Determine saturation magnetization from unsaturated permeability

I need to design an electromagnet for a project, and I want it to operate close to magnetic saturation. However, I don’t know the saturation magnetization of the core material. I know only that it is some form of cast iron, and that the unsaturated relative permeability is 980, considering that the B-H curve is approximated to be linear until saturation. I cannot do any additional measurements. Is there a way to approximately model the saturation magnetization from just this information?