1. Materials of Bearings

The materials of the race and ball of bearing require enough hardness that meet the following qualities:
(1). Large fatigue strength against repeated stress due to fatigue fracture of the race surface which governs the life of the bearings.
(2). High limit of elasticity and high yield strength to prevent deformation when a large load is applied per unit area.
(3). Large abrasion resistance against sliding friction between the retainer and the ball.
(4). High strength against crack due to impact load and failure caused by improper fitting etc.
(5).Small secular change in dimension and shape due to change of structure or internal stress.
GCr15 Steel <JIS G4805>(High carbon chromium bearing steel) satisfies the above comparatively well, and its chemical composition is shown in the following table. 

Chemical composition of high carbon chromium bearing steel 

In order to maitain uniform qualit of materials, FK keeps fully equipped installations and performs strict acceotance tests and inspections based on the strict acceptance standards in addition to JIS-standards. 

Kinds of test done at the FK are mainly chemical analysis, magnetic exploration, ultrasonic exploration, corrosion by strong acid, inspection of structure by naked eyes, inspection of structure by microscope, crusher test and hardness etc.

2. Material of the Cage and the Rivet

 The material of cage is JIS G3141(Cold rolled carbon steel sheet and strip)SPCC, and it is formed by the press. The material of the rivet is JIS G3507 (Low carbon steel wire rods)SWRCH 12A. 

3. Materials of Housings

The material of the housings is FC200 JIS G5501 (Gray iron casting) and the mechanical properties are shown in the following table. 

                                      Mechanical properties of Gray cast iron HT200 

Other Materials of Housings

4.Materials of Other Components