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MATERIALS OF BALL BEARING UNITS

1.Materials of Bearings

The materials of the race and ball of bearing require enough hardness and 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 

 

Class

Standard

Symbol

                                                   Chemical Composition (%)

C

Si

Mn

P

S

Cr

1

GB

GCr15

0.98-1.10

0.15-0.35

<0.50

<0.025

<0.025

1.30-1.60

DIN

100Cr6

ASTM

E5200

JIS

SUJ2

2

GB

9Cr18

0.98-1.10

<1.00

<1.00

<0.025

<0.025

16.00-18.00

DIN

X105CrMO17

ASTM

440C

JIS

SUC440C

 

In order to maintain uniform quality of materials, We keeps fully equipped installations and performs strict acceptance tests and inspections based on the strict acceptance standards in addition to JIS-standards. 

Kinds of tests done 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 

symbol

Thickness
(mm)

Dia. Of
testing bar
(mm)

Tension test

Traverse braking
Test

Pressure
Strength

Hardness
Test

Tensile
Strength

Bender
Strength

Deflection

 

Hardness

(kgf/mm2)

(kgf/mm)

(mm)

kgf/mm2

(HB)

HT200
(FC200)

Over 6-8

13

Over 23

53

1.8

75

187-255

Over 8-15

20

Over 22

45

2.5

75

170-241

Over 15-30

30

Over 20

40

2.5

75

170-241

Over 30-50

45

Over 17

34

3.0

75

170-241

Over 50

60

Over 16

31

4.5

75

163-229

 

Other Materials of Housings

Symbol

JIS number

FCD40(QT400)

JIS G5502

SPCC(08)

JIS G3141

SUS304

JIS G4304

 

4.Materials of Other Components

Components

Materials used

JIS symbols

JIS number

Sleeve for adapter

Carbon steel for machine structural use

S25C

JIS G4051

Nut for adapter

Carbon steel for machine structural use

S25C

JIS G4051

Washer for adapter

Cold rolled carbon steel sheet and strip

SPCC

JIS G3141

Oil seal

Synthetic nitrile rubber

-

-

Slinger

Cold rolled carbon steel sheet and strip

SPCC

JIS G3141

Hexagon set screw

Nickel chromium molybdenum steel

SCM 435

JIS G4105

Hexagon wrench key

Nickel chromium molybdenum steel

SNCM630

JIS G4103

Grease nipple

Free cutting brass bar

C3604

JIS H3250

 

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