Non-quenched and tempered steel wire rod with improved machinability and impact toughness and method for manufacturing same

A method for manufacturing a non-quenched and tempered steel wire rod with improved machinability and impact toughness, the method comprising:

• reheating a steel piece including, in percent by weight (wt %), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the remainder including Fe and inevitable impurities in a temperature range of 950° C. to 1100° C.;
• finish rolling the reheated steel piece into a steel wire rod at a temperature of 750° C. to 850° C.;
• and
• winding and cooling the steel wire rod,
• wherein the cooling performed after the winding comprises:
• a first cooling process performed at an average cooling rate of 5° C./s to 100° C./s from the finish rolling temperature to a winding temperature;
• a second cooling process performed after the first cooling process at an average cooling rate of 2° C./s to 5° C./s from the winding temperature to 700° C.;
• and
• a third cooling process performed after the second cooling process at an average cooling rate of 0.1° C./s to 2° C./s from 700° C. to 450° C.,
• wherein a microstructure of the steel wire rod comprises ferrite and pearlite, and an average thickness of the pearlite layer in a L cross-section, which is parallel to a rolling direction, is 30 μm or less.