A steel pipe for line pipe has a composition of, in mass %: C: 0.02 to 0.11%; Si: 0.05 to 1.0%; Mn: 0.30 to 2.5%; P: up to 0.030%; S: up to 0.006%; Cr: 0.05 to 0.36%; Mo: 0.02 to 0.33%; V: 0.02 to 0.20%; Ti: 0.001 to 0.010%; Al: 0.001 to 0.100%; N: up to 0.008%; Ca: 0.0005 to 0.0040%; and other elements and satisfies Cr+Mo+V0.40, the chemical symbols in the equation substituted by the content of the corresponding element in mass %. The pipe contains tempered martensite and/or tempered bainite and further contains ferrite in at least one of a portion between a steel pipe outer surface and a depth of 1 mm from the outer surface, and a portion between a steel pipe inner surface and a depth of 1 mm from the inner surface.

Free-cutting steel includes a specific composition, with an A value defined by a following formula (1) satisfying 4.0 or more and 20.0 or less, and remainder having Fe and an unavoidable impurity; and texture with 1000 or more sulfide particles with an equivalent circle diameter of less than 1 m per mm.sup.2, 500 or more sulfide particles with an equivalent circle diameter of 1 m or more and 5 m or less per mm.sup.2, and 1000 or more Pb particles with an equivalent circle diameter of 1 m or less per mm.sup.2, wherein
A value=(Mn+5Cr)/S(1) here, symbols of elements in the formula indicate contents (% by mass) of the elements.

The billet rolling mill comprises two rolls for shaping a blank, each shaping roll being provided with at least one rolling tool and being rotated about an axis of rotation by a drive motor, and a manipulator subassembly for moving the blank with respect to the shaping rolls. The manipulator subassembly comprises a clamp gripping the blank and a carriage moving the clamp at least along a direction of rolling of the blank. The manipulator subassembly comprises a linear motor moving the carriage along the direction of rolling. The direction of rolling is perpendicular to the axis of rotation of the rolling tool. The linear motor is configured for accelerating the blank and selectively exerting on the blank, either a tensile force, to extract the blank from a gap defined between the rolling tools, or a braking force, to limit a speed of ejection of the blank.

A high carbon steel wire coil and a production method includes: smelting to obtain molten steel; continuously casting the molten steel to obtain a continuous casting bloom, and performing a reduction with reduction rate that is first high, then low, and then high applied to the continuous casting bloom during continuous casting; heating the continuous casting bloom and then performing blooming to obtain a billet; heating the billet and then performing rolling and air cooling to obtain the wire coil. By finely controlling the dynamic soft reduction parameters during continuous casting, and a reduction with reduction rate that is first high, then low, and then high applied to the continuous casting bloom, the present invention significantly improves the segregation and porosity issues in the central region of the bloom from the source.