CARBON STEEL WIRE WITH HIGH STRENGTH AND EXCELLENT DUCTILITY AND FATIGUE RESISTANCE, PROCESS FOR PRODUCING SAME, AND METHOD OF EVALUATION

WIPO Patent Application WO/2010/050596

A1

Provided are a carbon steel wire which has a high strength that has not been attained so far and which has excellent ductility and fatigue resistance, a process for producing the wire, and a method of evaluating the wire. The carbon steel wire (1) has a carbon content of 0.50-1.10 mass%.  In the wire, the ratio of the hardness of a surface layer part (13) in a cross section (12) to the hardness of a surface layer part (3) in a longitudinal section (2), i.e., coefficient X (cross-section hardness/longitudinal-section hardness), and the ratio of the hardness of the center (14) in the cross section (12) to the hardness of a central part (4) in the longitudinal section (2), i.e., coefficient X (cross-section hardness/longitudinal-section hardness), each satisfies the relationship 0.9