A method produces an inner spiral grooved tube using a first drawing die, a second drawing die, and a revolving flyer. The method includes two twisting-drawing steps. The first twisting-drawing step forms an intermediate twisted tube by reducing the diameter of a linear grooved tube, which has plural straight grooves formed along the longitudinal direction on its inner surface, by passing the linear grooved tube through the first drawing die and then by revolving the liner grooved tube wrapped around the revolving flyer with the revolving flyer, in conjunction with imparting twist to the linear grooved tube. The second twisting-drawing step forms the inner spiral grooved tube by reducing the diameter of the intermediate twisted tube by passing the intermediate twisted tube, which revolves with the revolving flyer, through the second drawing die in conjunction with imparting twist to the intermediate twisted tube.

Provided is a wiredrawn product drawn from a heat-treated steel containing: 0.38 to 1.05% by mass of C; 0.0 to 1.0% by mass of Mn; 0.0 to 0.50% by mass of Cr; and 0.0 to 1.5% by mass of Si, with the remainder being Fe and unavoidable impurities, wherein a GOS value/average crystal grain size is greater than or equal to ?0.6?GAM value+1.5 at a grain boundary setting angle of 2? and a step number of 0.07 ?m.

The ultra-fine wire fabricating apparatus comprises a feeder assembly, a stationary die, and a rotary die holder. The feeder assembly supplies a wire. The stationary die comprises a hollow inclined channel configured on an inner surface of the stationary die. The hollow inclined channel is configured to receive the wire from the feeder assembly. The rotary die holder configured to receive the wire from the stationary die and simultaneously torsionally deform the wire, wherein the rotary die holder rotates relative to the stationary die to produce the ultra-fine wire with improved mechanical properties. The method ensures continuous grain refinement of wires. The wires are severe plastic deformed using the combined effects of the stationary die and rotary die holder. The mechanical properties of the raw materials are improved due to a grain refinement and microstructure evolution caused by plastic deformation.

The ultra-fine wire fabricating apparatus comprises a feeder assembly, a stationary die, and a rotary die holder. The feeder assembly supplies a wire. The stationary die comprises a hollow inclined channel configured on an inner surface of the stationary die. The hollow inclined channel is configured to receive the wire from the feeder assembly. The rotary die holder configured to receive the wire from the stationary die and simultaneously torsionally deform the wire, wherein the rotary die holder rotates relative to the stationary die to produce the ultra-fine wire with improved mechanical properties. The method ensures continuous grain refinement of wires. The wires are severe plastic deformed using the combined effects of the stationary die and rotary die holder. The mechanical properties of the raw materials are improved due to a grain refinement and microstructure evolution caused by plastic deformation.

A method produces an inner spiral grooved tube using a first drawing die, a second drawing die, and a revolving flyer. The method includes two twisting-drawing steps. The first twisting-drawing step forms an intermediate twisted tube by reducing the diameter of a linear grooved tube, which has plural straight grooves formed along the longitudinal direction on its inner surface, by passing the linear grooved tube through the first drawing die and then by revolving the liner grooved tube wrapped around the revolving flyer with the revolving flyer, in conjunction with imparting twist to the linear grooved tube. The second twisting-drawing step forms the inner spiral grooved tube by reducing the diameter of the intermediate twisted tube by passing the intermediate twisted tube, which revolves with the revolving flyer, through the second drawing die in conjunction with imparting twist to the intermediate twisted tube.

A method produces an inner spiral grooved tube using a first drawing die, a second drawing die, and a revolving flyer. The method includes two twisting-drawing steps. The first twisting-drawing step forms an intermediate twisted tube by reducing the diameter of a linear grooved tube, which has plural straight grooves formed along the longitudinal direction on its inner surface, by passing the linear grooved tube through the first drawing die and then by revolving the liner grooved tube wrapped around the revolving flyer with the revolving flyer, in conjunction with imparting twist to the linear grooved tube. The second twisting-drawing step forms the inner spiral grooved tube by reducing the diameter of the intermediate twisted tube by passing the intermediate twisted tube, which revolves with the revolving flyer, through the second drawing die in conjunction with imparting twist to the intermediate twisted tube.

A wire drawing apparatus (10) is used in a final drawing process to ensure adequate initial performance of adhesion between brass-plated steel wire and rubber without a drop in productivity. At least one of the die (14z) disposed in the most downstream position, the die (14y) disposed in the second most downstream position, and the die (14x) disposed in the third most downstream position is a drawing die having a friction coefficient of 0.12 to 0.41 with the brass-plated steel wire. The other dies (14) are drawing dies each having a friction coefficient of 0.1 or below. By using these drawing dies, brass-plated steel wire (13) is drawn, and a noncrystalline portion of high lattice defect density is formed on the surface of the crystalline portion of the brass-plating layer of the brass-plated steel wire (13).

A wire drawing apparatus (10) is used in a final drawing process to ensure adequate initial performance of adhesion between brass-plated steel wire and rubber without a drop in productivity. At least one of the die (14z) disposed in the most downstream position, the die (14y) disposed in the second most downstream position, and the die (14x) disposed in the third most downstream position is a drawing die having a friction coefficient of 0.12 to 0.41 with the brass-plated steel wire. The other dies (14) are drawing dies each having a friction coefficient of 0.1 or below. By using these drawing dies, brass-plated steel wire (13) is drawn, and a noncrystalline portion of high lattice defect density is formed on the surface of the crystalline portion of the brass-plating layer of the brass-plated steel wire (13).

A method of producing an inner spiral grooved tube using a first drawing die using first and second drawing dice and a revolving flyer is provided. The method includes a first twisting-drawing step to form an intermediate twisted tube by reducing a diameter of a linear grooved tube, on an inner surface of which a plurality of straight grooves is formed along with a longitudinal direction, in conjunction with imparting twist to the linear grooved tube by passing the linear grooved tube through the first drawing die and then by revolving the liner grooved tube by wrapping the linear grooved tube around the revolving flyer; and a second twisting-drawing step to form an inner spiral grooved tube by reducing a diameter of the intermediate twisted tube by passing the intermediate twisted tube, which revolves with the revolving flyer, through the second drawing die in conjunction with imparting twist to the intermediate twisted tube.

The present invention relates to a steel cord for rubber reinforcement. In the steel cord of the present invention, cobalt is contained by 0.001 ppm to 0.1 ppm within a 4 nm top-surface of the brass-plated steel wire. A method of manufacturing the steel cord includes: providing a brass-plated steel wire; mixing a cobalt compound in a wet lubricant filled in a wet drawing bath provided with a plurality of drawing dies between one pair of multi-stage drawing cones such that the concentration of the cobalt compound becomes 0.1 ppm to 100 ppm; and causing the cobalt to be contained by 0.001 ppm to 0.1 ppm within a 4 nm top-surface of the brass-plated steel wire after the brass-plated steel wire passes through a final die by causing the cobalt to be attached to a surface of the brass-plated steel wire and alloyed with a brass layer while the brass-plated steel wire is passing through the drawing cones and the drawing dies to be subjected to multi-stage drawing.