Copper-coated steel wire, stranded wire, insulated electric wire, and cable

A copper-coated steel wire comprising:

• a core wire made of a steel;
• and
• a coating layer made of copper or a copper alloy and covering an outer peripheral surface of the core wire;
• in a cross section perpendicular to a longitudinal direction of the core wire, the core wire including a plurality of oxide regions composed of an iron oxide, the oxide regions including the outer peripheral surface of the core wire and being disposed apart from each other in a circumferential direction of the core wire,
• in the cross section perpendicular to the longitudinal direction of the core wire, a sum of lengths of the plurality of oxide regions in the circumferential direction of the core wire being not less than 20% and not more than 80% of a length of the outer peripheral surface of the core wire,
• in the cross section perpendicular to the longitudinal direction of the core wire, the oxide region having a thickness of not less than 0.02% and not more than 2% of a wire diameter of the copper-coated steel wire,
• in the cross section perpendicular to the longitudinal direction of the core wire, a ratio of a length of the oxide region in the circumferential direction of the core wire to a thickness of the oxide region being not less than 1 and not more than 30,
• the steel constituting the core wire having a pearlite structure,
• the coating layer including an intermediate layer disposed in a region including an interface with the core wire and having a higher zinc concentration than a remaining region of the coating layer, and
• the zinc concentration in the intermediate layer being not less than 45 mass % and not more than 95 mass %.