What could be the reason for using

[N K Acharya]

What could be the reason for using SAE 1141 grade steel in Railway engines - parts such as rocker arm and valve bridge? since it has an ideal diameter around 2 inches, is it possible to get martensitic structure at the core in a section 1 1/2 inch diameter and height 2 inches?

 

[metengr]

Machineability and heat treatment response because of manganese. You need to look up the hardenability curve for this material.

 

[mrfailure]

You may not want to get a through-hardened structure though, as the residual stress associated with the phase change to martensite could result in a longitudinal zipper crack running from sulfide to sulfide to relieve the stress. I do not recommend this and would suggest, if possible, using a medium or low-alloy nonresulfurized steel instead.