Machine bed material

[Aust12]

Hi all. I finally built the mill. I used 20X75mm plate aluminium for the rail bases. When I added the epoxy the rail bases shifted slightly. It worked out ok it’s accurate to 30 microns or less. I was thinking of doing a redesign to try and improve on the accuracy. I have attached the drawings of what I’m planning. It will be made out of 50mm thick c45 steel the base will measure 500X400mm. There should be a nice but if weight in it.
I know it’s preferable to make machine bases out of cast iron but would C45 hot rolled steel work for this machine. The surfaces for the rails will be ground flat. It will only be cutting brass aluminium and sometimes small bits of steel.