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Bearing Materials - SHANDONG OBETTER BERAING CO., LTD
6.Dec. 2010 WWW.OBTBEARING.COM
The bearing industry uses different materials for the production of the various bearing components. The materials are processed to achieve desirable properties to maximize bearing performance and life. The materials described here are the most commonly used. Additional information can be found in the Technical Information Sheets for Balls, Closures, and Retainers.
Chrome Steel – SAE 52100
The most common material used to produce the load carrying components in precision ball bearings, roller bearings, and tapered roller bearings is 52100 chrome steel. These components are the inner and outer rings, balls and rollers. The chemical composition of this steel has high carbon and about 1.5% chromium content. Using controlled processing and heat-treating methods the finished bearing components have high strength to resist cracking and a hard surface to resist subsurface rolling contact fatigue. The typical surface hardness for bearing components made from this material ranges from 60-64 on the Rockwell hardness C scale (Rc).
Extra clean 52100 chrome steel
The raw steel used to produce high precision miniature bearings is processed with additional melting steps. The result is a type of steel with very uniform fine grain material structure, the bearing contact surfaces can be super finished very smooth so the bearing is very quiet.
The most common heat treating method for chrome steel is to thru harden the steel in a controlled atmosphere furnace. Bearings manufactured from chrome steel can operate at continuous temperatures up to 120°C.
Where higher temperatures are encountered, it is possible to Heat Stabilize the bearing components. By varying the heat treating process, bearings can be produced so they are capable of operating at temperatures of 220°C, and higher. For these applications, the components must be subjected to a tempering treatment at a higher temperature corresponding to the service temperature. This elevated tempering treatment has a detrimental effect on the hardness of the material and the load carrying capacity of the bearing is reduced.
SAE 52100 is an excellent general purpose bearing steel. Due to its excellent hardness and wear resistance, it exhibits good fatigue life in rolling element bearings. However, the corrosion resistance of chrome steel is poor because of the low chromium content. The surfaces of the bearings must be protected with a coating of rust inhibitor or oil to stop oxidation.
As can be seen in the following table, the standard chemical composition of chromium steel will vary depending on the country where it is produced.
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Designation
Country |
C% Carbon |
Si% Silicon |
Mn% Manganese |
P% Phosphorous |
Cr% Chromium |
Mo% Molybdenum |
Ni% Nickel |
S% Sulfur |
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AISI 52100
USA |
.95-1.1 |
.15-.35 |
.5 max |
.012 max |
1.3-1.6 |
.08 max |
.25 max |
.025 max |
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100CR6
Germany |
.95-1.1 |
.15-.35 |
.25-.45 |
.03 max |
1.35-1.65 |
.1 max |
- |
.02 max |
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SUJ2
Japan |
.95-1.1 |
.15-.35 |
.5 max |
.025 max |
1.3-1.6 |
.08 max |
.25 max |
.025 max |
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GCR15
China |
.95-1.05 |
.15-.35 |
.25-.45 |
.027 max |
1.4-1.65 |
.1 max |
.23 max |
.02 max |
Stainless Steels
Stainless steel materials are used to make bearing components because it is more resistant to surface corrosion due to the higher content of chromium (~18%) with the addition of nickel. The chromium reacts with oxygen to form a layer of chromium oxide on the surface, creating a passive film.
Martensitic Stainless Steel- AISI 440C
The carbon content in 400 series stainless steels is high enough so it can be hardened using standard heat-treating methods up to Rc58. Due to the lower hardness, the load carrying capacity is 20% lower in bearings made from this material, than they are with 52100 chrome steel bearings. The level of carbon content means the components are magnetic. The corrosion resistance is “good”, when 440C material is exposed to fresh water and mild chemicals. This material is primarily used by US bearing manufacturers.
Miniature bearings made from conventional 440C stainless steel will be slightly noisy because the large carbides that normally concentrate at the grain boundaries are exposed in the raceway finishing process. Larger bore bearings are not as affected by this condition. Bearings made from 400 series stainless steel can operate at higher temperatures than chrome steel, up to 250°C continuous. Bearings made from this material are generally more expensive than chrome steel bearings.
Martensitic Stainless Steel – ACD34
Many miniature bearing manufacturers make their rings and balls with a stainless steel material with slightly lower carbon and chromium content than AISI 440C – ACD34. After heat treatment, this material has smaller carbides so the bearing will have superior low noise characteristics while offering the same corrosion resistance as 440C. For bearings produced from this material, some manufacturers will publish the same load ratings as those for chrome steel. This is due to the use of tightly controlled heat treating methods that result in hardness up to Rc 60. Although this is one of the most widely used stainless steels for ball bearings, there is no AISI designation for this material.
Shandong Obetter bearing Company is a leading global supplier in the areas of bearings, mechatronics, services. OBT Group as a high-tech enterprise and professional manufacturer specicalized in ball bearing and roller bearing. we can produce non-standard bearing and machine parts as our customers request. we always follows the principles of "Good Faith, Equality, Cooperation and Win-Win" to cooperate with our customers.
For additional information, please contact:
Company brand: OBT Bearing
Company Name: Shandong Obetter Bearing Co., Ltd
WebSite: www.obtbearing.com
Tel/FAX:86-635-8511972
E-mail: obtbearing@163.com
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