In production of PM parts, sintering has a crucial impact on the final properties of the components. In this work, investigation of the sintering procedure was done to characterize the physical and chemical processes occurring during this production stage and also to predict the physical and mechanical properties of the sintered products. Different PM steel grades were used in this research. Physical, chemical, mechanical and functional properties were studied, and the formation of sintering necks was characterized by quantitative fractography. The obtained results has been written within 4 sections named as "modules". In the first module, sintering conducted at various temperatures which enable studying the physical and chemical processes. In the second module, the effects of density on formation of sintering necks were investigated. In the third module, the effect of gas-forming additives during sintering was studied. And in the fourth module, research focused on pore closing effects during sintering of high density compacts.