Steel cord for reinforcing rubber article, method for manufacturing same, and tire
Provided is a multi-twisted steel cord for reinforcing a rubber article, the steel cord having cord strength with a small loss as compared to the total strength of filaments constituting the cord and a high rubber penetration. The steel cord includes a plurality of twisted strands in a multi-twisted structure, each strand including a plurality of twisted filaments in two or more layers, in which at least some of the filaments have a tensile strength of 3,000 MPa or more, the steel cord satisfying a filament occupancy of 48% or more and less than 54%, a cord twist angle of 78° or more and less than 84°, an average crossing angle between adjacent filaments other than wrapping filaments of less than 17°, and a gap between adjacent sheath filaments constituting the strand of 0.065 mm or more.
1. A steel cord for reinforcing a rubber article, comprising
a plurality of twisted strands in a multi-twisted structure, each strand comprising a plurality of twisted filaments in two or more layers, wherein at least some of the filaments have a tensile strength of 3,000 MPa or more;
wherein the steel cord satisfies the following:
a filament occupancy of 48% or more and less than 54%;
a cord twist angle of 78° or more and less than 84° ;
an average crossing angle between adjacent filaments other than wrapping filaments of less than 17° ; and
a gap between adjacent sheath filaments constituting the strand of 0.065 mm or more.
2. The steel cord for reinforcing a rubber article according to claim 1 , wherein the average crossing angle between the adjacent filaments is less than 14°.
3. The steel cord for reinforcing a rubber article according to claim 2 , wherein the multi-twisted structure is a 1+n (n=6 or 7) structure comprising one core strand and six to seven sheath strands twisted around the core strand.
4. The steel cord for reinforcing a rubber article according to claim 3 , wherein a twist direction of the sheath filaments of the core strand is opposite to a twist direction of the sheath filaments of the sheath strands.
5. The steel cord for reinforcing a rubber article according to claim 3 , wherein a twist direction of sheath filaments of one of the sheath strands is opposite to a twist direction of sheath filaments of another sheath strand adjacent thereto.
6. The steel cord for reinforcing a rubber article according to claim 3 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
7. The steel cord for reinforcing a rubber article according to claim 2 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
8. A tire using the steel cord for reinforcing a rubber article according to claim 2 for reinforcement thereof.
9. The steel cord for reinforcing a rubber article according to claim 1 , wherein the multi-twisted structure is a 1+n (n=6 or 7) structure comprising one core strand and six to seven sheath strands twisted around the core strand.
10. The steel cord for reinforcing a rubber article according to claim 9 , wherein a twist direction of the sheath filaments of the core strand is opposite to a twist direction of the sheath filaments of the sheath strands.
11. The steel cord for reinforcing a rubber article according to claim 10 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
12. The steel cord for reinforcing a rubber article according to claim 9 , wherein a twist direction of sheath filaments of one of the sheath strands is opposite to a twist direction of sheath filaments of another sheath strand adjacent thereto.
13. The steel cord for reinforcing a rubber article according to claim 12 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
14. The steel cord for reinforcing a rubber article according to claim 9 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
15. A tire using the steel cord for reinforcing a rubber article according to claim 9 for reinforcement thereof.
16. The steel cord for reinforcing a rubber article according to claim 1 , wherein a lamellar orientation angle in a surface layer portion of at least some of the filaments is 0.0° or more and 6.0° or less, or 12.5° or more and 18.5° or less.
17. A tire using the steel cord for reinforcing a rubber article according to claim 1 for reinforcement thereof.
18. A method for manufacturing a steel cord for reinforcing a rubber article, wherein the steel cord is the steel cord for reinforcing a rubber article according to claim 1 , comprising a plurality of twisted strands in a multi-twisted structure, each strand comprising a plurality of twisted filaments in two or more layers;
the method comprising subjecting at least some of the filaments constituting the strand after a final wire drawing process to a stress relief annealing process at 250° C. or higher and lower than 300° C.
19. The method for manufacturing a steel cord for reinforcing a rubber article according to claim 18 , wherein the stress relief annealing process is performed after the final wire drawing process without a leveling process.