SKF - Rolling Bearings

Materials for rolling bearings
Machined metal cages
Machined steel cages
Machined steel cages are normally made of
non-alloyed structural S355GT (St 52) type
steel in accordance with EN 10 025:1990 +
A:1993. To improve sliding and wear-resistance
properties, some machined steel cages
are surface treated.
Machined steel cages are used for large
bearings or in applications where there is a
danger that season cracking, caused by a
chemical reaction, may occur if a brass cage is
used. Steel cages can be used at operating
temperatures up to 300 °C (570 °F). They are
not affected by the mineral or synthetic oilbased
lubricants normally used for rolling
bearings, or by the organic solvents used to
clean bearings.
Polymer cages
Polyamide 66
For the majority of injection moulded cages,
polyamide 66 (PA66) is used. This material,
with or without glass fibres, is characterized
by a favourable combination of strength and
elasticity. The mechanical properties like
strength and elasticity of polymer materials
are temperature dependent and subject to
ageing. The most important factors that play a
role in the ageing process are temperature,
time and the medium (lubricant) to which the
polymer is exposed. Diagram 1 shows the
relationship between these factors for glass
fibre reinforced PA66. It shows that cage life
decreases with increasing temperature and
the aggressiveness of the lubricant.
Machined brass cages
Most brass cages are machined from a
CW612N cast or wrought brass in accordance
with EN 1652. They are unaffected by most
common bearing lubricants, including synthetic
oils and greases, and can be cleaned
using normal organic solvents. Brass cages
should not be used at temperatures above
250 °C (480 °F).
E
Diagram 1
Cage ageing life for glass fibre reinforced polyamide 66
Cage ageing life [h]
100 000
Mild lubricants
Aggressive lubricants
10 000
1 000
100
50 100 150 200
(120) (210) (300) (390)
Bearing temperature [°C (°F)]
153