Materials of Bearings
The materials of the race and ball of bearing require sufficient hardness to meet the following qualities:
- High fatigue strength to resist repeated stress and prevent fatigue fracture of the race surface, which governs the life of the bearings.
- High elastic limit and yield strength to prevent deformation when subjected to a large load per unit area.
- High abrasion resistance to withstand sliding friction between the retainer and the ball.
- High strength to resist cracking due to impact load and failures caused by improper fitting, etc.
- Minimal secular change in dimension and shape due to changes in structure or internal stress.
GCr15 Steel <JIS G4805> (High carbon chromium bearing steel) meets these requirements comparatively well, and its chemical composition is shown in the following table.
Chemical Composition of High Carbon Chromium Bearing Steel
| Class | Standard | Symbol | Chemical Composition (%) |
|---|---|---|---|
| C | |||
| 1 | GB | GCr15 | 0.98-1.10 |
| DIN | 100Cr6 | – | |
| ASTM | E5200 | – | |
| JIS | SUJ2 | – | |
| 2 | GB | 9Cr18 | 0.98-1.10 |
| DIN | X105CrMO17 | – | |
| ASTM | 440C | – | |
| JIS | SUC440C | – |
To maintain uniform material quality, TRQ is fully equipped with installations and performs strict acceptance tests and inspections based on stringent acceptance standards in addition to JIS standards.
The types of tests conducted at TRQ primarily include chemical analysis, magnetic exploration, ultrasonic exploration, corrosion by strong acid, visual inspection, microscopic inspection, crusher test, and hardness test, among others.
- Materials of the Cage and the Rivet
The material of the cage is JIS G3141 (Cold rolled carbon steel sheet and strip) SPCC, and it is formed by pressing. The material of the rivet is JIS G3507 (Low carbon steel wire rods) SWRCH 12A.
- Materials of Housings
The material of the housings is FC200 JIS G5501 (Gray iron casting) and the mechanical properties are shown in the following table.
Mechanical Properties of Gray Cast Iron HT200
| Symbol | Thickness (mm) | Dia. of Testing Bar (mm) | Tension Test (kgf/mm²) | Traverse Breaking Test (kgf/mm) | Deflection (mm) | Pressure Strength (kgf/mm²) | Hardness (HB) |
|---|---|---|---|---|---|---|---|
| HT200 | Over 6-8 | 13 | Over 23 | 53 | 1.8 | 75 | 187-255 |
| Over 8-15 | 20 | Over 22 | 45 | 2.5 | 75 | 170-241 | |
| Over 15-30 | 30 | Over 20 | 40 | 2.5 | 75 | 170-241 | |
| Over 30-50 | 45 | Over 17 | 34 | 3.0 | 75 | 170-241 | |
| Over 50 | 60 | Over 16 | 31 | 4.5 | 75 | 163-229 |
Other Materials of Housings
| Symbol | JIS Number |
|---|---|
| FCD40 (QT400) | JIS G5502 |
| SPCC (08) | JIS G3141 |
| SUS304 | JIS G4304 |
- Materials of Other Components
| Components | Materials Used | JIS Symbols | JIS Number |
|---|---|---|---|
| Sleeve for adapter | Carbon steel for machine structural use | S25C | JIS G4051 |
| Nut for adapter | Carbon steel for machine structural use | S25C | JIS G4051 |
| Washer for adapter | Cold rolled carbon steel sheet and strip | SPCC | JIS G3141 |
| Oil seal | Synthetic nitrile rubber | – | – |
| Slinger | Cold rolled carbon steel sheet and strip | SPCC | JIS G3141 |
| Hexagon set screw | Nickel chromium molybdenum steel | SCM 435 | JIS G4105 |
| Hexagon wrench key | Nickel chromium molybdenum steel | SNCM630 | JIS G4103 |
| Grease nipple | Free cutting brass bar | C3604 | JIS H3250 |
