What is the most recent turbofan engine that used steel for its bypass fan blades?
The tickness of the Fan blade is not only defined by the structural requirement but rather for aerodynamic purpose, thus the geometry of the blade won't change much depending on the material used. Most of the metallic blades in use are hollow.
The price of the blade is quite irrelevent in modern engines. If you can decrease the wheight of the fan by 10% for double the price you'll do it as it will ensure so much fuel saving over the life of the engine. Thus I don't see the advantage of using steel over titanium for a fan blade.
Looking at other comments I understand it is for prototyping and needs to remain cheap. I would then recommend to build the core with 3D printed material which will give you the airfoil shape for aerodynamic and then enclose it with a metal sheets in order to obtain a sandwich like structure. This could greatly increase the stiffness and strength without much added weight.