Patent ID: 11946119
Assignee: JFE STEEL CORPORATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B  Y | IPC B  C

Claim 2:
3. A method for producing a powder mixture for powder metallurgy, the method comprising:
mixing a raw material powder, a copper powder, and a binder at a temperature higher than or equal to a melting point of the binder, to obtain a first powder mixture;
mixing the first powder mixture and a graphite powder having an average particle size of less than 5 μm at a temperature higher than or equal to the melting point of the binder, to obtain a second powder mixture; and
mixing the second powder mixture and carbon black at a temperature lower than or equal to the melting point of the binder, to obtain a powder mixture for powder metallurgy,
wherein the binder is one or more resins selected from the group consisting of copolyamide and polyurethane,
the raw material powder contains an iron-based powder in an amount of 90 mass % or more with respect to the raw material powder,
a ratio [mb/(mr+mg+mCu+mc)×100] of a mass mb of the binder to a sum of a mass mr of the raw material powder, a mass mg of the graphite powder, a mass mCu of the copper powder, and a mass mc of the carbon black is 0.3 mass % to 0.80 mass %,
a ratio [mg/(mr+mg+mCu+mc)×100] of the mass mg of the graphite powder to the sum of the mass mr of the raw material powder, the mass mg of the graphite powder, the mass mCu of the copper powder, and the mass mc of the carbon black is 0.6 mass % to 1.0 mass %,
a ratio [mCu/(mr+mg+mCu+mc)×100] of the mass mCu of the copper powder to the sum of the mass mr of the raw material powder, the mass mg of the graphite powder, the mass mCu of the copper powder, and the mass mc of the carbon black is 0.1 mass % to 3.0 mass %,
a ratio [mc/(mr+mg+mCu+mc)×100] of the mass mc of the carbon black to the sum of the mass mr of the raw material powder, the mass mg of the graphite powder, the mass mCu of the copper powder, and the mass mc of the carbon black is 0.01 mass % to 0.30 mass %,
a surface of the raw material powder is coated with at least part of the binder, and
a surface of the binder is coated with at least part of the graphite powder, at least part of the copper powder, and at least part of the carbon black.