PURPOSE: To obtain the above rare earth-iron magnet having high corrosion resistance by adjusting the atomic ratio of Co at 20% or more to the total amount of Fe and Co in all the metal phase except the main phase.
CONSTITUTION: This magnet is a sinter of alloy consisting mainly of Fe and Co and containing R (indicating a kind or more of rare earth elements containing Y) and B and has all the metal phase except the main phase e.g. R-rich phase and B-rich phase contain Co and this metal phase contain the atomic ratio of Co at 20% or more to the total amount Fe or Co. Generally, Co is higher than Fe in corrosion resistance and therefore inhibits corrosion of metal phases by making a metal phase which starts corrosion contain a large amount of Co. This process can improve corrosion resistance of the whole magnet.
SAKAI ISAO
SAHASHI MASASHI
