4130 Endurance Limit

[rhpe]

I am designing an axle shaft and have specified HT to be Rkw C 34-38 quench and tempered. Does anyone have a feel for what the endurance limit modifier should be as a funciton of the ultimate tensile strenght? I know that for most purposes I would start with half of the tensile strength and then use the appropriate deraters.

Thanks for your input.

 

[metengr]

You might want to start here for some help

http://www.fatiguecalculator.com/

 

[Fabrico]

Why not do what others do? Up the endurance limit by going to 4340.

 

[NickE]

Is there really a significant difference btw teh endurance limit of 4130 adn 4340 at the same strength?

 

[metengr]

If both steels (4340 ans 4140) are heat treated to the same ultimate tensile strength level, the endurance limits are very close.

 

[Fabrico]

There are factors beyond what some formulas may tell you.
The question was based on what truck axle manufacturers and race axle companies use; 4340 (which includes 300m), 1550 and "Hy-Tuf". Although 4130 is good for many things and highly weldable, it is not particularly inexpensive, much easier to work with than other alloys, or very popular for axles.