Are there additional downloads for other steels that aren't in the existing library? Is there any way to model case hardened materials or materials that have different hardnesses at different depths in the material?
You could use the composites or shell functionality to assign different layers a different value of stiffness. The material properties interface does not have a direct input for hardness values (using traditional units), but you could translate that to stiffness (EX) for a representative layer. I believe you'd need to use the product known as "SolidWorks Premium", to access the product known as "Simulation" (not SimulationXpress) to do that, however.