The main housing materials for the current standard bearing units are gray cast iron FC200 and ductile iron FCD450.
The FC200 material contains black graphite and graphite distributed as shown in photo 1. When heavy shock loads are applied to the housing, cracks spread along the black graphite strands and the housing may fracture.
In FCD450 material, the black graphite and graphite nodules are distributed as shown photo 2. This black graphite distribution can prevent the spreading of cracks. Also the shock resistance at low temperature, of FCD450 is superior to that of FC200.
Comparison of characteristics of ductile cast iron and gray cast iron
Material |
Symbol |
Tensile Strength N/mm2 |
Elongation % |
Hardness HB |
Ductile Cast Iron |
FCD450 |
Minimum 450 |
Minimum 10 |
143~217 |
Gray Cast Iron |
FC200 |
Minimum 200 |
Not Specified |
Maximum 223 |
30 mm not-machined test piece |
