A single-crystal diamond includes a pair of main surfaces facing each other, an impurity concentration being changed along a first direction in each of the main surfaces.

A diamond die includes a diamond provided with a hole for drawing a wire material, the diamond being a CVD single-crystal diamond, an axis of the hole being inclined relative to a normal direction of a crystal plane of the diamond.

A diamond die includes a diamond provided with a hole for drawing a wire material, the diamond being a CVD single-crystal diamond, an axis of the hole being inclined relative to a normal direction of a crystal plane of the diamond.

Embodiments of the invention relate to polycrystalline diamond (PCD) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, PCD includes a plurality of diamond grains defining a plurality of interstitial regions. A metal-solvent catalyst occupies at least a portion of the plurality of interstitial regions. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit a coercivity of about 115 Oersteds (Oe) or more and a specific magnetic saturation of about 15 Gauss.Math.cm.sup.3/grams (G.Math.cm.sup.3/g) or less. Other embodiments are directed to polycrystalline diamond compacts (PDCs) employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

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.

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.

A composite sintered body includes a first phase and a second phase. The first phase is a diamond phase, and the second phase is a phase formed of one or more types of elements or compounds or both thereof and applying strain to the first phase. A contained amount of the second phase is larger than 0 ppm and not larger than 1000 ppm. As a result, there is provided a high wear-resistant, high local wear-resistant, and high chipping-resistant diamond-containing composite sintered body.

Embodiments of the invention relate to polycrystalline diamond (PCD) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, PCD includes a plurality of diamond grains defining a plurality of interstitial regions. A metal-solvent catalyst occupies at least a portion of the plurality of interstitial regions. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit a coercivity of about 115 Oersteds (Oe) or more and a specific magnetic saturation of about 15 Gauss.Math.cm.sup.3/grams (G.Math.cm.sup.3/g) or less. Other embodiments are directed to polycrystalline diamond compacts (PDCs) employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

There is provided an irregularly-shaped diamond die for producing an irregularly-shaped wire, wherein a processing hole is provided, the processing hole having a reduction portion and a bearing portion in this order from an upstream side in a wire drawing direction, a corner portion having a curved shape and a non-corner portion located at a position different from a position of the corner portion are provided in a cross section of the bearing portion perpendicular to the wire drawing direction, and a surface roughness of the corner portion is greater than a surface roughness of the non-corner portion. The surface roughness Sa of the corner portion is equal to or less than 0.30 m and the surface roughness Sa of the non-corner portion is equal to or less than 0.20 m.

There is provided an irregularly-shaped diamond die for producing an irregularly-shaped wire, wherein a processing hole is provided, the processing hole having a reduction portion and a bearing portion in this order from an upstream side in a wire drawing direction, a corner portion having a curved shape and a non-corner portion located at a position different from a position of the corner portion are provided in a cross section of the bearing portion perpendicular to the wire drawing direction, and a surface roughness of the corner portion is greater than a surface roughness of the non-corner portion. The surface roughness Sa of the corner portion is equal to or less than 0.30 m and the surface roughness Sa of the non-corner portion is equal to or less than 0.20 m.