Free-cutting steel and method for manufacturing same

Free-cutting steel comprising:

• a chemical composition containing, in mass %,
• C:
• 0.08% or less,
• Mn:
• 0.50 to 1.50%,
• P:
• 0.100% or less,
• S:
• 0.250 to 0.500%,
• N:
• 0.0050 to 0.0150%,
• O:
• more than 0.0100% and 0.0500% or less,
• Cr:
• 0.70 to 1.50%, and
• a total amount of at least one element selected from a group consisting of Si, Al, and Ti of 0.050 to 0.500%, wherein a content of Ti is 0.010% or less, with the balance being Fe and inevitable impurities,
• with an A value defined by a following formula (1) satisfying 0.40 to 2.00, and
• with a B value defined by a following formula (2) satisfying 1.10×10−3 to 1.50×10−2;
• and
• a steel microstructure with distributed 3000 or more sulfide particles with an equivalent circular diameter of 5 μm or less per mm2,
• wherein
• A value=[Mn]/[Cr] (1)
• B value=(2[Si]+2+[Ti])×[O] (2)
• where [M] indicates a content in mass % of an element M described in [ ].