MACHINING STEEL SUPERIOR IN MANUFACTURABILITY

1 . Machining steel superior in manufacturability containing, by mass %,

C: 0.005 to 0.2%

Si: 0.001 to 0.5%

Mn: 0.3 to 3.0%

P: 0.001 to 0.2%

S: 0.30 to 0.60%

B: 0.0003 to 0.015%

O: 0.005 to 0.012%

Ca: 0.0001 to 0.0010%, and

Al≦0.01%,

having an N content satisfying

N≧0.0020% and 1.3×B−0.0100≦N≦1.3×B+0.0034, and

having a balance of Fe and unavoidable impurities, wherein

further, regarding the MnO in the steel, in a cross-section of the steel material perpendicular to the rolling direction, the area of MnO of a circle equivalent diameter of 0.5 μm or more being 15% or less of the area of the total Mn-based inclusions.

2 . Machining steel superior in manufacturability as set forth in claim 1 , wherein, regarding the sulfides mainly comprised of MnS, in a cross-section of the steel material perpendicular to the rolling direction, a density of sulfides of a circle equivalent diameter of 0.1 to 0.5 μm is 10000/mm 2 or more.

3 . Machining steel superior in manufacturability as set forth in claim 1 , further containing, by mass %, one or more of

V: 0.05 to 1.0%

Nb: 0.005 to 0.2%

Cr: 0.01 to 2.0%

Mo: 0.05 to 1.0%

W: 0.05 to 1.0%

Ni: 0.05 to 2.0%

Cu: 0.01 to 2.0%

Sn: 0.005 to 2.0%

Zn: 0.0005 to 0.5%

Ti: 0.0005 to 0.1%

Zr: 0.0005 to 0.1%

Mg: 0.0003 to 0.005%

Te: 0.0003 to 0.2%

Bi: 0.005 to 0.5%

Pb: 0.005 to 0.5%.