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Product/technological information

3. Bearing Materials

For the material of the outer ring, inner ring and balls, high-carbon chromium bearing steel treated with vacuum degassing is used in order to improve the torque and noise level, as well as to extend the bearing life. Also, martensitic stainless steel is used to meet corrosion-resistant requirements.

Chemical Composition of Bearing Materials

Material High Carbon Chromium Bearing Steel Stainless Steel Ceramic
Components Inner ring, outer ring, balls Inner ring, outer ring Balls Balls
Symbol SUJ2 KS440
(QD51,ACD34)
SUS440C ACD34
(Note 1)
Si3N4
Chemical composition
(Weight %)
C 0.95 - 1.10 0.60 - 0.75 0.95 - 1.20 0.60 - 0.75
Si 0.15 - 0.35 ≦1.00 ≦1.00 ≦1.00
Mn ≦0.50 ≦1.00 ≦1.00 ≦1.00
P ≦0.025 ≦0.030 ≦0.040 ≦0.030
S ≦0.025 ≦0.020 ≦0.030 ≦0.020
Cr 1.30 - 1.60 11.5 - 13.5 16.0 - 18.0 11.5 - 13.5
Mo ≦0.08 ≦0.30 ≦0.75 ≦0.30
Ni ≦0.25 ≦0.60 ≦0.60
Cu ≦0.25 ≦0.20 ≦0.20
V ≦0.15 ≦0.15
3.0 - 4.0
Al 3.2 - 4.2
Ti 0.5 - 1.0
Hardness HRC 60 - 64(Inner ring, outer ring)
62 - 67(Balls)
58 - 62 59 - 66 HV 1300 - 2000
Similar steel grades (outside Japan) SAE52100、100Cr6、ASTM52100、BS535A99、1.3505 X65Cr13、1.4037 SAE51440C、
AISI440C、
X102CrMo17、
X105CrMo17、
1.4125、1.3543
X65Cr13、1.4037

Note 1: Used for ball diameters of 0.500mm and 0.635mm.

Materials and Characteristics

Material Raceways and balls High carbon chromium bearing steel Stainless steel
Cages Low carbon steel plate (SPCC),
stainless steel plate (SUS304、SUS420J2)
Polyamide (66 nylon), etc. Stainless steel plate (SUS304、SUS420J2),
polyamide (66 nylon), etc.
Shields Low carbon steel plate (SPCC, SECC-NC),
stainless steel plate (SUS304)
Stainless steel plate (SUS304)
Seals Rubber (Nitrile rubber (NBR), fluoro rubber (FKM)) + core plate (SPCC-NP, SECC-NC), PTFE
Characteristics Operating temperature 120 ºC or less
(* Up to a maximum of 300 ºC is possible depending on the dimensional stabilization treatment and/or other specifications)
Dynamic load rating High About 85% of bearing steel
Static load rating High About 80% of bearing steel
Friction torque Low Slightly higher than bearing steel
Application For general use & high precision For high-speed For corrosion resistance

Physical and Mechanical Properties of Materials

Materials Specific Gravity Coefficient of Linear Expansion
(1/ºC),
[0-100 ºC]
Hardness
(Brinell: HB)
Young's Modulus
(Mpa)
〔kgf/mm2
Tensile Strength
(Mpa)
〔kgf/mm2
Yield Point
(Mpa)
〔kgf/mm2
Elongation
(%)
SUJ2 7.83 12.5×10-6 650 - 740 208000
〔21200〕
1570 - 1960
〔160 - 200〕
- -
KS440 7.70 10.3×10-6 580 210000
〔21400〕
1900
〔194〕
- -
SUS440C 7.68 10.1×10-6 580 200000
〔20400〕
1960
〔200〕
1860
〔190〕
-
SUS420J2 7.75 10.4×10-6 400 200000
〔20400〕
1650
〔168〕
1440
〔147〕
12
SUS304 7.93 17.3×10-6 150 193000
〔19700〕
510 - 657
〔52 - 67〕
510 - 656
〔21 - 32〕
50 - 60
Mild steel
(C=0.12 - 0.2%)
7.86 11.6×10-6 100 - 130 208000
〔21200〕
373 - 471
〔38 - 48〕
216 - 294
〔22 - 30〕
24 - 36
Hard steel
(C=0.3 - 0.5%)
7.84 11.3×10-6 160 - 200 205000
〔20900〕
539 - 686
〔55 - 70〕
333 - 451
〔34 - 46〕
14 - 26
Cast iron Gray iron
FC20
7.30 10.4×10-6 160 - 180 98100
〔10000〕
167 - 265
〔17 - 27〕
- -
Spheroidal graphite cast iron
FCD40
7.00 11.7×10-6 120 - 190 392 or more
〔40〕
12 or more
Copper 8.93 16.2×10-6 50 123000
〔12500〕
196
〔20〕
69
〔7〕
15 - 20
Brass (Annealed) 8.50 19.1×10-6 About 45 103000
〔10500〕
294 - 343
〔30 - 35〕
- 65 - 75
(Machined) 85 - 130 363 - 539
〔37 - 55〕
15 - 50
Zinc 7.14 31.0×10-6 30 - 60 92000
〔9400〕
147
〔15〕
- 30 - 40
Aluminum 2.69 23.7×10-6 15 - 26 70600
〔7200〕
78
〔8〕
34
〔3.5〕
35
Ceramic
(Si3N4)
3.20 (2.5 - 3.3)×10-6 HV 1300 - 2000 245000 - 314000
〔25000 - 32000〕
- - -

Comparison Table of SI, CGS and Engineering Units

Length Mass Time Temperature Acceleration Force Stress Pressure Energy Power
SI m kg s K m/s2 N Pa Pa J W
CGS System cm g s Gal dyn dyn/cm2 dyn/cm2 erg erg/s
Engineering Unit System m kgf・s2/m s m/s2 kgf kgf/m2 kgf/m2 kgf・m kgf・m/s

Prefixes of SI Units

Multiples Prefix Symbols
1018 Exa E
1015 Peta P
1012 Tera T
109 Giga G
106 Mega M
103 Kilo k
102 Hecto h
101 Deca da
10-1 Deci d
10-2 Centi c
10-3 Milli m
10-6 Micro μ
10-9 Nano n
10-12 Pico p
10-15 Femto f
10-18 Ato a