The different steels used for bearing materials

SMB Technical Talk: the properties of the various steel materials that are used for bearings, and the differences and advantages of chrome and stainless steel

SMB Technical Talk: the properties of the various steel materials that are used for bearings, and the differences and advantages of chrome and stainless steel.

The choice is not just about corrosion resistance.

Chrome steel (high carbon chromium steel) is the most commonly used steel for bearings.

It is harder than stainless steel so gives longer life ratings.

However it does not perform as well at higher temperatures.

Above 120C it undergoes greater dimensional changes and load capacity reduces.

Intermittent temperatures up to 150C can be tolerated but a constant 150C or higher temperature would reduce bearing life.

Heat treatement will allow the bearing to cope with roughly 170C constant.

The most common grade of stainless steel for bearings is 440.

It is hardenable and tough enough to take heavy loads (about 20% less than chrome steel) but is corrosion resistant and should cope with constant temperatures of up to 250C constant and 300C intermittent.

It is often wrongly assumed that all stainless steel is non magnetic.

440 stainless certainly is magnetic.

It is also not completely corrosion resistant and is affected by salt water and many acids/alkalis.

316 grade is far more corrosion resistant (hence the nickname "marine grade") and non magnetic, but much softer, and can only cope with small loads and speeds.

As it is not hardenable, it cannot easily be ground so 316 bearings are semi precision with a rougher feel.

For further information on bearing materials, see our technical data page on the website.

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