A rock drill insert made of cemented carbide having hard constituents of tungsten carbide (WC) in a binder phase including Co, wherein the cemented carbide includes 4-18 mass % Co and a balance of WC and unavoidable impurities. The cemented carbide also includes Cr in such an amount that the mass ratio Cr/Co is within the range of 0.04-0.19, and the difference between the hardness at a 0.3 mm depth at any point of the surface of the rock drill insert and the hardness of the bulk of the rock drill insert is at least 40 HV3.

The present invention provides a silver paste, containing at least a silver powder, a binder resin, and an organic solvent, in which a content of the silver powder based on the silver paste is 80.00 to 97.00% by mass, D10 is 1.00 to 3.00 μm and D50 is 3.00 to 7.00 μm, where D10 and D50 respectively represent a 10% value and a 50% value of a volume-based cumulative fraction obtained by laser diffraction particle size distribution measurement of the silver powder, the silver powder has a specific surface area of 0.10 to 0.30 m.sup.2/g, the silver powder has a copper content of 10 to 5000 ppm by mass, a content of the binder resin based on the silver powder is 0.430 to 0.750% by mass, and the silver paste has a dry film density of 7.50 g/cm.sup.3 or more.

The present invention provides a silver paste, containing at least a silver powder, a binder resin, and an organic solvent, in which a content of the silver powder based on the silver paste is 80.00 to 97.00% by mass, D10 is 1.00 to 3.00 μm and D50 is 3.00 to 7.00 μm, where D10 and D50 respectively represent a 10% value and a 50% value of a volume-based cumulative fraction obtained by laser diffraction particle size distribution measurement of the silver powder, the silver powder has a specific surface area of 0.10 to 0.30 m.sup.2/g, the silver powder has a copper content of 10 to 5000 ppm by mass, a content of the binder resin based on the silver powder is 0.430 to 0.750% by mass, and the silver paste has a dry film density of 7.50 g/cm.sup.3 or more.

The present invention provides a silver paste containing at least a silver powder, a binder resin, and an organic solvent, in which a value C.sub.BND/S.sub.BET is 2.0 to 3.4 where S.sub.BET (m.sup.2/g) represents a specific surface area of the silver powder, and C.sub.BND (% by mass) represents a content percentage of the binder resin based on the silver powder, a copper content of the silver powder is 10 to 5000 ppm by mass, and the silver paste has a dry film density of 7.50 g/cm.sup.3 or more. The present invention can provide a silver paste containing a powder in a high concentration and excellent in printability, and accordingly provide a silver conductor film that has a high filling factor and a high film density, exhibits high electrical conductivity, and is excellent in migration resistance.

The present invention provides a silver paste containing at least a silver powder, a binder resin, and an organic solvent, in which a value C.sub.BND/S.sub.BET is 2.0 to 3.4 where S.sub.BET (m.sup.2/g) represents a specific surface area of the silver powder, and C.sub.BND (% by mass) represents a content percentage of the binder resin based on the silver powder, a copper content of the silver powder is 10 to 5000 ppm by mass, and the silver paste has a dry film density of 7.50 g/cm.sup.3 or more. The present invention can provide a silver paste containing a powder in a high concentration and excellent in printability, and accordingly provide a silver conductor film that has a high filling factor and a high film density, exhibits high electrical conductivity, and is excellent in migration resistance.

A samarium-iron-nitrogen-based magnetic material containing Sm, Fe, N, Ti, and Co at a content of 2.5 at % or less. A content of the Sm may be 7 at % to 10 at %, a content of the Fe may be 65 at % to 80 at %, a content of the N may be 13 at % to 16 at %, and a content of the Ti may be 0.5 at % to 1.5 at %.

A samarium-iron-nitrogen-based magnetic material containing Sm, Fe, N, Ti, and Co at a content of 2.5 at % or less. A content of the Sm may be 7 at % to 10 at %, a content of the Fe may be 65 at % to 80 at %, a content of the N may be 13 at % to 16 at %, and a content of the Ti may be 0.5 at % to 1.5 at %.

To provide a magnetic core having a high permeability and a high voltage resistance while having a small variation in the voltage resistance.

The magnetic core includes the magnetic powder. A total area ratio of particles of the magnetic powder in a cross section of the magnetic core is 75% or more and 90% or less. An average circularity of large size particles is 0.70 or more when the large size particles are particles extracted from the particles of the magnetic powder in the cross section of the magnetic core in the order of size from the largest size until a cumulative area ratio of the extracted particles reaches a smallest area ratio exceeding 20% of the total area ratio of the particles of the magnetic powder.

To provide a magnetic core having a high permeability and a high voltage resistance while having a small variation in the voltage resistance.

The magnetic core includes the magnetic powder. A total area ratio of particles of the magnetic powder in a cross section of the magnetic core is 75% or more and 90% or less. An average circularity of large size particles is 0.70 or more when the large size particles are particles extracted from the particles of the magnetic powder in the cross section of the magnetic core in the order of size from the largest size until a cumulative area ratio of the extracted particles reaches a smallest area ratio exceeding 20% of the total area ratio of the particles of the magnetic powder.

A method for manufacturing a magnetic powder includes a step of producing a magnetic powder by spray-drying a spray liquid containing first magnetic particles, second magnetic particles, a thermosetting resin, and an organic solvent. A magnetic powder includes first magnetic particles and a thermosetting resin coating film on surfaces of the first magnetic particles. The first magnetic particles are soft magnetic metal particles. The resin coating film contains second magnetic particles. The second magnetic particles have a smaller average particle size than the first magnetic particles.