Sintered materials have recently become an indispensable part of power and motion transmission systems. Due to relatively low production costs, high material efficiency, reduced noise and vibration, and low environmental impact, sintered materials have a great advantage over classic materials. One of the problems of sintered materials is porosity, due to which there is a microlevel stress concentration which promotes the initiation and propagation of damage in the material. Using the obtained results of metallographic analysis, numerical modeling of the deformation process of the heterogeneous sintered material Astaloy Mo+0.2C at the microstructural level was carried out in this work for constitutive models of damage and elastoplastic behaviour of the material. Three different densities of sintered steels were analysed and separately for each density three different model sizes. Two-dimensional heterogeneous models consist of crystalline grains of ferrite and bainite and pores. The properties of ferrite and bainite were obtained through the instrumented indentation method. Preprocessing, processing and postprocessing was performed in the Abaqus software package, which is based on the finite element method. After the numerical simulation, the influence of different sizes and the influence of different porosity for the elastic and elastoplastic behaviour of the material and for the elastoplastic behaviour of the material with damage is shown. The paper is designed in such a way that a short introduction to powder metallurgy and sintered steels is given. After that, the constitutive models of the behaviour of the materials used in this work are described. The instrumented micro-level indentation method and data reconstruction to obtain the material properties used in this work are briefly described. An insight into the finite element method is given and the formulation of two-dimensional elements used for numerical simulation is presented. At the end, the model preprocessing procedure is described, and the results are analysed. The results of the numerical analyses were compared with the experimental results at the macro level obtained through uniaxial tests. Finally, according to the results, a conclusion is given.