MANUFACTURE OF ACICULAR IRON ALLOY MAGNETIC GRAIN POWDER FOR MAGNETIC RECORDING

摘要

PURPOSE:To offer a manufacturing method industrially obtainable acicular iron alloy magnetic grain powder for magnetic recording having high coercive force and high saturation magnetization and small in crystallite size among grains and in each distribution width of coercive force. CONSTITUTION:The granulated material of acicular ferrous hydroxide grains or acicular hematite grains are charged into a fixed layer reducing apparatus into a fixed layer, and while a hydrogen gas contg. 2 to 100 g/Nm<3> steam is flowed in the above reducing apparatus, reduction is executed at <350 deg.C to obtain acicular magnetite grains small in the difference between the crystalline size of the acicular magnetite grains in the upper layer part of the above fixed layer and the crystalline size of the acicular magnetite grains in the lower layer part. Then, this acicular magnetite grains are reduced at 350 to 550 deg.C in a hydrogen gas flow to obtain acicular iron alloy magnetic grain powder small in the distribution width of the crystallite size among the grains.