Steel wire rod and manufacturing method of steel wire rod

A manufacturing method of a steel wire rod, comprising:

• casting a bloom including, as a chemical composition, by unit mass %,
• C:
• 0.60% to 1.10%,
• Si:
• 0.005% to 0.350%,
• Mn:
• 0.10% to 0.90%,
• Cr:
• 0.010% to 0.300%,
• N:
• 0.0100% or less,
• P:
• 0.030% or less,
• S:
• 0.030% or less,
• Al:
• 0% to 0.070%,
• Ti:
• 0% to 0.030%,
• V:
• 0% to 0.100%,
• Nb:
• 0% to 0.050%,
• Mo:
• 0% to 0.20%,
• B:
• 0% to 0.0030%, and
• a remainder including Fe and impurities;
• heating the bloom to a heating temperature in a temperature range of 1150° C. or higher and 1250° C. or lower;
• retaining a temperature of the bloom at the heating temperature for 600 seconds to 7200 seconds;
• hot rolling the bloom after the retaining so that a finishing temperature is 950° C. or higher and 1050° C. or lower to obtain a hot rolled steel;
• water cooling the hot rolled steel to a temperature range of 780° C. or higher and 840° C. or lower;
• winding the hot rolled steel after the water cooling in the temperature range of 780° C. or higher and 840° C. or lower;
• patenting the hot rolled steel after the winding by immersing the hot rolled steel in a molten salt at a temperature of 450° C. or higher and T1° C. or lower defined by Formula (3) for 20 seconds to 200 seconds, within 9 seconds to 25 seconds after the winding;
• and
• tempering the hot rolled steel after the patenting to obtain the steel wire rod by heating the hot rolled steel to a tempering temperature in a temperature range of 540° C. to 600° C., retaining the hot rolled steel at the tempering temperature for 30 seconds to 600 seconds, and cooling the hot rolled steel to room temperature,
• T1[° C.]=−r′ [mm]×16+580 Formula (3)
• where r′ is a distance from a circumferential surface to a central axis of the hot rolled steel in units of mm.