Makoto Kassai

Semihard Magnetic Alloys of Co–Fe–Nb System

Ductile alloys of the Co–Fe–Nb system in the vicinity of 90% Co were studied for reed switch applications. Wires have been investigated which have high values of coercive force, squareness ratio and remanence as well as high stability of these magnetic properties against heating. As a result of this research, an 85 Co–12Fe–3Nb wire, 0.5 mm in diam., subjected to a sequence of a 1100°C intermediate anneal, 90% cold reduction and 750°C aging is deemed best for this application. This wire shows a coercive force of 20 Oe, a squareness ratio of 0.95 and a remanence of 15 000 G. Intermetallic Co–Nb compounds precipitate during aging treatment. This phenomenon causes the coercive force to increase. The cold drawing facilitates the precipitation. The intermediate anneal temperature should be sufficiently high to realize a complete solid solution in the wire. The drawn wire has 〈111〉 fiber texture. Since 〈111〉 is an easy magnetization direction, the wire shows a good rectangular hysteresis loop along the axis. Thi...

Magnetic Properties of Co–Fe–Nb Alloys for Remanent Reed Switches

Previous studies revealed that an 85Co–12Fe–3Nb wire for a remanent reed switch showed a coercive force of 20 Oe. The magnetic properties of Co–Fe–Nb alloys containing 6∼18 wt % Fe , O ∼7 wt % Nb , and the balance Co, were further investigated. Wires were made by a serial process of solution treatment at 1200°C, cold drawing and aging at 700°C for 1 hour. The value of coercive force increases linearly with Nb content, and reaches 48 Oe at 7 wt% Nb. The magnetic moment decreases linearly with Nb content from 172 to 132 emu/g. Changes in coercive force and magnetic moment with Fe content are not so large as those with Nb content. The magnetostriction constant, however, changes with Fe content and becomes nearly zero as Fe approaches 9 wt%. The squareness ratio (Br/B100) is higher than 0.90 for all the specimens except for the specimen with 7 wt% Nb. It was clarified by X‐ray diffractometer and electron microscope that the increase in coercive force with Nb is due to fine precipitates of Co 3 Nb in the grain.

Semihard Magnetic Alloys of Co[Single Bond]Fe[Single Bond]Ni[Single Bond]Nb System

Ductile alloys which have approximately equal amounts of Co and Fe, plus Ni and a small amount of Nb were investigated for remanent reed switch applications. As a result, 39Fe–38Co–20N–3Nb wire 0.6mm in diameter, made by intermediate annealing at 700°C, cold drawing to 92% reduction in area, and final annealing at 6007deg;C for 1 hour, showed a coercive force of 30 Oe, remanence of 16000 G, squareness ratio higher than 0.95, and thermal expansion coefficient of 98×10−7/°C between 30 and 400°C. This alloy could be cold‐worked easily after annealing. The phase was f.c.c. after annealing at a temperature over 800°C. However, cold working caused partial phase transformation of f.c.c. into b.c.c. This intermixing of f.c.c. and b.c.c. phases in a high coercive force state survived up to 700°C annealing. On the other hand, remanence was low in the cold drawn state, but increased by annealing over 600°C. The coercive force grew larger as the Nb content increased.

Magnetic Properties of Co[Single Bond]Fe[Single Bond]Nb Alloys for Remanent Reed Switches

Previous studies revealed that an 85Co–12Fe–3Nb wire for a remanent reed switch showed a coercive force of 20 Oe. The magnetic properties of Co–Fe–Nb alloys containing 6∼18 wt % Fe , O ∼7 wt % Nb , and the balance Co, were further investigated. Wires were made by a serial process of solution treatment at 1200°C, cold drawing and aging at 700°C for 1 hour. The value of coercive force increases linearly with Nb content, and reaches 48 Oe at 7 wt% Nb. The magnetic moment decreases linearly with Nb content from 172 to 132 emu/g. Changes in coercive force and magnetic moment with Fe content are not so large as those with Nb content. The magnetostriction constant, however, changes with Fe content and becomes nearly zero as Fe approaches 9 wt%. The squareness ratio (Br/B100) is higher than 0.90 for all the specimens except for the specimen with 7 wt% Nb. It was clarified by X‐ray diffractometer and electron microscope that the increase in coercive force with Nb is due to fine precipitates of Co 3 Nb in the grain.