hardness values 1

[Gerry45]

Can anyone advise me on the ideal and expected surface and core hardnesses for bearing quality balls of 64mm diameter made from 100Cr6 and 100CrMn6 ?

Am I right in believing that the 100CrMn6 would give a more uniform hardness and therefore less internal residual stress ?

 

[Carburize]

At mid range of the analysis for these two alloys the ideal diameter is about 85-mm for 100Cr6 and about 230-mm for 100CrMn6 resulting from higher silicon and manganese.
For a 64-mm ball therefore I would expect to see approximately the same hardness profile for both alloys which would be essentially flat at around 62 - 63 Rc.

 

[TVP]

There is some good information on 100Cr6 in the following documents:

http://www.snr-bearings.com/group/f...earingsteelforapplications.pdf?contentID=1163

http://www.struers.com/resources/elements/12/36589/e-Structure 8E.pdf

The microhardness data in the Struers paper converts to ~ 62-63 HRC.

 

[Gerry45]

Thanks both for your good info.

Carburise, what do you mean by 'ideal diameter'. Previously someone said the the maximum thickness for full through-hardening in 100Cr6 was 32mm. This seems along way from the dimensions you give of 85 and 230mm so these things may not be connected. Perhaps you can explain to me a little more please ?

 

[Carburize]

The "ideal diameter" is a term developed by Grossman in the late 30's to describe the hardenability of an alloy and represents the diameter of an infinitely long bar which will quench to 50% martensite in the center.

 

[Gerry45]

So at a diameter of 32mm, you would get perhaps 100% martensite at the core ? So at with 64mm and spherical, we would be closer to 100% than 50% martensite ?

I guess the remaining material is mainly austenite and the difference in structure gives rise to potential residual stresses ?

 

[Carburize]

Correct concerning the sphere.
The non martensitic product will most likely be bainite rather than austenite.