부산대학교 도서관

A study was made on the effects of alloying elements such as Si, Mn, Cr, Ni and Mo on the rotating bending fatigue properties of carburized steels.At first, the effect of Si was studied using commonly used grades, SCM 420 and SNCM 420. It was shown that decreasing the Si content remarkably reduced internal oxidation and resulted in higher fatigue limit. Next, in order to clarify the effects of other alloying elements fatigue testings were carried out on low Si steels, where the Si content was less than 0.15%. Internal oxdation was reduced and fatigue strength rose with increasing of Ni, Mo contents and with decreasing of Cr, Mn contents, when maintaining the constant core hardness. 0.2% C-3% Ni-0.45% Mo steel, for example, showed the highest fatigue limit of 100kgf/mm2. High Ni-high Mo-low Mn-low Cr steels are considered to exhibit superior fatigue resistance by suppressing the internal oxidation and by the greater fracture toughness of carburized case.