Characteristics and principles of silicon effect on the properties of steel

The physical nature of the influence of silicon dopants on the properties of pipe steels is analyzed. The impact strength at a temperature of -40 С of samples of 10 steels produced by ChTPZ, differing in the content of silicon, carbon, sulfur and nitrogen was studied experimentally. It is shown that with a silicon content of 0.02 wt. % the impact strength is very high (223 J/cm2). Higher silicon additions have a reinforcing effect on steel, but lower the toughness. To distinguish the action of silicon with respect to other alloying elements, literature data on the effect of a large group of alloying elements on the brittle transition temperature and the yield strength of steels are considered. A generalization of the literature data made it possible to propose an empirical equation relating the brittle transition temperature and the yield strength to the composition of the steel. On this basis, it was possible to show that silicon is indeed an element that increases the yield point to the greatest extent and simultaneously enhances the cold-brittleness of iron. The reasons for this phenomenon are discussed, and a hypothesis is put forward that the reason for the sharp increase in the yield strength when silicon is added is due to strong repulsion of silicon and carbon atoms in the neighborhood.