A water-resistant and long-life rolling bearing used in an environment involving water's seeping in the lubricant thereof, wherein at least one of the inner race, the outer race, and the rolling member is formed of alloy steel containing 0.05 to 0.60% by weight of Cu, 0.10 to 1.10% by weight of C, and 0 to 0.2% by weight of Nb or V. The alloy steel has functions of reducing hydrogen evolution on the surface thereof and of forming a film hardly permeable to hydrogen thereby to retard occurrence of flaking due to hydrogen-induced brittleness.

FIELD OF THE INVENTION 
This invention relates to a water-resistant long-life rolling bearing and 
more particularly to a rolling bearing which had a long duration of life 
even if water seeps in the lubricant of the bearing and is suitable for 
use as a roll neck bearing of a rolling mill, a water pump bearing for an 
automobile engine, etc. 
BACKGROUND OF THE INVENTION 
In general, the durability of a rolling bearing is reduced if water enters 
the lubricant. For example, incorporation of as little as 100 ppm of water 
into the lubricant causes a reduction in bearing life by 32 to 48% (see 
Schatzberg, P. and Felsen, I. M., Wear, Vol. 12, pp. 331-342, "Effects of 
water and oxygen during rolling contact lubrication" (1968) and 
Schatzberg, P. and Felsen, I. M., Journal of Lubrication Technology, ASME 
Trans. F, 91, 2, pp. 301-307, "Influence of water on fatigue failure 
location and surface alteration during rolling contact lubrication" 
(1969)). 
Therefore, a bearing used in an environment involving contact with water, 
such as a roll neck bearing of a rolling mill or a water pump bearing, 
should be given a countermeasure for sealing out water so as to avoid 
reduction of life. For example, JP-B-55-22648 (the term "JP-B" as used 
herein means an "examined published Japanese patent application") 
discloses a roll neck bearing for a rolling mill with its both sides 
sealed by a contact seal, such as an oil seal, and JP-A-59-223103 (the 
term "JP-A" as used herein means an "unexamined published Japanese patent 
application") discloses a bearing with its both sides sealed by a 
noncontact seal having a narrow bent gap. 
The sealing structures disclosed have achieved improved sealing properties 
over conventional countermeasures but are still insufficient in view of 
the duration of life of a bearing. That is, the bearing having a contact 
seal cannot completely prevent water from seeping in when the temperature 
of the bearing drops because air within the bearing contracts and sucks in 
outside water. The bearing with a noncontact seal still cannot get rid of 
the problem of water's seeping in through the gap of the seal. 
Seeing that the presence of only a little water as 100 ppm in the lubricant 
greatly influences the life of a bearing as stated above, any seal would 
produce no effect unless incorporation of water is completely prevented. 
Since it has been unknown why existence of water causes such a significant 
reduction in bearing life (see Ioanniedes, E. and Jacobson, B., Ball 
Bearing Journal, Special '89, pp. 22-27 "Dirty lubricants-reduced bearing 
life" (1989)), it has been difficult to take a radical measure to extend 
the bearing life from the standpoint of material. Attempts to prevent 
water's seeping in have therefore been confined to superficial measures 
for improvement on the performance of a seal. 
SUMMARY OF THE INVENTION 
The present invention has been completed with the attention paid to the 
above-described problem of the conventional techniques. Accordingly, an 
object of the present invention is to provide a water-resistant and 
long-life rolling bearing which has a long life even in an environment 
allowing water to seep in the lubricant by using a material having 
excellent functions of reducing hydrogen evolution mainly on the surface 
of steel and of forming a film hardly permeable to hydrogen to reduce 
hydrogen coming into steel thereby retarding occurrence of flaking due to 
hydrogen-induced brittleness. 
The inventors of the present invention have studied the influences of water 
on rolling fatigue of a rolling bearing and as a result revealed the 
following mechanism. 
(1) Hydrogen evolved through corrosion reaction enters, in its atomic 
state, through boundaries of former austenite crystal grains on the 
raceway of a bearing and is diffused through the grain boundaries and 
becomes hydrogen molecules, i.e., changes into hydrogen gas in the 
interstices among non-metallic inclusions crossing the former austenite 
crystal grain boundaries and a matrix material. 
(2) As the amount of hydrogen gas increases, the inner pressure of the 
interstices increases. When rolling members pass over the interstices, the 
inner pressure increases further. Such being the case, cracks initiate 
almost parallel to the raceway as if to expand the interstices thereby to 
decrease the hydrogen gas pressure. 
(3) Meanwhile, the amount of hydrogen gas increases again, and the cracks 
develop further to decrease the pressure in the interstices. 
(4) While the rises and falls of pressure in the interstices alternate, the 
cracks keep on developing, finally causing flaking. Because of repetition 
of crack development in this way, the fracture due to flaking exhibits a 
pattern like annular rings having an oxide inclusion in the center. In 
many cases, the non-metallic inclusion that has acted as a starting point 
of cracking falls off upon occurrence of flaking and is difficult to 
detect. 
In the present invention, such a flaking phenomenon of a bearing is called 
"hydrogen-induced brittleness flaking". While general flaking occurs 
taking part of non-metallic inclusions having a minimum given size as a 
starting point of initial flaking, hydrogen-induced brittleness flaking 
takes place from all the countless non-metallic inclusions as a starting 
point. Even through the countless non-metallic inclusions could be reduced 
to half in number, there would still remain a great number of nonmetallic 
inclusions so that it is impossible to extend the bearing life by highly 
purifying the material steel. 
The inventors have reached the present invention based on the thus revealed 
mechanism. 
The invention provides a rolling bearing used in an environment involving 
water's seeping in the lubricant thereof, wherein at least one of the 
inner race, the outer race, and the rolling member (rolling elements) is 
made of alloy steel containing 0.05 to 0.60% by weight of Cu, 0.10 to 
1.10% by weight of C, and 0 to 0.2% by weight of Nb or V.

DETAILED DESCRIPTION OF THE INVENTION 
The alloy steel used in the invention essentially contains 0.05 to 0.60% by 
weight of Cu. Cu suppresses corrosion of steel to reduce hydrogen 
evolution on the surface of steel and also forms a film hardly permeable 
to hydrogen, serving to reduce the amount of hydrogen entering the steel. 
Therefore, Cu is extremely effective in retarding occurrence of 
hydrogen-induced brittleness flaking. If the Cu content is less than 
0.05%, no substantial effect is produced. If its exceeds 0.60%, the alloy 
steel has reduced hot-processability. 
The alloy steel used in the invention essentially contains 0.10 to 1.10% by 
weight of C. If the C content is less than 0.10%, too much time is 
required for carburizing (or carbonitriding), which is unfavorable for 
productivity. If the C content exceeds 1.10%, the bearing has reduced 
dimensional stability. 
The alloy steel used in the invention preferably contains up to 0.20% by 
weight of Nb or V or contains both Nb and V in a total amount of not more 
than 0.20% by weight. Nb or V functions to make former austenite crystal 
grains finer thereby providing more grain boundaries where hydrogen atoms 
can pass through. It follows that hydrogen gas is delivered to many 
inclusions, which is effective in retarding hydrogen-induced brittleness 
flaking. Although the similar effect might be produced by other elements 
having the same function, such as Al and N, addition of Nb or V brings 
about better results in terms of water resistant life of a bearing. The 
upper limit of the Nb or V content is 0.2% from the economical 
consideration. 
In a preferred embodiment of the invention, the alloy steel contains 0.030 
to 0.150% by weight of P, 0.020 to 0.060% by weight of Al, and 0.005 to 
0.015% by weight of N. 
P functions similarly to Cu. That is, it suppresses corrosion of steel to 
reduce hydrogen evolution on the surface of steel and also forms a film 
hardly permeable to hydrogen, serving to reduce the amount of hydrogen 
entering the steel. Therefore, P is extremely effective in retarding 
occurrence of hydrogen-induced brittleness flaking. A P content less than 
0.030% produces insubstantial effect. If the P content exceeds 0.150%, the 
steel tends to become too brittle for use as a bearing material. From the 
standpoint of equipment cost, the upper limit of the P content is 
preferably 0.025% by weight. 
Al functions to make former austenite crystal grains finer similarly to Nb 
and V, thereby providing more grain boundaries where hydrogen atoms can 
pass through. It follows that hydrogen gas is delivered to many 
inclusions, which is effective in retarding hydrogen-induced brittleness 
flaking. An Al content less than 0.020% produces insubstantial effect. Al 
contents exceeding 0.060% bring no further improvement, only resulting in 
an increase of cost. 
N also functions to make former austenite crystal grains finer similarly to 
Al, Nb and V, thereby providing more grain boundaries where hydrogen atoms 
can pass through. It follows that hydrogen gas is delivered to many 
inclusions, which is effective in retarding hydrogen-induced brittleness 
flaking. An N content less than 0.005% produces insubstantial effect. N 
contents exceeding 0.015% bring no further improvement, only resulting in 
an increase of cost. 
In another preferred embodiment of the invention, the alloy steel contains 
0.15 to 1.10% by weight of Si, 0.35 to 1.50% by weight of Mn, and 0.35 to 
3.5% by weight of Cr. 
Si is added as a deoxidizer in steel manufacturing. At an Si content of 
less than 0.15%, no deoxidizing effect is exerted. An Si content more than 
1.10% causes unevenness in carburizing (or carbonitriding), failing to 
obtain sufficient hardness in places. In order to uniformly conduct the 
heat processing for carburizing (or carbonitriding) to obtain uniform 
hardness in the surface layer, the Si content is preferably not more than 
0.5% by weight. 
The alloy steel according to the present invention may further contain not 
more than 1.10% by weight of Mo, not more than 4.5% by weight of Ni, not 
more than 0.008% by weight of S, and not more than 0.0015% by weight of O. 
Mn, Cr, Mo, and Ni as above referred to can each be added for securing 
hardenability. If the Mn content is less than 0.35%, the effect for 
securing hardenability is insufficient. If the Mn content exceeds 1.5%, an 
abnormal structure due to segregation appears, causing cracks during 
production. If the Cr content is less than 0.35%, the effect for securing 
hardenability is insufficient. If the Cr content exceeds 3.5%, carburizing 
(or carbonitriding) proceeds unevenly, failing to obtain sufficient 
hardness in places. 
Mo and Ni do not always need to be added. If the Mo content exceeds 1.10% 
by weight or if the Ni content exceeds 4.50% by weight, an abnormal 
structure due to segregation appears, causing cracks during production. 
S and O in the alloy steel of the present invention are harmful elements 
which are unavoidably incorporated into alloy steel. That is, S forms 
sulfide inclusions, and O forms oxide inclusions, both accelerating 
rolling fatigue. While it is desirable to minimize these contents, the 
upper limits of the S content and the O content are set at 0.008% and 
0.0015%, respectively, from the economical viewpoint. 
The alloy steel according to the present invention is preferably produced 
by a vacuum arc remelting (hereafter abbreviated as a VAR) method or an 
electro-slag remelting (hereinafter abbreviated as ESR) method. Alloy 
steel obtained by these methods has a uniform structure with reduced 
segregation and is therefore free from local cells and resistant to 
corrosion. Accordingly, hydrogen evolution on the steel surface can be 
reduced, which is effective in retarding occurrence of hydrogen-induced 
brittleness flaking. 
As hereinabove described, at least one of the constituent members of a 
rolling bearing of the present invention, i.e., the inner race, the outer 
race, and the rolling member (rollers) is made of alloy steel having a 
controlled composition so that the hydrogen evolution on the surface of 
the steel may be reduced and a film hardly permeable to hydrogen may be 
formed on the steel surface thereby to reduce the amount of hydrogen 
entering the steel. The present invention thus provides a water-resistant 
rolling bearing that has a long life even when used in such an environment 
that may involve incorporation of water into the lubricant of the bearing. 
PREFERRED EMBODIMENTS OF THE INVENTION 
Bearings according to the present invention (conical rolling bearings) and 
comparative bearings were produced from alloy steel having various 
compositions according to the following specifications and tested by a 
bearing life test in accordance with the test method described below. 
Specifications: 
Bearing designation: HR32017XJ 
Inner diameter: 85 mm 
Outer diameter: 130 mm 
Assembled bearing width: 29 mm 
Basic dynamic load rating: 143000 N 
Properties of Bearing: 
Surface hardness: HRC 58 to 64 
Surface residual austenite: 20 to 45 vol % 
Carburized bearing: 
surface carbon concentration: 0.8 to 1.1 wt % 
Carbonitrided bearing: 
surface carbon concentration: 0.8 to 1.1 wt % 
surface nitrogen concentration: 0.05 to 0.3 wt % 
Test Method: 
The life test was performed by use of the tester shown in FIG. 1. An inner 
race 1 of a conical rolling bearing (work) W is fitted into a bearing seat 
6a, one end of a rotating shaft 6, to set the work W on the tester. An 
outer race 2 is fitted into an internal bearing holder 8 of a housing 7. 
An annular lid 10 having a water channel 9 is fitted to the end of the 
internal bearing holder 8. At the outlet of the water channel 9 is 
provided a spray 11 facing the wider base 3a of the conical roller 3. 
Water is injected into the water channel 9 as indicated by the arrow A. A 
radial load Fr is applied to the rotating shaft 6 by a loading means (not 
shown) to impose the radical load to the work W. An axial load Fs is 
applied to the internal bearing holder 8 by a hydraulic cylinder (not 
shown) to impose the axial load to the work W. 
The conditions of the life test in Examples 1 to 3 were as follows. 
Radial load: 35750 N 
Axial load: 15680 N 
Speed of revolution of inner race: 1500 rpm 
Lubrication: 
a) lubricated with 60 g of grease 
b) lubricated with 60 g of grease in the presence of 3 cc/hr of water 
(sprayed along with air onto the bearing). 
The 10% life L.sub.10 (90% life remaining) of a bearing in the absence of 
water and that of the same bearing in the presence of water were obtained 
to calculate a rate of life reduction due to incorporation of water 
according to equation (1). The lower the rate of life reduction, the more 
water-resistant and long-life is the bearing. 
EQU Rate of life reduction (%)=[(L.sub.10 in the absence of water)-(L.sub.10 in 
the presence of water)]/(L.sub.10 in the absence of water).times.100(1) 
For steel making, the following methods were adopted. 
(1) Furnace: 
An electric furnace or a converter was used. In an electric furnace scrap 
is smelted by the heat of an arc discharge. In a converter the temperature 
is raised to a prescribed temperature by making use of the heat of 
reaction between blown oxygen and elements in molten iron to conduct 
smelting. These furnaces have the same functions of decarburization, 
dephosphorization, removal of silicon, removal of manganese, and 
desulfurization. Ferroalloy is added to the stream of molten steel at the 
time of transfer to a ladle to adjust the composition near to the final 
composition. 
(2) Ladle Furnace (LF): 
Deoxidation, desulfurization, and fine adjustment of alloy elements are 
conducted. 
(3) RH Degassing: 
Deoxidation, dehydrogenation, and fine adjustment of alloy elements are 
conducted. 
Replacement of (2) and (3) with ASEA-SKF (a vacuum refining apparatus) or 
VAD (an arc degassing apparatus) gives no influence on the effects of the 
invention. 
(4) Ingot Formation or Continuous Casting: 
Molten steel is allowed to set in an ingot case or by means of a continuous 
casting machine. It gives no influence on the effects of the invention 
which is adopted. The resulting ingot is then subjected to remelting. 
(5) VAR Method or ESR Method: 
The ingot is put in a Cu-made crucible in a non-contact state. A voltage is 
applied between the ingot and the crucible to remelt the ingot by the heat 
of an arc discharge. The technique in which the upper layer of the melt in 
the crucible is slag (oxides) is called an ESR method, while the technique 
in which the atmosphere above the melt is vacuum is called a VAR method. 
EXAMPLE 1 
The influence of the Cu content of the alloy steel on the water-resistant 
bearing life was examined. In order to make a clear distinction between 
comparative bearings A to J and bearings M to Y according to the 
invention, the former had a Cu content of less than 0.05 wt % while the 
latter had a Cu content ranging from 0.05 to 0.60 wt %. The alloy 
constituents of the steel, the steel making method adopted, the heat 
processing given to the bearing are shown in Table 1 below. The results of 
the water-resistant life test are also shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Rate of 
Heat Life 
Sample 
Alloy Steel Composition (wt %) Method of 
Processing 
Reduction 
No. C Si Mn P S Ni Cr Mo Cu Al Ti O Steel Making 
of Bearing 
(%) 
__________________________________________________________________________ 
Com- 
parative 
Bearing: 
A 0.10 
0.24 
0.49 
0.015 
0.003 
4.50 
1.04 
0.16 
0.01 
0.035 
0.003 
0.0015 
electric furnace 
carburizing 
97 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
B 0.10 
0.25 
0.49 
0.016 
0.002 
4.50 
1.04 
0.16 
0.04 
0.033 
0.003 
0.0006 
electric furnace 
carburizing 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
C 0.35 
0.25 
0.80 
0.015 
0.005 
0.01 
1.50 
1.10 
0.01 
0.033 
0.002 
0.0013 
electric furnace 
carbonitriding 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
D 0.33 
0.25 
0.81 
0.017 
0.008 
0.01 
1.49 
1.09 
0.04 
0.030 
0.002 
0.0013 
electric furnace 
carbonitriding 
95 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
E 0.21 
0.16 
0.40 
0.019 
0.005 
1.58 
0.35 
0.22 
0.01 
0.034 
0.003 
0.0014 
electric furnace 
carburizing 
95 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
F 0.22 
0.15 
0.40 
0.019 
0.005 
1.60 
0.35 
0.21 
0.04 
0.032 
0.003 
0.0014 
electric furnace 
carburizing 
94 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
G 0.45 
0.50 
1.50 
0.019 
0.005 
0.01 
1.26 
0.01 
0.01 
0.029 
0.003 
0.0011 
electric furnace 
carbonitriding 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
H 0.45 
0.49 
1.49 
0.018 
0.002 
0.02 
1.25 
0.01 
0.04 
0.029 
0.003 
0.0011 
electric furnace 
carbonitriding 
94 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
I 1.09 
0.24 
0.35 
0.016 
0.001 
0.06 
3.50 
0.01 
0.01 
0.025 
0.002 
0.0004 
electric furnace 
hardening 
97d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
J 1.10 
0.24 
0.36 
0.016 
0.007 
0.06 
3.50 
0.01 
0.04 
0.022 
0.002 
0.0012 
electric furnace 
hardening 
95d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
Rate of 
Heat Life 
Sample 
Alloy Constituents (wt %) Method of 
Processing 
Reduction 
No. C Si Mn P S Ni Cr Mo Cu Al Ti O Steel Making 
of Bearing 
(%) 
__________________________________________________________________________ 
Bearing of 
Invention: 
M 0.10 
0.24 
0.49 
0.011 
0.008 
4.50 
1.04 
0.16 
0.20 
0.035 
0.003 
0.0005 
electric furnace 
carburizing 
55 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
N 0.10 
0.25 
0.49 
0.016 
0.005 
4.50 
1.04 
0.16 
0.30 
0.033 
0.003 
0.0015 
electric furnace 
carburizing 
53 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
O 0.10 
0.25 
0.49 
0.022 
0.003 
4.49 
1.04 
0.16 
0.60 
0.033 
0.003 
0.0015 
electric furnace 
carburizing 
50 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
P 0.35 
0.25 
0.80 
0.015 
0.005 
0.01 
1.50 
1.09 
0.10 
0.033 
0.002 
0.0013 
electric furnace 
carbonitriding 
60 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
Q 0.33 
0.25 
0.81 
0.017 
0.005 
0.01 
1.49 
1.10 
0.30 
0.030 
0.002 
0.0013 
electric furnace 
carbonitriding 
59 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
R 0.21 
0.16 
0.40 
0.019 
0.004 
1.58 
0.35 
0.22 
0.25 
0.034 
0.003 
0.0014 
electric furnace 
carburizing 
51 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
S 0.22 
0.15 
0.40 
0.019 
0.005 
1.60 
0.36 
0.21 
0.40 
0.032 
0.003 
0.0014 
electric furnace 
carburizing 
58 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
T 0.45 
0.50 
1.50 
0.019 
0.007 
0.01 
1.26 
0.01 
0.05 
0.029 
0.003 
0.0011 
converter .fwdarw. 
carbonitriding 
61 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
U 0.45 
0.50 
1.49 
0.018 
0.005 
0.02 
1.25 
0.01 
0.15 
0.029 
0.003 
0.0011 
electric furnace 
carbonitriding 
59 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
V 1.10 
0.24 
0.35 
0.016 
0.006 
0.06 
3.50 
0.01 
0.05 
0.025 
0.002 
0.0012 
electric furnace 
hardening 
59d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
W 1.10 
0.24 
0.35 
0.016 
0.003 
0.06 
3.50 
0.01 
0.10 
0.022 
0.002 
0.0012 
electric furnace 
hardening 
53d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
X 1.10 
0.24 
0.35 
0.019 
0.005 
0.06 
3.50 
0.01 
0.30 
0.022 
0.002 
0.0012 
electric furnace 
hardening 
50d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
Y 1.09 
0.24 
0.35 
0.016 
0.007 
0.07 
3.50 
0.01 
0.60 
0.022 
0.002 
0.0009 
electric furnace 
hardening 
58d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
__________________________________________________________________________ 
As is apparent from the results in Table 1, the rate of life reduction of 
bearings M to Y according to the invention is significantly lower than 
that of comparative bearings A to J, proving that Cu is extremely 
effective on hydrogen-induced brittleness flaking. As an example of the 
hydrogen-induced brittleness flaking the flaking pattern of comparative 
bearing A is shown in FIG. 2. There can be seen a fracture having a 
pattern like annular rings due to crack development, indicating 
hydrogen-induced brittleness flaking. 
EXAMPLE 2 
Bearings were produced from alloy steel containing Nb or V to examine the 
influence of Nb or V on the rate of life reduction. Specifically, bearings 
Q.sub.1 to Q.sub.5 were prepared in the same manner as for bearing Q of 
Example 1, except for adding Nb or V to the basic alloy steel composition 
of bearing Q in a varied concentration, and tested in the same manner as 
in Example 1. 
The alloy constituents, the method of steel making, the former austenite 
crystal grain size, and the test results obtained are shown in Table 2 
below. The term "former austenite crystal grain size" as used herein means 
the crystal grain size of the austenite at the time of heating for 
carburizing and hardening, which is measured in accordance with JIS G0551. 
The larger the figure, the finer the grains. Austenite is converted to 
martensite upon hardening (quenching), but the crystal grains do not grow 
by hardening. Accordingly, the smaller the former austenite crystal 
grains, the smaller the martensite crystal grains. 
TABLE 2 
__________________________________________________________________________ 
Rate 
of 
Former 
Life 
Method Austen- 
Re- 
Sam- of Heat ite duc- 
ple 
Alloy Constituents (wt %) Steel 
Processing 
Grain 
tion 
No. 
C Si Mn P S Ni Cr Mo Cu Al Ti O Nb V Making 
of Bearing 
Size 
(%) 
__________________________________________________________________________ 
Q 0.33 
0.25 
0.81 
0.017 
0.005 
0.01 
1.49 
1.10 
0.30 
0.030 
0.002 
0.0013 
0.00 
0.00 
electric 
carbo- 
7 59 
Q.sub.1 
0.35 
0.25 
0.80 
0.022 
0.008 
0.01 
1.45 
1.09 
0.30 
0.029 
0.002 
0.0011 
0.05 
0.00 
furnace 
nitriding 
9 49 
Q.sub.2 
0.35 
0.24 
0.80 
0.012 
0.003 
0.02 
1.48 
1.10 
0.30 
0.031 
0.002 
0.0013 
0.10 
0.00 
.dwnarw. 
followed 
9 48 
Q.sub.3 
0.35 
0.24 
0.81 
0.015 
0.006 
0.01 
1.49 
1.09 
0.29 
0.027 
0.002 
0.0010 
0.20 
0.00 
LF by 9 47 
Q.sub.4 
0.34 
0.25 
0.81 
0.019 
0.006 
0.01 
1.49 
1.10 
0.29 
0.033 
0.002 
0.0008 
0.00 
0.10 
.dwnarw. 
hardening 
9 47 
Q.sub.5 
0.32 
0.27 
0.79 
0.009 
0.001 
0.01 
1.50 
1.07 
0.31 
0.034 
0.002 
0.0010 
0.00 
0.15 
RH and 9 47 
degassing 
tempering 
.dwnarw. 
ingot 
formation 
__________________________________________________________________________ 
While all the bearings Q to Q.sub.5 are in accordance with the present 
invention, it is seen that addition of Nb or V suppresses the reduction in 
life due to incorporation of water. Thus, since Nb or V makes the former 
austenite crystal grains finer thereby to provide more grain boundaries 
through which hydrogen atoms are allowed to pass. As a result, hydrogen 
gas is broadly delivered to as many inclusions, and hydrogen-induced 
brittleness flaking is retarded effectively. 
EXAMPLE 3 
Bearings were produced in the same manner as in Example 1 by using alloy 
steel containing Cu and Nb or V in varied concentrations through various 
methods of steel making to examine the total influence of the method of 
steel making on the rate of bearing life reduction. 
Specifically, comparative bearings C.sub.1 to C.sub.3 were prepared in the 
same manner as for comparative bearing C (Cu content: 0.01 wt %) prepared 
in Example 1, except for adding 0.15 wt % of Nb (bearing C.sub.1), adding 
0.15 wt % of V (bearing C.sub.2), or increasing the Cu content to 0.04 wt 
% and adding 0.15 wt % of V (bearing C.sub.3). Bearings C.sub.4 to C.sub.8 
according to the present invention were prepared in the same manner except 
for increasing the Cu content to a range of from 0.05 to 0.25 wt % and 
adding Nb or V in a concentration varying from 0 to 0.15 wt %. The alloy 
steel for these bearings was prepared by remelting according to a VAR 
method or an ESR method. 
The alloy constituents, the method of steel making, and the results of the 
life test are shown in Table 3 below. 
TABLE 3 
__________________________________________________________________________ 
Rate 
of 
Life 
Re- 
Heat duc- 
Sample 
Alloy Constituents (wt %) Method of 
Processing 
tion 
No. C Si Mn P S Ni Cr Mo Cu Al Ti O Nb V Steel Making 
of 
(%)ring 
__________________________________________________________________________ 
Com- 
parative 
Bearing: 
C.sub. 
0.35 
0.25 
0.80 
0.015 
0.005 
0.01 
1.50 
1.10 
0.01 
0.033 
0.002 
0.0013 
0.00 
0.00 
electric 
carburizing 
96 
furnace 
(ordarw. 
LF .fwdarw. 
carbo- 
ingot nitriding) 
formation 
followed 
VAR by 
C.sub.1 
0.33 
0.25 
0.80 
0.010 
0.002 
0.01 
1.50 
1.10 
0.01 
0.033 
0.002 
0.0004 
0.15 
0.00 
electric 
hardening 
96 
furnace 
anddarw. 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot 
formation .fwdarw. 
VAR 
C.sub.2 
0.35 
0.25 
0.80 
0.024 
0.004 
0.01 
1.50 
1.10 
0.01 
0.033 
0.002 
0.0015 
0.00 
0.15 
electric 95 
furnace .fwdarw. 
LF .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
C.sub.3 
0.35 
0.25 
0.80 
0.023 
0.008 
0.01 
1.50 
1.10 
0.04 
0.030 
0.002 
0.0014 
0.00 
0.15 
electric 95 
furnace .fwdarw. 
LF .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
Bearing 
of the 
Invention: 
C.sub.4 
0.35 
0.25 
0.83 
0.015 
0.005 
0.01 
1.49 
1.10 
0.05 
0.030 
0.002 
0.0015 
0.00 
0.00 
electric 
carburizing 
30 
furnace 
(ordarw. 
LF .fwdarw. 
carbo- 
ingot nitriding) 
formation 
followed 
ESR by 
C.sub.5 
0.35 
0.25 
0.79 
0.025 
0.008 
0.01 
1.47 
1.09 
0.10 
0.030 
0.002 
0.0013 
0.05 
0.00 
electric 
hardening 
28 
furnace 
anddarw. 
LF .fwdarw. 
tempering 
ingot 
formation .fwdarw. 
VAR 
C.sub.6 
0.35 
0.25 
0.80 
0.019 
0.005 
0.01 
1.48 
1.10 
0.25 
0.030 
0.002 
0.0012 
0.00 
0.05 
electric 27 
furnace .fwdarw. 
LF .fwdarw. RH 
degassing .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
C.sub.7 
0.35 
0.25 
0.78 
0.012 
0.001 
0.01 
1.50 
1.09 
0.25 
0.030 
0.002 
0.0014 
0.00 
0.15 
electric 24 
furnace .fwdarw. 
LF .fwdarw. 
ingot 
formation .fwdarw. 
VAR 
C.sub.8 
0.35 
0.25 
0.81 
0.017 
0.002 
0.01 
1.46 
1.10 
0.25 
0.030 
0.002 
0.0014 
0.15 
0.00 
electric 23 
furnace .fwdarw. 
LF .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
__________________________________________________________________________ 
In Table 3, the rates of life reduction of bearings C.sub.4 to C.sub.8 are 
significantly lower than those of comparative bearings C to C.sub.3 and 
even considerably lower than those of bearings M to Y and Q to Q.sub.5 
according to the present invention shown in Tables 1 and 2. From these 
results it is seen that a VAR method or an ESR method as a steel making 
method is very effective on hydrogen-induced brittleness flaking provided 
that the alloy steel contains at least 0.05 wt % of Cu. This is because 
these remelting methods provide steel which has a metallurgically uniform 
structure with reduced segregation and therefore has improved corrosion 
resistance. Such steel undergoes reduced evolution of hydrogen on the 
surface thereof and thereby retards occurrence of hydrogen-induced 
brittleness flaking. 
FIG. 3 is the plot of rate of life reduction vs. Cu concentration in the 
alloy steel used in the invention. A-J, M-Y, and C.sub.4 to C.sub.8 
indicate the bearings prepared above. FIG. 3 clearly shows that it makes a 
dramatic difference in rate of life reduction whether the Cu concentration 
is less or not less than 0.05 wt %. 
If the Cu content is 0.04 wt % or less, no effect on hydrogen-induced 
brittleness flaking is recognized even if the alloy steel contains Nb or V 
or even if a VAR method or an ESR method is adopted, as can be concluded 
from the results of comparative bearings C to C.sub.3. In addition, if 
there is no difference in Cu content (Cu content being fixed at 0.25 wt 
%), the rate of life reduction tends to be lowered according as the Nb or 
V content increases, as can be seen from the results of bearings C.sub.6 
to C.sub.8. 
Comparative bearing C.sub.1 was designed to aim at reduction in rate of 
life reduction through purification of raw material, i.e., reduction of 
oxygen and sulfur concentrations. However, no effect was exerted in the 
presence of water. 
In Examples 4 to 7 hereinafter described, bearings were produced in the 
same manner as in Examples 1 to 3, except for replacing Ti as an alloy 
constituent with N, and tested under the same conditions as in Examples 1 
and 3, except for increasing the radial load to 40000 N and the axial load 
to 17544 N. 
When the water-resistant life test is conducted under the above conditions, 
because the condition of stress corrosion becomes the strictest on the 
stress-loaded site (part subjected to highest load) of the outer race, it 
is the outer race that suffers damage. Therefore, all the bearings tested, 
either comparative bearings or the bearings of the invention, had a common 
inner race and common conical rollers. Specifically, all the inner races 
were the same as in sample C.sub.0 shown in Table 4 below and all the 
rollers were the same as in sample G.sub.0 shown in Table 4 in terms of 
material, method of steel making, and heat processing. 
EXAMPLE 4 
The influence of Cu and P contents on the water-resistant bearing life was 
examined. In order to make a clear distinction between comparative 
bearings and the bearings of the invention, the Cu content of comparative 
bearings (A.sub.0 to L.sub.0) was set less than 0.05 wt %, while that of 
bearings of the invention (M.sub.1 to Y.sub.1) was in the range of from 
0.05 to 0.60 wt %. On the other hand, the P content of the former ranged 
from 0.015 to 0.030 wt %, while that of the latter ranged from 0.030 to 
0.150 wt %. 
The alloy constituents, the method of steel making and the heat processing 
of the outer race, and the results of the life test are shown in Tables 4 
and 5 below. 
TABLE 4 
__________________________________________________________________________ 
Rate of 
Heat Life 
Sample 
Alloy Steel Composition (wt %) Method of 
Processing 
Reduction 
No. C Si Mn P S Ni Cr Mo Cu Al N O Steel Making 
of Bearing 
(%) 
__________________________________________________________________________ 
Com- 
parative 
Bearing: 
A.sub.0 
0.10 
0.24 
0.49 
0.015 
0.003 
4.50 
1.04 
0.16 
0.01 
0.035 
0.010 
0.0015 
electric furnace 
carburizing 
97 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
B.sub.0 
0.10 
0.25 
0.49 
0.016 
0.002 
4.50 
1.04 
0.16 
0.04 
0.033 
0.010 
0.0006 
electric furnace 
carburizing 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
C.sub.0 
0.35 
0.25 
0.80 
0.015 
0.005 
0.01 
1.50 
1.10 
0.01 
0.033 
0.010 
0.0013 
electric furnace 
carbonitriding 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
D.sub.0 
0.33 
0.25 
0.81 
0.017 
0.008 
0.01 
1.49 
1.09 
0.04 
0.030 
0.010 
0.0013 
electric furnace 
carbonitriding 
95 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
E.sub.0 
0.21 
0.16 
0.40 
0.019 
0.005 
1.58 
0.35 
0.22 
0.01 
0.034 
0.010 
0.0014 
electric furnace 
carburizing 
95 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
F.sub.0 
0.22 
0.15 
0.40 
0.019 
0.005 
1.60 
0.35 
0.21 
0.04 
0.032 
0.010 
0.0014 
electric furnace 
carburizing 
94 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
G.sub.0 
0.45 
0.50 
1.50 
0.019 
0.005 
0.01 
1.26 
0.01 
0.01 
0.029 
0.010 
0.0011 
electric furnace 
carbonitriding 
96 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
H.sub.0 
0.45 
0.49 
1.49 
0.018 
0.002 
0.02 
1.25 
0.01 
0.04 
0.029 
0.010 
0.0011 
electric furnace 
carbonitriding 
94 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
I.sub.0 
1.09 
0.24 
0.35 
0.016 
0.001 
0.06 
3.50 
0.01 
0.01 
0.025 
0.010 
0.0004 
electric furnace 
hardening 
97d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
J.sub.0 
1.10 
0.24 
0.36 
0.016 
0.007 
0.06 
3.50 
0.01 
0.04 
0.022 
0.010 
0.0012 
electric furnace 
hardening 
95d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
K.sub.0 
0.10 
0.24 
0.49 
0.029 
0.003 
4.50 
1.04 
0.16 
0.01 
0.035 
0.010 
0.0015 
electric furnace 
carburizing 
80 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
L.sub.0 
0.10 
0.24 
0.49 
0.030 
0.003 
4.50 
1.04 
0.16 
0.04 
0.035 
0.010 
0.0015 
electric furnace 
carburizing 
80 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
__________________________________________________________________________ 
TABLE 5 
__________________________________________________________________________ 
Rate of 
Heat Life 
Sample 
Alloy Steel Composition (wt %) Method of 
Processing 
Reduction 
No. C Si Mn P S Ni Cr Mo Cu Al N O Steel Making 
of Bearing 
(%) 
__________________________________________________________________________ 
Bearing 
of the 
Invention: 
M.sub.1 
0.10 
0.24 
0.49 
0.030 
0.008 
4.50 
1.04 
0.16 
0.05 
0.035 
0.010 
0.0005 
electric furnace 
carburizing 
55 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
N.sub.1 
0.10 
0.25 
0.49 
0.030 
0.005 
4.50 
1.04 
0.16 
0.30 
0.034 
0.010 
0.0015 
electric furnace 
carburizing 
53 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
O.sub.1 
0.10 
0.25 
0.49 
0.030 
0.003 
4.49 
1.04 
0.16 
0.60 
0.033 
0.010 
0.0015 
electric furnace 
carburizing 
50 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
P.sub.1 
0.35 
0.25 
0.80 
0.100 
0.005 
0.01 
1.50 
1.09 
0.10 
0.030 
0.010 
0.0013 
electric furnace 
carbonitriding 
60 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
Q.sub.1 
0.33 
0.25 
0.81 
0.100 
0.005 
0.01 
1.49 
1.10 
0.30 
0.030 
0.010 
0.0013 
electric furnace 
carbonitriding 
59 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
R.sub.1 
0.21 
0.16 
0.40 
0.150 
0.004 
1.58 
0.35 
0.22 
0.25 
0.034 
0.010 
0.0014 
electric furnace 
carburizing 
51 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
S.sub.1 
0.22 
0.15 
0.40 
0.150 
0.005 
1.60 
0.36 
0.21 
0.40 
0.032 
0.010 
0.0014 
electric furnace 
carburizing 
58 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
ingot formation 
tempering 
T.sub.1 
0.45 
0.50 
1.50 
0.060 
0.007 
0.01 
1.26 
0.01 
0.05 
0.029 
0.010 
0.0011 
converter .fwdarw. 
carbonitriding 
61 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
U.sub.1 
0.45 
0.50 
1.49 
0.060 
0.005 
0.02 
1.25 
0.01 
0.15 
0.029 
0.010 
0.0011 
electric furnace 
carbonitriding 
59 
LF .fwdarw. RH 
followed by 
degassing .fwdarw. 
hardening and 
continuous casting 
tempering 
V.sub.1 
1.10 
0.24 
0.35 
0.120 
0.006 
0.06 
3.50 
0.01 
0.05 
0.025 
0.010 
0.0012 
electric furnace 
hardening 
59d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
W.sub.1 
1.10 
0.24 
0.35 
0.120 
0.003 
0.06 
3.50 
0.01 
0.10 
0.022 
0.010 
0.0012 
electric furnace 
hardening 
53d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
X.sub.1 
1.10 
0.24 
0.35 
0.120 
0.005 
0.10 
3.50 
0.01 
0.30 
0.022 
0.010 
0.0012 
electric furnace 
hardening 
50d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
Y.sub.1 
1.09 
0.24 
0.35 
0.120 
0.007 
0.30 
3.50 
0.01 
0.60 
0.022 
0.010 
0.0009 
electric furnace 
hardening 
58d 
LF .fwdarw. RH 
tempering 
degassing .fwdarw. 
ingot formation 
__________________________________________________________________________ 
It can be seen from the results in Tables 4 and 5 that the rates of life 
reduction of bearings M.sub.1 to Y.sub.1 according to the invention are 
markedly lower than those of comparative bearings A.sub.0 to L.sub.0, 
proving the significant effect of Cu and P on hydrogen-induced brittleness 
flaking. 
The plot of rate of life reduction against Cu concentration is shown in 
FIG. 4, and the plot of rate of life reduction vs. P concentration in FIG. 
5. These plots clearly reveal that whether the Cu concentration is less or 
not less than 0.05 wt % and whether the P concentration is less or not 
less than 0.030 wt % make a dramatic difference in rate of life reduction. 
In addition, there figures reveal that the rate of life reduction was 
almost invariable in the cases where the Cu concentration was in the range 
of 0.10 to 0.60 wt % or where the P concentration was in the range of 0.04 
to 0.150 wt %. 
That is, Tables 4 and 5 and FIGS. 4 and 5 show that the bearings of the 
invention have a significantly reduced rate of life reduction in the 
presence of water as compared with the comparative bearings, thus proving 
the great effects of Cu and P on hydrogen-induced brittleness flaking of a 
bearing. 
Table 6 shows the hydrogen concentrations in the stress loaded site (part 
subjected to highest load) and non-loaded site (part subjected to lowest 
load) of the outer race after the above life test was conducted for 
consecutive 70 hours. 
TABLE 6 
______________________________________ 
Hydrogen Concentration 
After 70-Hour Testing 
Stress-loaded 
Stress-Non- 
Site loaded Site 
Outer Race (ppm) (ppm) 
______________________________________ 
Comparative Bearing 
3.2 0.6 
C.sub.0 
Bearing of Invention 
0.9 0.6 
P.sub.1 
______________________________________ 
The hydrogen concentration in the stress-loaded site of the outer race of 
the bearing P.sub.1 according to the invention, though higher than in the 
non-loaded site because of entrance and diffusion of hydrogen therein, is 
lower than that in the stress-loaded site of the comparative bearing 
C.sub.0. It is thus seen that hydrogen hardly enters and diffuses in the 
outer race of the bearing of the invention and that Cu and P are effective 
in preventing hydrogen entrance. 
EXAMPLE 5 
Bearings Q.sub.10 to Q.sub.15 according to the present invention and 
comparative bearings Z.sub.1 and Z.sub.2 were produced using alloy steel 
basically having the same composition as used in bearing Q.sub.1 of 
Example 4 except for containing Al, N, Nb or V in varied concentrations 
and tested to examine the influences of these elements on the former 
austenite crystal grain size (JIS G0551) and the rate of life reduction in 
the presence of water. The alloy constituents, the method of steel making, 
the heat processing, the former austenite crystal grain size, and the 
results of the life test are shown in Table 7 below. 
TABLE 7 
__________________________________________________________________________ 
Rate 
of 
Former 
Life 
Method Austen- 
Re- 
Sam- of Heat ite duc- 
ple 
Alloy Steel Composition (wt %) Steel 
Processing 
Grain 
tion 
No. 
C Si Mn P S Ni Cr Mo Cu Al N O Nb V Making 
of Bearing 
Size 
(%) 
__________________________________________________________________________ 
Comparative Bearing: 
Z.sub.1 
0.33 
0.25 
0.80 
0.100 
0.005 
0.01 
1.50 
1.10 
0.30 
0.010 
0.002 
0.0012 
0.00 
0.00 
(common) 
(common) 
3 90 
Z.sub.2 
0.34 
0.25 
0.79 
0.101 
0.004 
0.01 
1.49 
1.10 
0.30 
0.019 
0.004 
0.0010 
0.00 
0.00 
electric 
carbo- 
5 80 
Bearing of the Invention: furnace 
nitriding 
Q.sub.10 
0.33 
0.26 
0.80 
0.101 
0.005 
0.01 
1.50 
1.10 
0.30 
0.020 
0.005 
0.0010 
0.00 
0.00 
.dwnarw. 
.dwnarw. 
7 60 
Q.sub.1 
0.33 
0.25 
0.81 
0.100 
0.005 
0.01 
1.49 
1.10 
0.30 
0.030 
0.010 
0.0013 
0.00 
0.00 
LF hardening 
8 54 
Q.sub.11 
0.35 
0.25 
0.80 
0.022 
0.008 
0.01 
1.45 
1.09 
0.30 
0.060 
0.015 
0.0011 
0.00 
0.00 
.dwnarw. 
and 8 50 
Q.sub.12 
0.35 
0.24 
0.80 
0.012 
0.003 
0.01 
1.48 
1.10 
0.30 
0.031 
0.010 
0.0013 
0.10 
0.00 
RH tempering 
9 44 
Q.sub.13 
0.35 
0.24 
0.81 
0.015 
0.006 
0.01 
1.49 
1.09 
0.29 
0.027 
0.010 
0.0010 
0.20 
0.00 
degassing 10 39 
Q.sub.14 
0.34 
0.25 
0.81 
0.019 
0.006 
0.0l 
1.49 
1.10 
0.29 
0.033 
0.010 
0.0008 
0.00 
0.10 
.dwnarw. 9 45 
Q.sub.15 
0.32 
0.27 
0.79 
0.009 
0.001 
0.01 
1.50 
1.07 
0.31 
0.034 
0.010 
0.0010 
0.00 
0.20 
ingot 10 40 
formation 
__________________________________________________________________________ 
Table 7 shows that all the bearings Q.sub.1 and Q.sub.10 to Q.sub.15 of the 
present invention which contain not less than 0.02 wt % of Al and not less 
than 0.005 wt % of N have a greatly lowered rate of life reduction in the 
presence of water than comparative bearings Z.sub.1 and Z.sub.2. It is 
also seen, comparing the bearings of the present invention, that bearings 
Q.sub.12 to Q.sub.15 containing Nb or V have a still lowered rate of life 
reduction in the presence of water than bearings Q.sub.1 Q.sub.10 or 
Q.sub.11 containing neither Nb nor V. Al, N, Nb and V each make former 
austenite crystal grains finer to provide more grain boundaries through 
which hydrogen atoms are allowed to pass. Therefore, among the alloys 
having almost the same content in terms of Cu content, the Al content or 
the N content, as the Nb or V content increases, hydrogen gas is made to 
be delivered to many inclusions. Nb or V is thus effective in retarding 
hydrogen-induced brittleness flaking. 
EXAMPLE 6 
Bearings were prepared from alloy steel which had varied Cu and P contents 
and was produced by a varied method of steel making to examine the 
influences of these factors on the rate of life reduction. 
Comparative bearings were prepared from alloy steel basically having the 
same composition as used in comparative bearing C.sub.0 of Example 4 (Cu: 
0.35 wt %; P: 0.015 wt %), except for slightly changing the Al and N 
contents (comparative bearing C.sub.10) or decreasing the P content to 
0.010 wt % and adding 0.15 wt % of Nb (comparative bearing C.sub.11). 
Bearings of the invention C.sub.12 and C.sub.13 were prepared using the 
same basic composition except for changing the Cu content to 0.25 wt % or 
0.24 wt %, respectively, and extremely increasing the P content to 0.100 
wt % to distinguish them from the comparative bearings. 
The alloy steel was prepared by either a VAR method or an ESR method. 
The alloy constituents, the method of steel making, and the results of the 
life test are shown in Table 8 below. 
TABLE 8 
__________________________________________________________________________ 
Rate of 
Heat Life 
Sample 
Alloy Steel Composition (wt %) Method of 
Processing 
Reduction 
No. C Si Mn P S Ni Cr Mo Cu Al N O Nb V Steel Making 
of 
(%)ring 
__________________________________________________________________________ 
Comparative Bearing: 
C.sub.10 
0.35 
0.25 
0.80 
0.015 
0.005 
0.10 
1.50 
1.10 
0.01 
0.030 
0.006 
0.0013 
0.00 
0.00 
electric 
(common) 
95 
furnace .fwdarw. 
carbo- 
LF .fwdarw. 
nitriding 
ingot .dwnarw. 
formation 
hardening 
VAR and 
C.sub.11 
0.35 
0.25 
0.80 
0.010 
0.002 
0.10 
1.50 
1.10 
0.01 
0.031 
0.010 
0.0004 
0.15 
0.00 
electric 
tempering 
96 
furnace .fwdarw. 
LF .fwdarw. RH 
degas- 
sing .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
Bearing of Invention: 
C.sub.12 
0.35 
0.25 
0.80 
0.10 
0.004 
0.10 
1.50 
1.10 
0.25 
0.033 
0.011 
0.0015 
0.00 
0.00 
electric 15 
furnace .fwdarw. 
LF .fwdarw. RH 
degas- 
sing .fwdarw. 
ingot 
formation .fwdarw. 
ESR 
C.sub.13 
0.35 
0.25 
0.80 
0.10 
0.008 
0.10 
1.50 
1.10 
0.24 
0.030 
0.009 
0.0014 
0.00 
0.00 
electric 14 
furnace .fwdarw. 
LF .fwdarw. 
ingot 
formation .fwdarw. 
VAR 
__________________________________________________________________________ 
As is shown in Table 8, the rates of life reduction of bearings C.sub.12 
and C.sub.13 according to the invention are distinctly lower than those of 
comparative bearings C.sub.10 and C.sub.11 and still lower than those of 
bearings M.sub.1 to Y.sub.1 of the invention shown in Table 5 and Q.sub.1 
and Q.sub.10 to Q.sub.15 of the invention shown in Table 7. These results 
reveal that the remelting method, i.e, a VAR method or an ESR method, is 
very effective on hydrogen-induced brittleness flaking as far as the Cu 
and P content satisfy the conditions specified in the present invention. 
This is because the steel prepared by the remelting method has a uniform 
structure with suppressed segregation and is therefore inhibited from 
corrosion. The amount of hydrogen evolved on the surface of such steel can 
thus be reduced, resulting in retardation of hydrogen-induced brittleness 
flaking. 
If the Cu content is 0.04 wt % or less, no effect on hydrogen-induced 
brittleness flaking is recognized even if the alloy steel contains Nb or V 
or even if a VAR method or an ESR method is adopted, as can be concluded 
from the results of comparative bearings C.sub.10 and C.sub.11. 
Comparative bearing C.sub.11 was designed to aim at reduction in rate of 
life reduction through purification of raw material, i.e., reduction of 
oxygen and sulfur concentrations. However, no effect was exerted in the 
presence of water. 
While the invention has been described in detail and with reference to 
specific examples thereof, it will be apparent to one skilled in the art 
that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.