About 50% of cobalt is an iron-cobalt alloy（Fe-co precision alloy） soft magnetic material. In order to improve the processing properties, it is usually added with 1.4 to 1.8% of vanadium (V), so it is also called iron cobalt vanadium soft magnetic alloy. It has a very high saturation magnetic flux density Bs (2.4T) and a Curie temperature (980 ~ 1100 ° C), so it is suitable for the production of aerospace appliances (micro-motors, electromagnets, etc.) that require light weight, small size, and high operating temperature. Relays, etc.). It also has a large saturation magnetostriction coefficient λs, which can be used to make magnetostrictive transducers.
Compared with iron-nickel alloy, it has poor processing performance, easy oxidation, low resistivity, high loss when high frequency, so it is not suitable to work at high frequency; and because of high cost, it is often used for high torque motor rotor and electromagnetic Iron pole, eardrum vibrating piece, power transformer, magnetostrictive transducer, etc. A soft magnetic alloy having a composition of 49% iron, 49% cobalt, and 2% vanadium can be processed into a very small toroidal core having an outer diameter of about 1 mm, and is used as a core of a rectangular loop for a relay.