I haven't been able to locate any engines that use steel for the bypass fan. All sources suggest Ti and composites are used for blade construction. Apart from the weight steel could partially make up for it by offering a thinner blade, cost/ease of construction and more resistance to foreign objects.
The reason I ask is that I am trying to design a large ducted fan (800mm) that will be as cheap as possible to manufacture by using a thin sheet of stainless steel for the blade material. The cut to shape sheet will be pressed in a mold to achieve the designed AoA across the blade length and then a 3D printed airfoil will slide over it.