GRAPHITE FREE-CUTTING STEEL EXCELLENT IN TOOL SERVICE LIFE AND FINISHED SURFACE ROUGHNESS

摘要

PURPOSE: To graphitize C in steel and to develop graphite free-cutting steel excellent in a tool service life and finished surface roughness by adding steel with a specified trace amt. of B or Pb, Bi, Te, Se or the like as well. ;CONSTITUTION: This steel has a compsn. contg., by weight, 0.02 to 1.0% C, 0.1 to 0.5% Si, 0.3 to 1.5% Mn, 0.02% P, 0.001 to 0.004% B, 0.04 to 0.35% S and 0.002 to 0.01% N or furthermore contg. total 0.05 to 0.35% of one or two kinds of Pb and Bi or total 0.002 to 0.02% of one or two kinds of Te and Se. This steel is subjected to graphitizing treatment, is thereafter rapidly cooled and is annealed to form its structure into a one in which ferrite as the matrix is dispersedly incorporated with graphite fine grains having 5 to 30μm² average cross sectional area in the ratio of 0.20 to 1.0%. Since it contains elements suppressing coagulation on the boundaries between a tool of Pb, Bi, Te, Se or the like and the material to be subjected to machining, the using service life of tool steel for machining is remarkably improved, and the machining finished surface roughness is remarkably improved as well.;COPYRIGHT: (C)1994,JPO&Japio