WIRE ROD FOR MANUFACTURE OF STEEL WIRE FOR PEARLITE STRUCTURE BOLT HAVING TENSILE STRENGTH OF 950-1600 MPa, STEEL WIRE FOR PEARLITE STRUCTURE BOLT HAVING TENSILE STRENGTH OF 950-1600 MPa, PEARLITE STRUCTURE BOLT, AND METHODS FOR MANUFACTURING SAME

摘要

This wire rod for the manufacture of a steel wire for a pearlite structure bolt having a tensile strength of 950-1600 MPa has a predetermined chemical structure and is manufactured by performing an isothermal transformation process directly after hot rolling. If the C content is represented as [C] in unit mass%, then in a region 4.5 mm from the surface of the wire rod, the metal structure has a pearlite structure of 140 × [C] area% or more. In the region 4.5 mm from the surface of the wire rod, the mean block particle size of pearlite blocks as measured in a cross-section of the wire rod is 20 μm or less. In the region 4.5 mm from the surface of the wire rod, the average lamellar spacing of the pearlite structure is more than 120 nm and not more than 200 nm.