Material specification page for ucfl200 series two-bolt flange units in Martensitic Stainless 440C. Covers the grade designation (AISI 440C = X105CrMo17 (1.4125), hardened and tempered — the only common stainless hard enough to form a rolling raceway), what the material does inside the bearing, its temperature and environmental limits, the alternatives worth considering, and the sizes available to ISO 3228 / JIS B 1559.
Why Martensitic Stainless 440C for UCFL200 Series Two-Bolt Flange Units
The standard corrosion-resistant bearing steel; a stainless bearing is rated below the same envelope in GCr15, so take its load ratings from the stainless table and never from the chrome steel one. In a ucfl200 series two-bolt flange units it is the ring and rolling element steel of the corrosion-resistant version.
It is the compromise that makes a corrosion-resistant rolling bearing possible: enough carbon to be hardened to a raceway hardness, enough chromium to resist water and mild chemicals. Everything else about the bearing — the envelope, the tolerance class, the clearance group — is unchanged.
Material Properties
| Grade designation | AISI 440C = X105CrMo17 (1.4125), hardened and tempered — the only common stainless hard enough to form a rolling raceway |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | About -30 °C to +180 °C in ordinary bearing service, the lubricant usually deciding before the steel does |
| Corrosion characteristic | Good in water, steam, mild chemicals and food service; it is a hardenable stainless, so it holds less chromium in solution than 304 and will stain in standing chlorides |
Service Limits
A martensitic stainless bearing is rated below the same envelope in chrome steel and it is not stainless in the way 316 is: it is corrosion RESISTANT, and standing salt water, chlorides or long wet periods will still pit it. It is also softer at temperature than GCr15. Take the ratings from the stainless table, and where the environment is genuinely aggressive, consider a full ceramic bearing or a polymer housed unit instead.
Alternatives and When to Switch
If the load matters more than the corrosion, go back to GCr15 with the right seals and a corrosion-inhibiting grease — a sealed chrome steel bearing outlasts a stainless one in many "wet" applications that are only occasionally wet. If the corrosion matters more than the load, go past stainless: a full ceramic or a polymer-housed bearing does not corrode at all.
Sizes of UCFL200 Series Two-Bolt Flange Units Available in Martensitic Stainless 440C
| Designation | Shaft bore d (mm) | Insert bearing | Housing material |
|---|---|---|---|
| UCFL201 | 12 | UC201 | Grey cast iron |
| UCFL202 | 15 | UC202 | Grey cast iron |
| UCFL203 | 17 | UC203 | Grey cast iron |
| UCFL204 | 20 | UC204 | Grey cast iron |
| UCFL205 | 25 | UC205 | Grey cast iron |
| UCFL206 | 30 | UC206 | Grey cast iron |
| UCFL207 | 35 | UC207 | Grey cast iron |
| UCFL208 | 40 | UC208 | Grey cast iron |
| UCFL209 | 45 | UC209 | Grey cast iron |
| UCFL210 | 50 | UC210 | Grey cast iron |
| UCFL211 | 55 | UC211 | Grey cast iron |
| UCFL212 | 60 | UC212 | Grey cast iron |
| UCFL213 | 65 | UC213 | Grey cast iron |
| UCFL214 | 70 | UC214 | Grey cast iron |
| UCFL215 | 75 | UC215 | Grey cast iron |
| UCFL216 | 80 | UC216 | Grey cast iron |
| UCFL217 | 85 | UC217 | Grey cast iron |
| UCFL218 | 90 | UC218 | Grey cast iron |
