In a kr series stud type track rollers, GCr15 Bearing Steel is the steel of the rings and, in most designs, of the rolling elements. The grade is GCr15 (GB/T 18254) = 100Cr6 (1.3505) = SAE 52100, through-hardened to 58–64 HRC; it is magnetic, and its usable service range is to about +120 °C as normally heat stabilized; stabilized rings (S1, S2 and above) extend the limit in steps to around +250 °C. This page covers what the material changes about the bearing, the limits it brings with it, and the sizes supplied.
Why GCr15 Bearing Steel for KR Series Stud Type Track Rollers
The default material for the rings and rolling elements of virtually every standard rolling bearing. In a kr series stud type track rollers it is the steel of the rings and, in most designs, of the rolling elements.
Through-hardened high-carbon chromium steel is what a raceway is: hard enough to resist the rolling contact stress, clean enough after modern vacuum degassing that the inclusions which start fatigue cracks are rare, and dimensionally stable after tempering so the ground bore stays the size it was ground to.
Material Properties
| Grade designation | GCr15 (GB/T 18254) = 100Cr6 (1.3505) = SAE 52100, through-hardened to 58–64 HRC |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | To about +120 °C as normally heat stabilized; stabilized rings (S1, S2 and above) extend the limit in steps to around +250 °C |
| Corrosion characteristic | None of its own — the ground surfaces are bare hardened steel and depend on the lubricant, the seals and the preservative for protection |
Service Limits
The limit that catches people is dimensional stability, not hardness: a standard bearing is heat stabilized for use to about +120 °C, and running it hotter lets the rings grow and lose their fit. Above that a stabilized ring — S1, S2 and upward — is ordered specifically, and it comes with a small reduction in hardness and therefore in rating. The steel also has no corrosion resistance of its own: the preservative it ships with is not a coating, and a bearing stored in a damp store rusts on its raceways before it is ever fitted.
Alternatives and When to Switch
Move to case-hardened steel where the ring section is heavy or the load is shocked; to 440C where the environment is wet or the part must not rust; and to a hybrid bearing with ceramic balls where the speed, the electrical environment or the lubrication regime is beyond what a steel ball will tolerate.
Sizes of KR Series Stud Type Track Rollers Available in GCr15 Bearing Steel
| Designation | Stud thread | Roller outer diameter D (mm) | Roller width C (mm) | Stud diameter (mm) |
|---|---|---|---|---|
| KR16 | M6 | 16 | 11 | 6 |
| KR19 | M8 | 19 | 11 | 8 |
| KR22 | M10 | 22 | 12 | 10 |
| KR26 | M10 | 26 | 12 | 10 |
| KR30 | M12 | 30 | 14 | 12 |
| KR32 | M12 | 32 | 14 | 12 |
| KR35 | M16 | 35 | 18 | 16 |
| KR40 | M16 | 40 | 18 | 16 |
| KR47 | M20 | 47 | 24 | 20 |
| KR52 | M20 | 52 | 24 | 20 |
