There are essentially two choices for the material used in ball
bearings - chrome steel or stainless steel. Since the material
plays a major part in the performance of a bearing in any given
application, it is very important that the correct material
is used. Note that the specified material applies to the load
bearing components only - the rings and the balls. The retainer
and the shields (if used) are usually made from a different
material and are subject to separate specification
CHROME STEEL (AISI 52100 OR EQUIVALENT)
This is the standard material used for ball bearing applications
where load capacity is the main consideration. The machinability
of this steel is excellent, giving smooth, low noise raceway
finishes, together with superior life. Chrome steel material
is recommended in applications where corrosion is not a factor.
CHEMICAL COMPOSITION (%):
C
CARBON |
Si
SILICON |
Mn
MANGANESE |
P
PHOSPHOROUS |
S
SULPHUR |
Cr
CHROMIUM |
Mo
MOLYBDENUM |
| .95 - 1.1 |
.15 - .35 |
Max .5 |
Max .025 |
Max .025 |
1.3 - 1.6 |
- |
Hardness: 60 - 64 Rockwell 'C'
STAINLESS STEEL
400 series martensitic stainless steel is the standard material
for miniature and instrument ball bearings where corrosion resistance
is more important than load capacity. There are 3 types of 400
series stainless steel used in the bearings described in this
handbook. These materials have evolved in response to different
manufacturing and application needs. It is important to note
that the actual material used is generally determined by the
manufacturer, and cannot be specified by the user. The bearing
part numbering system gives the appropriate codes for each material
type.
DR Stainless steel
This material is used in the manufacture of most corrosion-resistant
bearings. It has been specifically developed to give excellent
lifetime and low noise characteristics, combined with superior
corrosion-resistance.
CHEMICAL COMPOSITION (%):
C
CARBON |
Si
SILICON |
Mn
MANGANESE |
P
PHOSPHOROUS |
S
SULPHUR |
Cr
CHROMIUM |
Mo
MOLYBDENUM |
| .6 - .7 |
Max 1.0 |
Max 1.0 |
Max .03 |
Max .01 |
12 - 13.5 |
Max .25 |
Hardness: 58 - 60 Rockwell 'C'
AISI 440C STAINLESS STEEL
The use of 440C material has declined in favor of other, more
modern stainless steel formulations. However, it is still widely
available and has very high resistance to corrosion.
CHEMICAL COMPOSITION (%):
C
CARBON |
Si
SILICON |
Mn
MANGANESE |
P
PHOSPHOROUS |
S
SULPHUR |
Cr
CHROMIUM |
Mo
MOLYBDENUM |
| .95 - 1.2 |
Max 1.0 |
Max 1.0 |
Max .04 |
Max .03 |
16 - 18 |
Max .75 |
Hardness: 58 - 60 Rockwell 'C'
ES1 STAINLESS STEEL
This is a relatively new stainless steel formulation with excellent
machinability that allows raceway finish characteristics approaching
those of chrome steel, combined with a corrosion-resistance
at least the equal of AISI 440C.
CHEMICAL COMPOSITION (%):
C
CARBON |
Si
SILICON |
Mn
MANGANESE |
P
PHOSPHOROUS |
S
SULPHUR |
Cr
CHROMIUM |
Mo
MOLYBDENUM |
| .44 - 46 |
.2 - .4 |
.2 - .4 |
Max .03 |
Max .01 |
12.8 - 13.2 |
Max .25 |
Hardness: 58 - 60 Rockwell 'C'
ES1 material exposed to hgh humidity
52100 material exposed to high humidity
|
