| 摘要 |
PURPOSE:To obtain ferromagnetic iron powder having high saturation magnetization, a high specific surface area, moreover having no surface contamination by treating the iron powder particles after dry type reduction with inert gas containing steam followed by oxidation-stabilization of the particle surfaces using a gas containing oxygen. CONSTITUTION:The particles mainly composed of iron are obtainable by dry type reduction of iron oxide hydrate, or iron oxide containing additives such as cobalt and nickel as occasion demands, while it is especially desirable to use the particles mainly composed of iron obtained by a method, wherein surface treatment with a sintering preventive agent is given to alpha-oxygen hydroxide followed by dehydration and firing for being made secondary iron oxide as well as by dry type reduction using hydrogen gas. A treatment temperature using inert ga containing steam is desirably 0 deg.C-200 deg.C. When exceeding 200 deg.C, saturation magnetization of the ferromagnetic iron powder to be obtained is lowered, a rectangular ratio of a magnetic tape to be obtained and SFD are worsened so as to be not desirable. Next, the obtained particles are given surface oxidation in a mixed gas atmosphere containing oxygen for giving a corrosion resistance and weather-proofness. A component excepting oxygen in this mixed gas is desirable inert gas such as nitrogen gas. |
