STUDIES ON INDUSTRIALIZATION OF "MT" PERMANENT MAGNET (I)

On the Chemical Composition and Additional Elements

Abstract

Today, applications of permanent magnet are increasing in various fields of industries.The magnet of excellent quality such as Alnico, contains a great quantity of rare materials such as Ni and Co. During the World War II, research of permanent magnet was concentrated on the discovery of substitutional alloy which possessed high coercive force without containing any rare metals. MT magnet was developed in the authprs'laboratory. This magnet is Fe-Al-C ternary alloy and does not contain rare elements. It has magnetic properties nearly equal to a middle cobalt steel, and possesses comparatively high coercive force of about 200 Oersteds.
In this report, the result of basic experiments on optimum composition and effect of additional elements to MT magnet were described. First, the specimens of Fe-Al-C ternary alloys containing various different quantities of Al and C were prepared to detect their optimum composition. The experiment showed that these alloys presented. the most superior magnetic properties in the region of 8.0±0.2% Al, 2.0±0.1% C, and its residual induction became more than 6, 000 Gausses, coercive force more than 200 Oersteds and energy product more than 0.45×10⁶ Gauss-Oersteds. Moreover 13 kinds of metals including Si, Mn, Ni, Co, Cr, Sn, etc. were added to the basic ternary alloy, and their effects on the magnetic properties were investigated. Addition of small amount (0.5-2%) of Cu, Sn and Ni gave a good effect on magnetic properties. These elements, however, if added more than 3%, would come to unfavourable effect on the magnetic properties. It was appreciated from Fe-Al-C phase diagram of 1200°C section that the range of optimum composition lay approximately along a "tie line" in the γ field closed by γ+K or C field.