Abstract: In order to simulate 3D microstructures during solidification with porosity,the physical essence and numerical calculation principles of the finite element-cellular automaton (CAFE) method were analyzed.Then,the CAFE method was used to simulate the solidification processes,porosity,and 3D microstructure of 9SMn28 free-cutting steel castings.It is shown that under the condition of air cooling,the solidification of casting surface layers occurs in the process of continuous cooling,but in the casting interiors there exist firstly isothermal solidification and then cooling solidification.The simulation result of porosity is basically identical with experimental castings.The 3D microstructure of 9SMn28 free-cutting steel can be simulated by the CAFE due to its agreement with experimental results.