Process for manufacturing a steel machine blank, at least one of which is surface hardened by induction and obtained blank

摘要

A mechanical component is produced by heat treating a low alloy steel, before surface induction hardening, to form a structure of ferrite and 80% lamellar pearlite at least in the region to be surface hardened, the heat treatment being carried out before, during or after operations of shaping an ingot of the steel to a rough product. A process for producing a mechanical component, which is surface induction hardened by two austenitizing operations followed by quenching to obtain a ferrite- and undissolved carbide-free martensitic structure of hardness greater than 800 HV and of ASTM grain size index 7, involves (a) producing an ingot of steel of composition (by wt.) 0.43-0.62% C, 0.5-1.6% Mn, 0-0.8% Si, 0-0.5% Ni, 0-1.5% Cr, 0-0.35% Mo, 0-0.15% V, 0.005-0.05% Al, 0.004-0.022% N, up to 0.1% S, up to 0.1% Pb, up to 0.012% Te, up to 0.04% Se, up to 0.13% Bi, up to 0.005% Ca, balance Fe and impurities, the sum of Mn, Ni, Cr, Mo, V and Si being 0.95-3%; and (b) heat treating as described above. An Independent claim is also included for a mechanical component which consists of the above steel and which has an induction quench hardened portion with the martensitic structure described above, the rest of the component having a structure of ferrite and 80% lamellar pearlite.