Case-Hardened 20CrMnTi NATR Series Yoke Type Support Rollers: Chosen for shock loading and for heavy ring sections, where a tough core resists the cracking a fully through-hardened section would not survive. The material decides the corrosion behavior — none of its own; protected in service exactly as through-hardened bearing steel is and the temperature the part will stand (similar to through-hardened rings — about +120 °C without special stabilization), and it is the reason the alternatives below exist. Properties, limits and the full size table follow.
Why Case-Hardened 20CrMnTi for NATR Series Yoke Type Support Rollers
Chosen for shock loading and for heavy ring sections, where a tough core resists the cracking a fully through-hardened section would not survive. In a natr series yoke type support rollers it is the steel of the rings and, in most designs, of the rolling elements.
Carburizing puts the hardness where the rolling contact is and leaves the core tough, so the ring can absorb shock and heavy section stresses that would crack a through-hardened ring. It is the usual choice for large roller bearing rings and for anything that gets hit rather than merely loaded.
Material Properties
| Grade designation | 20CrMnTi (GB/T 3077), of the same class as 20MnCr5 and SAE 8620 — carburized to a hard case over a tough, unhardened core |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | Similar to through-hardened rings — about +120 °C without special stabilization |
| Corrosion characteristic | None of its own; protected in service exactly as through-hardened bearing steel is |
Service Limits
The case has a depth, and that depth is a design limit: load high enough and the maximum shear stress moves below the hardened case into the softer core, where the surface then collapses. That is why case depth is specified against the rolling element size and the load, and why a case-hardened ring is not simply a tougher version of a through-hardened one.
What the Material Changes About the Bearing
The material does not change the envelope: the bore, the outside diameter, the width and the corner radius stay exactly as the boundary dimension standard fixes them, so the bearing is interchangeable with any other bearing of the same designation. What it changes is what happens inside the contact — the fatigue behavior, the tolerance of shock, and the temperature at which the ring stops being dimensionally stable.
Sizes of NATR Series Yoke Type Support Rollers Available in Case-Hardened 20CrMnTi
| Designation | Bore d (mm) | Outer diameter D (mm) | Width C (mm) |
|---|---|---|---|
| NATR5 | 5 | 16 | 12 |
| NATR6 | 6 | 19 | 12 |
| NATR8 | 8 | 24 | 15 |
| NATR10 | 10 | 30 | 15 |
| NATR12 | 12 | 32 | 15 |
| NATR15 | 15 | 35 | 19 |
| NATR17 | 17 | 40 | 21 |
| NATR20 | 20 | 47 | 25 |
| NATR25 | 25 | 52 | 25 |
| NATR30 | 30 | 62 | 29 |
| NATR35 | 35 | 72 | 29 |
| NATR40 | 40 | 80 | 32 |
