IRON POWDER HAVING HIGH COMPRESSIBILITY FOR HIGH STRENGTH POWDER METALLURGY PRODUCT AND PREPARATION THEREOF

摘要

PURPOSE:To prepare an iron powder for a powder metallurgy product excellent in sinterability and sinter tensile strength without losing compressibility by a method wherein a relatively small amount of a reduced iron powder is mixed in an unfinished reduced water atomized iron powder and the resulting mixture is reduced and crushed. CONSTITUTION:A mixture consisting of 70-95% unfinished reduced water atomized iron powder whose particle size ratio of 100 mesh or less is 90wt% or more and the remainder reduced iron powder whose particle size ratio of 325 mesh or less is 70% or more is subjected to finish reduction in a temp. range of 850-1,050 deg.C under a reducing atmosphere with a dew point 0-15 deg.C and the obtained finished reduced cake is crushed to obtain a desired iron product whose powder ratio of 100 mesh or less is 80% or more. In the above described method, a compounding ratio of the reduced iron fine powder is reduced to prevent the lowering of compressibility and the deterioration of moldability. In addition, the atmosphere of finish reduction is pref. a H2 gas or an ammonia decomposed gas.