M50 tool steel 2

[mfgenggear]

I have a customer who is considering

AMS6490 or AMS6491 for bearing races

I was told that the AMS6491 is more refined than the AMS6490
Consumable vs Double Vacuum melted.
what would the basis be to use one or the other.
& How would one justify it.

Thanks

 

[kclim]

The VIMVAR process for 6491 would result in a higher purity and more uniform product, which in turn leads to better properties (fatigue resistance, wear).

To determine if either was adequate for the job, you should look at SAE AMS standard and see if the minimum properties match what you have in mind.

I imagine if the application is critical (e.g. safety, people's lives are at risk in case of failure), you could justify 6491 over 6490.

 

[TVP]

kclim outlined the essentials. Here are some excellent resources for more information on the various melting processes, including why they are important for bearing products:

"An Introduction to Premium Melting"

http://www.cartech.com/about.aspx?id=3404

Latrobe Steel melting options

http://www.latrobesteel.com/assets/documents/datasheets/Melt_Flow_Chart.pdf

"Ovako Steel Cleanliness Specifications"

http://www.ovako.com/index.asp?r=1136

"Development of clean steel - advantages in ladle metallurgy and testing technology"

http://www.ovako.com/index.asp?r=1138

NASA tech paper with a table showing difference in performance between CEVM and VIM-VAR (double vacuum process) for gear surface fatigue (relevant to bearings as well)

http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212463.pdf