 0.049 1.09 0.028 0.00149 0.0064 0.001 0.0049 0.0007 1

^frr ^
TABLE 6

No. PRODUCTION RESULT

CHEMICAL COMPOSITION OF CAST PIECE (MASS%)

G Si Mn P S Cr Al Ca REM Ti N 0
UJ
—J -=c
X
LU
UJ
>-
i_-
o 62 1.00 0.25 0.75 0.007 0.005 1.04 0.025 0.000004 0.0025 O.O0O7 0.005 0.0005

63 0.99 0.24 0.76 0.007 0.006 1.04 0.021 0.000005 0.0033 0.0008 0.004 0.0005

64 1.01 0.25 0.73 0.011 0.007 1.06 0.026 0,000008 0.0029 0.002 0.0048 0.0010

65 0.96 0.27 0.81 0.014 0.020 1.03 0.032 0.000008 0.0016 0.002 0.0046 0.0011

66 0.99 0.25 0.75 0.006 0.008 1.05 0.025 0.00080 0.0020 0.0005 0.005 0.0005

67 0.99 0.25 0.74 0.006 0.014 1.03 0.026 0.00100 0.0030 0.0080 0.007 0.0004

68 1.02 0.25 0.75 0.008 0.005 1.04 0.025 0.00110 0.00007 0.0008 0.005 0.0005

69 1.01 0.25 0.74 0.007 0.009 1.02 0.024 0.00110 0.0630 0.0017 0.005 0.0005

70 1.00 0.Z5 0.75 0.007 0.006 1.04 0.025 0.00150 0.0030 0.0010 0.005 0.0006

71 1.00 0.24 0.76 0.007 0.007 1.05 0.025 0.00170 0.0035 0.0003 0.005 0.0009

72 1.00 0.26 0.75 0.007 0.001 1.07 0.024 0.00240 0.0015 0.0025 0.005 0.0005

73 1.03 0.22 0.87 0.011 0.061 1.11 0.030 0.00490 0.0010 0.001 0.0070 0.0013

74 0.97 0.28 0.71 0.015 0.049 1.06 0.034 0.00510 0.0055 0.002 0.0051 0.0013

75 1.01 0.26 0.75 0.007 0.006 1.05 0.023 0.00590 0.0017 0.0008 0.005 0.0005

76 1.05 0.21 0.73 0.014 0.007 1.05 0.038 0.00146 0.0066 0.002 0.0070 0.0006

77 1.10 0.23 0.90 0.013 0.008 1.16 0.036 0.00083 0.0064 0.002 0.0059 0.0006

78 0.88 0.28 0.71 0.013 0.007 1.13 0.025 0.00144 0.0016 0.002 0.0074 0.0014

79 1.52 0.22 0.83 0.013 0.007 1.14 0.039 0.00171 0.0057 0.003 0.0058 0.0008

80 1.03 0.Q8 0.77 0.013 0:007 1.16 0.029 0.00064 0.0032 0.003 0.0072 0.0010

81 1.02 0.82 0.78 0.010 0.007 1.14 0.030 0.00047 0.0010 0.003 0.0063 0.0007

82 1.03 0.26 0.08 0.01 Z 0.006 1.06 0.035 0.00174 0.0059 0.001 0.0043 0.0006

83 0.98 0.26 1.52 0.014 0.005 1.14 0.035 0.00167 0.0059 0.001 0.0069 0.0006

84 1.07 0.28 0.78 0.032 0.008 1.12 0.036 0.00128 0.0041 0.003 0.0072 0.0015

85 0.99 0.21 0.76 0.011 0.009 0.48 0.036 0.00149 0.0018 0.003 0.0064 0.0014

86 1.09 0.25 0.73 0.011 0.005 2,22 0.031 0.00040 0.0041 0.002 O.0071 0.0013

87 1.09 0.23 0.73 0.013 0.008 1.03 0.008 0.00156 0.0019 0.003 0.0045 0.0015

88 1.01 0.29 0.80 0.013 0.005 1.11 0.052 0.00095 0.0036 0.002 0.0051 0.0009

89 0.99 0.25 0.81 0.012 0.008 1.06 0.030 0.00086 0.0043 0.003 0.0160 0.0008

90 1.01 0.23 0.72 0.014 0.006 1.08 0.031 0.00190 0.0011 0.001 0.0073 0.00008

91 ,1.02 0.25 0.82 0.010 0.010 1.16 0.037 0.00192 0.0011 0.001 0.0069 0.0032

92 0.97 0.21 0.89 0.013 0.009 1.18 0.028 0.00077 0.0050 0.002 0.0059 0.0013

93 1.06 0.25 0.83 0.014 0.008 1.01 0.040 0.00110 0.0037 0.002 0.0054 0.0007

94 1.02 0.27 0.79 0.014 0.005 1.03 0.028 0.00178 0.0011 0.002 O.0O57 0.0015

95 1.02 0.23 0.70 0.014 0.005 1.03 0.027 0.00066 0.0011 0.001 0.0048 0.0009

96 0.99 0.29 0.82 0.014 0.007 1.07 0.028 0.00098 0.0038 0.002 0.0058 0.0009

97 1.02 0.20 0.77 0.015 0.009 1.18 0.026 0.00034 0.0009 0.001 0.0074 0.0006

98 0.99 0.25 0.88 0.010 0.009 1.09 1 0.036 0.00082 0.0063 0.002 0.0049 0.0006 1

7-/i^rg
TABLE 7

No. PRODUCTION RESULT
CHEMICAL COf POSITION OF CAST P ECE CMASS%) CASTING RESULT

V Mo W Ni Gu Nb B

LU
_J CL.
-<
X
LU
L±J
>■
:s
LU
> 1 COMPLETELY CAST

2 COMPLETELY CAST

3 COMPLETELY CAST

4 COMPLETELY CAST

5 COMPLETELY CAST

6 1.53 0.22 COMPLETELY CAST

7 0.26 0.45 0.34 COMPLETELY CAST

8 0.23 COMPLETELY CAST

9 0.019 COMPLETELY CAST

10 COMPLETELY CAST

11 COMPLETELY CAST

12 COMPLETELY CAST

13 COMPLETELY CAST

14 COMPLETELY CAST

15 COMPLETELY CAST

16 COMPLETELY CAST

17 COMPLETELY CAST

18 COMPLETELY CAST

19 0.0025 COMPLETELY CAST

20 COMPLETELY CAST

21 0.21 0.10 0.011 COMPLETELY CAST

22 COMPLETELY CAST

23 COMPLETELY CAST

24 COMPLETELY CAST

25 COMPLETELY CAST

26 0.23 COMPLETELY CAST

27 COMPLETELY CAST

28 COMPLETELY CAST

29 COMPLETELY CAST

30 COMPLETELY CAST

8/4^ ^^
TABLE 8

No. PRODUCTION RESULT
CHEMICAL COf POSITION OF CAST PIECE (MASS%) CASTING RESULT

V Mo w Ni Gu Nb B

LU
_l Q-
•< X
LU
LU
>-
f—
LU
>• 31 0.2? COMPLETELY OAST

32 COMPLETELY CAST

33 0.25 COMPLETELY CAST

34 1.62 COMPLETELY CAST

35 COMPLETELY CAST

36 0.15 0.15 0.51 COMPLETELY CAST

37 COMPLETELY CAST

38 COMPLETELY CAST

39- 0.048 COMPLETELY CAST

40 0.052 COMPLETELY CAST

41 0.048 COMPLETELY CAST

42 0.052 COMPLETELY CAST

43 0.048 COMPLETELY CAST

44 0.055 COMPLETELY CAST

45 0.09 COMPLETELY CAST

46 0.11 COMPLETELY CAST

47 0.09 COMPLETELY CAST

48 0.11 COMPLETELY CAST

49 0.0048 COMPLETELY CAST

50 0.0052 COMPLETELY CAST

51 0.0005 COMPLETELY CAST

52 0.0005 COMPLETELY CAST

53 COMPLETELY CAST

54 COMPLETELY CAST

55 COMPLETELY CAST

56 COMPLETELY CAST

57 COMPLETELY CAST

58 COMPLETELY CAST

59 COMPLETELY CAST

60 COMPLETELY CAST

61 COMPLETELY CAST

sm^ s^
TABLE 9

No. PRODUCTION RESULT
CHEMICAL COMPOSITION OF CAST PIECE (HASS%) CASTING RESULT

V Mo w Ni Cu Nb B

LU _J
^ •< X LU
LU
-<
-<
Q_
IS
o 62 COMPLETELY OAST

63 COMPLETELY CAST

64 COMPLETELY CAST

65 COMPLETELY CAST

66 COMPLETELY CAST

67 COMPLETELY CAST

68 COMPLETELY CAST

69 IIIIEWIEO DOE 10 liOZZLE H.0(XA6E

70 COMPLETELY CAST

71 COMPLETELY CAST

72 COMPLETELY CAST

73 COMPLETELY CAST

74 COMPLETELY CAST

75 COMPLETELY CAST

76 COMPLETELY CAST

77 COMPLETELY CAST

78 COMPLETELY CAST

79 COMPLETELY CAST

80 COMPLETELY CAST

81 COMPLETELY CAST

82 COMPLETELY CAST

83 COMPLETELY CAST

84 COMPLETELY CAST

85 COMPLETELY CAST

86 COMPLETELY CAST

87 COMPLETELY CAST-

88 COMPLETELY CAST

89 COMPLETELY CAST

90 COMPLETELY CAST

91 COMPLETELY CAST

92 0.72 COMPLETELY CAST

93 1.02 COMPLETELY CAST

94 1.02 COMPLETELY CAST

95 3.52 COMPLETELY CAST

96 0.52 COMPLETELY CAST

97 0.052 COMPLETELY CAST

98 1 0.0052 1 COMPLETELY CAST

Wrz S~1
TABLE 10

No. EVALUATION RESULT
METALLOGRAPHIG OBSERVATION FATIGUE
PROPERTIES
LIO
(x105(rfaES) VICKERS
HARDNESS
AFTER
TEHPERIfIG
AT lao'-c
(Hv)

STATE OF OXYSULFIDES mm] iH
OXYSaPlDES (MASS%) FRACTIffilOF
0)!YSiiFireS
in TOTAL
wnmm fSMROf
OXVSllFIffiS
HAVIIffillAJgi
AXIS 1^5
(PIECE/mn^) TiHBdSIIIB liSEPeiSJTLy
mi
(PIECE/mrn^) TOTAL lliM ffl^Af® TiHEXISTIfS
FfitfJ Oy^SOLFlOES (PIECE/irffl2)

UJ
1
X
LU
LU
>>
i—
:s
UJ
> 1 REM-Ca-AhO-S-{TiN) 9.5 54 0.61 0.021 4.58 15 698

2 REM-Ca-A}-0-S-{TiN) 7.4 80 0.27 0.017 2.63 11 695

3 REM-Ca-Al-0-S-CTiN) 12.8 77 0.68 0.018 4.03 10 696

4 REM-Ca-At-0-S-(TiN) 8.4 82 0.9? 0.005 1.43 14 698

5 REM-Ca-Al-0-S-CTiN) 11.3 90 0.27 0.004 1.13 18 710

6 REM-Ca-AI-0-S-{TiN) 8.7 72 0.88 0.048 2.62 18 725

7 REM-Ca-AI-0-S-{TlN) 15.5 84 0.79 0.021 2.90 22 749

8 REM-Ca-AI-O-S-diN) 15.4 52 1.66 0.561 4.51 12 733

9 REM-Ca-AhO-S-(TiN) 10.4 94 0.25 0.002 2.12 18 736

to REf-l-Ca-AI-0-S-y-0'S-CTiN) 13.7 71 0.46 0.032 3.09 18 695

w^ c^
TABLE 12

No. EVALUATION RESULT
METALLOGRAPHIG OBSERVATION FATIGUE
PROPERTIES
UO VICKERS HARDNESS
AFTER TEMPERING
AT mo
(Hv)

STATE OF OXYSULFIDES AI2O3 Cft^iTEfir IN OXVSUflDES
(MASS%) FRACriOfi ff
OXVSULFiDES
IN TOTAL
IliaOSIfflS
(%) fagSEROF
oxvmFiffis
HAVIliO yAJOfl WIS Of 5 pORIM
(PIECE/rra2) fiyiEROF TiilBdSTIfffi
mmw%
(PIECE/(mi2) liliEXiSTIfM lllFEfSE)ITLy
FftOa 0\TailT!ffiS (PIEGE/m2}

UJ _J
X
LU
LU
>-1—I
is
a:
o o 62 REM-O-S 2.1 37 3.9 0.264 5.98 6.4 731

63 REM-Al-0-S 5.6 35 3.5 0.265 6.18 6.3 740

64 REM-AI-0-S 15.0 45 2.1 0.010 5.15 9.5 650

65 REM~A!-0-S 15.0 25 4=9 0.023 5.95 4.5 650

66 67 REM-Ca-AhO-S 14.8 53 1,9 1.271 5.88 4.9 728

REM-Ca-A{-0-S-CTiN) 13.6 35 M 1.618 6.80 5.8 714

68 Ai-Ca-0 68.0 36 4.4 1.310 6.19 3.7 707

69 NOZZLE BLOCKAGE OCUURS

70 AhCa-0 13.7 49 4.6 0.194 6.31 4.1 739

71 A!-Ca-0, REM-Ca-AhO-SHTiN) 4.7 39 2.8 0.173 5.99 6.2 723

72 REM-Ga-AI-0-S-(TiN) (FRACTlS^E) 38.8 61 1.8 0.230 6.41 7.5 735

73 MnS 3.6 42 2.1 0.500 6.95 8.3 692

74 CaO, A!-Ca-0 5.1 35 11 1.100 7.35 8.5 695

75 CaO 14.6 33 5.5 0.446 6.78 5.6 722

76 REM-Ca-Al-O-S 14.9 52 2.0 1.269 5.87 5.0 692

77 REM-Ca-AI-O-S 14.7 54 1.8 1.270 5.87 5.1 701

78 REM-Ga-AI-O-S-CTiN) 7,0 79 0.85 0.029 3.13 8.0 590

79 CRACKS OCCUR DURING QUENCHIHG

80 REM-Ga-At-O-S^TiN) | 14.5 88 0.85 0.022 3.96 7.8 580

81 CRACKS OCCUR DURING OUEfJCHING

82 REH-Ca-AI-O-S-(TiN) | 12.5 82 0.85 0.021 1.37 7.7 585

83 CRACKS OCCUR DURING QUENCHING

84 REM-Ga-At-0-S-{TiN) 11.2 73 0.85 0.045 3.89 7.9 698

85 REf,(-Ca-Ai-0-S-CTiN) 5.1 76 0.85 0.028 1.84 7.7 583

86 CRACKS OCCUR DURING QUENCHING

87 REM-Ca-0-S 1.9 36 M 0.230 5.95 6.3 652

88 AIjOs.At-Ca-O 21.3 32 3^ 0.240 5.97 6.5 661

89 TiN, REh!-Ga-Al-0-S-(TiN) 10.1 33 U. 1.580 6.70 6.3 633

90 REM-Oa-AhS 9.4 35 3.5 0.235 5.93 6.3 636

91 A!203. REM-Ca-AI-0-S-