Microstructure and Cutting Performance of New Free-Cutting Stainless Steels Used for Ball Point Pen

A new type S-Pb ferritic free-cutting stainless steel was manufactured by intermediate frequency furnace and electroslag remelting.The chemical composition,microstructure,inclusion and cutting performance were analyzed by optical microscopy,SEM,EDS and ultra-precision CNC lathe.The results show that the free-cutting phases of the tested steel bar,product wire and imported SF20T product wire contained MnS,Pb and the composite inclusion consisted of MnS,Pb and Te.MnS in the steel bar was spindle.MnS in the cold-drawn product wire was fine and elliptical in transverse direction,and distributed along the drawing direction in forms of chain and intermittence,with the size smaller than the transverse and lognitudinal size in SF20T product wire.The matrix microstructure of the tested steel product wire was ferrite with the grain size scale of 10.The cutting performance of the steels was good at high-speed and medium feeding rate,this could meet the requirements to the chip morphology and surface roughness.