Need help with RAR abbreviation

[CoryPad]

I have a part that is carburized SCM420H (similar to SAE 4120). I have a report that states the case microstructure is "Tempered martensite RAR 1-2". I need to know what RAR means. I assume it is a retained austenite rating. Any details about this would be appreciated. Thank you for your help.

Regards,

Cory

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[Carburize]

I am not familiar with the term - it does not appear in either of the two main gear metallurgy specifications AGMA 923 or ISO 6336-5.
What is the part?

 

[CoryPad]

It is a tripod housing for a vehicle halfshaft. I have "borrowed" an Internet image of a similar part, although the area of interest has been truncated (to the right) in this image:

Regards,

Cory

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[Carburize]

It sounds like the RAR 1-2 refers to some internal company document from the OEM.

 

[metengr]

CoryPad;
Perhaps some helpful information;

http://www.atrona.com/_home/content.cfm?content=t_template&exp=1&artTypeID=213&packet=213

 

[metman]

Cory:

metengr's link shows that lab uses RAR = to your guess. Could it be a typo and should read RAR 1-2% instead of inches?

 

[Carburize]

No - 1-2% is way too low a number for anybody to quote and it be meaningful even using X-ray diffraction.

 

[CoryPad]

It was not 1-2 inches - I used the quotation marks to show an exact exerpt from the report. Yet another reason to never use the inch-pound unit system. Blech....

I think Carburize is correct - this is a rating according to an internal company specification. By the way, it can't be the OEM - that's ME! Now to comment to my supplier how much I think of their report that uses unexplained abbreviations, misspelled my company's name, etc.

Regards,

Cory

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[Carburize]

Cory - let us know what it means when you find out!

 

[Carburize]

A major thread drift but... is there any connection between cory and tvp?

 

[CoryPad]

Yes. How did you determine this? Small world, isn't it?

Regards,

Cory

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[Carburize]

cory - I frequent the ASM board as well - OK so what is the connection?

 

[CoryPad]

I just visited our supplier. RAR is an abbreviation for Retained Austenite Rating. This rating is a visual comparison to images of microstructures with known retained austenite levels. There are 7 levels, with 1 being low retained austenite (say < 10%), and 7 being high. The information was attributed to "Chevrolet Laboratories, Detroit, Mich.". There hasn't been a Chevrolet Laboratories in Detroit, Michigan for quite some time, so this is a legacy document that is not widespread in global industry.

Carburize - I prefer to limit public disclosure. If you are an ASM member, you can access the ASM member database and contact me directly.

Regards,

Cory

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

 

[Carburize]

cory - no problem I fully understand -
Thanks for the information on the RAR - if only the lab had just put 10 - 15% on the report!