Deep Analysis of Free-cutting Phase and Its Distribution in Japanese SF20T Pen Tip Steel

Abstract

This paper aims at investigating the existence state of free-cutting phase in Japan SF20T free-cutting stainless steel (one of the most widely used pen tip steel). By using the devices of an optical microscope (OM), a scanning electron microscope (SEM), electrolytic etching, and Vickers hardness meter, the quantity, composition, shape, size, distribution of the free-cutting phase in the steel and the change of hardness of steel were analysed and characterized, strive to find out the reason of the performance of SF20T steel is far superior to that of other countries'pen tip steel. The results show that the morphologies of inclusions in the steel were mostly in spindle shape, and their distributions were dispersed and quite uniform. The free-cutting phases, MnS in spindle, Pb, and MnTe, were beneficial to enhancing the cutting performance of the steel. In contrast to domestic materials, the distribution of inclusions in the Japanese steel was more uniform, thereby providing key significance for production of pen-making and steelmaking in domestic plants.