Steel wire for machine structural parts and method for manufacturing the same

A steel wire suitable for a machine structural part, comprising, in mass percentage:

• Fe;
• C in a range of from 0.05 to 0.60%;
• Si in a range of from 0.005 to 0.50%;
• Mn in a range of from 0.30 to 1.20%;
• P in a range of from more than 0 to 0.050%;
• S in a range of from more than 0 to 0.050%;
• Al in a range of from 0.001 to 0.10%;
• Cr in a range of from more than 0 to 1.5%;
• N in a range of from more than 0 to 0.02%;
• and
• inevitable impurities,
• wherein a proportion of an area of cementite present at ferrite grain boundaries in an area of all cementite of the steel wire is 32% or more, and
• wherein, when a C content, in mass percentage, of a steel of the steel wire is expressed as [C], an average circular-equivalent diameter of all the cementite is in a range of from
• (1.668-2.13 [C]) to (1.863-2.13 [C]) μm.