I have serious doubts that case-hardening gives much of a spring effec to a piece of steel. After the case-hardening process if there was warpage etc, these gns were "HardFit". This meant they were bent back into shape. I do not believe that in this hard fitting they were moved enough they would not have gone back had they had a spring temper, but they stayed bent, indicating they were not of the nature of a spring.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra