PURPOSE: To produce a low carbon sulfur-based free cutting steel excellent in machinability and the homogeneity of the material.
CONSTITUTION: This low carbon sulfur-based free cutting steel is a one having a compsn. contg., as fundamental conpopnents, by mass, 0.05 to O.15% C, 0.5 to 2.0% Mn, 0.1 to 0.4% S, 0.05 to 0.10% P and 0.005 to 0.040% O, in which the content of Si is limited to ≤0.1% and Al to ≤0.009%, contg. N in the range of 20 to l50ppm, and the balance substantial Fe, and in which, among inclusions of one or more kinds among Al2O3, SiOz2and MnO and/or inclusions in which ≥ two kinds among Al2O3, SiO2 and Mn0 are bonded, the diameter of the inclusions including one or more kinds of oxides by ≥ 50% in total by mass is all regulated to <53μm, or among the inclusions, the number of the ones having ≥53μm diameter is regulated to ≤100 pieces per kg steel. Moreover, Pb, Bi and Te are incorporated therein by 0.01 to 0.40wt.% in total.
KUSANO YOSHIAKI
HAYASHI HIROAKI
OGAWA TOSHIFUMI
