Relationship Among Mechanical Properties.

No.

You could look it all up in a good steels data book for yourself and work one out on your own, Mildred. I'm not going to do that for you.

Well to my understanding low alloy steels are designed chemically to meet hardness and toughness goals...by altering the chemical composition certain properties are instilled in the alloy....low carbon and medium carbon steels are not used in the tempering process, only high carbon steel(over 1.2%)....

http://www.technologystudent.com/equip1/heat1.htm

https://en.wikipedia.org/wiki/High-strength_low-alloy_steel

If emperical it would be in tables and it actually is!

No. Use the tables.

The tables came about (at least the NASA versions) because of the gazillion pull test samples I had to make as an apprentice machinist.

Hooker

Thank you one and all for the time.

Low carbon steels don't harden on their own during heat treating. There is a hardening process call carburizing that adds carbon to the surface of the steel and penetrates slightly below the surface:

https://en.wikipedia.org/wiki/Carburizing

This would allow for a surface hardening or 'case hardening' that provides a hardness typically about .06-.09" deep while leaving the remaining inner core of steel ductile and its hardness not affected.

I think most heat treaters would recommend Rc around the mid 40s for maximum toughness.

When I need a tough shaft that is going to see a lot of torque and abuse I would use 4340 hardened to 45-48 Rc.

Track Rollers and Cam Followers are usually case hardened steel, if they were a through hardened alloy steel they may crack due to brittleness but by case hardening they get a hard wear surface with a flexible or ductile inner core not prone to cracking and breaking due to through hardening.

Thank you for the valuable information.