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13. BEARING MATERIALS

The bearing rings and rolling elements of rolling 13.1 Materials for Bearing Rings and Rolling NSK uses highly pure vacuum-degassed bearing 13.2 Cage Materials
bearings are subjected to repetitive high pressure with Elements steel containing a minimum of oxygen, nitrogen, and
a small amount of sliding. The cages are subjected to hydrogen compound impurities. The rolling fatigue life The low carbon steels shown in Table 13.5 are the main
tension and compression and sliding contact with Primarily, high carbon chromium bearing steel of bearings has been remarkably improved using this ones for the pressed cages for bearings. Depending on
the rolling elements and either or both of the bearing (Table 13.1) is used for the bearing rings and rolling material combined with the appropriate heat treatment. the purpose, brass or stainless steel may be used. For
rings. elements. Most NSK bearings are made of SUJ2 For special purpose bearings, high temperature bearing machined cages, high strength brass (Table 13.6) or
Therefore, the materials used for the rings, rolling among the JIS steel types listed in Table 13.1, while steel, which has superior heat resistance, and stainless carbon steel (Table 13.5) is used. Sometimes synthetic
elements, and cages require the following the larger bearings generally use SUJ3. The chemical steel having good corrosion resistance may be used. resin is also used.
characteristics: composition of SUJ2 is approximately the same as The chemical composition of these special materials
AISI 52100 specified in the USA, DIN 100 Cr6 in are given in Tables 13.3 and 13.4.
High rolling contact Germany, and BS 535A99 in England.
Material fatigue strength Characteristics For bearings that are subjected to very severe shock Table 13. 4 Chemical Composition of Stainless Steel for
characteristics required for loads, carburized low-carbon alloy steels such as Rolling Bearing (Major Elements)
required for High hardness cage material chrome steel, chrome molybdenum steel, nickel
bearing rings chrome molybdenum steel, etc. are often used. Such Standard Symbols Chemical Composition (%)
and rolling High wear steels, when they are carburized to the proper depth
elements resistance and have sufficient surface hardness, are more shock JIS G 4303 SUS 440 C C Si Mn P S Cr Mo
resistant than normal, through-hardened bearing steels SAE J 405 51440 C 0.95 to 1.20 16.00 to 18.00
High dimensional because of the softer energy-absorbing core. The 0.95 to 1.20 Less than Less than Less than Less than 16.00 to 18.00 Less than
stability chemical composition of common carburized bearing 1.00 1.00 0.040 0.030 0.75
steels is listed in Table 13.2. Less than Less than
High mechanical 1.00 Less than Less than Less than 0.75
strength 1.00 0.040 0.030

Other necessary characteristics, such as easy Table 13. 5 Chemical Composition of Steel sheet and Carbon Steel
production, shock and heat resistance, and corrosion for Cages (Major Elements)
resistance, are required depending on individual
applications.

Table 13. 1 Chemical Composition of High-Carbon Chromium Bearing Steel (Major Elements) Chemical Composition (%)

Standard Symbols Chemical Composition (%) Classification Standard Symbols C Si Mn P S
JIS G 4805
C Si Mn P S Cr Mo Steel sheet and JIS G 3141 SPCC Less than − Less than Less than Less than
ASTM A 295 0.15 to 0.35 strip for pressed BAS 361 SPB 2 0.12 0.50 0.04 0.045
SUJ 2 0.95 to 1.10 0.40 to 0.70 Less than Less than Less than 1.30 to 1.60 − cages JIS G 3311 S 50 CM 0.13 to 0.20 Less than
0.15 to 0.35 0.50 0.025 0.025 Less than Less than 0.030
0.15 to 0.35 0.90 to 1.15 Less than Less than 0.47 to 0.53 0.30 0.25 to 0.60 0.03 Less than
Less than 0.025 0.025 0.035
SUJ 3 0.95 to 1.10 0.50 Less than Less than 0.90 to 1.20 − Less than
0.025 0.025 0.03
0.15 to 0.35 0.60 to 0.90

SUJ 4 0.95 to 1.10 1.30 to 1.60 0.10 to 0.25 Carbon steel for
machined cages
52100 0.93 to 1.05 0.25 to 0.45 Less than Less than 1.35 to 1.60 Less than JIS G 4051 S 25 C 0.22 to 0.28 0.15 to 0.35 0.30 to 0.60 Less than 0.03 Less than 0.035
0.025 0.015 0.10

Remarks BAS is Japanese Bearing Association Standard.

Table 13. 2 Chemical Composition of Carburizing Bearing Steels (Major Elements)

Standard Symbols Chemical Composition (%) Table 13. 6 Chemical Composition of High Strength Brass for Machined Cages
JIS G 4052
C Si Mn P S Ni Cr Mo Chemical Composition (%)
JIS G 4053
ASTM A 534 SCr 420 H 0.17 to 0.23 0.15 to 0.35 0.55 to 0.95 Less than Less than Less than 0.85 to 1.25 − Standard Symbols Impurities
SCM 420 H 0.17 to 0.23 0.15 to 0.35 0.55 to 0.95 0.030 0.030 0.25
SNCM 220 H 0.17 to 0.23 0.15 to 0.35 0.60 to 0.95 Less than Less than Less than 0.85 to 1.25 0.15 to 0.35 Cu Zn Mn Fe Al Sn Ni Pb S i
SNCM 420 H 0.17 to 0.23 0.15 to 0.35 0.40 to 0.70 0.030 0.030 0.25
SNCM 815 0.12 to 0.18 0.15 to 0.35 0.30 to 0.60 Less than Less than 33.0 to 42.0 0.1 to 1.5 Less than
0.030 0.030 0.35 to 0.75 0.35 to 0.65 0.15 to 0.30 JIS H 5120 CAC301 55.0 to 60.0 Residual 0.5 to 2.5 0.5 to 1.5 0.5 to 1.5 Less than 1.0 Less than Less than
Less than Less than (HBsC 1) 0.1 to 1.0 0.2 to 2.0 1.0 0.4 0.1
0.030 0.030 − Less than
Less than Less than 1.55 to 2.00 0.35 to 0.65 0.15 to 0.30 JIS H 3250 C 6782 56.0 to 60.5 − 0.5 −
0.030 0.030
4.00 to 4.50 0.70 to 1.00 0.15 to 0.30 Remarks Improved HBsC 1 is also used.

8620 H 0.17 to 0.23 0.15 to 0.35 0.60 to 0.95 Less than Less than 0.35 to 0.75 0.35 to 0.65 0.15 to 0.25
4320 H 0.17 to 0.23 0.15 to 0.35 0.40 to 0.70 0.025 0.015 1.55 to 2.00 0.35 to 0.65 0.20 to 0.30
9310 H 0.07 to 0.13 0.15 to 0.35 0.40 to 0.70 Less than Less than 2.95 to 3.55 1.00 to 1.40 0.08 to 0.15
0.025 0.015
Less than Less than
0.025 0.015

Table 13. 3 Chemical Composition of High Speed Steel for Bearings Used at High Temperatures

Standard Symbols C Chemical Composition (%)

Si Mn P S Cr Mo V Ni Cu Co W

AISI M50 0.77 to 0.85 Less than Less than Less than Less than 3.75 to 4.25 4.00 to 4.50 0.90 to 1.10 Less than Less than Less than Less than
0.25 0.35 0.015 0.015 0.10 0.10 0.25 0.25

A 114 A 115