cast iron impact

[WardHollowayPE]

I have noticed that when a bearing housing is cast iron it can handle impact loads better than a steel housing. Cast iron is brittle compared to steel. I was just wondering what the reasons are.
Thanks

Ward Holloway, Jr, PE

 

[TVP]

Are the designs exactly the same? What type of iron is it because there is a huge difference between ductile iron (nodular iron) and grey iron. How is the steel part heat treated?

 

[WardHollowayPE]

The housings are grey cast, I am not sure about the steel housings. I have also seen machine designs where cast is prefered over steel due to vibration. The impact strength of cast may be just rumor. It's not important for any design I was working on. I was just curious.


Ward Holloway, Jr, PE

 

[CoryPad]

Gray iron has higher vibration damping than steel due to the graphite phase.

Gray iron will have much worse impact resistance than steel with constant geometry.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[metengr]

Other reasons for using grey iron castings as bearing housings, in addition to the reason(s) stated above, are that they can be intricate in shape and are relatively easy to produce with minimal machining effort, are lower cost in comparison to fabricated bearing housings and have been used by motor and gear box manufacturers for many years.

 

[arunmrao]

To reiterate what some of the members have already suggested,CI has a better damping capacity,hence any small jerks or jumps can be easily absorbed without causing any distortion or bend to the shaft/gear.

Ease of manufacture into shaped component,along with the lowest cost makes it the chosen one.

Perhaps in the event of catastrophe, the CI bearing block would crack easily and release the stress,thus saving the shaft/bearing from getting damaged.

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