In base material, the fatigue strength increases with increasing static strength. In weld joints the base material strength has in most cases no influence.
The material factor (steel strength enhancement factor) is based on experience and test results. FATcomp indetifies the relevant curve depending on the joint you choose.
Improvement methods can increase the fatigue strength in some cases, this is not taken to account in the curves below, picture 1.
Picture 1: Steel strength enhancement factor vs yield strength.