Patent ID: 8585835
Filing Date: 2013-11-19
Classification: C21D,C22C,F02M

Abstract:
1. A high-strength steel machined product having excellent hardenability, comprising: about 0.42 to 0.7% of C; 2.5% or less (excluding 0%) of Si; 0.5 to 3% of Mn; 1.5% or less of Al; 0.01 to 0.3% as the sum of one or more of Nb, Ti, and V; 2.0% or less (excluding 0%) of Cr; 0.5% or less (excluding 0%) of Mo; 2.0% or less of Ni; 0.7 to 3.0% as the sum of two or more of Cr, Mo, and Ni; 0.75 to 0.90% of carbon equivalent (Ceq) defined by the following formula and the balance of Fe and inevitable impurities, wherein the metal structure is composed of a mother-phase structure containing 50% or more (volume percentage to the entire structure) of lathy bainitic ferrite and 20% or less (volume percentage to the entire structure) as the sum of polygonal ferrite and granular bainitic ferrite, and a secondary-phase structure has 5 to 30% (volume percentage to the entire structure) of retained austenite and 5% or less (volume percentage to the entire structure) of martensite.