SULFUR AND SULFUR COMPOSITE FREE CUTTING STEEL CONTAINING ZR

摘要

PURPOSE:To provide the titled free cutting steel consisting of prescribed percentages of C, Mn, S, Zr and O and the balance Fe with inevitable impurities and showing satisfactory machinability even when any of carbide and high-speed steel tools is used. CONSTITUTION:A sulfur or sulfur composite free cutting steel contg. Zr is composed of, by weight, =0.80% C, 0.3-2.0% Mn, 0.12-0.40% S, 0.03-0.60% Zr, 0.0005-0.02% O and the balance Fe with inevitable impurities. The machinability of the free cutting steel can be further improved by adding =0.35% Pb. When a conventional steel B2 is machined with a high-speed steel tool, the service life of the tool is as short as about 25min. Free cutting steels Z1-Z4 of this invention ensure =about 150min service life and especially Z4 ensures about 370min service life.