Steel Cord and Single Steel Wire Having Excellent Straightness Quality for Reinforcing Tire and Manufacturing Method Thereof

Abstract

Provided are a steel cord and a single steel wire having excellent straightness quality for reinforcing tire and a method of manufacturing the steel cord and single steel wire. The steel cord and the single steel wire include a wire undergoing through a drawing process, a heating process performed in a state in which tension is applied to the wire, and a cooling process; and a winding portion on which the wire is wound, the winding portion having a diameter greater than a diameter of the wire, wherein, when an end of the wire that has been wound on the winding portion for six months to one year is fixed on a point and the wire is pulled down vertically to 400 mm, a distance between a first axis that is perpendicular to the point and an opposite end of the wire is 30 mm or less. The method of manufacturing the steel cord and single steel wire having excellent straightness quality for reinforcing tire includes: a wire preparing process, a heating process, a cooling process, and a winding process.

1 . A steel cord and a single steel wire having excellent straightness quality for reinforcing tire, the steel cord and the single steel wire comprising:
 a wire undergoing through a drawing process, a heating process performed in a state in which tension is applied to the wire, and a cooling process; and   a winding portion on which the wire is wound, the winding portion having a diameter greater than a diameter of the wire,   wherein, when an end of the wire that has been wound on the winding portion for six months to one year is fixed on a point and the wire is pulled down vertically to 400 mm,   a distance between a first axis that is perpendicular to the point and an opposite end of the wire is 30 mm or less.   
     
     
         2 . The steel cord and the single steel wire of  claim 1 , wherein
 a heating temperature in the heating process is 200° C. or less, and a cooling temperature in the cooling process is 40° C. or less.   
     
     
         3 . The steel cord and the single steel wire of  claim 2 , wherein
 the heating temperature, a heating time, and the tension applied to the wire during the heating process satisfy condition A below,   
       condition (A): T+13.67 In(t)+2.7 τ≥425 (In condition (A), T is an absolute temperature K of the heating temperature, t denotes the heating time s, and τ is the tension (kgf) applied to the wire). 
     
     
         4 . A method of manufacturing a steel cord and a single steel wire having excellent straightness quality for reinforcing tire,
 the method comprising:   preparing a wire that has been drawn;   heating the wire in a state in which tension is applied to the wire;   cooling down the wire; and   winding the wire on a winding portion having a diameter that is greater than a diameter of the wire.   
     
     
         5 . The method of  claim 4 , further comprising
 measuring straightness by fixing an end of the wire that has been wound on the winding portion for six months to one year at a point and pulling down the wire vertically to 400 mm,   wherein, in the measuring of the straightness, a distance between a first axis that is perpendicular to the point and an opposite end of the wire is 30 mm or less.   
     
     
         6 . The method of  claim 4 , wherein
 a heating temperature in the heating of the wire is 200° C. or less, and a cooling temperature in the cooling of the wire is 40° C. or less.   
     
     
         7 . The method of  claim 6 , wherein
 the heating temperature, a heating time, and the tension applied to the wire during the heating of the wire satisfy condition A below,   
       condition (A): T+13.67 In(t)+2.7 τ≥425 (In condition (A), T is an absolute temperature K of the heating temperature, t denotes the heating time s, and τ is the tension (kgf) applied to the wire).