A roll neck bearing is the largest concentration of load per millimetre in any industry, and chrome steel is still the only practical answer. Steel & Metallurgy duty is very high load, heat and cooling water washing the grease out; the material is what decides whether the bearing survives it.
| Industry duty | rolling force with heavy axial component, 60–200 °C at the roll neck |
|---|---|
| Typical media | mill scale, cooling water, grease |
| Housing temperature | 60 to +200 °C |
| Material and grade | through-hardened chrome steel — 100Cr6 / 52100 |
| Hardness | 59–65 HRC |
| Temperature ceiling | 120 °C (200 °C stabilised) |
| Corrosion / chemical | none — rusts without protection |
| Relative cost | 1.0× of a standard 52100 bearing |
A rolling mill applies a load that would destroy any other bearing type, and it does it continuously for weeks. Four rows of cylindrical rollers share the load across the roll face; the rings are through-hardened to 60 HRC with a case that resists the shock at the bite. Nothing about that is marginal, which is why the failure modes in a mill are almost always lubrication and sealing rather than fatigue.
| Position | Bearing type | Material / finish | Why it works there |
|---|---|---|---|
| Work roll neck | Cylindrical roller | 52100 four-row, C3/C4, sealed | Very high radial load, shared across four rows. |
| Back-up roll neck | Tapered roller | 52100 four-row, preset | Radial plus axial from the bending forces. |
| Run-out table roller | Self-aligning roller | 52100, 222xx, C3 | Heat, scale and water; the spherical seat takes frame distortion. |
| Mill drive spindle | Cylindrical roller | 52100, NU, C3 | High speed with radial load, floating to allow axial growth. |
| Material | Fit here | Choose it when |
|---|---|---|
| 100Cr6 / 52100 | Best fit | The only economic choice at this load; the design effort goes into seals and lubrication. |
| M50 | Workable alternative | Housings that stay above 200 °C, where the grease has been replaced by oil-air. |
| Bronze | Workable alternative | Slow, high-load auxiliary shafts where a bush is a planned wear part. |
Because the load per unit width of the roll face is enormous and the envelope is fixed by the mill stand. Four rows share it without growing the roll neck.
Water and scale in the lubricant, or a seal failure. Classical fatigue is rare because the bearing is sized for shock, not for rating life.
Yes, and most mills do. The rings are re-ground and re-matched; the economics only work on the large sizes.
Hardness, temperature, corrosion and equivalents for 52100 chrome steel.
Read →Typical duty, recommended types and suffixes for steel mills.
Read →Hot roll necks — hot strip mill and furnace-adjacent positions above 200 °C.
Read →Mill auxiliaries — run-out table bushes, guide rolls and slow auxiliary shafts.
Read →Send the position, bore size, quantity and the medium it sees. We reply with the material certificate, clearance class, lubricant and price within 30 minutes on working days.