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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 | ― | |
| Ｙ | ― | ― | ― | ― | 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 |