Machine structure steel superior in chip disposability and mechanical properties
摘要
A machine structure steel superior in chip disposability and mechanical properties which contains sulfide-type inclusions such that those particles of sulfide-type inclusions with major axes not shorter than 5 mu m have an average aspect ratio not larger than 5.2 and which also contains coarse particles of sulfide-type inclusions such that the following relation is satisfied. <DF>a/b ≤ 0.25 </DF> where, a denotes the number of particles of sulfide-type inclusions with major axes not shorter than 20 mu m, and b denotes the number of particles of sulfide-type inclusions with major axes not shorter than 5 mu m. The machine structure steel exhibits good chip disposability and mechanical properties despite its freedom from lead.
