Free-cutting non-quenched and tempered steel for wind power pin shaft and manufacturing method of free-cutting non-quenched and tempered steel

The invention relates to free-cutting non-quenched and tempered steel for a wind power pin shaft and a manufacturing method of the free-cutting non-quenched and tempered steel. The steel comprises the following chemical components in percentage by weight: 0.20 to 0.25 percent of C, 0.35 to 0.50 percent of Si, 1.35 to 1.55 percent of Mn, less than or equal to 0.008 percent of P, 0.020 to 0.035 percent of S, 0.3 to 0.4 percent of Cr, 0.10 to 0.35 percent of Ni, 0.02 to 0.05 percent of Mo, 0.010 to 0.045 percent of Al, 0.08 to 0.15 percent of V, 0.010 to 0.015 percent of N and the balance of Fe and inevitable impurity elements. During rolling, controlled rolling and controlled cooling are carried out, the oxide characteristic value K3 of the steel is smaller than or equal to 10, the steel Rel (yield strength) is larger than or equal to 520 MPa, the Rm (tensile strength) is larger than or equal to 650 MPa, the ductility A5 is larger than or equal to 18%, the V-type impact energy value at the temperature of-30 DEG