Steel for Induction Hardening

A steel for induction hardening comprising a chemical composition consisting of, in mass percent:

• C:
• 0.58 to 0.68%;
• Si:
• 0.70 to 1.40%;
• Mn:
• 0.20 to 1.40%;
• P:
• less than 0.020%;
• S:
• less than 0.020%;
• Al:
• 0.005 to 0.060%;
• N:
• 0.0020 to 0.0080%;
• 0:
• 0.0015% or less;
• V:
• 0.01 to 0.25%;
• B:
• 0.0003 to 0.0040%;
• Ti:
• 0.010 to 0.050%;
• Ca:
• 0.0005 to 0.005%;
• Cr:
• 0 to 0.15%;
• Cu:
• 0 to 0.50%;
• Ni:
• 0 to 0.30%;
• Mo:
• 0 to 0.20%;
• and
• Nb:
• 0 to 0.05%,
• with the balance being Fe and impurities, and satisfying Formulae (1) to (3), wherein a steel microstructure is made up of ferrite and pearlite, where an area fraction of the pearlite is 85% or more, and
• in the steel, a ratio of a number of composite inclusions to a total number of Al2O3 inclusions and the composite inclusions is 20% or more, and the composite inclusions contain, in mass percent, 2.0% or more of SiO2 and 2.0% or more of CaO, with the 99% or more of the balance being Al2O3;
• C+Si/7+Mn/5+Cr/9+Mo/2.5≤1.05 (1)
• C+Si/10+Mn/20+Cr/25≥0.70 (2)
• Cr/Si≤0.20 (3)
• where, symbols of elements in Formulae (1) to (3) are to be substituted by contents of corresponding elements (mass percent).