| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a rolled steel material for induction hardening, which is capable of achieving a high strength and a high base-material toughness even without being refined and forms a hardened layer excellent in toughness by induction hardening. <P>SOLUTION: The rolled steel material for induction hardening has chemical components comprising, by mass, 0.38 to 0.55% C, ≤1.0% Si, 0.20 to 2.0% Mn, ≤0.020% P, ≤0.10% S, 0.10 to 2.0% Cr, 0.010 to 0.10% Al, 0.004 to 0.03% N and the balance being Fe with impurities, wherein a value of [C+(1/10)Si+(1/5)Mn+(5/22)Cr+1.65V-(5/7)S] is ≤1.20, and the total content of Si, Mn and Cr satisfies 1.2 to 3.5%. The rolled steel material has a microstructure composed of ferrite, lamellar pearlite and spheroidal cementite, wherein the ferrite has an average crystal grain size of 10 μm or less, the lamellar pearlite accounts for ≤20% (including 0%) of the area of the microstructure, and the number of the spheroidal cementite is 6×10<SP POS="POST">5</SP>pieces/mm<SP POS="POST">2</SP>or more. The rolled steel material may further comprise specific amounts of one or more elements chosen from Cu, Ni, Mo, Ti, Nb and V, respectively. <P>COPYRIGHT: (C)2012,JPO&INPIT |
